Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: MikeS on 23/10/2011 07:44:51
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Mass creates gravity. At the moment of the big bang and for a short time after, all that existed was energy and energy without mass has no gravity. Without gravity the universe would have inflated until such time as matter and antimatter were created.
The curvature of space by gravity is possibly what creates time. Therefore the inflation would have taken place possibly outside of time as without mass, gravity and therefore time did not yet exist.
The above does not contradict the idea of inflation. It just explains the cause.
Is this a reasonable explanation?
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Mike - energy causes curvature of space-time; ie gravity. it does not need to be matter - energy and mass are equivalent.
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Mass creates gravity. At the moment of the big bang and for a short time after, all that existed was energy and energy without mass has no gravity. Without gravity the universe would have inflated until such time as matter and antimatter were created.
The curvature of space by gravity is possibly what creates time. Therefore the inflation would have taken place possibly outside of time as without mass, gravity and therefore time did not yet exist.
The above does not contradict the idea of inflation. It just explains the cause.
Is this a reasonable explanation?
Mike - energy causes curvature of space-time; ie gravity. it does not need to be matter - energy and mass are equivalent.
I disagree. Einstein defined "gravity" quite differently, as many modern scientists do today. He wrote in his 1916 paper, page 148
The special theory of relativity has led to the conclusion that inert masa is nothing more or less than energy..
Om page 143 Einstein wrote
We make a distinction hereafter between "gravitational field" and "matter" in ths way that we denote everything but the gravitational field as "matter." Our use of the word therefore includes not only matter in the ordinary sense, but the electromagnetic field.
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PMB - how would you and other modern scientists define it then?
I disagree. Einstein defined "gravity" quite differently, as many modern scientists do today. He wrote in his 1916 paper, page 148
The special theory of relativity has led to the conclusion that inert masa is nothing more or less than energy..
Om page 143 Einstein wrote
We make a distinction hereafter between "gravitational field" and "matter" in ths way that we denote everything but the gravitational field as "matter." Our use of the word therefore includes not only matter in the ordinary sense, but the electromagnetic field.
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PMB - how would you and other modern scientists define it then?I disagree. Einstein defined "gravity" quite differently, as many modern scientists do today. He wrote in his 1916 paper, page 148
The special theory of relativity has led to the conclusion that inert masa is nothing more or less than energy..
Om page 143 Einstein wrote
We make a distinction hereafter between "gravitational field" and "matter" in ths way that we denote everything but the gravitational field as "matter." Our use of the word therefore includes not only matter in the ordinary sense, but the electromagnetic field.
See http://home.comcast.net/~peter.m.brown/sr/inertial_mass.htm
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Peter - this is a discussion forum not a link site for your blog/site.
You said I had ill-defined gravity by connecting it to space time curvature - when I asked for a clarification you post a one word answer and a link to your hobby site on inertial mass.
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Mike - energy causes curvature of space-time; ie gravity. it does not need to be matter - energy and mass are equivalent.
Imatfaal
Energy and mass are only equivalent, in that matter is created from energy. In many respects they can be thought of as opposites.
Gravity causes curvature of space-time but gravity is not energy. Mass creates gravity, energy does not. If you have any arguments or links to the contrary I would be interested to know.
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Mike - energy causes curvature of space-time; ie gravity. it does not need to be matter - energy and mass are equivalent.
Imatfaal
Energy and mass are only equivalent, in that matter is created from energy. In many respects they can be thought of as opposites.
In which cases?
Gravity causes curvature of space-time but gravity is not energy. Mass creates gravity, energy does not. If you have any arguments or links to the contrary I would be interested to know.
Gravity does not curve space time - gravity is (simplistically) the effect of space time being curved.
The einstein field equations and the stress energy tensor that determine how space time are curved are notoriously complex but quite clearly include energy. The stress energy tensor has multiple blocks of components which contribute - two of such are energy density and energy flux (along with momentum flux and density)
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Mike - energy causes curvature of space-time; ie gravity. it does not need to be matter - energy and mass are equivalent.
Imatfaal
Energy and mass are only equivalent, in that matter is created from energy. In many respects they can be thought of as opposites.
