- 2348 - The Universe from start to finish. Studying Cosmology gets you into some fun physics and math calculations that try to explain observations. This in turn results in new discoveries because things don’t always match up. How did things become as they are?
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---------------------- 2348 - The Universe from start to finish.
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- The strongest bond between cosmology and everyday life resides not in religion and philosophy but in the ability of science to pursue questions of universal simplicity about how things came to be as they are.
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- The skepticism of questioning, subversive and perpetually dissatisfied spirit that is the characteristic of science. A theory can be sensible and beautiful and still quite wrong.
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- Galileo: " Pure logical thinking cannot yield us any knowledge of the empirical world; all knowledge of reality starts from experience and ends with experience."
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- The Earth's equator is moving east at 1000 miles per hour. Eratosthenes, a Greek scholar, in 300 B.C. figured the Earth was round. He was in Egypt in the town of Syene, now called Aswan. On June 21 every year he noticed the Sun shined to the bottom of the deep well that was in the town center.
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- At the same time in Alexandria, directly north of Syene a ten foot stick pointing straight up cast a 16 inch shadow on the ground. Sighting directly at the Sun he measured the angle at the top of the stick to the sun's rays to be 7 and one-half degrees. The distance between the two towns was almost 50 days travel by camel, walking about 10 and one-half miles each day.
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-----------------------10.5miles/day *49.5days = 519.75miles * 360 degrees / 7.5 degrees = 24,948 miles.
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----------------------- Divide by pi and get 7,926 miles for the diameter pf he Earth. It took a camel driver to figure that out.
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- Let's try parallax to measure the distance to Mars before we use it on the stars. If we line up Mars and a star directly behind it, say at 80 degrees. Then on the opposite side of the globe do the same thing; there will be a slight angle difference due to parallax from the two vantage points.
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- If this angle is measured to be 0.0092 degrees, you notice it is very small. We can make a couple right triangles and calculate the distance to Mars. It is 7,926.21 miles* cosine 80 * tangent 80 / tangent 0.0092 degrees plus 7,926.21 miles * cosine 80 degrees = 48,614,310 miles.
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- The Earth's and other planet's orbital velocity increases when it is nearer the Sun and decreases when it is farther away such that the rate sweeps an equal area within its orbit over equal intervals of time.
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- When orbits are elliptical , over a fixed time, these triangles are long and narrow far out and short and fat when close in but the areas of the two triangles are equal.
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- In 1761 and 1769 Venus crossed the face of the Sun and that yielded a fairly accurate value of the size of the Earth's orbit.
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---------------------- The period of Mars is measured to be 1.88 years (686.98 days).
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----------------------- The orbit of Mars is 141,595,165.14 miles.
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----------------------- The formula is the period of Mars squared divided by the period of the Earth squared = the orbital radius of Mars cubed divided by the orbital radius of the Earth cubed
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----------------------- This formula works for any two bodies in orbit about the same mass.
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----------------------- 1.88 years squared / 1year squared = 141,595,165.14 miles cubed / Earth's orbit
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----------------------- The orbit radius of Earth is 92,955,806.84 miles ( mean distance).
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----------------------- Jupiter's period is 11.83 years.
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----------------------- The orbit of Earth is 93 million miles, but that's called one astronomical unit, AU.
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----------------------- So, 11.86 years squared / 1 year squared = Jupiter's orbit cubed /
1 AU cubed.
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----------------------- Jupiter's orbit is 5.2 AUs or 483.6 million miles.
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- Once the orbit diameter was known “parallax” could be used to calculate the distance to the stars. In 1838 Cygni was measured at 11 light years away.
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- How small of an angle would you have to measure to measure the distance to Sirius, which is 8.6 lightyears away? One lightyear is 63,240 AU, astronomical units ( distance Earth to Sun ). 8.6 lightyears is 543,864 AUs. The tangent of the angle = sine 80 degrees ( angle we first used to line up Sirius with a more distant star or galaxy behind it ) * 2 AU ( Earth's orbit diameter ) / 543,864 AU.
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- The angle we would measure would be only 0.002075 degrees
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- Gaseous nebulae, clouds of gas and dust, are typically measure to be a few tens of light years in diameter. Spiral nebulae are billions of stars and typically measure 100,000 light years in diameter. Spiral nebulae are millions of light years away. They look about the same through the telescope. Astronomers had to learn the difference before their next leap in understanding the distances in the universe.
