OK...this is Don Lincoln here. My name was invoked and a little bird came and suggested I pop in. I have not read all of the chat above.
Regarding gravity and belief. First, belief is a non-scientific word....or at least it has lots of really ridiculous connotations. When a scientist says that they believe in a theory, they're just being sloppy. (And I include me in that. But language is language and we do the best we can.) "Belief" to a scientist simply means in this context, that the theory is consistent with all relevant known data and we can take it as an approximation of the truth.
Now, on gravity. It's very clear that Einstein's formulation is more accurate than Newton's or, for that matter, any other suggested theory of gravity. It's also eminently clear that general relativity fails at small sizes and very high gravitational fields. For that, we will need a theory of quantum gravity. Some ideas have been put forward, but none have been validated in any way, meaning to all intents and purposes, we have no believable theory of quantum gravity.
However, given the established validity of general relativity, it follows that that when quantum gravity is evaluated for gravitational fields not strong enough to manifest their quantum behavior, that the predictions will be effectively identical to general relativity. From that, we can infer that the bending of spacetime will be valid in quantum formulations as well, although there may be additional explanatory insights.
Accordingly, I feel quite comfortable in saying that I believe in general relativity in the realm in which it is applicable. Similarly, I believe in Newtonian gravity in the realm in which it is applicable. After all, we shot the New Horizon probe to Pluto - traveling billions of miles, passing by several planets, and NASA hit a target 10 km in size. Newton works. Einstein works. Well, until they don't. That's all of science. Theories work as long as they work.
One other piddly point. Our current understanding of gravity is qualitatively different from the other known forces. Sure. Some of you have been discussing the meaning of the word force. Classically, it means something that has the potential to cause an object's velocity to change according to some reference frame. At the quantum level, it has a somewhat different meaning. There it means that the phenomenon can effect some sort of change, be it changing velocity or causing particle decay. The fact that the word has a nuanced meaning depending on the size scale at which it is being evaluated implies that the word is fuzzy and anybody trying to nail it down, will fail.
This brings up a more important point is that the mapping of words onto scientific concepts is a dangerous endeavor. It is highly unlikely that any word can be mapped into a concept so well that it is impossible to find an exception. There will aways likely be a qualification of some sort. Accordingly, don't hold onto words very hard. They will fail you. Instead, understand the more nuanced scientific principle for which the word is nothing more than an imperfect and ultimately inaccurate placeholder.
For the person who complained about the videos being at a commercial site. Well, I've worked for over three decades learning this stuff. I spent half a year writing the lectures, which comprise 12 hours of clearly-explained advanced science. I spent a week filming the project and many hours ensuring that the quality of the video and audio product was high.
And someone has the temerity to suggest that I and the production company shouldn't be compensated for that effort? It's like whining that someone won't come and paint your house. Go ahead - enroll in the streaming service - you will have access to an astonishing amount of knowledge and expertise, translated in such a way that non-experts can understand a portion of the more complex ideas.
BTW I was a solid presence at SPCF for a long time, but I will not be a regular here. I have just contracted my 5th or 6th book and that will take enough time that active involvement here is simply not in the cards.
Cheers....