In which cases?
Gravity causes curvature of space-time but gravity is not energy. Mass creates gravity, energy does not. If you have any arguments or links to the contrary I would be interested to know.
Gravity does not curve space time - gravity is (simplistically) the effect of space time being curved.
The einstein field equations and the stress energy tensor that determine how space time are curved are notoriously complex but quite clearly include energy. The stress energy tensor has multiple blocks of components which contribute - two of such are energy density and energy flux (along with momentum flux and density)
Matter is lumpy, solid and sticks together. Energy likes to dissipate. It requires energy to make 'things'. It takes energy to power 'things'. The universe is essentially made of matter but fuelled by energy.
I can't agree with that. Space time being curved is due to gravity, not gravity being an effect of curved space-time. If gravity does not curve space-time, what does? We know that mass (matter) curves space time, the greater the mass, the greater the curvature.
This would seem to imply that if energy is included then gravity must be a force? As I understand it, gravity is geometry.
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Yeah, in Einsteins definition it is. A acceleration that can be seen as 'energy expended' locally, will also produce a 'gravity' locally? So 'energy' is indeed a confusing idea. I'm still trying to see how to think of it, making sense. But if we assume that 'energy' represent the 'ground state' of everything measurable, then both space, and so its metric 'Gravity' must be 'energy'.
Myself I don't really know what 'energy' is though (more than a expression for transformations)? And where it should be situated in 'relative motion and accelerations/decelerations.
I might assume, as you get a real 'local gravity' in a acceleration/deceleration that it is a symmetry to 'energy expended'.
But where is the energy/momentum situated in a uniform motion? In 'space'? It's not local at least. Which makes me wonder how to measure it?
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You might want to argue that it indeed is situated in 'space', as shown by radiation changing its 'energy/momentum' relative 'relative motion'. But it's not measurable in that black box scenario. And if I go by how Einstein proved 'gravity/accelerations' then? A uniform motion is 'at rest'?
That's how I think of it for now. But we still have to explain the momentum. And that? Hurts me head. I've looked at the stress energy tensor for it, but it's hard to understand where, in any local positional uniformly moving system, that 'energy' is stored. Almost like Mach principle that one.
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Gravity and acceleration are equivalent and it requires energy to accelerate an object. Does this mean that energy by itself creates gravity. Not as I understand it. To accelerate an object up to relativistic speed requires a lot of energy. This energy is stored as relativistic mass. So it's the mass that creates the additional gravity, not the energy per se.
As I understand it mass is the sole cause of gravity. Energy only has the roll of producing mass. Energy by itself does not produce gravity.
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The thing is that both you and me are a little 'hands on' Mike. We want it to show, at least I do so. The idea of it 'storing' the energy may make a mathematical sense but it won't 'bend' your geodesic as I know at least? Which, if we assumed that energy, in a uniform motion close to lights speed, it should, if now energy is a local expression and equivalent to 'gravity' in some way.
And you won't be able to prove that 'energy' in a black box scenario either.
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You could define it such as motion 'must exist', and if it exist. then you will see effects relative any other 'frame of reference'. But it might also be so that 'energy'(in a uniform motion) always will need a relation to exist. Which means that although you can calculate a 'potential energy' you always will need to have 'something else' to relate it too. That is a subtle difference making 'uniform motion' acceptable to me, but making accelerations/decelerations unique, in that they then will be the only 'local effect' I know of related to motion, and then doubly unique in the way it express that effect, as gravity (constant inertia).
And that is one way to define it that I'm thinking of actually, because then we have one thing thats very 'local', and another that always will crave a relation to exist.
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Starlight change energy with your relative uniform motion, but space won't (Assuming 'virtual particles') But we expect a 'radiation' in a Rindler observer accelerating, don't we?
And 'virtual particles' is more tricky to me than thinking of space as indeterminacy. Although I used to find that description working, I'm starting to question it. But it also depends on what one mean by saying 'virtual particles', and if you expect them to be 'propagating' etc. Indeterminacy is HUP and does not involve a measurable time, and neither does it discuss 'motion'.
