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bapowell
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Who cares? What does this have to do with the thread. Physics is an empirical science. Last I checked, philosophy is not.yoda jedi said:Physics is rooted on Philosophy.
Who cares? What does this have to do with the thread. Physics is an empirical science. Last I checked, philosophy is not.yoda jedi said:Physics is rooted on Philosophy.
This is quite misleading, or perhaps I'm misunderstanding you. Matter was indeed around in the earliest epochs -- the fundamental matter fields (electrons, quarks, etc) and the gauge fields were both in exist concurrently. Do you mean that it was only until the universe cooled sufficiently for matter/antimatter to fall out of equilibrium with the radiation?DaveC426913 said:In the earliest epochs, the universe was far, far too hot for matter to exist at all.
bapowell said:This is quite misleading, or perhaps I'm misunderstanding you. Matter was indeed around in the earliest epochs -- the fundamental matter fields (electrons, quarks, etc) and the gauge fields were both in exist concurrently. Do you mean that it was only until the universe cooled sufficiently for matter/antimatter to fall out of equilibrium with the radiation?
bapowell said:If you have inflation, then when it ends and the universe reheats, you populate the universe with all relativistic species, both matter and gauge fields. Reheating after inflation is what we would normally call "hot big bang", and so both fields would exist at this early time. If we speculate earlier than this, as in, what created the inflaton, then I suppose it's possible that the inflaton was created and nothing else, but I can also imagine a standard big bang initial universe that creates everything plus inflaton, inflation happens, and viola.
bapowell said:However, we don't know anything about what happened before inflation. Why do you suggest that there wasn't matter/antimatter? I think the OP was suggesting that the annihilation produced the big bang -- a bunch of energy gets released and drives the initial expansion. But you are absolutely right...you don't get inflation from radiation.
This is pretty accurate. In curved space, you are right that there is no longer a unique plane wave solution in general. The key scales which determine whether the particle concept is valid are: 1) the curvature scale of the space and 2) the Compton wavelength of the particle. When the Compton wavelength of the particle becomes larger than the curvature radius, the vacuum state of that particle becomes a multiparticle state -- particles are created. As you are probably aware, a concrete example of such 'curvature induced' particle creation is Hawking radiation. Here, particles are generated from the vacuum (recall the quantum vacuum has nonzero energy) and due to the existence of the event horizon of the black hole, 'part' of this energy is radiated away. In turn, the black hole shrinks a little. So, in a sense, there is an exchange of energy between curvature and particles.friend said:As I understand it, particles are represented in QFT by waves in flat space. So in curved spacetime, particles are not well defined. But every point locally is flat even in curved space. So I wonder if particles come into and out of existence as space curvature changes or as space expands. This would mean that particles share energy with spacetime, or that spacetime is just another type of particle interacting with rest of the particle zoo.
This I don't quite understand. We can of course differentiate between energy stored in particles and energy stored in curvature on scales smaller than the curvature radius. In any case, energy (particles) produced by the gravitational field (such as in the Hawking effect) is tiny in comparison to 'legitimate' matter -- the stuff created by the big bang. More on this in a moment...In that case, you can't say which came first because one is the alternate form of the other.
Perhaps. In order to get inflation, one must have a gravitational source with a negative pressure. Vacuum energy has this property, and is currently a popular way to implement inflation. However, actual particles (radiation or dust) do not cause inflationary expansion.So it might be legitimate to say that particle interactions with spacetime drove inflation.
This seems interesting but speculative. We have a good understanding of how to implement inflation using vacuum energy. This is a finite contribution to the stress energy tensor (source of gravity). During inflation, the curvature scale is set by the Hubble radius. Particle with wavelengths surpassing the Hubble radius are produced during inflation (in current literature, the term 'perturbation' is used in lieu of particle). These perturbations are exactly that -- perturbations -- in the sense that they are higher order contributions to the curvature (at lowest order, they don't couple at all -- and so they can't source curvature). The perturbations that are generated during inflation (which is driven by some nonperturbative source, like the vacuum energy discussed above), while they don't participate in driving inflation, they do have very important consequences for the later formation of structure in the universe.It might be that the curvature of space contains a form of potentional energy. This energy is converted back and forth between particles which quickly convert back into curvature. But as these virtual particle live longer and longer, they interact with each other, lose energy and are not so easily converted into curved spacetime. The result would be that space expands and becomes flat. This is a mechanism for particles to drive inflation.