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- In 1925 Edwin Hubble photographed individual stars in a spiral nebulae, now called a spiral galaxy, once we knew what it was.
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- When something expands it cools. Matter is really just frozen energy. When the Universe expanded after the big bang , or cooled after the big bang, atoms, molecules, galaxies, and people were formed, in that order.
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- The Cosmic Microwave Background, is the temperature of about three degrees above absolute zero. That happens to be the temperature of the current expansion..
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- The Universe is isotropic, to the observer the Universe is the same in every direction, so this cosmic microwave background is the same in every direction , everywhere in the universe.
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- It is the haze of photons that permeated space ever since the big bang. When we look farther out with a microwave telescope we see farther back in time. This photon haze thickens and eventually becomes opaque. So the microwave telescope eventually sees the universe as a giant sphere that stops where we can't see any farther.
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- In 1965, two physicists discovered this cosmic microwave background, after first thinking it was pigeon droppings inside their antenna.
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- In 1989, COBE, a cosmic background explorer satellite discovered stunning confirmation that this expansion model existed. The temperature versus wavelength, or frequency, plotted exactly according to the theory. with the absolute temperature being 2.726 degrees centigrade above absolute zero.
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- In 1992, this experiment was repeated with more sensitive instruments. It discovered that although matter was generally distributed evenly, homogeneously, there were clumps of bubbles of galaxies formed by gravitational attraction. These clumps were thought to originated from quantum fluctuations an the microscopic level in the very early universe.
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----------------------- This universe is 25% helium and 73% hydrogen.
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----------------------- All heavier elements were forged inside supernovae, exploding stars.
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- Although the Universe is under no obligation to make sense, students in the pursuit of knowledge are.
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- In 1929 Hubble found the linear relationship that the more distant the galaxy the greater the redshift displayed in its spectral lines. When redshift is plotted versus apparent magnitude the plot is a straight line, indicating cosmic expansion.
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- The Hubble Constant denotes the rate at which the Universe is expanding , it is thought to be 50 kilometers per second per megaparsec. A megaparsec is 3.26 million light years.
So, for every 3.26 million light years we look out into space the galaxies are receding 50 kilometers per second faster. That is 49,306 miles per hour for every million lightyears distance.
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- The deceleration factor measures the rate at which cosmic expansion is slowing down, due to gravitational attraction which is due to the mass inside the universe.
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- The mass density is now thought to average one atom per cubic meter of space.
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- Knowing these numbers precisely would allow calculations to determine if and when the universe would stop expanding and begin collapsing back into itself. Or, if the universe continues to expand forever; a form of heat death, where all the energy would eventually run out, black galaxies would expand endlessly into black expanding space.
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- This formula for the “critical density balancing” between these two fates is called omega:
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- Omega = 2* the deceleration + 2/3*cosmological constant * speed of light squared / the Hubble constant squared.
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- The effect of deceleration is to slowly decrease the Hubble constant. Therefore, it must not be a constant at all. Well it does remain approximately constant over our lifetime so we call it a constant.
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- If the Omega is equal to one and the Hubble constant is 50 then you can calculate the Universe to be 15 billion years old.
- This expanding universe is difficult to measure because of the bubble of galaxies in clusters and super clusters whose gravitational effects pull galaxies in different directions than the direction of expansion. Local galaxies appear to be going 600 kilometers per second in an unrelated direction.
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- Parallax is simple triangulation used to measure distances of close in stars. In 1672 astronomers calculated the orbit of Mars using triangulation.
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- If you know the radius of one planet's orbit you can derive all the others from their orbital periods with Earth's orbit known we can get better parallax calculations
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- By 1900 astronomers had measured the distance to 100 stars.
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- A star's brightness can be determined theoretically from its mass and chemical composition. This is intrinsic brightness or absolute magnitude.
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- If we know that Sirius has an intrinsic brightness, and a similar star is one percent as bright, in observed brightness, then we conclude it is 10 times farther away. The brightness will decrease by the square of the distance.
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- Sirius is 8.6 lightyears away , so the observed star must be 86 lightyears away.
