Re: The train and the light inside.


tomgee wrote:
PD wrote:
tomgee wrote:
PD wrote:
tomgee wrote:
Spaceman wrote:
"Igor" <thoovler@xxxxxxxxxx> wrote in message
news:1140550474.168851.260960@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
And when did you do your experiment that proved that they don't measure
the same speed c?

The problem is, how could they?
An outside observer could not measure
c for what an inside observer is measuring c for already.
the relative speeds are being ignored if such is true.

It seems that way to you, but I contend that the outside observer has a
faster time rate than has the train because the train is moving faster
than he is,

How do you know that, tomgee?

The same way you know that, PD, since I have told you how over and
over. It's very simple and undeniable. When two objects are at
constant velocity wrt each other, they must be moving at the same speed
and in the same direction. Thus, you and your TV are at CV when you
sit and watch it. However, when you get up to go pee, during the time
you are moving, you are not at CV wrt your TV. Then, you are moving
faster than your TV because at CV both of you are at CV with the planet
also, but when you move, you are moving faster than the TV and the
planet too. The TV and the planet remain at the same speed and moving
in the same direction so they remain at CV wrt each other. But not
you. Once you move from your seat, you are no longer at CV with the TV
and the Earth because you are no longer moving at the same speed and in
the same direction, but now you must move slightly faster than the two
in order to get somewhere else (your potty) and return later to the TV.

It is indeed very simple and not at all what you described.
Let me illustrate with two examples and ask you some pertinent
questions.
Example 1:
Two cars take off from a stop light and both cars accelerate. While
they accelerate, they are not at constant velocity, apparently.
However, if they have the same rate of acceleration, then they stay
abreast of each other and they have zero *relative* motion. Is it your
position still that constant relative motion implies constant velocity
of each?

It is not "apparent" that they are not at CV wrt each other. In fact,
it
would look as if they are, since they are moving abreast of each
other and in the same direction (assuming you meant to say that).
Let's say they are moving at CV as they accelerate,

"Moving at CV" with respect to what? The road? Wouldn't that be
incompatible with the fact that they are accelerating?
"Moving at CV" with respect to each other? That's what I said. They are
not moving *relative* to each other, but that does not mean they are
moving at CV with respect to the road (or anything else). Please reread
what I said and pay attention.

and in such a
case, it can be said that they are at "relative motion" wrt each other.

They cannot be at CV with just "constant relative motion" unless they
are also moving in the same direction as well as moving at the same
speed at any given moment. The difference between CV and your
"constant relative motion" is that CV requires not only that the speed
be identical but that the direction be identical as well.

TomGee, please don't be an idiot. If they are keeping abreast of each
other, of course they are moving in the same direction.

IOWs, you
can
have "constant relative motion" without having CV if the two cars are
moving opposite each other at the exact same speed.

Example 2: I'm sitting on a train headed east at 97 mph. While I'm
sitting, both the train and I have the same constant speed relative to
the earth (97 mph) and our relative speed is zero.

Yes, you do, but you and the train are not at CV wrt to the earth.

What do you call a *constant* 97 mph while I sit there???

What the hell do you think CV means?

You
and the train are at CV wrt each other. It can be said that you, the
train, and the earth are at CV wrt the direction East, but not wrt the
total state of motion of the earth. You are not taking into
consideration
the fact that the earth is also moving through space in a direction
other
than the one in which it rotates.

I said 97 mph *with respect to the earth*. What the earth is doing is
not relevant to that.

Even if the train is moving along
the
plane of its solar orbit, it (and you in it) is moving additional to
the
motion of the earth because it must do so in order to move from one
place to another.

Now I get up because
I have to pee, and I walk toward the restroom at the back of the train.
Now the train is moving 97 mph with respect to the earth, and I'm
moving 94 mph with respect to the track. Is it still your position that
in my getting up and starting to walk at 3 mph, I'm traveling faster
than the train?

Yes. Your motion on the train is the same as the train's motion on the

track. In order for to be able to move from your seat on the train,
you
must move faster than the earth and the train.

The train is going 97 mph with respect to the track, and I'm going 94
mph with respect to the track. How is 94 mph faster than 97 mph?

Do you have ANY idea what you're talking about?


During the time you went off and returned, time for you passed slightly
slower than it did for your TV and the Earth. Meaning that you aged
slightly less than did your TV or the planet. I know it's hard for you
to believe all this, but it's based on SR and the second law of
thermodynamics.

If it so happens that the train is
traveling west, then I think I can argue that the train is traveling
*slower* than the fella on the tracks. Do you see why?

Assuming the experiment declared a certain direction in which the train
is moving, the experiment did not depend on the direction at all since
the two observers were not said to be at CV wrt each other. Direction,
then, does not enter into the experiment, only the fact that one
observer is moving faster than the other.

So, regardless whether I walk to the front of the train or toward the
back of the train (see example 2 above), I'm still traveling faster
than the train.

Yes.

I see. So both 94 mph and 100 mph are both faster than the train's 97
mph with respect to the track.

TomGee, seriously: some of the most amazing things come out of your
fingers when you attempt to think.

PD

.

Relevant Pages

  • Re: The train and the light inside.
    ... Let's say they are moving at CV as they accelerate, ... I'm sitting on a train headed east at 97 mph. ... Yes, you do, but you and the train are not at CV wrt to the earth. ... only you and the train changed speeds and so you are no longer at CV ...
    (sci.physics)
  • Re: The train and the light inside.
    ... the relative speeds are being ignored if such is true. ... faster time rate than has the train because the train is moving faster ... they must be moving at the same speed ... They cannot be at CV with just "constant relative motion" unless they ...
    (sci.physics)
  • Re: The train and the light inside.
    ... Let's say they are moving at CV as they accelerate, ... I'm sitting on a train headed east at 97 mph. ... Yes, you do, but you and the train are not at CV wrt to the earth. ... only you and the train changed speeds and so you are no longer at CV ...
    (sci.physics)
  • Re: The physical lies in SR.
    ... inertial reference frames traveling upon the same ... It is only if the circular defintion for the meter is used. ... Because it was good to base it on a universal constant. ...
    (sci.physics.relativity)
  • Re: WHy is the central line so much faster?
    ... train just took off, we must've been doing 40-50 mph. ... reset to allow operation of the new stock, yet still protect the old from ... This means that acceleration at speeds above 10 to 15 mph is considerably ...
    (uk.transport.london)