Thread: Special Relativity misconceptions

Everything is not relative. The spacetime interval measured between two events is not relative. The speed of light is not relative. Further examples abound. Also, YOUR FACE is not a thought provoking idea.

Just so everyone is clear, in my OP, the bold text is me repeating the misconception, and the unbolded text is my correction to the misconception.

Originally Posted by PhilosopherStoned

Everything is not relative. The spacetime interval measured between two events is not relative. The speed of light is not relative. Further examples abound. Also, YOUR FACE is not a thought provoking idea.

The spacetime interval measured between two events is not relative... in three dimensions. After that, they are. The speed of light IS relative if you are traveling at the speed of light. At the speed of light you are motionless. YOUR FACE abounds.

Originally Posted by sloth

The spacetime interval measured between two events is not relative... in three dimensions. After that, they are. The speed of light IS relative if you are traveling at the speed of light. At the speed of light you are motionless. YOUR FACE abounds.

Nothing can travel faster than the speed of light because mass increases with velocity. A vehicle attempting to travel faster than the speed of light would require an infinite amount of energy to accelerate its increasing mass (as far as we know an infinite amount of energy does not exist).

Nothing can travel faster than the speed of light because the speed of light is c.

Originally Posted by Xei

Nothing can travel faster than the speed of light because the speed of light is c.

Unless you measure speed by counting stationary landmarks. To stationary observers, you'll never get to c, but to the moving observer it may seem like they're going faster than c*, with the understanding that stationary time is also going by faster than usual. This is actually a very simple concept, I guess people who don't understand it just didn't get SR to begin with.

* It's actually length contraction, but if you decide to measure your speed as v = (stationary distance)/(moving time), which is not at all unreasonable for a one-way trip, then c is no barrier for the simple reason that you're not using consistent units anyway.

So you're saying you go faster than c by measuring the times in your frame at which you pass landmarks separated by distances in their frame? ...right, if you want to define speed that way.

Originally Posted by stormcrow

Nothing can travel faster than the speed of light because mass increases with velocity. A vehicle attempting to travel faster than the speed of light would require an infinite amount of energy to accelerate its increasing mass (as far as we know an infinite amount of energy does not exist).

I wasn't talking about traveling faster than the speed of light.
I was stating that the speed of light is relative. If I was moving at the speed of light, another object that was also traveling at the speed of light, in the same direction, would be motionless to me.
I was also stating that PHILOSOPHER'S FACE!

Also,

Originally Posted by PhilosopherStoned

Also, YOUR FACE is not a thought provoking idea.

YOUR FACE was not the thought provoking idea I was referring to. I was just ending my post on a meaningful note.

Objects moving at the speed of light don't have a rest frame. You would measure zero distance and zero time moving at the speed of light. Considering "what stuff looks like" at the speed of light is meaningless.

Unless you and YOUR FACE are smarter than Einstein that is...

EDIT:
Oh yeah. LOL about "spacetime interval is not relative...in three dimensions". The spacetime interval is the 4 dimensional, hyberbolic distance between two events in spacetime. So you would square the time and subtract the distance. People will measure different times and different distances between events but when the consider the square of the distance substracted from the square of the time, they will all agree on the number. If they use the same units of course.

Please define the spacetime interval for dimensions other than four before you claim that it is or is not relative. Thanks so much.

Originally Posted by Xei

So you're saying you go faster than c by measuring the times in your frame at which you pass landmarks separated by distances in their frame? ...right, if you want to define speed that way.

Well, I'm glad someone finally at least understands the concept...

Why not measure speed that way? Suppose you're in a spaceship on a one-way trip to a star 100 light years away. Now, you can do the calculation for yourself if you know the math, but if we assume 1g acceleration in the ship frame with a turn-around at the halfway point and 1g deceleration, the entire trip takes just over 9 years in the ship frame, and just over 101 years in the Earth frame. The speed at the halfway point as measure on Earth is 0.9998c, and what about the speed on the ship? Well you could say that the ship is going at a speed of 0 in the ship frame, but much more useful would be to count the landmarks as they pass by. Using this pseudo-speed, the ship peaks at 52c.