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But HUP do discuss 'energy', and with high 'energies' you will get spontaneous pair productions, as you should get close to the event horizon, as I think of it. And accelerations also take 'energy' to produce, uniform 'motions' do not.
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Matter is lumpy, solid and sticks together. Energy likes to dissipate. It requires energy to make 'things'. It takes energy to power 'things'. The universe is essentially made of matter but fuelled by energy.
I can't agree with that. Space time being curved is due to gravity, not gravity being an effect of curved space-time. If gravity does not curve space-time, what does? We know that mass (matter) curves space time, the greater the mass, the greater the curvature.
This would seem to imply that if energy is included then gravity must be a force? As I understand it, gravity is geometry.
Mike you are talking nonsense. matter is lumpy? energy likes? the universe is fuelled?
spacetime is curved by mass/energy not by gravity. gravity emerges from freefalling bodies following geodesics in curved spacedtime. Please try and read up on this before contradicting everything. the wikipedia page on gravitation would be a good place to start. http://en.wikipedia.org/wiki/Gravity#General_relativity
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Maybe you can look at it this way, a Lorentz contraction and a time dilation will always demand at least one other 'frame of reference' to exist. So they can exist in both a acceleration and a uniform motion. And 'gravity' could then be seen as a symmetry to 'energy expended'? But then we have Earths 'gravity', what would that make matter? Matter do not expend energy? It 'binds' energy though.
And that would indeed make a acceleration 'gravity', and so 'energy'. But how does the acceleration 'bind' that energy into 'gravity' locally? Ouch :)
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So, not 'energy expended' but 'bound energy' in both cases, although a acceleration expend 'energy' to 'bind' it. Heh, and that was a very strange definition :) It's like we have two states in this universe describing or coupled to 'gravity'. Accelerations and matter/mass. Then we have our 'uniform motion' that always will describe a state of being 'at rest' relative spaces metric 'gravity', in a geodesic, aka 'free fall'.
And 'motion' becomes truly weird.
I think 'gravity' should be a geometry, to make this work. And it should have to do with the displacements in the four 'directions/dimensions', three spatial together with one temporal, inside that local accelerating frame? But how to relate that to invariant mass. Gravity may be about time dilations and Lorentz contractions, just as uniform motion. But, you will need two 'frames of reference' to prove them, just as you will need it with 'potential energy/momentum' in a uniform motion.
When it comes to 'gravity' itself, you only need one 'frame' to prove it though, as long as it is mass or an acceleration.
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Sorry, I'm talking to myself here :) If I assume times arrow to be linked to 'c', as a 'clock', then that 'time' can't change locally. So, how would that create a 'gravity'? The room time geometry will change, but only when comparing frames of reference, same as in a uniform motion. So it still needs two frames of reference to exist, if I define it as a 'geometry'? I can't, or can I? Define it as happening locally?
The question to define here. How big is a 'frame of reference'. How many will I find using 'ideal clocks' inside that accelerating frame? If I define it from 'c', a frame of reference, ideally, should be the same length as it takes light to move one Plank length, that is one Planck time.
(To make this one work we first need to agree on that any 'clock' normally, as on Earth, is a primarily conceptual device, always approximately defined. We know that gravity dilates 'clocks', and the distance of a frame of reference should be a Plank length in my definitions, as that's where our definitions fail, as well as where we define light to 'propagate' the smallest amount. But then you have HUP to consider too, so it could be slightly 'indeterministic' and so of a slightly greater value.)
I better sleep on this one :)
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Matter is lumpy, solid and sticks together. Energy likes to dissipate. It requires energy to make 'things'. It takes energy to power 'things'. The universe is essentially made of matter but fuelled by energy.
I can't agree with that. Space time being curved is due to gravity, not gravity being an effect of curved space-time. If gravity does not curve space-time, what does? We know that mass (matter) curves space time, the greater the mass, the greater the curvature.
This would seem to imply that if energy is included then gravity must be a force? As I understand it, gravity is geometry.
"Mike you are talking nonsense. matter is lumpy? energy likes? the universe is fuelled?"
