171–179 of 179 posts
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I don't remember any evidence supporting the simulation theory. Do you have a link?
I wouldn't say empirical evidence but here is one of many that keeps popping up in popsci news: https://www.scientificamerican.com/article/confirmed-we-live...
The simulation hypothesis is nothing except sciencey-sounding creationism/dualism.
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> I find myself becoming more and more sensitive to this basic mistake: We know relativity is wrong somehow. We know quantum mechanics is wrong somehow. Please don't use the word "wrong". Alchemy is wrong. Astrology is wrong. Relativity and Quantum Mechanics get many things right but are probably "incomplete" in the same way Newtonian mechanics wasn't wrong, only incomplete.
> Alchemy is wrong. Astrology is wrong. I think you are partly right. Quantum mechanics and general relativity are incomplete rather than wrong. I don’t think either has been falsified, it’s more that they are just useless in specific cases. This is in contrast with Newtonian mechanics, which implies Galilean transformation when changing reference frames, which looks right at our usual scales, but is plainly wrong in…
Of course they have. If you try to use SR or GR to predict how particles behave, you will get none of the quantum effects we have observed experimentally.
If you try to use QM or QFT to predict how the planets move* or at least how black holes move, you'll get predictions that don't agree with what telescopes have observed.
So yes, both of the theories have already been falsified.
* I have been told that there are some ways to account for gravity in regular QM in a way similar to GR that essentially work until you get to the kinds of strong fields near a black hole, where they break down again.
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> I find myself becoming more and more sensitive to this basic mistake: We know relativity is wrong somehow. We know quantum mechanics is wrong somehow. Please don't use the word "wrong". Alchemy is wrong. Astrology is wrong. Relativity and Quantum Mechanics get many things right but are probably "incomplete" in the same way Newtonian mechanics wasn't wrong, only incomplete.
astrology is not wrong, because it doesn't say anything provable. it just is. it's like saying poetry is wrong or paintings are wrong
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There could be a Newtonian speed limit if there was a drag force with a vertical asymptote in v through the medium that filled space.
I would call that something other than Newtonian physics, since that would constitute adding a term of some sort to some important equations, but I'm willing to agree this is just arguing about definitions and it doesn't really matter in the end since it still wouldn't be right. :)
Of course, the Michelson-Morley experiment proved that even if this substance exists, it can't be dragged around, so frame dragging can't be an explanation for the constant speed of light, making the whole idea unnecessary. Future observations predicted by SR and GR would probably not have been compatible anyway.
But, getting back to your point, if this ether had existed and had been the medium through which light propagates and had been draggable by moving objects, then this would not have been a contradiction or even modification of Newtonian mechanics.
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> QFT is one of the most successful theories we've created, but GR is still our best theory regarding gravity. There's still no evidence for the graviton. We probably need something else besides QFT to describe the nature of reality The evidence for QFT is orders of magnitude stronger than the evidence for GR, and the two are incompatible. The empirical evidence is simply the fact that gravity exists; if there's no g…
> The empirical evidence is simply the fact that gravity exists; if there's no graviton then how does gravity work? According to GR, gravity per se is a kind of illusion caused by the movement of particles in a curved space-time. The more basic effect is spacetime curving itself around mass(/energy). Now, whether this interaction itself is quantized or not (if the curvature comes in integer multiples) remains unknown…
Right, but you can't actually do physics (that is, QFT) in that model. You can model a universe made up of particles that have mass and no other properties, and, uh, that's it.
> Now, whether this interaction itself is quantized or not (if the curvature comes in integer multiples) remains unknown. It is very much possible that gravity/space-time curvature is a different kind of effect than the other three fundamental interactions, and that it is not in fact qunatized, so there is no graviton.
I mean, yes, but in that case what is it? I would love for someone to come up with a non-graviton model that describes gravity while remaining compatible with QFT. But unless and until someone actually comes up with that model, gravitons are the best we can do.
> And unto string theory, the problem with it is that it doesn't explain anything new. It posits some ideas of how gravity might work in a qunatized form, but any actual tests of the correctness of those calculations requires studying a black hole up close, which won't happen very soon.
