# Thread: All Motion is Relative?

1. Is there any number for a "true" speed.

Everyone knows that even if you are standing still on earth you are flying around in orbit of the sun at Xm/s. This galaxy is also moving faster and faster according to what I have read about expanding universe.

So how would you measure the speed of earth itself total, not in reference to the sun, not in reference to the galaxy?

Is there a unit for this? You would need a "center" of the universe to do that I think.

Also, once you guys help me answer that I have a secondary question to further that first one. So lets say we are moving at "true" 1,000M/s if I turn on a flashlight then wouldn't the light be travelling 1,000M/s + c thus breaking the laws of physics?

If not, then in the future if everything keeps expanding and moving faster wouldn't ever piece of matter be moving at the speed of light? Meaning no matter could move in the direction they are "expanding" at as it would be going over the speed of light.

2.

3. Originally Posted by ScienceNoob
Is there any number for a "true" speed.
299,792,458 metres per second.
The speed of light in a vacuum.

4. Originally Posted by ScienceNoob
Is there any number for a "true" speed.
No.
All speeds are relative. (Except for light).

So how would you measure the speed of earth itself total, not in reference to the sun, not in reference to the galaxy?
You can't.
Earth's speed always has to be relative to something.

Is there a unit for this? You would need a "center" of the universe to do that I think.
Nope. And there isn't a centre of the universe.

Also, once you guys help me answer that I have a secondary question to further that first one. So lets say we are moving at "true" 1,000M/s if I turn on a flashlight then wouldn't the light be travelling 1,000M/s + c thus breaking the laws of physics?
Since there isn't any such thing as a "true speed" the question doesn't arise.

If not, then in the future if everything keeps expanding and moving faster wouldn't ever piece of matter be moving at the speed of light? Meaning no matter could move in the direction they are "expanding" at as it would be going over the speed of light.
Not quite true: any "faster than light movement" isn't so much a "speed" as the fact that space between galaxies is "expanding". The galaxies aren't travelling at such velocities.

5. Originally Posted by RedPanda
Originally Posted by ScienceNoob
Is there any number for a "true" speed.
299,792,458 metres per second.
The speed of light in a vacuum.
Yeah c, but I was asking if there is a true measurement of your velocity. Because right now if I drive a car down the road 10M/s, I am really travelling much faster. Adding on the velocity of the earth around the sun and the rotation of the earth and that our solar system is moving and the galaxy that is in is moving and so forth.

So is there any number for "true" velocity?

6. Originally Posted by Dywyddyr
Originally Posted by ScienceNoob
Is there any number for a "true" speed.
No.
All speeds are relative. (Except for light).

So how would you measure the speed of earth itself total, not in reference to the sun, not in reference to the galaxy?
You can't.
Earth's speed always has to be relative to something.

Is there a unit for this? You would need a "center" of the universe to do that I think.
Nope. And there isn't a centre of the universe.

Also, once you guys help me answer that I have a secondary question to further that first one. So lets say we are moving at "true" 1,000M/s if I turn on a flashlight then wouldn't the light be travelling 1,000M/s + c thus breaking the laws of physics?
Since there isn't any such thing as a "true speed" the question doesn't arise.

If not, then in the future if everything keeps expanding and moving faster wouldn't ever piece of matter be moving at the speed of light? Meaning no matter could move in the direction they are "expanding" at as it would be going over the speed of light.
Not quite true: any "faster than light movement" isn't so much a "speed" as the fact that space between galaxies is "expanding". The galaxies aren't travelling at such velocities.

Thanks for the response ok let me propose the following situation to you and perhaps you can shed some light on it

Lets say I am in a car going <--- and another person is in a car going ---> both at 1M/s

I Shine a light <--- wouldn't the person going ---> see the light at c + 2M/s?

If not why?

7. Originally Posted by ScienceNoob
I Shine a light <--- wouldn't the person going ---> see the light at c + 2M/s?
Light is ALWAYS seen as travelling at c.

If not why?
Because light moves at the speed of light (short answer).
It's what relativity is founded upon: c is c for any observer.

8. Being able to detect very small amounts of time, would it be possible to send a light beam in several different directions and receive a reading that would show us which direction we are moving, and use that directional information to figure out how fast we are moving?

9. By 'receive a reading' you mean detecting the reflected photons. That would tell you how far away an object was, whether you are approaching it or receding from it, and your relative velocities. But there must be an object there.

10. Originally Posted by AlexG
By 'receive a reading' you mean detecting the reflected photons. That would tell you how far away an object was, whether you are approaching it or receding from it, and your relative velocities. But there must be an object there.
would it work if we used satellites that could detect an emitted signal and record time?

11. It's called GPS. Your cell phone probably has it.

12. So why can't we detect our speed of motion through space, relative to only to c?

13. c is a velocity. You can't measure relative to a velocity. Furthermore, c is measured to be the same no matter what your relative velocity is no mater what your relative direction of motion is. You can only detect motion through space relative to something else.

14. If we are moving through space at say 100mps and we shot a beam in the direction we where moving, would it not arrive at c-100mps?

15. Originally Posted by keeseguy
If we are moving through space at say 100mps and we shot a beam in the direction we where moving, would it not arrive at c-100mps?
No. We would measure the speed of the beam as being c. The object hit would measure the speed of the beam as being c. Everything, everywhere, regardless of it's relative motion would measure the beam of light as being c.

Light's funny like that.

16. If we were in a bus traveling at c. I sitting in the back turn on my flash light, you would never see the beam, right?

17. Wrong. I'd see your beam and measure it as moving at c. c is measured to be the same in every frame of reference.

18. Originally Posted by AlexG
Originally Posted by keeseguy
If we are moving through space at say 100mps and we shot a beam in the direction we where moving, would it not arrive at c-100mps?
No. We would measure the speed of the beam as being c. The object hit would measure the speed of the beam as being c. Everything, everywhere, regardless of it's relative motion would measure the beam of light as being c.

Light's funny like that.
I think he is saying something like a sonar system but with light. Shoot out beam of light see how long it takes to come back am I right?

19. Originally Posted by ScienceNoob
Originally Posted by AlexG
Originally Posted by keeseguy
If we are moving through space at say 100mps and we shot a beam in the direction we where moving, would it not arrive at c-100mps?
No. We would measure the speed of the beam as being c. The object hit would measure the speed of the beam as being c. Everything, everywhere, regardless of it's relative motion would measure the beam of light as being c.

Light's funny like that.
I think he is saying something like a sonar system but with light. Shoot out beam of light see how long it takes to come back am I right?
That would be called Radar. Or a laser range finder.

