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Author Topic: Is Relativity Wrong?  (Read 17080 times)

Offline Rincewind

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Is Relativity Wrong?
« on: 01/10/2005 15:23:15 »
I think the generally accepted interpretation of relativity says that when you go faster your time slows down.  So, for example, the astronauts who went to the moon and back are slightly younger than other peeps who were born at the same time but stayed on Earth.

I was thinking, if a ship and some light left a planet then the ship came back, having aged less than the people on the planet, wouldn't the distance the light had travelled have to be different as well?  Either that or it would have to have travelled at a different velocity for those on the planet and those on the ship, right?

Am I making some kind of basic error here?


 

Offline ukmicky

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Re: Is Relativity Wrong?
« Reply #1 on: 01/10/2005 16:02:51 »
Hi andrew and welcome to the forum      (good choice):)

I was going to anwser your question but i tend to make basic errors also, so instead of trying.

If you wait a little while one of the many clever people on this forum will get back to you.

Or If you google time dialation and Relativistic Length Contraction you should also get an explanation. :)

A couple of links given basic explanations


http://en.wikipedia.org/wiki/Length_contraction
http://www.glenbrook.k12.il.us/gbssci/phys/mmedia/specrel/lc.html
http://www.glenbrook.k12.il.us/gbssci/phys/Class/relativity/U7l4e.html

Michael                                      
« Last Edit: 01/10/2005 16:38:45 by ukmicky »
 

Offline Rincewind

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Re: Is Relativity Wrong?
« Reply #2 on: 01/10/2005 17:56:48 »
Hello Micheal, nice to meet you:)

I like your comment about 'clever people':D

About length dilation...

...if the spaceship and the people who stayed end up on the planet at the same time and they could agree on how far away the light was, but not on how much time had passed, surely that means they wouldn't agree on a velocity?

Or does the light travel a different distance across space for each PoV but somehow end up in the same place?
 

Offline Solvay_1927

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Re: Is Relativity Wrong?
« Reply #3 on: 02/10/2005 01:37:37 »
Rince/Andrew,
welcome to the best science forum on the net.

I'm not sure I understand your question.

Correction - I AM sure - I DON'T understand your question.

Could you give a more precise example? (e.g. who leaves what location when, where do they go, when do they return, where does the light beam go, etc.)

If you can make the example more specific, maybe I can give you an answer.

(And after that, maybe someone else can come along and give you a CORRECT answer.) :)


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Offline Rincewind

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Re: Is Relativity Wrong?
« Reply #4 on: 02/10/2005 19:55:04 »
Okay, just answer this first and I'll decide if the rest of my question is worth answering:

Did the astronauts who went to the moon age less during their voyage than people who stayed behind on Earth, even if by a tiny amount.

(According to the theory of relativity)

Cos if they did... well, we'll get to that if they did.
 

Offline ukmicky

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Re: Is Relativity Wrong?
« Reply #5 on: 03/10/2005 00:15:48 »
Cheers mate Thats any easy one,I'm good at the easy one's.;)

Yes they did age less in respect to the people they left behind on earth, but it was probably no more than seconds as the speed that their ship was travelling wasn't very fast in relativity terms.

Time is only RELATIVE to the observer.(RELATIVITY)

Different observers can observe  time differently to each other.
If you were on earth and you could magically with no time delay see a clock in a fast moving spaceship, the faster the better,you would see their clock running slower than yours on earth:)

RELATIVITY CALCULATER LINK BELOW
http://www32.brinkster.com/snefru/space/srcalc/srcalc.htm

Michael                                      
« Last Edit: 03/10/2005 00:31:29 by ukmicky »
 

Offline Solvay_1927

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Re: Is Relativity Wrong?
« Reply #6 on: 03/10/2005 01:29:27 »
Yeah, ukmicky's right.

So ... what about the rest of your question, rincewind?

Solvay.


