michel123456

On 10/2/2020 at 6:29 PM, swansont said:

IOW, there is no frame of reference where the distance is 1 LH and the described trip takes 45 min

However, that is what is shown in animation 1. Look at B's clock.

On 10/3/2020 at 9:48 PM, Janus said:

This is how events unfold according to Earth and Planet x.

B and it clock are length contracted and B's clock is time dilated. The length contraction doesn't really play a role in the out come here.

You yourself looking at your screen are this observer. Which is wrong ( I mean the animation shows something unphysical)

Say that you are this observer: you are located some LHours away, your distance to Earth is D and to planet X is also D (your position is at the summit of an isosceles triangle),  your clock is synchronized to E and X, and you are at rest with E and X.

For you would B (clock T) be time dilated & length contracted? Knowing that your distance to B remains roughly the same.

3 minutes ago, swansont said:

Why won't you address the muon issue?

Because we cannot even agree on simple things.

Like : if your clock looks like running slower for me, then my clock must also look like running slower from you. If I read 60 minutes on my clock & 45 minutes on your clock, then reversely you will read 60 minutes on your clock & 45 minutes on my clock.

Not even that.

.edited because of cross posting

12 minutes ago, swansont said:

But you keep denying relativity, or failing to use it, so this is not a consistently-applied sentiment.

In the example in play, you fail to apply length contraction to a moving frame.

 

Lenght contraction applies instantly for Earth leaving clock T.

But for 1 long hour, for clock T the distance to planet X will not be contracted. Planet X will appear resting at 1LH away. And the signal of departure will appear to come from 1LH away (just like the missile example, in which you had no problem at all to write down that it will be recorded traveling 1 hour & 15 minutes).

You are all very intelligent people here. Why don't you take a rest & take a new look to this thought experiment. There is no danger, and Relativity will not change.

7 minutes ago, swansont said:

The problem is that we have evidence that relativity is true. You can't disprove it with a thought experiment. So you need to look at actual physical evidence to do this. For example, you could finally address Eise's questions about the muon experiment.

I firmly believe that the question IS the thought experiment, and ONLY the thought experiment. Not to say that this thought experiment is bad for Relativity, it suggests some weird effect that I think does not take place.

Relativity is OK, no question about that.

8 minutes ago, swansont said:

In the earth's frame. You persist in not specifying frames of reference.

In the frame at rest. In this case, T is at rest. The Earth goes away (say westward) and planet X arrives (say from eastward).

1 hour ago, Eise said:

OMG...! What 'it'? Which scenario? This is even less clear! 

My guess what your 'argument is point at': the missile travelling from planet X to Earth (With T as static guest...).

• From the Earth's FOR it takes 1:15h. (60Lminutes/0.8c)
• T travels a contracted distance, 0.6 x 1 lh = 36 Lminutes. As he is traveling with 0.8c, this takes him 0:45 according his own clock.

Where is this wrong according you? Please always mention in your reactions:

• your scenario (you are introducing new one after new one, only to feed your intuition to find yet another counter argument...)
• which event or process are you looking at?
• According to which FOR's measurements?
• Looking at the clock and rule of the other FOR or its own FOR?

I do not agree. Your imprecise remarks show that you do not really think through our answers, and this is insulting to the effort Janus, Bufofrog, Swansont, md<somenumberhere>, Markus, and who more. We are all trying to be as precise as possible, and you come with some vague counter argument, shot from the hip.

Tell us e.g. what is wrong with Janus' animations? If nothing, where do you differ in our interpretations of them?

And why do you refuse again and again to take real examples, where we have empirical measurements?

"Tell us e.g. what is wrong with Janus' animations? If nothing, where do you differ in our interpretations of them?"

You don't want me to do that. But since you asked: almost everything is wrong.

More precisely animation 1: (I'll need some time to adjust my answer, please be patient)

On 10/3/2020 at 9:48 PM, Janus said:

This is how events unfold according to Earth and Planet x.

B and it clock are length contracted and B's clock is time dilated. The length contraction doesn't really play a role in the out come here.

This is the view of some "exterior observer" since it does correspond to no FOR (not the Earth, not Planet X, not clock T)

a.From Earth, when clock T starts it is 12.00 on Earth and 11.00 on planet X

b.From Planet X, when clock T starts, it is 13.00 on planet X

You cannot represent facts a & b on this kind of animation.

The only good thing is that clocks on Earth & on planet X are synchronized. But you cannot extract any information from it, expect that clock T ticks slower than the clocks on Earth & planet X, which means that from T, the clocks on Earth & planet X are ticking FASTER (and where is time dilation then?)

c. There is no length contraction in this animation, which as I stated before is WRONG. If you want to represent time dilation, you must represent length contraction too. By length contraction I do not mean the oval shape of T solely, but also its path 0,6 LH long. Where is it?