That's not his question. It's actually something Einstein thought about when he was a student. If he was riding his bicycle at the speed of light, and he turned on his headlight, what would he see?

20. Originally Posted by AlexG
Originally Posted by ScienceNoob
Originally Posted by AlexG
Originally Posted by keeseguy
If we are moving through space at say 100mps and we shot a beam in the direction we where moving, would it not arrive at c-100mps?
No. We would measure the speed of the beam as being c. The object hit would measure the speed of the beam as being c. Everything, everywhere, regardless of it's relative motion would measure the beam of light as being c.

Light's funny like that.
I think he is saying something like a sonar system but with light. Shoot out beam of light see how long it takes to come back am I right?
That would be called Radar. Or a laser range finder.

That's not his question. It's actually something Einstein thought about when he was a student. If he was riding his bicycle at the speed of light, and he turned on his headlight, what would he see?

21. Originally Posted by ScienceNoob
Originally Posted by AlexG
Originally Posted by ScienceNoob
Originally Posted by AlexG
Originally Posted by keeseguy
If we are moving through space at say 100mps and we shot a beam in the direction we where moving, would it not arrive at c-100mps?
No. We would measure the speed of the beam as being c. The object hit would measure the speed of the beam as being c. Everything, everywhere, regardless of it's relative motion would measure the beam of light as being c.

Light's funny like that.
I think he is saying something like a sonar system but with light. Shoot out beam of light see how long it takes to come back am I right?
That would be called Radar. Or a laser range finder.

That's not his question. It's actually something Einstein thought about when he was a student. If he was riding his bicycle at the speed of light, and he turned on his headlight, what would he see?

Electromagnetic waves. That's just what light is, in a different part of the electromagnetic spectrum.

22. From the questions above, can we say that GR predicts;

c + would result in a blue shift of the light while the speed remains at c
c - would result in a red shift of the light while the speed remains at c
?

23. It's not GR, it's Maxwell's equations, but yes. Frequency changes, velocity doesn't.

24. Originally Posted by AlexG
It's not GR, it's Maxwell's equations, but yes. Frequency changes, velocity doesn't.
Interesting, I'll need to check that out.

I thought it was part of the Doppler effect.
The Doppler effect (or Doppler shift), named after the Austrian physicist Christian Doppler, who proposed it in 1842 in Prague, is the change in frequency of a wave (or other periodic event) for an observer moving relative to its source. It is commonly heard when a vehicle sounding a siren or horn approaches, passes, and recedes from an observer. Compared to the emitted frequency, the received frequency is higher during the approach, identical at the instant of passing by, and lower during the recession.
and
For waves which do not require a medium, such as light or gravity in general relativity, only the relative difference in velocity between the observer and the source needs to be considered.
Doppler effect - Wikipedia, the free encyclopedia

25. Originally Posted by ScienceNoob
Originally Posted by AlexG
Originally Posted by keeseguy
If we are moving through space at say 100mps and we shot a beam in the direction we where moving, would it not arrive at c-100mps?
No. We would measure the speed of the beam as being c. The object hit would measure the speed of the beam as being c. Everything, everywhere, regardless of it's relative motion would measure the beam of light as being c.

Light's funny like that.
I think he is saying something like a sonar system but with light. Shoot out beam of light see how long it takes to come back am I right?
Yes, if we have a satellite at a know distance in orbit, and a beam is shot at it, say we are moving at 1/2c at 0° our beam can only travel 1/2c, at 90° it would travel c, at 180° it would get there quicker. Sonar it a measure of reflection, which may not work, I was considering measuring only the time until reception.

26. Originally Posted by keeseguy
If we were in a bus traveling at c. I sitting in the back turn on my flash light, you would never see the beam, right?
No bus can travel at c. Only massless particles (like photons and gravitons) can travel at c.

27. say we are moving at 1/2c at 0° our beam can only travel 1/2c,
No. The beam ALWAYS travels at c. Velocity addition does not work for light. You've been told this many times now, and keep misunderstanding. I can only assume that it's a purposeful misunderstanding and you're simply a trolling crank.

28. Originally Posted by keeseguy
If we were in a bus traveling at c. I sitting in the back turn on my flash light, you would never see the beam, right?
Let's change this to a bus moving at 0.99c, since, as already point out in an earlier post, massive objects cannot travel at c.

For us, traveling in the bus, the light will travel at c relative to the bus. If the bus is 10 m long, it will take ~ 1/30,000,000 of a sec for the light to travel from back to front.

However, for someone standing on the road, this same light travels at c relative to the road. For him, the light has to "chase after" the front of the bus and will take 1/300,000 of a sec to reach the front of the bus.

The thing to keep in mind is that we are talking about the same light, just measured by different observers.

This fact leads to to a number of interesting things.

For instance: Let's put our light source in the middle of the bus and shine it in both directions. For anyone in the bus, the light takes an equal amount of time to reach the front and back of the Bus. If we put clocks at the front and back we can use this to synchronize the clocks (imagine each clock is designed to start running from 12:00 once it is hit by the light.).

But from the roadway, it works differently. The light traveling from midpoint to front chases the front of the bus, while the back of the bus rushes towards the light heading towards the back. The result is that the rearward light hits its clock before the forward light hits its clock. This means that the rear clock stats running before the front one does. Since each clock starts running from 12:00, The front clock, once it starts running will always run behind the rear clock. Thus for anyone in the the train, the clocks always read the same time, but for someone on the road, the rear clock runs ahead the front clock. This is known as the Relativity of Simultaneity.

As unnatural as this seems, this is the natural way of things. It only seems unnatural to us because we are used speeds that at very very small when compared to that of light. At these speeds, the difference in comparative clock readings between bus riders and roadway standers is so small it is all but immeasurable. Thus common experience misleads us to think that the idea of simultaneity is universal and is the same for the bus as it is for the road, even though it really isn't. This is usually the biggest stumbling block for people when they first try to understand Relativity; They continue to think in terms of absolute simultaneity and try to apply the idea of "at the same time" when it is just not applicable to the situation.

29. Originally Posted by Janus
Originally Posted by keeseguy
If we were in a bus traveling at c. I sitting in the back turn on my flash light, you would never see the beam, right?
Let's change this to a bus moving at 0.99c, since, as already point out in an earlier post, massive objects cannot travel at c.

For us, traveling in the bus, the light will travel at c relative to the bus. If the bus is 10 m long, it will take ~ 1/30,000,000 of a sec for the light to travel from back to front.

However, for someone standing on the road, this same light travels at c relative to the road. For him, the light has to "chase after" the front of the bus and will take 1/300,000 of a sec to reach the front of the bus.

The thing to keep in mind is that we are talking about the same light, just measured by different observers.

