- 3543 - - DARK ENERGY - expanding the universe? Astronomers today believe that ¾ths of the Universe is spread evenly throughout space. It may even be space itself? The Universe’s expansion is speeding up. And, we know that it takes energy to accelerate something. Astronomers do not know where this energy comes from. So, we just give it a name, “Dark Energy“. But, if it is ¾ths of all the mass-energy in the Universe it must be pretty important.
--------------------- 3543 - DARK ENERGY - expanding the universe?
- “Dark Matter” is another 20% of all the mass-energy in the Universe. It is affected by gravity and is believed to be what holds all the galaxies together. Dark Matter interacts with gravity but does not interact with electromagnetic energy.
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- “Ordinary Matter“, the remaining 5% of the Universe, does interact with electromagnetic energy. Electromagnetic Energy is everything we see and touch. It is only 5% of what is out there but it too is pretty important since it is everything we know.
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- The other 95% is Dark Energy and Dark Matter that we do not know. What we think is that Dark Matter is what holds all matter together through gravitational attraction. And, that Dark Energy it trying to pull it apart. Over the last 5 billion years the evidence says that Dark Energy is winning. We are just along for the ride.
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- Dark Energy is not predicted by any physics we understand. Obviously, we need to discover some new physics.
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-------------- There are 3 theories in the works:
-------------- (1) The “Cosmological Constant” which is a factor added to Einstein’s equation for the expansion of the Universe that puts a uniform, intrinsic, property in space. Originally Einstein added this fudge factor to make his equations give a static Universe. Today the constant is added differently to add a factor to his equations that expands the Universe into infinity.
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--------------- (2) “Quintessence“, which is an energy field that fills space like a fog, or like a magnetic field. This could be the same energy field that created Cosmic Inflation seconds after the Big Bang.
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---------------- (3) It could be that Dark Energy is an illusion to us observers. We assume the laws of gravity are the same everywhere and always. But, it could be that the conditions of gravity are changing at , or over, great distances. This is the theory of “modified gravity“.
--------------- (4) None of the above.
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- Astronomers came upon the accelerating Universe theory by studying White Dwarf originating supernovae ( called Type 1a supernova). These type supernovae release about the same energy each. The brightness of this energy being the same also can be used to calculate the distance of the supernovae.
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- The dimmer the supernova the farther away it is. The redshift of this light is the amount the wavelengths are stretched and therefore how long the Universe has been expanding during its travels. By looking over a broad range of redshifts astronomers conclude that the expansion rate has varied.
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- About 5 billion years ago instead of slowing down it began speeding up. Dark Energy became dominate over Dark Matter and the Universe started expanding faster and faster.
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- One major variable in this data is the brightness of White Dwarf Supernovae. Is it truly a “Standard Candle” that can be relied upon for intrinsic brightness. We know that the earlier stars did not have the heavy elements. They were created later in other supernovae explosions.
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- Later stars would explode with heavy elements in their makeup. Does this change their intrinsic brightness? If White Dwarf supernovae brightness are not always the same their distance calculations would be in error. If the distances are wrong maybe the expansion theory is wrong too.
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- Another scale astronomers are trying to use is the physical scale of the distribution of galaxies. This scale was set by the shockwaves traveling through the early Universe’s expansion.
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- If astronomers can measure the redshifts of a large number of galaxies maybe they can better define the distances between the galaxies. Once this scale is understood we can determine if the scale is expanding with time. To date astronomers have enough data for 4% precision. They want better precision, but, so far, their data agrees with the Type 1a supernovae data.
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- We always need more data. Astronomers are stuck with improving the precision of their measurements until they loose interest. Right now they are interested.
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- Dark Energy happens to by the biggest puzzle in all of physics and astronomy. Stay tuned.
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April 15, 2022 DARK ENERGY 1147 3543
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--------------------- --- Friday, April 15, 2022 ----------------------------------
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