On Thursday, January 16, 2020 at 6:06:40 AM UTC-7, John Clark wrote: > > On Wed, Jan 15, 2020 at 6:54 PM Alan Grayson <[email protected] > <javascript:>> wrote: > > >> Already about 74% of the matter/energy in our universe is in the form >>> of Dark Energy, and as time progresses that percentage can only increase >>> and we'll get closer and closer to a pure de Sitter universe. That's >>> because the Cosmological Constant is a property of empty space, so as the >>> accelerating universe creates more space it also creates more Dark Energy, >>> however the total amount of matter (both regular and dark) remains fixed. >>> >> >> *> Why does the total amount of matter, both regular and dark, remain >> fixed as the universe expands? AG* > > > The simple answer is in General Relativity there is a mechanism for > creating new space but not for creating new matter. >
*What theory do we rely on to explain the emergence of matter, regular and/or dark? AG* > The Cosmological Constant is the energy that is always inherent in space > even when it has no matter in it. General Relativity says that this vacuum > energy will cause space to accelerate, that is to say more space will be > created, so unlike the matter in it vacuum energy will not become diluted > as the universe expands but will remain constant in both space and time. > According to General Relativity the curvature of Spacetime (NOT the > curvature of space) is determined by the energy and momentum in it, and as > Sean Carroll says "*the manifestation of spacetime curvature is simply > the fact that space is expanding*". And if vacuum energy is constant then > the spacetime curvature (NOT spatial curvature) of the universe is constant > so the universe is accelerating at a fixed rate, that is to say it always > takes a fixed amount of time to double in size. > > General Relativity allows for the existence of vacuum energy but does not > insist on it, Einstein's theory has no way to calculate it's value, it > could be anything even zero and can only be determined by observation. For > many years astronomers thought the value was indeed zero and so they could > forget about it, but then in the late 1990's they found that the universe > was accelerating and the vacuum energy density consistent with this was > 6*10^-10 joules per cubic meter. > > Curiously unlike General Relativity with Quantum Mechanics you CAN > calculate the value of vacuum energy, however when you do so you find it is > in error by a factor of 10^120; it's been called the worst discrepancy > between theory and observation in the entire history of science. So if the > goal is to find a Theory Of Everything maybe people should leave General > Relativity alone and monkey around with Quantum Mechanics rather than the > reverse, it might be worth a try. > > By the way, we don't know for sure that vacuum energy is the cause of Dark > Energy but it seems like the best guess at the moment. > > John K Clark > > -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/614b1b82-a0dc-44b6-82db-a87f97383b09%40googlegroups.com.