This fact leads to to a number of interesting things.

For instance: Let's put our light source in the middle of the bus and shine it in both directions. For anyone in the bus, the light takes an equal amount of time to reach the front and back of the Bus. If we put clocks at the front and back we can use this to synchronize the clocks (imagine each clock is designed to start running from 12:00 once it is hit by the light.).

But from the roadway, it works differently. The light traveling from midpoint to front chases the front of the bus, while the back of the bus rushes towards the light heading towards the back. The result is that the rearward light hits its clock before the forward light hits its clock. This means that the rear clock stats running before the front one does. Since each clock starts running from 12:00, The front clock, once it starts running will always run behind the rear clock. Thus for anyone in the the train, the clocks always read the same time, but for someone on the road, the rear clock runs ahead the front clock. This is known as the Relativity of Simultaneity.

As unnatural as this seems, this is the natural way of things. It only seems unnatural to us because we are used speeds that at very very small when compared to that of light. At these speeds, the difference in comparative clock readings between bus riders and roadway standers is so small it is all but immeasurable. Thus common experience misleads us to think that the idea of simultaneity is universal and is the same for the bus as it is for the road, even though it really isn't. This is usually the biggest stumbling block for people when they first try to understand Relativity; They continue to think in terms of absolute simultaneity and try to apply the idea of "at the same time" when it is just not applicable to the situation.
Thank you very much for enlightening my ignorance, I do try to pay attention.

30. So the doppler effect measure the change in frequency on a response? Ok so now it seems like there are two methods.

1) The one that sonar uses it measures the time it takes for response. I don't see why not use that for the same radar.

2) The doppler effect I guess I don't quite understand it fully.

31. Originally Posted by ScienceNoob
So the doppler effect measure the change in frequency on a response? Ok so now it seems like there are two methods.
As I brought up Doppler, I'll attempt to answer succinctly, pending correction by a "learned fellow"
1) The one that sonar uses it measures the time it takes for response. I don't see why not use that for the same radar.
The Doppler effect in sound results in a higher or lower pitch (wavelength)
For sound waves, see: Doppler effect - Wikipedia, the free encyclopedia
2) The doppler effect I guess I don't quite understand it fully.
The Doppler effect in light resilts in a red or or blue shift (wavelength)
For light, see: Relativistic Doppler effect - Wikipedia, the free encyclopedia

I would assume that the Doppler effect applies to any medium that propagates in wavelike manner.

I'm in deep water here, so I'll stop right now!

32. Originally Posted by ScienceNoob
1) The one that sonar uses it measures the time it takes for response. I don't see why not use that for the same radar.
Radar does use time to obtain range.
But Doppler radar uses the frequency shift to ascertain (relative) speed at the same time.

33. To revert to the title of the thread; "All motion is relative?", there is a well known case which casts doubt on the notion that all motion is relative. It has been referred to as "Newton's bucket" but it refers to any object which is spinning about an axis and which is subject to centripetal forces. A spinning body is acted upon by centripetal forces, which can be measured, whereas no such forces exist in the case of a body which isn't spinning. In the case of Newton's bucket, the bucket containing water which is spinning about a vertical axis through its centre could be recognised as rotating by the curved surface of the water it contains. It was argued by Newton that this appears to discriminate between rotational motion and absolute rotational rest. This view has been contested by others - most notably by Ernst Mach. But it is interesting that the argument about this has persisted for several centuries.

34. Is there a unit for this? You would need a "center" of the universe to do that I think.
Nope. And there isn't a centre of the universe.

No center to the universe? And how exactly do you know this?

35. Originally Posted by interesting
No center to the universe? And how exactly do you know this?
Because everything is moving away from everything else.
I.e. pick any point at all and everything is moving away from it. (At a speed proportional to the distance).
Pick some other point, as far away as you can.
Oops, everything is moving away from that one too. (With the same speed/ distance proportion).
How astronomers know that our galaxy is not centre of universe?

36. Originally Posted by Dywyddyr
Originally Posted by interesting
No center to the universe? And how exactly do you know this?
Because everything is moving away from everything else.
I.e. pick any point at all and everything is moving away from it. (At a speed proportional to the distance).
Pick some other point, as far away as you can.
Oops, everything is moving away from that one too. (With the same speed/ distance proportion).
How astronomers know that our galaxy is not centre of universe?
I didn't claim that OUR galaxy was the center of the universe. I was inferring that of course there is a center. Everything has a center.

If you are a particle on the outskirts of an explosion you will say that everything is moving away from everything else. You would be correct. If you then said your local 'galaxy' of particles is not the center of the explosion. You would be correct. If you then said 'everything is moving away from everything else, therefore there cannot be a center to the explosion'..you would be wrong.

37. Originally Posted by interesting
Originally Posted by Dywyddyr
Originally Posted by interesting
No center to the universe? And how exactly do you know this?
Because everything is moving away from everything else.
I.e. pick any point at all and everything is moving away from it. (At a speed proportional to the distance).
Pick some other point, as far away as you can.
Oops, everything is moving away from that one too. (With the same speed/ distance proportion).
How astronomers know that our galaxy is not centre of universe?
I didn't claim that OUR galaxy was the center of the universe. I was inferring that of course there is a center. Everything has a center.

If you are a particle on the outskirts of an explosion you will say that everything is moving away from everything else. You would be correct. If you then said your local 'galaxy' of particles is not the center of the explosion. You would be correct. If you then said 'everything is moving away from everything else, therefore there cannot be a center to the explosion'..you would be wrong.
A classical rookie mistake is to think that the big bang was an "explosion". It wasn't.

38. Originally Posted by xyzt
Originally Posted by interesting
Originally Posted by Dywyddyr
Originally Posted by interesting
No center to the universe? And how exactly do you know this?
Because everything is moving away from everything else.
I.e. pick any point at all and everything is moving away from it. (At a speed proportional to the distance).
Pick some other point, as far away as you can.
Oops, everything is moving away from that one too. (With the same speed/ distance proportion).
How astronomers know that our galaxy is not centre of universe?

I didn't claim that OUR galaxy was the center of the universe. I was inferring that of course there is a center. Everything has a center.

If you are a particle on the outskirts of an explosion you will say that everything is moving away from everything else. You would be correct. If you then said your local 'galaxy' of particles is not the center of the explosion. You would be correct. If you then said 'everything is moving away from everything else, therefore there cannot be a center to the explosion'..you would be wrong.
A classical rookie mistake is to think that the big bang was an "explosion". It wasn't.
Oh really?

And since you know exactly what happened during the Big Bang could you enlighten us in your own words? I don't need a link to a science article you read - do you believe everything you read and then regurgitate your new-found 'knowledge'?