IOW this animation 1 above is pure garbage.

Now animation 2.

On 10/3/2020 at 9:48 PM, Janus said:

If we now consider things from B's inertial frame of reference, you get this.

B is at rest while the Earth and planet X move to the left at 0.8c.

In this 2nd animation the Earth is leaving at 12:00, so far so good.

But planet X should be applied the delay: clock T does not get the start signal instantly. So, this animation is wrong. And in this "view from other observer" (that corresponds to animation 1) the clocks on Earth & on planet X are not synchronized anymore.

24 minutes ago, Eise said:

No. I know I said it took 1:15h, but I made very clear that this is from the FOR of Earth, X and T (standing still at Earth). Sentences like the above say nothing, unless you say both what event or process, and according to which FOR.  Why can't you stop these imprecise way of speaking. You are just confusing everybody, and most of all yourself. 

STOP IT! Again you use this ambiguous 'seen'. If you do not stop this, i.e., if you keep intentionally vague, I will ask this thread to be closed.

So let's repeat it again:

• the missile travels 1:15h according the FOR of Earth, X, and T in your example above
• the missile travels 1Lh according the FOR of Earth, X, and T in your example above.
• the missile travels 0:45h according the its own FOR (i.e. its own clock)
• the missile travels 0.6Lh  according the its own FOR (i.e. its own odometer)^*

Exactly the same holds when Planet X travels to Earth (replace 'missile' with 'Planet X' in the above 4 lines).

Except that you use 'observe' again: T observes Planet X to arrive 0:15h after it observes Planet X starting to move. But because of signal delay, T rightly concludes that the trip took 1:15h.

But nobody ever said that the trip takes 0:45h from the FOR of Earth and Planet X!!! (except you..)  The '0:45' appears in two (equivalent) ways:

• It is the trip time that T measures on his own clock. For T, he travels only 0.6Lh.
• It is according the FOR of Earth and Planet X the time dilation of T: according Earth's own clock, the trip took 1:15h. But reading the logbook of T, it turns out that T took only 0:45h, i.e. according T's clock. As for the FOR of Earth the distance is still 1Lh, Earth can only conclude that T's clock was slower.

I am wondering how you are thinking. Are you really trying to understand what we write (or animate!!), or do you throw a potential counter example against every step you simply do not understand? 

I proposed several times that you concentrate on real scenarios, i.e. scenarios where we really have measurements. It is an empirical fact that many muons that are created in the upper atmosphere reach the earth's surface. But the halftime of the muons is too short to reach the earth's surface, even if they would travel at near light velocity. Or take muons in an accelerator: where given their half life they could maybe not even make one complete turn through the synchrotron, it is measured that it runs about 30 times through it. This is real stuff, not relativity applied to a science fiction scenario. 

 

^*So Earth, X, and T on one side, and the missile on the other side, agree about their relative velocity: 

• From Earth, X, and T: 60 LMinutes / 75 minutes = 0.8c
• From the missile: (0.6 x 60 LMinutes)/45 minutes = 0.8c.

"Exactly as it should be."

No.

27 minutes ago, Eise said:

I know I said it took 1:15h, but I made very clear that this is from the FOR of Earth, X and T (standing still at Earth)

In its FOR, T is at rest. There is NO REASON why it would give a different result.

29 minutes ago, Eise said:

STOP IT! Again you use this ambiguous 'seen'. If you do not stop this, i.e., if you keep intentionally vague, I will ask this thread to be closed.

Cool down.

I am the one who has been insulted, not you.

32 minutes ago, Eise said:

For T, he travels only 0.6Lh.

My understanding is different (let me be wrong). I thought that Relativity gives you the result of what happen in the other FOR, not what happens in your own FOR. IOW for the Earth ,T is time dilated, and for Earth, T is length contracted.

In its own FOR, nothing happens to T. (I am trying to avoid the words "see" & "observe" that annoy you so much).

In the FOR of T :

1. The departure time of the Earth is recorded at 12:00.

2. The departure time of planet X is recorded at 13:00 (1 hour after its actual departure)

3.The arrival time of planet X is recorded at 13:15 (15 minutes after the arrival of the signal from the departure).

In the FOR of T,standing at rest, the travel was 1h15min.

It is not possible that T records only 45 minutes. That would mean that planet X is arriving before the signal.

Quino. R.I.P.

6 hours ago, swansont said:

10 hours ago, michel123456 said:

Thank you for the animations, very enlightening.

