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Is there no up or down in outer space?

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Venger
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26 Jan 2013, 4:18 pm

Trencher93 wrote:
I learned about this in the 1980s! Lionel Richie had a song "Dancing on the Ceiling".


That would be funny if there was a big party at the South-Pole Station, and everybody was dancing to that song. :lol:

It would be a real life version of the video for that song.



ruveyn
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26 Jan 2013, 8:35 pm

Venger wrote:
Trencher93 wrote:
I learned about this in the 1980s! Lionel Richie had a song "Dancing on the Ceiling".


That would be funny if there was a big party at the South-Pole Station, and everybody was dancing to that song. :lol:

It would be a real life version of the video for that song.


Down is toward the c.o.g. of the planet. Up is in the opposite direction.

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Venger
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26 Jan 2013, 8:59 pm

So is the North Pole really the top of the world, and the South Pole the bottom of it? lol



ruveyn
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26 Jan 2013, 9:05 pm

Venger wrote:
So is the North Pole really the top of the world, and the South Pole the bottom of it? lol


No. North Up, South Down is a map convention. The critical directions are (1) toward the center of mass of the planet and (2) away from the center of mass. (1) is Down. and (2) is Up. No matter where you stand on Earth your feet are down and your head is up.

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BlackSabre7
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26 Jan 2013, 9:43 pm

naturalplastic wrote:
BlackSabre7 wrote:
I think I remember seeing that! Yes, that would be a step up from the usual. Don't get me wrong, I LOVE next gen. Data is my hero. :heart:


Wait a minute!

Aspie women LIKE Data (the TV character) ?!?!?!?!

I could act like a dorky android...for you!



I can't speak for anyone else, but I would definitely trade in my psychopathic husband with post traumatic stress syndrome and no education for a smart, nice, calm Data. In a heartbeat.
I'm a dork too, so that would be welcome.
And Data could finish him off for me, without any troublesome feelings of guilt to bug me with.

Ummm, too far? :bball:



eric76
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28 Jan 2013, 7:39 am

Einstein had a thought experiment about how to tell whether you are in a stationary elevator on the surface of the Earth or an elevator out in space being accelerated "upward" with the same acceleration as the gravitational acceleration of the Earth.

If you were on the elevator in space, "up" would obviously be in the direction in which you and the elevator are being accelerated.



ruveyn
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28 Jan 2013, 10:38 am

eric76 wrote:
Einstein had a thought experiment about how to tell whether you are in a stationary elevator on the surface of the Earth or an elevator out in space being accelerated "upward" with the same acceleration as the gravitational acceleration of the Earth.

If you were on the elevator in space, "up" would obviously be in the direction in which you and the elevator are being accelerated.


Or, equivalently, opposite the direction in which you are being pulled by gravity. By the way, there equivalence principle only applies to -uniform- gravitational fields. In a real gravitational field, like at the surface of our planet, there are tidal forces. The gravity acting on a rod 100 feet long and aligned towed the center of mass of the earth pulls more on the end nearest the surface than the end furthest away. Likewise a long rod hold horizontally is pulled in somewhat opposite direction at the ends (I live it as an exercise for you to figure that one out).

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eric76
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28 Jan 2013, 10:46 am

ruveyn wrote:
eric76 wrote:
Einstein had a thought experiment about how to tell whether you are in a stationary elevator on the surface of the Earth or an elevator out in space being accelerated "upward" with the same acceleration as the gravitational acceleration of the Earth.

If you were on the elevator in space, "up" would obviously be in the direction in which you and the elevator are being accelerated.


Or, equivalently, opposite the direction in which you are being pulled by gravity. By the way, there equivalence principle only applies to -uniform- gravitational fields. In a real gravitational field, like at the surface of our planet, there are tidal forces. The gravity acting on a rod 100 feet long and aligned towed the center of mass of the earth pulls more on the end nearest the surface than the end furthest away. Likewise a long rod hold horizontally is pulled in somewhat opposite direction at the ends (I live it as an exercise for you to figure that one out).

ruveyn


Another possible way to distinguish between an elevator at rest on the Earth and one being accelerated in space would be by measuring whether or not two plumb bobs are actually parallel. If in the gravitational field of Earth, both wold point toward the center of the Earth and would not be parallel.



ruveyn
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28 Jan 2013, 12:01 pm

eric76 wrote:

Another possible way to distinguish between an elevator at rest on the Earth and one being accelerated in space would be by measuring whether or not two plumb bobs are actually parallel. If in the gravitational field of Earth, both wold point toward the center of the Earth and would not be parallel.


Exactly. That corresponds to the forces on the ends of a long horizontally aligned rod.

Gravitation is so weak, we can scarcely detect the mis-alignment of the plumb bobs here on Earth. However the tides indicate this in a remarkably clear manner. In a rising elevator there are no tides.

Einstein's Equivalence Principle equating uniform gravitation with acceleration is manifested only in infinitesimally small volumes of space. It is true locally, but not globally. When you paste together all the small portions of space time, you get the curvature of the space-time manifold.

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LupaLuna
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29 Jan 2013, 3:10 pm

You guys might find this interesting.

http://www.youtube.com/watch?v=i0g3g6AvLtM



Ozoro
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29 Jan 2013, 8:21 pm

Your sense of up and down is based on the pull of gravity. So since there is little to no gravity in space you will not have a sense of up and down.



Jitro
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29 Jan 2013, 8:25 pm

Is there right and left in space?

Is there back and forth in space?



Ozoro
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29 Jan 2013, 8:42 pm

Right, Left, Back, and Forth are all dependent on your orientation, which is why those directions are different even on earth depending on which way you are facing. So yes you would have a feel for those directions.



ruveyn
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30 Jan 2013, 8:14 am

Jitro wrote:
Is there right and left in space?

Is there back and forth in space?


Chirility or right/left handedness is real. It is also built into the weak interaction (so called weak force).

See: http://www.nobelprize.org/nobel_prizes/ ... press.html

Yang got a novel Prize just 3 years after his discovery. And do not forget Madam Wu who was the experimental brains behind the deed.

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