friend said:In that case, you can't say which came first because one is the alternate form of the other. So it might be legitimate to say that particle interactions with spacetime drove inflation. It might be that the curvature of space contains a form of potentional energy. This energy is converted back and forth between particles which quickly convert back into curvature. But as these virtual particle live longer and longer, they interact with each other, lose energy and are not so easily converted into curved spacetime. The result would be that space expands and becomes flat. This is a mechanism for particles to drive inflation.
Of course, you need a model first. If what you are saying somehow fits into general relativity or some other accepted gravity theory, then you'd do well to utilize such a theory to substantiate the claims you are making here. I have a hard time seeing how much of any of what you say fits into any accepted theory. If you are attempting to strike out in a new direction, I caution you to read the forum rules about overly speculative posts.apeiron said:Of course, dark energy would have to be fitted into this model as a further factor. Though it could just be a measure of QM uncertainty in the expansion mechanism I suspect.
bapowell said:Of course, you need a model first. If what you are saying somehow fits into general relativity or some other accepted gravity theory, then you'd do well to utilize such a theory to substantiate the claims you are making here. I have a hard time seeing how much of any of what you say fits into any accepted theory. If you are attempting to strike out in a new direction, I caution you to read the forum rules about overly speculative posts.
bapowell said:If you are attempting to strike out in a new direction, I caution you to read the forum rules about overly speculative posts.
bapowell said:Who cares? What does this have to do with the thread. Physics is an empirical science. Last I checked, philosophy is not.
Why? Your post "from nothing -> NOTHING" has nothing to do with this thread (it does relate to the title of the thread, but if you read through it you'll find that it's not even remotely a theme). This is a physics forum. "from nothing -> NOTHING" is not physics. It's not a physicist's job to define "nothing". It's a philosopher's.yoda jedi said:define nothing...
bapowell said:Why? Your post "from nothing -> NOTHING" has nothing to do with this thread (it does relate to the title of the thread, but if you read through it you'll find that it's not even remotely a theme). This is a physics forum. "from nothing -> NOTHING" is not physics. It's not a physicist's job to define "nothing". It's a philosopher's.
apeiron said:It sounds like the standard idea that the material to start the big bang arose as a quantum fluctuation out of "nothing".
http://en.wikipedia.org/wiki/Edward_Tryon
Of course, quantum fluctuations would seem to have to arise out of some framework of existence. So not exactly nothing.
yoda jedi said:you have to read carefully...
Mr. Smart Aleck... ...lol...
Read
Whoops. You got me. By all means, carry on.yoda jedi said:you have to read carefully...
Mr. Smart Aleck... ...lol...
IcedEcliptic said:I'm confused, it seems like you are saying that from nothing there can be nothing. Nothing is an infinity, and how do you grasp this? Nothing is an unimaginable as infinite something, so which is more absurd to our minds? Something from something that has always been there, or something from nothing that was previously there. They are both inconceivable, and so intuiting it seems awry. The math is the way here, and knowing when we have become philosophers.
IcedEcliptic said:I'm confused, it seems like you are saying that from nothing there can be nothing.
yoda jedi said:nothing is the absolute vacuum.
In any case you can grasp or comprehend the concept of infinity, see for example the work of Georg Cantor, Cantor's discovered that there is not just one infinity, but a never-ending hierarchy, each infinitely bigger than the last, he gave a detailed analysis of infinity.
no way.
from nothing, nothing, nada.
