81–90 of 138 posts
Nothing has satisfied me between why gravity and magnetism are not the same thing. A ferrous material where the electron poles can be aligned show high forces. Most things are totally misaligned, which I believe creates gravity. No explanation on stackexchange or anything else convinces me. Most of the arguments feel egotistical to me.
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> Why though? It bothers me too, why? because it's circular reasoning: acceleration can't explain acceleration. > Would it help if the sheet were in a centrifuge? No, for the same reason. (You're imagining a tube-shaped membrane?) To make it worse, it's developing a wrong idea that hides the right and deeply strange idea: when an object passes a mass and its path seems to deflect what's really happening is that the o…
As a sibling points out, it’s not explanatory as much as a visualization. Or if it explains something it’s not gravity itself but a less familiar kind of geometry and a new concept of straightness where sometimes the shortest path is what we’d usually think of as curved. Seems fine. Little chance of understanding gravity until you can grasp the prerequisite concepts you’re going to describe it with. And anyway explai…
The actual description of gravity isn't hard to understand, it's just really strange. There is no good reason to introduce confusing and intrinsically incorrect models.
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Balls on sheet is a wrong model imo. It needs gravity to work and therefore doesn't explain gravity. I like to imagine a sponge. If you could somehow make dense lumps inside the sponge (may be apply heat in its center somewhere using microwaves?) everything around that lump will be feel a tension/attraction towards that lump. That's my mental model.
It's not trying to explain gravity. It's trying to visualize it.
Afaiu, the answer is that moving through time in a gravitational gradient makes you constantly “fall flat” on an x/time 2d graph due to time dilation gradient, thus affecting x and spatial momentum. Apparently mass affects time and time creates gravity. Idk if that’s a fringe idea or mainstream.
https://www.researchgate.net/publication/383609891_Gravity_M...
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As a sibling points out, it’s not explanatory as much as a visualization. Or if it explains something it’s not gravity itself but a less familiar kind of geometry and a new concept of straightness where sometimes the shortest path is what we’d usually think of as curved. Seems fine. Little chance of understanding gravity until you can grasp the prerequisite concepts you’re going to describe it with. And anyway explai…
Gravity is one of the fundamental forces, there's no recursion in it's definition, indeed we don't "define" it we describe it. The actual description of gravity isn't hard to understand, it's just really strange. There is no good reason to introduce confusing and intrinsically incorrect models.
Well, teaching is the usual reason, otherwise physics with trig would all just wait for calculus, and calculus wouldn't get covered before real analysis, etc. Incorrect, or more charitably "useful, prerequisite, & intentionally not rigorous" models are a pretty standard tool for walking students closer to real understanding. Clearly no one is proposing trampolines and bowling balls models because they are expecting to win a Nobel.
> The actual description of gravity isn't hard to understand, it's just really strange.
Hmm, Einstein thought it was pretty hard, and I didn't know that you and Witten had finished quantum gravity or the other latest and greatest.
> Gravity is one of the fundamental forces, there's no recursion in it's definition, indeed we don't "define" it we describe it.
Unpacking this to a first approximation it actually sounds like you're looking for The Truth instead of useful models, that you always know Truth when you see it, that you don't believe that apparently different descriptions can result in formally equivalent stuff. I'm also guessing that you might be strongly inside a "only cares about math because physics" camp whereas I sympathize more with "only cares about physics because math". Lots of interesting conversations in there, but it'll all just be philosophy at that point anyway and you probably wouldn't like it.
> Einstein finished his masterwork, the theory of general relativity, in 1915. He was 37 years old Interestingly if you look at the most popular programming languages they were created by someone 37.5 years old, on average [0]. [0] https://pldb.io/blog/ageAtCreation.html
That's not a great comparison. Einstein had already turned physics on its head and kickstarted several foundational paradigms in 1905, when he was only 25-26 years old.
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He comments on fields in which he’s unqualified, and his remake of Nova had a ton of unnecessary swearing. And goes on TV and talks about politics. That’s when he lost me.
Sagan was political, more so than Tyson. Sometimes science intersects with politics in ways that can’t be avoided. Nuclear proliferation, land management, etc. So how can you just turn off any scientist who touches politics? Or is it just a certain kind of politics that turns you off?
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> Some claim matter falling into a black hole never really does from the point of view of an outside observer. Such claims are wrong. The correct statement is that the outside observer never sees the matter reaching or falling inside the event horizon. But that's not because it never happens; it's because the spacetime geometry prevents light emitted at or beneath the horizon from getting back out to the outside obse…
In a hypothetical pure GR universe what you're saying is correct, but our universe also includes QM and that makes BH physics much more subtle, e.g.: https://en.wikipedia.org/wiki/Firewall_(physics) and we can't state things with such certainty...
In some ways, yes, but none of that changes the particular thing I said about BH physics.
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An electron-proton pair approaching each other will not necessarily form a hydrogen atom by emitting radiation. They could just scatter off each other, and if the impact parameter is large enough, this process could be modeled reasonably well by an analysis using classical relativity. Or, at high enough energy, other particles could be produced, which would require quantum field theory to model.
You can't just reject evidence like this though: electrons orbiting protons don't emit synchrotron radiation. So whatever else you want to the prize, you have to be able to reproduce this result.
Not in atoms, no. But I mentioned scattering, which is a different scenario.
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> An electron falling (electrostatically) toward a proton will reach the speed of light at some point. No, it won't. A correct relativistic analysis of the relative motion of the electron and proton will show their relative speed never reaching c, let alone exceeding it. You can't just plug numbers into Coulomb's Law for this case, because Coulomb's Law by itself is not relativistically correct. You need to use the f…
> You can't just plug numbers into Coulomb's Law for this case, because Coulomb's Law by itself is not relativistically correct. Sorry if this is a bit pedantic, but as someone trying to study this at the moment, I don't see this the same way and I'd like to validate my interpretation: You can just plug numbers into Coulomb's law, that part is correct. But then the problem of infinite velocities comes from interpreti…
Not if you want to get correct answers in problems that involve moving charges.
> relativity is necessary when things start to move 'very fast'
In electromagnetism, relativity is necessary whenever charges are in motion. Whether or not they are moving "ver fast" is irrelevant. Coulomb's Law is only valid when you have a charge at rest.
That said, the post I originally responded to obviously was talking about charges moving "very fast" since it claimed an electron falling towards a proton could exceed the speed of light.