You can watch three videos on Einstein's theory of gravity explaining "how gravity REALLY works" and get different answers. Two are claiming objects fall to earth due to "time dilation" (the change in clock synchronization at higher altitudes or speeds), while the other claims it is because we on earth are accelerating upwards at 9.82 meters per second, an even more absurd idea for obvious reasons on a spherical earth. https://www.youtube.com/watch?v=PjT85AxTmI0
If those are the best explanations these top minds can come up with, the only real conclusion is that Einstein's theory fails to explain the most basic examples of observable gravity. Namely you drop something and it falls to Earth, or you jump and fall back down to Earth.
I'm not saying Einstein did this intentionally, or because he was a big bad evil Jew. His theories did (apparently anyway) get several predictions right or right enough to make it look valid. But all it takes is one major flaw to invalidate the theory and go back to the drawing board. Or do what modern scientists do and keep doing mental gymnastics to avoid doing any useful and original work.
Physics has probably been set back half a century by people clinging to this idea for too long. It may have some true elements, but it is conceptually wrong and mathematically flawed. It relies on undefined hocus pocus (space-time curvature) that has led scientists (particularly astronomers) to very erroneous understandings of the universe.
Gravity isn't properly understood in physics (i.e. modelled). Modelling gravity in current thinking of mainstream physics would require an experimental detection of a particle/wave (depending on the physics model), that they've been trying hard to find and have utterly failed.
Thus, we can't say we measure gravity or know what causes it, we can just measure the effects of what we model as gravity and then we call that thing gravity itself. Silly, yes. And then we model the effects mathematically (and try to explain them conceptually, often using poor metaphors).
The video in question makes an argument that gravity is the effect of mass-energy density distributions causing actual space-time curvature (without reference to time dilation).
This does not invalidate Einstein's theory of gravity aka general relativity, although there are other arguments against it.
Remember, it's just a model, not reality.
So far Einstein's theory of gravity aka general relativity has worked "well enough" for so many applications that it has been used.
What it doesn't solve are the conundrums in classical, relativistic and quantum experiments, which are many.
That's why there is a constant search for a better theory of general relativity and for a better theory of universal gravity.
But so far, none that I can find or am aware of, have been able to include all the calculable predictive power of previous models and extend them beyond those, while solving through equations the aforementioned experimental conundrums.
There are many conceptual alternative models for gravity, relativity and even unified physics (combining all of the so called forces), but none of them are at the level of mathematical equations in such a way that they surpass the previous models equations in predictive power of testable experiments in non-ambiguous, useful and testable ways (i.e. they correlate with reality better in all aspects).
For example, one of my hobby interests, topological geometrodynamics (TGD) solves many of the problems conceptually, but doesn't have usable equations to go beyond the current models in it's predictive power.
Many of the string/super-symmetry models branch out to too many possible equations and not mathematically testable (so "not even wrong").
Many of the alternative mathematical models that try to replace the general relativity model of gravity don't match the current measurements (MOND, aQal, TVS, etc).
For me the most abhorrent thing about general relativity (of Einstein) is the outcome that comes out of it : dark matter and dark energy.
They don't exist. We can't measure them, we've been looking for them and they supposedly fill 95% of known universe. This is just stupid.
Most likely dark matter/energy are just epiphenomena of using wrong equations to model reality in a wrong way. Like epicycles of the earth-centric solar system: unneeded complications that mask the true reality of how things are. Latest maps of energy distribution in the measurable universe point out that Einstein's theory of relativity is wrong.
Great, but what is the better mathematical model that would give everything the Einstein's theory does and still mathematically predict correctly all the latest findings and the rest of the experimental conundrums?
We haven't found it yet (not in the mainstream at any rate).
Remember all maps are wrong, some are useful in some situations.
And I'm by no means a great fan or defender of Einstein.
If I find a better working mathematical model, I will immediately switch over to that.
Yes I said the two others used time dilation, but the video I cited (which references those other videos as being wrong) said that it was due to the ground accelerating upward towards the falling object at 9.8 meters per second, which I pointed out is absurd. Both explanations are conceptual absurdities.
That's the problem though, there isn't. The vast majority of physicists just accept it as fact and try to build upon it from there, building entirely erroneous and sometimes well funded fields of research.
Because few point out these flaws this "constant search for a better theory" is rare and even ostracized by mainstream science. That is what holds physics back.
Dark matter/energy don't 'come out of' Einstein's equations. Dark matter is based on observations of how galaxies rotate. Dark energy is based on the red-shift of light from distant galaxies. If you use a 'tired light' hypothesis, then dark energy disappears (although other problems pop up!).
Well, yes and no.
The equations from Einstein's general relativity can NOT account for the observation of the mass / energy distribution in the universe.
So, out of this discrepancy grew "dark energy and matter" as otherwise the Einstein's theory would have been proven wrong, because the equations didn't predict that outcome.
So, voila! Dark energy / matter, to keep the failed model going.