I’ve only just learnt that the speed of light is really the speed of causality and I’m trying to understand it. I’m sorry if this is a stupid question but imagine I had a seesaw a lightyear long. I sit at one end and the other end lifts instantaneously. If someone was sat at the other end I would be lifting them faster than light could reach them. Their being lifted would be faster than the speed of causality. Is this wrong? Does one end of a seesaw dropping and the other end lifting not happen instantaneously with one another?
EDIT: Thank you to the people who have all responded so far. I can see that my thought that the two ends of the sawsee moving simultaneously with one another was the error in my thinking, and that the reason I thought this was due to scale and in reality a seesaw seems instantaneous but it’s not. Thanks again to those who took the time to reply and I’m grateful for your kindness.
In: Physics
> I sit at one end and the other end lifts instantaneously.
Nope, that’s not how it happens.
When you sit on a seesaw, your weight pushes down on the atoms in the seat. Those atoms push down on the atoms at your end of the beam, which push on the atoms next to them, and so on and so forth until the other end of the beam pushes up on the other person.
This seems instantaneous on the playground, and then the speed of light is really fast. But, it’s neither. In a substance with normal stiffness, the wave moves closer to the speed of sound than the speed of light. Still really fast on the playground. The speed of light is the fastest speed that causality can spread, most real systems not using light are much slower.
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