Is the speed of light different in KSP?

[Yeomans]

Hey guys, this is a question that I came across recently in my day-dreaming sessions... I thought, since the scale of the Kerbin star system is much smaller than ours, yet the planets and stars exert comparable gravitational influence (something that is usually explained as an effect of the celestial bodies being much more dense) it led me to realize that the physical laws in this universe must be somewhat different from ours to compensate for these differences. From that point, I began wondering if the cosmic speed limit - the speed of light - would be different as well. Most importantly, given the knowledge we do know about the Kerbin system, is it possible for us to either calculate or take an educated guess as to the exact value? Not only is this a subject of scientific inquiry, however for practical reasons as someone interested in experimentation within KSP, understanding the presumed physical laws and constants of the universe in this game are important. If anybody has any ideas regarding finding this magic number, I'd be willing to entertain them and try my hand at finding it.

Thanks alot!

~Dan

[AceMgy]

Yes it is quite different. The speed of light is infinite in KSP.

The game uses purely Newtonian mechanics, as none of the calculations done by the game contain a gamma correction. I'm assuming, there, as I've not decompiled the game and gone diving into the source code to find out (which would be a pain), but I'd be very surprised if they went to the trouble of including special relativity for no conceivable benefit.

Edit: Just realized you weren't asking if the game calculated relativistic mechanics, but if one could derive a revised speed of light from the constants in KSP. The gravitational constant in KSP is the same as ours, and we have no data about the electromagnetic constants (permittivity and permeability of free space, for starters) that would allow us to caculate the speed of light directly if relativity were to be implemented into the game. So it would be completely up to the devs if they decided to put that in.

Edited June 22, 2013 by AceMgy

[stupid_chris]

Technically, the physics are the same in KSP, there's just no relativity. You can go as fast as you can, no time contractions at high speeds, no speed of light limit, etc. But else it's the same.

It'S true the system is scaled down, but to compensate this to still have normal gravitational forces, they just made the planets out of... super dense materials. For example, Kerbin is ten times denser than Earth and three times denser than lead if I remember correctly. That's illogic, but that was the only way without changing the laws of physics, else some more stuff would be implied and it's a bit out of hand lol.

[MoonHeadJohn]

Are you talking about a universal speed limit simulated within the application or is this more of a blue sky thinking what if the Kerbal universe were real type question?

I can think of a few things for the former but won't waste your time if you mean the latter.

[AustralianFries]

Not sure, but I think the speed of light is the same as is in real life. However nothing happens when you get to/approach it...

[MoonHeadJohn]

Not sure, but I think the speed of light is the same as is in real life. However nothing happens when you get to/approach it...

Doesn't the Kraken rear its ugly head before you even reach 1/4 the speed of light?

Skip to the last 2-3 minutes of the video to see the effects on the space ship.

But yeah, as he says he's gone past 10% the speed of light and the ship is oscillating like mad. If he left it on for 22 days I'm fairly certain the ship would destroy itself before day 5.

[1096bimu]

wtf is with Scott Manley? He often talk about stuff he doesn't fully understand but pretends that he does. popularity has nothing to do with expertise or authority on matters of science.

[allmappedout]

wtf is with Scott Manley? He often talk about stuff he doesn't fully understand but pretends that he does. popularity has nothing to do with expertise or authority on matters of science.

Anyone who claims to fully understand everything is a liar. You're right, he's not perfect, but geez, give the guy a break. He does know his stuff for the most part, as he is an astrophysicisisisisisist, and more importantly, most of the time he's entertaining.

[1096bimu]

Anyone who claims to fully understand everything is a liar. You're right, he's not perfect, but geez, give the guy a break. He does know his stuff for the most part, as he is an astrophysicisisisisisist, and more importantly, most of the time he's entertaining.

I don't see how he's an astrophysicist in any way, I can spot numerous problems in his videos and I don't claim to be even close to an astrophysicist. He's just above layman level.

