Supernovae - Stars that explode

-  2173  -   The best measurements to date put the age of the Universe to be 13.862 billion years.  These  measurements also allow calculations for the composition of the Universe to be 30% matter and 70% Dark energy.  Today’s expansion rate is 74.2 km/sec/mps, which equals  49,306 miles per hour per million lightyears. The coasting point from expansion’s deceleration to acceleration occurred 7 billion years go , half way back to the Big Bang.
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----------------------------  2173  -  Supernovae  -  Stars that explode
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-  Stars die and explode.  Our Sun will die in another 5,000,000,000 years.  It is just middle aged right now.  I will not be around for this explosion.  Our mother Earth will explode more gently as a planetary nebula.  The hot envelope of the nebula will expand all the way out to cover the planet Earth.  We’re toast. 
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-  If our star were 8 times more massive it would explode as a supernova then collapse into a neutron star instead of a planetary nebula.  If it were 10 to 20 times more massive the end of the supernova explosion would collapse into a blackhole.
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-  (October 13, 2018)  Astronomers found a neutron star “2012au” in the galaxy 4790 that was 77 million lightyears from Earth.  Astronomers measured the oxygen and sulfur atoms flying away from the star at 5,150,000 miles per hour.  These heavier atoms would trail behind the lighter element hydrogen atoms that leave the supernova explosion first forming an inner shell of ejected gas.
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-  (November 10, 2018)  Supernova “iPTF 14gqr”  occurred that was 930 million lightyears away.  The star was 8 times the mass of the sun.  It burned through its nuclear fuel that was keeping it from collapsing due to the compression of gravity.  Its core collapsed into a neutron star.  The explosion ejected an outer layer of gas as a bright flare lasting 20 days.  Its visible light lasted for 7 days. 
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-  Supernova explosions are spotted as gamma ray bursts approximately once a day from all directions in the sky.  These flashes of electromagnetic radiation  are 100,000,000,000,000,000,000 times more energy than our Sun but lasting only  few seconds.
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-  What likely happens with a gamma ray burst that is not a supernova is that it starts out more massive.  The stellar core collapses under its own gravity into a blackhole.  Jets of material shootout from the magnetic poles that collide with the expanding layers of gas.  The collisions of atoms cause the emission of high energy gamma rays. 
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-  A gamma ray is a high energy photon of light, higher energy than an X-ray.  Gamma rays would penetrate 10 feet of lead without being absorbed..  The wavelength of a gamma ray is the smallest in the electromagnetic spectrum. Its wavelengths start at 0.01 * 10^-9 meters and is even smaller with higher energy.  For comparison:  The color violet in visible light is 380* 10-9 meters.
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-  When the Sun dies it will leave behind a core of carbon and oxygen with a shell of helium.  This phase is called a White Dwarf star.   It has lost all of its hydrogen that has burned into helium.  There is no more energy to sustain it and it will continue to cool and fade away.
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-  The fate pf every star depends on its mass.
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-  Larger stars balloon into Red Giants, after all the hydrogen is burned their gravity force begins forming atom nuclei into heavier elements   The heavier elements become onion layers of carbon, oxygen, silicon, etc until the heaviest element iron is compressed into the core 
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-  Iron is too heavy to fuse any heavier elements, fusion stops.  The star collapses.  The electrons are driven into the nuclei of the iron atoms.  The electrons combine with the protons to form neutrons and neutrinos. 
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-  The neutrinos have little mass and escape the core immediately with a tremendous amount of energy. The temperature increases to 100 billion degrees.  The outward explosive pressure creates a shockwave traveling at 10% the speed of light.  The supernova explodes.  The core collapses into  neutron star, or into a blackhole, depending upon the amount of mass left behind.
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-  If the star starts out with a 25 solar mass, it can burn all of its hydrogen in a short time, about 7 million years.  The temperature can reach 40 million degrees.  The compression of gravity increases the temperature to 200 million degrees using helium fusion for another 500,000 years.  Then, carbon fusion takes over and the temperature is 600 million degrees lasting for only 600 years. 
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-  Neon fusion at 1200 million degrees lasts for only one year.  Oxygen fusion at 1500 million degrees lasts for only 6 months.  Silicon fusion at 2700 million degrees lasts for  single day.  Then, in 2 seconds the core collapses when it reaches 5400 million degrees.
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-  The core bounces and expands in 1 millisecond.  The star explodes into a supernova reaching a temperature of 23,000 million degrees.  The supernova explosion lasts for 10 seconds. 
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-  Over the supernova’s lifetime it expels 80% of its mass back into space.  This shock wave is called a stellar wind that spreads the heavier elements out into the universe.  Somehow these heavier elements condense back into planets and into people that are reading this.
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- An example of a supernova that completed this process is the Gum Nebula in the constellation Vela.  It exploded as a supernova 11,000 years ago and is now has a diameter spreading out 2,300 light years.  It spans 60 arc degrees across the sky.  And , it is only 300 lightyears away from Earth. 
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-  The Crab nebula in the constellation Taurus the Bull, known as Messier, M1, is 6,000 lightyears from Earth.  It was even visible from Earth with the naked eye in 1054 A.D.  The event was recorded in American Indian and in Chinese history.  These must have been our first astronomers.
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- The Crab Nebula is 230 arc seconds across and 5,872 lightyears away. 
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--------------- Arc Seconds  =  206,265  * diameter  /  distance
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-------------   Diameter  =  230  *  1800  /  206,265
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--------------  Diameter  =   parsecs  *  3.262  lightyears /  parsec =  6.55  lightyears.
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-  The Crab Nebula is expanding at 1,400 kilometers / second.  The radius is 3.2736  lightyears.
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-------------------  Time  = Distance  /  Velocity
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-------------------  Time  =  3.2736  LY  / 1400 km  /  sec.  *  9.461  *  10^12  km  /  LY  =  2.2   *  10^10 sec  /  3.16  sec  /  year  =  700 years.
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--------------------  700 years 
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-------------------  This  calculation puts the event at 303  A.D.  The actual date was 1054 A.D.  My oversimplified calculation was only accurate to within 24%.  Not bad for an amateur astronomer.
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-  These supernova were classified as Type II supernova because hydrogen is present in their spectrum and the core collapse was the cause of their explosion.
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-  There is another type of supernova called a Type I where there is no absorption lines or emission lines present in  the spectrum for hydrogen.  These special supernova are created in binary stars.  The heavier of the two orbiting stars will convert hydrogen to helium more rapidly.  It runs out of fuel more rapidly and becomes a Red Giant star dumping its outer layers onto its companion star.
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-  The Red Giant eventual ejects its outer layers and becomes a White Dwarf star consisting mostly of carbon and oxygen.  The second star eventually catches up to the first star and evolves into a Red Giant too.  It begins dumping its outer layers into the White Dwarf star.
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-   When the White Dwarf  star reaches the critical mass of 1.4 Solar Mass its temperature climbs to 4 billion degrees igniting the carbon and detonating the star becoming a Type I supernova.  The second Red Giant star gets flung out into space as action must equals reaction as Kepler taught us.
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-  The 1.4 Solar Mass limit is called the Chandrasekhar limit.  Sugrhmanyan Chandrasekhar was an India- American astronomer born 1910 in India. He graduated Cambridge University in 1933.  He received the Noble Prize for the theoretical calculation that determined if a star was more massive than 1.4 Solar Mass it would explode as a supernova. 
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-  Subatomic particles have a finite volume of their own and can only be compressed a certain amount.  Chandrasekhar calculated that this limit would be 1.4 Solar Mass.
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-  Because Type I supernovae at 1.4 Solar Mass have the same tremendous runaway configuration each time,  their brightness should be the same each time.  By comparing this absolute brightness to the apparent brightness from Earth astronomers can calculate how far the supernova is from us.  Astronomers call this their “standard candle” when the absolute magnitude of brightness is known. 
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-  When astronomers measured hundreds of these Type 1 supernova they calculated that their luminosity was10% to 20% fainter than they should be at their “known” distances.  If they were further away that meant that the universe is expanding faster than expected.  Even today astronomers can not explain what forces are accelerating the expansion of the Universe.  So, we simply call the unknown force Dark Energy.
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-  If you know the brightness of a star you can calculate the distance the star is away from us.  A potential error in measuring this brightness is the effect of interstellar dust dimming the light before it reaches us.  Interstellar dust is very fine submicroscopic haze made up mostly of carbon and silicon.  The size of the dust is such is that it absorbs or scatters blue light more than it does red light. 
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-  This is the same reason why the sky is blue and the sunset is red.  If we take a spectrum of the light from the supernova , and , the blue light and red light have the same intensity and the same decaying light spectrum, then, the dust absorption can be ruled out as a possible factor for dimness.
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-  If we start with a Type 1 supernova  in a nearby galaxy were we already know the distance using other means of calculation , then, the Type 1 supernova that is more distant will appear dimmer by the inverse square law of the distance.
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-  To understand this think of a light source emitting from a point source into a sphere.  One meter from the light source shines on a rectangular area one meter on a side, i.e. 1 square meter.  Two meters from the light source expands to 2 meters on a side , 4 square meters,  3 meters to 9 square meters, etc.  As the distance increases the same light is spread over a greater area which is equal to the square of the distance and the light is dimmer by that amount.  A supernova 3 times the distance away will be 9 times as dim.
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-  The Universe today is expanding at 70 kilometers per second per mega parsec distance.  A mega parsec is 3,262,000 lightyears distance.  If we measure the redshift of the light coming from the supernova we can calculate the distance the light has traveled to reach us. 
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-  As the galaxy is moving away from us its wavelength of light becomes longer, stretched toward the red end of the light spectrum 
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-------------------  Redshift  =  change in wavelength  /  wavelength emitted
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------------------  Redshift  =  z
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---------------  Velocity of the galaxy  /  Velocity of light  =  (z^2  +  2z)  / ( z^2  +  2z  +2)
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 -  A redshift of 1  means the receding velocity of the galaxy is 60% that of the speed of light.  This is not your common sense velocity.  It rather is a measurement of  the expansion of space that has taken place while the light from the galaxy is on its way to us. 
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-  However, if we measure the same distance to the galaxy using its luminosity we find that the supernova is actually 5% dimmer than expected.  Because the light is dimmer the galaxy must be further away.  Therefore, the Universe must not be expanding at a “constant” 70 km/sec/mps.  It must be accelerating even faster than that.  This measured acceleration occurs up to 5 billion lightyears away. 
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-  When you see through a telescope the further distant you look the further back in time you see.  Back 5 billion years we see us accelerating faster and faster.  When we observe supernova that is more than 7 billion lightyears distant it appears 25% brighter than expected.  It appears brighter because the Universe is decelerating its expansion at that point in our cosmic history.   The supernova is closer than expected.
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-  The coasting point that marks the transition from decelerating due to gravity and accelerating due to Dark Energy occurs at  the redshift of   z  =  0.7.  Using the formula above this corresponds to a receding velocity of 49% the speed of light.  49% of 299,800 km / sec / mps  is 195,600 km / sec / mps.  If the velocity were a constant the distance would be 200 km per mega parsec.
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-   Each mega parsec is 3.262million lightyear.  The distance is 7 billion lightyears back to half the age of the Universe.
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-  Over 200 supernova explosions have been measured in this way.  The best measurements to date put the age of the Universe to be 13.862 billion years.  These  measurements allow the calculation for the composition of the Universe to be 30% matter and 70% Dark energy.
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-  Today’s expansion rate is 74.2 km/sec/mps  =  49,306 miles per hour per million lightyears. The coasting point from deceleration to acceleration occurred 7 billion years go , half way back to the Big bang.
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-  Supernova erupt every 100 years in a galaxy the size of our Milky Way Galaxy.  The last supernova seen with the naked eye occurred in 1987.  It was in our southern neighbor galaxy, the Large Magellanic Cloud.
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-  If galaxies were the size of a dinner plate the Observable Universe would be 20 miles in every direction.  If we knew which way to look we would see a supernova explosion every day. 
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-    November 19, 2018          5  ,  54,  504     2171     2173
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 --------------------------   Friday, February 28, 2020  --------------------------
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SUPERNOVA - 2 explosions being studied?