This may not be the correct terminology but is never the less true.
spacetime is curved by mass/energy not by gravity. gravity emerges from freefalling bodies following geodesics in curved spacedtime. Please try and read up on this before contradicting everything. the wikipedia page on gravitation would be a good place to start. http://en.wikipedia.org/wiki/Gravity#General_relativity
Space-time is curved by mass, I agree and said so Gravity and acceleration are equivalent and it requires energy to accelerate an object. Does this mean that energy by itself creates gravity. Not as I understand it. To accelerate an object up to relativistic speed requires a lot of energy. This energy is stored as relativistic mass. So it's the mass that creates the additional gravity, not the energy per se.
As I understand it mass is the sole cause of gravity. Energy only has the roll of producing mass. Energy by itself does not produce gravity.
If you actually read my posts you would realise that I am not "contradicting everything", in fact I am contradicting very little.
My whole point being that to the best of my knowledge, mass is the only source of gravity. (Mass[modified Oct.28] gravity and acceleration being the same.) Energy is not a source of gravity other than it can be converted into mass. Energy, by itself does not produce a gravitational field. Either it does or it does not. If it does then I would like to know how?
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Space-time is curved by mass, I agree and said so
But you also said this " Gravity causes curvature of space-time but gravity is not energy." and "The curvature of space by gravity ...." which are completely false. Go back and re-read your posts.
If you actually read my posts you would realise that I am not "contradicting everything in fact I am contradicting very little.",
"I can't agree with that. Space time being curved is due to gravity, not gravity being an effect of curved space-time. " This is a direct contradiction of what I posted and completely against all that is taught.
My whole point being that to the best of my knowledge, mass is the only source of gravity.
Then unfortunately your knowledge is lacking - try reading the introduction to gravity on wikipedia (http://en.wikipedia.org/wiki/Gravity#General_relativity) that I posted and you might start to understand and gain the required knowledge.
(Mass and acceleration being the same.)
No! Mass and energy are equivalent - gravity and acceleration can be equivalent on a local scale, but mass and acceleration are not the same. Just look at the units - mass is kg or even eV/c^2 (cos mass and energy are equivalent) acceleration is ms^-2 they are just not the same
Energy is not a source of gravity other than it can be converted into mass. Energy, by itself does not produce a gravitational field. Either it does or it does not. If it does then I would like to know how?
Converted into is not quite the same as equivalent. Energy and its flux will warp spacetime and this will be experienced as gravity.
How? that's the best and worst question of the lot. We do not know - we dont even know what spacetime is! What we do know is that we have an incredibly accurate model consisting of 10 equations which relate the einstein tensor (which describes spacetime geometry) with the stress energy tensor (which describes momentum and energy density and fluxes). This mad situation of incredibly nasty maths does however allow us to get mercury's orbit and perihelion correct, and it predicted correctly gravitational time dilation and redshift. Physics can never really answer how or why - it merely creates models that accurately parallel reality to greater and finer extents
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It's also interesting to ask yourself what you expect this 'SpaceTime' to be made of. That is, if it has a granularity. If you look on my thoughts one might expect a 'granularity' at Plank length, but as HUP is there too? I'm not sure if a 'granularity' can exist. Indeterminism comes in at a much larger scale and will adjust all outcomes, depending on you, making/creating the experiment.
"Some theories suggest that the quantum nature of space should manifest itself at the ‘Planck scale’: the minuscule 10-35 of a metre, where a millimetre is 10-3 m. However, Integral’s observations are about 10 000 times more accurate than any previous and show that any quantum graininess must be at a level of 10-48 m or smaller.
“This is a very important result in fundamental physics and will rule out some string theories and quantum loop gravity theories,” says Dr Laurent. Integral made a similar observation in 2006, when it detected polarised emission from the Crab Nebula, the remnant of a supernova explosion just 6500 light years from Earth in our own galaxy.
This new observation is much more stringent, however, because GRB 041219A was at a distance estimated to be at least 300 million light years." This one is interesting, discussing a granularity, not that you can say that it proven anything, as it builds on theoretical assumptions, but if assuming the underlying hypothesis to be correct it seems as if any graininess must be under Plank size, if existing. Which makes it way out beyond HUP territory, and outside what I expect us to ever be able to measure too.