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Offline Rincewind

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Re: Is Relativity Wrong?
« Reply #7 on: 04/10/2005 00:12:22 »
So if a beam of light left earth at the same time as them, and they went to the moon and back, they would then be able to agree with the folks who had stayed on earth about how far away the light was right?  
The light is a certain distance, at this point, from the planet Earth, yeah?
So if they can agree on how far away the light is, but not how much time has passed, how can they agree on a speed of light (which is always constant.  That's like a fundamental thingummy of relativity)?
 

Offline Rincewind

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Re: Is Relativity Wrong?
« Reply #8 on: 04/10/2005 00:15:43 »
I mean, if they were going away from me, then I can understand their clocks going slower, but if they were coming towards me wouldn't their clocks go faster and catch up again?  Logically speaking.

I know the equations call for the squares of velocities to be used which makes it (apparently) a scalar quantity and therefore independant of direction.  But I'm not sure the maths hooks up with common sense on this one.
 

Offline ukmicky

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Re: Is Relativity Wrong?
« Reply #9 on: 04/10/2005 01:43:31 »
Explanations are now getting harder. Let’s see how well I do

Their are two frames of reference here the first one is yours and the earths which as far a you and the earth is concerned remains constant,(no time dilation) and the second one is the spaceship that is speeding through space, and is now experiencing time dilation.
Time dilation slows down time for the observer experiencing it compared to there original frame of reference, which in this case is Earth

Your frame of reference won't change, its there frame of reference on the ship that is changing, they are the ones that have left you and the earth frame of reference and therefore it is them that is experiencing the effects of relativity.

For their time on the space ship to catch up with your time on earth,you and the earth would have to experience time dilation which you can't because the earths speed of travel through space remains constant.

Hmmm. It’s a bit long winded. Where’s my mistake, there’s got to be one coz it’s me.:)

have I gone wrong anywhere. or missed anything.

ps i quite enjoy trying to learn all this stuff. So be kind:D


Michael                                      
« Last Edit: 04/10/2005 04:24:45 by ukmicky »
 

Offline Solvay_1927

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Re: Is Relativity Wrong?
« Reply #10 on: 04/10/2005 22:44:43 »
Andrew - I understand your question now, and it's a good one.  In fact, it's quite tough.

Michael's answer is absolutely right (as far as I can tell - although I'm no expert), but I'm not sure it really addresses the specific point in your question (i.e. just how far will the light ray have travelled, according to the each observer's calculations).

Will have to think about this one.


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Offline ukmicky

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Re: Is Relativity Wrong?
« Reply #11 on: 05/10/2005 01:40:28 »
For them to get correct anwsers they have to make there calculations differently
 

The people on earth would make their calculation as normal.

The people who have returned from space would have to make their calculation taking into account the effects of relativity.

Both sets of people should then agree on everything.:)

Or am i still not understanding the question right.





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Offline Solvay_1927

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Re: Is Relativity Wrong?
« Reply #12 on: 05/10/2005 13:35:12 »
Michael - you're absolutely right (again).  But the question is HOW do they make their calculations?

Andrew(Rince)'s question, as I understand it, can maybe be represented as follows:

At noon, an earthling shoots off a photon of light into space, and simultaneously an astronaut shoots off to the moon.
At 10pm (earth time), the astronaut returns.  But the astronaut's watch reads 9pm (say), due to relativistic time dilation.
Now, the earthling and astronaut are together again and share the same inertial frame of reference again.  So they'll both agree about how far away the photon of light is - it's 10 billion km away (roughly - the speed of light is a bit over 1 billion kph).
So the problem is: the earthling says the photon has travelled 10 billion km in 10 hours, but the astronaut says it's travelled 10 billion km in NINE hours.  So the astronaut thinks the light has travelled at a faster rate!

This problem has been driving me quite mad for several hours.  But I think I might have a resolution now:

From the astronaut's point of view, the photon has NOT travelled in a straight line. The distortion of the astronaut's spacetime (due to her acceleration) means that, in the astronaut's 9 hours, the photon has only had to travel 9 billion km through the astronaut's spacetime.

