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brentwood
Carpal Tunnel

Reged: 11/04/05

Re: Scary relativity [Re: The Mighty Mo]
#6215614 - 11/25/13 04:42 PM

I can do thought experiments that show that time does in fact slow down at speeds approaching c. I do this with bouncing balls, light beams and with deference to the giants of the past, railway carriages. For this to work, you have to accept that c is a constant. If I really work at it, and write some of it down, I can also show the contraction in length along the direction of travel and also can see the logic of the mass increase.
The lightbeam will still leave the moving car at c, it is just that to an outside observer, the car is following closely behind.
Can you respond to this Danny without using any maths? what does the outside observer see.

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deSitter
Still in Old School

Reged: 12/09/04

Re: Scary relativity [Re: brentwood]
#6215647 - 11/25/13 04:58 PM

Everybody STOP thinking for a while I'll do the thinking! Just pay attention!

Believe me, this will be worth it.

-drl

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choran
Pooh-Bah

Reged: 12/28/12

Re: Scary relativity [Re: deSitter]
#6215666 - 11/25/13 05:03 PM

"Everybody STOP thinking for a while."

FINALLY, something I can easily do!!

Edited by choran (11/25/13 05:04 PM)

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deSitter
Still in Old School

Reged: 12/09/04

Re: Scary relativity [Re: choran]
#6215686 - 11/25/13 05:12 PM

The Moon moves over the Sun. It exactly eclipses it, so that totally is a mere blink of the eye - but for that fraction of a millisecond, the Sun is covered and no light gets to Earth from its photosphere. And, this is a perfect Moon, with no bumps and a perfect sphere, likewise a perfect Sun, with no tidal bulging.

So now say the Moon acquires a large tangential speed to Earth. Naively we expect the Lorentz contraction in the direction of its motion to cause the eclipse to not happen...

That's the problem we're solving. In it are ALL the other problems of how moving things look.

-drl

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Otto Piechowski
Pooh-Bah

Reged: 09/20/05

Loc: Lexington, KY
Re: Scary relativity [Re: deSitter]
#6215700 - 11/25/13 05:15 PM

I think I follow. The moon is moving at a near light speed so it "shrinks" in the direction of movement (perpendicular to the line connecting earth to sun). Since it shrinks, it should not cover the sun.

?

Otto

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Crow Haven
Pooh-Bah

Reged: 01/09/09

Loc: Oregon USA
Re: Scary relativity [Re: Otto Piechowski]
#6215711 - 11/25/13 05:23 PM

Otto, so does that mean that the light from the Sun would get to the observer before the Moon appears to?

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Otto Piechowski
Pooh-Bah

Reged: 09/20/05

Loc: Lexington, KY
Re: Scary relativity [Re: Crow Haven]
#6215728 - 11/25/13 05:35 PM

Maya,

Let's let Danny drive this description. I was just trying to understand what he meant by tangential and why he said, according to what we know about SR, that the moon should never cover the sun. (Oh, in case you are wondering about that "shrink" thing, according to the popularized version of SR I learned on my own, to an outside observer looking at an object moving perpendicular (at right angle) to the observer, the length of an object moving at a near light speed, "shrinks" in the direction of the movement. According to the formula (if I remember it correctly) if an object at "rest" is 10 meters long, once it starts moving at a constant 90% the speed of light, to an outside observer it will only appear 4.36 meters long.)

Otto

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Crow Haven
Pooh-Bah

Reged: 01/09/09

Loc: Oregon USA
Re: Scary relativity [Re: Otto Piechowski]
#6215740 - 11/25/13 05:41 PM

Thanks for the explanation, Otto.

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Rick Woods
Postmaster

Reged: 01/27/05

Loc: Inner Solar System
Re: Scary relativity [Re: deSitter]
#6215773 - 11/25/13 06:04 PM

Quote:

The Moon moves over the Sun. It exactly eclipses it, so that totally is a mere blink of the eye - but for that fraction of a millisecond, the Sun is covered and no light gets to Earth from its photosphere. And, this is a perfect Moon, with no bumps and a perfect sphere, likewise a perfect Sun, with no tidal bulging.

So now say the Moon acquires a large tangential speed to Earth. Naively we expect the Lorentz contraction in the direction of its motion to cause the eclipse to not happen...