I wonder why people think they can ignore indeterminism at small scales? Not 'modern' enough? If it exist, and if it is a outcome of the way you make the experiment then it says something very definite to me. That it's you defining a outcome, not the experiment per se, even though there are rules defining what you 'will see'.
Integral challenges physics beyond Einstein. (http://www.physorg.com/news/2011-06-physics-einstein.html)
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Maybe space is continuous and only energy is quantized. But then, we need a new concept of space-time.
Even if there is a certain limit for the energy at the Planck length, it is not necessarily the ultimate limit. In my opinion, it is just the limit of the relativity of time and a limit to the geometry of energy in quantum mechanics as we know it.
http://iopscience.iop.org/1538-4357/553/2/L97/fulltext
And, by the way, gamma-ray bursts are still unexplained, contrary to whatever you may have heard...
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It's somewhat like I think too CPT. Although I expect indeterminacy to be what you meet at those scales, making probability the tool of choice. The problem with probability is that, though it might answer what we can expect, it doesn't challenge our imagination. You could see it as the ultimate tool at small scales, defining outcomes, and adaptable to whatever new definitions we come up with, as and if, proven by experiments.
But to me it seems as somewhat of a 'dead end' in that it will not take us past the definitions we create through those experimental outcomes defining that probability. That's also a definition I might have to change, depending on the thoughts of those much more familiar with the mathematics involved here. But as it is for now I see probability as something defined by and inside the 'box' we see, no matter if defined by quantum logic or relativistic SpaceTime.
And that 'box' is to me marked out by 'c', both scales, 'down' into QM as 'up' into relativity.
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As for what a gamma-ray burst should 'come from', that's not what's discussed in that article. "According to calculations, the tiny grains would affect the way that gamma rays travel through space. The grains should ‘twist’ the light rays, changing the direction in which they oscillate, a property called polarisation. High-energy gamma rays should be twisted more than the lower energy ones, and the difference in the polarisation can be used to estimate the size of the grains."
And that's the granularity problem I'm discussing.
If we take the holographic theory of SpaceTime it seems to me to build on the way 'waves' interact. Where is a 'wave' at Plank scale?
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In quantum gravity it is, not in my theory.
see this about the quasars time variability: [;D]
http://www.thenakedscientists.com/forum/index.php?topic=31190.0;prev_next=prev
About gamma ray bursts, it is just that i read something on it last week saying no calculations using the standard black hole models can explain their properties in a satisfactory manner.
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At Planck scale, a photon should have a wavelength of 2πLp. It should look like any other photons but it should not be affected by increases in time dilation. It should create a black hole when it collides with matter. I will write further explanations in the new theories section...
Any matter should form a unitary black hole of a mass of Mp before joining another black hole of a mass of N*Mp...
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Space-time is curved by mass, I agree and said so
But you also said this " Gravity causes curvature of space-time but gravity is not energy." and "The curvature of space by gravity ...." which are completely false. Go back and re-read your posts.
If you actually read my posts you would realise that I am not "contradicting everything in fact I am contradicting very little.",
"I can't agree with that. Space time being curved is due to gravity, not gravity being an effect of curved space-time. " This is a direct contradiction of what I posted and completely against all that is taught.
My whole point being that to the best of my knowledge, mass is the only source of gravity.
Then unfortunately your knowledge is lacking - try reading the introduction to gravity on wikipedia (http://en.wikipedia.org/wiki/Gravity#General_relativity) that I posted and you might start to understand and gain the required knowledge.
(Mass and acceleration being the same.)
No! Mass and energy are equivalent - gravity and acceleration can be equivalent on a local scale, but mass and acceleration are not the same. Just look at the units - mass is kg or even eV/c^2 (cos mass and energy are equivalent) acceleration is ms^-2 they are just not the same
Energy is not a source of gravity other than it can be converted into mass. Energy, by itself does not produce a gravitational field. Either it does or it does not. If it does then I would like to know how?
Converted into is not quite the same as equivalent. Energy and its flux will warp spacetime and this will be experienced as gravity.
