Science lesson for the day
Posted by aogThursday, 22 January 2004 at 10:22 TrackBack Ping URL

Orrin Judd asks

at the moment of the Big Bang who was the energy borrowed from?

in regard to my comments on “virtual particles and the Heisenberg Uncertainty Principle”.

It’s an interesting question. According to some schools of cosmology, the net energy of the universe is zero. Therefore there’s no need to borrow energy for the universe as a whole, although one might need a little bit to get the process started. This is one of the attractions of a flat universe, which is the result of many models where the net energy of the universe is exactly zero. That would be in many ways the most elegant solution, but reality doesn’t always oblige us in that way.

Comments — Formatting by Textile
oj Friday, 23 January 2004 at 21:07

Where are the Stellar Contestoga Wagon companies?

pj Saturday, 24 January 2004 at 17:25

This article is a very misleading rendition of the inflationary cosmology. Inflationary cosmology treats our universe as a sort of “bubble” in a larger space — call it the “multiverse” — which was in a meta-stable state. The bubble itself began as a quantum fluctuation in the multiverse; the multiverse is unstable to such bubbles, in that as soon as they appear they “inflate,” sucking in energy from the multiverse. Once bubble reaches a certain positive energy — that sufficient to make omega=1 — it becomes causally disconnected from the multiverse, at which the bubble is a standalone “universe.” However, there can be many such universes in the multiverse. All these universes are causally disconnected from one another. Each has positive energy.

You can see in his dropping-the-ball analogy that the idea of “negative energy” comes only from defining the metastable state of the multiverse as one of “zero energy,” so that when it decays to a lower-energy state as it transfers energy into the bubble it acquires “negative energy.” But the only rational definition of “zero energy” in physics is the ground state, and the multiverse is not in its ground state in the inflationary cosmology.

Annoying Old Guy Sunday, 25 January 2004 at 13:27


Not all inflationary theories posit a multi-verse. I’m not a fan of the “zero-energy” cosmologies, but I certainly understand the attraction. In contrast, the meta-stable multi-verse just rubs me the wrong way. Where did that come from? Why hasn’t it decayed? Why just one step up from the ground state? The beauty of the zero-energy cosmology is that it works even from the ground state.

pj Thursday, 29 January 2004 at 17:21

AOG - The “zero-energy” label means nothing, the first time it’s applied — the location of “zero” is arbitrary. All inflationary cosmologies depend on the energy in the universe being taken from what’s outside the universe. We don’t know if there is a ground state to the multiverse, or what state the multiverse was created in, so we can’t guess how many universes had to be created before the multiverse reached its ground state. It could be one, or many.

If the state before the universe was already the ground state, then the universe could not have arisen — there would have been no decay energy released into the universe when it formed, and we’d have a universe with no particles, matter, or energy.

aog Friday, 30 January 2004 at 08:47

Hmmm. I haven’t seen that requirement in my readings. The cited article is just something I found via Google when I was looking for a link, not what I’m basing my claims on. My understanding has been that the point of the zero energy models was that didn’t require energy to bleed in from “outside”.

End of Discussion