Does this make sense to anyone?  Can anyone tell me if that's (sort of) right or not?

And can anyone explain HOW to calculate the distance the photon travels through the astronaut's spacetime (in simple terms - i.e. without having to take a full course in general relativity)?
I sort of understand the maths of special relativity (where velocity is uniform), but I can't work out how to take into account the acceleration (i.e. the astronaut stopping and turning around at the moon).

Ta.
Solvay.


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Offline ukmicky

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Re: Is Relativity Wrong?
« Reply #13 on: 05/10/2005 23:44:25 »
Hey Paul I seem to be getting good at this, maybe we should collaborate and come up with the new theory of everything.

You can be my research assistant.:D:D

___________________

As for your question maybe your trying to complicate things to much, your need to simplify things and take the journey as a whole rather than in stages.





Michael                                      
« Last Edit: 06/10/2005 04:22:47 by ukmicky »
 

Offline Solvay_1927

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Re: Is Relativity Wrong?
« Reply #14 on: 06/10/2005 22:47:19 »
Depends ... how much are you willing to pay for me to be your research assistant?

I need to read up more on relativity though - I suspect I still don't really understand it.



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Offline Solvay_1927

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Re: Is Relativity Wrong?
« Reply #15 on: 07/10/2005 16:31:59 »
Now I’ve thought about the question a bit more, I think you’re right Michael – I’m overcomplicating things.  Maybe it can be simplified this way:

While the astronaut is travelling, she sees the length (dimension in the direction of travel) of the earthling’s frame of reference contracted by a factor of 0.9 (i.e. same as the time dilation factor).

So while the earthling sees the photon travelling 10 billion km, the astronaut sees it travelling (inside the earthling’s reference frame) a distance of only 9 billion km.  So she calculates the correct speed of light (9 billion km in the earthling’s frame divided by 9 hours in the earthling’s frame).

When the astronaut comes to rest (i.e. is no longer moving from the earthling’s point of view), she’ll agree with the earthling that the photon is 10 billion km away.  She’ll just have a different perspective on how it got there!

(They must agree that the photon is 10 billion km away when they’re both at rest:  if the photon hits a mirror at that point, and the astronaut and earthling stay still while they wait for the photon to return, they’d both see it arrive back at the same time, 10 hours later).

But I’m still not sure I’ve really “got” it – it smells funny to me.  Can anyone tell me if the above reasoning is right or not?



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Offline Rincewind

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Re: Is Relativity Wrong?
« Reply #16 on: 08/10/2005 07:11:57 »
Mm, yeah, I suspected length dilation would be relativity's explanation, here's what I have to say about that:

There are a certain (well, random actually but with the law of averages and that...) number of quantum fluctuations in a given area of space.  If you perceive that area to be squidged (as with the moving astronaut) you would perceive a higher density of quantum fluctuations, no?

If you were moving, the rest of the universe would have a higher KE relative to you so this could account for the higher number of quantum fluctuations except that a vacuum has no mass with which to 'hold' kinetic energy, but then neither does light, and that has kinetic energy so... bleuuurgh, I dunno.

But, I've thought about this alot, and I am as sure as I can be that relativity should be symmetrical.  Your time should balance out and when you return to the same point in space, your time should be the same as those who remained there.  I cannot understand how a theory of relativity can produce this objectivity.  That is, that something which is 'moving' (in inverted commas because it all depends on the inertial frame) will lose time.  That suggests to me that if you reversed the inertial frame (centred it on the 'moving' object rather than the 'stationary' one), it would be the 'stationary' object that lost time.

It's been suggested to me that acceleration is the key, but if that's the case why don't the equations take any notice of acceleration (I'm sure there are more advanced equations I haven't encountered yet that do apply to accelerating objects but the point is you can work out time/length dilation just from knowing the relative velocity of two objects, which one accelerated is irrelevant).

