Thread: Special Relativity misconceptions

Originally Posted by Xei

Or keep up the highly intredasting intellectual discussion about something you don't actually know the definition of, that would be cool too.

Nobody can type faster than me because my car is a car.

Originally Posted by sloth

Two cars leave point A traveling in the same direction at 2mph. Relative to car 1, car 2 is motionless.
Two cars leave point A traveling in the same direction at C. Relative to car 1, car 2 is... what?

Please explain this in normal dumb guy words. I am not a rocket surgeon, nor am I impressed by them.

There is no way to explain in "normal dumb guy words". It is the special theory of relativity. It's easy and graspable for people willing to work for it. "Please explain this in normal dumb guy words" means "I am not willing to work for it". If you are willing to work, then here it goes.

You are using the principle of relativity in your analysis. This goes back to Galileo. Say that at time t_0, both cars are at x_0. Then at time t, both cars are at x=t*2mph if we measure t in hours.
That is the "restframe" of point A. The position of A is always x=0 when measured in this rest frame.

The principle of relativity essentially says that physics works the same in all reference frames which are the rest frame of a particle moving with constant velocity. We need to be able to translate between frames.

Lets move to the car frame. With the cars moving at 2mph to the right in A's rest frame, we see that in the car frame, the cars are always at x=0. On the other hand, we know from experience that the distance between them will stay the same from one frame to the other. Hence the position of of A in the car frame must be given by x = -t*2mph. So in the car frame A is moving to the left at 2mph.

In general, if (t', x') is the coordinate of an event in A's frame, and (t, x) is the coordinate of an event in the car frame, then t = t' and x = x - t*2mph. These are the galilean transformations.

The problem occurs because the speed of light is predicted to be constant from maxwell's equations and is experimentally confirmed to be constant.

So c is constant.

But if those transformations are correct, then we're in trouble. Flash a light at (0, 0). Describe it in A's frame. A photon at (0, 0) will also intersect the event (1, c), one hour later and one light-hour away. Now lets translate to the car frame. A photon at (0, 0) and (1, c) in A's frame will be present at (0, 0) and (1, c - 2) in the car frame. So the car frame will measure the speed to be c - 2 miles per hour. This contradicts experiment and the predictions of electrodynamics.

The correct solution is to use the lorentz transformations instead of the galilean ones. This has the effect of preserving the principle of relativity but sacrifices some common misconceptions of distance and time. The key to accepting this is to understand that you don't know everything and that nobody ever made a deal with you promising that your experience was valid for all realms of existence.

If you think hard and ask questions instead of making ignorant statements, we can go into the lorentz transformations at some later date and you might actually learn something...

EDIT:

Of course the erroneous assumption was "the distance is the same in all frames of reference". Also, the assumption that t = t' is erroneous as well. There is no "absolute" time.

I really appreciate your explanation there, Phil.
It may take me a little bit of reading to figure it all out in my head.
I still don't understand why two objects moving at the same speed, in the same direction, are not motionless to one another.
I also do not understand why the speed of light is not relative, especially when you consider the fact that it actually slows down and stops when it enters a black hole.

Originally Posted by sloth

I really appreciate your explanation there, Phil.
It may take me a little bit of reading to figure it all out in my head.
I still don't understand why two objects moving at the same speed, in the same direction, are not motionless to one another.
I also do not understand why the speed of light is not relative, especially when you consider the fact that it actually slows down and stops when it enters a black hole.

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

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.

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.

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.

So we could be in a black hole right now.... Awesome.

One thing I don't get is this:

Why do you not age when you travel at the speed of light?
Is time light?
So if all my atoms are moving at c, my body doesn't age because they are moving "with" the flow, sort of thing?
It's just weird.

What specifically is time? Why does time stop when going c?
Does light not age either? How can you determine time, if light itself is moving everywhere in 0 seconds, but time is measured by the speed of light?

Originally Posted by sloth

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

Well, to a massless particle like the photon, the universe would be timeless. But being a matter-borne object yourself, you need not worry about that

Originally Posted by sloth

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.

But the information about what's happening to the light in the vicinity of the black hole must necessarily exit that curved space to get to you. So when it gets to you it's behaving normally. I think your problem is that in your mind there's some "objective" observer, and you're not realizing that all observers are correct...

Originally Posted by tommo

So we could be in a black hole right now.... Awesome.

Actually a while back I read about a serious cosmological hypothesis that the universe itself is the interior of an event horizon, and the big bang is the singularity. Weird stuff.

Originally Posted by tommo

One thing I don't get is this:

Why do you not age when you travel at the speed of light?
Is time light?
So if all my atoms are moving at c, my body doesn't age because they are moving "with" the flow, sort of thing?
It's just weird.

You don't travel at the speed of light, so don't worry about it. Although I can say that as you approach the speed of light relative to a specific observer, your space and time dimensions start to 'mix', so that instead of travelling forward in space at a certain speed and forward in time at 1 second per second, your space speed increases less than normal and your time speed increases to more than 1 second per second.

Originally Posted by tommo

What specifically is time? Why does time stop when going c?
Does light not age either? How can you determine time, if light itself is moving everywhere in 0 seconds, but time is measured by the speed of light?

Not all questions have answers.

Originally Posted by cmind

Well, to a massless particle like the photon, the universe would be timeless. But being a matter-borne object yourself, you need not worry about that

You are assuming that I am a matter-borne object and I take offense, you damned hyooman!

