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Is our universe trapped inside a black hole? This JWS Telescope discovery

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Re: Is our universe trapped inside a black hole? This JWS Telescope discovery

#51

Post by cryptonector »

rocqua wrote: post #35
cryptonector wrote: post #31

Earlier quoted context omitted.

> How does this work with matter falling into 'our' black hole and hawkins-radiation leaving our black hole? We would see that at the edge (if we could see it) there's new mass and energy, but that would be obscured by what appears as the CMB for us. > Heck, Hawkins radiation means black holes can evaporate. Does that correspond to a universa collapsing? No, it corresponds to stuff disappearing from our universe, unt…

Hawking radiation can't just be stuff dissapearing, because the actual singularity can dissolve. Besides, where would the stuff even leave from? I could imagine the mass flux through our event horizon being related to the energy driving space expansion (or contraction). That only makes sense if time on the inside is related to time on the outside though. The idea that any mass that will ever fall into our black hole…

> Hawking radiation can't just be stuff dissapearing

It has to be the case that black hole evaporation means that mass-energy inside the black hole "disappears" from inside the black hole. It doesn't disappear from the rest of the universe, but if we are inside a black hole then we would "see" (if we could) that Hawking radiation means stuff disappears from our inside-a-black-hole-universe.

Re: Is our universe trapped inside a black hole? This JWS Telescope discovery

#52

Post by dvh »

perihelions wrote: post #23
fprog wrote: post #13

An alternate hypothesis which seems equally interesting, albeit for different reasons, is at the end of the article: > Another explanation for why the JWST may have seen an overrepresentation of galaxies rotating in one direction is that the Milky Way's own rotation could have caused it. > Previously, scientists had considered the speed of our galaxy's rotation to be too slow to have a non-negligible impact on observ…

I'm utterly confused what's going on. They're measuring galaxies' rotations by looking at images of the subset that are spiral galaxies, and checking which direction the arms spiral. They describe their image processing algorithm in their paper [0]. (it's around figure 3) How can local movement of stars within the Milky Way affect which way spiral galaxy arms are pointing? [0] https://academic.oup.com/mnras/article/5…

You cannot decide galaxy rotation by looking at it. Consider this gallaxy:

    _______   
    \   _ B\  
    /  /_\  \ 
    \  \_/   \
     \A____  /
           \/
Is A side closer to us, or is B side closer to us? You can't tell by just looking at it, if the B is closer that we are seeing bottom of the galaxy and it rotates CW. If A is closer than we are seing top of the gallaxy and it rotates CCW.

Re: Is our universe trapped inside a black hole? This JWS Telescope discovery

#53

Post by cryptonector »

Mertax wrote: post #26
perihelions wrote: post #23

Earlier quoted context omitted.

I'm utterly confused what's going on. They're measuring galaxies' rotations by looking at images of the subset that are spiral galaxies, and checking which direction the arms spiral. They describe their image processing algorithm in their paper [0]. (it's around figure 3) How can local movement of stars within the Milky Way affect which way spiral galaxy arms are pointing? [0] https://academic.oup.com/mnras/article/5…

There is no absolute direction for a galaxy’s spin—it’s always relative to the observer’s perspective. So I’d suspect they’re saying time and distance would need to be factored in rather than just looking at static images relative to our position today since our own spin may have caused a particular galaxy to appear to have been spinning in a different direction at another point in space-time

> There is no absolute direction for a galaxy’s spin—it’s always relative to the observer’s perspective.

Not entirely. The galaxy is bound by gravity and the stars rotate in the galaxy around its baricenter. We can compute how fast it must be rotating from the amount of visible matter. Enter dark matter and various complications, but still, you can tell that it's rotating and which way.

And for galaxies we see edge on we can use the difference if redshift on one end versus the other to tell which way it is turning.

Re: Is our universe trapped inside a black hole? This JWS Telescope discovery

#54

Post by Y_Y »

Mertax wrote: post #26
perihelions wrote: post #23

Earlier quoted context omitted.