My answer is that velocity is unimportant, what matters is displacement.  For every 300,000km you travel away from an object you lose a second, for every light-second you travel towards an object, you gain a second.  How does that sound to everyone?  (Don't worry about upsetting me if I'm wrong, as long as you explain why I'm wrong simply enough for me to understand, it'll stop me thinking about it and the whole reason I'm here is so that I can stop thinking about this and move onto something new to wonder about).  Perception is reality in this case.

We could argue that when we see light from a distant star, it's a thousand years old, or whatever, but I would argue that as the light has been moving at the speed of light and therefore experiencing no time, saying it's old and far away is saying the same thing twice, and not truly understanding the nature of time as a dimension which passes through every point in 3D space.  It would be more correct, in my understanding, to say the star is a thousand light years away, but what we're seeing is what is happening, not what was happening a thousand years ago.  And if we could travel there in an instant we would journey a thousand years into the star's future, but looking back at our planet we would see it a thousand years before we left.

And this is real.  And this is true.

Looking at space, the distance you are from something can always be worked out.  If two of it's coordinates are 0,0 and the third is, say, 5, then no matter how you twist these dimensions your distance can always be worked out to be 5.  I think the same is true when you account for the fourth dimension, and your distance can be measured either in kilometres (each=1/300,000sec) or seconds (each=300,000km) and these two units are interchangeable.

Someone should have sorted me out on this a long time ago, but the few I've managed to discuss it with (I'm sure you're all familiar with trying to discuss relativity with non-physicists) haven't shown sufficient understanding to convince me.  One of them holds a 2:1 in physics but was satisfied once he could do the maths and didn't really seem to associate the maths with reality, but the fault's probably mine.

Appreciate the time you've spent already btw, Solvay:)
« Last Edit: 08/10/2005 07:20:16 by Rincewind »
 

Offline Rincewind

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Re: Is Relativity Wrong?
« Reply #17 on: 08/10/2005 07:41:50 »
In relativity, if you travelled a vast distance across space at close to the speed of light you would be a long way from where you started, okay, simple enough.  If someone wanted to come after you, they could, and they would see you again, but if you were to travel back to them, they would have died hundreds of years ago.  What kind of sense does that make?
 

Offline ukmicky

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Re: Is Relativity Wrong?
« Reply #18 on: 08/10/2005 20:34:19 »
Originally posted by Rincewind

My answer is that velocity is unimportant, what matters is displacement. For every 300,000km you travel away from an object you lose a second, for every light-second you travel towards an object, you gain a second.


________________________
Hi rincewind

As you know Im not and expert and will never be:(,but what happens when an object travels around an object instead of away from it like the GPS satellites, which are now younger than they would be if they remained on earth?

Because these satellites are in constant motion around the earth the effects of relativity must be accounted for to maintain their positional accuracy. The newer satellite’s have three atomic clocks with an accuracy of 1 SECOND in a million years and have to continually communicate and adjust their times with earth base clocks because the satellites are in constant motion and due to relativity are running slower than atomic clocks on earth.

From what your saying if you turned the satellites around and sent them the opposite direction around the earth they would then make up any time lost when they were moving the other way and would be running faster than they were.:):)

Michael                                      
« Last Edit: 08/10/2005 20:42:33 by ukmicky »
 

Offline Rincewind

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Re: Is Relativity Wrong?
« Reply #19 on: 09/10/2005 14:59:10 »
Oh, is that really true?  Damn.

Someone (a physics student) once told me that time dilation had never been proved, that for every experiment which had backed up relatavistic time dilation there had been several which had had the opposite result.  That's what got me thinking along these lines.

My last two posts were a bit dodgy cos I was very sleep deprived but it's been something that's been playing around in the back of my mind for a while.  I feel like it's been resolved now and I can get on with not worrying about relativity - there are far cleverer people than me who can do that:)

I still don't really understand why one thing (the satellite) counts as moving, and its time goes slower, while the other thing (the Earth) counts as stationary though.  I guess the satellite is accelerating faster in gravity because of its lower mass but, as I said before, acceleration is not taken into account in the time/length dilation equations.  

