# The Naked Scientists Forum

### Author Topic: What time does the rocket arrive at point B?  (Read 6278 times)

#### pzkpfw

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##### Re: What time does the rocket arrive at point B?
« Reply #75 on: 28/08/2016 00:44:51 »
Basically if you were to look at the Sun the image you are seeing is an approx 8 minute old image and not the actual present image and you see the sun in its past , however from a different look at the situation there is an apparent contradiction.

There is no contradiction. You simply ignore the time it takes light to travel. Your continuous observation can't remove that time.

In your World, what if there were three observers? Z, who is 8 light minutes from X; and Y, who is exactly between them (4 light minutes from X, and 4 light minutes from Z).

It seems that in your World, X, Y and Z would all see each other wave at the same time. Everything (in your World), that occurs at the same time, is seen to occur, at the same time, regardless of distance. Is this a correct result of your claims?
« Last Edit: 28/08/2016 00:47:23 by pzkpfw »

#### Thebox

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##### Re: What time does the rocket arrive at point B?
« Reply #76 on: 28/08/2016 00:47:59 »
OK - I can get with that...

I haven't been following the thread.  I just noticed a post implying that we would see the light of the sun here on earth as it was 8 minutes before when it left the sun... which is not true.

Basically, XYZ thinks that if two people with pre-synchronised clocks, 8 light minutes apart, waved at the "same time", they'd both be seeing each other do that at the moment they waved. i.e. they'd see each other waving at the same time as they are themselves waving. Whereas everyone else says that the two people would see the other persons wave 8 minutes later. If they both waved for 1 minute, their own arm would have stopped waving (for 7 minutes) at the time they see the other persons wave.

We're ignoring all other effects, relativistic or not. In this sort of very very basic topic (light takes time to travel), it's not helpful to nitpick the minutia. This is at the "lies to children" level.

Not quite,

You and I stand nose to nose with our arms in the air with our palms touching, we will set the time on both our clocks to be synchronous and you will depart at 9:00:00am

Can you tell me what time do you see me at 9:00:00am?

An event occurs at A (at 9:00:00), light travels (over a 0 light second distance) to B, B sees the event at A (at 9:00:00).
An event occurs at B (at 9:00:00), light travels (over a 0 light second distance) to A, A sees the event at B (at 9:00:00).

True or false?

#### Thebox

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##### Re: What time does the rocket arrive at point B?
« Reply #77 on: 28/08/2016 00:52:50 »
Everything (in your World), that occurs at the same time, is seen to occur, at the same time, regardless of distance. Is this a correct result of your claims?

That's about it in short but it is only that because of the contradiction.

#### pzkpfw

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##### Re: What time does the rocket arrive at point B?
« Reply #78 on: 28/08/2016 00:57:51 »
Everything (in your World), that occurs at the same time, is seen to occur, at the same time, regardless of distance. Is this a correct result of your claims?

That's about it in short but it is only that because of the contradiction.

The only contradiction is that you agree that light takes time to travel, yet think anyone at any distance can see something at the instant it occurs.

Absolutely mind bogglingly weird.

#### Thebox

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##### Re: What time does the rocket arrive at point B?
« Reply #79 on: 28/08/2016 01:01:11 »
Everything (in your World), that occurs at the same time, is seen to occur, at the same time, regardless of distance. Is this a correct result of your claims?

That's about it in short but it is only that because of the contradiction.

The only contradiction is that you agree that light takes time to travel, yet think anyone at any distance can see something at the instant it occurs.

Absolutely mind bogglingly weird.

It the scenario that's weird and spooky and mind boggling.

An event occurs at A (at 9:00:00), light travels (over a 0 light second distance) to B, B sees the event at A (at 9:00:00).
An event occurs at B (at 9:00:00), light travels (over a 0 light second distance) to A, A sees the event at B (at 9:00:00).

True or false?

On the other forum you have agreed this to be true.

If B travels for 1 light second away from A , what time will it say on both clocks?

#### pzkpfw

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##### Re: What time does the rocket arrive at point B?
« Reply #80 on: 28/08/2016 01:05:22 »
It the scenario that's weird and spooky and mind boggling.

An event occurs at A (at 9:00:00), light travels (over a 0 light second distance) to B, B sees the event at A (at 9:00:00).
An event occurs at B (at 9:00:00), light travels (over a 0 light second distance) to A, A sees the event at B (at 9:00:00).

True or false?

On the other forum you have agreed this to be true.

If B travels for 1 light second away from A , what time will it say on both clocks?

