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"A well-known scientist (some say it was Bertrand Russell) once gave a public lecture on astronomy. He described how the earth orbits around the sun and how the

"A well-known scientist (some say it was Bertrand Russell) once gave a public lecture on astronomy. He described how the earth orbits around the sun and how the sun, in turn, orbits around the center of a vast collection of stars called our galaxy. At the end of the lecture, a little old lady at the back of the room got up and said: "What you have told us is rubbish. The world is really a flat plate supported on the back of a giant tortoise." The scientist gave a superior smile before replying, "What is the tortoise standing on?" "You're very clever, young man, very clever," said the old lady. "But it's turtles all the way down!"" — Hawking, 1988 https://en.wikipedia.org/wiki/Turtles_all_the_way_down#History https://en.wikipedia.org/wiki/Turtles_all_the_way_down#Histo... https://en.wikipedia.org/wiki/Infinite_regress#Consciousness https://en.wikipedia.org/wiki/Infinite_regress#Consciousness edit: What if we talked about the idea rather than worried about who said it?

Houshalter 10y ago
I like that story, but it doesn't really apply to simulation hypothesis. Each simulated universe would necessarily have much less computing power than the level above it. We should expect there to be a limit on how powerful the computers we could build are, if we were in a simulation. Perhaps if we tried to build a simulated universe, things would start breaking, or events would happen to prevent it, or our simulation would just be shut down or reset.
- kbenson 10y ago
  You are assuming that all simulations run at the same speed. A simple way to look at it is if you have half as much computing power to apply towards the simulation, run it at half speed. This is undetectable from within the simulation.
  - Houshalter 10y ago
    Still, the universe only contains so much energy. There is a limit to the number of computations that can be done, and only a tiny percent of those can be allocated to our simulation.
    - kbenson 10y ago
      What makes you assume that a simulated universe has to match the base universe in every respect? It's entirely possible that the simulations, including us if we're in one, are running an extremely constrained version of the real universe, however many levels removed it is.
      - Houshalter 10y ago
        Well then that's not "turtles all the way down", it's just turtles 2 levels down. Second, the simulation argument is about our own universe someday making simulated realities. Assuming we are being simulated by a radically different universe is entirely different.
- solotronics 10y ago
  Or more computing resources would be automatically allocated to us.
  - Houshalter 10y ago
    But we can't have more computing power than the parent universe. And if we are only one simulation out of millions, we couldn't have more than a fraction of a percent.
- soylentcola 10y ago
  Or, to put it another way, "could god create an emulator that runs faster than the computer it's running on?"
- dragonwriter 10y ago
  > We should expect there to be a limit on how powerful the computers we could build are, if we were in a simulation. We should expect there to be a limit on how powerful the computers we could build are, if we are in a universe governed by the physical laws we now understand, whether or not we are in a simulation.
  - Houshalter 10y ago
    Yes, but a simulated universe would have bounds much lower than that. E.g. the laws of physics say that building a computer of size X is possible. But whenever we try to build it, it should mysteriously fail. Because the laws of physics aren't actually being simulated, any more than a video game simulates every particle and photon of light. It's just an approximation, and the computing power isn't there to actually simulate a computer that big.
    - dragonwriter 10y ago
      > Yes, but a simulated universe would have bounds much lower than that. No, it wouldn't. A simulated universe would have exactly the limits of the laws of the simulation, which would be exactly the physical laws of the universe as seen from within. > Because the laws of physics aren't actually being simulated, any more than a video game simulates every particle and photon of light. It's just an approximation The approximation (of some idealized laws of physics conceived in the external realiy) being simulated would be exactly the laws of physics observed in the internal reality of the simulation.
      - Houshalter 10y ago
        No, the simulation would not be able to fully simulate physics! It would need to cheat, a lot. A lot of sections would be unsimulated. When you observe the result of a physics experiment, the result would be made up on demand by some caretaker AI. Not by actually simulating physics.
        dragonwriter 10y ago
throwaway2016a 10y ago
He didn't say it was turtles all the way down though... he said there was a one in a billion chance we are the bottom turtle.

Houshalter 10y ago

I like that story, but it doesn't really apply to simulation hypothesis. Each simulated universe would necessarily have much less computing power than the level above it. We should expect there to be a limit on how powerful the computers we could build are, if we were in a simulation. Perhaps if we tried to build a simulated universe, things would start breaking, or events would happen to prevent it, or our simulation would just be shut down or reset.

kbenson 10y ago
You are assuming that all simulations run at the same speed. A simple way to look at it is if you have half as much computing power to apply towards the simulation, run it at half speed. This is undetectable from within the simulation.
- Houshalter 10y ago
  Still, the universe only contains so much energy. There is a limit to the number of computations that can be done, and only a tiny percent of those can be allocated to our simulation.
  - kbenson 10y ago
    What makes you assume that a simulated universe has to match the base universe in every respect? It's entirely possible that the simulations, including us if we're in one, are running an extremely constrained version of the real universe, however many levels removed it is.
    - Houshalter 10y ago
      Well then that's not "turtles all the way down", it's just turtles 2 levels down. Second, the simulation argument is about our own universe someday making simulated realities. Assuming we are being simulated by a radically different universe is entirely different.
solotronics 10y ago
Or more computing resources would be automatically allocated to us.
- Houshalter 10y ago
  But we can't have more computing power than the parent universe. And if we are only one simulation out of millions, we couldn't have more than a fraction of a percent.
soylentcola 10y ago
Or, to put it another way, "could god create an emulator that runs faster than the computer it's running on?"
dragonwriter 10y ago
> We should expect there to be a limit on how powerful the computers we could build are, if we were in a simulation. We should expect there to be a limit on how powerful the computers we could build are, if we are in a universe governed by the physical laws we now understand, whether or not we are in a simulation.
- Houshalter 10y ago
  Yes, but a simulated universe would have bounds much lower than that. E.g. the laws of physics say that building a computer of size X is possible. But whenever we try to build it, it should mysteriously fail. Because the laws of physics aren't actually being simulated, any more than a video game simulates every particle and photon of light. It's just an approximation, and the computing power isn't there to actually simulate a computer that big.
  - dragonwriter 10y ago
    > Yes, but a simulated universe would have bounds much lower than that. No, it wouldn't. A simulated universe would have exactly the limits of the laws of the simulation, which would be exactly the physical laws of the universe as seen from within. > Because the laws of physics aren't actually being simulated, any more than a video game simulates every particle and photon of light. It's just an approximation The approximation (of some idealized laws of physics conceived in the external realiy) being simulated would be exactly the laws of physics observed in the internal reality of the simulation.
    - Houshalter 10y ago
      No, the simulation would not be able to fully simulate physics! It would need to cheat, a lot. A lot of sections would be unsimulated. When you observe the result of a physics experiment, the result would be made up on demand by some caretaker AI. Not by actually simulating physics.
      - dragonwriter 10y ago

throwaway2016a 10y ago

He didn't say it was turtles all the way down though... he said there was a one in a billion chance we are the bottom turtle.