Originally Posted by cmind

Well, I'm glad someone finally at least understands the concept...

Hey now. I understood from the beginning...

Why not measure speed that way?

Because it's confusing and obscures some stuff that's pretty fundamental to understanding relativity?

Suppose you're in a spaceship on a one-way trip to a star 100 light years away. Now, you can do the calculation for yourself if you know the math, but if we assume 1g acceleration in the ship frame with a turn-around at the halfway point and 1g deceleration, the entire trip takes just over 9 years in the ship frame, and just over 101 years in the Earth frame. The speed at the halfway point as measure on Earth is 0.9998c, and what about the speed on the ship? Well you could say that the ship is going at a speed of 0 in the ship frame, but much more useful would be to count the landmarks as they pass by. Using this pseudo-speed, the ship peaks at 52c.

As you've already pointed out, but as I feel the need to reemphasize, you're completely ignoring the fact that the observer on the spaceship measures the distance travelled shrinking. This is how that observer accounts for the fact that they've travelled 100 light years in 9 years.

Originally Posted by PhilosopherStoned

As you've already pointed out, but as I feel the need to reemphasize, you're completely ignoring the fact that the observer on the spaceship measures the distance travelled shrinking. This is how that observer accounts for the fact that they've travelled 100 light years in 9 years.

Yes, and? The point I'm trying to get across is that if you're willing to make it a one-way trip, you can indeed get places faster than 1 year per lightyear.

But that's not right.

The reason that it's not right is because you're sitting half in the classical point of view, where space is distinct from time, and half in the relativistic point of view, where length contraction occurs.

Pick an event to start at. Pick an event to get to. Take the spacetime interval between them. If it's positive, then they're timelike separated and you can get from A to B. If they're not timelike separated, then you can't. It's as simple as that. We're operating in four dimensions.

Saying that two events occur at the same place is meaningless unless they also occur at the same time or unless you sneak in a preferred frame of reference. Likewise, saying that two events occur at the same time is meaningless unless they occur at the same place or you sneak in a preferred frame of reference.

Originally Posted by PhilosopherStoned

But that's not right.

The reason that it's not right is because you're sitting half in the classical point of view, where space is distinct from time, and half in the relativistic point of view, where length contraction occurs.

No, I'm not. Why don't you put aside your ego and read what I'm saying. If you accelerate at 1g for 4.5 years, then decelerate at 1g for 4.5 years, you will be separated from your starting point by 100 lightyears and 101 years in the frame of the starting point. In your own frame, you will have clocked 9 lightyears and 9 years (give or take). I understand that, so get off it.

What I'm saying is, from a practical standpoint, if it's a one-way trip, meaning you don't intend on returning to Earth, why the fuck do you care how much time has passed on Earth? Furthermore, you will in fact be 100 lightyears (and 101 years, which is irrelevant if you're colonizing a new place) from your starting point. And from your subjective perspective, you traveled those 100 lightyears in 9 years, although the odometer would say 9.

I'm not saying any more on this. If you haven't understood what I'm saying by now, then you need a lesson in reading comprehension.

You seem to be confused. I don't not understand anything that you're saying. What I'm saying is that you're putting yourself up as an expert on relativity and then selling confusing crap. Nothing about what you are describing is "faster than light" travel.

You are playing games with length contraction to get your result. That's fine. Just don't ignore that feature.

I wonder, is it you or every other member of this forum that questions you that needs to put their ego aside...

Originally Posted by cmind

Yes, and? The point I'm trying to get across is that if you're willing to make it a one-way trip, you can indeed get places faster than 1 year per lightyear.

Not your light-year.

Originally Posted by PhilosopherStoned

Objects moving at the speed of light don't have a rest frame. You would measure zero distance and zero time moving at the speed of light. Considering "what stuff looks like" at the speed of light is meaningless.

Unless you and YOUR FACE are smarter than Einstein that is...

