so this image gave me time to think about teleportation machines.
I do think that travelling arbitrarily close to the speed of light (i.e. practically instant) might be doable, and probably actually is, but it would be so expensive that nobody would use it anyways.
i mean, you can just build a rocket and accelerate it arbitrarily close to the speed of light, using enough fuel. but the cost of doing so is prohibitively expensive, so there’s no practical way to actually ever do that in practice.
slow travel is just much more economical, that’s why teleportation is out of the question. but that’s economical reasons, not a fundamentally physical one.
this comic argues that through teleportation machines, travel would become instant and cheap. and i think it’s the opposite: the faster, the more expensive.
teleportation machines probably work by accelerating every part of you to the speed of light and slowing them down again on the other side. so it really is like a rocket acceleration.
and no, they wouldn’t kill you any more than stepping on an airplane does.
there’s also this existential comics about it that argues:
but that’s already the case on an airplane. if you drink a cup of water on the airplane, the atoms inside your body get swapped out for new ones; that literally happens all the time. so it partially kills you? but nobody thinks that way. (ship of theseus)
This isn’t really true.
Let’s ignore things like engine weight and fuel weight for a moment, and say that we’ve got an engine-less, fuel-less (maybe electric?) rocket going through a vacuum. It is able to accelerate and decelerate without consuming any resources. As such, the total mass of the rocket will always be the same, right?
Not exactly. We’ve discovered that as things approach the speed of light, their mass actually increases, meaning that more energy is required to continue accelerating the same object at the same rate. So in our magic rocket example, say the magic motor is able to accelerate the 1000kg rocket 1m/s/s. As the rocket gains speed, that same rocket will have more than 1000kg of mass, and the motor will not be able to accelerate it the full 1m/s/s. Eventually, the rocket will become so massive that the motor is unable to accelerate it a meaningful amount at all.
Now… This is in a hypothetical situation with a magic, fuel-less motor. In the real world, more engine power means a heavier motor which means you need more power which means you need more fuel which means you’re heavier which means you need a bigger motor which means…
If it were just a matter of, “it’s really expensive to do it”, Musk would’ve already teleported a car by now.
It’s worth noting that combining the relativistic correction factor into mass is actually quite problematic. It’s a vector (directional), while mass is scalar(directionless). You suddenly need to ask what direction your mass is. Furthermore, a hypothetical person on the ship will still measure their inertial mass as normal.
As it stands, it would take an infinite amount of energy to reach the speed to light, but you can get arbitrarily close to it, with a finite amount (huge, but finite).
nah, like, i mean, exponentially more expensive. rocket equation
as you go faster, you need exponentially more fuel (with chemical rockets). so it gets really expensive really fast.
you could improve the speed somewhat by switching to electric / nuclear propulsion or by using a solar sail. While electric / nuclear propulsion just increases the effective exhaust velocity, which gives you greater Δv achievable, solar sails fundamentally change the game because they don’t require exhaust to accelerate the spaceship. Instead, any star’s light pushes the ship forward through the pressure that radiation exerts on a surface (thus the name solar sail). Yet while it allows arbitrary maximum speeds, acceleration itself is a very slow process this way, so it might take thousands of years to reach peak speed, which only pays off if you do interstellar travel.
I think the chart you posted helps prove my point. Mass go up, energy needed exponentially go up. That doesn’t just mean “more fuel”, it means more power behind the thrusters. And that chart isn’t even taking into consideration the gain of mass as you increase in velocity, just the mass of the vessel itself.
As you approach the speed of light, the amount of light that reaches these sails decreases, making them less effective, while mass is still increasing.