- #71
Doc Al
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James S Saint said:You do NOT want to lecture me about what logic is or isn't.
James S Saint said:You do NOT want to lecture me about what logic is or isn't.
Of course. But what you don't seem to be getting is that distance and time are with respect to some reference frame.James S Saint said:The "problem" is that speed is ONLY measured by distance and time, agreed?
Sorry, still wrong. A distance of 2 Ls implies some reference frame. In this case, the ground frame.We (my brother and I - the only people involved) measured 2Ls of distance between us. It doesn't matter where we were. It doesn't matter if there was a ground. We could have simply met in space and slowly backed away to a distance of 2Ls. No distortions involved.
Again, only with respect to that ground frame.But 1.333 secs later, we are back where we started.
Nonsense. All it tells you is that with respect to the ground frame, the distances closed at a rate of 1.5c.The "problem" is that we are measuring speed by time and distance which tells us that one of us traveled at 1.5c. We can't really know which one of us. But SOMETHING happened faster than light.
I am trying desperately to keep this as simple as possible. The issue of how fast light might be going here or there is not really the issue.Borg said:I'm still waiting on your explaiination of how fast light travels when it is coming from your brother's ship. I would love to hear how light travels faster than light.
James S Saint said:The "problem" is that we are measuring speed by time and distance which tells us that one of us traveled at 1.5c. We can't really know which one of us. But SOMETHING happened faster than light.
Borek said:Assuming that just because one of them moves at 0.75c means the other can get faster than 0.25c seems wrong to me. Following this line of thinking, what happens to the light emitted by our Sun? If it goes in the direction of the Earth with c, everything emitted in the opposite direction has to stop?
espen180 said:As for the light question, a photon doesn't have an intertial reference frame, you we cannot ask what the world looks like for a photon.
DaleSpam said:Here is the problem. You are starting with a flawed premise. In this arrangement the fastest your brother can possibly be closing with the sign is <0.25c.
Sorry, it's not as simple as you envision. Please answer the question. How fast do you (in your ship) think that the light from your brother's flashlight travels?James S Saint said:I am trying desperately to keep this as simple as possible.
We didn't even know there was a ground. We saw, measured 2Ls. Yet 1.333 secs later, we BOTH saw 0 distance.Doc Al said:Nonsense. All it tells you is that with respect to the ground frame, the distances closed at a rate of 1.5c.
The issue with the light beam was just used to point out the logical consequence of your statements and how they contradict what we know about how light works. There's logic coming to bite you in the butt again!James S Saint said:I am trying desperately to keep this as simple as possible. The issue of how fast light might be going here or there is not really the issue.
It's been answered several times.Now i have even removed the ground from the scenario to simplify further. Someone please just answer this;
James S Saint said:I am trying desperately to keep this as simple as possible. The issue of how fast light might be going here or there is not really the issue.
Now i have even removed the ground from the scenario to simplify further. Someone please just answer this;
Measured 2 Ls according to what frame? 1.333 s according to whom?James S Saint said:We didn't even know there was a ground. We saw, measured 2Ls. Yet 1.333 secs later, we BOTH saw 0 distance.
Again, only as measured with respect to the ground frame.From our perspective, we would not be able to know who "traveled", but only that one of us obviously did. And that one got to the other at 1.5c.
James S Saint said:Yes, but I'm not talking about what a ground observer sees. I see the distance of 2Ls get reduced to 0 in only 1.333 secs. That is what matters. Perhaps I cannot actually see the ground at all or even know it exists. As stated just prior, the ground only serves as an equal frame for us to begin and end. Both of us would end up seeing that 2Ls of distance vanished in only 1.333 secs.
Austin0 said:They would all agree on the simultaneity of the intersection. If they don't steer carefully they could headon and then it would be obvious they met simultaneously. Seriously though, all observers agree on local events at a single location. SImultaneity becomes relevant when events are separated spatially
Does anyone disagree with that post?James S Saint said:We didn't even know there was a ground. We saw, measured 2Ls. Yet 1.333 secs later, we BOTH saw 0 distance.
From our perspective, we would not be able to know who "traveled", but only that one of us obviously did. And that one got to the other at 1.5c.
James S Saint said:Let's see what we CAN agree to. Assuming the floating in space modification to the original OP;
Does anyone disagree with that post?
Of course we disagree with it! Where have you been?James S Saint said:Does anyone disagree with that post?
So everyone agrees that we both measured 2Ls and within 1.333 secs, we both measured 0?espen180 said:Yes. See Post #79, where I have calculated the actual measurements you would make.
Borg said:Sorry, it's not as simple as you envision. Please answer the question. How fast do you (in your ship) think that the light from your brother's flashlight travels?
Ok, what part of THAT post do you disagree with?Doc Al said:Of course we disagree with it! Where have you been?
One traincrash at a time, please. I'll get to it if I can get anywhere with what I am pursuing first.Borg said:Still waiting...
Yes, I completely disagree with your post(s). My question was made to get you to realize the illogic of your assumptions. If you answer the question, you might see that there are problems with your assumptions.James S Saint said:One traincrash at a time, please. I'll get to it if I can get anywhere with what I am pursuing first.
Do you disagree with that post in question and if so with what part?
James S Saint said:So everyone agrees that we both measured 2Ls and within 1.333 secs, we both measured 0?
James S Saint said:A) Now the whole point to relativity is that there is no actual absolute frame, thus neither brother can claim to be the one traveling. All we see is 2Ls of distance vanish in 1.333 secs.
