Relativity - Oh dear, here we go again!

You are getting tripped up on this existence concept.

Things don't exist within a reference frame. Things simply exist. The reference frame provides a point of view for measurements of the thing.
 
ynot said:
Let me try to explain what I mean in planet X language. A particular thing “at rest“ (non-accelerating) is in a particular “burp”. Anything and everything else in the universe that’s not moving relative to this particular thing is also in the same “burp”. Anything and everything that is moving relative to this particular thing are in different “burps”. A thing “at rest” in a particular “burp” cannot simultaneously exist in any other “burp”. A thing can’t be moving relative to a "burp" and still be in that “burp”, because that different movement puts it in a different “burp”.
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Ok. I think it's pretty clear what you mean by "in reference frame X". But everyone else says "motionless relative to reference frame X" for the same idea. So you might as well say that too, instead of "in".
 
69dodge said:
Ok. I think it's pretty clear what you mean by "in reference frame X". But everyone else says "motionless relative to reference frame X" for the same idea. So you might as well say that too, instead of "in".
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I’m not talking about reference frames and didn‘t mention them in what I wrote. On planet X no one knows about relativity. All we know on planet X is that some things move relative to other things and some don’t. The things that don’t move relative to other things are in a particular “burp” with those things. Everything else is in different “burps”. Please pretend for a minute that you’re from planet X.
 
robinson said:
And in any inertial frame you can imagine.
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Now I distinctly remember you saying that you are the resident comedian.
Please do not say anything serious again.
Some poor chap struggling with this may think this is wrong.

regards,
BillyJoe
 
ynot said:
I’m not talking about reference frames and didn‘t mention them in what I wrote. On planet X no one knows about relativity. All we know on planet X is that some things move relative to other things and some don’t. The things that don’t move relative to other things are in a particular “burp” with those things. Everything else is in different “burps”. Please pretend for a minute that you’re from planet X.
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I don't know where you're going with this.

Ok. I'm pretending that I'm from planet X. Now what?
 
jsfisher said:
You are getting tripped up on this existence concept.

Things don't exist within a reference frame. Things simply exist. The reference frame provides a point of view for measurements of the thing.
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But things don’t exist in isolation, they exist with other things that they either do or don’t move in relation to. The other things that they don’t move in relation to I have been describing as being in the same inertial frame. Apparently this is wrong, so I now describe them as being in the same “burp”.
 
69dodge said:
I don't know where you're going with this.

Ok. I'm pretending that I'm from planet X. Now what?
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Can you understand what I’m trying to say any better when you don’t apply any functions and terms of relativity?
 
ynot said:
But things don’t exist in isolation, they exist with other things that they either do or don’t move in relation to. The other things that they don’t move in relation to I have been describing as being in the same inertial frame. Apparently this is wrong, so I now describe them as being in the same “burp”.
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They are not in the same inertial frame. Your things are motionless with respect to the same inertial frame. Big difference. Frames are not something you are either in or not in. ("with respect to" = "relative to".)

Things that exist all exist independent of any reference frame (inertial or otherwise). The reference frame simply provides a point of view from which measurements can be made.
 
ynot said:
That’s exactly what I meant (and what I thought I had said). :confused:

I’m not talking about whether things can be observed or measured from other inertial frames. Just that they can and do only actually exist in one inertial frame at a particular time (not two or more at once). So is that correct?
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Yes. And by that I mean no. :rolleyes: Seriously, you really should try to learn the definitions that everyone else is using. The answer to the question you meant to ask is yes, but the answer to the question you asked is no.

ynot said:
Let me try to explain what I mean in planet X language. A particular thing “at rest“ (non-accelerating) is in a particular “burp”. Anything and everything else in the universe that’s not moving relative to this particular thing is also in the same “burp”. Anything and everything that is moving relative to this particular thing are in different “burps”. A thing “at rest” in a particular “burp” cannot simultaneously exist in any other “burp”. A thing can’t be moving relative to a "burp" and still be in that “burp”, because that different movement puts it in a different “burp”.
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You're making this much more complicated than it needs to be. The way you have explained it, "be in a burp" means "have a velocity" and "be in another burp" means "have another velocity". You could have just asked about velocities instead of inertial frames or "burps". And yes, if object B has a different velocity than object A, they don't have the same velocity. You got that right.

I wonder how much progress this discussion can make when it takes a hundred posts to sort out something like this.
 
ynot said:
Can you understand what I’m trying to say any better when you don’t apply any functions and terms of relativity?
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Nothing anywhere can get out of any refererence frame. OK?

If you ignore English, do your words make sense in Swahili?
 
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Fredrik said:
Yes. And by that I mean no. :rolleyes: Seriously, you really should try to learn the definitions that everyone else is using. The answer to the question you meant to ask is yes, but the answer to the question you asked is no.


You're making this much more complicated than it needs to be. The way you have explained it, "be in a burp" means "have a velocity" and "be in another burp" means "have another velocity". You could have just asked about velocities instead of inertial frames or "burps". And yes, if object B has a different velocity than object A, they don't have the same velocity. You got that right.

I wonder how much progress this discussion can make when it takes a hundred posts to sort out something like this.
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Yeah, yeah, yeah . . . Velocities . . . Doh! - Thanks for pointing out the obvious. :o

Perhaps I sholuld stick to reading Mickey Mouse comics.

ETA - But why does Goofy walk and talk like a human but Pluto doesn’t? They’re both dogs aren’t they?
 
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ynot said:
Can you understand what I’m trying to say any better when you don’t apply any functions and terms of relativity?
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I already understood what you were trying to say, and I said so. (Maybe I wasn't clear?) I just pointed out that you were using different words to say what you were trying to say than other people would use to say the same thing.
 
ynot said:
Are we talking reference frames or inertial frames, and is there a difference?
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Well not all reference frames are necessarily inertial frames, but any inertial reference frame contains the whole universe because you can see things move in an inertial reference frame.

Non inertial reference frames are accelerating or spinning, and as such normal physics does not apply and you can get results that seem to make little sense like the twins paradox.
 
According to relativity, there’s length contraction and time dilation when a body is moving:
Will the object still contract if it has negative velocity?:confused:
 
Ali said:
According to relativity, there’s length contraction and time dilation when a body is moving:
Will the object still contract if it has negative velocity?:confused:
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You are missing the point about relativiity:

According to relativity, there’s relative length contraction and relative time dilation when a body is moving relative to another body.

If that body now has a negative velocity, that means it is travelling in the opposite direction that it was travelling originally. It will still have length contraction and time dilation relative to the other body. Why would it not?


And vice versa.
...if you don't understand this, you are missing the point about relativiity. ;)


regards,
BillyJoe
 
If a body moves towards me, what will happen to its size relative to me?
If a body moves away from me, what will happen to its size relative to me?
 
Ali said:
If a body moves towards me, what will happen to its size relative to me?
If a body moves away from me, what will happen to its size relative to me?
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If you look at the length contraction formulas, you'll see that velocity enters as v2. So the sign doesn't matter. Whether it's moving towards you or away from you makes no difference.
 
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