Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: thedoc on 19/12/2016 11:53:01
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Calvin asked the Naked Scientists:
Hi Chris.
I have recently discovered your show (http://www.thenakedscientists.com/HTML/podcasts/) and have been enjoying your podcasts (http://www.thenakedscientists.com/HTML/podcasts/). I have a couple of closely-related questions which I have been wondering about which perhaps you can answer: (1) what existed before the big bang, and (2) where did the energy come from to set the big bang in motion?
Thanks so much for your show (http://www.thenakedscientists.com/HTML/podcasts/).
Calvin Girvin
Stephenville, Texas
What do you think?
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I'm no expert on the subject, but I understand the Big Bang to be an explosion of time, which occurred simultaneously at all points in space. It doesn't make sense to ask what happened before that event because time is not defined in that context. By the same token, you can't ask what caused the event because causation requires a time line. Hawking describes it as a quantum fluctuation, which separated the future from the past. It's similar to spontaneous creation of a matter-antimatter pair.
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Calvin asked the Naked Scientists:
Hi Chris.
I have recently discovered your show (http://www.thenakedscientists.com/HTML/podcasts/) and have been enjoying your podcasts (http://www.thenakedscientists.com/HTML/podcasts/). I have a couple of closely-related questions which I have been wondering about which perhaps you can answer: (1) what existed before the big bang, and (2) where did the energy come from to set the big bang in motion?
Thanks so much for your show (http://www.thenakedscientists.com/HTML/podcasts/).
Calvin Girvin
Stephenville, Texas
What do you think?
The energy didn't come from anywhere because the total energy of the universe is zero. The positive energy associated with matter is exactly canceled by the negative energy associated with gravity.
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That's true. Energy can't be created or destroyed. It can only change from one form to another. But the Big Bang created churn in the various energy fields (i.e. entropy) so the genesis question is, where did the fields come from and what motivated all of that churn?
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The energy didn't come from anywhere because the total energy of the universe is zero. The positive energy associated with matter is exactly canceled by the negative energy associated with gravity.
I take it that is an assumption. There is surely no way to demonstrate that except by assuming it to be true and testing that assumption against predictions,is there?
We are free to make other assumptions and test them also ,perhaps?
If the sum total of positive/negative energy was exactly zero (perhaps disallowed by quantum theory?) then it may suggest that the universe is entirely self referential and there was nothing that caused it.
I suppose this is multiverse territory, though;)
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I take it that is an assumption. There is surely no way to demonstrate that except by assuming it to be true and testing that assumption against predictions,is there?
It's a law of physics, i.e. the conservation of energy. If you're not familiar with what a law of physics is, then let me explain. A physical law statement inferred from particular facts, applicable to a defined group or class of phenomena. It's a postulate which is a statement accepted as true for the purposes of argument or scientific investigation; also, a basic principle. We hold these to be true as long as they are consistent with observations. Its what you might call an "assumption." So yes. It's an assumption. But not something that is without any justification.
Most amateurs don't realize if but the absolute value of the energy of a system has no physical meaning so it can be set to anything one wishes. What is physically meaningful is that its always constant. So we can set that constant to zero before the be big bang and it will remain zero. It's no different in cosmology than in classical mechanics.
If you'd like to read the details then see
The Inflationary Universe by Alan H. Guth, Addison Wesley, 1997, page 9-12.
You can download it for free at: http://b-ok.org/book/2192972/f7d328
As for where the universe came from there is a scientific idea that it came from vacuum fluctuations. This was first proposed by Edward Tyron.
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If you'd like to read the details then see
The Inflationary Universe by Alan H. Guth, Addison Wesley, 1997, page 9-12.
You can download it for free at: http://b-ok.org/book/2192972/f7d328
Thanks very much . I will try to look at it (although it may take me a while to get around to it)
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I take it that is an assumption. There is surely no way to demonstrate that except by assuming it to be true and testing that assumption against predictions,is there?
It's a law of physics, i.e. the conservation of energy.
Sadly, this is not the case.
First, the conservation of energy is not something that one can easily apply in the context of GR. It is not something that one can say holds in all the contexts that we are used to imagining in classical physics.
Second, the idea that the entire energy of the universe is canceled out by gravity is part of some hypothetical models of the universe. It is not something demonstrated, nor is it required to be part of the standard cosmological model.
Most amateurs don't realize if but the absolute value of the energy of a system has no physical meaning so it can be set to anything one wishes. What is physically meaningful is that its always constant. So we can set that constant to zero before the be big bang and it will remain zero. It's no different in cosmology than in classical mechanics.