39. Originally Posted by interesting
Originally Posted by xyzt
Originally Posted by interesting
Originally Posted by Dywyddyr
Originally Posted by interesting
No center to the universe? And how exactly do you know this?
Because everything is moving away from everything else.
I.e. pick any point at all and everything is moving away from it. (At a speed proportional to the distance).
Pick some other point, as far away as you can.
Oops, everything is moving away from that one too. (With the same speed/ distance proportion).
How astronomers know that our galaxy is not centre of universe?

I didn't claim that OUR galaxy was the center of the universe. I was inferring that of course there is a center. Everything has a center.

If you are a particle on the outskirts of an explosion you will say that everything is moving away from everything else. You would be correct. If you then said your local 'galaxy' of particles is not the center of the explosion. You would be correct. If you then said 'everything is moving away from everything else, therefore there cannot be a center to the explosion'..you would be wrong.
A classical rookie mistake is to think that the big bang was an "explosion". It wasn't.
Oh really?

And since you know exactly what happened during the Big Bang could you enlighten us in your own words? I don't need a link to a science article you read - do you believe everything you read and then regurgitate your new-found 'knowledge'?
I do not engage crackpots.

40. Originally Posted by xyzt
Originally Posted by interesting
Originally Posted by xyzt
Originally Posted by interesting
Originally Posted by Dywyddyr
Originally Posted by interesting
No center to the universe? And how exactly do you know this?
Because everything is moving away from everything else.
I.e. pick any point at all and everything is moving away from it. (At a speed proportional to the distance).
Pick some other point, as far away as you can.
Oops, everything is moving away from that one too. (With the same speed/ distance proportion).
How astronomers know that our galaxy is not centre of universe?

I didn't claim that OUR galaxy was the center of the universe. I was inferring that of course there is a center. Everything has a center.

If you are a particle on the outskirts of an explosion you will say that everything is moving away from everything else. You would be correct. If you then said your local 'galaxy' of particles is not the center of the explosion. You would be correct. If you then said 'everything is moving away from everything else, therefore there cannot be a center to the explosion'..you would be wrong.
A classical rookie mistake is to think that the big bang was an "explosion". It wasn't.
Oh really?

And since you know exactly what happened during the Big Bang could you enlighten us in your own words? I don't need a link to a science article you read - do you believe everything you read and then regurgitate your new-found 'knowledge'?
I do not engage crackpots.
Awesome. Haha.

I do not engage with people who recycle information and have nothing to stand on. Are you 12 years old and can't handle a rational discussion?

41. Originally Posted by interesting
Originally Posted by xyzt
Originally Posted by interesting
Originally Posted by xyzt
Originally Posted by interesting
Originally Posted by Dywyddyr
Originally Posted by interesting
No center to the universe? And how exactly do you know this?
Because everything is moving away from everything else.
I.e. pick any point at all and everything is moving away from it. (At a speed proportional to the distance).
Pick some other point, as far away as you can.
Oops, everything is moving away from that one too. (With the same speed/ distance proportion).
How astronomers know that our galaxy is not centre of universe?

I didn't claim that OUR galaxy was the center of the universe. I was inferring that of course there is a center. Everything has a center.

If you are a particle on the outskirts of an explosion you will say that everything is moving away from everything else. You would be correct. If you then said your local 'galaxy' of particles is not the center of the explosion. You would be correct. If you then said 'everything is moving away from everything else, therefore there cannot be a center to the explosion'..you would be wrong.
A classical rookie mistake is to think that the big bang was an "explosion". It wasn't.
Oh really?

And since you know exactly what happened during the Big Bang could you enlighten us in your own words? I don't need a link to a science article you read - do you believe everything you read and then regurgitate your new-found 'knowledge'?
I do not engage crackpots.
Awesome. Haha.

I do not engage with people who recycle information and have nothing to stand on. Are you 12 years old and can't handle a rational discussion?
The point is that your posts are not "rational". They are ignorant.

42. Originally Posted by xyzt
Originally Posted by interesting
Originally Posted by xyzt
Originally Posted by interesting
Originally Posted by xyzt
Originally Posted by interesting
Originally Posted by Dywyddyr
Originally Posted by interesting
No center to the universe? And how exactly do you know this?
Because everything is moving away from everything else.
I.e. pick any point at all and everything is moving away from it. (At a speed proportional to the distance).
Pick some other point, as far away as you can.
Oops, everything is moving away from that one too. (With the same speed/ distance proportion).
How astronomers know that our galaxy is not centre of universe?

I didn't claim that OUR galaxy was the center of the universe. I was inferring that of course there is a center. Everything has a center.

If you are a particle on the outskirts of an explosion you will say that everything is moving away from everything else. You would be correct. If you then said your local 'galaxy' of particles is not the center of the explosion. You would be correct. If you then said 'everything is moving away from everything else, therefore there cannot be a center to the explosion'..you would be wrong.
A classical rookie mistake is to think that the big bang was an "explosion". It wasn't.
Oh really?

And since you know exactly what happened during the Big Bang could you enlighten us in your own words? I don't need a link to a science article you read - do you believe everything you read and then regurgitate your new-found 'knowledge'?
I do not engage crackpots.
Awesome. Haha.

I do not engage with people who recycle information and have nothing to stand on. Are you 12 years old and can't handle a rational discussion?
The point is that your posts are not "rational". They are ignorant.
Nice 12 year old comeback.

The moment I wrote to explain in 'your own words' was the moment it became too much for you to engage in a discussion.

Any adults here interested in backing up their claims?

43. Everything has a center.
Where's the centre of the surface of a sphere ?

44. Originally Posted by interesting
Originally Posted by xyzt
Originally Posted by interesting
Originally Posted by xyzt
Originally Posted by interesting
Originally Posted by xyzt
Originally Posted by interesting
Originally Posted by Dywyddyr
Originally Posted by interesting
No center to the universe? And how exactly do you know this?
Because everything is moving away from everything else.
I.e. pick any point at all and everything is moving away from it. (At a speed proportional to the distance).
Pick some other point, as far away as you can.
Oops, everything is moving away from that one too. (With the same speed/ distance proportion).
How astronomers know that our galaxy is not centre of universe?

I didn't claim that OUR galaxy was the center of the universe. I was inferring that of course there is a center. Everything has a center.

If you are a particle on the outskirts of an explosion you will say that everything is moving away from everything else. You would be correct. If you then said your local 'galaxy' of particles is not the center of the explosion. You would be correct. If you then said 'everything is moving away from everything else, therefore there cannot be a center to the explosion'..you would be wrong.
A classical rookie mistake is to think that the big bang was an "explosion". It wasn't.
Oh really?