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- Cepheid stars, or pulsating stars, are the next distance indicator into the universe. Cepheid’s are young giant stars the are in an unstable stage in their evolution. The Cepheid star contracts and gets hotter.
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- Heat emanating into its atmosphere ionizes its helium . Helium atoms loose one of their electrons. More heat and energy knocks a second electron off the helium atom. Double ionized helium atoms tend to absorb light. The stars atmosphere then becomes opaque.
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- The opaque atmosphere retains heat and the star gets even hotter. As it gets hotter it expands. As it expands it cools, since its heat energy is spread over a greater area. As helium atoms cool they return to their single ionized state. The atmosphere turns transparent and collapses as the heat and light dissipates. This whole cycle repeats itself every few weeks. This becomes a predictable repeatable cycle.
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- Astronomers can measure the rate of a Cepheid's pulsation and with its color they can determine its intrinsic brightness. Bigger Cepheid’s pulsate more slowly. And , the bigger the star, the brighter it shines.
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- Polaris, the north star , is the nearest Cepheid to Earth and it was determined to be 466 light years from Earth.
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- Cepheid’s have been measured in galaxies as far as 15 million lightyears away. Using the Hubble telescope this has been extended to 60 million lightyears distance. These more recent measurements have put the Hubble constant, rate of universal expansion, at 80 rather that 50 kilometers per second per megaparsec.
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- Supernovae are exploding stars. A supernovae can release more energy in one minute that is released by all the normal stars in the observable universe during the same amount of time. Only one-hundredth of one percent is emitted as visible light. 99% of their energy is not light but is in the form of neutrinos. The temperatures are in the 100 billion degrees.
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- All Type 1a supernovae have similar absolute magnitudes in intrinsic brightness.
Measuring these “standard candles” results in a Hubble constant of 50.
Type I supernovae are dwarfs, they collapse when they gain a critical mass.
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- Type 11 supernovae are giants They collapse when they run out of nuclear fuel at their core. When the fuel runs out they become unstable, the radiation pushing outward no longer is in balance with the gravity pulling inward. They deflate.
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- Reverend Robert Evans in Australia discovered 27 supernovae using the telescope in his backyard. He had an acute visual memory. He could spot an exploding star that was not in that galaxy the last time he looked.
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- In 1977 astronomers discovered that the spectrum of hydrogen, 21 centimeters in wavelength, is blurred, widened by the Doppler shift, related to the speed at which the galaxy is rotating. The rotation speed is related to the galaxy's brightness. This method could measure distances out to 300 million light years. This method is getting a Hubble constant of 70.
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- Gravitational lensing is the next big step in measuring distances. Quasars are young stars and are consequently further away, and further back in time. As the light of a quasar travels toward us across billions of lightyears of space, it may pass to either side of an intervening cluster of galaxies.
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- The warped space surrounding the galaxy cluster can act as a lens such that we get two images of the one quasar. ( Gravitational force is simply the result of objects and light beams pursuing the shortest available path through curved space.)
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- The light traveling around one side of the lens will travel further than the other side, most likely. The quasar is pulsating, with its brightness changing over as little as a month. The difference in light travel can now be measured for the same event. You can now calculate how much longer the path through space is taken by the second path.
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- Measuring the intensity or brightness of light is not the only way to measure distances. Measuring the intensity of cosmic microwave background through galaxies that emit
x-radiation is a newly discovered technique.
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- Intergalactic gas in clusters of galaxies is relatively warm and emits X-rays, consequently microwave background photons are heated up when they pass through the cluster. This results in a hot spot in the background radiation. The more distant galaxy clusters are denser and hotter and make hotter spots . So temperature can be a measure of the distance. In 1991 this technique yielded a Hubble constant of 40 to 50.
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- Still another technique measures the brightness fluctuation as the narrow-field telescope scans across a galaxy. Nearby galaxies can resolve individual stars, their unevenness in brightness as we scan across them is greater. The more distant galaxies show more smoothness as the star light tends to all merger together. So, galaxy brightness fluctuation is a measure of distance. This technique should allow Hubble telescope to go out 500 million lightyears.
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- There is a scientific dictum that claims the simpler of two otherwise comparable hypotheses is to be preferred..