That's a far different statement than one that says that the value is exactly cancelled out by gravity. The cancelling out statement is supposed to have specific physical content, rather than the nebulous it-doesn't-matter-so-arbitrary approach. One claim cannot support the other.
If you'd like to read the details then see
The Inflationary Universe by Alan H. Guth, Addison Wesley, 1997, page 9-12.
You can download it for free at: http://b-ok.org/book/2192972/f7d328
As for where the universe came from there is a scientific idea that it came from vacuum fluctuations. This was first proposed by Edward Tyron.
Yes, reading the book by Guth you will see Guth advocating a sort of vacuum fluctuation hypothesis, wherein it is proposed that the total energy of the universe is 0 is the gravity-cancelling way.
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Calvin asked the Naked Scientists:
Hi Chris.
I have recently discovered your show (http://www.thenakedscientists.com/HTML/podcasts/) and have been enjoying your podcasts (http://www.thenakedscientists.com/HTML/podcasts/). I have a couple of closely-related questions which I have been wondering about which perhaps you can answer: (1) what existed before the big bang, and (2) where did the energy come from to set the big bang in motion?
Thanks so much for your show (http://www.thenakedscientists.com/HTML/podcasts/).
Calvin Girvin
Stephenville, Texas
What do you think?
I question the Big Bang and prefer a universe which is infinite and filled with an infinity of lesser such bangs rendering a homogenous CMBR that only appears to have been created by a single event.
"Worlds without end."
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I question the Big Bang and prefer a universe which is infinite and filled with an infinity of lesser such bangs rendering a homogenous CMBR that only appears to have been created by a single event
Why?
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I question the Big Bang and prefer a universe which is infinite and filled with an infinity of lesser such bangs rendering a homogenous CMBR that only appears to have been created by a single event
Why?
For several reason, one of which is honestly due to personal preference. But the better case for this position, revolves around the significant possibility that space/time is indeed flat and that position lends support to the infinite model. If that be the case, then it demands no special need for a singular big bang. The lesser case has do with my position on determinism, and as many have questioned, "What was before so what caused the Big Bang"? I prefer to take the position that in an infinite universe, there is no need for a beginning. Infinite in time, infinite in scope, and infinite in possibilities. Besides, with the choices we have, the best two are "The Big Bang" and "The Infinite Model" and I just prefer the latter.
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I question the Big Bang and prefer a universe which is infinite and filled with an infinity of lesser such bangs rendering a homogenous CMBR that only appears to have been created by a single event
Why?
For several reason, one of which is honestly due to personal preference. But the better case for this position, revolves around the significant possibility that space/time is indeed flat and that position lends support to the infinite model. If that be the case, then it demands no special need for a singular big bang. The lesser case has do with my position on determinism, and as many have questioned, "What was before so what caused the Big Bang"? I prefer to take the position that in an infinite universe, there is no need for a beginning. Infinite in time, infinite in scope, and infinite in possibilities. Besides, with the choices we have, the best two are "The Big Bang" and "The Infinite Model" and I just prefer the latter.
You do realize that your position is not consistent, right? Since all the space you have observable access to is a single "big bang" zone, regardless of how many there might be.
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The singularity (assuming it existed) is were the energy for the big bang came from. What sets the big bang off is complex. I will try to explain that as best I can.
When the singularity collapsed and formed the big bang there was an explosion which was the result of the singularity converting all of it's mass into energy which caused an emission of photons. The process of converting the mass into energy is practically instant so there were photons emitted only for a spit second. It sort of creates an EMP wave or a hollow shell/orb of photons moving away from the point of the singularity
in other words the first light of the big bang blooms out in an electromagnetic pulse of light and energy, This first light is still traveling to this day.
But the light will not just go on forever, it is still bound to the mass of the universe no matter how far away it is. The mass of the universe will still bend the light if only slightly over billions of years until the light comes back around trillions of years later. By that time the singularity would reform and the first light will be the last in the next big bang.
In other words the first light of the big bang will be used to trigger the next big bang far in the future.
I described this terribly, but I hope what I'm saying makes sense. :P
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There had to be a repulsive force of unknown origin that triggered inflation. If the big bang started from a singularity this is one possible way that it could have happened. When all the forces were united there may have been the conditions present for such an action. It is open to endless debate.
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There had to be a repulsive force of unknown origin that triggered inflation. If the big bang started from a singularity this is one possible way that it could have happened. When all the forces were united there may have been the conditions present for such an action. It is open to endless debate.