And since you know exactly what happened during the Big Bang could you enlighten us in your own words? I don't need a link to a science article you read - do you believe everything you read and then regurgitate your new-found 'knowledge'?
I do not engage crackpots.
Awesome. Haha.

I do not engage with people who recycle information and have nothing to stand on. Are you 12 years old and can't handle a rational discussion?
The point is that your posts are not "rational". They are ignorant.
Nice 12 year old comeback.

The moment I wrote to explain in 'your own words' was the moment it became too much for you to engage in a discussion.

Any adults here interested in backing up their claims?
It was you who asserted that the Big Bang wasn't an explosion: "Oh really?" and then dismissed that knowledge learned a priori is somehow based upon blind speculation.

45. Originally Posted by interesting
I didn't claim that OUR galaxy was the center of the universe.
The article explains why the claim doesn't just apply to our galaxy.

I was inferring that of course there is a center. Everything has a center.
Not even in our everyday experience. Where's the centre of the surface of the Earth?

If you are a particle on the outskirts of an explosion you will say that everything is moving away from everything else.
Er, apart from the co-moving particles you mean?

You would be correct. If you then said 'everything is moving away from everything else, therefore there cannot be a center to the explosion'..you would be wrong.
Keep trying...

46. Originally Posted by Dywyddyr
Not even in our everyday experience. Where's the centre of the surface of the Earth?
Good point. I'm standing on it.

47. Originally Posted by Markus Hanke
Everything has a center.
Where's the centre of the surface of a sphere ?
I don't think there is a center of the surface of a sphere. I do think there is a center to the sphere itself

48. Originally Posted by interesting
Everything has a center.
Originally Posted by interesting
I don't think there is a center of the surface of a sphere.
So you were wrong then?

49. Now to get back at the original question. If timespace is really a continuum and lightspeed is really a constant (why light speed only and not all RF energy waves?) - then, if the space changes, must not the space-time continuum change? Also, doesn't light energy when reaching far fields, diminish at the inverse of the square of the distance? To my current way of thinking, all RF energies including light may travel at a certain defined speed in space, but not always in straight lines so while the speed may remain constant, the distance may vary. It isn't like light or RF energy of other frequencies can travel in space in no time at all. At least in the constant restrained speed of light theory.

This whips up some ideas in my mind, because there are likely areas in space where light cannot reach.

50. Originally Posted by interesting
Originally Posted by Markus Hanke
Everything has a center.
Where's the centre of the surface of a sphere ?
I don't think there is a center of the surface of a sphere. I do think there is a center to the sphere itself
The universe is not a sphere.

51. Originally Posted by xyzt
Originally Posted by interesting
Originally Posted by Markus Hanke
Everything has a center.
Where's the centre of the surface of a sphere ?
I don't think there is a center of the surface of a sphere. I do think there is a center to the sphere itself
The universe is not a sphere.
How do you know that, and what shape is it then? Also where does the idea that all things have a center come from? A center has to be relative to a circumference, no? How can a circumference have a center without being around something?

52. Originally Posted by Mayflow
If timespace is really a continuum and lightspeed is really a constant (why light speed only and not all RF energy waves?) -.
I find it mind-boggling that you are so uneducated. The correct word is "ignorant" by the way.

Of course all EMR travels at speed c in a vacuum. From large wavelength radio waves all the way up the EMR spectrum to short wavelength gamma waves. (high school is where I learned this.)

You brag all the time about how smart you are and your engineering background. You are, in reality, an uneducated fool. It's no wonder you've been suspended 3 or 4 times now. You deserve it. I think you might be stupid, on top of your ignorance -- not sure about that but it seems a good bet. I don't think you went to any school and just picked up a few bits of info on the web. Why don't you go back to that woo website of yours. There you can play smart with the other morons.

53. Originally Posted by Mayflow
Also where does the idea that all things have a center come from?
Why ask xyzt, it wasn't his claim.

A center has to be relative to a circumference, no?
Uh what?
You do know what circumference means, don't you?

How can a circumference have a center without being around something?
A circumference doesn't have a centre.

54. Originally Posted by Chucknorium
Originally Posted by Mayflow
If timespace is really a continuum and lightspeed is really a constant (why light speed only and not all RF energy waves?) -.
I find it mind-boggling that you are so uneducated. The correct word is "ignorant" by the way.

Of course all EMR travels at speed c in a vacuum. From large wavelength radio waves all the way up the EMR spectrum to short wavelength gamma waves. (high school is where I learned this.)

You brag all the time about how smart you are and your engineering background. You are, in reality, an uneducated fool. It's no wonder you've been suspended 3 or 4 times now. You deserve it. I think you might be stupid, on top of your ignorance -- not sure about that but it seems a good bet. I don't think you went to any school and just picked up a few bits of info on the web. Why don't you go back to that woo website of yours. There you can play smart with the other morons.
Just quoted to show your supreme intelligence for all to see.

55. Originally Posted by Dywyddyr
Originally Posted by Mayflow
Also where does the idea that all things have a center come from?
Why ask xyzt, it wasn't his claim.

A center has to be relative to a circumference, no?
Uh what?
You do know what circumference means, don't you?

How can a circumference have a center without being around something?
A circumference doesn't have a centre.

Can you follow a simple conversation?

56. Originally Posted by Mayflow
Can you follow a simple conversation?
Yes he can. And he's quite good at it. You're the one who can't.

Where did you go to school? You should sue that school because you learned nothing.

It's a shame that you are allowed to post here on this science forum, because your posts are (always) non-scientific and you do a disservice to all those trying to learn real science.

57. Anyone care to discuss the subject?

58. Originally Posted by Dywyddyr
Originally Posted by interesting
Everything has a center.
Originally Posted by interesting
I don't think there is a center of the surface of a sphere.
So you were wrong then?
No. The object is a sphere. It has a center. You picked a piece of the object and asked for its center.

59. Originally Posted by Dywyddyr
Originally Posted by Mayflow
Also where does the idea that all things have a center come from?
Why ask xyzt, it wasn't his claim.

A center has to be relative to a circumference, no?
Uh what?
You do know what circumference means, don't you?

How can a circumference have a center without being around something?
A circumference doesn't have a centre.
A circumference does not have a center?

60. Originally Posted by interesting
Originally Posted by Dywyddyr
Originally Posted by interesting
Everything has a center.
Originally Posted by interesting
I don't think there is a center of the surface of a sphere.
So you were wrong then?
No. The object is a sphere. It has a center. You picked a piece of the object and asked for its center.
He seems to not think that circumferences have centers, but maybe that circumferences have centers?