B) We have no means to use the equation involved, because we do not know where ground would be. We do not know who was traveling. ALL we know is that within 1.333 secs, what was 2Ls disappeared.
C) From ALL we know, one of us traveled at 1.5c.
Now which of A,B, and C is disagreeable?
i understand that was your intention and I will respect it, but not yet. I need to find out why people cannot see what I see so very clearly concerning "no absolute frame".Borg said:Yes, I completely disagree with your post(s). My question was made to get you to realize the illogic of your assumptions. If you answer the question, you might see that there are problems with your assumptions.
So you disagree with (A), the very notion of relativity. I think therefore your input is a bit pointless.espen180 said:All of them are wrong. Assuming instant acceleration, the actual situation, in either of the ships' rest frames, is 0.86Ls being traversed in 0.9 secs.
James S Saint said:So you disagree with (A), the very notion of relativity. I think therefore your input is a bit pointless.
And sorry, I had misread your reply just before.
EXACTLY what is in error with (A)?espen180 said:The second part of A is wrong. The distances you report are not those observed by the ship observers, and the time is wrong according to ship observers. Of course I agree with relativity!
Either brother can (and does) view himself as being at rest and the other brother moving towards him.James S Saint said:1) Now the whole point to relativity is that there is no actual absolute frame, thus neither brother can claim to be the one traveling.
Those measurements are only true in the ground frame. As soon as the brothers move, they are no longer at rest in the ground frame. They will use their own measurements of distance and time to measure how fast they move with respect to each other. (If you understand relativity, you can calculate what they will measure.)2) All we see is 2Ls of distance vanish in 1.333 secs.
The second sentence is the very setup to the story. (1) The brothers measured the 2Ls. (2) There was travel between them such that they both saw the distance vanish in 1.333 secs.
James S Saint said:EXACTLY what is in error with (A)?
The statements were;
1) Now the whole point to relativity is that there is no actual absolute frame, thus neither brother can claim to be the one traveling.
2) All we see is 2Ls of distance vanish in 1.333 secs.
The second sentence is the very setup to the story. (1) The brothers measured the 2Ls. (2) There was travel between them such that they both saw the distance vanish in 1.333 secs.
How can that be wrong?
James S Saint said:i understand that was your intention and I will respect it, but not yet. I need to find out why people cannot see what I see so very clearly concerning "no absolute frame".
Not so. Both brothers (and all observers always) see themselves as "the rest frame". That is what relativity is about. There is no actual rest frame for them to assume that they are the one traveling.Doc Al said:Either brother can (and does) view himself as being at rest and the other brother moving towards him.
The only measurements that are made in this scenario is the 2Ls distance and the 1.333 secs duration. They both read the same time change. Neither knows who moved except that they moved with respect to each other.Doc Al said:They will use their own measurements of distance and time to measure how fast they move with respect to each other. (If you understand relativity, you can calculate what they will measure.)
Note that you really aren't answering my questions either. I am trying to narrow exactly where I am actually wrong to one particular incorrect statement (at least). You are not helping with that. I understand that you might have a good point, but like I said. one train wreck at a time, please.Borg said:So you realize that the intention is to get you to see your illogical assumptions but, you're going to continue making statements that are based on those assumptions anyway? You aren't going to get anywhere with this so why not answer the question from post 76 while you're waiting for everyone else to see the light?
The physical impossibility of instant acceleration is not relevant. I could make the scenario where they backed off further and the ships merely took a little extra time to get up to speed. The question would turn out the same. It merely complicates the issue. How fast does a photon accelerate to get up to light speed when it leaves an atom? Certainly not instantly. So is the photon not traveling at the speed of light?espen180 said:Those starting conditions are physically impossible if reported in either of the ships' rest frames.
If reported in the ground frame, the correspond measurements the observers in the ships with make are the ones I gave above and in post #79.
James S Saint said:The physical impossibility of instant acceleration is not relevant. I could make the scenario where they backed off further and the ships merely took a little extra time to get up to speed. The question would turn out the same. It merely complicates the issue. How fast does a photon accelerate to get up to light speed when it leaves an atom? Certainly not instantly.
What do you mean 'not so'? You just repeated back what I said.James S Saint said:Not so. Both brothers (and all observers always) see themselves as "the rest frame". That is what relativity is about. There is no actual rest frame for them to assume that they are the one traveling.
According to what frame? Answer this or this thread is done.The only measurements that make in this scenario is the 2Ls distance and the 1.333 secs duration.
No one is talking about 'absolute' movement. All movement is relative.They both read the same time change. Neither knows who moved except that they moved with respect to each other.
Again, according to what frame?Perhaps, from their perspective, one traveled at .9c and the other at .6c. Or perhaps one at .75 and the other at .75. They cannot know. They have nothing with which to measure such.
ALL they know is that there was 2Ls of distance and 1.333 secs later, there is none.
Oh oh.. I'm sorry. I read your post as "Neither".. my mistake.Doc Al said:What do you mean 'not so'? You just repeated back what I said.
The INITIAL frame, which is also the FINAL frame. It is in that frame that both measurements, both initial and final time and distance, get measured by both parties.Doc Al said:According to what frame? Answer this or this thread is done.
OK, so what's the big issue? In the ground frame, the ships close at 1.5c. So?James S Saint said:The INITIAL frame, which is also the FINAL frame. It is in that frame that both measurements, both initial and final time and distance, get measured by both parties.