Space, Fields, Mass & Energy? Who makes who?

[JohnSSM]

This discussion cropped up 12 pages into a Speculative forum post, but I wanted to start a new thread here.

What was there before the big bang, if anything? When you imagine the setting before the big bang, what do you typically imagine? An ultra small, ultra energetic point of nothingness? That's kinda what ive always imagined...Apparently, in this view, there is no space yet. If you see your tiny energetic point in a big open space, its ok, you cant really see something with no spatial values, but to think the "space around" that point is spacetime, would be a misconception...and also there is no mass yet, mass is really a factor of moving and there isn't any moving going on within a place with no space. But we do have energy...massless, non moving energy that occupies no space...There could be fields though...Since the nature of fields in much harder to imagine and most people don't consider them any different from space itself, which is not true...space would at least be a conglomeration of fields, but with no space, no mass and no motion those fields would have nothing to guide or dictate....but that doesn't mean the fields are not present just because space is not...or that's how I see it...I write from a perspective of truth, but these are only my thoughts and I know that...Although I do believe they are being guided by GR and QM...Im thinking in terms of them being unified, in a way...If you don't consider them both simultaneously, then you need to have a theory of what existed before the big bang in GR...and another for what existed in terms of QM...If ya cant mix em, ya cant mix em...but im kinda taking what I know about both...I don't know how you could when discussing such a topic...

This point was brought on by another point...When describing the geometrical effects of GR on space-time, one might say, "The geometry of space-time (gravity) is dictated, in whole, by the relative motion and energy of mass, through properties belonging to the mass itself and other masses which are present" What "happens to" space-time is not a mechanism of space-time. Gravity isn't even "real", it's just a relative effect of all the vectors of mass-energy. Nothing is pulling you...energy is pointing you...and you don't even move, you just gain energy in a certain vector...that's all that needs to occur to curve space-time and create relative motion...the first thing that becomes obvious is that you cannot have straight lines in space...even with no other mass around you and no gravitational effects other than the ones produced by your own mass, you would still spin...but you don't really spin...youre just given a relative perception of spinning...

Alas, the point becomes, does the presence of mass not only create the curves in space? does it also create space as it simply creates a vector from the existence of its energy?...and since that stuff doesn't sit still, it always has a vector...What's the point? It seems that you cannot have space without mass...if nothing is there, then there are no properties to create a geometrical model of anything...space doesn't sit there unfilled...its a relative perspective of GR and gravity...space is as unreal as motion...or, it seems to me, using what I understand about GR...

As soon as space does exist, it gives those fields a chance to put their theoretical directives to use and they become fields in space-time...can there be fields without space-time?...seems possible to me since its just a...what is it? a set of guidelines for that which react with it? It doesn't have to exist in a reaction to exist...just like the geometry that guides GR...its just sitting there, ready to guide GR...we don't need anything to figure for GR...put in some mass and GR figures itself....maybe GR didn't even exist before the big bang...the rules could have formed after mass was finally created...

Id really like the GR point of view on this...Im sticking to it the best I know.



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[Strange]

What was there before the big bang, if anything?

 

No one knows. There are a large number of different hypotheses. In GR there is no "before" but it is assumed we need a theory of quantum gravity to udnerstand the earliest stages (and, perhaps, before).

[JohnSSM]

I do agree and hopefully you can appreciate what I said about needing to think I terms of both GR and QM which cant be done yet...So this is all speculative again, isn't it?

[elfmotat]

General Relativity says that energy-momentum and spacetime curvature are equivalent. Neither "creates" the other. The field equation of GR is:

 

[math]G_{\mu \nu} = \frac{8 \pi G}{c^4} \, T_{\mu \nu}[/math]

 

the left hand side is spacetime curvature, T is energy-momentum density, and they are related by a constant.

 

As for quantum gravity, the straightforward approach you would expect to use for a quantum field theory of gravity simply does not work. For the other three forces + matter, you take the Lagrangian of the theory and plug it into the path integral. After some very clever and tedious calculations you will be able to use this to make numerical predictions about different types of interactions that might take place by using a process called renormalization. It was mathematically proven a number of years ago that GR simply is not renormalizable. I.e. QFT and GR are simply not compatible as-is. Either our theory of gravity needs to be reconsidered, or our approach to QFT, or both. There are a number of approaches which purport to solve this problem, String Theory and Loop Quantum Gravity being the most well-known, though none has been completely successful.

 

That being said, we are not completely at a loss. There are a number of things we can do which we can be reasonably confident about. For example, semi-classical gravity, where the stress-energy tensor in the GR field equation is replaced by the expectation value of the stress-energy operator:

 

[math]G_{\mu \nu} = \frac{8 \pi G}{c^4} \, \langle \hat{T}_{\mu \nu} \rangle[/math]

 

This gives an approximation method for finding the gravitational field generated by a quantum field, though we are still considering spacetime as a classical object. We are also able to do QFT calculations on curved background spacetimes, giving us a good approximation of how quantum fields behave in the vicinity of, for example, a black hole. This is how things like Hawking radiation and black-hole entropy are rigorously analyzed.

 

I believe Strange answered your question regarding the Big Bang. GR predicts spacetime was a singularity at t=0. I.e. GR predicts that space and time simply did not exist "before" t=0. This obviously seems a bit unphysical. Until there's a successful quantum theory of gravity we probably won't know much about what was actually going on.

[JohnSSM]

I also predicted that space and time did not exist...Did you see that in my post?

