4 ms·

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 unde

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 more time would be needed as the graph of particle interactions would grow non-linearly - and therefore time "slows down" in a matter (information) dense area of spacetime. What really got me gunned down was then going on to argue that this suggested a simulated universe, running in a substrate. Either way, interesting to see someone else who actually has some clout having similar ideas.

bytelayer 11y ago
This is a fascinating idea. Could you elaborate on how you think the additional computational complexity would give rise to attraction between particles in matter-dense regions?
- madaxe_again 11y ago
  Spacetime just stretches to reduce the effective density in a flat universe and maintain an effectively constant information density - thus gravity and time dilation.
sawwit 11y ago
Why does it imply a simulation? Perhaps it can be explained by an anthropic argument: Perhaps the kind of mechanics behind spacetime in which time evolution is computed in a stepwise manner depending on density are extraordinarily more likely because they somehow allow for much simpler mechanics (sets of laws with lower entropy are more likely to be the ones we find ourselves in, especially so if we assume that all non-physical sets of laws are realized as well, so that the impact of such a difference in entropy on the probabilties could be vast).
hellofunk 11y ago
Beautiful stuff, man. One of the more interesting questions I've seen asked in my casual hobby readings lately is: "Is the Universe quantized?" Meaning of course, is there a final limit to how small things get, and, with the passing of time, does it flow freely or pass in very tiny quantized periods?
- simonh 11y ago
  I don't see how that would work with length contraction and time dilation. A unit quantum length object in my frame of reference would have different length to one in a frame at motion relative to mine, and time for it would pass at different quantum clock ticks. I don't see how a universe like that could work when it came to interactions between moving particles.
  - AnimalMuppet 11y ago
    You're assuming that the Lorentz contraction applies unchanged as you move to the Planck length. That's not a given.
- progman 11y ago
  > is there a final limit to how small things get AFAIK yes, the limits are known as Planck Constants. It means that we are living in a digital universe. https://en.wikipedia.org/wiki/Planck_constant https://en.wikipedia.org/wiki/Planck_constant There are also conjectures about a _holographic_ universe. https://en.wikipedia.org/wiki/Holographic_principle https://en.wikipedia.org/wiki/Holographic_principle https://www.youtube.com/results?search_query=holographic+universe https://www.youtube.com/results?search_query=holographic+uni...
  - flatline 11y ago
    The existence of the Planck length does not imply quantized spacetime, which is still very much an open question in the field of physics. To the best of my knowledge most models still posit a continuous spacetime. cf. https://www.quora.com/Is-time-discrete-or-continuous https://www.quora.com/Is-time-discrete-or-continuous
duaneb 11y ago
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 extract the computation from the otherwise non-semantic system. It definitely makes sense to think of the universe as a projection of a higher dimension, or a holograph, or however you want to look at it, but that's a far cry from implying a simulation. EDIT: hologram -> holograph
- madaxe_again 11y ago
  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 capability to accurately simulate a small corner of the universe, then it stands to reason that someone further up the hylaean flow (apologies to Stephenson) also has. Hell, maybe the rotation of distant galaxies is off because they're just sprites ;)
  - padobson 11y ago
    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!
- criddell 11y ago
  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_hypothesis https://en.wikipedia.org/wiki/Mathematical_universe_hypothes...
ThomPete 11y ago
Isn't that what Wolfram is also getting at with his irreducible complexity concept? I wonder if the trick about this is not really to find a true explanation but the right perspective and more and more simulation seems to be a very valuable perspective to put on this. Disclaimer — I am not a physicist so apologies if my question is stupid.
HiLo 11y ago
This seems relevant. It's just a ride. https://www.youtube.com/watch?v=KgzQuE1pR1w https://www.youtube.com/watch?v=KgzQuE1pR1w

bytelayer 11y ago

This is a fascinating idea. Could you elaborate on how you think the additional computational complexity would give rise to attraction between particles in matter-dense regions?

madaxe_again 11y ago
Spacetime just stretches to reduce the effective density in a flat universe and maintain an effectively constant information density - thus gravity and time dilation.

sawwit 11y ago

Why does it imply a simulation? Perhaps it can be explained by an anthropic argument: Perhaps the kind of mechanics behind spacetime in which time evolution is computed in a stepwise manner depending on density are extraordinarily more likely because they somehow allow for much simpler mechanics (sets of laws with lower entropy are more likely to be the ones we find ourselves in, especially so if we assume that all non-physical sets of laws are realized as well, so that the impact of such a difference in entropy on the probabilties could be vast).

hellofunk 11y ago

Beautiful stuff, man. One of the more interesting questions I've seen asked in my casual hobby readings lately is: "Is the Universe quantized?" Meaning of course, is there a final limit to how small things get, and, with the passing of time, does it flow freely or pass in very tiny quantized periods?

simonh 11y ago
I don't see how that would work with length contraction and time dilation. A unit quantum length object in my frame of reference would have different length to one in a frame at motion relative to mine, and time for it would pass at different quantum clock ticks. I don't see how a universe like that could work when it came to interactions between moving particles.
- AnimalMuppet 11y ago
  You're assuming that the Lorentz contraction applies unchanged as you move to the Planck length. That's not a given.
progman 11y ago
> is there a final limit to how small things get AFAIK yes, the limits are known as Planck Constants. It means that we are living in a digital universe. https://en.wikipedia.org/wiki/Planck_constant https://en.wikipedia.org/wiki/Planck_constant There are also conjectures about a _holographic_ universe. https://en.wikipedia.org/wiki/Holographic_principle https://en.wikipedia.org/wiki/Holographic_principle https://www.youtube.com/results?search_query=holographic+universe https://www.youtube.com/results?search_query=holographic+uni...
- flatline 11y ago
  The existence of the Planck length does not imply quantized spacetime, which is still very much an open question in the field of physics. To the best of my knowledge most models still posit a continuous spacetime. cf. https://www.quora.com/Is-time-discrete-or-continuous https://www.quora.com/Is-time-discrete-or-continuous

duaneb 11y ago

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 extract the computation from the otherwise non-semantic system. It definitely makes sense to think of the universe as a projection of a higher dimension, or a holograph, or however you want to look at it, but that's a far cry from implying a simulation. EDIT: hologram -> holograph

madaxe_again 11y ago
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 capability to accurately simulate a small corner of the universe, then it stands to reason that someone further up the hylaean flow (apologies to Stephenson) also has. Hell, maybe the rotation of distant galaxies is off because they're just sprites ;)
- padobson 11y ago
  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!
criddell 11y ago
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_hypothesis https://en.wikipedia.org/wiki/Mathematical_universe_hypothes...

ThomPete 11y ago

Isn't that what Wolfram is also getting at with his irreducible complexity concept? I wonder if the trick about this is not really to find a true explanation but the right perspective and more and more simulation seems to be a very valuable perspective to put on this. Disclaimer — I am not a physicist so apologies if my question is stupid.

HiLo 11y ago

This seems relevant. It's just a ride. https://www.youtube.com/watch?v=KgzQuE1pR1w https://www.youtube.com/watch?v=KgzQuE1pR1w