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The speed of light is not a speed limit on effective travel, but on observation. Imagine you build an engine that gives enough thrust to roughly produce an extr
by TangoTrotFox 9y ago
The speed of light is not a speed limit on effective travel, but on observation. Imagine you build an engine that gives enough thrust to roughly produce an extra effective 1km/s of velocity each time you operate it. Even though the speed of light is 300km/s, that engine is going to operate exactly the same on the 301st operation as it did on the first operation. And, in fact, in 'real' terms if we create an engine capable of generating 1g of thrust for years at a time - we could travel 700 light years in ~12 years by thrusting for 1g forward 6 years, turning around and then thrusting for 6 years backwards.
But of course the 'catch' is that time dilation (and length contraction) kick in. And so while from the frame of reference of the ship and all its travelers only 12 years will have passed, from the frame of reference of everybody back on Earth - 700 years would have passed. What we would observe is that as the ship approached the speed of light, its apparent mass would approach infinity, reaching a velocity asymptote at the speed of light.
And these values are also not linear. It's possible to travel a practically unlimited distance in the span of a single human lifetime - from the perspective of that human. 100 trillion light years would take about 62 years at 1g from the perspective of those on board our ship. There's also really really fun paradoxes available here. Imagine somebody leaves Earth towards this planet and at some point decades, or perhaps even centuries later, we develop technology that enables substantially faster travel. Our planetary settlers on their 12 year journey could arrive 12 years later to find that not only is the planet indeed colonized, but it's colonized by the descendents of Earthlings that left decades, or even centuries, after they did.
The really exciting thing here is that NASA seems to have gone silent on the EM drive after having it pass every single test they threw at it. In my opinion, this is evidence of classification which is something that would make sense. If the EM drive somehow actually works - and everything we know says it most certainly should not - that would change absolutely everything. The ability to actually start realistically considering these sort of missions would be mundane compared to other possibilities, which I'm not even going to get into as they sound, and should be, absurd. As an aside, this part on the EM drive is 100% speculation - not to be confused with everything stated above, which are direct and heavily tested (even if absurd sounding) consequences of relativity.
- tachyoff 9y ago> The speed of light is not a speed limit on effective travel, but on observation. It is absolutely a limit on effective travel (if we ignore things like wormholes for a second). Conventional motion through space is bounded by c for several reasons, not the least of which being that the closer you get to c, the more energy it takes to make smaller and smaller changes in velocity (the object acts as though it's gaining mass the faster it goes). In fact, it's asymptotic. Accelerating a particle to c would require an infinite amount of energy.
- TangoTrotFox 9y agoThis is a common misunderstanding, and was the point of the example. A stationary observer observing a particle being accelerated towards the speed of light would observe that particles apparent mass begin to approach infinity as its observed velocity approached the speed of light, thus requiring an amount of energy approaching infinity to continue to accelerate it further. However, this has nothing to do with the scenario with you being that particle. You are currently moving at near the speed of light relative to many things at this very moment, yet your mass is certainly not approaching infinity, America notwithstanding! And if you accelerated enough in the opposite direction of your relative partner to exceed the speed of light it's not like you'd suddenly start finding it impossible. No, it's a matter of observation. From the other particle's perspective it would see your mass approaching infinity and your speed would slow, but the distances you covered would remain the same due to length contraction. A similar effect explains why, for instance, particles in CERN's reactors travel distances that should be impossible for them to travel before decaying. E.g. if the speed of light was 10m/s and a particle decays after 3 seconds then it should be impossible to see that particle travel more than 30 meters. Yet we see it travel hundreds of meters. Isn't relativity fun?
- tachyoff 9y agoUnder relativity, you can't simply add speeds like that, unfortunately (I believe this is related to the fact that the speed of light is the same in all reference frames). Here's a link that can explain it better, though: http://curious.astro.cornell.edu/about-us/139-physics/the-theory-of-relativity/special-relativity/1016-why-can-t-relative-velocities-add-up-to-more-than-the-speed-of-light-intermediate http://curious.astro.cornell.edu/about-us/139-physics/the-th... In short, you can't go faster than light in any reference frame, relative to any other observer. Here's another source: https://physics.stackexchange.com/questions/75501/lorentz-and-galilean-transformation https://physics.stackexchange.com/questions/75501/lorentz-an...