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Show HN: What if the speed of light was 5 km/h?

rivendell.dmitrybrant.com

181–190 of 204 posts

Re: Show HN: What if the speed of light was 5 km/h?

#181
I know this takes the fun out of it, and it is a fun project, but FWIW the speed of light is not an independent variable. It's woven into the fine-structure constant, the relationship between mass and energy, and how any kind of information is transmitted between objects in the universe.

This is more of a simulation of what if light was perceived as 5mph for you and kept the same for everyone else.

It is cool though.

Re: Show HN: What if the speed of light was 5 km/h?

#182

Here is my prediction. If the speed of light were 5 km/s, it would be slower than the speed of sound; consequently, the sound would reach me much faster than the visual image. For instance, if I were surrounded by ten people and one of them clapped, I would hear the sound first and only realize who had clapped quite a while later.

Actually, all the [physics stuff] that allows sound to propagate would also be slowed down, to More realistically - the atmosphere would not be gaseous (everybody dies), the sun would be a black hole larger than the earth's orbit (everybody dies), and quite a few other problems.

Re: Show HN: What if the speed of light was 5 km/h?

#183

One oddity of Lorentz invariance is that two non-parallel boosts decompose into a boost and spatial rotation. I've never quite wrapped my head around this and was hoping to get some insight from this simulation. But afaict, I'm not seeing this effect (press W for a bit, the A for a bit and it's not obvious I'm at a different orientation - if I look down at the ground the gridlines are still axial). I don't know if I'…

go past the cubes at near lightspeed, you'll see them rotated; you can see their back planes even before you passed them.

That’s just the aberration, no? I.e., you can simply smash A and observe some rotation. Since there are no non-collinear accelerations in this case, it’s certainly not the required effect (which is called Wigner rotation).

In the sources I see that the acceleration is applied simply by utilizing a velocity‐addition formula (see https://github.com/dbrant/relativity/blob/fcc20fb18381959ac2...), so no Wigner rotation appears. I guess all the fancy stuff related to how time passes in an accelerating frame (like https://en.wikipedia.org/wiki/Twin_paradox#Difference_in_ela...) is also wrong in this simulation because of that.

You can however observe a mathematically equivalent effect in hyperbolic games, e.g., in Hyperbolica. Hyperbolica even has a quest about rotating a chest by moving it along the axes. On the hyperbolic plane it’s of course not about acceleration but about a winding number you’re doing around some point, but it’s still fun.

Re: Show HN: What if the speed of light was 5 km/h?

#184

Here is my prediction. If the speed of light were 5 km/s, it would be slower than the speed of sound; consequently, the sound would reach me much faster than the visual image. For instance, if I were surrounded by ten people and one of them clapped, I would hear the sound first and only realize who had clapped quite a while later.

Actually, all the [physics stuff] that allows sound to propagate would also be slowed down, to More realistically - the atmosphere would not be gaseous (everybody dies), the sun would be a black hole larger than the earth's orbit (everybody dies), and quite a few other problems.

Didn't even think of this, but yes: 5km/h ~ 1m/s, which is 1/10^8 the real c. This multiplies the sun's Schwarzschild radius (normally ca. 3km according to Wikipedia) by 10^16, making it 310^13 km, with 1AU = 15010^6 km.

It's yet another xkcd-level apocalypse.

Re: Show HN: What if the speed of light was 5 km/h?

#185

Some time ago I had the following shower thought: "the Speed of Light is pretty slow" How i got there: The closest major galaxy to the Milky Way is Andromeda, and is 2.5 million! light-years away. And this is the CLOSEST galaxy, the universe is extremely big. Of course that as you get closer to C, the traveling object will experience time dilation (relative to observer), so the time passed will be less. At 99.999% C,…

> the Speed of Light is pretty slow

Professor Farnsworth: That's why scientists increased the speed of light in 2208.

Re: Show HN: What if the speed of light was 5 km/h?

#187
post #83
post #75

The book Redshift Rendezvous from 1990 explores this idea. (TBH the story is a little clunky, but if you like to see someone look at the physics in depth, it's pretty interesting.) https://www.goodreads.com/en/book/show/1382560.Redshift_Rend...

I'm reading the clockwork rocket at the moment. It's a little different but it's set in a universe where the laws of physics / behaviour of light seems to be different to our own.

If you end up enjoying it, give Dichronauts a shot as well.

Re: Show HN: What if the speed of light was 5 km/h?

#188

I know this takes the fun out of it, and it is a fun project, but FWIW the speed of light is not an independent variable. It's woven into the fine-structure constant, the relationship between mass and energy, and how any kind of information is transmitted between objects in the universe. This is more of a simulation of what if light was perceived as 5mph for you and kept the same for everyone else. It is cool though.

I think the unspoken point of these simulations (Carl Sagan also famously did one for the good Cosmos) is not what if the speed of light was lower, but what would traveling at near the speed of light look like in a more recognizable/'intuitable' scenario than the endless vastness of space with little specks of stars flying by us.

Re: Show HN: What if the speed of light was 5 km/h?

#190

Whenever I think about light speed being fast, I imagine myself standing at the edge of the solar system and watching a hypothetical photon travel from the Sun to the Earth and taking 8 minutes. Suddenly it doesn't feel like light is really all that fast except at human scales. 5 km/h would be fascinating though.

I wish the guy who created this included a 'your perceived velocity relative to [some fixed point]'. The speedometer shows what an at rest observer would perceive your velocity as, not what you would perceive it is. The 'magic' of relativity is that the speed of light is not really a speed limit. You can travel endlessly far ahead of it. Distance and time then begin to distort, and you effectively travel into the future, but you can go arbitrarily faster than it.

If we ever reach the technology to enable relativistic starships (basically able to accelerate at 1g or so for years at a time), then the universe is going to get seriously weird. Not only for us, but also for people in the distant future who will regularly have ancient relics from the past traveling into their time, when they will likely scarcely resemble us, and going 'Hello fellow... humans?' That'd be some next level archaeology opportunities though.

It'll also be socially odd as the elite and powerful travel off into the future seeking immortality, unable to ever return, at least so far as we currently understand.

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