-  2636  -  SUPERNOVA   -  2 explosions being studied?  Astronomers have detected the fallout of the biggest known explosion in the universe since it was born more than 13 billion years ago.  The blast came from a supermassive black hole in the Ophiuchus galaxy cluster, located nearly 400 million light years from Earth.
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---------------------   2636  -  SUPERNOVA   -  2 explosions being studied?
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-  Stars explode.  Our Sun is a star.  It will explode.  Our Sun is a smaller star and its explosion is not so massive.  The bigger the star the more massive the explosion.

-  This explosion in Ophiuchus was five times more massive than the previous title-holder of the universe’s biggest outburst, which occurred in the galaxy cluster (MS 0735+74). But unlike the Big Bang, a near-instantaneous expansion from which the universe originated, the Ophiuchus cluster explosion was a slow burn that raged for hundreds of millions of years.
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-  The eruption was caused by an “active galactic nucleus” (AGN), which is the term for the central region of a galaxy during energetic phases that are notable for their powerful flares and intense emissions of radiation. The supermassive black hole at the center of the Milky Way, for instance, is currently dormant, though it has been an AGN in the past.
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- The outburst blew out a colossal hole in the plasma surrounding the black hole, creating a “giant radio fossil” in the cluster. Scientists have observed this cavity for years, but they were puzzled about its origins due to its unprecedented scale.
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-   The cavity is a very aged fossil of the most powerful AGN outburst seen in any galaxy cluster.  Multi-wavelength observations were used from two space telescopes, NASA's Chandra X-ray Observatory and the European Space Agency's XMM-Newton, as well as two ground radio observatories, the Murchison Widefield Array in Australia and the Giant Metrewave Radio Telescope in India.
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-  In particular, the radio observations helped to reveal the odd features at Ophiuchus as the work of an AGN explosion. Over the coming decades, radio telescopes are expected to become much larger and more sensitive, so this may not be the last time the record for the biggest cosmic explosion is blasted away by a new discovery.
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-  Another giant burst, known as a Seyfert flare, lasted about 300,000 years and occurred relatively recently in cosmic terms. It was triggered by activity near the supermassive black hole at the center of the Milky Way, called Sagittarius A*, which is over four million times as massive as the Sun.
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-  Some 3.5 million years ago, the center of our galaxy experienced a cataclysmic explosion that blasted out radiation across hundreds of thousands of light years.  It is centered 200,000 light years from Earth.
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-  The event reveals that the Milky Way’s core is more dynamic and energetic than expected. It must have been a bit like a lighthouse beam.
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-  The exact origins of the flare are unknown, but it would have required a lot of gas to suddenly be dumped into the galactic nucleus.   For instance, a giant molecular cloud may have gotten too close to Sagittarius A*, only to be consumed and spit out from both poles of the galaxy in this gigantic flare.
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-  The effects of the explosion create the Magellanic Stream, a massive river of gas and dust that orbits the Milky Way at a distance of 200,000 light years.  Despite how far away the stream is from the Milky Way’s core some parts of this gassy river were energized by the pyrotechnic event. Gas in the stream appears to be ionized, or stripped of electrons, signaling that the flare recently influenced it.
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-  It's likely that the flare was about as bright as could be expected for a supermassive black hole [of Sagittarius A*’s mass.  So if you were one of humanity’s early ancestors living at this time, what exactly would you see in the night sky?
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-   Most of the optical light from the blast would be absorbed by the dust and gas surrounding the galactic nucleus. The flare might have been comparable (say, one-tenth as bright or so) to the full Moon in brightness spread over a much larger area of the sky.
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-  However, if you could transport X-ray observatories back in time 3.5 million years, you would capture a much more dazzling glimpse of the flare’s brilliant jets. This is because about 10% of the flare’s total luminosity was emitted by high-energy X-rays which are much less likely to be blocked by gas and dust.
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-  The flare would be extremely bright to modern X-ray telescopes, unless there was a very large amount of gas lying along our line of sight to it.  We would still be able to see the effects of the flare as it ionized and heated the gas away from the plane, the fading remnants of which we still see today.
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- ----------------------------------------  Request other Reviews about our Sun, and here is a list about supernovae of other suns,(stars):
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-  455 - Supernovae - A Cosmos, Everything but Quiet.  It is violent out there.
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-  476 - Gamma Rays and Cosmic Rays
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-  504  -  Accelerating Universe from Unknown Force.
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-  508 - You Are Made of Star Dust 
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-  510 - Supernova You Can See
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-  613  -  From supernova to our Sun.Nuclear fusion will occur when a star’s central temperature reaches 10,000,000 degrees.  The collisions are so rapid at that temperature that all electrons are stripped away from their nucleus.  And, nuclei collide to such an extent as to overcome the repulsive electric force of their mutual positive charges.  The Strong force acts over a distance of only .0000000000001 centimeters (10^-13), the width of an atom, but, it completely overpowers the electromagnetic force and the nuclei fuse together.  When two protons fuse they form the nucleus of deuterium, but the mass is about 1% less than the combined mass of the two protons.  This amount of mass is converted into energy according to E = mc^2 and in the form of a positron (a positive or anti-electron) and an anti-neutrino.
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-  831  -  Supernova 1987A. We first saw Supernova 1987A in the Large Magellanic Cloud  over 20 years ago.  That is the astronomers in the southern hemisphere saw it with the naked eye, beginning February 23, 1987.  It is below the southern horizon for us.  The Large and Small Magellan Clouds look like glowing clouds but both are irregular galaxies.    Maybe they are part of our Local Group of galaxies, but recent evidence is that they are just passing by.  The Large Magellan Cloud is 1/20th the size of the Milky Way Galaxy and has 1/10th as many stars.  One of these stars blew up and 20 years later it is still giving astronomers new information about supernovae.
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-  929  -  The youngest supernova.   A supernova normally goes off in a galaxy every 50 to 100 years.  However, we have not seen one in several hundred years.  It could be that they are going off and they are out of sight.  The last one astronomers had recorded for the Milky Way  is Cassiopeia A. It went supernova 330 years ago, that would be in 1678.  Today the remnant of that explosion has an expanding shockwave that is 10 lightyears in diameter.  The shockwave has an average velocity of 20,300,000 miles per hour
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-  984  -  The art of astronomy. Today you are seeing many amazing images of astronomical objects in newspapers, magazines, and TV.  These images are called “false color images” and they are coming from new types of cameras in space and around the world.  They are the new “art of astronomy
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-  1308  -  Supernova  is a star that exploded 400 years ago.  The star was first seen in 1572 in the Constellation Cassiopeia.  Cassiopeia is the upside down , lazy “w” you see in the night sky on the opposite side of the North Star from the Big Dipper.  It is called Tycho’s Supernova because the Danish astronomer Tycho Brahe published a book about his observations of the “new star” in 1573.  The supernova appeared in early November, 1972.  There have been 8 naked eye discoveries of supernovae in recorded history.
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-  1319  -   RCW-86 Supernova is one of about 8 supernovae explosions witnessed by the naked eye in recorded history.  The Chinese recorded this one in the year 185 A.D.  They called it the “Guest Star” and it remained in the night sky for 8 months.
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-  1320  -     When Supernova Sn1006 first explode in the year 1006 it was brighter than the planet Venus in the night sky.  It was even visible during the day for several weeks after the explosion even though it was 7,000 lightyears away.
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-  1411  -  The brightness also depends on the proportion of metals in the star.  Space is full of explosions and we are just getting the technology that allows us to begin seeing them.  This picture is of a supernova remnant is the debris left after a star exploded some 400 years ago.  After much study it was decided that this is a beautiful example of two White Dwarf stars in a binary system that went supernova.  One exploded obliterating the other.  It is called a type 1a supernova when one star steals mass from another and reaches that 1.4 Solar Mass threshold that collapses atoms into the nuclei.  The rebound is a supernova explosion.
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-  1566  -  Supernovae are what we are made of.  Gamma Ray bursts occur about once a day in the Observable Universe. When Supernova Sn1006 first explode in the year 1006 it was brighter than the planet Venus in the night sky.  It was even visible during the day for several weeks after the explosion even though it was 7,000 lightyears away.
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-  1684  -  What does a supernova explosion sound like?   In space there is no sound.  However, technology can detect electromagnetic radiation and translate it to the frequencies we can hear.  What can we learn from this?
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-  1698  -  How rare are we in the Universe?  We are made of elements created in exploding stars.  Our world has such abundance but how rare is this abundance in the Universe?   For every 1 million miles of space galaxies are receding each other by 47,000 miles per hour.
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-  1699  -  Betelgeuse is 640 lightyears away.  It is a 20 Solar Mass Red Supergiant star that could go supernova tomorrow.
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-  1881  -  Supernovae are like snowflakes.  No two are alike.  Yet, we try to use a special type of supernovae explosion as a “standard candle“, a known brightness that can be used to calculate distance.  However, supernovae, in general, can be 100 times brighter and 100 times dimmer than the average supernovae explosion.
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-  2149  -  Supernovae from blue super giant stars.
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-  2173  -   How supernovae explode.
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-  2299  -  You are made of stardust.   A Supernova is a sun, a star, that explodes because it becomes unstable after it exhaust all of its nuclear fuel.  Our Sun will not become a Supernovae because it is not big enough.  A bigger star will have the gravity necessary to overcome the electromagnetic force between the electron and nucleus of atoms and when its fuel is gone it goes supernova.
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- 2300  -  Supernovae you can see. If you have read 2299 - “ You Were Made from Star Dust - Supernova”, you are probably anxious to learn more about Supernova.  It turns out that in the last 1000 years at least six, maybe eight supernova explosions have been seen by naked eye observers. 
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-  2345  -  Scientists estimate it takes 100,000,000 to 200,000,000 years for intelligent life to emerge and colonize a planet.  65,000,000 years ago, at the end of the Cretaceous-Tertiary (K-T) period, 50% of life on Earth was extinguished.  The dinosaurs did not survive.  But, some half of marine invertebrates, plankton, marine reptiles did survive.  65,000,000 years later here we are and you are reading about it.
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-  2426  -  LIFE  -  Exploding stars create life , and destroy life. Our galaxy is big and mostly empty space, but it harbors millions of blackholes that are remnants of supernovas and collapsing stars.  When a giant star burns all it’s fuel, no heat remains to create the pressure withstanding the compression of gravity.  The force of gravity collapses the stars mass into a singularity at the center of a blackhole.   These creators of life are every where. 
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-  February 27, 2020                                                                          2636                                                                                 
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-----  Comments appreciated and Pass it on to whomever is interested. ----
---   Some reviews are at:  --------------     http://jdetrick.blogspot.com ----- 
--  email feedback, corrections, request for copies or Index of all reviews
---  to:  ------    jamesdetrick@comcast.net  ------  “Jim Detrick”  -----------
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 ---------------------          Friday, February 28, 2020    --------------------
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PLATO - a dialogue for justice?

