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

The wavelength of light is λ = c / f, where c is the speed of light and f is the frequency.

When c is approximately 10^7 times lower, so is the wavelength (if we keep the frequency the same), so now-visible light would have wavelengths far shorter than an atom or a molecule, and probably couldn't be easily detected by biological means.

You could say: sure, maybe we'll just see light at lower frequency. Maybe that's true, but the energy of a single photon is E = hf, where h is the Planck constant. So if we assume much lower-frequency photons, they have much lower energy, and thus become harder to detect.

Lots of other things could be different, like chemistry, heat conduction etc.

At a height of roughly 1.8, at c = 5km/h, light would take 0.1 seconds to travel from head to toe. Nerve signals are much slower than c, so human bodies likely wouldn't exist as we know them.

The list of potential implications to consider is fascinating, endless and maybe even a bit overwhelming :-)

At first sight, this is remarkably more accurate that the "slower speed of light" game from MIT that was made available all those years ago (~2012).

Many issues with the MIT game were discussed here:

https://physics.stackexchange.com/questions/43695/how-realis...

While the thread lists multiple issues, the issue that I found was with modeling temporal aspects of relativistic doppler (I also reported it on the github repo of the "slower speed of light" project, but that doesn't appear to be maintained):

https://github.com/MITGameLab/OpenRelativity/issues/17

In this game, it looks like the temporal component of the Doppler effect is modelled correctly.

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 traveler would take ~11,000 years to arrive to Andromeda.

So again, even at 99.999% C, 11K years seems like a LONG time to reach even the closest galaxy.

My reasoning was: the speed of light is pretty damn slow.

But then I realized: no, it's not the speed of light that is slow, is my frame of reference.

For us humans, 11,000 years seems like A LONG time, but for the universe is not that long.

The universe's age is estimated to be 13.8 billion years. 11,000 years is 0.0000007971 of the age of the universe.

An average human lives 70 years, 0.0000007971 of that lifespan is approximately ~0.4 hours, or 29 minutes, so it's not that bad.

So yeah, frame of reference matters.

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'm misinterpreting the math, or the simulation, or maybe the simulation is doing something to 'correct' for this behavior so things are more natural, or something else. Does anyone have any insight?

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.

No doubt inspired by George Gamow's Mr.Tompkins in Wonderland (https://en.wikipedia.org/wiki/Mr_Tompkins). That was recommended reading for entering Physics undergrads when I did my degree.

Velocity raptor is a free game that accurately simulates the effects of special relativity. It slows down the speed of light to 3m/s and you solve puzzles as a cute dinosaur. https://www.testtubegames.com/velocityraptor.html

There is also a helpful FAQ which explains all the strange things happening, such as length contraction, time dilation, and color shifting: https://testtubegames.com/srel101.html

My favorite levels are #18 (which demonstrates time dilation), #26 (which demonstrates space warping), and #42 (which demonstrates retarded time https://en.wikipedia.org/wiki/Retarded_time ). All the levels are unlocked and you can skip to any level.

It would be nice to add controls for mobile.

MIT Game Lab made a take on this back in 2012.

https://gamelab.mit.edu/games/a-slower-speed-of-light/

This is an awesome thought provoking question! My mind goes immediately to perhaps using this as a “time scaled” model to “observe” well known physical experiments and physical phenomenon if possible eg Young’s Experiment. Could that work / be useful? I am not a physicist but currious.

Too bad that it does not seem to work on mobile. I did not find any way to move around (add arrow buttons? Are we supposed to move around?) and if I double tap I change the direction in which I am looking but not very predictably. Maybe my phone is too slow.

In the Three Body Problem Trilogy by Liu Cixin some of the more advanced civilisations have the ability to change the speed of light locally with very interesting consequences for the that local space

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...

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.

What if the speed of light were 5 km/h?

Btw there is also this

https://en.wikipedia.org/wiki/A_Slower_Speed_of_Light

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.

"What if the speed of light was 5 km/h?"

Website loads in few ms

Nahh it's not

Interesting experiment! What I missed (as a non-scientist) is a live explanation of what is happening while I'm navigating this virtual world and changing parameters. This would be a great way to learn!

Hmm, by some bug my back arrow first slows me down from approaching c, but then will sudddenly spead me back up (while going backwards), so I get stuck in a dark world. (Firefox on Linux).

Edit, maybe it's because the speed shift is so coarse I cross past 0 km/h from back to forwards and reverse too fast...

Other than this, very very nice. Love this kind of thing for developing intuiting outside the normal range in which we experience the laws of Physics. Well done.

I think the old SciFi classic "Zone of Thought" and the other book which name escapes me now explorer this idea, although not 5Km/h.

To stop a 'blight' in the universe, some natural laws have to be changed wherever it starts to spread, is the story premise if memory serves me.

The speed of light, wave-particle duality, and so on, always make me feel that the universe also has a "computing power"

Feature request: I'd like to ride the ferris wheel.

Very related Scott Manley video that discusses and simulates the same effects https://www.youtube.com/watch?v=R_g9EeT233Q

Which parts of this were ideas you came up with yourself?

Awesome, at 5 km/h it feels like I'm in a black hole. Time stops at the speed up light if I'm not wrong!

FWIW, the best traveling speed is 147000km/h, because the Doppler effect makes a red light appear green. ;)

Light doesn't have a "speed" as in the usual meaning of the word "speed". Talking about speed requires defining spatial distances and time durations, which are in turn defined or created by the phenomenon of light.

Light doesn't "travel". It's just an exchange of entangled photons creating the concept of time duration and distance.

This is awesome. I always think about this. As humans, we are very limited in what we can perceive and experience. A higher form of entity could have a completely different way of viewing nature and the world.

