Most cosmologists agree we are unlikely to understand the big bang without a quantum theory of gravity. The leading candidates for this are string theory, loop quantum gravity and Horava-Lifshitz gravity. We see again and again in all these different approaches the same result; the hourglass universe i.e a period of contraction mirroring a period of expansion. This clearly violates the BGV theorem. Don’t believe me, ask Aron Wall, here are his words:

“Carroll’s secondary point that the assumptions of the theorem might not hold seems even more devastating. It says that there must be a beginning if the universe is always expanding. So maybe have it contract first, and then expand. That’s an easy way around the BGV theorem, and (as Carroll points out) there are a number of models like that. On this point I agree with Carroll that the BGV theorem is not by itself particularly strong evidence for a beginning.” ]]>

“What causes the universe to pop out of nothing? No cause is needed.”

The theory that the universe can originate from nothing has been critiqued in the following two links:

1) https://sekharpal.wordpress.com/2015/10/23/a-fundamental-flaw-in-the-thesis-a-universe-from-nothing-part-I/

2) https://sekharpal.wordpress.com/2015/10/23/a-fundamental-flaw-in-the-thesis-a-universe-from-nothing-part-II/

Newtonian gravity: zero energy = Einstein-de Sitter

General relativity: zero energy = closed universe.

And that’s if it makes sense to talk about total energy at all in GR.

]]>*The energy of the gravitational field is negative;17 it is conceivable that this negative energy could compensate for the positive energy of matter, making the total energy of the cosmos equal to zero. In fact, this is precisely what happens in a closed universe, in which the space closes on itself, like the surface of a sphere. It follows from the laws of general relativity that the total energy of such a universe is necessarily equal to zero.*

Whether or not this argument is relevant, one often hears it, but usually with the example of the Einstein-de Sitter universe, not a spatially closed universe. What am I missing?

]]>Indeed. Even if energy conservation is necessary in the creation of the universe, it is certainly not sufficient. Also, energy doesn’t seem to be conserved in cosmology anyway, so the whole stuff about the kinetic and potential energy balancing out is a red herring.

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