-  2635  - PLATO -  a dialogue for justice?   Socrates was the world’s greatest teacher, but he never wrote anything down.  And, he always answered a question with a question forcing the inquirer to think for himself.  Plato was his student and Aristotle was Plato’s student.  Aristotle’s student was Alexander the Great.
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-                                                                   Aristotle  -
---------------------   2635 - PLATO -  a dialogue for justice?
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-  Plato was born in 428 B.C. in Athens, Greece.  His given name was Aristocles but his nickname was Plato, which means “broad” presumably in reference to his build.
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-  Athens was a democracy and free speech abounded.  But, there is always some politics that intervenes.  Socrates would wander the city and speak his philosophy to the common folks.  He was trying to get people to examine their own ideas more closely.
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-  Socrates  maintained that an unexamined life is not worth living.  He was executed in 399 on charges of irreverence to Greek gods and corrupting the city’s youth. 
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-  Plato was in the audience when his teacher defended himself against the charges.  The jury voted 280 to 220 for the death sentence.  Plato wrote the “Apology” reflecting on the death of his teacher.
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-  Plato began writing dialogues, conversations between two people debating philosophical questions.  Much of these come from Socrates’ teachings.  In 387 Plato founded his school called the Academy.
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-  His school  offered courses in astronomy, biology, rhetoric, mathematics, philosophy, and political theory.  Above the door was written:  “Let no one ignorant of mathematics enter here.“  Aristotle was one of the students who entered.
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-  Plato’s book the “Republic” gets into the nature of justice.  A just man is one in whom every component of personality harmoniously plays its proper role, while reason is paramount.  Plato was working on defining a just society when he died in 347 B.C. 
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-  This Greek is a little hard to read but it is the thought that counts. Plato said in teaching his student:
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-  “He who thinks nothing of bodily pleasures is almost as though he were dead“.
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-  That is true
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-  “What again shall we say of the actual acquirement of knowledge?-- is the body, if invited to share in the inquiry, a hinderer or a helper?  I mean to say, have sight and hearing any truth in them?  Are they not, as the poets are always telling us, inaccurate witnesses?  And yet, if even they are inaccurate and indistinct, what is to be said of the other senses?  For you will allow that they are the best of them? “ ( i.e.:  Don’t believe everything you see or hear.)
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-  Certainly, he replied.
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-  “Then when does the soul attain truth? -- for in attempting to consider anything in company with the body she is obviously deceived“. (Take care in examining your own thoughts and the thoughts of others).
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-  Yes, that is true.
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-  “Then must not existence be revealed to her in thought, if at all?”
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-  Yes.
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-  “And thought is best when the mind is gathered into herself and none of these things trouble her -- neither sounds nor sights nor pain nor any pleasure -- when she has as little as possible to do with the body, and has not bodily sense or feeling , but is aspiring after being?”  (Some of your best thinking occurs in your sleep.  It is a good thing to sleep on your thoughts.)
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-  That is true.
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-  “And is this the philosopher who dishonors the body, his soul runs away from the body and desires to be alone and by herself.”
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-  That is true.
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-  “Well, but there is another thing, Simmias:  Is there or is there not an absolute justice?”
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-  Assuredly there is.
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-  “And an absolute beauty and absolute good?”

-  Of course.
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-  “But did you ever behold any of them with your eyes?”   (These things occur in the mind, they cannot be written, read, taught, or experienced in a bodily sense.  Material possessions, power, money, will not bring them to you.)
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(1)  Plato’s view of astronomy was that the spheres of the planets made celestial music.  The idea that the heavens only contained perfect circles was considered fact up until Kepler’s time, 2000 years later.

 (2)  Plato invented the fictitious land “ Atlantis” that adventurers are still searching for to this day.

(3)  Aristotle lectured to students while walking about in the garden.  Recent studies have shown that overweight American kids could benefit from this teaching technique.  Aristotle’s collection of manuscripts became the great Library of Alexandria.  His lectures collected into 150 volumes.

(4)  Great teachers are not always right.  Aristotle believed the heart was the center of life and the brain merely a cooling organ for the blood.  Well, on second thought, maybe he was right.  He was the first to propose the “aether” which astronomers are just now reconsidering in the “light” of Dark Energy.

(5)  Aristotle was convince that the Earth was round because traveling north appeared new stars over the northern horizon, old ones disappeared over the southern horizon.
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-  February 27, 2020                                                 651                     2635                                                                                 
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 ---------------------          Thursday, February 27, 2020    --------------------
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PLANETS - how they got their names?

-  2634  -  PLANETS  -  how they got their names?  March 2020, in the early morning you can see Jupiter, Saturn, and Pluto.  Binolulars is all you need.  Venus in the evening.  Jupiter’s moons Callisto, Europa, Io, and Ganymede are visible too.

-

-

-

---------------------   2634  -  PLANETS  -  how they got their names?

-

-   These five naked-eye planets, Mercury, Venus, Mars, Jupiter, and Saturn, have been known since antiquity. The Greeks called them Hermes, Aphrodite, Ares, Zeus, and Cronus.

-

-  Aphrodite (Venus to the Romans) caused some problems until the third century b.c. Greek observers had named it Phosphorus when it appeared in the morning sky and Hesperus for its evening showing. It was Aristarchus of Samos, born around 310 b.c., who realized that these two objects were one and the same.

-

-  Centuries later, the Romans adopted the planets of the Greeks and simply changed their names to Mercury, Venus, Mars, Jupiter, and Saturn.

-

-  All was well until 1781, when German-born English astronomer William Herschel discovered a planet beyond Saturn. For more than half a century, there was no agreement on a name, and astronomers often referred to it as the planet Herschel. The name Uranus was finally added to the list.

-

-  In 1846, the English and French mathematicians John Couch Adams and Urbain Jean Joseph Le Verrier simultaneously predicted the position of an eighth planet, which astronomers found easily.

-

-  After much wrangling, astronomers agreed on the name Neptune. Finally, in 1930, a young English girl named far-flung Pluto through an international appeal for suggestions. Uranus, Neptune, and Pluto are all names of Roman gods, so their choices preserved the overall naming scheme of the solar system.

-

-  Galileo Galilei discovered the first planetary moons around Jupiter in 1609. He wanted to name them the Medician Stars after his benefactor, Cosimo de’ Medici. However, the classical nomenclature that had prevailed for more than 2,000 years won out. Classical names were applied as more and more planetary moons were discovered.

-

-  Jupiter’s moons are Callisto, Europa, Io, and Ganymede and 63 other moons

-

-  The mold was broken at Uranus when planetary scientists named its moons after characters found in the works of Shakespeare: Umbriel, Titania, Oberon, Ariel, and 23 other moons

-

-  Uranus moons Mirnda, Ariel, Umbriel, and Oberon and 23 smaller moons

-

-  Alexander Pope named Neptune’s moons  from Greek water gods:  Triton, Nereid, Nesso, Proteus, and 10 other moons

-

-  Pluto’s moons came from mythological inhabitants of the underworld.  Charon, Nix, and Hydra.

-

-  The Greeks gave our Moon the name Selene, and Earth was Gaia. Both our modern words Earth and Moon derive from Middle English. So rather than Gaia or Selene, we have just plain old Earth and the Moon.

-

-  Not quite as romantic when astronomers name stuff.

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------------------------------  Other reviews about the planets:

-

-  2448  -  PLANET NINE  -   could it be a blackhole?    Maybe there is an ancient, grapefruit-size blackhole hiding out in our solar system.  This tiny, heavy object might in fact take the place of a theoretical planet that might be tugging on other objects in our solar system. 

-  

-  965  -  The chemistry of planet formation.  The Chemistry of Planet Formation.  We have 8 planets in our Solar System.  Our Sun is only one star and there are billions of stars in our own galaxy.  How many other stars have planets?   The answer today is 322 planets have been found around other suns , and, we are adding new planets at the rate of one per week

-

-  935  -  Planet temperatures.  If  you walk into a wine cellar , it’s cold. A few feet underground it is a constant 55 F.  So you may think that the deeper you go the colder it gets.  Not so.  After 20 feet the temperature begins to climb 1 F for every 100 to 200 feet.  When you get to the center of the Earth it is 8,500 F.  The surface of the Sun is 11,000 F.  An inventor in Idaho, ex-HP, is designing a thermo pump, ( a reverse refrigerator ) to take advantage of the temperature differences between the surface and deep underground.  It becomes a cheap, sustainable energy source.

-

-  928  -  Planet formation. No other place has been found in the Cosmos that could support life as we know it.  But, that has not stopped us from looking.  Astronomers have found more than 200 planets in other solar systems.  How they formed and how they contain such wide diversity is a new mystery.  We thought we had a design for planet formation that matched our Solar System.  In contrast, other solar systems are so diverse and supposedly formed out of chaos.

-

-  919  -  Planet travel. Planet Travel. Astronomy today has technology that is beyond the imagination.  And, at the same time we have imagination far beyond our technology.  Let me give you an example.  In the fall of 2007 astronomers observed a planet that transits in front of its star.  It is 63 lightyears away in the Constellation Vulpecula.  

-

-  840  -  Planet Pegasi and Dopper astronomy. The planet 51 Pegasi b was discovered in 1995.  It was the first planet discovered orbiting a normal star, like our Sun.  When watching the star astronomers were able to detect a rhythmic wobble using the Doppler Shift Technique. 

