Best intuitive explanation of space curvature/gravity

[Dennis P Brown]

For anyone wishing to see a very intuitive and well explained examples of why gravity is the curvature of space-time and not a force, here it is! The first ten minutes is a bit irrelevant except to review some standard (simple) ideas but the second half is both easy and extremely clear on what space curvature really is and how apples/objects react/fall. Without a doubt, the simplest, clearest but still very in depth explanation of how General Relativity creates gravity; and best of all, no math (well, they do mention Newton's force law.)

See: https://www.youtube.com/watch?v=OpOER8Eec2A

[Richard Hull]

There is of course no curvature of "space-time" without mass. Physical mass and mass alone is the source of gravity and curves "space-time" by its presence within space. No mass, no gravity and no curvature of space-time. How mass performs this feat is still a mystery, regardless of the Higgs which is a mere guess. Makes us feel smart and empowered to say. We can observe and say what happens based on observation (experiment). The mechanism behind what we observe in this case is a mystery. Root causes, have themselves, root causes and so on ad infinitum.

I observe my cat sometimes chasing its tail and think, how silly. At least it is smart enough to stop once it realizes it is a futile endeavor.

Of course I am not saying finding scientifically root causes is a futile gesture.....or is it? How far down the rabbit hole are we willing to go before we realize the hole closes behind us and runs in a circle. We seek to find something new in an unending run around the hole, imagining we feel we have come this far so let's go along a bit more. We can always make things up as we go along to explain that which we cannot.

Man is like a small child who says' Why? Once his query is answered to the best of our ability, he repeats, Why?

Richard Hull

[Dennis P Brown]

You are absolutely correct, Richard. Without mass (rest), space-time curvature is meaningless. This then creates the silly chicken-egg reasoning. No one likes that one but General Relativity(GR) is, well, what it is.

I do believe that I can prove this conjecture by Einstein and define what space-time curvature really is, in a physical sense that is meaningful to anyone. So that chicken-egg problem goes away.

So, over the last few months of working through some of the current research and my grad book on QM, I've made a great deal of progress and turns out Field Theory - when properly combined with GR - automatically creates what we call gravity.

Frankly, the creation of space-time curvature by mass is inescapable when light has a finite speed. For me, that aspect of finite light propagation causing space-time curvature to emerge from FT is the most interesting aspect of my derivation.

[Rich Gorski]

Just throwing a wrench in the works...I would think that light (massless photon) will curve space time due to the energy it contains. So its equivalent mass is E/c^2. A very very tiny mass equivalent indeed but yet it should curve spacetime. If this is true does that mean a black hole can be created just by a sufficiently intense beam of light ??

Rich G.

[Richard Hull]

Nice attempt at equivalence principle. There is no evidence that light or any form of EM radiation warps space-time. Mass warps space-time and thereby, bends all EM radiation accordingly.

EM radiation/photons interact only with the charged particles in matter. All EM radiation is solely due to charged matter interactions where a charged
matter particle is accelerated or decelerated. No chicken or the egg scenario here. No charged matter, no EM radiation. Matter cannot be created from EM radiation.

Don't be fooled by the 1.2mev + photon making an electron-positron pair. No 1.2mev photon just splits into matter. That photon must interact with charge matter. Most normally the electron shell. Only then do the electron and positron appear! In bulk matter, the 512kev positron is quickly annihilated to a 512kev photon. The 512kev electron speeds off to replace missing electron conservation of mass and energy is held for the universe.

Net result: photon hits atom field, Photon destroyed becoming a high speed positron plus a high speed electron (shared energy). Positron is destroyed along with another electron in matter. A new photon of lesser energy is created during annihilation. Newly created electron speeds off having difference in original photon energy and the new photon's energy.

The universe just traded and degraded photon energy by giving an electron kinetic energy of charge in motion. Universe matter mass balance, one fixed electron mass destroyed, one electron mass created at high speed.
Zero charge photon turns into +electron and normal negative electron, negative electron annihilates positron. Zero charge photon created at lower energy. Destroyed electron is replaced by created electron but is now a free charge with kinetic energy from that original photon.

Richard Hull

[Daniel Harrer]

There is no direct evidence for energy warping spacetime yet, but it must happen or the entirety of GR is wrong. That mass and energy are two sides of the same thing is fundamental, and this includes gravitational effects. I think it also follows from continuity arguments that would cause FTL signalling if curvature just "pops away" whenever two photons are formed from annihilation, but I haven't done the math.

There is also the concept of a Kugelblitz, a black hole made entirely of photons. One way we very optimistically might be able to create one.

Dennis: what do you mean by "GR" when you say it, combined with field theory, causes gravity? For me, gravity is already a quintessential part of GR?

[Dennis P Brown]

GR assumes that space-time curvature creates what we call gravity. Yes, it assumes mass curves space-time but does not account or explain it except to say it does. Gravity is not a force but a reaction by mass due to the 'curvature/time change due to - mass. A somewhat circular argument. To explain why objects accelerate towards massive objects is not so simple nor something that GR explains.

Richard, every point you make is 100% correct and actually, are critical elements that help explain what this space-time curvature really is.

[Rich Gorski]

Sounds like your arguing against GR.

In GR, The total energy of a particle, Etot = Ekinetic + Erestmass or (Etot)^2 = (pc)^2 + (moc^2)^2. This is included in GR as part of the first term (the mass/energy term T00) of the energy-momentum tensor Tuv (this is the left hand side of the Einstein field equation). The Tuv tensor describes the mass/energy/flux/pressure/shear that is responsible for the curvature of spacetime. Note that it includes (pc)^2 which is the energy of a massless photon. So if you believe in GR the massless photon indeed curves spacetime and in fact two photons should gravitationally attract each other... although the effect so so small that it is well beyond any experimental detection technique.