How? that's the best and worst question of the lot. We do not know - we dont even know what spacetime is! What we do know is that we have an incredibly accurate model consisting of 10 equations which relate the einstein tensor (which describes spacetime geometry) with the stress energy tensor (which describes momentum and energy density and fluxes). This mad situation of incredibly nasty maths does however allow us to get mercury's orbit and perihelion correct, and it predicted correctly gravitational time dilation and redshift. Physics can never really answer how or why - it merely creates models that accurately parallel reality to greater and finer extents
imatfaal
That was obviously a mistake and should have read "gravity and acceleration are the same".
What is the reasoning behind the hypothesis that energy has gravity and what experimental evidence is there to confirm it?
I know that Einstein's field equations talk about the stress-energy tensor but what does this mean in non mathematical jargon. There must have been some logic that led up to it?
The alleged gravity of energy (light) being so weak that it cannot be measured. If so, then it is conceivable that energy does not have gravity?
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It's conflicting views. If you define 'energy' as some ground state then everything, possibly, should confirm to that idea, including 'Gravity'. And that is the 'quantum particle view' in where everything somehow should be related to 'particles', bosons or fermions, as I understands it. Einsteins view was that the 'Gravity' we saw was a result of SpaceTime geometry, as I got it sometime long ago. But in his general theory of relativity he also defined a equivalence between a acceleration and 'Gravity', so it becomes a tricky subject in that a acceleration definitely uses energy to become 'Gravity'.
Against it you can use the uniform motion of a planet, also creating a 'Gravity', although not transforming it (energy).
It may well be a geometry anyway, as I see it. But then I do not know what 'energy' really is.
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I have seen the argument that a mirrored box full of photons will weigh marginally more than the same empty box. If so then that would imply that photons have mass and can therefore be a source of gravity. What I haven't been able to find is the argument describing why a box full of photons would weigh more.
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imatfaal
That was obviously a mistake and should have read "gravity and acceleration are the same".
Locally yes - gravity will always have a tidal component tho.
What is the reasoning behind the hypothesis that energy has gravity and what experimental evidence is there to confirm it?
The "hypothesis" is now generally accepted as a well tested theory - it is called General Relativity. It is as well tested as any theory in science.
I know that Einstein's field equations talk about the stress-energy tensor but what does this mean in non mathematical jargon. There must have been some logic that led up to it?
well yes the logic is based upon mass/energy equivalence
The alleged gravity of energy (light) being so weak that it cannot be measured. If so, then it is conceivable that energy does not have gravity?
Who says it cannot be measured? And no with physics as it is it is inconceivable that energy does not cause spacetime to warp.
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imatfaal
That was obviously a mistake and should have read "gravity and acceleration are the same".
Locally yes - gravity will always have a tidal component tho.
What is the reasoning behind the hypothesis that energy has gravity and what experimental evidence is there to confirm it?
The "hypothesis" is now generally accepted as a well tested theory - it is called General Relativity. It is as well tested as any theory in science.
I know that Einstein's field equations talk about the stress-energy tensor but what does this mean in non mathematical jargon. There must have been some logic that led up to it?
well yes the logic is based upon mass/energy equivalence
The alleged gravity of energy (light) being so weak that it cannot be measured. If so, then it is conceivable that energy does not have gravity?
Who says it cannot be measured? And no with physics as it is it is inconceivable that energy does not cause spacetime to warp.
General Relativity covers a lot of ground and I was specifically asking if energy has gravity. I have not been able to find any research confirming that it has been measured. All I have found are articles saying it is too weak to be measured. I agree that when looking at it from the mass/energy equivalence principle mass can be seen as energy and hence energy has mass and therefore gravity. But that is when looked at from the energy equivalence of mass. Energy is equivalent to mass but energy is not mass. I still don't see why energy by itself should have gravity. I can't see the logic behind it. What am I missing?
You say that "it is inconceivable that energy does not cause spacetime to warp". Does that not imply that if it is energy that causes spacetime to warp that gravity is a force, not geometry?
I am sorry to labour the point but I really am trying to understand. If energy has gravity then at the moment of the big-bang, the universe was born with gravity. If energy does not have gravity then the universe was born initially without gravity.
