The quantum source of space-time • Hacker News Board

Re: The quantum source of space-time

#91

Post by padobson » Wed, Nov 18, 2015, 3:43 PM UTC

madaxe_again wrote: post #83

duaneb wrote: post #74

Earlier quoted context omitted.

Why do you (and others) tend towards arguments suggesting simulations? To me, the language here is important. Both simulation and computation imply (to me) a tool and a user of the tool. Even a broader interpretation of computation as, umm, the efficient transfer of precise information through spacetime in certain shapes (which is easily providable by our understanding of physics today) requires an observer to extrac…

A simulation doesn't mean that there is a simulator - just that what we consider real may be a projection of something else. As you say, the holographic universe principle can equally answer this. That said, the simulation argument strongly pushes in favour of a simulated reality - particularly when you consider that there is no need for it to be real time, or of the entire universe. In short if we ever gain the capa…

Hell, maybe the rotation of distant galaxies is off because they're just sprites

So there's probably some other simulation of our universe where they tried to do models, but it was too slow.

If not, then the simulator introduced a pre-mature optimization. The existential ramifications of such a development inefficiency are palpable!

Re: The quantum source of space-time

#92

Post by philipov » Wed, Nov 18, 2015, 4:02 PM UTC

pacala wrote: post #84

fizx wrote: post #42

Earlier quoted context omitted.

Say we're measuring spins of entangled particles with random entangled spins. So the real problem isn't that "when one is up, then the other will magically be up too." That could be accomplished with local hidden variables (e.g. shared seeds on a PRNG, or your examples). The real problem is that when you measure A in the "up" direction, and then B in the "10 degrees east of up" direction, then B seems to know that yo…

What if I have a million A/B pairs, measured in parallel. Each bit is 100 A measurements, 1 for up and 0 for down. Why is this not FTL communication of 10k bits?

Because you can't use it to pass information to someone listening to only a single end of the pair. You have to measure both particles to detect the correlation, or else all you're getting is random noise.

Imagine I'm flashing a light at you on and off, randomly. Some of the flashes aren't random and contain a message. To read the message, or even detect its existence, you have to know which flashes were random, and this is what observing both particles in an entangled pair allows us to do. There is no signal with only a single particle.

Re: The quantum source of space-time

#93

Post by criddell » Wed, Nov 18, 2015, 4:09 PM UTC

duaneb wrote: post #74

madaxe_again wrote: post #46

Earlier quoted context omitted.

I am a physicist... The most interesting (to me, at any rate) bit of this article are susskind's observations on computational complexity. As a precocious undergrad I put forward the idea that gravity and time dilation were the same thing, and both stemmed from the universe needing a constant amount of "time" to compute the interrelations between the particles in a volume of space - and if there were more particles m…

Why do you (and others) tend towards arguments suggesting simulations? To me, the language here is important. Both simulation and computation imply (to me) a tool and a user of the tool. Even a broader interpretation of computation as, umm, the efficient transfer of precise information through spacetime in certain shapes (which is easily providable by our understanding of physics today) requires an observer to extrac…

What do you feel about the mathematical universe hypothesis[1]? If I understand it correctly (and I probably don't), it says that the universe is literally mathematics. Not that it's a manifestation of mathematics or can be modeled by mathematics, but is 100% mathematics.

I think that fits the computation model and doesn't require an observer or operator.

[1]: https://en.wikipedia.org/wiki/Mathematical_universe_hypothes...

Re: The quantum source of space-time

#94

Post by HiLo » Wed, Nov 18, 2015, 4:10 PM UTC

madaxe_again wrote: post #46

taliesinb wrote: post #17

Here's a recent lecture by Erik Verlinde in which he tries to explain both dark energy and dark matter using entropic gravity: https://www.youtube.com/watch?v=PSYXt3Xu3xI I'm not a physicist, but he seems to be invoking similar ideas to Raamsdonk: that spacetime and gravity are emergent properties that boil down to entanglement somehow. But the loop quantum gravity people have been saying something like that for ages…

I am a physicist... The most interesting (to me, at any rate) bit of this article are susskind's observations on computational complexity. As a precocious undergrad I put forward the idea that gravity and time dilation were the same thing, and both stemmed from the universe needing a constant amount of "time" to compute the interrelations between the particles in a volume of space - and if there were more particles m…

This seems relevant. It's just a ride.

https://www.youtube.com/watch?v=KgzQuE1pR1w

Re: The quantum source of space-time

#95

Post by Retra » Wed, Nov 18, 2015, 4:13 PM UTC

dschiptsov wrote: post #73

dools wrote: post #65

Earlier quoted context omitted.

Mathematics doesn't imply anything. You can make a model using mathematics and then use it to make predictions, then test those predictions experimentally. By doing this a lot you can discover things and give them names like time, and proper time, and space and whatnot.

Is this a proof? Western philosophy, so far, succeed in separating these concepts as being a priory which is perfectly reasonable, considering that any sensory input which is subsequently used to train and condition our mind is coming serialized by out sense organ, so, for a mind, which is a result of conditioning by the senses, the notion of succession is a priory . Conditioning by shared physical environment gives…

What would you ask of a proof? If you're reading some text, how do you determine if the text constitutes a proof?

Re: The quantum source of space-time

#96

Post by crusso » Wed, Nov 18, 2015, 4:19 PM UTC

pacala wrote: post #84

fizx wrote: post #42

Earlier quoted context omitted.

Say we're measuring spins of entangled particles with random entangled spins. So the real problem isn't that "when one is up, then the other will magically be up too." That could be accomplished with local hidden variables (e.g. shared seeds on a PRNG, or your examples). The real problem is that when you measure A in the "up" direction, and then B in the "10 degrees east of up" direction, then B seems to know that yo…

What if I have a million A/B pairs, measured in parallel. Each bit is 100 A measurements, 1 for up and 0 for down. Why is this not FTL communication of 10k bits?

