If the universal speed limit is 299,792,458m/s. And you had a rod several light-years long, and began spinning while holding the rod, wouldn’t the other end of the rod surpass the limits?
In: Physics
There’s a lot of answers here about how long it takes for the act of you pulling on the rod to travel down the length of it before it fully starts to react, and that’s fine, but if, in this scenario, you were willing to wait, that wouldn’t be the main issue.
The main issue is the acceleration. In Newtonian mechanics even that wouldn’t be an issue and you’d be able to, albeit slowly, accelerate the end of the rod past the speed of light. But we’re not talking about Newtonian mechanics, we’re talking Einstein’s relativity. And with that on mind, even if you could get the force to be applied to the whole thing at once, and you were somehow strong enough to move a light year’s worth of rod, you still wouldn’t be able to get the end moving faster than light because no matter how much torque you put on that rod, no matter how hard you try to spin it, it’s other end will only ever get closer to the speed of light, but will never surpass it. It’s hard to wrap your head around but it’s diminishing returns – if eating one hamburger gave you enough strength to spin the rod a certain amount, get it to a certain speed, if it’s close to the speed of light then you might have to eat two hamburgers to go make the end speed up the same numerical amount. Then 3-4, then more. By the time you’re at 99.99999% the speed of light you could build a machine that would turn the entire universe into energy for the purpose of spinning up that rod and you’d only get maybe one more extra decimal place with a nine in it. It gets harder and harder to do as you get closer and to actually get to the speed of light you would need infinite energy, which is impossible.
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