I find it interesting that while in forums, folks dont really address what is being said...SO much of my post is just ignored...but there are points all through it I was hoping to discuss...

[elfmotat]

I also predicted that space and time did not exist...Did you see that in my post?

 

You didn't "predict" it, you just stated it. That's not the same thing. If you wanted me to, I could go through all the calculations in GR which actually predict (i.e. numerically, quantitatively, non-ambiguously) that spacetime converges to a singularity as t goes to zero. Can you do the same with your ideas?

 

 

I find it interesting that while in forums, folks dont really address what is being said...SO much of my post is just ignored...but there are points all through it I was hoping to discuss...

 

Unfortunately, this is because your "points" are rather vague and ill-defined. It's hard to address questions that don't really make much physical sense. If you had asked more concrete questions then I would have given concrete answers to those questions. Instead, your OP seems more like existential musings rendered into prose. I did the best I could with what you provided -- I gave concrete answers to the general sentiment of the post.

 

If you want me to go through line by line and address each point individually, my response will mostly consist of "please define X," or "X doesn't make sense," or "what do you mean by X?"

Edited January 9, 2015 by elfmotat

[JohnSSM]

 

You didn't "predict" it, you just stated it. That's not the same thing. If you wanted me to, I could go through all the calculations in GR which actually predict (i.e. numerically, quantitatively, non-ambiguously) that spacetime converges to a singularity as t goes to zero. Can you do the same with your ideas?

 

 

 

Unfortunately, this is because your "points" are rather vague and ill-defined. It's hard to address questions that don't really make much physical sense. If you had asked more concrete questions then I would have given concrete answers to those questions. Instead, your OP seems more like existential musings rendered into prose. I did the best I could with what you provided -- I gave concrete answers to the general sentiment of the post.

 

If you want me to go through line by line and address each point individually, my response will mostly consist of "please define X," or "X doesn't make sense," or "what do you mean by X?"

Sure...lets try it once...Thats exactly what I would expect..

I dont think math is the only way to predict something...

[elfmotat]

Sure...lets try it once...Thats exactly what I would expect..

I dont think math is the only way to predict something...

 

Math is the only way to unambiguously, quantitatively, numerically predict something. Math is the language of physics. Physics consists of mathematical models compared with experimental/observational data. Below is a video you may find informative. Pay close attention to the part at 5:00, where he discusses vague theories and why they are not scientific.

 

Edited January 10, 2015 by elfmotat

[JohnSSM]

 

Math is the only way to unambiguously, quantitatively, numerically predict something. Math is the language of physics. Physics consists of mathematical models compared with experimental/observational data. Below is a video you may find informative. Pay close attention to the part at 5:00, where he discusses vague theories and why they are not scientific.

 

Yes...feynman was my personal tutor on youtube and has been for years...along with some other fellas who won nobel peace prizes...

 

I love the part when he kinda scoffs and says "this is what newton dreamed up about gravity"...lol...dreaming got him really far...and believing that GR and QM in either of their current states will be the most correct answers in 200 years is really short sighted...if we lived that long, id put all my money on it...

 

If you dont want to take the time to ration out my words with interpretive communication skills, its ok...They have moved me to speculations, so, we can just talk openly..there is no thoery to prove any of it...yet

 

I know i need to keep it close to reality and real science, but asking which forces are complimentary forces and which are frame forces seems to be legit in QM if it will ever be figured out...it seems we can throw our own ideas around...thats what I did...I tried to keep them within the realm of QM, even though I posted in GR...but its really a piece about unifying them

 

 

 

 

[elfmotat]

Yes...feynman was my personal tutor on youtube and has been for years...along with some other fellas who won nobel peace prizes...

 

I love the part when he kinda scoffs and says "this is what newton dreamed up about gravity"...lol...dreaming got him really far

 

Are you watching the same video as me?

 

and believing that GR and QM in either of their current states will be the most correct answers in 200 years is really short sighted...if we lived that long, id put all my money on it...

 

When did anyone say otherwise? This seems very tangential.

 

If you dont want to take the time to ration out my words with interpretive communication skills, its ok...They have moved me to speculations, so, we can just talk openly..there is no thoery to prove any of it...yet

 

To prove any of what?

 

I know i need to keep it close to reality and real science, but asking which forces are complimentary forces and which are frame forces seems to be legit in QM if it will ever be figured out...it seems we can throw our own ideas around...thats what I did...I tried to keep them within the realm of QM, even though I posted in GR...but its really a piece about unifying them

 

I have no idea what you mean by "complimentary forces" and "frame forces." I've never encountered those terms before.

[JohnSSM]

yes...same video....right before the 5 minute mark...he is using newtons laws of gravity of his example of the law that didnt last because of new math...

They say otherwise when they take certain ideas and put them in speculations...

Not looking for proof...looking for perspectives and online discussion...its a forum, not a reality test...

I heard someone in a forum refer to spacetime as a reference frame and EMF as a secondary frame...called it complimentary by mistake...sorry bout that...

[swansont]

believing that GR and QM in either of their current states will be the most correct answers in 200 years is really short sighted...if we lived that long, id put all my money on it...

 

 

Depends on what you mean by "most correct". Most precise? No, very likely not — someone will come up with a refinement or a new model that does better. But most applicable? Newton still owns the day on that one. Any new theory that comes along will give the same results under the same conditions. Sending a rocket to rendezvous with a comet (or whatever) is still done with Newtonian physics.