Does the photon get through?

[ryan]

Imagine two very long pieces of thin opaque ribbon equal in length. Imagine that these ribbons are floating in space. They are stretched out lengthwise such that one end of one ribbon meets the end of the other ribbon, so these ribbons maximize their combined length. So, where one ribbon ends the other begins. These ends overlap very slightly so that no light can get through the space that both ribbons meet. Now imagine an observer watching as the ribbons go by at a relativistic speed. The observer has a device that will blow up if hit by a photon coming from a position in front of the observer where a continuous shadow from the ribbons will hopefully be. So from the frame of the ribbons a man sees that the ribbons overlap; therefore, the man will not see the observer blow up. But because of Lorenz transformations, the observer does blow up.

How can this be?

This is just like the ladder paradox only there is only one photon that needs to get through instead of needing simultaneity like in the ladder paradox.

 

[Loren Pechtel]

I don't think the observer blows up.

The ribbon is neither approaching nor receding at the point where it's casting the shadow, I don't think he sees any shortening at that point.

 

[ryan]

I don't think the observer blows up.

The ribbon is neither approaching nor receding at the point where it's casting the shadow, I don't think he sees any shortening at that point.

Oh yeah, I always miss something when it comes to relativity.

 

[barbos]

Imagine two very long pieces of thin opaque ribbon equal in length. Imagine that these ribbons are floating in space. They are stretched out lengthwise such that one end of one ribbon meets the end of the other ribbon, so these ribbons maximize their combined length. So, where one ribbon ends the other begins. These ends overlap very slightly so that no light can get through the space that both ribbons meet. Now imagine an observer watching as the ribbons go by at a relativistic speed. The observer has a device that will blow up if hit by a photon coming from a position in front of the observer where a continuous shadow from the ribbons will hopefully be. So from the frame of the ribbons a man sees that the ribbons overlap; therefore, the man will not see the observer blow up. But because of Lorenz transformations, the observer does blow up.

How can this be?

This is just like the ladder paradox only there is only one photon that needs to get through instead of needing simultaneity like in the ladder paradox.

It's unnecessary complicated ladder paradox, both observers will observe the same thing, because depending on the RF light will be traveling at different angle. with respect to the plane of the ribbons

 

[Bomb#20]

I don't think the observer blows up.

The ribbon is neither approaching nor receding at the point where it's casting the shadow, I don't think he sees any shortening at that point.

Oh yeah, I always miss something when it comes to relativity.

Yeah, relativity does that to people. The issue isn't whether it's approaching or receding -- lengths get shortened regardless of the direction of movement. The reason the photon doesn't get through is that the ribbons shrink together as well as individually. Say each ribbon is a hundred miles long in its rest frame, two hundred miles long together. They're moving by at relativistic speed, let's say enough to shorten them each to 99 miles. That doesn't mean an observer sees a 99 mile ribbon go by and then a one mile gap and then another 99 mile ribbon. What he sees going by is 198 miles of ribbon. The full 200 mile distance shrinks when both its halves shrink.