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imatfaal
That was obviously a mistake and should have read "gravity and acceleration are the same".
Locally yes - gravity will always have a tidal component tho.
What is the reasoning behind the hypothesis that energy has gravity and what experimental evidence is there to confirm it?
The "hypothesis" is now generally accepted as a well tested theory - it is called General Relativity. It is as well tested as any theory in science.
I know that Einstein's field equations talk about the stress-energy tensor but what does this mean in non mathematical jargon. There must have been some logic that led up to it?
well yes the logic is based upon mass/energy equivalence
The alleged gravity of energy (light) being so weak that it cannot be measured. If so, then it is conceivable that energy does not have gravity?
Who says it cannot be measured? And no with physics as it is it is inconceivable that energy does not cause spacetime to warp.
General Relativity covers a lot of ground and I was specifically asking if energy has gravity. I have not been able to find any research confirming that it has been measured. All I have found are articles saying it is too weak to be measured. I agree that when looking at it from the mass/energy equivalence principle mass can be seen as energy and hence energy has mass and therefore gravity. But that is when looked at from the energy equivalence of mass. Energy is equivalent to mass but energy is not mass. I still don't see why energy by itself should have gravity. I can't see the logic behind it. What am I missing?
What you are missing I am afraid is a full physics education and a solid grounding in maths. Your argument from personal incredulity is not convincing
You say that "it is inconceivable that energy does not cause spacetime to warp". Does that not imply that if it is energy that causes spacetime to warp that gravity is a force, not geometry?
That is a complete non-sequitur. Mass/energy cause space time to curve - curved space time gives rise to the effects of gravity
I am sorry to labour the point but I really am trying to understand. If energy has gravity then at the moment of the big-bang, the universe was born with gravity. If energy does not have gravity then the universe was born initially without gravity.
Yes both your if..thens are correctly constructed - however the only one with experimental evidence to back it up is that energy curves space time and gives rise to gravitational attraction; but this is experimental evidence from a very different, colder, less denser and mass-dominated universe
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imatfaal
That was obviously a mistake and should have read "gravity and acceleration are the same".
Locally yes - gravity will always have a tidal component tho.
What is the reasoning behind the hypothesis that energy has gravity and what experimental evidence is there to confirm it?
The "hypothesis" is now generally accepted as a well tested theory - it is called General Relativity. It is as well tested as any theory in science.
I know that Einstein's field equations talk about the stress-energy tensor but what does this mean in non mathematical jargon. There must have been some logic that led up to it?
well yes the logic is based upon mass/energy equivalence
The alleged gravity of energy (light) being so weak that it cannot be measured. If so, then it is conceivable that energy does not have gravity?
Who says it cannot be measured? And no with physics as it is it is inconceivable that energy does not cause spacetime to warp.
General Relativity covers a lot of ground and I was specifically asking if energy has gravity. I have not been able to find any research confirming that it has been measured. All I have found are articles saying it is too weak to be measured. I agree that when looking at it from the mass/energy equivalence principle mass can be seen as energy and hence energy has mass and therefore gravity. But that is when looked at from the energy equivalence of mass. Energy is equivalent to mass but energy is not mass. I still don't see why energy by itself should have gravity. I can't see the logic behind it. What am I missing?
What you are missing I am afraid is a full physics education and a solid grounding in maths. Your argument from personal incredulity is not convincing
You say that "it is inconceivable that energy does not cause spacetime to warp". Does that not imply that if it is energy that causes spacetime to warp that gravity is a force, not geometry?
That is a complete non-sequitur. Mass/energy cause space time to curve - curved space time gives rise to the effects of gravity
I am sorry to labour the point but I really am trying to understand. If energy has gravity then at the moment of the big-bang, the universe was born with gravity. If energy does not have gravity then the universe was born initially without gravity.
Yes both your if..thens are correctly constructed - however the only one with experimental evidence to back it up is that energy curves space time and gives rise to gravitational attraction; but this is experimental evidence from a very different, colder, less denser and mass-dominated universe
What is this experimental evidence please?
I know that it is part of general relativity and general relativity is a well tested and tried theory. But what specific experimental evidence is there to confirm that energy curves space time.