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- Questions: If there are an infinite number of stars occupying an infinite amount of space why is the night sky bright as day with all this starlight? If the space is finite, why hasn't the gravitational force of an infinite number of stars collapsed into a singularity? If centrifugal force is keeping stars from collapsing and space is rotating, then rotating with respect to what? How do forces even propagate through space?
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- In 1915 the Einstein theory of general relativity does away with an need for a force of gravity. Planets and mass follow paths of least resistance through curved space. If space is curved, and the universe is sphere shaped, you could travel infinitely far and never come to the edge of space.
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- Maps or models are always imperfect in that they represent the territory of investigation more economically than does the territory itself, inevitably the model contains less information.
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- The general theory of relativity indicates that space can be mapped only by going to four dimensions. Three dimension Newtonian models do not work completely.
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- In 1882 an astronomer pointed out that Mercury was not behaving strictly according to Newtonian laws. When Einstein added the forth dimension of time the calculations for Mercury's behavior again finally matched observation.
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- In 1854 Georg Reimann created 4-dimensional geometry. Einstein applied Reimann's geometry to the cosmos. When the Earth was flat, 2-dimensional geometry worked fine. But when we discovered the Earth was a sphere, we needed 3-dimensional geometry to explain things. To explain the cosmos we now need 4 dimensions.
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- On this 4-dimensional map light beams form the gridlines. Light beams bend when they pass near massive objects. In 1919 this was observed during a total eclipse. Stars behind the Sun changed positions as the starlight bent passing near the sun. Where Einstein got radical was to claim that actually the light beams are straight lines and that space itself is what is curved.
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- This idea is not intuitive, but observation ranks this theory as among the most accurate theories of physics ever devised. Calculations were validated when gravitational redshift was observed in white dwarf stars. And, when radar signals were bounced off Mercury, Venus and Mars. And when time delays in radio signals coming back from spacecraft Voyager are passing by Saturn.
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- If cosmic matter density is higher than critical density then space is wrapped around the universe, and spherical. If matter density is less, the universe is hyperbolic. If exactly equal to critical density space is flat. Omega is >1, <1, or =1. At the local level we think space is flat, Omega =1. Maybe at the universe level cosmic geometry is curved.
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- With curved space the effects of gravitation is local, but not at a distance. So, gravitational force does not have to travel anywhere or through anything. In Einstein's theory of gravity there is no force. Objects simply respond to the contours of space in their immediate vicinity. Geodesics is the mathematical measurement of curved surfaces, such as the Earth's geography which is a curved surface.
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- Curved space also explains Galileo's discovery that in a vacuum all objects fall at the same rate. Feathers and cannon balls follow the same path of least resistance, geodesics. The path is the same regardless who travels it, or how big it is , or how much it weighs.
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- Maybe we will learn that all forces are geometrical at their root. Maybe a
10-dimensional geometry will explain all the theories to do with matter and energy. Remember matter is only energy that has cooled down, or slowed down enough that we can see it.
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- We know the universe is larger than we can see. We can only see those galaxies that lie close enough to us for their light to have reached us at the present time. This is the "observable universe".
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- In an expanding universe , what's observable is but a fraction of the whole. If the Universe were the size of the Earth, we could only see an Observable Universe the size of a proton.
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- We should be able to count galaxy densities at various distances and measure the curvature of space. The number of galaxies must increase even faster with distance for any given field of view because we are seeing back to an earlier time when the universe was smaller and galaxies were closer together.
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- Blackholes both support general relativity and disagree with it. Inside blackholes the curvature of space becomes infinite. Light can not escape a blackhole.
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- To escape the Earth you need a velocity of about 24,000 miles per hour. The surface of the earth is 3,963 miles above the center of the Earth. If we squeezed the Earth to half that size, 4 G's , we would need an escape velocity of 1.4 times, or 33, 600 miles per hour.
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- If we squeezed the Earth's radius down to 0.35 inches you would need an escape velocity of 186, 000 miles per second ( the velocity of light) At that density the Earth would become a blackhole.
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- Escape velocity depends on both mass and radius. The more massive the object the larger it can be when it becomes a blackhole. The Sun would have a radius of 1.9 miles for it to become a blackhole.