That's from : http://www.scienceforums.com/topic/29357-do-we-see-a-train-arrive-that-arrived-8-minutes-earlier/page-12#entry341330 [nofollow]

I'm not going to waste time giving you the answer here in the same detail as I gave over there when I introduced this to you.

In short:

An event occurs at A (at 9:00:00), light travels (over a 0 light second distance) to B, B sees the event at A (at 9:00:00).
An event occurs at B (at 9:00:00), light travels (over a 0 light second distance) to A, A sees the event at B (at 9:00:00).

True.

But then Real Word:

An event occurs at A (at 9:00:00), light travels (over a 1 light second distance) to B, B sees the event at A (at 9:00:01).
An event occurs at B (at 9:00:00), light travels (over a 1 light second distance) to A, A sees the event at B (at 9:00:01).

And in XYZ World:

An event occurs at A (at 9:00:00), light travels (over a 1 light second distance) to B, B sees the event at A (at 9:00:00).
An event occurs at B (at 9:00:00), light travels (over a 1 light second distance) to A, A sees the event at B (at 9:00:00).

You've yet to explain why it works the way it does in XYZ World.

#### Thebox

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##### Re: What time does the rocket arrive at point B?
« Reply #81 on: 28/08/2016 01:09:29 »

You've yet to explain why it works the way it does in XYZ World.

An event occurs at A (at 9:00:00), light travels (over a 0 light second distance) to B, B sees the event at A (at 9:00:00).
An event occurs at B (at 9:00:00), light travels (over a 0 light second distance) to A, A sees the event at B (at 9:00:00).

True.

An event occurs at A (at 9:00:00), the object  B travels (  1 light second distance) , B sees  A (at 9:00:01).

An event occurs at A (at 9:00:00), the object  B travels (  1 light second distance) , A sees  B (at 9:00:01).

True.
« Last Edit: 28/08/2016 01:14:30 by Thebox »

#### timey

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##### Re: What time does the rocket arrive at point B?
« Reply #82 on: 28/08/2016 01:26:00 »
OK - I can get with that...

I haven't been following the thread.  I just noticed a post implying that we would see the light of the sun here on earth as it was 8 minutes before when it left the sun... which is not true.

Summarised; XYZ thinks that if two people with pre-synchronised clocks, 8 light minutes apart, waved at the "same time", they'd both be seeing each other do that at the moment they waved. i.e. they'd see each other waving at the same time as they are themselves waving. Whereas everyone else says that the two people would see the other persons wave 8 minutes later. If they both waved for 1 minute, their own arm would have stopped waving (for 7 minutes) at the time they see the other persons wave.

We're ignoring all other effects, relativistic or not. In this sort of very very basic topic (light takes time to travel), it's not helpful to nitpick the minutia. This is at the "lies to children" level.
Ah yes - well that is a pretty straightforward scenario. (chuckle)...

But to be fair to Thebox I have found him at times to be weirdly inspirational in his meanderings through physics, and also of some benefit as to humour.  I can forgive a lot of a person who makes me laugh.

As to light only being observable when it has reached the observation reference frame - that is very interesting indeed I find, but not of relevance to the remit of this thread - other than the fact of it being true of course. :D

Box - 8 light minutes is a long distance away.  If the person you were observing waving were in the dark and you had a mega torch with which to illuminate your waving friend, you would have to wait 8 minutes after turning your torch on before the light reached your waving friend in order to illuminate him from his situation of being in the dark.

If we didn't have to wait 8 light minutes to see light emitted from the sun, we'd all be toast.
« Last Edit: 28/08/2016 01:31:54 by timey »

#### Thebox

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##### Re: What time does the rocket arrive at point B?
« Reply #83 on: 28/08/2016 01:43:37 »

Box - 8 light minutes is a long distance away.  If the person you were observing waving were in the dark and you had a mega torch with which to illuminate your waving friend, you would have to wait 8 minutes after turning your torch on before the light reached your waving friend in order to illuminate him from his situation of being in the dark.

If we didn't have to wait 8 light minutes to see light emitted from the sun, we'd all be toast.

Believe me when I say I understand this also, I can not  help it if there is a contradiction.  My scenario gives a different result which is contradiction.

added- What is weird is that the object B arriving at the Sun is seen in the same time frame of reference as that of A, A would see B at 9:08 and B would see A at 9:08 , however if somebody was to raise a flag on arrival at B end,  this event would not be seen by A until 9:16, (scratches head going to bed).

« Last Edit: 28/08/2016 01:54:42 by Thebox »

#### pzkpfw

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##### Re: What time does the rocket arrive at point B?
« Reply #84 on: 28/08/2016 05:07:17 »
An event occurs at A (at 9:00:00), the object  B travels (  1 light second distance) , B sees  A (at 9:00:01).