-

-  839  -  Our gaseous planets.-  Our Gaseous Planets.  Astronomers have discovered over 250 planets outside our Solar System.  An the same time they reduced the number of planets in our Solar System from nine to eight.  After 75 ears the ninth “planet” got plutoed and kicked out of the planet category and in to the Kuiper Belt with the rest of the big icy comets.

-

-  710  - Fourier discovers he terrestrial planets.

-

-  691  -  Other planets in other solar systems.

-

-  591  -  Osiris , a planet around another star.  

-

-  41  -  The five visible  planets.

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-  29  -  Our gaseous planets.

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-  February 26, 2020                                                                          2634                                                                             

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-----  Comments appreciated and Pass it on to whomever is interested. ---- 

---   Some reviews are at:  --------------     http://jdetrick.blogspot.com -----  

--  email feedback, corrections, request for copies or Index of all reviews 

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 ---------------------          Wednesday, February 26, 2020    --------------------

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METEORS - we call them shooting stars.

-  2633  -   METEORS  -  we call them shooting stars.  How four small pieces of rock can teach us about the history of the solar system.  The first  is a meteor from outer space that hurtled through the atmosphere of a bright, blue planet to land upon a world populated by strange, multi-tentacled creatures.

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---------------------   2633 -  METEORS  -  we call them shooting stars.
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-  It sounds like something from the pages of a science fiction novel, but it’s a true story and it’s written in stone.   At the time of the World’s Columbian Exposition in 1893, the collection of curiosities that would become the Field Museum included 170 meteorites. The museum collection  includes more than 15,000 meteorites from over 1,500 falls.
-
-  “A fall,” is an event in which the arrival of a meteorite is observed and recorded. This allows fragments to be identified with that event. Meteorites not identified with a fall are known in the field as “finds.”
-
-  The museum has a thousand-pound remnant of the Canyon Diablo meteorite that gouged the great meteor crater in the Arizona desert. There are fragments of the Chelyabinsk meteor, which made a fiery descent over Russia in 2014. There is even a meteorite that fell on a garage in Illinois in 1938, displayed alongside the holed seat and dented muffler of the car it struck.
-
-  But possibly the most intriguing meteorites in the collection are four that are embedded in slabs of limestone. They are surrounded by a whitish discoloration of the rock, evidence of something leaching from them. These are “fossil meteorites“.
-
-   One of them rests only inches away from the mineralized shell of a cephalopod, an extinct mollusk related to the modern nautilus. Fossils of prehistoric sea creatures are common in rocks dating from the Ordovician Period, which lasted from 500 to 435 million years ago.
-
-   But fossil meteorites are rare. In fact, they were unknown until 1952, when the first find was made in Sweden. To date, only 115 have been found, almost all of them at a single quarry.
-
-  Striations in the stone there represent layers of sediment laid down over millions of years, when this place was at the bottom of an ancient sea. In that age there were no land animals or even true vertebrates; the first dinosaurs were still 230 million years in the future.
-
-   Life was in the ocean, teeming with creatures now long gone. Trilobites scuttled along the sea floor and crinoids waved with the movement of the water. Among them swam cephalopods of the genus Orthoceras residing within a long, conical shell, tentacles groping for whatever  creature would become its next meal. 
-
-  This was the pattern of life in the Ordovician ocean; preserved by the long, slow process of fossilization to record a chapter in the history of life on Earth. But something extraordinary happened in the middle of the Ordovician Period. Meteorites began to fall among the future fossils, lots of them.
-
-   As the meteorites settled into the sea floor, they were buried along with the remains of the sea creatures to become fossils themselves. And just as the fossilized animals tell a story about the history of life on Earth, the fossil meteorites relate a chapter in the history of the solar system.
-
-  That story begins in the asteroid belt. The vast majority of meteorites that fall to Earth come from this ring of irregular, rocky bodies that never managed to form a planet. The asteroids occasionally jostle each other and when they do, the bits and pieces broken from them are sometimes sent Earthward.
-
-  470 million years ago, there was a titanic collision among the asteroids. It shattered one of them completely in the biggest breakup the solar system has seen in the last 3 billion years. Immense amounts of debris from this collision were flung toward the inner solar system, where it quickly subjected Planet Earth to an intense bombardment. On a cosmic time scale, the number of meteorites falling to Earth jumped overnight.
-
-  The first step in proving the story is to verify that the objects found in the Thorsberg quarry are meteorites.  Identifying fossils as meteorites poses a special challenge. They have been buried and embedded in stone for hundreds of millions of years. Just as the seashells underwent a mineralogical change, turning to stone over the eons, so did the meteorites.
-
-   The meteorites, of course, were already stone, but they underwent a process which changes their mineral content. That’s what caused the whitish discoloration in the stone surrounding them. Researchers have to study their microscopic structure, along with their chemical composition, to be sure of their identity.
-
-  The presence of the mineral chromite (FeCr2O4) in the fossils was one thing that identified them as meteorites.   Another important giveaway is the presence of chondrules: small, round particles found embedded inside the meteorite.
-
-  Although meteorites come in many varieties, there are three basic types:  iron, stony iron, and stony. Stony meteorites are by far the most common, making up about 96 percent of those that fall to Earth. They are composed largely of silicate minerals, such as olivine and pyroxene.
-
-   Iron meteorites are mostly iron, although they often contain other elements, such as nickel and cobalt.
-
-   Stony irons, the most rare of the three types, combine the characteristics of the other two.
-
-  The type of meteorite depends on where it came from in the parent body that broke apart to produce it. Some asteroids are differentiated, they have an iron core surrounded by a rocky mantle and crust, just as Earth does. Differentiation occurs when a body is heated by collisions or radioactivity to the point where its materials can flow. The iron meteorites come from the core of such a body, stony irons from a narrow region between the core and mantle, and stony meteorites from the mantle and crust. 
-
-  Stony meteorites also come from asteroids that are not differentiated. Some asteroids were never hot enough to form an iron core, but did generate enough heat to melt bits of material embedded in them. These melted mineral grains are called chondrules and meteorites that contain them are called chondrites.
-
-  Having established that the embedded stones in the quarry are meteorites, and specifically that they are chondrites, can scientists go a step further in demonstrating that they all came from the same parent body?
-
-  As a matter of fact, they can, because chondrites come in several varieties. The family of ordinary chondrites  includes three basic types: These are the H, L and LL chondrites.
-
------------------------------  The H chondrites have a relatively high metal content;
-
------------------------------  the L chondrites have a low metal content;
-
------------------------------  the LL chondrites have both a low metal content overall and a low iron content relative to other stony meteorites.
-
-  Of the meteorites that fall to Earth today, 38 percent are L chondrites. In contrast, all of the fossil meteorites  found to date are all L chondrites. They were the predominant type of meteorite in the Ordovician and moreover, they all came from the same asteroid, the L Chondrite Parent Body.
-
-  The limestone in which they are embedded was laid down as layers sediment over millions of years. The bottom layers are the oldest and the upper layers are the youngest.