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- The amount of energy in any chunk of matter is equal to its mass times the velocity of light squared. So nothing can have a velocity greater than that of light. As we approach the speed of light the mass increases, distance along the axis of direction shrinks, passage of time slows. The amount of energy to go faster increases. To reach the speed of light the mass would become infinite, length would be zero and time would stop. An impossible situation wouldn't you think.
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- Every healthy star has a balanced diet of nuclear fusion radiating outward from its core and gravity trying to collapse it to a point. Caught in this balance, stars can pulsate. When gravity collapses a little, density grows(compression), heat increases. thermonuclear fusion increases, subatomic particles go faster ( get hotter, the definition of heat), releasing more energy, expanding the core, that thins and cools a bit and starts to contract again with gravity.
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- The star survives as long as it has fuel to burn. The more massive a star the faster it burns ( burn rate is the cube of the mass). A star 10 times bigger than the Sun would burn 1000 times faster. The Sun's burn rate should allow it to survive 10 billion years before it collapses into itself.
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- We think the Sun is middle aged, about 5 billion years old. That more massive star would only live for 10 million years. The star collapses in less that one second when the core shrinks.
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- If its mass is 1.4 times that of the Sun it will become a white dwarf star. It becomes carbon and oxygen with a gas shell about 100 miles in diameter.
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- If its mass is more than 1.4 times solar mass its gravity overwhelms the exclusion principle and electrons are smashed into protons turning them into neutrons. It becomes a neutron star, about 10 miles in diameter, perfectly smooth as a ball bearing.
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- Spinning more than a thousand times per second, rotation velocity increases as they contract, like an ice-skater pulling their arms in. Neutron Star’s magnetic fields emit intense radio waves that strike Earth as “pulsars“.
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- If a star collapses further it becomes a blackhole. Light rays will go into orbit about its mass. It becomes a tiny circle of blackness. Gravitational redshift is a displacement of light toward the red end of the spectrum as it loses energy in its attempt to climb out of the curved space surrounding the blackhole. A blackhole is disembodied mass, mass without matter.
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- The blackholes at the center of galaxies is estimated to be the masses of 100 million suns, even a billion suns. Something that massive should be seen, but, the source of the gravitational force whirling those stars around is massive, small and black. Yet, we can't see it.
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- The law of entropy says that unless work is done to prevent it, all systems tend toward increasing disorder, or greater entropy. Entropy is disorder over time. Missing information over time. Entropy is randomness. The less entropy there is in a system the more information available.
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- All work involves a certain irreducible increase in entropy. For a machine to do work it must increase entropy.. Reducing entropy takes work. Information tends always to decrease.
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- A system left to itself will tend to a state of maximum entropy.
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- The indeterminacy principle says that subatomic particles do not have definitive positions in space and time , rather, their locations can be specified only in terms of probabilities. Steven Hawkings uses this principle to show that particles can boil out of a blackhole, when other theories say nothing escapes a black hole.
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- Everything is made of curved space. Matter is energy.
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- If an atoms nucleus were a golf ball the outermost electrons would lie two miles away. Atoms like galaxies are mostly cavernous space. What feels solid to our hand is the atoms in the object repelling the atoms in our hand. Matter is energy.
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- In 1950 scientists determined that the big bang could not have made anything heavier than lithium.
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- In 1948 scientists calculated the temperature of the universe to be 5 degrees Kelvin. Today's COBE satellite, Cosmic Background Explorer, measures it to be 2.726 degrees, and that is accurate to within 0.004 degrees. One of the most accurate measurements ever made is on something that is 10 billion lightyears away.
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- Our Sun burns 600 million tons of hydrogen every second, turning 4 million tons into energy. To accomplish this two protons fuse forming deuterium (one proton, one neutron) releasing a positron and neutrino. The positron hits an electron, the annihilation creates a gamma ray.
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- The deuterium fuses with hydrogen forming helium-3, releasing more gamma rays. Two helium-3 nuclei fuse into helium-4 plus two protons. The two hydrogen nuclei (protons) and one helium-4 nucleus weigh 0.7 % less than the original nuclei. That's the mass that was converted into energy. That's the 4 million tons per second of energy that the Sun shines.
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- Baryons are protons and neutrons, what we call ordinary matter. Most of the matter in the universe is not made of baryons, not ordinary matter. In fact, 99% of the universe is non-baryonic. That is to say everything we can see that constitutes our universe constitutes only 1% of the matter in the cosmos.