[Ekku Zakku]

It was oscillating due to physical time acceleration, not so much because of the Kraken. The deep space Kraken is pretty much fixed, there are no floating point errors left to destroy craft at ridiculous speeds or distances anymore; the only "Kraken" left is the one that randomly makes parts fall apart, and that can happen well within the Kerbol system.

The maximum possible speed in KSP is limited to the number of digits the game's variable can handle for speed, and if the speed surpasses the capacity of that variable, there will either be an overflow error or the value for speed will jump to the opposite extreme value it can handle (your speed will either drop to 0 or go to the extreme negative speed possible, idk whether KSP uses a signed or unsigned variable for speed lol)

[Brenok]

I don't see how he's an astrophysicist in any way, I can spot numerous problems in his videos and I don't claim to be even close to an astrophysicist. He's just above layman level.

Could you be more specific? I saw some of Manley's videos but weren't particularly observant.

[MoonHeadJohn]

I don't see how he's an astrophysicist in any way, I can spot numerous problems in his videos and I don't claim to be even close to an astrophysicist. He's just above layman level.

If there is a problem, please do correct whatever he got wrong in that video.

Wouldn't advise derailing this thread questioning his degree in Astronomy and Physics and Masters in IT. Can understand the half of what you see and less of what you hear vibe but this isn't the place for it.

[1096bimu]

If there is a problem, please do correct whatever he got wrong in that video.

Wouldn't advise derailing this thread questioning his degree in Astronomy and Physics and Masters in IT. Can understand the half of what you see and less of what you hear vibe but this isn't the place for it.

do you think he's gonna read every single comment? Besides, I don't really like him because of how he talks to his wife in that video a few days before.

If anybody's interested I could watch his videos again and make a list of mistakes.

[MoonHeadJohn]

do you think he's gonna read every single comment? Besides, I don't really like him because of how he talks to his wife in that video a few days before.

If anybody's interested I could watch his videos again and make a list of mistakes.

Could send him a comment if you feel like it, he seems to catch some of the more interesting posts on his videos.

But anyway, I meant share the proper information in this thread.

[Yeomans]

Well, I am in no position to critique or defend Scott Manley's legitimacy in this regard, however I personally see no flaws.

Anyways, in an attempt to halt the digression, I was kind of asking the question "if the KSP universe were real...". I would think that for an earth-like planet (with life) to be as dense as Kerbin while retaining all of the qualities of Earth it would require some tinkering of physical laws. I'm no scientist but if we were to assume Kerbin, in this universe, is the equivalent of Earth in our Universe, then there would likely be some differences. In that case, could a different speed of light be calculated?

[MoonHeadJohn]

Anyways, in an attempt to halt the digression, I was kind of asking the question "if the KSP universe were real...". I would think that for an earth-like planet (with life) to be as dense as Kerbin while retaining all of the qualities of Earth it would require some tinkering of physical laws. I'm no scientist but if we were to assume Kerbin, in this universe, is the equivalent of Earth in our Universe, then there would likely be some differences. In that case, could a different speed of light be calculated?

Just did a quick Google search and found this which suggests the idea of fossil worlds.

Grasset and his collaborators now say that the strange bodies could be the “fossil cores†of planets that were once much larger, an idea that was first proposed by researchers in 20111.

If it holds true it could mean that such dense worlds would be possible in our universe. But in the same article it also says that super Earths would be left behind by such a process. So not sure if something the size of Kerbin would be left behind.

[Fel]

Problem is that the speed of light is a parameter of em waves, KSP only models Newtonian Physics.

I guess that assuming that electrons have 10.6x more mass could give you a new speed of light, (hv = mc^2) but that is really getting into quantum physics which I really don't have a strong suit in.