So let me see if I understand correctly:

If all three are at rest (clock T standing on Earth & planet X at rest) and a missile M is sent from planet X to Earth at 0.8c, how long will it take (as seen from T & Earth) to reach the Earth (and T)?

1:15

It’s no different than the trip in the other direction.

6 hours ago, Eise said:

When you actually mean 'observes' with 'seen': Earth will only see that the missile started from X after one hour, the time light takes to reach Earth. But then, oh shock, the missile arrives only 15 minutes later. So it looks as if the missile took only 15 minutes. But the earth observer is not so stupid. He knows that he got the signal of the missile's start after 1 hour. So he concludes that the trip took 1 hour and 15 minutes. So it all fits.

We all agree that the missile took 1hour and 15 minutes.

Now, replace the missile by planet X itself. Simply change the label M (missile) with Planet X.

How much time does it take, as seen by clock T (at rest) to see planet X come. The answer is the same: Earth Clock T will only see that the missile Planet X started from X after one hour, the time light takes to reach Earth clock T. But then, oh shock, the missile planet X arrives only 15 minutes later. So it looks as if the missile planet X took only 15 minutes. But the earth clock observer is not so stupid. He knows that he got the signal of the missile's planet x start after 1 hour. So he concludes that the trip took 1 hour and 15 minutes. So it all fits.

That is exactly what T clock observes in its FOR. 1:15. that is the time interval  between the departure of the Earth & the arrival of planet X.

And not 45 minutes.

13 hours ago, Janus said:

However, due to Relativity of Simultaneity, the Planet X clock already reads 48 min later than Earth's clock when B and the Earth are next to each other. Thus the 27 minutes it advances brings it to 1 hr 15 min, as it passes B.  The times on Earth's clock and B's clock when they are next to each other agree with the first animation, and the Times shown on B's clock and Planet X's clock when they are next to each other also agree with the first animation.

Thank you for the animations, very enlightening.

So let me see if I understand correctly:

If all three are at rest (clock T standing on Earth & planet X at rest) and a missile M is sent from planet X to Earth at 0.8c, how long will it take (as seen from T & Earth) to reach the Earth (and T)?

20 hours ago, swansont said:

Nobody is claiming the clock traveled 1LH in 45 minutes. You said “When you combine 1LH of distance and 45 min of travel, it is wrong.” and I agree: a wrong claim that nobody has made, is wrong. The only person who brought this up is you, with the implication that this argument exists somewhere. 

 

It’s fine that you say this. It’s true. It’s what everybody has explained. What’s not fine is the implication that anyone has suggested that it’s not the case. What’s the point of deny something that nobody is claiming?

 

 

 

If you read the example from Janus, you will see that time dilation is included while length contraction is forgotten: here below in bold where it is argued that the clock reads 45 min. when arriving.
 

Quote

 

So let's work out a couple of examples:

Assume you are situated 1 light hr from a stationary(to you) clock that is synchronized to your own clock (when your clock reads 12:00, it reads 12:00)

You looking at this clock when your clock reads 12:00 will visual see the clock as reading 11:00. (since it took the light carrying that image 1 hr to travel from the other clock, to get to you when your clock reads 12:00, it had to leave the other clock when it read 11:00)

 

A third clock travels from your position to the second clock at 0.8c

Using the formula above we find that you will see it tick 1/3 as fast as your own. It will arrive at the second clock in 1.25 hrs when the second clock reads 01:15. But because of the light travel time lag between you and the second clock, you will not see this until until your clock reads 02:15. This means the you will watch the third clock recede for 2.25 hrs by your clock while seeing it ticking 1/3 as fast and thus if it read 12:00 when it left you, you will see it arriving at the second clock reading 12:45. So in the 1:15 it took to make the trip it only ticked off 45 min. (remember, even though you didn't see the third clock arrive until your clock read 02:15, it had actually arrived an hour earlier.)

 

Now let's do a reverse trip. you see the second clock read 01:15 and the third clock reads 12:45 when your clock reads 02:15, however this image of those two clocks left 1 hr ago, so the third clock left the second clock when your clock read 01:15 (in other words, if the third clock turns around and heads back the moment it reaches the second clock, by the time you see this, the third clock is already well along its trip back to you.). The return trip takes the same 1.25 hrs, which means it arrive back at you when your clock reads 02:30. This means that you will see its entire return trip occur during the 15 min between 02:15 and 02:30. At a accelerated tick rate of 3 you will see the third clock tick off 45 min during that period, and read 01:30 upon arrival, when your clock reads 02:30. So again, it ticked off 45 min during the 1.25 hr trip, the same as for the outbound trip and accumulated at total of 1.5 hrs for your 2.5 hrs.