On top of that, relativistically speaking, a body doesn't accelerate in gravity, does it? It just travels in a straight line through warped space time.

Is that it?  Is it because the satellite is travelling further through space time, getting to the same place.  It's not accelerating, it's just travelling faster and further in a straight(ish) line, and that's why its time runs slower.

OK, if relativity is right, why can't they just program the correct time dilation into the atomic clocks so that they run at the right speed with respect to Terran clocks, why do they have to keep in communication?

I can't really get my head around circular motion very well.  I guess an inertial frame can't be rotating because things obviously change when you're spinning, but what are you spinning relative to if there's no ether?  How does the body or the particle or whatever know that it's spinning?  Is it relative to the gravitational gradient maybe?  These are questions that didn't really bother me when I was doing physics at school but I've wondered about it a lot since.  I mean, a fundamental misunderstanding of what rotation is measured relative to or how rotation is measured could account for dark matter or dark energy or both, ay?  It could, I'm not saying it will.
 

Offline Andrew K Fletcher

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Re: Is Relativity Wrong?
« Reply #20 on: 09/10/2005 16:41:07 »
Space travel accelerates the ageing process and is well documented, the body undergoes a massive acceleration of the age related illnesses we will all become familiar with.

So, the space travel actually aged their bodies faster than if they had stayed on Earth.

Secondly, the 1969 alledged lunar landing had the computer capabilities of a modern day pocket calculator. Given the difficulties NASA has in saending astronauts into space, let alone landing them on the moon, I have to admit to being very suspicious about the USA Government telling a few porky's. Furthermore, the footage of the early moon landing is highly suspect now that technology to evaluate it properly has moved on.

So In all probability and relativity to your question, the hypothesis of relativity is relatively wrong in this case at least.



"The explanation requiring the fewest assumptions is most likely to be correct."
K.I.S. "Keep it simple!"
 

Offline ukmicky

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Re: Is Relativity Wrong?
« Reply #21 on: 09/10/2005 20:32:33 »
Did the americans land on the moon? well the russians believed it.and i believe it. oh and all the evidence as far as i'm concerned has proved it. so yes we did land on the moon.

And when we send men to mars,the sceptics will be out again saying the same things.

I believe this topic has also been discussed on this forum before.


Michael                                      
« Last Edit: 09/10/2005 21:03:28 by ukmicky »
 

Offline Andrew K Fletcher

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Re: Is Relativity Wrong?
« Reply #22 on: 10/10/2005 09:27:39 »
Alrighty then, on your belief the Americans landed on the moon so they did. Wouldnt stand up in a courtroom Michael.

I have also seen the evidence and agree with the points raised about land marks in different places in relation to the angle of the photographs, the direction of shadows, the speed at which the doust moves when impacted by the astronauts feet, etc etc.

"The explanation requiring the fewest assumptions is most likely to be correct."
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Offline itsjustme

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Re: Is Relativity Wrong?
« Reply #23 on: 10/10/2005 13:52:51 »
hey you know that quantum laws dont have to obide by classical laws.
 

Offline Solvay_1927

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Re: Is Relativity Wrong?
« Reply #24 on: 10/10/2005 22:41:35 »
Apologies in advance, but this may be a long posting - so I'll split it up into sections.

Firstly, Andrew K Fletcher:
Is there any chance you could post your conspiracy theory under another topic?  Maybe create a new topic or resurrect an old topic where this has been discussed before (as Michael has pointed out)?
I don't mean to sound rude - I'm interested (though sceptical) re: what you have to say on the conspiracy theory, and I'm sure there are others who would be interested in debating it - it's just that the current topic is relativity, and going off on such an unrelated tangent will make the topic very confusing and impossible to follow.
Thanks.
 

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Re: Is Relativity Wrong?
« Reply #24 on: 10/10/2005 22:41:35 »

 

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