An event occurs at A (at 9:00:00), the object  B travels (  1 light second distance) , A sees  B (at 9:00:01).

True.

Why? How? What is your evidence for this?

The basis for the common understanding of everyone else, is the relationship between speed, distance and time. How do you refute this?

#### Thebox

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##### Re: What time does the rocket arrive at point B?
« Reply #85 on: 28/08/2016 09:46:27 »
An event occurs at A (at 9:00:00), the object  B travels (  1 light second distance) , B sees  A (at 9:00:01).

An event occurs at A (at 9:00:00), the object  B travels (  1 light second distance) , A sees  B (at 9:00:01).

True.

Why? How? What is your evidence for this?

The basis for the common understanding of everyone else, is the relationship between speed, distance and time. How do you refute this?

The evidence was once everyone admitted the simultaneous sight by using the relationship of speed, distance and time.

photon a to b = 1.s

photon b to a = 1.s

b travelling = 1.s

All 3 of these events happening simultaneously.

« Last Edit: 28/08/2016 09:50:26 by Thebox »

#### Thebox

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##### Re: What time does the rocket arrive at point B?
« Reply #86 on: 28/08/2016 10:31:14 »
diagram

#### Colin2B

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##### Re: What time does the rocket arrive at point B?
« Reply #87 on: 28/08/2016 14:57:01 »
Basically if you were to look at the Sun the image you are seeing is an approx 8 minute old image and not the actual present image and you see the sun in its past
Yes, yes, yes!

however from a different look at the situation there is an apparent contradiction.

The evidence was once everyone admitted the simultaneous sight by using the relationship of speed, distance and time.
No-one has admitted simultaneous sight in the way you mean it

photon a to b = 1.s

photon b to a = 1.s

b travelling = 1.s

All 3 of these events happening simultaneously.
You are confusing events
In your scenario photons a to b and b to a travel simultaneously, starting their journey at 0900 however the photon b to a cannot show object b arriving at b, because the object is still travelling from a - it hasn't yet arrived and won't until 0900.01, it is a different event.
Only when it has arrived at b can a new photon start its journey to a, allowing observer at a to see the arrival at b. Total time 2s.

But to be fair to Thebox I have found him at times to be weirdly inspirational in his meanderings through physics, and also of some benefit as to humour.  I can forgive a lot of a person who makes me laugh.
I agree. It important in any subject to consider the not so obvious and explore possibilities. The ability to think through different scenarios is extremely valuable, however, it is also important to recognise when we have reached a dead end in a particular line of thinking.

This particular rabbit hole is a dead end and unless you intend sampling the bottle marked drink me it really isn't t worth spending more time in wonderland than necessary. I don't intend to.

#### Thebox

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##### Re: What time does the rocket arrive at point B?
« Reply #88 on: 29/08/2016 12:27:17 »

Colin!  I am not stupid, I have clearly shown you  with my word press link that I understand the present information. There is a contradiction Colin and it is not my failure in ''seeing'' this. The failure is on your part , not mine.

Please understand that I understand ''your'' information and working with only 1 second is not very difficult.

I will show you but you just keep seeing ''red'' and are not ''playing'' along so I can show you.

Do you agree that A and B both reflect light towards each other and the speed of the light is constant in either direction?

A yes or no is all that is needed, I will then ask the next question and so on until we reach a point where you will ''see'' the contradiction by all your yes answers.

#### phyti

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##### Re: What time does the rocket arrive at point B?
« Reply #89 on: 29/08/2016 17:08:15 »
Thebox;

Scientists using radar signals reflecting from a device left on the moon, have determined it is receding from earth about 1" per year.
Why do they have to wait 2.5 seconds for the emitted signal to return?

#### Colin2B

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##### Re: What time does the rocket arrive at point B?
« Reply #90 on: 29/08/2016 18:51:06 »
I will show you but you just keep seeing ''red''
No, I only see white light in my mind. We agreed to ignore red shift etc.

and are not ''playing'' along so I can show you.
The reason I'm not playing along is I can see where your confusion lies and to be honest it doesn't fuss me at all whether you can see it or not. In fact I don't think you ever will.
However, I will 'play along' one last time.

Do you agree that A and B both reflect light towards each other and the speed of the light is constant in either direction?
Yes

#### Thebox

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##### Re: What time does the rocket arrive at point B?
« Reply #91 on: 29/08/2016 19:24:48 »

Do you agree that A and B both reflect light towards each other and the speed of the light is constant in either direction?
Yes

Do you agree that both A and B are in the present ?