Best case, you'll probably observe that light is a special form of raycasting. Hence, the speed of light is equivalent to how fast you can run the game ;p

Edited June 22, 2013 by Fel

[Ralathon]

There are pretty much 2 ways to tweak physics so you can create the kerbol system. Either increase the mass of particles, or increase the EM interaction (or a mix of these 2 obviously) so electron shells are smaller. The speed of light is determined by the magnetic permeability and electric permitivity of empty space. To make atoms 10 times denser the permitivity needs to be 10 times bigger. c^2=1/e0u0 so our new c^2 would be ten times as small, and thus the new speed of light would be about 0.32 times our speed of light.

This change in e0 would however completely destabilize most nuclei so treat this more as an absolute minimum. You need to mess about with the other constants to keep the whole thing stable (increase the strong nuclear force so the nuclei remain stable f.ex)

[Kanga]

There are pretty much 2 ways to tweak physics so you can create the kerbol system. Either increase the mass of particles, or increase the EM interaction (or a mix of these 2 obviously) so electron shells are smaller. The speed of light is determined by the magnetic permeability and electric permitivity of empty space. To make atoms 10 times denser the permitivity needs to be 10 times bigger. c^2=1/e0u0 so our new c^2 would be ten times as small, and thus the new speed of light would be about 0.32 times our speed of light.

This change in e0 would however completely destabilize most nuclei so treat this more as an absolute minimum. You need to mess about with the other constants to keep the whole thing stable (increase the strong nuclear force so the nuclei remain stable f.ex)

I can't imagine any of that being a boardroom discussion, regardless of how accurate it is. (I'm no scientist, just a teenager enjoying a game)

"Okay guys, we've got an issue. We need to either increase the mass of particles or make electron shells smaller... Our users will be outraged otherwise." Can you imagine that? I can't. I don't know whether SQUAD is a science genius or not, but that would be a bizarre discussion indeed. I guess my conclusion would be that some people are taking the theoretical physics that differ between our universe and the Kerbol universe way too seriously and should probably think that Squad can make his own damn physics in the game, and make them as accurate as he likes.

[Boffinbox]

i set my speed of light in remotetech to 3x10^7, and that tends to behave more realistically, especially when controlling a rover from the moon. otherwise, you can control probes on the moon with a 0.03 second delay...

[Crush]

The maximum possible speed in KSP is limited to the number of digits the game's variable can handle for speed, and if the speed surpasses the capacity of that variable, there will either be an overflow error or the value for speed will jump to the opposite extreme value it can handle (your speed will either drop to 0 or go to the extreme negative speed possible, idk whether KSP uses a signed or unsigned variable for speed lol)

I am pretty sure KSP uses floating point values for positions and speeds. Floating point values don't roll over when they overflow*. Integers behave like you described*. Floating point values take the special value of +INV or -INV* when they go beyond what can be represented by the bits they have.

* in almost all programming languages. There are exceptions, but these are rare, because the behavior above is the natural behavior of most CPU architectures.

Edited June 22, 2013 by Crush

[1096bimu]

well you can't go faster than about a google meters per second in floating point.

[Ekku Zakku]

I am pretty sure KSP uses floating point values for positions and speeds. Floating point values don't roll over when they overflow*. Integers behave like you described*. Floating point values take the special value of +INV or -INV* when they go beyond what can be represented by the bits they have.

* in almost all programming languages. There are exceptions, but these are rare, because the behavior above is the natural behavior of most CPU architectures.

Ah I see XD I've still got a lot to learn in the programming field lol, but thanks for clarifying =3 learn something new every day~

[bracknellexile]

Ralathon, am I right in thinking that if you follow this process through then changing the strong nuclear force would likewise have knock-on effects elsewhere and you end up having to try to rebalance pretty much every fundamental constant? I'm struggling to find a reference (my google-fu is failing me) but I'm sure I recall from my undergrad days reading somewhere that it's nigh on impossible for a universe to physically exist unless all the constants have the values they do in our universe. I don't know of any other sets of constants that have been proved to lead to a stable (or even temporarily plausible) universe.