EDIT:
Oh yeah. LOL about "spacetime interval is not relative...in three dimensions". The spacetime interval is the 4 dimensional, hyberbolic distance between two events in spacetime. So you would square the time and subtract the distance. People will measure different times and different distances between events but when the consider the square of the distance substracted from the square of the time, they will all agree on the number. If they use the same units of course.

Please define the spacetime interval for dimensions other than four before you claim that it is or is not relative. Thanks so much.

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.

Originally Posted by Xei

Nothing can travel faster than the speed of light because the speed of light is c.

Does anyone else see the flaw in this statement?

Originally Posted by sloth

Does anyone else see the flaw in this statement?

Your thought processes are both rudimentary and a century out of date. :/

The speed of light is always c (experimentally confirmed in the late 1800s), obviously there is therefore a flaw in the classical model of space and time, and that was the whole reason special relativity was developed.

Originally Posted by Xei

Your thought processes are both rudimentary and a century out of date. :/

The speed of light is always c (experimentally confirmed in the late 1800s), obviously there is therefore a flaw in the classical model of space and time, and that was the whole reason special relativity was developed.

I fail to see how childishly insulting my "thought processes", or spouting off Science Book verses has worked out the flaw in your original statement.
I can't believe you insulted my "thought processes". ROFL!
I'll bet you would be great at a party.

This is a special relativity thread though... how about you look up the very basics of what special relativity is and then come back for a discussion?

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

Alright, kiddo,
I'm not talking about special relativity. I'm talking about your comment:

Originally Posted by Xei

Nothing can travel faster than the speed of light because the speed of light is c.

You can tell, because *your comment* was the subject of my sentence. See, the "subject" of a sentence is what the sentence is about! Isn't that neat to know!? My statement was about your comment. It was not about special relativity or ponies or unicorns. It was about your comment. That means that your comment is the "SUBJECT" of my sentence.

The statement: "Nothing can travel faster than the speed of light because the speed of light is (the speed of light in a vacuum)." is flawed.
This is because the fact that the speed of light is the speed of light is not sufficient evidence that nothing can move faster than this speed. Even if there is further evidence that nothing can move faster than the speed of light, it does not factor in here, because you did not state such evidence as being the reason that nothing can travel faster than the speed of light. You stated that nothing can travel faster than the speed of light because the speed of light is the speed of light.
I am aware that the speed of light is the speed of light. It's very fast, isn't it?! Like a racecar!
Did you know that racecar spelled backwards is still racecar?
That's because the driver is going SO FAST that he doesn't know whether he's coming or going!
Isn't that neato!?
Racecars are neat, huh?
Yeah...

I think the confusion here is that Xei was referring to the mathematically derived value of c, which in and of itself isn't necessarily the speed of light, although it turns out it is (in vaccum). But as usual, he did it in a very confusing and condescending way.

Originally Posted by sloth

I'm not talking about special relativity. I'm talking about your comment:


You can tell, because *your comment* was the subject of my sentence. See, the "subject" of a sentence is what the sentence is about! Isn't that neat to know!?

Your comment is flawed, regardless of what spcial relativity says, and regardless, even, of what the subject of your comment was. Even if the subject of your statement had been "toasters" it would still have been flawed.
The statement: "Nothing can travel faster than the speed of light because the speed of light is (the speed of light in a vacuum)." is flawed.
This is because the fact that the speed of light = the speed of light is not sufficient evidence that nothing can move faster than this speed. Even if there is further evidence that nothing can move faster than the speed of light, it does not factor in here, because you did not state such evidence as being the reason that nothing can travel faster than the speed of light. You stated that nothing can travel than the speed of light because the speed of light is the speed of light.
I am aware that the speed of light is the speed of light. It's very fast. Like a racecar!
Did you know that racecar spelled backwards is still racecar?
That's because the driver is going SO FAST that he doesn't know whether he's coming or going!
Isn't that neato!?

I'm sorry, how do you propose to catch up with light if it's always moving away from you at speed c?

My comment is the crux of special relativity. If you'd taken my advice you'd know that by now.