I'm utterly confused what's going on. They're measuring galaxies' rotations by looking at images of the subset that are spiral galaxies, and checking which direction the arms spiral. They describe their image processing algorithm in their paper [0]. (it's around figure 3) How can local movement of stars within the Milky Way affect which way spiral galaxy arms are pointing? [0] https://academic.oup.com/mnras/article/5…

There is no absolute direction for a galaxy’s spin—it’s always relative to the observer’s perspective. So I’d suspect they’re saying time and distance would need to be factored in rather than just looking at static images relative to our position today since our own spin may have caused a particular galaxy to appear to have been spinning in a different direction at another point in space-time

I don't necessarily agree, in the presence of a universe (and under some reasonable cosmological assumptions) you can't just get rid of an observed rotation by a change of inertial frame. You can rotate along with it, but you'll produce a tell-tale fictitious force.

See e.g. https://en.wikipedia.org/wiki/Mach's_principle

Re: Is our universe trapped inside a black hole? This JWS Telescope discovery

#55

Post by AstralStorm »

dvh wrote: post #52
perihelions wrote: post #23

Earlier quoted context omitted.

I'm utterly confused what's going on. They're measuring galaxies' rotations by looking at images of the subset that are spiral galaxies, and checking which direction the arms spiral. They describe their image processing algorithm in their paper [0]. (it's around figure 3) How can local movement of stars within the Milky Way affect which way spiral galaxy arms are pointing? [0] https://academic.oup.com/mnras/article/5…

You cannot decide galaxy rotation by looking at it. Consider this gallaxy: _______ \ _ B\ / /_\ \ \ \_/ \ \A____ / \/ Is A side closer to us, or is B side closer to us? You can't tell by just looking at it, if the B is closer that we are seeing bottom of the galaxy and it rotates CW. If A is closer than we are seing top of the gallaxy and it rotates CCW.

Yes you can, by gravitational lensing of another body. Works exactly by triangulation in Lorentz space. You can thank Einstein for this feature of special relativity.

(Tricky part is deciding it's another body from a picture. You would need a second JWST preferably far in the other Lagrange point. Stereoscopy solves it directly. You can )

The thing is, you need another galaxy in the way to be sure, or a black hole. Theoretically our Sun can serve. [] Or the supermassive black hole in the center of our galaxy, but the sensitivity might be a bit compromised.

And long observation time.

[] https://en.m.wikipedia.org/wiki/Solar_gravitational_lens It's a bit hard to put satellites in the right place.

Re: Is our universe trapped inside a black hole? This JWS Telescope discovery

#56

Post by cwillu »

jacksnipe wrote: post #38
tremon wrote: post #33

Earlier quoted context omitted.

I don't understand this logic. To me, that's equivalent to saying "there's no absolute direction for which way a wheel spins, it's relative to the speed of the observer". Which makes no sense to me, because my definition of spin is measured against the axis of rotation of the object itself. I don't see how time-intermittent frame captures from our own position affect that interpretation. Or are we using an astonomy-s…

But what if you, the observer, are also rotating? What if you’re rotating faster than the thing you’re observing?

I don't see how that could be so prominent as to reverse the visible arms of a spiral galaxy, what am I missing?

Re: Is our universe trapped inside a black hole? This JWS Telescope discovery

#57

Post by ShinTakuya »

m3kw9 wrote: post #44
ShinTakuya wrote: post #9

Earlier quoted context omitted.

Black holes need not be dense. The black hole at the centre of galaxy M87 has the density of air in our atmosphere. The larger the black hole, the less dense it is. So that alone doesn't preclude us existing inside of one.

That’s news to me, I was taught that the mass collapses into it self it creates more gravity and more matter gets sucked in because the mass is so dense. So at which point does it become less dense?

Keep in mind that my own knowledge of physics is very rusty, so some of this is definitely making bad assumptions.

The density in the singularity (centre) of the black hole is in theory infinite. But the event horizon (the part where light no longer escapes) is not the singularity, it's simply where the gravity becomes so strong that light can't escape.

Think of it as the sun vs the planets - we're not in the sun, but we still feel its effects. The density of the solar system isn't the same as the density of the sun. This is bad analogy because the same mathematics/physics doesn't apply, but it should help you get the general picture based on your original assumption.

In general, the heavier the black hole, the less dense it is when measured from the event horizon. So in theory, it's possible to have a black hole so heavy that the event horizon contains the entire universe. In fact, the known universe is heavy enough to be a black hole 3 times the known radius of the universe. But as we know from stars that turn into black holes, just because something is heavy enough to be a black hole, doesn't mean it is one yet.

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