 

Let's see the question from the FOR of the traveling clock: the clock is constantly at rest, the Earth & planet X are moving.

At 12:00, the clock T is at rest. For some mysterious reason the Earth goes away at velocity 0,8c. At the same instant, at 12:00 on planet X (that is synchronized with Earth), planet X starts toward T, also at velocity 0,8c.

Regarding the Earth: clock T sees Earth going away immediately, there is motion, and thus there is time dilation & length contraction.

BUT regarding planet X, there is a delay: clock T continues to see planet X at rest, at distance 1LH. There is no motion yet, there is no length contraction yet, there is no time dilation yet. Motion of planet X will appear after the delay has passed, that is to say after 1 hour.

IOW after 1 hour Earth has left, clock T will see planet X start its travel.

If you agree with the above then you may also re-estimate the 45 minutes mentioned by Janus: 45 minutes is less than 1 hour, so that would mean that planet X would have arrived at T before the signal transmitted by light. This is impossible: the 45 min are wrong.

In fact, after waiting 1 hour, clock T will see planet X rush and crash on clock T after 15 minutes. The dial on clock T will show 1h & 15 minutes for the trip, or 75 minutes.

44 minutes ago, swansont said:

The traveling clock observed the trip’s length to be contracted.

The clock is observing itself at rest. The "length of the trip" is the distance between 2 moving objects (the Earth & planet X)

7 minutes ago, swansont said:

And yet you’re the only on pairing those two values.

????????????? I am the one? who says that the clock traveled 1LH in 45 minutes?

I said that in Earths frame, the clock traveled 45 minutes until 0,6 LH, that it has to travel another 30 minutes to reach planet X , total trip 75 minutes.

I say that you cannot apply time dilation alone, or length contraction alone, you must use both, otherwise you don't get the 0,8c.

34 minutes ago, swansont said:

IOW, there is no frame of reference where the distance is 1 LH and the described trip takes 45 min.

Yes exactly.

44 minutes ago, Eise said:

Because it is T that is traveling with 0.8c in Earth's and X's FOR. It is traveling the contracted distance between Earth and X.

There is also length contraction of T seen from Earth, but only for what is moving, i.e. T's rocket. It is shorter from the FOR of Earth and X. But Earth and X are not traveling from the exhaust and the frontside of the rocket in your scenario.

In T' s FOR, the Earth is traveling. And Planet X is traveling.

1 hour ago, Eise said:

• From FOR of the Earth there is no length contraction, but only time dilation on the clock of T
• From FOR of T, there is only length contraction of the distance Earth -> X, but no time dilation on his own clock

Why such a difference? Earth & T should be reversible. Why is there length contraction on the other & no time dilation? Who made the choice?

59 minutes ago, Eise said:

From earth one sees the moment of arriving of T at X and looks at its clock, it only shows 45 minutes.

That is exactly what I say: from Earth we are taking count of time dilation (looking at the clock) without taking count of length contraction (that shows nowhere). It is a mistake.

As seen from the Earth, we should look at both length contraction & time dilation, in such a way that when the clock ticks 45 minutes, the distance traveled is 0,6 LH.

44 minutes ago, Eise said:

You are mixing up two things;

- in Earth's and X's FOR the distance between them simply does not change because some spaceship happens to travel from Earth to X.

- However, T is moving in this FOR, and so its spaceship and everything on board is length contracted.

Apply md65536's criteria: is it moving?

• no --> no length contraction (the distance between Earth and X is not moving!)
• yes --> that what is moving is length contracted (and time dilated)

I would say: for the traveler the distance between Earth and X is length contracted.

Just as the shadow of an object can be shorter as the object itself: it really is shorter. (a shadow is a projection of the object on the horizontal plane). Maybe (maybe...) it helps to see it that way. Two different inertial frames have different projections of events (and distances between events) on their respective time and space axes. But the observers agree on 'the real length' between two events , i.e. the distance as defined in Minkowskian spacetime.

I have no much problem with all of that.

You wrote:
 

Quote

 

Apply md65536's criteria: is it moving? (...)

yes --> that what is moving is length contracted (and time dilated)

 

So what about what I wrote:

2 hours ago, michel123456 said:

With 1LH of distance and 75min of travel you get 0,8c (which was the assumption)

With 0,6LH of distance and 45min of travel you get 0,8c (which was the assumption)

And everything is fine.

BUT

When you combine 1LH of distance and 45 min of travel, it is wrong.