It is maybe some kind of new Geometry that he and Chucknorium created.

61. [QUOTE=Dywyddyr;580735]
Originally Posted by Mayflow
Also where does the idea that all things have a center come from?
Why ask xyzt, it wasn't his claim.

Heck I just hit the quote button. You are very pedantic and I would say to a fault. Has the right side of your brain's hemisphere been impaired? Now let me lead you through this. Chucknorium aside, because I find no worth in his posts as of this point in time, Interesting was talking about a sphere in shape, but it could have been any sort of circumference, so referred to a center of anything. He/she was not the one who talked somehow about the center of a circumference - actually I think that was you.

62. Originally Posted by Mayflow
Originally Posted by interesting
Originally Posted by Dywyddyr
Originally Posted by interesting
Everything has a center.
Originally Posted by interesting
I don't think there is a center of the surface of a sphere.
So you were wrong then?
No. The object is a sphere. It has a center. You picked a piece of the object and asked for its center.
He seems to not think that circumferences have centers, but maybe that circumferences have centers?

It is maybe some kind of new Geometry that he and Chucknorium created.
Is the circumference of sphere or the surface of a sphere an object? If it doesn't have a center maybe it is not an object. A thing being an object.

63. Originally Posted by interesting
No. The object is a sphere. It has a center. You picked a piece of the object and asked for its center.
Nope.
What's under discussion is the surface of the sphere.

Originally Posted by Mayflow
A circumference does not have a center?
No.

Originally Posted by Mayflow
You are very pedantic and I would say to a fault.
And you appear to rely on sloppy terminology, possibly in order to mask your ignorance.

Has the right side of your brain's hemisphere been impaired?
Have you been subscribing to myths again?

Interesting was talking about a sphere in shape, but it could have been any sort of circumference, so referred to a center of anything. He/she was not the one who talked somehow about the center of a circumference - actually I think that was you.
Then I suggest you try reading the thread (or at least the relevant posts) again.
Interesting: Everything has a center. (No mention of a sphere until later).

64. Originally Posted by Robittybob1
Originally Posted by Mayflow
Originally Posted by interesting
Originally Posted by Dywyddyr
Originally Posted by interesting
Everything has a center.
Originally Posted by interesting
I don't think there is a center of the surface of a sphere.
So you were wrong then?
No. The object is a sphere. It has a center. You picked a piece of the object and asked for its center.
He seems to not think that circumferences have centers, but maybe that circumferences have centers?

It is maybe some kind of new Geometry that he and Chucknorium created.
Is the circumference of sphere or the surface of a sphere an object? If it doesn't have a center maybe it is not an object. A thing being an object.
I didn't follow that, but if some object is a part of a circumference, may not it itself be a circumference with a center?

65. Originally Posted by Mayflow
I didn't follow that, but if some object is a part of a circumference, may not it itself be a circumference with a center?
What?
Where exactly is the centre of a circumference?

66. Originally Posted by Dywyddyr
Originally Posted by Mayflow
I didn't follow that, but if some object is a part of a circumference, may not it itself be a circumference with a center?
What?
Where exactly is the centre of a circumference?
Most definitely at the center.

67. Originally Posted by Dywyddyr
Originally Posted by Mayflow
I didn't follow that, but if some object is a part of a circumference, may not it itself be a circumference with a center?
What?
Where exactly is the centre of a circumference?
I said (follow?) if something is part of a circumference, it may have itself a center. Think at the quantum level.

68. Originally Posted by Mayflow
I said (follow?) if something is part of a circumference, it may have itself a center. Think at the quantum level.
What you wrote (apart the specious bollocks), was "may not it itself be a circumference with a center?"
I'll ask again: Where, exactly, is the centre of a circumference?
(And your introduction of "quantum" is precisely on a par with Deepak Chopra's [mis]use of the word).

69. [QUOTE=Dywyddyr;580758]
Originally Posted by Mayflow
I said (follow?) if something is part of a circumference, it may have itself a center. Think at the quantum level.
What you wrote (apart the specious bollocks), "

Did you like have a deprived childhood or something?

70. Originally Posted by Mayflow
Did you like have a deprived childhood or something?
No.
I had an education. You should try it sometime.
I'll ask again: Where, exactly, is the centre of a circumference?

71. Once again, and I don't expect you to get it, any point on a circumference can be it's own circumference, and have its own center which will itself be a circumference with its own center. The day that we believed that the atom is the smallest particle ever is long past.

72. Hi all - interesting thread. Brings to mind something I read years ago that remained unresolved in my mind concerning relative motion. I'm going to try to find it so as to complete my understanding here, but from what I recall (dimly) at the moment, I have this question.

A laser, pointing vertically, is travelling horizontally, at, say, 1/10th c. It shoots a laser beam towards th ceiling. Do those individual photons, upon leaving the laser gun, travel in a vertical direction ?

IOW, if at a particular instant, the laser gun was pointing at point X on the ceiling, will the photon emmitted at that instant hit point X, or will it hit the ceiling a little further along, in the line of travel of the laser gun ?

Thanks.

73. Originally Posted by Mayflow
Think at the quantum level.
You can't think properly in a Newtonian universe. You should forget about understanding quantum-level science or relativity. Both are way beyond your intellect.

74. Originally Posted by Mayflow
Once again, and I don't expect you to get it
Why would ANYONE "get it"? All you've done is make the claim while failing, consistently, to provide any support.

any point on a circumference can be it's own circumference
ONLY if you completely redefine the word "circumference".
(In other words: No, you're wrong).

and have its own center which will itself be a circumference with its own center.
In other words your "proof" that a circumference has a centre is to claim any point on that circumference is also (somehow) a circumference and that (without any explanation of support at all) that particular "circumference" has a centre.

The day that we believed that the atom is the smallest particle ever is long past.
Entirely irrelevant.

75. Originally Posted by Mayflow
any point on a circumference can be it's own circumference, and have its own center which will itself be a circumference with its own center. .
That is the type of nonsensical statement that would probably amaze your group of idiots over there on your woo website. Here it is just laughable.

76. Originally Posted by Chucknorium
Originally Posted by Mayflow
Think at the quantum level.
You can't think properly in a Newtonian universe. You should forget about understanding quantum-level science or relativity. Both are way beyond your intellect.
Quoted again for your vast intellect.

