Why would'nt this work?
-
Because the stick isn't infinitely rigid. If you push it at one end the other end doesn't immediately start moving. The time it takes, I think, is equal to the speed of sound inside that material. Ultimately the forces that bind atoms together and allow them to interact are limited by the speed of light.
-
that makes sense, i forgot that pushing something is basically like creating a sound wave on it ^^'
thank you
-
Damn, so that means no FTL communication for now...
-
Your math is off. The Moon is about 384,400 KILOmeters from the Earth, not meters. So 116,485 seconds, or a bit over 32 hours.
-
-
You're gonna want a powerful laser probably and ain't no stick that big like not even fkn close not even we tried so that's why would'nt tbqh
-
So I found a dowel rod online that's 1 meter long by 25 mm in diameter made of beech, which is pretty typical for this kind of rod. Each rod weighs 420 g. 300,000 km is 300,000,000 m. So for a dowel rod to be 300,000,000 m long, it would weigh 126,000,000,000 g, or 126,000,000 kg. You would never be able to push this rod. If you had a magical hydraulic ram that could, it would just compress the soil under it. This is on the scale of the foce released from an atomic bomb.
But let's throw that out and pretend the whole thing weighs 420 grams instead. Maybe it's made of a novel, space-age material instead of beech. And since you've said it can't bend or break, the portion at the surface of the earth would be spinning at roughly 1,000 kph (due to the rotation of the earth), and the portion at the end of the rod would be spinning at about 28 km/s. Most of the mass of the rod would be spinning faster than escape velocity, so you wouldn't be able to hold onto it. It would be gone almost instantly.
Let's pretend you could hold onto it. Then the person on the moon couldn't hold it, because the earth rotates on its axis about 28 times faster than the moon travels around its orbit. So you can see how this problem devolves into ever more layers of magic and hand-waiving.
The final problem is the fundamental difference between classroom physics and material engineering. If you could fix the moon to the end of the rod, and you used a space-age material that weighs 420 g for the whole thing, and it could be so rigid as to not bend, then it would have to break instead. If, instead, it's designed to not break, then it must be able to bend. This is just how real materials work. But even if it does neither, or at most only bends a little, it is still true that as you push on the rod it would compress. So the tip wouldn't move at first. The pressure would move through the rod like a wave. You can't send information faster than light.
-
Do you think it would be possible if you remove the astronauts eyelids? Would that enable faster than light communication?
-
I ran this by an engineer and they said the same thing
-
Excellent write up. -
There's a bunch of these thought experiments that try to posit scenarios where C is violated.
Here's one I remember from uni involving scissors. Similar to what OP was thinking, but really really big scissors.
-
-
-
Hear me out... What about a metal stick?
-
I assume the post is saying that they’re both touching the ends of the stick and then one person pushes. It would be instant. What would sound have to do with an object moving? Purely mechanical communication.
-
Are you saying that the person on the moon would feel a tap from the other end or the person would actually push the stick forward towards the man’s hand on the moon?
-
I'm not a scientist, but when I asked the same question before they said, "compression."
Like, the stick would absorb the power of your push, and it would shrink (across its length) before the other end moved. When the other end does finally move, it's actually the compression reaching it.
-
Metal is a lot heavier than wood. You'd never be able to lift it to the moon.
-
-