There was a repulsive force but it didn't cause inflation, it was inflation. So long as its understood that the term inflation refers to the inflationary period of the big bang.
The term big bang is misleading because it gives the false impression that there was an explosion of some sort and there's nothing in the big bang theory about an explosion. Peebles explains it very nicely in his text
Principles of Physical Cosmology on page 6
The familiar name for this picture, the "big bang" cosmological model, is unfortunate because it suggests we are identifying an event that triggered the expansion of the universe, and it may also suggest that the event was an explosion localized in space. Both are wrong.
Its best to read the context in which that was written so I suggest that folks here download it and read it. It can be found here
http://b-ok.org/book/667792/03a6bb
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lets say I'm a photon, one of the first photons that the big bang generated. I the photon would travel in one direction for countless centuries as there is nothing in my way to stop me. I have traveled to this day 13.7 billion light years away from ground zero, on the edge of nothingness. When the big bang occurred and sent me on my way another kind of wave traveled with me, gravity waves. The gravity waves were generated as the singularity converted all of its mass into energy (at the same time I the photon was born)
I have traveled with the gravity waves on the edge of space the gravity waves act on me, curving me and eventually causing me to turn all the way around and return to ground zero a process that would take trillions of years but it would mean that the new singularity would be bombarded with photons like me, the first light of the last big bang.
So much light hitting the new singularity (which will form trillions of years in the future) would hit the singularity at a direct angle (straight at the nucleus of the singularity) which will rapidly heat the core of the singularity and cause it to rupture.
Also inflation could have just been what happens when the singularity releases it's grip on the fabric of space. When the gravitational field of the singularity tried to snap back to it's original orientation.
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lets say I'm a photon, one of the first photons that the big bang generated. I the photon would travel in one direction for countless centuries as there is nothing in my way to stop me.
Why not? It can always be absorbed by something like an atom or planet etc.
The gravity waves were generated as the singularity converted all of its mass into energy (at the same time I the photon was born)
First off, all of its energy was zero. Its a misconception to think that energy can be converted into mass.
I have traveled with the gravity waves on the edge of space the gravity waves act on me, curving me and eventually causing me to turn all the way around and return to ground zero a process that would take trillions of years but it would mean that the new singularity would be bombarded with photons like me, the first light of the last big bang.
Can't happen. The big bang was an expansion of space, not merely photons flying away from each other. And it wasn't merely photons which existed after the big bang but other particles like electrons and protons etc.
Also inflation could have just been what happens when the singularity releases it's grip on the fabric of space. When the gravitational field of the singularity tried to snap back to it's original orientation.
Please put that in the new theories forum,. not here.
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Here's a fairly coherent account of the Big Bang:
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Here's a fairly coherent account of the Big Bang:
That's not related to the big bag. That appears to be a nebula and thus not directly related. In fact not related at all other than resulting from the big bang. I.e. I myself am about as related to the big bag as what's in that photo.
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String Theory (more properly called M Theory) can answer this question if you are ready to believe in extra dimensions and other universes in higher dimensions. We all know that gravity is a force that pull every thing down. but gravity is actually weaker than the other forces in the universe such as the electromagnetism. According to string theory the must be particles of gravity just as there are particles of electromagnetic force called photons. These particles of gravity is called gravitons. The core of string theory is that all particles contains a string. One string is contained by each particle. The string of each particle vibrate differently giving each particle a different characteristics. According to string theory our universe is surrounded by a largely stretched string called a membrane. Now strings of photons and the strings of matter is attached to the membrane of our universe but the strings of particles like gravitons are enclosed in loops and not attached to the membrane of our universe and so the gravitons can move into other dimensions and parallel universes and thus diluting the force of gravity in our universe. For this to happen according to string theory there must be 11 dimensions (4 dimensions of our universe and 7 extra dimensions). Now according to some String Theorists, the membrane surrounding our universe and the membranes surrounding the other universes in higher dimension float. sometimes once in a billions and billions of light years these membranes collide and cause Big Bang releasing infinite amount of energy to be released in the universes colliding. So according to string theory the big bang of our universe may have caused from the membrane of our universe colliding with the membrane of another universe in a higher dimension.
I KNOW I HAVE GONE A BIT OFF TOPIC BUT IT WAS TO SHOW HOW STRING THEORY RELATES TO BIG BANG. WHATEVER I HAVE SAID THERE IS MATHEMATICAL EQUATIONS TO PROVE IT BUT EXPERIMENTALLY ANY OF THIS HAS NOT BEEN PROVEN YET.