Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

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

rivendell.dmitrybrant.com

Post reply on HN
Print view View original

201–210 of 219 posts

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

#201

Post by Sopel »

teamonkey wrote: post #178

This is very cool, but what mechanism lets me see the roof of the cars on the big wheel? The cars seem to twist towards me as they approach and away from me as they recede, but from my initial stationary position, which is below the roof of the lowest car, I feel that I shouldn’t ever be able to see light from the top surface of a car’s roof? If I toggle ‘L’ off then indeed, I can’t see the top of any of those cars.…

The cart is moving down faster than the light "bouncing" from the top of the cart towards your eyes. Whether the light can actually bounce this way I do not know. https://imgur.com/a/Aztdj4C

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

#202

Post by evanb »

timoth3y wrote: post #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.

You can adjust the speed of light and hold the fine structure constant (and all other dimensionless parameters) fixed by adjusting some of the other dimensionful parameters.

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

#203

Post by zamadatix »

gwbas1c wrote: post #189

I don't understand movement: "W" makes me appear to move backwards, "S" makes me appear to move forwards. When I use space to stop, I move back to where I started. Is this a bug or am I just really confused?

When you speed up at speeds comparable to that of light, the angles, amounts, and wavelengths of light which reach you will change. This means you can't visually judge brightness, color, distance, and length the same as you normally would.

E.g. when you accelerate ("W") the angle the light rays from in front of you appear to be coming changes, making them look farther away. If you let go of "W" you should keep your current velocity and see you are indeed still moving forward, just in a world more pronouncedly warped by the effects of relativity.

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

#204

Post by bell-cot »

moring wrote: post #184
bell-cot wrote: post #182

Earlier quoted context omitted.

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 3 10^13 km, with 1AU = 150 10^6 km. It's yet another xkcd-level apocalypse.

Sadly, Google's AI search can find no hint of St. Randall working on a What If? 3 book.

(But What If he's sworn it to secrecy?;)

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

#205

Post by throwawaysoxjje »

bell-cot wrote: post #182
ama4efaria wrote: post #176

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.

You don’t have to go that far: Earth itself would be a black hole

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

#206

Post by d34dman »

sakjur wrote: post #91
tliltocatl wrote: post #85

Fun fact: given that the meter is defined in terms of speed of light (and cesium frequency), "changing the speed of light" is a counterfactual impossibility, what is actually changing are some other fundamental constants.

If we realized tomorrow we had the speed of light slightly wrong, we wouldn't change the length of a meter, we would change the definition of the meter. We've redefined the meter thrice already.

Isn't it more like "meter" expands/contracts based on where you are in space?

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

#208

Post by aequitas »

yreg wrote: post #89
zrail wrote: post #15

The first few Discworld books explore this a little bit too. I think pterry dropped the concept after that, I don't really remember it later in the series.

Darkness travels even faster than light on Discworld, because it has to be fast enough to get out of the way when light arrives.

The sunrise flows like a golden river onto the landscape. If I remember correctly.

Also one of my favorites is discworld scientist experimenten with ftl communication through succession by “modulating” a king above a pit of sharks an measuring his son at the other end of the world for “kingness”

Post reply on HN