Just a thought experiment for you guys: imagine a bacteria that survives inside humans. It doesn't even know what a human is. For the bacteria, its entire world is simply the environment in which it lives. It doesn't know that we are living beings actively trying to maintain ourselves and survive.

Now, suppose a harmful bacteria enters our body, makes us sick, and we take medicine that kills all of them. From the bacteria's perspective, it could look like a natural disaster or some unexplained event in which they all suddenly get wiped out. They have no idea that a living being called a human actively tried to eliminate them using something called medicine, which was engineered specifically to kill them.

Similarly, what if our world, or nature itself, is part of some higher-level entity that we simply exist within? What if the reason for our deaths, natural calamities, and other events is something completely beyond our perception? Whatever we do, we may never be able to understand what is actually happening at that level, just as bacteria may never be able to understand that humans exist.

One thing that could potentially support this idea is self-regulation. We see self-regulating systems throughout nature, and these patterns seem to repeat at different scales. We ourselves are self-regulating organisms, and nature also has countless cycles and mechanisms that regulate themselves.

Maybe these patterns continue at scales we cannot perceive. We can observe certain things at the scale of humans, but we still don't fully understand what happens at the nano scale or on the scale of the universe. Perhaps there are higher levels of organization and self-regulation that we simply don't have the ability to perceive yet.

The Schwarzschild radius is proportional to c^-2, so this would mean the Schwarzschild radius of the Earth would be about 400 billion km, and the Earth would be a black hole.

Feels like W goes back (instead of forwards like in an FPS), and S goes forward. Is that intended or just my keyboard being weird?

EDIT: ah, by setting 'Speed of light' parameter to 40km/hr I find it a bit more intuitive

This only works on a desktop? Is there any way to interact with it on a phone?

The most obvious thing would be that we and other creatures would have sight as a secondary sense. If light went that slowly we would have to develop other ways of navigating the world, such as echolocation, smell or touch.

Well I'm not a physicist, but we all travel through time at the speed of light. With a much smaller speed of light, I think relativistic speeds would be much easier to achieve. I.e. you could age noticeably differently than your family on a solo car drive to get groceries.

For some reason I get a black screen in Safari. Renders ok in Brave on the same MacBook Pro.

This is what it's like with my new glasses

This looks oddly similar to a psychedelic trip.

So it's without collisions, I take it?

I got confused by the premise. To the fully blind person, the speed of light does not matter. He'll hit the object 5 meters away from him regardless if he sees it or not (as will everyone else, but it'll look weird).

Why are the lamp posts blinking in a weird way?

See also https://gamelab.mit.edu/games/a-slower-speed-of-light/, a 2012 game that did the same thing

What if the speed of light was 2c instead of c? Would that change anything for us?

So weird, after visiting, my mouse icon disappears!

Then we will never be able to see aliens again.

in the real world if the speed of light was 5 km, we'd probably be a lot smaller!

Um, speed of light and gravity are so fundamentally linked that nothing you see would look like that. Just changing speed of light but not adjusting anything else makes little sense.

Now I'm curious what the evolutionary ramifications of this would be.

I don’t quite get the assumptions here. If c were actually 5 km/h, causal influences would propagate much more slowly. With G unchanged, planets and stars at their current masses and sizes would lie within their Schwarzschild radii. Any rock greater that 1.5km in radius is a blackhole. With c reduced to 5 km/h, the black-hole threshold would correspond to a surface escape speed of just 5 km/h. Holding the other relevant constants fixed would also radically alter atomic structure and chemistry. It seems like a lot would change before we could be around to observe the cool redshifts. Is the reduced c being applied only to the visual effects?

cool idea, but being vibe coded doesn't inspire much confidence on whether the math or author subject understanding is correct.

As such I wouldn't base my understanding on the subject on this as-is. Which is a shame as, if it was actually hand coded I might actually use this to learn relativity, something which would otherwise be out of my reach.

A note on source code, I think committing the actual javascript code and such is a mistake at the level of committing compiled binaries to a repo. It's more useful, correct and genuine to upload the prompts used, which are the source code that generates the target code, and upon which the author and others can study and modify the program.

That said, as an idea, it reminds me of Kay's dynabook example ( https://dl.acm.org/doi/10.1145/800193.1971922 ) :

"Here look." Her fingers started to fly on the DynaBook's keyboard, altering the program she had·written several weeks before .. You justact as though the ship is pointed towards the sun and add speed!· As she spoke her ship started to fall, but not towards the sun. Oh no!..·"

If we want to move closer to that ideal, of interactive education, I don't think we can just apply the old forms and use the LLM to aid one in being the allmighty program-creator, the LLM needs to be placed at the service of the user. I can't help but seeing the usage of LLMs to generate code as misplacing this power. It's as if a new powerful metal were discovered and smiths can only think about making hammers and foundries and casts with that metal, considering it too valuable to actually use it for the products being smithed.

Would mean the biomolecular computers would be faster than electronics.

Electronics wouldnt work at all.

Can't see your website but I would think everything you see would have so much latency it would be worse than today's internet with dialup using 2GB of RAM on an Atom CPU ;)

Next step, taking into account effects of acceleration according to general relativity.

this is really great

I think this is not possible. There is most likely a reason as to why light has this speed. Naturally it must be tied to energy and interaction of energy with other things. I also don't think "human speeds" applies here because it assumes that humans were decoupled from this, which I don't think we are at all. Besides, humans also use fairly fast things once you go down to the level of molecular biology and chemistry; the chromophore 11-cis-retinal is quite fast in its changes, for instance, and various enzymatic reactions such as by the carbonic anhydrase - up to 10⁶ reactions per second for the latter (assuming there is a sufficient amount of substrate available). That's not slow.

You wouldn’t be able to see shit OP