relativity

@rosborne979,

rosborne979 wrote:

As Contrex has said, the speed of light has been measured

I think that Michelson's experiment is wonderfully elegant and ingenious. I really cannot see where to start attacking it.In today's high-tech world many people tend to look with scorn on the days before colour television, or computers, etc. Yet this guy, in the Jazz Age, using equipment that anyone can duplicate today, measured the speed of light to a remarkable degree of accuracy.

1 Reply

@dalehileman,

dalehileman wrote:

Maybe it isn't convincing but neither were Einstein's assertions at the very first. Hitler called 'em "Jewish Science."

Digging deeper I see...

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@contrex,

Quote:

I really cannot see where to start attacking it.

At risk of repetition, again, once more, to clarify a clarification, I hadn't attacked it at all but merely provided an alternative way of looking at it

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@dalehileman,

dalehileman wrote:

But Ros I thought I had

Maybe you need to be more concise. Tell us concisely, why you think that light speed is infinite when you acknowledge that it has been measured and is not infinite.

1 Reply

@rosborne979,

Quote:

Tell us concisely, why you think that light speed is infinite when you acknowledge that it has been measured and is not infinite.

Again, Ros, I thought I had pretty exhausted my viewpoint. But we have three different folk at noon placing the time on Mars at 12:05 plus or minus 5 minutes, and I'm only suggesting that a special consideration of Isaac's view might prove valuable in the intuitive grasp of certain changes apparent to Al in his mass, length, and clock reading

That's about as concise as I can get

I've posted my observations on other sites where though disagreeing others at least understood my position

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@dalehileman,

dalehileman wrote:

But we have three different folk at noon

Noon where?

1 Reply

@contrex,

Quote:

Noon where?

Please Conn review my postings. At noon on Earth, Al watching Isaac on his way to Mars, and Marty just passing by in the other direction

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@dalehileman,

dalehileman wrote:

Quote:
Noon where?

Please Conn review my postings. At noon on Earth, Al watching Isaac on his way to Mars, and Marty just passing by in the other direction

I presume you mean when it is 12:00 by the clock at some place on the earth. I find it hard to remember who "Al" and "Marty" are, I'll read your scenario again.

I cannot help thinking that all you are trying to do is over-simplify relativity (into something false) because you don't understand it.

1 Reply

@contrex,

Quote:

I presume you mean when it is 12:00 by the clock at some place on the earth.

It's Al's clock, Con, as I thought I had explained but apparently not very clearly, at the moment of Isaac's takeoff and Marty's passing by

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I find it hard to remember who "Al" and "Marty" are,

Al stands by upon Earth, observing the two flybys. Marty had launched from Mars 5 minutes earlier by Al's reckoning

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I'll read your scenario again.

Please feel free to do so

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I cannot help thinking that all you are trying to do is over-simplify relativity

I'm attempting to provide another way to look at time-at-a-distance that might satisfy requirements of the Intuition

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(into something false)

Could be there's a basic flaw in my reasoning but haven't yet encountered it. I'll readily admit however it's hard to picture a Universe in which it's five minutes later everywhere else at a distance of 5 light minutes

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because you don't understand it.

I think I have a modest grasp of the fundamentals howevermuch others might disagree

I get the impression that in spite of all the technical expertise, there's not much interest in relativity hereabout

But thanks Con for your participation

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You don't need to invoke the speed of light anyway. If you have two extremely accurate clocks, which tick at exactly the same rate, and they are synchronised to show exactly the same time, and you keep one here on earth, and send the other up to the International Space Station and keep it there for 6 months, and then bring it back and compare the two, it will be behind the one that stayed behind, by about 0.007 seconds. It is only the fact that the effect is so small in everyday experience that stops us being aware of it. If I had two atomic clocks and sent one by train to Madrid and back, I could compare the readings and see the difference.

There is an equation for calculating the slowdown of time in a system which is moving with another system:

http://www.fourmilab.ch/cship/equations/timedial.gif

This says that the time passed in the moving system, "t prime" (the letter t with a little tick) is equal to:

the time passed in the stationary system (t without a prime), divided by the square root of (one minus the velocity squared over the speed of light squared)

This has been confirmed by experiments, modern ones including the Hafele-Keating experiment in 1971. Atomic clocks were flown aboard commercial airliners twice around the world, first eastward, then westward, and then compared to others that remained at the United States Naval Observatory. When reunited, the differences were consistent with the predictions of special and general relativity. In fact the effect was observed experimentally in the 1930s.

I think you are of the opinion that the non-existence of a "universal now" is against intuition, and while I can see where you are coming from, I don't think that Hafele and Keating's clocks were faulty, any more than Michelson's measurements were.

1 Reply

@contrex,

Quote:

You don't need to invoke the speed of light anyway

Well Con I sort of do 'cause it plays a sort of crucial role in my speculation

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If I had two atomic clocks and sent one by train to Madrid and back, I could compare the readings and see the difference.

