
Tangled Up in Spacetime - taralx
https://www.scientificamerican.com/article/tangled-up-in-spacetime/
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M_Grey
Scientific American has turned into such a rag... their recent bit about
"entangled black holes" was especially cringy.

It's Michio Kaku level of hand wavery and lack of rigor.

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Xcelerate
Meh... I thought the article did a decent job given the readership. The goal
of putting quantum mechanics on an information-theoretic foundation is indeed
a hot research topic lately.

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hyperliner
"In the AdS/CFT correspondence Maldacena showed that one can completely
describe a black hole purely by describing what happens on its surface. In
other words, the physics of the inside—the 3-D “bulk”—corresponds perfectly to
the physics of the outside—the 2-D “boundary.”"

Very interesting!

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ianai
I thought quantized spacetime had already been disproven below a testable
range? I.e. Any theorized particles wouldn't be seen by particle accelerators
smaller than say a solar system or drastically larger.

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jsprogrammer
The end of the article states that everything it discussed prior is only part
of a "toy". It is known that the toy being studied does not fully correspond
to our universe.

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empath75
Think of coming up with one of these theories like writing a complicated
computer program. Sometimes the whole task is too big to even think about, it
you sort of understand one part of it, so you work on getting that part sorted
out as best you can, and hope you can somehow figure out the rest of the
program later, and it'll be useful.

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anindha
I always thought of Einstein's theory of General Relativity as a model. For me
it doesn't explain the execution.

This to me makes more sense that at a quantum level there are discreet
particles that are being acted on according to relativity. I think of it more
like a CPU where this is a clock input.

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johncolanduoni
Quantum mechanics is pretty field oriented (doubly so for QFT, which is what
you're dealing with at that scale) so I don't understand why it would be any
less of a "model" than general relativity.

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anindha
Space and time are very macro concepts according to general relativity. It
doesn't actually explain how time elapses differently on one atom vs. another
atom only that it does.

I am traveling close to the speed to light how is my watching running slower?
How do the atoms in my watch know to run slower?

I am not suggesting that current quantum mechanics is more than a model, but I
think we are along the right path to figure out the answer to my above
question.

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soVeryTired
>I am traveling close to the speed to light how is my watching running slower?
How do the atoms in my watch know to run slower?

I think in some sense this is the wrong question to ask. Your watch isn't
running slower. The point is that if you're moving, you must be moving
relative to something else. Their watch will appear slower to you, and your
watch will appear slower to them. The counterintuitive part is that you're
both correct.

The reason all this comes about is that both observers measure the speed of
light as traveling at the same speed, but they can't agree on the path that
the light has taken.

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anindha
Yes, I should have been clearer. Running slower compared to a stationary
observer.

Your last point doesn't explain why or how time dilation occurs, just that we
know that the speed of light is a constant to all reference frames.

There is a famous experiment with three synchronized atomic clocks. Two were
flown in opposite directions around the globe the other stationary. The
eastward flown clock lost 59ns and the westward flown clock gained 273ns, both
relative to the stationary clock. The reason is that the clock flown eastward
is travelling faster since it is in the direction of the earth's rotation.
Measurements are consistent with the theory of relativity.

[https://en.wikipedia.org/wiki/Hafele%E2%80%93Keating_experim...](https://en.wikipedia.org/wiki/Hafele%E2%80%93Keating_experiment)

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soVeryTired
> Your last point doesn't explain why or how time dilation occurs, just that
> we know that the speed of light is a constant to all reference frames.

But that's what the light clock experiment [1] is all about. The two observers
see the light moving at the same speed, but one observer thinks the light
takes a longer path than the other observer does. If both observations are
equally valid, the inevitable conclusion is time dilation.

[1] [http://www.emc2-explained.info/The-Light-
Clock/#.WBxO8vnLdPA](http://www.emc2-explained.info/The-Light-
Clock/#.WBxO8vnLdPA)

