I have asked this question before, and got an answer that satisfied me (at least it did then), however, since then MANY famous scientists disagree with the reasoning of the answer making me think that I'm missing something.
Many scientists including Hawking, Krauss, etc contend that universe came to be through a quantum fluctuation event. Now I'm not a physicist but from what I understand, in order for a quantum fluctuation of this energy magnitude to persist, it requires the total energy content of the universe to equal zero under this premise:
A gravitational field has negative energy. Matter has positive energy. The two values cancel out provided the universe is completely flat.
Okay if that's the case, then the only possible source of the negative energy is a gravitational field. How do we get a gravitational field without the universe already existing in some form? As I said I asked this once before, and was told by a physicist that quantum fluctuations could NOT explain the origin of our universe. Yet Hawking, Krauss, etc persist in the idea that they can.
Can anybody shed some light on this in layman's terms?
2013-03-05T17:07:23Z
Satan Claws - While a lot of what you said escapes me, I do get the overall point. I guess what I didn't emphasize is that the HUP places a limit on the time that a quantum fluctuation can persist. The greater the energy of the fluctuation, the shorter the time that it may last. It is said that the amount of energy in the universe, paired with the fact that it still persists requires the overall energy to equal zero otherwise the HUP would not permit the persistence of the universe. It's not that the gravitational field is required for all quantum fluctuations, but for one containing as much energy as the universe contains, it must equal zero. Therefore it requires negative energy from a gravitational field, or did I get that wrong? Again, I'm a layman, not a scientist and I admit this above my pay grade so to speak.
Satan Claws2013-03-05T15:18:38Z
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In QM, you can learn about something called "second quantization" when studying systems of identical particles. Naively, it makes sense to talk about quantization of particles because you don't have half a particle, or 2.35 particles; you have integer numbers, and there is a discretization on the measurable quantity of "number of particles" in a system. So, this second quantization technique introduces two quantum operators, the "destruction operator" which decreases the number of particles of a system by one unit and the "creation operator" which increases the number of particles of a system by one unit. For example, to have N particles in a system, that corresponds to applying the construction operator N times to the vacuum state (which, by definition, is the state of a system with zero particles). By definition, applying the destruction operator on a vacuum state gives the vacuum state again, because the number of particles in the vacuum state is already zero. BTW, in QM, "first quantization" comes from the kind of quantization people're "used" to -- giving stuff like levels of energy, commutation relations like Heisenberg's uncertainty relations, etc. Something important you should note is that there are no considerations of external fields involved here: it works with "free particles", i.e. no external potentials, or with particles in a box (but which are free inside the box). Anyway, the second quantization stuff becomes important when you talk about quantum statistical physics -- where you study the properties of systems that are parity even (doesn't change the sign of the state function) or parity odd (changes the sign of the state function) when switching two identical particles; parity even (symmetric) systems under such transformations are bosons, anti-symmetric systems are fermions. Whole sets of properties come from these considerations, and are used in things like what happens to a star (which is a bunch of fermions).
The second thing you should keep in mind is that, for physicists, it's not so much the state of the system that is interesting, but rather the relations of quantities -- or rather, the operators that represent those quantities. When you write the Schroedinger equation (which is non-relativistic), or the Klein-Gordon equation (relativistic but spin 0, so only good for bosons), or the Dirac equation (relativistic, spin 1/2 i.e. good for fermions). More specifically, physicists talk about observables -- i.e. operators which have proper values that correspond to the values of the physical quantities we measure. When you write the (time-independent) Schroedinger equation, the nabla^2 operator is the linear momentum squared, and divided by the mass gives the kinetic energy operator; the potential in there is really an operator (whatever it is); and the energy on the right is really the proper value (or "eigenvalue" as they call, "eigen" comes from German) of the total energy operator (kinetic energy operator plus potential energy operator) on the other side of the equal sign. The state of the system is of little importance there; it is what it is, and it'll depend on the initial conditions. The important part is the relations between the operators. (An operator is a mathematical entity which gives a function when applied to a function; it's the analog of a function, like the sine or the logarithm, which is an entity that transforms a number it to another number, or a vector when you apply it to a vector.) The physics of the problem is in the operators. Those are the symbols in the Schroedinger, Klein-Gordon, Dirac, and all other field equations. Even the Maxwell equations can be written as operator equations, applied to a "function" which is really the electromagnetic field (the solution to the Maxwell equations). In fact, quantum electrodynamics *needs* the electromagnetic field in there to keep the equation for the electron "straight" (more specifically, maintaining the same relations between operators when making local transformations of coordinate systems); the Maxwell equations show up (in a very weird and compact form) in the QED field equation.
I'm not too sure on how cosmologists work there, but I suspect that they use some form of second quantization. They start with an initial condition (the vacuum, i.e. no particles) and try to come up with an equation (technically not really the equation, but rather a function called "lagrangian", which is the solution to the Euler-Lagrange equation) which RESEMBLES what you're (and they're) looking for: a toy universe with a gravitational field and a scalar field that can give mass to particles. There is some educated guessing, but it really amounts to this: http://youtu.be/b240PGCMwV0
To be trouble-free, i don't have an entire ton of expertise on physics yet in my existence, however so some distance as i'm worried, thought opens the belief for all doorways of possibilities. as an occasion, many scientist think of that at final, there will be a "enormous Crunch" the place, as you are able to think of from the word, is the place the gravity from each and all the planets will ultimately have each and all the planets come decrease back to the element at which each little thing already originated at. the undertaking with that however is that planets are nevertheless traveling so some distance faraway from one yet another that the purple shift does not appear like it quite is going to pass away quickly, which ability if this have been to ensue, you may desire a great form of time, and that i propose plenty. however i'm getting off undertaking. i think of a thank you to seem at it quite is the actuality which you will no longer unavoidably want mass with the intention to reason gravity. I say this because of the forged previous E = mc^2 which in certainty is: E^2 = (mc^2)^2 + (laptop)^2 see because of this all of us comprehend mass has capability, and a great form of it. however this formulation additionally debts for the conversion of organic capability into mass. An occasion of capability becoming gravity is a Kugelblitz. A kugelblitz is a black hollow shaped whilst capability has the wave length of the planck length, this is the smallest achievable length interior the universe. Black hollow's have substantial gravity, so subsequently, you does no longer unavoidably want mass, yet you may desire capability, which in accordance to scientist, each and all the capability of the universe grow to be centred all the way down to a single element, so subsequently there might additionally must be a good stress of gravity
Sure ... It is impossible to have a quantum fluctuation in space/time before time and space began. Space/time was supposedly created by the big bang. And that means there can not have been any events prior to the big bang.
That means : 1 Hawking and Krauss are wrong or ... 2 Our idea about the big bang are in error in some fundamental way
It is a paradox -- because we are faced by the reality of the universe existing.
The latest thing I've heard on this is that when the universe becomes rarefied enough (it's expansion is accelerating) there will be another quantum fluctuation event. It's based on new findings about the mass of the Higgs Boson. http://www.escapistmagazine.com/news/view/122212-Higgs-Boson-Points-to-End-of-Whole-Universe This may be something that has been repeating for an infinite amount of time.
You have come a long way. You understand the basics very well. The "no universe" or "nothing" is unstable. It is so unstable that is actually explodes in a "Big Bang". It is the ACCELERATION of this explosion that creates gravity as well as the mass. Acceleration and gravity are related. Check out the Unruh Effect for how acceleration creates the mass. Check out "The Origin of the Universe - Case Closed" for more. Good luck in your search.