Directly observing both mass and non-mass aspects of particles at the same time is hard, sure. But we know that particles exist and have both mass and charge (and colour and all that)! They must in fact be subject to both QFT and gravitational effects at the same time. Yes, I can't immediately show that up on my desk in the lab, but I'm deeply uncomfortable with "ignore gravity unless you're working with big stuff, and then if you're working with big stuff ignore the whole rest of known physics and use this radically different theory (that, again, fundamentally contradicts the entire rest of known physics) to model what it's doing". I mean, yes, it does work for all the experiments we can currently do. But it's not at all a satisfactory model of how the universe actually works.
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Come on! I make a serious effort to be precise here, and you just don't seem to give a damn. Time is a word , and I'm trying to establish the absolute minimum common sense rules for using that word. Obviously we have to use other words to do that, words like "event", "cause" and "order" (note, not "object"). But that's OK, the point is to explain what we mean by these words in relation to each other. To answer your q…
So the idea is to assign a different "time" to each event. It's very different from physics, because physics assigns the "same" time to multiple events. In Newtonian Mechanics, everyone agree to assign the same time to the same collection of events. In Special Relativity, the same time is assigned to different collections of events by different observers. In General Relativity, it's more complicated. Back to your ori…
> Does each event get a different place, of places can be shared between events?
Why is this even a question? It is obvious from the definition that two events can happen at the same place at different times.
The theory instead (wisely) says nothing about events happening at the same time.
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There is a distance-free notion of time which predates, and necessarily predates, all experimental theories of time. This is (loosely after Kant): * Every thing that happens, happens at a time. Let's call those things "events" from now on. It's nonsense to claim that a thing happened, but never (at any point in time) happened. * Every event happens in a place. It's nonsense to say that a thing happened, but nowhere h…
Points 1,2,4 imply absolute Newtonian space and time. They are completely and utterly wrong. Einstein showed us this more than 100 years ago - please keep up.
They perfectly match the idea of events as 4D points in Minkowsky space time. Points 1 and 2 are matched by describing any event by its (x, y, z, t) coordinates in some reference frame. Point 4 is matched by the fact that the Lorrentz transform preserves the ordering by t of events which are timelike separated.
Many seem to forget that even in relativity, all observers agree on the order of events that are close enough together in space. For example, any possible observer agrees that the pyramids are older than Hacker News (though they will disagree on how much older).
What the GP is saying is that this framework definition of time is in fact a series of requirements that any physical theory of time must fulfill to be recognizable as talking about time. That is, any theory that doesn't match those criteria is not talking about the same thing we are when we say time.
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I think most people can relate to sometimes feeling like their experience of time is incongruent with objective clock time. We're educated and socialized to believe that it is our perception that is incorrect, because the clock is right. Some philosophers and other types of scholars would question whether we should cede all sense of reality to that which can be objectively measured. You might say that there's no one…
This is like claiming that there is no physical temperature because "hot" water for a bathtub is different from "hot" water for a tea (and different from "hot" air during a summer day). Perhaps we should use two different word for the " perceived time " and for the " clock time ". The good days, when I go to sleep all the night appears to go away in an instant, but it isn't. It's more useful to have a physical define…
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So the idea is to assign a different "time" to each event. It's very different from physics, because physics assigns the "same" time to multiple events. In Newtonian Mechanics, everyone agree to assign the same time to the same collection of events. In Special Relativity, the same time is assigned to different collections of events by different observers. In General Relativity, it's more complicated. Back to your ori…
The t coordinate of 4D Minkowski space-time perfectly corresponds with the definition that the GP was making. As does the t in Newtonian mechanics. > Does each event get a different place, of places can be shared between events? Why is this even a question? It is obvious from the definition that two events can happen at the same place at different times. The theory instead (wisely) says nothing about events happening…
> Why is this even a question?
It's very strange that two events can not share the same "time". This is not the usual definition of time in physics [1]. So it's a natural question if the same strange property apply to "place".
Also, the definition of "time" in a world with special relativity makes it necessary to include (x,y,z) so "time" includes all the information included in "place". Why is it necessary to have both concepts?
[1] I think it gets more complicated in General Relativity, but I never took that course :( .