In the twins paradox, that is exactly what happens: it is argued that, as seen from Earth, the twin traveled 1LH in 45 minutes. So the traveling twin is younger than his brother. There is a mistake somewhere.

35 minutes ago, Eise said:

What an observer from Earth sees is time dilation:

And no length contraction? An observer never observes a particle flatten?

Or to say it otherwise:

As viewed by the traveling clock, what is the distance between Earth & Planet X? You wrote:

40 minutes ago, Eise said:

According T however, the distance between Earth and X is length contracted 0.6 x 1Lh

So, I understand that the traveling clock is observing length contraction.

Let's say it differently

With 1LH of distance and 75min of travel you get 0,8c (which was the assumption)

With 0,6LH of distance and 45min of travel you get 0,8c (which was the assumption)

And everything is fine.

BUT

When you combine 1LH of distance and 45 min of travel, it is wrong.

5 hours ago, Eise said:

Right. So why do you say then something like this?

 

I should have said : When length contraction is applied, Earth see the length traveled by the clock <in 45 minutes> as contracted by a factor of 0.6.

4 minutes ago, Eise said:

 

So how much does the clock travel? 1LH or 0.6 x 1LH?

 

That is the question.

IMHO if the clock reached destination, as seen by Earth it has traveled 1LH. If it traveled 0,6 LH (as seen by Earth) it has not reached destination. Because in Earth's FOR, the destination did not moved. As seen by Earth, at 0,6 LH away, there is no planet X.

5 minutes ago, Eise said:

No, you are not, and the syndrome that Swanson, Markus, md65536, Janus, Bufofrog, and I  have, is that we have a more than superficial knowledge of relativity.

Let's assume, as you do, that Earth and planet X are in the same inertial frame. Two spaceships, T1 and T2 (Traveler) make up for planet X, 1 light hour away. T1 travels with 0.8c, and T2 with 0.6c.

What is the distance from Earth to Planet X?

When T1 arrives at Planet X how far did T1 travel from the view of Earth's and planet X's FOR?

When T1 arrives at Planet X how far did T2 travel from the view of Earth's and planet X's FOR?

So how far is planet X from Earth?

 

In your opening statement you wrote that planet X is 1 light hour away. From Earth.

And from planet X, the Earth is 1 LH away.

So it is 1 LH in all cases.

The lack of comments gives a mixed feeling...

15 hours ago, Eise said:

17 hours ago, michel123456 said:

The earth sees the traveling clock ....<insert your comment here>

... length contracted. But not the length traveled.

I hope that I am misreading your comment and that you don't suffer from the same syndrome with Swansont in this post:

On 9/23/2020 at 5:39 PM, swansont said:

Is the “length” moving? No. So it’s not contracted.

On 9/23/2020 at 6:33 PM, swansont said:

On 9/23/2020 at 5:48 PM, The victorious truther said:

In the description is declares that it's a row of dice moving. Not a single (die) pictured at different times while it was moving if I recall correctly. 

My mistake. The questions are still focusing on irrelevant details, given the fundamental misunderstanding of relativity.

The Earth sees the traveling clock length contracted. No matter if there is a rod between the clock & Earth, contraction is observed in all cases. It is a geometric effect, it does not act on material things only, it acts on everything.

14 hours ago, md65536 said:

All from the Earth's viewpoint:

Is the traveling clock moving?

Is a ruler attached to the traveling clock moving?

Is a ruler attached to the Earth moving?

Do you know which are length contracted?

My answers in bold below for clarity (not shouting).

All from the Earth's viewpoint:

Is the traveling clock moving? Yes the clock is moving

Is a ruler attached to the traveling clock moving? No, it does not matter.

Is a ruler attached to the Earth moving? No, it does not matter

Do you know which are length contracted? Yes. From the Earth's viewpoint the traveling clock is contracted, the distance that it travels is contracted, its time is dilated.

Also from the Earth's viewpoint, the destination (planet X at coord y on the diagram) is not moving. So the distance from Earth to planet X is still 1 LY: this distance is not length contracted.

The question is: after 45 minutes (as read by the Earth on the traveling clock), did the traveler reach destination? (as observed by Earth)

My answer is No: after 45 minutes (as read by the Earth on the traveling clock), the traveler has moved 0,6 LY (as seen by the Earth). It misses destination by 30 minutes (as read by the Earth on the traveling clock), and 0,4 LY (as seen by the Earth).

7 hours ago, Eise said:

The earth sees the travelling clock running slower by a factor of 0.6.

Yes, OK. The earth sees the travelling clock running slower by a factor of 0.6.

And what about length contraction?

The earth sees the traveling clock ....<insert your comment here>

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