That's the problem we're solving. In it are ALL the other problems of how moving things look.

-drl

Now come on - we've all confessed to being ignoramuses; have some charity!
What's the Lorentz Contraction and why would we expect that? This isn't going to work unless we understand the steps leading up to the solution.

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EJN
Carpal Tunnel

Reged: 11/01/05

Loc: 53 miles west of Venus
Re: Scary relativity [Re: deSitter]
#6215788 - 11/25/13 06:14 PM

deleted

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PeterR280
Pooh-Bah

Reged: 05/27/13

Re: Scary relativity [Re: Rick Woods]
#6215792 - 11/25/13 06:16 PM

total confusion.

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Rick Woods
Postmaster

Reged: 01/27/05

Loc: Inner Solar System
Re: Scary relativity [Re: dickbill]
#6215806 - 11/25/13 06:26 PM

Quote:

Quote:

ALL observers will always measure the speed of light as the same, regardless of their state of relative motion

That in itself is counterintuitive, so why would we start with a counterintuitive postulate?

Counterintuitive doesn't bother me. But, is this what we're saying?

At rest: c = 186,000 mph relative to that (at rest) condition.

At speed (c - 1 fpm), it still goes 186,000 mph; but that's taking SpaceGirl's speed as the new "at rest" and measuring from there. At that speed, time and space are warped and compressed, and the (new) 186,000 miles are squeezed into whatever portion of the (old) one foot light can travel in one second (as measured at the near-c speed).

Would a weak analogy be one of those pictures where, when you look at it straight on, it's just a row of straight vertical lines; but when you look at it from the lower edge of the paper, the undistorted view appears?

I suspect that to make the analogy I'm looking for, you have to mix the two states, which isn't valid somehow. Like, translating the old 1-foot measure into the at-speed condition.

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PeterR280
Pooh-Bah

Reged: 05/27/13

Re: Scary relativity [Re: PeterR280]
#6215809 - 11/25/13 06:27 PM

On the positive side if you learn tensors you ill be half way there to general relativity.

Why would you say that people would expect the Moon would to shrink due to the Lorentz contraction?

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Rick Woods
Postmaster

Reged: 01/27/05

Loc: Inner Solar System
Re: Scary relativity [Re: EJN]
#6215813 - 11/25/13 06:28 PM

Quote:

Quote:

What's the Lorentz Contraction

L = L0 * sqrt(1 - (v^2/c^2))

What does it describe?
I really am trying to get my squishy little brain around this somehow.

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choran
Pooh-Bah

Reged: 12/28/12

Re: Scary relativity [Re: Rick Woods]
#6215827 - 11/25/13 06:34 PM

Re: sun/moon example, I'm betting no Lorentz "length" transformation (shortening in direction of movement), but instead a "rotation" so sphere stays a sphere. Get your popcorn, this is gonna get sticky!

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PeterR280
Pooh-Bah

Reged: 05/27/13

Re: Scary relativity [Re: choran]
#6215840 - 11/25/13 06:38 PM

First of all Special Relativity deals with inertial reference frames without acceleration or gravity. Why introduce something like an orbit if you are explaining Special Relativity? It makes it even more confusing.

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PeterR280
Pooh-Bah

Reged: 05/27/13

Re: Scary relativity [Re: PeterR280]
#6215849 - 11/25/13 06:41 PM

By the way how many years did it take Einstein to get there from Special Relativity?

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choran
Pooh-Bah

Reged: 12/28/12

Re: Scary relativity [Re: PeterR280]
#6215857 - 11/25/13 06:47 PM

1905 (SR) to about 1915 (GR) I think.

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EJN
Carpal Tunnel

Reged: 11/01/05

Loc: 53 miles west of Venus
Re: Scary relativity [Re: choran]
#6215858 - 11/25/13 06:48 PM

And now for a musical interlude from Grace Slick & Jefferson Airplane - White Rabbit

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choran
Pooh-Bah

Reged: 12/28/12

Re: Scary relativity [Re: EJN]
#6215878 - 11/25/13 06:59 PM

Yup. Rabbit Hole dead ahead!! I think when Danny gets back we're all in for it. Teacher leaves the classroom and everybody acts up. LOL

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