Friday, August 2, 2019

COSMOLOGICAL CONSTANT - how fast is the Universe expanding

-   2428  -  COSMOLOGICAL  CONSTANT -  -  The Cosmological Constant was invented by Albert Einstein.  When he was thinking about gravity and the birth of the Universe, he could not see how , if gravity were the only force working over long distances, the Universe would not stop expanding and begin contracting into a “ Big Crunch”.
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----------------------- 2428  -  COSMOLOGICAL  CONSTANT -  how fast is the universe expanding?
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-   At the time of Einstein‘s theories, in  the early 1900’s, the observed Universe appeared to be “static”, neither expanding not contracting.  Albert thought that another force had to be present to prevent gravity from stopping the expansion of the Universe and sending it into reverse.
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-------------------  Gravity = - m*M*G / R^2
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-  The force of gravity is equal to the product of the two masses, m and M,  and inversely to the square of the distance between them, R.  G is the Gravitational Constant that Isaac Newton discovered and its value depends on the units of measurement.
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-------------------  G  =  6.67 * 10^-11  meters^3 / Kilogram * second^2
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-  Albert simply invented another force to put into his equations and called it the “Cosmological Constant“.
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------------------  Force in the Universe  =  - m*M*G / R^2 + Lambda * m*R
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-  The Greek letter Lambda is the symbol for the Cosmological Constant.   The product of Lambda*mass*distance defines the anti-gravity force responsible for the expansion of the Universe counteracting gravity.  Albert arbitrarily set the force of expansion exactly equal to the force of gravity so the two balanced and the Universe became static.
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-  A few years later Edwin Hubble discovered that the Universe was expanding.  He discovered that galaxies farther away were expanding faster than galaxies closer to us.  He determined the expansion to be a direct relationship between the velocity of expansion and the distance from us. 
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-----------------------  The ratio became “Hubble’s Constant” = Ho = velocity / distance:
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-----------------------  Ho  =  150,400 miles per hour per mega parsec
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-----------------------  Ho  =  .046107 miles per hour per lightyear
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-  So, if a galaxy was a million light years away it would have a receding velocity of 46,107 miles per hour.
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-  The Universe was not static, it is expanding.  The repulsive force that is opposing gravity was not zero it is some positive number.  Most recent discoveries measuring supernova in these far away galaxies have determined that the Universe is not only expanding its rate of expansion is accelerating. 
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-  The conclusion is that the fate of the Universe is to expand forever into a “Big Chill”.  For the first 8.2 billion years matter was dominate and gravity was slowing the Universe expansion down.  However, 5.5 billion years ago the reverse occurred and the repulsive force of vacuum energy took over.
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-   As the Universe expands matter becomes rarefied and the gravitational forces become less and less.  The “vacuum energy of space“, that is the “Cosmological Constant“, does not change as the Universe expands.  It becomes the dominate force and the recession velocity of the galaxies grows ever larger.
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-  To explain the repulsive force the vacuum of space must contain some intrinsic fundamental energy.  It is called vacuum energy, and Dark Energy, because we do not know what causes it.  It just must exist to explain what we observe.
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-  Measurements made on the expansion rate of the Universe verses gravity determine the value of the Cosmological Constant.  It must be very, very small, very nearly zero but not quite zero.
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-   The value of Lambda is 1.9 * 10^-29 grams / cm^3.  Planck units are based on natural constants and not man’s defined standard units.   Expressed in Planck Units Lambda is 2 * 10^-120 units.  That is a decimal point followed be 119 zeros then a 2.  That is so close to zero, but it is not zero, it is just very, very small. 
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-  The amazing point is that if it were just 100 times larger, a decimal point followed by 117 zeros then a 2,  the Universe would change and life as we know could not have evolved.  The Universe would have expanded too fast.  On the other hand, if the Constant was even a little bit smaller, a decimal point followed by 122 zeros and a 2, then life would not exist because the galaxies would never have a chance to cool and form stars and planets after the Big Bang.
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-  It appears that  the Cosmological Constant is very finely tuned and the expansion rate of the Universe is “just right” to allow life to have formed at this time.  “There is no reality without observers.”  The natural constants appear to  be finely tuned to allow life to be here and observers to make these inquiries.   
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-  Of course if it were any other way we would not be here so the natural constants have to be what the are.  But why?  No equation can derive these numbers.  Scientists can measure them to many decimal places but they have no idea why they are what they are.
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-  The Cosmological Constant is one of the most dramatic examples of fine tuning of natural constants.  But, they are dozens more natural constants fine tuned for life as well.
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- Some of these natural constants include:
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---------------- Speed of Light  =  c  =  2.99792458 * 10^8 meters / second
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----------------  Planck Constant  =  h  =  6.626076 * 10^-34 joule * seconds
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---------------  Gravitational Constant  =  G  =  6.67259 *10^-11 meters^3/ kilogram*sec^2
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---------------  Boltzman Constant  =  k  =  8.617385 * 10^-5 electron volts / Kelvin
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---------------  Electron Charge  =  e  =  1.60217733 * 10^-19 coulombs
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---------------  Electron Mass  =  Me  =  9.193897 * 10^-31 kilograms
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---------------  Proton Mass  =  Mp  =  16,726.231 * 10^-31 kilograms
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---------------  Avogado’s Number  =  N  =  6.0221367 * 10^23 / mole
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-  There are dozens more natural constants expressed as quantities in units defined by scientists, such as kilograms, seconds, meters, etc.  There is a system of units based on natural constants independent of any of man’s definitions or standards. 

-  These are Planck Units.  They are defined using the Gravitational Constant, the speed of light and the Planck Constant of 6.626076 * 10^-34 joule* seconds set to equal 1.  Under these unit’s the Planck length is equal to 1.61599 *10^-35 meters.  The Planck length squared is equal to G * h / 2*pi*c^3.
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-  Again, physicists have no clue why these natural constants are the size they are but if any of them were a little bit bigger or a little bit smaller our Universe would change to the degree that life as we know it would not exist.  We would not be here to observe the Universe or measure these constants.  This fact is known as the Anthropic Principle.
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-  Some of the scientists to credit for this insight into our Universe:
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(1)   Alexander Friedman ( 1888 - 1925) was a Russian mathematician.  During WWI he was on the Russian front with the Russian air force.  In 1922 he was the first to recognize that Einstein’s equation was an impossible balance.  Just the slightest fluctuation would cause the Universe to expand or contract, in no way could it be balanced at static.  He adjusted Einstein’s Cosmological Constant so the Universe was expanding.  He proposed that  in the distant past  the Universe started at a single point with a  Big Bang.  He died of typhoid fever while still in his thirties.
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(2)  Abbe Georges Lemaitre (1894 - 1966) was a Belgian astronomer.  He served in WWI in the Belgian army as an artillery officer.  He became an ordained priest in  1922.  In 1927 with a degree in astrophysics he developed the theory of an expanding Universe and extrapolated backwards in time to where all of matter first exploded in a Big Bang, billions of years ago.
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(3)  George Gamow (1904 - 1968) was a Russian-American physicist who studied under Friedmann.  In 1948 he worked out a method by which the explosion of Lemaitre’e cosmic egg would lead to the formation of all the elements in a very short time.  Gamow also predicted that there would exist the Cosmic Microwave Background radiation left over from the Big Bang.  The CMB radiation was not detected until 1964

-  August 2, 2019                                                                                   713                                                                                                                                                         
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