#### pzkpfw

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##### Re: What time does the rocket arrive at point B?
« Reply #92 on: 29/08/2016 21:25:20 »
Do you agree that both A and B are in the present ?

"in the present" needs very careful definition.

#### Ethos_

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##### Re: What time does the rocket arrive at point B?
« Reply #93 on: 29/08/2016 22:40:15 »

Do you agree that A and B both reflect light towards each other and the speed of the light is constant in either direction?
Yes

Do you agree that both A and B are in the present ?
The word "present" is frame dependent. Do you understand that each frame has it's own personal interpretation of the "present"? But right now, which is my personal "present", I'm simply to sick to argue with you or anyone else Mr. Box................Good day to all!
« Last Edit: 29/08/2016 22:43:11 by Ethos_ »

#### Colin2B

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##### Re: What time does the rocket arrive at point B?
« Reply #94 on: 29/08/2016 22:46:51 »
Do you agree that both A and B are in the present ?
No I don't

The points made by pzkpfw and Ethos are both valid.
From my point of view you are talking about events on a timeline. Sometimes A and B are in the past, sometimes what you might call instantaneously 0. It is best to be specific and say what point on the timeline you are talking about rather than saying past or present.

#### Thebox

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##### Re: What time does the rocket arrive at point B?
« Reply #95 on: 30/08/2016 12:09:40 »
Do you agree that both A and B are in the present ?
No I don't

The points made by pzkpfw and Ethos are both valid.
From my point of view you are talking about events on a timeline. Sometimes A and B are in the past, sometimes what you might call instantaneously 0. It is best to be specific and say what point on the timeline you are talking about rather than saying past or present.

I will simplify for you so you can ignore the subjective of simultaneity.

Do you agree that A and B are both in the present if in the same inertial reference frame next to each other?
« Last Edit: 30/08/2016 12:58:36 by Thebox »

#### Thebox

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##### Re: What time does the rocket arrive at point B?
« Reply #96 on: 30/08/2016 12:13:13 »

Do you agree that A and B both reflect light towards each other and the speed of the light is constant in either direction?
Yes

Do you agree that both A and B are in the present ?
The word "present" is frame dependent. Do you understand that each frame has it's own personal interpretation of the "present"? But right now, which is my personal "present", I'm simply to sick to argue with you or anyone else Mr. Box................Good day to all!

Get well soon Ethos. Thank you for participating.

#### Thebox

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##### Re: What time does the rocket arrive at point B?
« Reply #97 on: 30/08/2016 12:15:35 »
Do you agree that both A and B are in the present ?

"in the present" needs very careful definition.

OK , noted that present definition insists on different time frames, i.e simultaneity, which will not be the case by the end of the thread and yes's by Colin.

#### Thebox

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##### Re: What time does the rocket arrive at point B?
« Reply #98 on: 30/08/2016 13:25:30 »
Do you agree that both A and B are in the present ?
No I don't

The points made by pzkpfw and Ethos are both valid.
From my point of view you are talking about events on a timeline. Sometimes A and B are in the past, sometimes what you might call instantaneously 0. It is best to be specific and say what point on the timeline you are talking about rather than saying past or present.

I will simplify for you so you can ignore the subjective of simultaneity.

Do you agree that A and B are both in the present if in the same inertial reference frame next to each other?

I will predict your yes answer because it is undeniable because I have not got all the time in the world.

B moves away from A , the light between A and B and B and A is constant like you already yes answer shows .

Is there anything in this diagram you do not understand related to B moving away from A?

You can clearly see in this diagram that you still observe B in the present although B has moved away because the sight remains ''simultaneous'' between A and B because of the fact the timing remains constant and simultaneous, they always see each other at the same time and each others present.

If you do not agree with this , then where do you consider it is wrong?

It is hardly rocket science and I am sure anyone can work this out , 1 second of time passes when B is in motion, 1 second passes on A and B's clock,
(ignoring time dilation for now).
They both always see each other at the same time. It takes a total of one second for the light to travel either direction from A to B or vice versus. The light from A to B and vice versus travels from A to B or vice versus for the entire 1 second B is in motion.

#### Thebox

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##### Re: What time does the rocket arrive at point B?
« Reply #99 on: 30/08/2016 13:49:42 »
To simplify if you see something now in your present and it  moves away from you, you always see each other at the same time, I.e the present

#### The Naked Scientists Forum

##### Re: What time does the rocket arrive at point B?
« Reply #99 on: 30/08/2016 13:49:42 »