Originally Posted by cmind

But the information about what's happening to the light in the vicinity of the black hole must necessarily exit that curved space to get to you. So when it gets to you it's behaving normally. I think your problem is that in your mind there's some "objective" observer, and you're not realizing that all observers are correct...

But it seems to me that if all observers are correct, that this, by definition, makes it relative. I'm sorry if I sound repetitious and stupid. Perhaps my definition of "relative" is incorrect", or maybe I have unlocked a secret of physics that science has yet to unravel. I shall call it "sloth's law", and it will be way cooler than anything that silly ol' Einstein came up with.

Originally Posted by cmind

Actually a while back I read about a serious cosmological hypothesis that the universe itself is the interior of an event horizon, and the big bang is the singularity. Weird stuff.

I like this.

Originally Posted by cmind

You don't travel at the speed of light, so don't worry about it. Although I can say that as you approach the speed of light relative to a specific observer, your space and time dimensions start to 'mix', so that instead of travelling forward in space at a certain speed and forward in time at 1 second per second, your space speed increases less than normal and your time speed increases to more than 1 second per second.

However, you don't observe this. Only an outsider would observe this, which would make this relative.
...right?

Originally Posted by cmind

Not all questions have answers.

I know! Like, when I try to pull out of a parking lot, and suddenly a convoy of vehicles appears out of nowhere to slow me down! Where do they come from!? What are they doing when they are not impeding my passage onto the road?

Originally Posted by sloth

But it seems to me that if all observers are correct, that this, by definition, makes it relative. I'm sorry if I sound repetitious and stupid. Perhaps my definition of "relative" is incorrect", or maybe I have unlocked a secret of physics that science has yet to unravel. I shall call it "sloth's law", and it will be way cooler than anything that silly ol' Einstein came up with.

Your definition is wrong.

Originally Posted by sloth

However, you don't observe this. Only an outsider would observe this, which would make this relative.
...right?

Correct. Your use of the word "relative" here is very different from above, when you were talking about looking at black holes from far away.

Originally Posted by sloth

I know! Like, when I try to pull out of a parking lot, and suddenly a convoy of vehicles appears out of nowhere to slow me down! Where do they come from!? What are they doing when they are not impeding my passage onto the road?

They wait...they wait.

Originally Posted by cmind

Your definition is wrong.

I think the Science Book could be wrong, honestly.
Sorry if I make some Science followers angry with that line.

I will simply make a new word for the concept that I am talking about:

slothy
Adjective
existing or having its specific nature only by relation to something else; not absolute or independent: Happiness is relative.

I'm not saying that you're wrong in your quote of the Science Book. I'm saying that I think that particular verse of the Science Book could be wrong. If light/space/time/or cupcakes are bending and slowing down or anything like that, they are ALWAYS doing so IN RELATION to me, since I am the center of the universe.

Originally Posted by cmind

Correct. Your use of the word "relative" here is very different from above, when you were talking about looking at black holes from far away.

I don't think so. Even if light is slowing down WITH or BECAUSE OF dilation in space time, it is still slowing down in relation to me.

I'm not trying to be hard headed. I promise. I can see what you're saying, I think. I just don't see the evidence, or frankly, the difference. If light is getting mangled because space/time is getting mangled, or if light is getting mangled all by itself, you still can't say that it is going a particular speed, or that it is in a particular spot in space, unless you reference SOMETHING else.

Originally Posted by sloth

I think the Science Book could be wrong, honestly.
Sorry if I make some Science followers angry with that line.

I will simply make a new word for the concept that I am talking about:

slothy
Adjective
existing or having its specific nature only by relation to something else; not absolute or independent: Happiness is relative.

I'm not saying that you're wrong in your quote of the Science Book. I'm saying that I think that particular verse of the Science Book could be wrong. If light/space/time/or cupcakes are bending and slowing down or anything like that, they are ALWAYS doing so IN RELATION to me, since I am the center of the universe.


I don't think so. Even if light is slowing down WITH or BECAUSE OF dilation in space time, it is still slowing down in relation to me.

I'm not trying to be hard headed. I promise. I can see what you're saying, I think. I just don't see the evidence, or frankly, the difference. If light is getting mangled because space/time is getting mangled, or if light is getting mangled all by itself, you still can't say that it is going a particular speed, or that it is in a particular spot in space, unless you reference SOMETHING else.

The entire theory of relativity is fundamentally based on the assumption that light travels at speed c for all observers. Everything else follows from that. You literally cannot talk about light not going c in the context of relativity, because that's not relativity anymore. Now, you can either live in ignorance or open a fucking book and learn something. Either way, I and probably everyone else are done with you.

You mean open a book and believe whatever it says without question? Just like a religious person would do?
If the entire theory is based off of an assumption then it stands to reason that if that assumption is wrong, the theory could be wrong.
If I am not talking about the theory of relativity, then I am okay with that. I am talking about SOMETHING, and as I said, I shall name it "sloth's Law".
The fact remains that light entering a black hole slows down and stops. I understand that this means that c is constant RELATIVE to the surrounding space/time, however, since time does not stop for me when the light does this, then this decrease in speed is RELATIVE to ME. If Science doesn't consider this to be a form of relativity then maybe it should. I don't personally care, though.

Or maybe we humans know everything there is to know.

If everyone wishes to just call me blasphemous, rather than attempting to explain why I am wrong, I am okay with that too. This happens when I try to talk to sheeple too.

If you want to rewrite the Gospels, then yeah you gotta be an expert on the Bible. Similarly, if you want to rewrite relativity, you gotta understand the theories. Deal with it.

Kay.