-
-  Geologists determine the ages of the layers by several methods. By applying sedimentation rates measured in modern environments, they can estimate how long it took to build up a layer.
-
-  Index fossils, which are fossils of species known to have lived at a particular point in time, can pinpoint the age of a specific layer. There were many species of the mollusk  and they are so common. Finally, the decay products from natural radioactivity can date the rocks.
-
-  A combination of these methods shows that the L chondrites began to arrive here just under 470 million years ago. And when they arrived, they came en masse.. The search has covered all of the old sea floor that has been quarried since then.  The abundance of meteorites on the mid-Ordovician sea floor is far too high to be explained by a meteorite flux similar to that of today.
-
-  When the debris breakup began to reach this planet, meteorites fell with a frequency 100 times the modern rate for a million years. Furthermore, data from preserved craters indicates an order-of-magnitude increase in the flux of small asteroids as well.
-
-  Not only did the L chondrites bombard Earth in huge numbers, they did it very quickly. The typical travel time for a meteorite is millions to tens of millions of years. This is the time from when its parent body breaks apart to when a piece of it lands on Earth as a meteorite. The fossil meteorites began to arrive mere tens of thousands of years after the breakup of the meteor.
-
-  How is it possible to know how long a meteorite traveled through interplanetary space? There would have to be some kind of clock built into it. There is such a clock and the chemists are able to read it by measuring the amount of certain rare isotopes of elements that are in the meteorite.
-
-  The clock works like this: Every atom of every element has a mass number equal to the combined number of protons and neutrons in its nucleus. For example, helium with two protons and two neutrons has a mass number of 4 and is written as 4He.
-
-   Likewise, an atom of neon normally has 10 protons and 10 neutrons and is denoted as 20Ne. In rare cases, a nuclear reaction can produce a nucleus with fewer or more neutrons than normal, resulting in isotopes like 3He (2 protons, 1 neutron) or 21Ne (10 protons, 11 neutrons).
-
-   On Earth, naturally occurring neon has only about a quarter of a percent 21Ne; naturally occurring helium has a mere ten-thousandth of a percent 3He. These rare nuclei are produced by cosmic rays, the high-energy radiation that permeates outer space
-
-  While an asteroid is intact, the rock in its interior is shielded from the cosmic rays and isotopes are not produced. When the asteroid breaks apart, the fragments are exposed to cosmic rays and production of isotopes begins.
-
-  When the fragment falls to Earth as a meteorite, it is shielded once again by  Earth’s atmosphere and production of the isotopes stop. Thus, the quantity of isotopes in the meteorite provides a measure of how long it was traveling in space.
-
-  Isotopes of 3He and 21Ne were cross-checked against the layers of rock where they were found. Their remarkable result was that the older the rock layer, the less time the meteorites in it had spent in transit. This is basically the result you’d expect if all of the meteorites came from a single parent body, with the ones making the shortest trip sitting here longest.
-
-   As if being embedded next to a cephalopod didn’t make it rare enough. The probable explanation for this rapid transit is that the breakup occurred near an orbital resonance,  a spot where the gravity of Jupiter pulled them out of the asteroid belt and onto an Earthbound expressway.
-
-  Meteoritic material is constantly falling to Earth. The planet typically gains about five tons per year from meteorites, much of it in the form of tiny grains or microscopic fragments coming off of larger bodies.
-
-  With the proper chemical methods, these micrometeorites can be recovered from the limestone. In a recent international study, scientists recovered micrometeorites from a Russian quarry and studied their isotopes to determine their type. They found that prior to 470 million years ago, most of the meteorites falling to Earth were stony meteorites.
-
-  Over the years, some scientists have conjectured that meteorites have been at least partially responsible for mass extinctions and subsequent evolutionary events. So far, only the Chicxulub Meteor, which struck at the end of the age of dinosaurs, is known to be associated with such an event. A more thorough understanding of fossilized meteorites could further test such hypotheses.
-
-  Just before midnight on March 26, 2003, residents of Park Forest, Illinois, were startled by what many thought was a bomb. Bright flashes in the sky, resounding booms and falling debris were reported throughout this Chicago suburb. It was, of course, a meteorite. Several homes were hit and one strike left the occupants looking up at a softball-sized hole in their ceiling. Fortunately, nobody was hurt.
-
-  For the Chicago Center for Cosmo-chemistry at the nearby University of Chicago and for the Field Museum, the fall was a bonanza. When the fragments were collected and studied they were found to be L chondrites from the same source as the fossils in the Thorsberg quarry.
-
-  Pieces of the Park Forest meteorite now reside in a display case alongside the fossil meteorites from Sweden. After 470 million years, they are reunited at last.
-
-------------------------------------  Other reviews about meteors:
-
-  2586    METEORITE  -  the oldest meteorite?  A meteorite that crashed into rural southeastern Australia in a fireball in 1969 contained the oldest material ever found on Earth, stardust that predated the formation of our solar system by billions of years
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-  2389  - METEORS  -  we call them shooting stars. Shooting Stars are meteoroids that enter Earth’s atmosphere in the night sky.  On average on a dark night you can see a shooting star once an hour.  These meteoroids are rocky dust and debris zipping around our solar system at 30,000 mph.
- 
-  2343-  The Story of a Rock  A meteorite rock was found in Oman, Africa in September, 2002.  The rock tells us that it came from the Moon and it even tells us which crater on the Moon it was ejected from.  About 30 Earth rocks have been found and identified as originating on the Moon.  This is the story of two of these rocks.  The first rock was found in Oman. a country southeast of Saudi, Arabia on the Arabian Peninsula.               
1619  -  How often do meteors hit Earth and how big are they?  What were the more famous meteors that impacted Earth.  What is the likelihood another big one is on its way?
-
-   1611 -  Meteor Impacts. How many meteors of all types hit us each year? When is the next big hit expected? Learn the equations that give the answers.
-
-  1567  -  The Russian Meteor  -  The Russian Meteor. Valentine’s Day was a real surprise for many people in Russia.  February 14, 2013, a 10,000 ton meteor blasted through the atmosphere.  The fireball was traveling 40,000 miles per hour.  The shockwave created when the meteor hit the atmosphere blew out glass windows in over 3,000 buildings, over a 1,000 square kilometers.  Over 1,000 people were injured.  Mostly glass cuts, one with a broken back.  People instinctively went to the windows to see what caused the giant flash of light.  They were standing in front of the windows when the shockwave reached them.
- 
-  1557  -   Tektites in Healdsburg, California  - January 23, 2013, our local paper ran an article about the tektites found in Dry Creek Valley around Healdsburg, California, just 20 miles from my house. What in the world are tektites?
-
-  1019  -  The Sudbury Asteroid.  A giant asteroid struck Earth 1,850,000,000 years ago creating the Sudbury Basin in Ontario, Canada.  The impact blew a crater in the shallow sea floor that was 160 miles across.  Along the seashore were dense colonies of cyan bacteria.  Their stumpy masses are call stromatolites.
-
-  1017 -  Meteorite and Asteroids.  Meteorites have been landing on the surface of Earth for millions of years.  We have found many of them.  You can buy them on E-Bay.  In 2004 in Placid, Florida a 5.3 pound asteroid was recovered.  E-bay says it came from the planet Mercury so it would yield a higher price.  But, astronomers do not think it came from Mercury.  They believe it came from the Asteroid Belt.
-
-   719  -  Geminid Meteor Shower. December 14, 2006, is the peak of the Geminid meteor shower in the night sky.  A meteor is a streak of light, often called a shooting star.  We see the light trailing a meteoroid.  A meteoroid is an interplanetary object that is bigger than a speck of dust and smaller than an asteroid.
-
-   523  -  The Story of a Rock