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- Gravitational force on planets diminishes by the square of their distance from the Sun. The inner planets orbit faster. The Earth 30 kilometers per second, Jupiter, five times farther out, orbits at 13 kilometers per second.
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- The Sun is 99% of the mass in our solar system.
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- Our Milky Way galaxy is one of 26 galaxies on our Local Group. Our local group is traveling 630 kilometers per second in an unusual direction, toward the constellation Centaurs.
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- The Sun is traveling 220 kilometers per second around the Milky Way center. To pull the Local Group of galaxies in this unusual direction it would need to be pulled by a mass of 50,000 galaxies that we can not see.
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- Over a 100 million lightyears distance there is lots of structure with galaxies, clusters of galaxies, super clusters and vast voids in between. Once we look over 1,000 million lightyears distance the universe appears more homogeneous and isotropic ( the same in all directions) . To date astronomers have probed 6 billion lightyears in both directions.
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- A chicken is an egg's way of making another egg.. Galaxies and universes must have some type of an evolution too. Can blackholes produce another galaxy?
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- The Earth has had 7 global die outs which can be dated to coincide with comet impacts. 65 million years ago , between the Cretaceous and Tertiary periods a comet hit the Yucatan peninsula creating a 100 mile diameter crater.
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- "Gas and dust" to "gas and dust". The Earth began as a disk of gas and dust orbiting the Sun. It started as a grain of dust. These grains started sticking together by electrostatic force and then by slamming into each other traveling at orbital speeds.
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- Once Earth was a mile in diameter gravitational forces started pulling more pieces together. These escalated into titanic collisions. As mass grew higher escape velocities were needed for collision material to escape. Scientists estimate this whole process to a few hundred miles in diameter took less that 10,000 years.
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- After that it took elliptical orbits to promote further collisions, 10 million years for these to subside. Earth's oldest rocks are 3.8 billion years old. Bombardments from space continued for 100 thousand years. It is believe the Earth's water was brought here by the bombardment of comets.
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- Most planets rotate counterclockwise, viewed from the north, they spin west to east. Except Venus and Pluto spin clockwise. Uranus is tilted more than 90 degrees, pole to plane of orbit.
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- These unusual orbits were caused by massive collisions during planetary formation. The moon around Earth was created by a big splash when the Earth was red hot, molten crust. That's why the moon lacks iron. Iron was at the Earth's core and not in its crust to get blown away..
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- If we lived on a planet circling Alpha Centauri, our nearest star, 4.22 lightyears, our current technology would not allow us to see our Sun's planets. In 1983 astronomers did discover a disk around Vega, 26 lightyears away. In 1995 measuring variations in a Sun's motion as little as 3 miles per hour, astronomers found evidence of planets orbiting a star in Pegasi. In 1996 evidence of planets were found in Virginis, Virgo near Arcturus, and Ursae Majoris. See Reviews about Exoplanets as thousands more have since been discovered.
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- Supernovae, exploding stars occur 3 times per century in an average galaxy. That equates to one per second in the observable universe.
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- Meterorites that are found on Earth are 4.56 billion years old. The Sun is 5 billion years old.
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- Hubble can see galaxies 4 billion times fainter that the human eye can see., 8 billion light years away and 8 billion years back in time.
- Evolution is creative and creativity is unpredictable.
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- Age of the Earth were a calendar year vertebrates evolved on November 21, primates on Christmas day and Homo Sapiens only 3.5 minutes before midnight on New Year's Eve.
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- From 1920 to 1970 field theory was in. Now string theory has promise. If correct, then all subatomic particles are blackholes. 10-dimensioal mathematics is used to model this mathematical universe.
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- Does reliability in the past constitute a warranty in the future?
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- Distrust any concept you can not explain to your kids.
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- The optimist proclaims that we live in the best of all possible worlds, the pessimist fears this is true.
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- The weak nuclear force is 10,000,000,000,000,000,000,000,000,000 times stronger than gravity.. Electromagnetism is 100,000,000,000 times stronger than that. And, the strong nuclear force is 100 times stronger than electromagnetism. What does it take to explain all this?
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- There is no obligation for the universe to be logical, however it is an obligation for students of knowledge to be logical or the teachers won’t give you good grades.
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- April 29, 2019 342
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