It's FTL communication of 10k random bits, whatever that gets you besides a great symmetric encryption key to share between you and the other end.

Re: The quantum source of space-time

#97

Post by Retra » Wed, Nov 18, 2015, 4:30 PM UTC

criddell wrote: post #93

duaneb wrote: post #74

Earlier quoted context omitted.

Why do you (and others) tend towards arguments suggesting simulations? To me, the language here is important. Both simulation and computation imply (to me) a tool and a user of the tool. Even a broader interpretation of computation as, umm, the efficient transfer of precise information through spacetime in certain shapes (which is easily providable by our understanding of physics today) requires an observer to extrac…

What do you feel about the mathematical universe hypothesis[1]? If I understand it correctly (and I probably don't), it says that the universe is literally mathematics. Not that it's a manifestation of mathematics or can be modeled by mathematics, but is 100% mathematics. I think that fits the computation model and doesn't require an observer or operator. [1]: https://en.wikipedia.org/wiki/Mathematical_universe_hypot…

Mathematics is a human language for studying the structure of various experiences. To say the universe "is" mathematics without saying what mathematics is doesn't really say much at all. You might as well say it's magic.

And, saying that it's a "mathematical structure" is just saying that it's a structure that humans can apply mathematics to model. So there's really no mechanism for this to be true, except in the trivial "the universe has structure" sense, which also tells you (basically) nothing, because humans can't even perceive things that don't have structure, nor can we reason about them.

Re: The quantum source of space-time

#98

Post by criddell » Wed, Nov 18, 2015, 4:58 PM UTC

Retra wrote: post #97

criddell wrote: post #93

Earlier quoted context omitted.

What do you feel about the mathematical universe hypothesis[1]? If I understand it correctly (and I probably don't), it says that the universe is literally mathematics. Not that it's a manifestation of mathematics or can be modeled by mathematics, but is 100% mathematics. I think that fits the computation model and doesn't require an observer or operator. [1]: https://en.wikipedia.org/wiki/Mathematical_universe_hypot…

Mathematics is a human language for studying the structure of various experiences. To say the universe "is" mathematics without saying what mathematics is doesn't really say much at all. You might as well say it's magic. And, saying that it's a "mathematical structure" is just saying that it's a structure that humans can apply mathematics to model. So there's really no mechanism for this to be true, except in the tri…

> Mathematics is a human language for studying the structure of various experiences

I think you are getting hung up on the semiotics of mathematics which is indeed a human construct. The idea of "1 + 1 = 2" is true no matter how (or if) you represent the idea.

> saying that it's a "mathematical structure" is just saying that it's a structure that humans can apply mathematics to model

That's not what the theory says (AFAIK). The mathematical universe hypothesis says that there is nothing in the universe, it's all just mathematics.

Edit: Think about it this way: if you could simulate a universe and in that simulated universe you modeled people and all the stuff around them, what would you tell those simulated people with their simulated free well what a table is made out of? It's all mathematics, right?

Re: The quantum source of space-time

#99

Post by TeMPOraL » Wed, Nov 18, 2015, 5:05 PM UTC

antimagic wrote: post #60

TeMPOraL wrote: post #18

Earlier quoted context omitted.

I think he means that the "entanglement" as understood by general public, i.e. as "I do something to particle A, and suddenly particle B changes" is an invalid way of reading the math; you didn't do anything to B, you merely figured out, by interacting with A, in which world you're in.

You see, this is the thing that kills me when thinking about the quantum world. The Many Worlds interpretation is so clean and obvious, except for one thing - it requires creating a new universe for each quantum entanglement event. Gah! Of course that does make me think about forking processes and copy-on-write, and the idea that our reality is just a simulation in a computer and that maybe creating new universes is…

I'm starting to think about this along the "zero-worlds interpretation" - i.e. there is only one world, but it's not based on discrete particles with states, but on probability distributions. We perceive the world as if it was already mostly simple, but it's because we too are entangled with stuff. There are no many worlds of particles, because particles are not the building blocks of a world. If you look at it from the hypothetical computer simulating us, it's kind of like storing the set of all natural numbers - you can store slices of it in lists (and then quantum entanglement under MWI works by figuring out in which list you are) vs. storing a generator function.

I admit I'm still in the process of learning and figuring this stuff out.

Re: The quantum source of space-time

#100

Post by Xcelerate » Wed, Nov 18, 2015, 5:23 PM UTC

lisper wrote: post #36

zby wrote: post #34

Earlier quoted context omitted.

'determine' does not mean 'change' - does it?

The issue is not so much with the word "determine" as it is with the word "instantaneously". You could say "Entanglement lets the measurement of one particle instantaneously frob the state of a partner particle" without knowing or specifying what the word "frob" means and you'd have the same problem: you're claiming that measuring one particle does something to the other particle, and does it instantaneously and, mor…

No one denies that when a measurement is performed, the measuring system and the measured system become entangled (and the aggregate system containing both continues evolving unitarily).

> When you "measure" the two halves of an EPR pair what you are really doing is performing two measurements on whatever system produced the EPR pair to begin with.

Here's the problem with that. Consider the measurements of a pair of space-like separated entangled photons. A choice can be made about the details of these measurements by the experimenters at the last second possible. For example, the rotation angle of a polarizer can be randomly chosen the instant before a photon strikes it, yet correlations with this choice show up in the other measurement that was taken far away. (Note that these correlations still don't allow you to send information faster than light.) But the "which angle" information was never contained in whatever system produced the two photons.