77. Originally Posted by Dywyddyr
Originally Posted by Mayflow
Once again, and I don't expect you to get it
Why would ANYONE "get it"? All you've done is make the claim while failing, consistently, to provide any support.

any point on a circumference can be it's own circumference
ONLY if you completely redefine the word "circumference".
(In other words: No, you're wrong).

and have its own center which will itself be a circumference with its own center.
In other words your "proof" that a circumference has a centre is to claim any point on that circumference is also (somehow) a circumference and that (without any explanation of support at all) that particular "circumference" has a centre.
So, according to you, any point on a circumference cannot have its own circumference and center? The neutrinos and baryons are going to be pissed now.

78. Originally Posted by Mayflow
So, according to you, any point on a circumference cannot have its own circumference and center? The neutrinos and baryons are going to be pissed now.
Like I said, you're introducing specious "features".
ANY point on a circumference can be taken (excluding the annoying facts that [1] a circumference is 2D "construct" and therefore won't have either neutrinos or baryons, and [2] neither neutrinos nor baryons are circumferences as you claimed).
We now consider the "centre" of that point to be the "centre of the circumference" (while completely ignoring the sheer ridiculousness of that concept).
Thus, ANY point can be considered the centre.
Ergo a circumference doesn't have A centre and any point on that circumference is indistinguishable from any other point.

A circumference doesn't have a centre: QED

79. So, a circumference does not have a center? Does a center have a circumference then?

80. Originally Posted by Chucknorium
Originally Posted by Mayflow
Think at the quantum level.
You can't think properly in a Newtonian universe. You should forget about understanding quantum-level science or relativity. Both are way beyond your intellect.
Isaac Newton invented the universe? Or is it Fig Newton? If it is fig Newtonian then why isn't everyone fat?

81. Originally Posted by Mayflow
So, a circumference does not have a center?
Which part of "a circumference doesn't have A centre" didn't you understand?

Does a center have a circumference then?
Not always.

82. Originally Posted by Dywyddyr
Originally Posted by Mayflow
So, a circumference does not have a center?
Which part of "a circumference doesn't have A centre" didn't you understand?

Does a center have a circumference then?
Not always.
Mostly the part that a circumference does not have a center, and the part that a center does not have a circumference.

83. Originally Posted by Mayflow
Mostly the part that a circumference does not have a center
In other words you can't follow a simple chain of logic, even when it's laid for you.

and the part that a center does not have a circumference.
And you haven't bothered to look the definition of circumference, despite me providing you with a link.
Here's an illustration of three shapes with their centres marked.

Please note that only ONE of the three has a circumference.

84. Originally Posted by Dywyddyr
Originally Posted by Mayflow
Mostly the part that a circumference does not have a center
In other words you can't follow a simple chain of logic, even when it's laid for you.

and the part that a center does not have a circumference.
And you haven't bothered to look the definition of circumference, despite me providing you with a link.
Here's an illustration of three shapes with their centres marked.

Please note that only ONE of the three has a circumference.
The other two shapes have perimeters. A circumference is a special case of perimeter. Every point on the perimeter can become the center as it is always equidistance one way or the other.

85. Mayflow see you next month.

You've been continuously warned to stay from the hard science parts of the forum because you seem to lack the ability to contribute in any meaningful way....or as in this case....take what could be an interesting subjects about relative speeds and turned it into a review of 10th grade geometry. This will be your last chance.

Robert you are also warned to stay out this subforum for much the same reasons.

86. Oh good greif. I can use the words perimeter and center of mass as well, but how do you figure the shape of the perimeter matters?

87. Originally Posted by Robittybob1
The other two shapes have perimeters. A circumference is a special case of perimeter.
A perimeter is not necessarily a circumference.
Non-circular shapes do not have a circumference (and circumference is what's been under discussion).

Every point on the perimeter can become the center
In other words there is no centre, since any point is indistinguishable from every other.

88. Originally Posted by Mayflow
Originally Posted by interesting
Originally Posted by Dywyddyr
Originally Posted by interesting
Everything has a center.
Originally Posted by interesting
I don't think there is a center of the surface of a sphere.
So you were wrong then?
No. The object is a sphere. It has a center. You picked a piece of the object and asked for its center.
He seems to not think that circumferences have centers, but maybe that circumferences have centers?

It is maybe some kind of new Geometry that he and Chucknorium created.
Mayflow -- you are breathtakingly ignorant about math, science and logic. That unfortunately abets your arrogant belief that you know what you're talking about.

To mathematicians and geometers, a circumference is a length (look it up; you didn't pay attention in school, apparently). Insisting that there must be a center of a length is fully as nonsensical as your assertion that "voltage is nonlinear, but power is linear." Or some similar bollocks.

Circles have centers.

Squares have centers.

Circumferences do not have centers. If you continue to insist otherwise, you will have to show us the center of "1.342 inches" (hint: it's not 0.671 inches -- I'm not asking for the center of a piece of string of 1.342-inch length).

Colloquially, a circumference can refer to the boundary that defines a circle. But that boundary has no unique center, so one cannot speak of the center of a circumference, even when using the term colloquially.

Based on statistics of your posts here, when you are told you are wrong about math, science or logic, you should assume that you are wrong because you have almost always been wrong. So stop posting rude, ignorant and nonsensical rebuttals.

89. Originally Posted by tk421
Based on statistics of your posts here, when you are told you are wrong about math, science or logic, you should assume that you are wrong because you have almost always been wrong. So stop posting rude, ignorant and nonsensical rebuttals.
She is incorrigible. The shame about her posting is that some new member, who is ignorant in science, will read her posts and make the wrong determination that she knows what she is talking about -- which she doesn't.

She should stick to her poems, which are god-awful, but at least they aren't harmful. Well, maybe they could be used as torture . . . for she could be the fourth worst poet in the universe, right behind the Vogons.

90. She's just a troll. I would normally be of the opinion bullshit should be challenged but in this case I think the more people who ignore her the better. The crap she posts is so obviously crap that anyone who finished high school can see through it (the whininess and childishness are big clues, even to a noob, that she doesn't have a clue). Trying to put her right just leads to a train wreck of a thread derail, like here. Don't feed the troll...

91. Originally Posted by interesting
I don't think there is a center of the surface of a sphere. I do think there is a center to the sphere itself
Yes, that is exactly correct. Keeping this in mind, the 4-dimensional pseudo-Riemannian manifold which we use to model the universe has a topology that is similar to the surface of a sphere, not the sphere itself; it is singly connected, has no boundary, is either finite or infinite, has a genus of zero, and is time-orientable. Elementary topology tells us that such manifolds cannot have a centre point, just as the surface of a sphere cannot have a centre point.

