Thread: Special Relativity misconceptions

Originally Posted by cmind

No one said that two objects with the same velocity are not motionless to each other... I have no idea where you read that.

I read that here, when Philosopher made the claim that the speed of light was not relative.
If the two objects are moving at the speed of light, in the same direction, they are relatively motionless to one another. This makes the speed of light relative.
I still don't get that part.

Originally Posted by cmind

Light doesn't slow down or stop in a black hole, it's still going in a straight line at c, but spacetime itself is heavily warped compared to flat space. In other words, if you were in the black hole, you would see the light as behaving normally.

But I'm not in a black hole, which means that in my RELATIVE point of view, it stops, warps, and slows down. This makes the speed of light relative.
I still don't get that part.

Originally Posted by sloth

I read that here, when Philosopher made the claim that the speed of light was not relative.
If the two objects are moving at the speed of light, in the same direction, they are relatively motionless to one another. This makes the speed of light relative.
I still don't get that part.

Objects can't move at the speed of light. You might as well be asking "what if gravity went up?"

Originally Posted by sloth

But I'm not in a black hole, which means that in my RELATIVE point of view, it stops, warps, and slows down. This makes the speed of light relative.
I still don't get that part.

It doesn't matter what you see. To the light beam, what matters is the spacetime in its immediate vicinity, which is flat according to GR (differentiability of spacetime). When you look at light bending around a black hole, you're watching an event that is causally disconnected from you, and more importantly, you are causally disconnected from it. Meaning your observations can't have any effect on the event itself. If you were close enough to be causally connected, you would see the light moving in a straight line at speed c.

I think you're a good example of why kids shouldn't be taught general relativity before they fully understand special relativity. You're extremely confused because you don't have a grasp of the basics and you're diving into black hole physics, which is a huge step up from SR.

Originally Posted by cmind

Objects can't move at the speed of light. You might as well be asking "what if gravity went up?"

No, but light can.
Should I replace the word "object" with "photons"?

Originally Posted by cmind

It doesn't matter what you see. To the light beam, what matters is the spacetime in its immediate vicinity, which is flat according to GR (differentiability of spacetime). When you look at light bending around a black hole, you're watching an event that is causally disconnected from you, and more importantly, you are causally disconnected from it. Meaning your observations can't have any effect on the event itself. If you were close enough to be causally connected, you would see the light moving in a straight line at speed c.
I think you're a good example of why kids shouldn't be taught general relativity before they fully understand special relativity. You're extremely confused because you don't have a grasp of the basics and you're diving into black hole physics, which is a huge step up from SR.

I didn't say that I had to see anything. Even if I am blind, the light RELATIVE TO ME is slowing down, and/or stopping. How is that not relative? Are you saying that I have to be able to manipulate the light in order for it to be relative? I don't think that's right.
The fact remains that relative to my position and momentum, the light is getting mangled in a black hole.