This is an idea for a closed-system propulsion device using a theoretical EM-pulse-emitting antenna fixed inside a closed rectangular prism floating in space.
I AM NOT SUGGESTING THAT I THINK THIS WILL WORK.
However, I don't know enough about physics to know why it won't work. I am asking you guys why this won't do what the image shows:
>antenna emits a pulse of energy, system should not move because it causes an equal and opposite force on all sides of the antenna
>pulse hits the left side of the box, exerts force F1 on the left side of the box, and the whole system moves to the left
>later, pulse reaches the right side of the box and exerts force F2 on that side
>F1=F2 so the box stops moving
>box is now in a different place; another pulse can be emitted to continue in this direction
I've been thinking something similar actually so i'll give you a bump for answers. Originally i was under the impression that sending this pulse of microwaves or whatever it has to be (some energy) wouldn't cause a force on the box, but if it does why wouldn't this work, along with the EM?
It would indeed impart a miniscule force. See solar sails.
I can understand why this device shouldn't work given current model of physics. Because the microwave energy is constantly emitted, the force on both sides of the device is constantly the same, if you consider the forces on the inside of the cone part pushing it back in the direction of the small end. My idea is different because the energy comes in one single pulse at a time, which will make the whole system move and then stop as it hits each wall
It's not, because a photon rocked emits the photons in a direction and they are sent away from the system. This thing recaptures the momentum of the photons within itself and the whole thing still moves.
>This thing recaptures the momentum of the photons within itself and the whole thing still moves.
No. Think about it. You are saying that when the photon is emitted, nothing happens. That would mean that photon rockets don't work. What is actually happening is
1. You emit a photon. The box moves in the direction opposite to the direction of the photon.
2. The photon hits the other side of the box, stopping the box
So all you have is a photon rocket that stops itself pointlessly.
right, it stops itself, but now it's in a different place than before. I agree that the idea would be more pointless to make than a photon rocket if it could be made, but that still doesn't address the problem of how this could work without actually emitting anything away from the system
Oh, and it's not just a photon rocket aimed at the inside of a box. it's essentially two photon rockets pointed away from each other, mounted inside a box, and closer to one end than the other end. So when it emits the photons it doesn't move, when the left photon hits the left side it moves in that direction and when the right photon later hits the right side it stops moving, now at rest in a different place than before
The bullet and gun "emit" from each other and both go off into space, away from each other, forever. A gun mounted inside a box that fired into its own inside wall would move backwards when fired, and stop when the bullet hits the wall, and its center of momentum would not have changed it just reordered its inside parts.
Yes. And how do you think that is any different from the situation of the photon rocket in a box? Again, no momentum is being created. The photon and the box have a certain amount of momentum that does not change from the start.
I see what you're trying to say OP, but consider the left side of pic related. The component forces of the light force on the top and bottom of the box would end up cancelling out the force on the left side of the box and it wouldn't move. If you designed the box in such a shape that the component opposing forces always "missed" the wall, it would work.
What you guys fail to understand is that judging by the memedrive the logic you're using doesn't apply to EM waves. Before memedrive I'd have laughed at OP now I say hey why not give it a try
disclaimer: i dont know much about EM
But are you retards forgetting about Newton's 3rd law? If an electromagnetic pulse creates a force one the box, wouldn't there be a force opposite to the pulse?
This seems like trying to use a fan attached to a sailboat to sail.
Also, why not just take off on end of the box?
I just worked it out. Consider calculating the change in the center of mass of the system, using a loss in mass at the point of the emitter due to the photons (where the momentum p=mc, where m is the change in mass). Now, calculate the change in the center of mass due to the change in position of the body caused by the time delay of the photon momentum transfer on the two walls of the body.
If you do this correctly, you'll see that these changes in center of mass are equal in opposite; in other words, the center of mass remains in its original position. All that is happening is that you're shifting the position of the body relative to the center of mass of the entire system, so you'll never be able to get the body to move past the original center of mass.
1. No, I would think so, but don't know where it would be
2. Right but unlike with the sailboat, I don't understand why this won't work
3. that would work but i'm asking this for hypothetical purposes
what many people in these threads don't realize is that EM--electrodynamics, specifically--is the go-to counterexample to Newton's Third law. It's been known for a very long time and is included in most mechanics books worth a damn that Newton's Third law is not really a physical law but holds for many forces/interactions. Simple contact forces analyzed in introductory mechanics will follow Newton's third law; however, for magnetic forces due to fields caused by moving charges, this is no longer true.
I haven't looked into the EM drive or the buzz behind it, but I can guarantee scientists who are analyzing it/testing it are fully aware of this. I think only clickb8 sites would even bring it up.