-  February 25, 2020                                                                          2633                                                                                 
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-----  Comments appreciated and Pass it on to whomever is interested. ----
---   Some reviews are at:  --------------     http://jdetrick.blogspot.com ----- 
--  email feedback, corrections, request for copies or Index of all reviews
---  to:  ------    jamesdetrick@comcast.net  ------  “Jim Detrick”  -----------
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 ---------------------          Wednesday, February 26, 2020    --------------------
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latest index

-  Send number to get a copy:
-
--  2622  -   NANOTECHNOLOGY  -  solar cells from nanowires?    Energy is the number one problem we will face in the next few decades. This year the world uses 14,500,000,000,000 watts of power.  Most of this energy is generated using gas and oil.  Only 1 % of our energy comes from solar, wind, or geothermal.  In the year 2050 we will be using somewhere at least 30,000,000,000,000 watts of electricity. 
-
-  2623  - -  NANOTUBE  -  how to build a radio?  A whole new radio has been invented using nanotechnology.  The radio is so small it cannot be seen without the aid of a microscope.  The radio is a single carbon nanotube that is much smaller than a wavelength of light.   
-
-  2624  -   GOVERNMENT   -    How much does the government spend and where does the m  My ie handles the family budget.  I worry about the big things.-
-
-  2625  -   EULER’S FORMULA  - Topology for 6th Graders ?  Euler’s formula applies to all types of solids and surfaces and it is not always equal to 2.  A different equation will define a different type of solid.  Let’s take a donut for example.  This category of shape is called a “torus”, but the donut is more familiar.  -
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-  2626   -   CALENDAR  -  why 7 days, and daylight savings?   Alexander the Great  shifted to the seven-day week. I Emperor Constantine who decreed that the seven-day week was the official Roman week and made Sunday a public holiday in A.D. 321.  One hundred years ago Congress passed the first daylight saving legislation.-
-
-  2627  -   ASTEROID  -  to hit Mother Earth.  It is not an if, it is a when.  Astronomers are tracking Near Earth Asteroids, NEAs.  There are many, and each one needs to be identified with an orbit trajectory to learn if it will be a threat.  OK, let’s just say they see one coming right at us.  What then?-
-  2628  -   GRAVITY  WAVES  -  from supernovae explosions?  Is the speed of gravity instantaneous, or is there a speed limit on how fast the force of gravity can travel. This is not as simple a question.  After all, we know how fast light travels, and if the Sun were to suddenly wink out of existence, we’d still receive light from it for just over 8 minutes after it disappeared!-
-
-  2629  -   GALAXIES  -  how do they form and grow?  Astronomers don’t yet fully understand how those original massive stars themselves are initially formed. So far, observations have only yielded some pieces of the puzzle. This is because nearly all the known massive stars in our galaxy are located very far away from our solar system. They also form in close proximity to other massive stars, making it difficult to study the environment where they take shape.-
-
-  2630  -  OLBERS  PARADOX  -  why is the sky dark?  -    Olbers' paradox, named after the German astronomer Heinrich Wilhelm Olbers (1758–1840), also known as the "dark night sky paradox", is the argument that the darkness of the night sky conflicts with the assumption of an infinite and static universe. -
-
-  2631  -   DARK  MATTER  -  dark coffee would help?  Astronomer’s observations have determined the average density of matter in our universe to very high precision. But this density turns out to be much greater than can be accounted for with “ordinary atoms“.  Is there some other matter that we still don’t know about?-
-
-  2632 -  DARK  ENERGY  -  some form of anti-gravity?  - Is dark energy the “cosmological constant“. The fact that we see the Universe expanding as it does means that there must be some new form of energy causing these distant galaxies to recede from us faster and faster as time goes on.-
-
-  2633  -   METEORS  -  we call them shooting stars.  How four small pieces of rock can teach us about the history of the solar system.  The first  is a meteor from outer space that hurtled through the atmosphere of a bright, blue planet to land upon a world populated by strange, multi-tentacled creatures.

-

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-----  Comments appreciated and Pass it on to whomever is interested. ---- 

---   Some reviews are at:  --------------     http://jdetrick.blogspot.com -----  

--  email feedback, corrections, request for copies or Index of all reviews 

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 ---------------------   Wednesday, February 26, 2020  -------------------------

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DARK ENERGY - some form of anti- gravity? -

-  2632 -  DARK  ENERGY  -  some form of anti-gravity?  - Is dark energy the “cosmological constant“. The fact that we see the Universe expanding as it does means that there must be some new form of energy causing these distant galaxies to recede from us faster and faster as time goes on.
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-

