What awful AI-generated illustrations. Anyway, is there any justification for treating spacetime as a smooth manifold, except for mathematical tractability?
Yes. GR does it and GR gives good descriptions for a lot of observed phenomena.
New theory claims to unite Einstein's gravity with quantum mechanics
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Re: New theory claims to unite Einstein's gravity with quantum mechanics
#42A wonderful, bold, and colorful idea, already thought through carefully. And 5000:1 odds! It'll be more interesting how many more dozens of minds will find more testable consequences. Is it too much to hope that some untestable ideas will deservedly die?
Re: New theory claims to unite Einstein's gravity with quantum mechanics
#43Our present day understanding of the universe is rudimentary at best and will be rocked with each new device invented to reveal its nature to us.
When we explode a nuclear bomb here how far away in the universe would it be visible or detectable?
If there were a highly developed civilization would they not be listening for this background noise to detect when a civilization had reached the nuclear point and used it for exploding a bomb?
Re: New theory claims to unite Einstein's gravity with quantum mechanics
#44What awful AI-generated illustrations. Anyway, is there any justification for treating spacetime as a smooth manifold, except for mathematical tractability?
They're not AI generated, there's literally artist credits in the picture captions.
Re: New theory claims to unite Einstein's gravity with quantum mechanics
#45This is a question I've been asking myself (probably due to a lack of understanding and knowledge) and this theory seems to hint at something similar: why do we assume spacetime to be homogenous in its nature? Here they seem to say that on some quantum level spacetime could vary drastically. Couldn't then dark matter be explained by some variations on a large scale? Like giant "wrinkles" in spacetime? They would then…
Science had fared quite well so far with the assumption that the laws of physics are largely the same no matter where and when we are. There would have to be very strong evidence to throw that out. And the immediate next problem is that it actually wouldn't explain much. The immediate next question would be "why is spacetime behaving this way".
Ultimately it's just a way to say, "well, there is simply more gravity there". I was also thinking of the "why" and I'd say because when the universe expends, or initially expended, it didn't happen homogeneously. In my opinion it's more realistic that spacetime isn't homogeneous than that it is.
Re: New theory claims to unite Einstein's gravity with quantum mechanics
#46This is a question I've been asking myself (probably due to a lack of understanding and knowledge) and this theory seems to hint at something similar: why do we assume spacetime to be homogenous in its nature? Here they seem to say that on some quantum level spacetime could vary drastically. Couldn't then dark matter be explained by some variations on a large scale? Like giant "wrinkles" in spacetime? They would then…
Small nitpick on choice of words here - homogenous probably isn't the right word to use, instead the correct term is probably invariant.
The universe appears homogenous at various scales, meaning it's self-same within some amount of tolerance across itself. The distribution is homogenous. That's different from invariance, the assumption that a variable (in this case an intrinsic property such as mass) remains unchanged over time for a given subject of study, such as a particle.
Even if a given property can vary from subject to subject (even wildly), the sum of all subjects could still appear homogeneous in their distribution.
>why do we assume spacetime to be homogenous in its nature?
Because it's distribution appears to be consistent, at least as far as we can measure. That's not the same thing as objects at the quantum scale being invariant (or variable) in some way that we currently think is the opposite.
>Couldn't then dark matter be explained by some variations on a large scale? Like giant "wrinkles" in spacetime?
Considering the scales at which these fluctuations would have to occur for us to have not already measured them I'm doubtful they could build up to anything like that, even in aggregate and random patterns.
>They would then behave as pseudo black holes, or more like "black trenches", that lead to the structures we see today in the universe. The structures seem to have more mass than what we can actually see, but are in fact just placed in locations that behave differently gravity wise?
I don't think I'm really qualified to answer on how possible this interpretation is, but with the confirmation of gravitational waves a few years back we confirmed another piece of Einstein's theories and seem to have a good grasp on the observational effects of gravity at least. There was a recent announcement about mapping of the Gravitational Wave Background [0] using pulsars spread across the galaxy that was super cool too you might be interested in that I would say is related to this question.
The real answer is that theories like this require quite a bit of work to manipulate existing and complex math, and that you'd need someone who can translate an idea like yours into a mathematical model that fits with our observational data. That's an exceedingly difficult thing to do, as evidenced by the last 70ish years of physics.
[0]: https://www.space.com/gravitational-wave-background-universe...
Re: New theory claims to unite Einstein's gravity with quantum mechanics
#47What awful AI-generated illustrations. Anyway, is there any justification for treating spacetime as a smooth manifold, except for mathematical tractability?
They're not AI generated, there's literally artist credits in the picture captions.
Perhaps they're post-edited somewhat but there isn't a way you're convincing me those are fully handmade. Look at the nonsensically warped tiles. Look at the rods suspending some of the globes but not others in a random fashion, look at the illegible "writing".
Re: New theory claims to unite Einstein's gravity with quantum mechanics
#48A wonderful, bold, and colorful idea, already thought through carefully. And 5000:1 odds! It'll be more interesting how many more dozens of minds will find more testable consequences. Is it too much to hope that some untestable ideas will deservedly die?
That which can be destroyed by the truth should be.
Re: New theory claims to unite Einstein's gravity with quantum mechanics
#49Earlier quoted context omitted.
I find that it saves time to just start by assuming the experts haven't thought of X because of how many times I've seen assuming that they _have_ thought of X turn out to be a poor assumption, across many domains.
That’s incredibly specious reasoning.
Probably gets a better result than the alternative though. ;)
Re: New theory claims to unite Einstein's gravity with quantum mechanics
#50> and this scale can be determined by another experiment where we test how long we can put a heavy atom in superposition of being in two different locations."
Im a physics noob, but does this imply the theory helps explain why we usually only see quantum effects on the mucroscopic scale, since it says something about how heavy objects cant be put in superposition?