Forum adverts like this one are shown to any user who is not logged in. Join us by filling out a tiny 3 field form and you will get your own, free, dakka user account which gives a good range of benefits to you: No adverts like this in the forums anymore. Times and dates in your local timezone. Full tracking of what you have read so you can skip to your first unread post, easily see what has changed since you last logged in, and easily see what is new at a glance. Email notifications for threads you want to watch closely. Being a part of the oldest wargaming community on the net. If you are already a member then feel free to login now.

So, I sent this question in to Randall Monroe, because frankly I think the potential implications are so important that it's worth an actual scientist's opinion.

After having read XKCD's What If "Diamond" I had a thought. What if you just simply kept adding 9s to that number and never stopped? Could you eventually reach a level of destruction capable of destroying the entire universe? Considering that actually traveling at lightspeed means going FASTER than whatever point you arrive at the destruction of the universe, is the reality not that going at light speed is theoretically impossible due to the infinite energy requirements, but instead that we should never, EVER do it, because humanity's very first experiment that propels anything actually TO the speed of light would result in the universe's destruction the first time whatever we propel to that speed impacts so much as a single proton?

If I'm right, the reality seems to be much, MUCH more horrifying than scientists are treating it, though I am willing to accept that they simply never freak out about it because they consider the idea of propelling something fast enough to destroy the universe to require so much energy that by the time we can do it, we'd have to have other universes we could live in, at which point those kinds of velocities would simply be pointlessly slow.

Okay, I calmed down about it. I'm good now.

No. https://en.wikipedia.org/wiki/Measurements_of_neutrino_speed for a particle traveling at nearly the speed of light but releasing very little energy with a collision. Also, the farthest parts of the universe are expanding away from us at faster than the speed of light, so the energy released by the collision (which can travel no faster than the speed of light) will never arrive. Finally, the inverse square law very quickly reduces the energy released from a hypothetical collision, even if none of it is absorbed by intervening objects, so it would require unimaginably vast amounts of energy to even be detectable across the universe.

But really, it's a pretty stupid thing to worry about in the first place. The speed limit here is not an engineering limit (like breaking the sound barrier was) where the only question is whether or not we're clever enough to build a device to do it, it's an absolute limit. The energy required to reach 0.9999999999 ... 999999999999c is on the level of "convert the entire mass of the observable universe into energy to accelerate an object to that speed" at which point, well, you've destroyed the entire universe already so who cares about the theoretical problem. Then there's also the fact that the level of collision energy required to destroy your accelerated object and end the experiment is considerably less than the level of collision energy required to destroy the entire universe, so it won't survive to reach those speeds even if you had access to near-infinite energy supplies.

TL;DR: The reason scientists are treating this possibility with no concern is that it won't ever happen, period. Scientists don't live in fear of bad scifi movie plots.

 Peregrine wrote:
No. https://en.wikipedia.org/wiki/Measurements_of_neutrino_speed for a particle traveling at nearly the speed of light but releasing very little energy with a collision. Also, the farthest parts of the universe are expanding away from us at faster than the speed of light, so the energy released by the collision (which can travel no faster than the speed of light) will never arrive. Finally, the inverse square law very quickly reduces the energy released from a hypothetical collision, even if none of it is absorbed by intervening objects, so it would require unimaginably vast amounts of energy to even be detectable across the universe.

But really, it's a pretty stupid thing to worry about in the first place. The speed limit here is not an engineering limit (like breaking the sound barrier was) where the only question is whether or not we're clever enough to build a device to do it, it's an absolute limit. The energy required to reach 0.9999999999 ... 999999999999c is on the level of "convert the entire mass of the observable universe into energy to accelerate an object to that speed" at which point, well, you've destroyed the entire universe already so who cares about the theoretical problem. Then there's also the fact that the level of collision energy required to destroy your accelerated object and end the experiment is considerably less than the level of collision energy required to destroy the entire universe, so it won't survive to reach those speeds even if you had access to near-infinite energy supplies.

TL;DR: The reason scientists are treating this possibility with no concern is that it won't ever happen, period. Scientists don't live in fear of bad scifi movie plots.

I've heard of the Oh-My-God Particles and what they do to our atmosphere when they hit it. I've also heard of light, by definition, traveling at the speed of light yet not causing any noticeable effects when they impact my body, certainly not undergoing nuclear fusion. Different particles behave differently, that's why they have different names.

I'm asking what would happen if we got the kind of matter we would build a spaceship out of up to the speed of light, not what would happen if we got neutrinos up to the speed of light. Though frankly we wouldn't actually HAVE to go the speed of light to theoretically cause that much destruction, simply adding enough 9s to the .9c would theoretically be sufficient.

And, uh, you might wanna re-read stuff, because the entire combined energy of the entire multi-verse would be insufficient to propel so much as a simple proton actually to the speed of light, because the amount of energy required is literally infinite, and I'm pretty sure if we ever found a way around the energy requirements the result of that kind of velocity might still be damaging.

 Pouncey wrote:
Though frankly we wouldn't actually HAVE to go the speed of light to theoretically cause that much destruction, simply adding enough 9s to the .9c would theoretically be sufficient.

Yes, but only on a planetary scale. As I pointed out already, the energy demands required to get the hypothetical mass sufficiently close to the speed of light to be a threat are vastly beyond what is practical to obtain. "What would happen if a relativistic spacecraft hit a planet" is an interesting question, and the answer is somewhere on the "civilization ends" area of the damage scale. Anything higher than that in damage just isn't a relevant question.

And, uh, you might wanna re-read stuff, because the entire combined energy of the entire multi-verse would be insufficient to propel so much as a simple proton actually to the speed of light, because the amount of energy required is literally infinite, and I'm pretty sure if we ever found a way around the energy requirements the result of that kind of velocity might still be damaging.

Uh, yes, I know that. That's why I said "to 0.9999999999999999999999999999999c", not "to the speed of light".

Edit: I should probably read what I'm replying to sometimes.

Yeah, I freaked out over nothing.

Besides, if we ever had enough energy to wipe out the universe, we'd need to be getting extra energy from other universes, so we could just, like, evacuate before the blast hits?