No. The object is a sphere. It has a center. You picked a piece of the object and asked for its center.
We currently use a FLRW manifold to model the universe; such manifolds are closed, i.e. they are globally compact and without boundary. As such, their topology cannot be that of a 4-sphere. Having said that, there are certain manifolds the spatial (!) part which are quotient spaces of S(3), such as the Poincare dodecahedral space. These will yield a spherical geometry in the spatial part only - however, the universe itself is of course (3+1) dimensional, so once the spatial slices are foliated along the time direction, you once again end up with a topology that does not permit any centre point, as explained above.

To make a long story short - none of the models we use in modern physics to describe the universe as a whole is compatible with the notion of a "centre point". The BB event was not an "explosion" in the sense that everything moves outward from a fixed centre point, but it was the start of metric expansion on a manifold, whereby all points move away from all other points, and no single point is physically privileged in any way.

92. Originally Posted by PhDemon
She's just a troll.
That begs the question : why does management allow it to post here? It gets suspended, what, four times now, and it is allowed to come back and post more crap????

93. Beats me, they have been very patient...

94. Maybe the driving force is to keep as many members as possible and keep the daily post count up. After all, when that mayflow troll posts, it causes a flurry of posting by other members, even mostly dormant ones like me.

95. Originally Posted by Chucknorium
Maybe the driving force is to keep as many members as possible and keep the daily post count up. After all, when that mayflow troll posts, it causes a flurry of posting by other members, even mostly dormant ones like me.
Definitely. Besides, she's not the worst offender. There are many more worse than her.

96. Getting back to our regular programme,

Originally Posted by ScienceNoob
Is there any number for a "true" speed.
As others have pointed out, there's no such thing as a "true" velocity for a massive object (and it will be c for a massless object). Velocity is relative. Galileo figured this out 4 centuries ago. If you are inside an aeroplane traveling at a steady velocity, you cannot tell what that velocity is.

Everyone knows that even if you are standing still on earth you are flying around in orbit of the sun at Xm/s. This galaxy is also moving faster and faster according to what I have read about expanding universe.

So how would you measure the speed of earth itself total, not in reference to the sun, not in reference to the galaxy?
As in the aeroplane example, you cannot determine the "total speed" of the earth, as there is no such thing.

Is there a unit for this? You would need a "center" of the universe to do that I think.
You may designate any point as the reference point for computing a velocity. You don't need a "center." Any point will do. You just need to specify what that point is for others to know what you are talking about. "1000km/s" by itself is meaningless. "1000km/s relative to Greenwich" tells the listener enough to figure it out.

Also, once you guys help me answer that I have a secondary question to further that first one. So lets say we are moving at "true" 1,000M/s if I turn on a flashlight then wouldn't the light be travelling 1,000M/s + c thus breaking the laws of physics?
Again as others have pointed out, speeds do not add directly. At speeds much less than c, they do to a good approximation, but the key word is approximation. As with all approximations, one must be aware of the domains of applicability of this one. If you attempt to use an approximation where it is not valid, you will get an invalid answer.

There is a quantity that you may find useful. It's called rapidity, and it does add linearly (for this one-dimensional case). See Rapidity - Wikipedia, the free encyclopedia. Then, once you've done the addition, you convert back into ordinary speed.

Rapidity properly takes relativity into account. No speed ever exceeds c. "It's not just a good idea, it's the law."

If not, then in the future if everything keeps expanding and moving faster wouldn't ever piece of matter be moving at the speed of light? Meaning no matter could move in the direction they are "expanding" at as it would be going over the speed of light.
Recession velocities can (and do, for sufficiently distant objects) exceed light. That's because space expands. This is not a violation of relativity -- indeed, it is a consequence of (general) relativity.

97. Originally Posted by marcbo
Hi all - interesting thread. Brings to mind something I read years ago that remained unresolved in my mind concerning relative motion. I'm going to try to find it so as to complete my understanding here, but from what I recall (dimly) at the moment, I have this question.

A laser, pointing vertically, is travelling horizontally, at, say, 1/10th c. It shoots a laser beam towards th ceiling. Do those individual photons, upon leaving the laser gun, travel in a vertical direction ?

IOW, if at a particular instant, the laser gun was pointing at point X on the ceiling, will the photon emmitted at that instant hit point X, or will it hit the ceiling a little further along, in the line of travel of the laser gun ?

Thanks.
Getting back to our regular programme .. indeed !

So can someone answer the above for me ?

Heh .. preferably Janus as he has a knack for 'splaining things in a manner I can understand, and without the needless antagonism and bickering .. Thanks !

98. Originally Posted by marcbo
Hi all - interesting thread. Brings to mind something I read years ago that remained unresolved in my mind concerning relative motion. I'm going to try to find it so as to complete my understanding here, but from what I recall (dimly) at the moment, I have this question.

A laser, pointing vertically, is travelling horizontally, at, say, 1/10th c. It shoots a laser beam towards th ceiling. Do those individual photons, upon leaving the laser gun, travel in a vertical direction ?
In the vehicle hosting the laser, the beam travels vertically. With respect to the ground, the beam is aberrated (inclined) forward.

IOW, if at a particular instant, the laser gun was pointing at point X on the ceiling, will the photon emmitted at that instant hit point X, or will it hit the ceiling a little further along, in the line of travel of the laser gun ?

Thanks.

In all frames, the beam hits the same point. If it didn't, you would have an experiment that could determine the state of uniform motion of a lab from INSIDE the respective lab. This contradicts the principle of relativity.

99. xyzt, in another thread a while back, you accused me of making up BS.

I was quite surprised and dissapointed at that, because it was totally false and there was no need for it. I don't feel you are the person I can have a condusive dialogue with concerning certain queries I have.

So thanks for the response, however, I know that bad starts really ever only lead to bickering and waste of time, so I will put you on ignore.

I will make no further response to you at all on any matter, and respectfully request you refrain from answering my queries and responding to my posts.

100. Hi Janus - if it's not too much trouble, can you please look at my post #71 and let me have a response, particulalry the main point, which is ..

A laser, pointing vertically, is travelling horizontally, at, say, 1/10th c. It shoots a laser beam towards th ceiling. Do those individual photons, upon leaving the laser gun, travel in a vertical direction ?

101. Originally Posted by marcbo
Hi Janus - if it's not too much trouble, can you please look at my post #71 and let me have a response, particulalry the main point, which is ..

A laser, pointing vertically, is travelling horizontally, at, say, 1/10th c. It shoots a laser beam towards th ceiling. Do those individual photons, upon leaving the laser gun, travel in a vertical direction ?
No, in your example the beam would travel diagonally to any observer in the same frame of reference. That creates some interesting results.
a) even as the diagonal light beam is longer than the straight vertical beam, it arrives at the ceiling in the same time as if the laser was stationary.

OK I see my error. The question is not what an observer would see, but if the photons vertical path is altered by the movement of the laser gun.

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