Speed of light revisited yet still again

@dalehileman,

dalehileman wrote:

Maybe we're having a kind of semantic impasse

You've got me worried now! This morning I made an Excel spreadsheet which applies the time-dilation formula, I'll fool around with it some more and come back.

1 Reply

@contrex,

You have me worried Con; after all these years and decades have I misunderstood the Whole Shebang

Or is it a problem of the "stationary reference" per my edit in #…….912 above

I await the results of your upcoming study with the utmost anticipation

1 Reply

@dalehileman,

dalehileman wrote:

after all these years and decades have I misunderstood the Whole Shebang

I don't think so; I think I misunderstood your question. Watch this space! See my other post about another forum.

1 Reply

@contrex,

Yea Con and thanks for that link

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OK.

This is the formula for calculating time dilation

http://i124.photobucket.com/albums/p29/badoit/TdelEqn_zps809316e1.jpg

where:
t = time observed in the other reference frame (the astronaut in the spaceship)
t0 = time in observers own frame of reference (Earth)
v = the speed of the moving object
c = the speed of light in a vacuum

I put this in a spreadsheet and played around with various values for the speed of the moving object.

If I have it right, where the speed v is 0.99999999999999 c, the spaceship takes t0=10 minutes according to an observer on Earth, the astronaut would experience a time passing t=0.0000849 seconds, well within the capabilities of a 1960s era atomic clock.

In an imaginary thought-experiment type of situation, of course you can push the speed up to any arbitrarily big fraction of the speed of light and of course the time experienced by the astronaut will shrink to an equally arbitrarily small duration. It may exceed the ability of any imaginable clock to resolve, but it won't actually go to zero. It can't.

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@contrex,

Under special relativity for the person on the spacecraft the same dilation would apply in observing clocks on earth.

The person on the spacecraft would see 10 minutes pass while observing that the clocks on earth would stand still. (If we ignore acceleration and general relativity.)

Quote:

For instance, two rocket ships (A and B) speeding past one another in space would experience time dilation. If they somehow had a clear view into each other's ships, each crew would see the others' clocks and movement as going more slowly. That is, inside the frame of reference of Ship A, everything is moving normally, but everything over on Ship B appears to be moving more slowly (and vice versa).

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

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@parados,

parados wrote:

The person on the spacecraft would see 10 minutes pass while observing that the clocks on earth would stand still.

Nearly stand still.

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@contrex,

Thanks Con for that formula

Quote:

t=0.0000849 seconds, well within the capabilities of a 1960s era atomic clock

…explaining of course why Marty unaware of its passage

1 Reply

@contrex,

Relatively speaking of course.

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@dalehileman,

dalehileman wrote:

Thanks Con for that formula

Quote:
t=0.0000849 seconds, well within the capabilities of a 1960s era atomic clock
…explaining of course why Marty unaware of its passage

If Marty had an electronic gizmo he could measure it. The human brain, however, cannot register durations of much less than about 0.1 second.

1 Reply

@parados,

Quote:

(If we ignore acceleration and general relativity.)

Interesting Para you should specify acceleration, something that's oft bothered me, the idea that the guy who experiences acceleration is the one whose clock stops 'cause I get a feeling its mention implies some sort of stationary ref, which standard Relativity denies

But

Quote:

(If we ignore acceleration and general relativity.)

then why would she see our clocks standing still; I'd suppose instead she'd see 20 minutes elapse here

Con help

1 Reply

@contrex,

Quote:

Nearly stand still.

I'm not sure, Con, per my #…….997 because remember, there's no relativity

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@contrex,

If Marty had an electronic gizmo he could measure it.

Yea Con she could. Called her "she" to prevent her mention getting mixed up with that of one of us back home, in LC to distinguish her mention from that of Hers

Quote:

The human brain, however, cannot register durations of much less than about 0.1 second

There's another reason it doesn't register

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@dalehileman,

Quote:

our little visible area moves at c

s/b "...doesn't move at c…"

Con how come you didn't catch this

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@dalehileman,

dalehileman wrote:

"...how do we know that our little visible area moves at c with respect to the rest of the Universe..."

I'd really like to know what you mean by this.

2 Replies

@Brandon9000,

It means, you are already in motion Brandon, in several directions at once....at least.

Thought you knew everything???

1 Reply

@dalehileman,

Quote:

then why would she see our clocks standing still

Because that is how relativity works.

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@DNA Thumbs drive,

For relativity, motion only matters when comparing 2 objects with different motions. It's only about the objects you are comparing and they both see the same thing for the other object. There is no C outside the 2 objects you are comparing. By introducing another object you are just introducing a new comparison not an objective observer that is motionless.

1 Reply

@parados,

relativity is just a tad bit more complex than that....................

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@Brandon9000,

dalehileman wrote:
"...how do we know that our little visible area moves at c with respect to the rest of the Universe..."

Quote:

I'd really like to know what you mean by this.

Sorry Bran, it was a typo; I meant to ask,

How do we know that what we now call The Visible Universe in its entirety is not moving at velocity c with respect to a much larger body, the actual Universe

You're to be congratulated, Bran as that nobody else picked it up

2 Replies

Speed of light revisited yet still again

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