
Ask HN: Assume the universe is a simulation. Why is c the speed of light? - vinaybn
Is it the processor&#x27;s clock-speed, always constant?
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CM30
Why a technical reason? Maybe it's a deliberate design decision, like how the
physics are set up in a video game. Maybe in this sort of scenario, they did
some playtesting and found that setting light to that speed made the game more
'enjoyable'.

Then again, it could be a way to cover up for a lack of content. Set the speed
of light to be faster, and it might theoretically make it so a species with
massively advanced technology could reach the edge of the universe. More
convenient and realistic than an invisible wall.

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networked
A connection between the simulated universe's speed of light and its host
CPU's clock speed would imply _real-time_ simulation. I see no reason why that
would necessarily be the case for a simulated universe; most research-grade
physics simulations humans run today aren't real-time. (They would be real-
time or faster if we had the hardware to run them that way — I imagine a
sufficiently accurate physics "REPL" would help a researcher tremendously —
but we make do without them.)

~~~
vinaybn
This doesn't make sense to me. Assuming this is a simulation, real-time isn't
"real" time.

~~~
networked
By "real-time" above I mean from the perspective of whoever runs the
simulation. Compare: [https://en.wikipedia.org/wiki/Real-
time_simulation](https://en.wikipedia.org/wiki/Real-time_simulation).

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brudgers
The puzzlement consists of using "universe" in two incompatible contexts
without paying clear attention to the distinction between the contexts.

The first context is the ordinary one in which the universe is roughly the
container for everything that is including ourselves.

The other context is one in which the universe is a simulation of a container
for everything that is including ourselves that is indistinguishable by us
from an actual container for everything that is including ourselves.

It's fine to use the latter definition, so long as one recognizes that the use
is very odd and problematic and any conclusions one draws while using it are
simulated conclusions about the simulated container and not conclusions about
the actual container for everything that is including ourselves. To put it
another way, if the universe is a simulation then "light" and "speed" and "C"
refer to elements of the simulation and need not have a one to one
correspondence to entities in the actual universe. Human knowledge can only be
knowledge of the simulation.

Our knowledge is limited to things it is possible for humans to know. If we're
in a simulated universe, then we can only know about the simulation.

~~~
iyn
I have a similar view, but at the same time I still have a little bit of hope
that even if the universe was a simulation, there would be some way to somehow
go outside the simulation (e.g: by 'thinking', if that would make sense, about
outside-the-simulation concepts; something like escaping the VM). But it's
kind of an emotional reaction to the realization of the limits of one's
mind/perception ;).

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kazinator
The question is too simplistic, because, within the simulation, the speed of
light appears constant in different reference frames that move relative to one
another. The simulation doesn't favor any particular reference frame; it's a
supervisor over all possible reference frames, so to speak.

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teovall
Perhaps the Universe is simulated by a distributed computing system. The speed
of light could ensure that state remains consistent throughout the system
without requiring synchronization of all of the nodes. Only spatially adjacent
nodes need to communicate with each other and the speed of light could be
tuned such that the bandwidth limit between the nodes would be never be
reached.

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fallingfrog
If the universe is a simulation, it would have to be on an analog computer
which doesn't have a clock speed as such. Or a digital computer running
sufficiently tiny time steps to be indistinguishable from an analog computer.
In either case I don't think c is directly related to "clock speed". I'm not a
good enough physicist to tell you what it does mean. That's my feeling anyway.

~~~
theSage
I would be inclined towards digital due to the presence of Planck length and
Planck time.

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irascible
It's the refresh rate of "their" displays.

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inlineint
Actually the speed of light is just a constant that interconnects spatial and
time coordinates.

In special relativity everything moves with c light speed in a 4-dimentional
pseudo-Euclidian space. It means that the light speed constant c is just a
measure unit that interconnects time and spatial coordinates. And the actual
spatial velocity of a particle is just a projection on the spatial coordinates
of it's 4-dimentional velocity which always has length equal to c.

So the existence of light speed constant seems more like a boundary condition
that limits class of possible solutions rather than something connected with
the processor's clock-speed.

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csorrell
It is my understanding that when determining the official figure,the General
Conference on Weights and Measurements took an average of some of the most
accurate measurements that were available at the time. But I think that there
were variations in each case. So we could assume that either our tools were
just not precise enough, or that the speed of light is not actually constant.
(or both?) I'm curious, are physicists these days routinely measuring the
speed of light, and if so are these measurements consistent?

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hacknat
It is the fixed rate at which all mass-energy is moving through space-time.
The rate never changes for anything. If an object is moving slowly through the
space axis of space-time then it is moving quite rapidly, though at a fixed
and predictable rate, through the time axis, and vice versa. C is the rate at
which time and space are flowing in the simulation. Clock speed is a good
analogy.

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thomas-b
Could just be a bug between time and space being linked while it should not.

Or we need to buy the FTL DLC

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staunch
What video game doesn't have constants?

    
    
      const LIGHTSPEED = 299_792_458

~~~
pjungwir
How many significant figures does it need to have, do you think?

And that makes me wonder, how does this simulation deal with irrational
numbers and real numbers? How does it represent pi and radical 2? The Greeks
were afraid of these numbers. Are they are problem for a theory that we are a
simulation run on finite resources?

~~~
sjg007
I think it has to do with the concept of computable vs non computable
functions. One stand is that if the Universe is a simulation then by
definition it is computable but we can clearly define and reason about non
computable things (which suggests that it is not in fact just a Turing machine
and may in fact the hyper computer running the simulator. But you can't really
get above that. So the speed of light is just a defined constant which no
meaning and we can't pierce the through hypervisor.

[https://en.wikipedia.org/wiki/Simulated_reality#Computationa...](https://en.wikipedia.org/wiki/Simulated_reality#Computationalism)

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Joof
Without knowing physics, maybe we should find a good simulator, change the
speed of light constant and see how the interactions change.

Alternatively, see if different equations scale differently based on the speed
of light.

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thiago_fm
c is the speed of light because then you can create a constraint over the size
of the universe, also make everything that is placed inside of this universe
that has mass locked inside it, as it would take infinite energy to get
something with mass(which also would go to infinite) to be at the same speed
of light.

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imakesnowflakes
Because that value made life, as we know it, possible.

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eecks
Hardware limitation?

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PythonDeveloper
In order for any simulation to proceed at a steady state, there must be _at
least_ one constant. Everything else can be variable, but in order for time to
progress at the same "tick", it has to have something to measure by.

That said, why create a "tick" when the perception of that tick can vary by
individual? When I go into code mode, 10 hours can slip by in an instant, and
I'm not hungry or thirsty until I come out of it.

Perhaps it's just an affectation of focus, as time still "ticked" by at it's
normal rate.

Einstein said that the effects of time move more slowly the closer you get to
C, so it makes sense that C would be the univeral "tick" if this was a
simulation. As evidenced by Mars rovers _and_ Voyager, an earth clock on
another planet or in space still ticks at the same rate (Voyager and Mars are
moving through space at the same rate we are moving around the sun, about
61,000km/hour).

There's no other reason for light to move at a steady speed, and nothing
apparent that's stopping it from going faster.

~~~
kleer001
This "tick" theory gets my vote.

I see c as an emergent quality of a base granularity. If the universe is a
cellular automata then c would be related to the distance between two
successive layers, between what just happened and what is happening now,
between now and next.