-
---------------------   2632 -  DARK  ENERGY  -  some form of anti- gravity?
-
-  See Review 2631 about Dark Matter.  Dark Energy is totally different and even more mysterious to astronomers.  Dark Matter is 23% of the Universe and Dark Energy is 72% of the Universe.  Remember that mass and energy are 2 forms of the same thing:
-
------------------------    Energy  =  Mass * (speed of light)2
-
-  Of all the revolutionary discoveries that we've made about the Universe, the most unexpected and surprising has to be Dark Energy. Ever since the Big Bang the force  between the initial expansion, working to drive everything apart, and gravity working to pull everything back together, the Universe has behaved as though these two opposing influences were in perfect balance.
-
-  Then,  6 billion years ago, the expansion all of a sudden started speeding up again, causing distant objects to accelerate. “Dark Energy” is the name we give to the unknown cause of this unexpected phenomenon, but suddenly things don't add up.
-
-  Does dark energy produce gravity?  Does the increase in dark energy as space expands also create more gravity?
-
-  The mathematics governing General Relativity is quite complicated, and General Relativity itself offers many possible solutions to its equations. But it's only through specifying the conditions that describe our Universe, and comparing the theoretical predictions with our measurements and observations, that we can arrive at an understandable theory.
-
-  Every form of energy in the Universe, no matter how weird, exotic, or unfamiliar it is, obeys the same law of gravity, that is “Einstein's General Relativity“. Most of the types of energy we are used to come in the form of quanta: tiny little point-like packets of energy that move through the fabric of spacetime.
-
-  Some of those quanta are “radiation-like“, meaning they move at the speed of light. Others are “matter-like“, meaning they're moving slower compared to the speed of light.
-
-  Examples are photons, which always act like radiation, normal matter and dark matter, which always act like matter, and neutrinos, which behave like radiation in the early Universe.
-
-  All massless particles travel at the speed of light, including the photon, gluon and gravitational waves, which carry the electromagnetic, strong nuclear and gravitational interactions.
-
-  Any particle with a non-zero rest mass will travel slower than light, and as the expansion of the Universe causes it to lose kinetic energy, eventually it will become non-relativistic, behaving as matter rather than radiation.
-
-  The reason for this dichotomy is that every particle has two types of energy it can possibly possess:  rest-mass energy, which is the amount of energy inherent to the particle itself, via Einstein's most famous equation, E = mc2,  and kinetic energy, which is the energy due to the particle's motion through the Universe.
-
-  As the Universe expands, the number of particles remains the same but the volume that they occupy, the size of the Universe, increases.
-
-  How the matter density drops over time should dilute as the volume does: in proportion to the size of the Universe cubed. But if you have a lot of kinetic energy, or you're something like a massless photon where your energy is defined by your wavelength, not only do you dilute with volume, but your wavelength also gets stretched as your Universe expands. Radiation, therefore, dilutes in proportion to the size of the Universe to the fourth power.
-
-  Radiation is dominant over matter for roughly the first 9,000 years, but remains an important component, relative to matter, until the Universe is many hundreds of millions of years old, thus suppressing the gravitational growth of structure.
-
-  But there are other forms of energy the Universe is allowed to have besides particles. In particular, three different ideas have existed for a long time that all have energy, but all have their own evolution.
-
-  Cosmic strings: which are long, thin, one-dimensional strands of energy that stretch across the Universe.  As the Universe expands, cosmic strings can still span the entire Universe in one dimension, but will take up less of the Universe's volume in the other two.
-
-  Domain walls: which are long, thin, two-dimensional sheets of energy that stretch across the Universe.  Domain walls can span the whole Universe in two dimensions, but will still dilute in the one other dimension.
-
-  Cosmological constant: which is a form of energy that's inherent to the fabric of space itself.  For a cosmological constant, the fact that space is expanding just means that there's more volume, and it doesn't dilute at all. The energy density will remain a constant.
-
-  Is “dark energy” the “cosmological constant“? The fact that we see the Universe expanding as it does means that there must be some new form of energy causing these distant galaxies to recede from us faster and faster as time goes on.
-
-  But if the energy present in the Universe is what causes gravity to work, as all the different forms of energy attract all the other forms of energy, then why are progressively more distant galaxies appearing to accelerate away from us as the Universe ages?
-
-   You would think that if the Universe possessed a cosmological constant, it would be gaining energy as the Universe expanded, and would gravitate more, slowing the expansion rate down. But that isn't what happens at all.
-
-  The four possible fates of our Universe into the future; the last one appears to be the Universe we live in, dominated by dark energy. What's in the Universe, along with the laws of physics, determines not only how the Universe evolves, but how old it is. If dark energy were about 100 times stronger in either the positive or negative direction, our Universe as we know it would have been impossible.
-
-    Why does the presence of dark energy, either in the form of a cosmological constant mean that distant galaxies are accelerating away from us at faster and faster speeds as the Universe continues to expand?
-
-  The answer is because we live in a Universe governed by Einstein's laws, and we have to follow what those laws tell us, even the parts of it that are counterintuitive. Einstein first put forth his greatest theory of all, General Relativity, in 1915.
-
-   Using this theory  Karl Schwarzschild worked out the solution for a non-rotating black hole. Other solutions soon followed: for an empty Universe; for gravitational waves; for a cosmological constant all by itself.
-
-   But the most important advance came in 1922, when Alexander Friedmann derived the general solution for a Universe filled with energy that was both isotropic (the same in all directions) and homogeneous (the same in all locations in space).
-
-  The two equations he derived are, even today, still known as the Friedmann equation, and fortunately we only need to examine the first one to learn how the Universe expands dependent on what forms of energy are in it. The first term in the equation is the Hubble expansion rate (squared): a measure of how quickly the fabric of space is stretching at any moment.
-
- All of the other terms in the equation represent a combination of:
-
---------------------------------  all the matter,
-
--------------------------------  all the radiation,
-
--------------------------------  all the neutrinos,
,
--------------------------------  all the dark energy, if it is a cosmological constant
-
-   Because the dark energy density remains a constant, the expansion rate will never drop below a certain amount if dark energy is real.  When the Universe expands enough that the density of everything else becomes negligible, the expansion rate will asymptote to a constant as well.
-
-  For our Universe, this means that the expansion rate will never drop below about
-
--------------------  55 kilometers / second / Megaparsec, about 80% of its present value ,
-
-------------------  which is: ------------- 74.2 km / sec/ Mpc
-
-------------------  which is: -------------------  49,300 miles per hour / million light years distance
-
-  Whether the expansion of the Universe accelerates or decelerates depends not only on the energy density of the Universe , but also on the pressure of the various components of energy. For something like dark energy, where the pressure is large and negative, the Universe accelerates, rather than decelerates, over time.