Yes thanks Con but I'm aware of the effect. But I have given Isaac and Marty a sturdy constitution tolerating the most immense acceleration and very special ship capable of travel at nearly c so that their clocks are in effect stopped just an instant after takeoff

Quote:

I think you are of the opinion that the non-existence of a "universal now" is against intuition,

Yes sort of. Of course time at a distance depends upon your state of motion but there is, as I had mentioned, an unspoken assumption that it's really the same time everywhere

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and while I can see where you are coming from,

Not quite yet, apparently

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don't think that Hafele and Keating's clocks were faulty, any more than Michelson's measurements were.

Nor do I. By the tenets of conventional relativity they're perfectly accurate. My cerebration, as I remember having remarked, merely constitutes a new way of looking at time-at-a-distance more consistent with the apparent changes that seem to take place in a moving object

..that is, whether or not they take place its itself relative; hence "relative relativity." But once more thanks for your participation

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@dalehileman,

dalehileman wrote:

time at a distance

This is the key thing that you need to explain more clearly, or else be exposed to the accusation of talking nonsense. Some math would reinforce your case.

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@dalehileman,

dalehileman wrote:

But I have given Isaac and Marty a sturdy constitution tolerating the most immense acceleration and very special ship capable of travel at nearly c so that their clocks are in effect stopped just an instant after takeoff

You don't need imaginary people with cute names. Why risk pulverising them? A (very sturdy) travelling clock and a stationary one will do.

1 Reply

@dalehileman,

dalehileman wrote:

there is, as I had mentioned, an unspoken assumption that it's really the same time everywhere

That assumption is not present where I am located.

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@dalehileman,

dalehileman wrote:

Quote:
You don't need to invoke the speed of light anyway
Well Con I sort of do 'cause it plays a sort of crucial role in my speculation

Of course c is present in the Lorentz equation, and therefore is central to time dilation calculation (I should have emphasised that) even though the effect is measurable at lower speeds. What I am getting at is that what you are doing is, essentially, "hand-waving" unless you have some mathematics?

http://en.wikipedia.org/wiki/Handwaving

http://www.thefreedictionary.com/hand+waving

http://c2.com/cgi/wiki?HandWaving

Here's a list of techniques (see 1.3)

http://school.maths.uwa.edu.au/~berwin/humour/invalid.proofs.html

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@contrex,

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You don't need imaginary people with cute names.

I was merely following Alex's lead, it seemed quite appropriate

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Why risk pulverising them?

Because their traveling at c greatly simplifies the discussion

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….unless you have some mathematics?

I'm not much of a mathematician but my speculation requires no math. Of course it does leave some q's unanswered; for instance, though somewhat OT, why c had assumed a particular value

dalehileman wrote:
time at a distance

Quote:

This is the key thing that you need to explain more clearly

In the case of my illustration it refers to the supposed reading of Marty's clock back on Mars when it's noon at home. You may wish to again reread my pertinent postings but if the confusion persists I apologize most profusely; though I've about exhausted my ability at clarification

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@dalehileman,

dalehileman wrote:

Again, Ros, I thought I had pretty exhausted my viewpoint. But we have three different folk at noon placing the time on Mars at 12:05 plus or minus 5 minutes, and I'm only suggesting that a special consideration of Isaac's view might prove valuable in the intuitive grasp of certain changes apparent to Al in his mass, length, and clock reading

That's about as concise as I can get

That's about the most awkward explanation of anything I've ever heard. I can't even tell what you are suggesting or disagreeing with, and I've read your original post as well (it wasn't any clearer).

You have to be very careful with these types of thought experiments to state them clearly and simply.

1 Reply

@rosborne979,

Quote:

You have to be very careful with these types of thought experiments to state them clearly and simply.

I would Ros if I knew what was so confusing

Con asks about the math. Well, expressing time-at-a-distance d as t = d/c

Expressed in millions of miles and in minutes, when the distance to Mars is 60, with an approximate value of c = 12 then it's 5 minutes later there

There's no conceivable way it can be said more simply

1 Reply

@dalehileman,

dalehileman wrote:

Expressed in millions of miles and in minutes, when the distance to Mars is 60, with an approximate value of c = 12 then it's 5 minutes later there

We already know that the "light minute" distance between Earth and Mars is approximately 4 minutes or 20 minutes depending on where they are in their orbit. What part of that is bothering you? I don't get what you are objecting to.

1 Reply

@rosborne979,

Quote:

What part of that is bothering you?

Nothing concerning classical relativity is bothering me. What does bother me is my apparent inability to explain my speculation

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I don't get what you are objecting to.

I'm not objecting to anything, merely providing a slightly different way of viewing time-at-a-distance

2 Replies

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