Rich G.

Ps. Daniel, thanks for your annihilation example.

[Daniel Harrer]

Dennis, I would say the second half, that the curvature "causes" gravity, does not need more explanation. It just comes from all the things inertially following geodesics in spacetime. So it is just Newton's first law, with a twist.

Hence the true question is why spacetime would "care" to react to masses at all. A simple, naive, yet incomplete answer is that mass-energy is just what we call the thing that corresponds to this bending of spacetime; the basic charge(s) of gravity. But that obviously doesn't explain multiple non-trivial relations between gravitational mass, inertia, the equivalence principle, and energy in all its various forms.

Getting back to my question: what is "mass" in your setup without already using GR? Or how does it emerge as a property of energy? And how does anything like, or similar to, the Higgs mechanism happen to give certain fundamental particles a positive rest mass? I am a mathematician, so feel free to throw math terminology at me.

[Frank Sanns]

These concepts are not so easily communicated between people because of the implication and complications. Several factors have been brought up.

Saying warping time and space due to gravity is a bit of a misnomer and also is not ubiquitously applicable. As brought up, there is something called the equivalence principle. It needs no mass to warp time and space; not my choice of explanation but consistent with the syntax in this thread.


Who is taking the trip and who is not during the effect of "gravity" is also important. The answer becomes, the one experiencing an acceleration. Clocks only run slow in a gravitational field if they are fixed in another reference frame, i.e. sitting on the surface of a massive planet. If in free fall with no atmospheric drag, there is no warped time and space to the one falling.

A photon still follows the same time space laws as the rest of us as perceived by us. It is however another beast entirely when it comes to its own behaviors.

[Dennis P Brown]

Daniel, you are now asking far different questions than issues on GR and its failings and what constitutes space-time curvature. If you are satisficed with the current "It just is" there is nothing wrong with that. But I am not. The tensors in GR are mathematical transforms that give correct answers but no insight into the why they occur. That, for me, is what I am concerned with.

I'll partly answer - the Higgs only creates 'real' mass because the effects of 'negative' mass makes no sense. The equations say such a mass would instantly accelerate and could travel faster than light. That is, the equations break down and that tells use they do not work for such particles or they do not ever come into existence. Take your pick.

I have no issue with mass nor the Higgs field. Those are questions that neither interest me nor have any bearing on my research efforts. That, maybe, is something you should investigate? However, speculation is not of any use in science when addressing specifics. One must use rigorous mathematical and physics based models using known reality to properly formulate any idea. Otherwise, it is just philosophy.

The issue of photons, while germane to GR, again, has no bearing on my work. Nor can anyone do an experiment that proves that photons are directly affecting space-time. As such, it is a interesting but always speculative idea.

As I've mentioned, gravity does not really exist (certainly not in GR) - the force we call gravity is the space-time curvature and that is what GR shows and defines as gravity. Mass, via no know explanation, causes space-time curvature. This in turns causes the mass to move along that 'world line'. That has been used to both explain and predict a vast array of physics. It fails in many areas and that is the issue. That is claimed to be the result of GR and QM being incompatible - that I intend to change.

Bottom-line; there is no explanation for either why space-time is curved by mass nor why mass follows said path; these are simple givens. Later, some physicist do believe (and I agree) that 'gravity's' acceleration effect on a mass is solely caused by time dilation near a larger mass. Some further believe this is a quantum effect.

I decided that these approaches and explanations are not good enough and have worked out, from first principles, both what the space-time curvature really "is", and what causes this to occur. Yes, both GR and QM (from FT applications) are required to explain these results but there is a physical bases. Yes, it is testable. No, it is not finished by a long shot

[Richard Hull]

There is no energy anywhere in the universe that is not created by charge exchange, nuclear or electronic, as part of all mass + binding energy locked down in mass OR by gravitationally created universal attraction, again, directly due to mass, and mass alone. These two potential energies and their interactions create 100% of all EM radiation which acts, in a passive, secondary, reactionary way to, itself, transport energy over vast distances to heat, move and disrupt charged matter. This can produce kinematic motion of charged particles creating new electrostatic potential energy.

No charged particles, no magnetism, no light, no EM radiation, no photons. No chicken or the egg here. No gravitation due solely to mass, no stellar fusion, no detectable space-time curvature. So very simple. The universe runs via potential energy exchanges. All photonic/EM radiation is a secondary created energy form and not, nor has ever been more than a force carrier. Binding energy is also a secondary creation read as mass but brought into being by gravitational-matter interactions.(fusion). Strong and weak forces cannot exist without matter thus are secondary. They have no meaning in a charged-matterless universe.

What is at the core of all this is that science struggles aimlessly trying desperately to avoid philosophy, while generating the next best thing to philosophy, theories! These theories, some so tightly held, by balled up mathematics that are crafted sometime by observational evidence. However, when new evidence forces a major theory or system to be called into question, its adherents run about is an insane effort to save it by more theoretical and mathematical machinations. I really get a kick out of both watching and listening to these "chicken littles" trying to save the web they have woven.

Again how far afield and down the rabbit hole can we lead ourselves into what often seems wild conjecture. All of this to find the root cause of all physical things and their interactions. As god is said to have spoken to moses..."I am that I am"
(I am not a religious person)

I'll stick with my first two paragraphs as a core knowledge of how the universe keeps in balance and on the move. It is unconcerned with we little mites riding a rock around an unimportant main sequence star.

Richard Hull