-
-  For matter, the pressure is negligible so long as it's moving slow compared to the speed of light. For radiation, the pressure is positive, meaning the expansion rate slows more quickly than it does for matter alone.
-
-  But for dark energy, the pressure is not only negative, it's three times as powerfully negative as radiation pressure is positive. For dark energy, the pressure is actually equal to the negative of the energy density.   Instead of decelerating, the Universe accelerates when dark energy dominates.
-
-  There is a large suite of scientific evidence that supports the picture of this expanding Universe and the Big Bang, complete with dark energy.  This leads to an even more counterintuitive result: as the Universe continues to expand, dark energy means that the total amount of energy contained within our observable volume always increases.
-
-  Yet as it does, the Universe doesn't decelerate, but rather speeds up. The most sacred laws in all of physics, the conservation of energy, only applies to particles interacting in a static spacetime. When your Universe expands (or contracts), energy is no longer conserved.
-
-  There is an amount of energy intrinsic to the fabric of space itself, but the effects of the energy density are overwhelmed by the effects of the negative pressure that arises. The Universe's expansion doesn't slow down due to the presence of dark energy, but rather distant galaxies will speed away faster and faster due to its cumulative effects.
-
-   For anything beyond our Local Group of galaxies, its fate is already sealed: it will speed away, faster and faster, until we can no longer access it in our accelerating Universe.
------------------------------
-
------- Other reviews about Dark Energy and see Review 2631 to learn about Dark Matter.
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-  2337  -  Dark Energy  -  When the Universe began, gravity soon separated away from the three other forces.  This happened at 10^-43 seconds and at a temperature of  10^32 degrees Kelvin.  Gravity is the force that pulls masses back together.  But, there is another force that is expanding the Universe.
-
-  2297  -  Dark Matter is the gravity that is holding each galaxy together.  Dark Energy is the anti-gravity that is hurling separated galaxies away from each other at an ever accelerating rate.  Astronomers and physicists cannot explain either one.  These two unknowns occupy 23% and 72%, totaling 95%, of all the matter-energy in the Universe.  Everything we know and understand is in the remaining 5%.  We have a lot to work on.
-
-  2257  -  What is the fate of our Universe?  The key to unlocking our ultimate cosmic fate is dependent on our understanding what we are looking at   And then ensuring that our answers aren't biased by the assumptions we're making about the objects we're measuring. Dark energy may not be a constant.  Stay tuned, an announcement on the fate of the Universe will follow.
-
-  2138  - -  The Birth of My Universe.  The Universe was homogeneous before Inflation happened. and because it expanded much faster than the speed of light it remained homogeneous.  The velocity of the expansion today is 47,000 miles per hour for every million lightyears distance. In 1998 astronomers discovered that this velocity was accelerating.  There is some type of Dark Energy in the vacuum of space that is accelerating the expansion of the Universe.
-
-  2112  -  Cosmological constant , the fudge factor that expanded the universe.  The fudge Factor that expanded the Universe. .  We know the Universe is not only expanding its expansion is accelerating at an ever faster rate.  Now, science is resurrecting the cosmological constant fudge factor  in order to use Einstein’s equations to explain an accelerating expansion that began 5 billion years ago.
-
-  2105  -   Energy Expanding Universe.  Universe is expanding at 49,306 miles per hour per million lightyears distance.  .  Eventually at the edges of the Universe the separation speed exceeds the speed of light.  Then light from those galaxies at the edge will never reach us.
-
-  1896 -  Dark Energy and the expansion of the Universe.  Astronomers are trying different methods to measure the accelerating expansion of the Universe.  The hope is for new discoveries to point to the source of “Dark Energy” that is creating this repulsive force.
-
-  1884  -  What we know about the expansion of the Universe?  Making accurate distance measurements to stars and galaxies is an amazing challenge for astronomers.  This review discusses how we got to what we think we know about the Universe’s expansion and what could be causing it.
-
-  1864  -  How is Dark Energy expanding the Universe?  Why is this expansion rate accelerating?  Where does the energy come from?  What is the likely end result?
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-  1855  - Cosmology,  studying energy flows and statistics.  -  Cosmic Inflation requires that the Actual Universe to be much larger then the Observable Universe.  The observable is 93 billion lightyears diameter.
-
-  1800  -  Dark Energy  -  Something is counter acting Gravity.  For the first 7 billion years gravity was king.  Then, something else took over once expansion reached this point. Now the Universe is expanding at an ever accelerating rate over this next 7 billion years.
-
-  1749  -  No matter where you go in the Universe your field of reference has everything expanding away form you, an at ever accelerating rate.   Dark Energy Expanding the Universe.  What is it that is causing the Universe to expand at an ever increasing rate?  What force is overcoming the force of gravity?
-
-  1594,  1595,  1596, 1597, 1599  -  Reviews to study why is 95% of the Universe “dark”. 
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- 1516  -  If the Universe density were greater then 10^-29 grams / cm^3 then gravity would win over repulsion expansion.  We need to find 200 times more Dark Matter in order to reach this “ critical density”.
-
-  1499  -  Graph of Universe composition versus Redshift expansion rate.
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-  1290  -  Calculations of the average density of the Universe. Ours is a dynamic universe unbalanced by the mysterious Dark Energy. Why is Dark Energy Expanding the Universe?  Most astronomical data we have today confirms the fact (theory in fact) that the Universe is still expanding at an ever increasing rate.  The cause is suspected to be some type of anti-gravity that is named “ Dark Energy”.    We know what gravity is and we expected gravity to eventually stop the expansion and reverse the Universe into a “ Big Crunch”.   However, we now think that Dark Energy is the predominate force in the Universe and that it will expand the Universe forever into a “Cold , Rarified Space of almost Nothing”
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-  1147  -  Dark Energy is not predicted by any physics we know of.  Here are 3 theories that are in the works.
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-  1083 -  1084  -  1085 -  Dark Energy  -  Equation for how fast mass would have to decrease to keep the speed of light at 186,600 miles per second.
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-  1047  -  Is the Universe like Swiss Cheese?
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-  822  -  Things are “Dark” because we can’t see them and we do not know what they are.
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-  715 -  Cosmic Dark Ages.  First billion years after the Big Bang.
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-  660  -   then there are Dark Matter reviews , and Cosmic Inflation reviews
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-  374  -  What is dark matter?  How do we know it is there? 
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-  February 24, 2020                                                                            2632                                                                               
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 ---------------------          Tuesday, February 25, 2020    --------------------
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