Alan Guth has described the inflationary universe as the "ultimate free lunch": new universes, similar to our own, are continually produced in a vast inflating background.This is based of of Guth's actual quote coupled with the grand view of what may be going on:
It is said that there’s no such thing as a free lunch. But the universe is the ultimate free lunch.”
Do we understand inflation enough to believe it is free? And am I correct in remembering that I read somewhere that the net energy of the Universe is 0?
ReplyDeleteStan, if would be hard to know what the net energy in the universe is. We know it is infinite at every point, but since experiments only measure energy differences this is okay. The infinite part is often called the zero point energy, but it is real and is possibly the vacuum energy driving the expansion of the universe. It is also responsible for the casimir effect.
ReplyDeleteIn any quantum mechanical system you can't have zero energy by hisenberg's uncertainty principle. Just when you think you have removed all the energy and know it is zero, think again. There are quantum fluctuations that keep it uncertain. This is not a violation of conservation of energy.
You can think of the zero point energy as this: virtual particles popping in and out of the vacuume in such a way that energy is conserved.
Now, I admit that it could turn out to be zero when after the whole universe is summed over. But it is hard to *know*.
Stan,
ReplyDeleteAs I said on anthor blog, regarding the infinite zero point energy at every point:
"If you want to see the exact calculation go to Google Book and search for the quantum field theory book by peskin and schroeder. Under contents click on “Klien Gordon Field”. This is chapter 2 starting on page 13 of the book. The relevant equations as 2.5 and 2.31. All the equations around these equations are the derivation.
After 2.31 the authors discuss what I have said, the energy, represented as the Hamiltonian, is infinite. The say it sounds disturbing but since we can only measure energy differences things are fine and if you remove the “zero point energy” contribution what is left is something we can measure. They then admit they will come back to places such infinite energy is useful. They are partly referring here to things like vacuum energy/dark energy in cosmology though there are more places this stuff seems to rear its head."
Also add the casimir effect: From the wikipedia: "Although the Casimir effect can be expressed in terms of virtual particles interacting with the objects, it is best described and more easily calculated in terms of the zero-point energy of a quantized field in the intervening space between the objects."
Nick is actually working on an machine that creates en event horizon that traps these virtual particles before they can annihilate each other going back to vacuum and extracting their energy to provide the earth with unlimited renewable energy.
ReplyDeleteHoes that machine coming Nick? :)
Joe,
ReplyDeleteIt's coming along well. I just need a billion dollars or so in additional funding. :)
Stan, as for the "freeness" of the lunch. If inflation is correct and did none other than create our universe out of some small patch of space, it would still be like a free lunch.
ReplyDeleteWe get galaxies, clusters, stars, elements and everything else in the universe from that one little patch+inflation.
But it is true, once we learn more Guth might have to retract his statement. :)
Stan, sorry to beat a dead horse, but on that casimir wikipedia page there is this too:
ReplyDelete"The vacuum has, implicitly, all of the properties that a particle may have: spin, or polarization in the case of light, energy, and so on. On average, all of these properties cancel out: the vacuum is, after all, "empty" in this sense. One important exception is the vacuum energy or the vacuum expectation value of the energy.
Summing over all possible oscillators at all points in space gives an infinite quantity. To remove this infinity, one may argue that only differences in energy are physically measurable; this argument is the underpinning of the theory of renormalization. In all practical calculations, this is how the infinity is always handled. In a deeper sense, however, renormalization is unsatisfying, and the removal of this infinity presents a challenge in the search for a Theory of Everything. Currently there is no compelling explanation for how this infinity should be treated as essentially zero; a non-zero value is essentially the cosmological constant and any large value causes trouble in cosmology."
Okay, I'm done.
Hey this stuff isn't in my 'Quantum Physics for Dummies' book. No really, that book does exist and I have it! Haven't read it though. It's really a trophy to my "Some things just aren't for dummies" philosophy.
ReplyDeleteStan, I've flipped through that book and it is actually really good. (For what it is supposed to do.) There is also a string theory for dummies book.
ReplyDeleteIf you could actually read such books you would know, at least on a basic level, the real stuff, not just some discovery channel watered down version. It's not watered down at all, if I remember right, just only touches the basics that can be done without too much prerequisite knowledge. (As you said though, you can't get far in QFT without some technical knowledge, even on a basic level.)
When the first page I flipped to had Calculus and Differential Equations, I got spooked. I have taken those courses, but I gleefully abandoned that part of my education. =:)
ReplyDelete