Cantor was a pioneer of set theory. He developed several concepts, such as the cardinality (roughly the size) of sets. He developed the ideas of 'countable' vs. 'uncountable' infinity. As a quick taste, consider the integers and the real numbers. Even though there are an infinite number of elements in each set, there are infinitely more reals than integers. This should be pretty obvious -- you can fit an infinite number of real numbers between the the two integers 0 and 1. His work on infinity has not been free of criticism, however, as some mathematicians believe that it is sensible to compare two infinities. Also look up the Cantor Set.IcedEcliptic said:Can you link me to this work by Georg Cantor? I cannot seem to find it, but it sounds like it is worth the reading.
yoda jedi said:nothing is the absolute vacuum.
bapowell said:This is pretty accurate. In curved space, you are right that there is no longer a unique plane wave solution in general. The key scales which determine whether the particle concept is valid are: 1) the curvature scale of the space and 2) the Compton wavelength of the particle. When the Compton wavelength of the particle becomes larger than the curvature radius, the vacuum state of that particle becomes a multiparticle state -- particles are created.
apeiron said:A vacuum is still a something, no matter how "absolute". It has global properties like a temperature and a dimensional structure. So what are you trying to say here? Your point is unclear to me.
IcedEcliptic said:Can you link me to this work by Georg Cantor? I cannot seem to find it, but it sounds like it is worth the reading.
yoda jedi said:http://www.math.vanderbilt.edu/~schectex/courses/infinity.pdf
Georg Cantor (1845-1918):
The man who tamed infinity.
"Eventually Cantor’s ideas won out and became part of mainstream mathematics.
David Hilbert, the greatest mathematician of the early 20th century, said in 1926 that
“No one can expel us from the
paradise Cantor has created.”
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http://www.archive.org/stream/contributionstot003626mbp#page/n1/mode/2up
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yoda jedi said:you are talking about the true vacuum, the vacuum of quantun mechanics (quantum fluctuations, quantum harmonic oscillators, etc), i am talking about ideal emptiness, a state that not exist physically.
apeiron said:But how is an "ideal emptiness" not still a crisply global something - a container or context of some kind? There may be nothing at every location,
yoda jedi said:Which locations ?
Why can't such a state exist physically? You've given no reason for this. A supersymmetric quantum vacuum has zero energy.yoda jedi said:you are talking about the true vacuum, the vacuum of quantun mechanics (quantum fluctuations, quantum harmonic oscillators, etc), i am talking about ideal emptiness, a state that not exist physically.
apeiron said:The ones that are empty of course.
bapowell said:Why can't such a state exist physically? You've given no reason for this. A supersymmetric quantum vacuum has zero energy.
Wow. You're not listening. Do you know what a supersymmetric vacuum is?yoda jedi said:wrong, quantum vacuum is not a zero energy state.
"According to present-day understanding of what is called the vacuum state or the quantum vacuum, it is "by no means a simple empty space", and again: "it is a mistake to think of any physical vacuum as some absolutely empty void." According to quantum mechanics, the vacuum state is not truly empty but instead contains fleeting electromagnetic waves and particles that pop into and out of existence."
bapowell said:Wow. You're not listening. Do you know what a supersymmetric vacuum is?
bapowell said:Wow. You're not listening. Do you know what a supersymmetric vacuum is?
This is a common question when discussing the origins of the universe. The concept of something coming from nothing can be difficult to grasp, but in physics, the term "nothing" does not mean a complete absence of anything. Instead, it refers to a state of extremely high energy and density, which eventually led to the formation of the universe.
The Big Bang theory is the most widely accepted explanation for the origin of the universe. However, it is still unknown what exactly caused the Big Bang. Some theories suggest that it was a result of quantum fluctuations in the vacuum of space, while others propose the existence of a multiverse. The exact cause is still a topic of ongoing research and debate among scientists.
While it may seem counterintuitive, there is a lot of evidence that supports the idea that the universe came from nothing. For example, the expansion of the universe, the cosmic microwave background radiation, and the abundance of light elements all point to the early universe being extremely hot and dense, which aligns with the Big Bang theory.
This question delves into the philosophical debate of existence and the concept of nothingness. While science can provide explanations and evidence for the origins of the universe, the question of whether something can truly come from nothing is a matter of perspective and personal belief.
The concept of time and space as we know it did not exist before the Big Bang. Therefore, it is difficult to determine what existed before it. Some theories suggest that the universe goes through cycles of expansion and contraction, with each Big Bang being a new beginning. However, this is still a topic of speculation and is yet to be proven by scientific evidence.