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I love this film. It's spectacular, especially in IMAX 3D. But something about
it just bothers me.
If I understand 'orbital mechanics' at all (and gravity), then for a given orbit
above the Earth, objects go at a certain speed or velocity.
If the objects travelled faster, they would be in a different orbit.
If that's true, then one of the main 'set pieces' of the film-- the orbiting
space station being destroyed by fast-moving debris hitting it-- seems
unnatural. Wouldn't that debris naturally be in some different orbit, because of
its different speed? (Unless the debris was from an explosion-- blasting out in
all directions from some particular orbit.) I don't remember if such an
explosion was the cause.
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On 01/19/2018 05:40 PM, Kenneth wrote:
> I love this film. It's spectacular, especially in IMAX 3D. But something about
> it just bothers me.
>
Gravity: the movie that proves George Clooney would rather float away in
space and die, then spend time with a woman his own age.
- Tina Fey
--
dik
Rendered 344576 of 345600 pixels (99%)
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> Wouldn't that debris naturally be in some different orbit, because of
> its different speed?
It depends on the mass. Two equal masses [w][c]ould occupy the same orbit.
But you can have circular orbits, elliptical orbits, and you also have
360-degrees of rotation around both orthogonal axes - so you could be travelling
at 70,000 mph in one direction, and get t-boned, or hit by an object head-on in
the "oncoming lane".
Then there's the whole perturbation thing, so all of the orbits are going to
have some variation over time....
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On Fri, 19 Jan 2018 19:52:18 -0500, Bald Eagle wrote:
>> Wouldn't that debris naturally be in some different orbit, because of
>> its different speed?
>
> It depends on the mass. Two equal masses [w][c]ould occupy the same
> orbit.
>
> But you can have circular orbits, elliptical orbits, and you also have
> 360-degrees of rotation around both orthogonal axes - so you could be
> travelling at 70,000 mph in one direction, and get t-boned, or hit by an
> object head-on in the "oncoming lane".
>
> Then there's the whole perturbation thing, so all of the orbits are
> going to have some variation over time....
Yup, agreed. On ISS they occasionally have to perform collision
avoidance maneuvers (an article in 2015 reports they'd done about 25 of
them at that time).
--
"I learned long ago, never to wrestle with a pig. You get dirty, and
besides, the pig likes it." - George Bernard Shaw
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Am 20.01.2018 um 01:52 schrieb Bald Eagle:
>> Wouldn't that debris naturally be in some different orbit, because of
>> its different speed?
>
> It depends on the mass. Two equal masses [w][c]ould occupy the same orbit.
No, the only mass the orbit depends on is the celestial body the objects
orbit around.
(At least as long as atmospheric drag is not a relevant factor.)
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Am 19.01.2018 um 23:40 schrieb Kenneth:
> If that's true, then one of the main 'set pieces' of the film-- the orbiting
> space station being destroyed by fast-moving debris hitting it-- seems
> unnatural. Wouldn't that debris naturally be in some different orbit, because of
> its different speed? (Unless the debris was from an explosion-- blasting out in
> all directions from some particular orbit.) I don't remember if such an
> explosion was the cause.
Yes, such an explosion was indeed the cause. IIRC that explosion in turn
was caused by another collision.
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"Bald Eagle" <cre### [at] netscape net> wrote:
> > Wouldn't that debris naturally be in some different orbit, because of
> > its different speed?
>
>
> But you can have circular orbits, elliptical orbits, and you also have
> 360-degrees of rotation around both orthogonal axes - so you could
> be travellingat 70,000 mph in one direction, and get t-boned, or hit by
> an object head-on in the "oncoming lane".
Yeah, I completely forgot about those little facts; there are an infinite number
of 'great circles' around the Earth for any given orbit... as well as their
reversed directions!
> It depends on the mass. Two equal masses [w][c]ould occupy the same orbit.
Like Clipka says, I think the different masses of the various objects (in the
same orbit) can be ignored. Let's say there are two objects: the U.S. Space
shuttle, and an apple(!) I'm guessing that both can be launched into the same
orbit, given the correct trajectories and forces. Assuming both are in nicely
circular orbits, they are actually 'falling' around the Earth. Neglecting air
resistance, any two objects 'fall' at the same rate, regardless of their masses.
(The old Galileo experiment, from the Tower of Pisa.) So it follows that the
Space shuttle and the apple-- in the same orbit-- are going at the same speed or
velocity. (If their speeds were different, one would head further off into
space-- attaining a higher orbit, or maybe a more eccentric one?)
I find that it's far more fun to CONJECTURE about things than to actually look
up the facts :-P Just like the ancient Greeks! (Well, they did OK with
geometry, I guess...)
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On 20/01/2018 16:09, Kenneth wrote:
> Just like the ancient Greeks! (Well, they did OK with
> geometry, I guess...)
But not that great with Irrational numbers or beans. ;-)
--
Regards
Stephen
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The main thing that bothered me was that Clooney basically tells Bullock
to point directly toward the Chinese module and hit the gas.
But:
1. Isn't it really hard to move between two locations in a straight line
in Space, so close to a large body such as the Earth? Aren't successful
orbital maneuvers really complicated, time-consuming and hard to pull off?
2. Wouldn't it take a really long time to cover the distance between two
space stations at the rate she was moving in her suit (e.g. slow enough
so she could stop herself by grabbing on with her hands, IIRC)? Or do
space stations typically live within a few kilometers of each other?
Never got to see the movie in imax.
Mike
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On 21/01/2018 16:37, Mike Horvath wrote:
> The main thing that bothered me was that Clooney basically tells Bullock
> to point directly toward the Chinese module and hit the gas.
>
> But:
>
> 1. Isn't it really hard to move between two locations in a straight line
> in Space, so close to a large body such as the Earth? Aren't successful
> orbital maneuvers really complicated, time-consuming and hard to pull off?
> 2. Wouldn't it take a really long time to cover the distance between two
> space stations at the rate she was moving in her suit (e.g. slow enough
> so she could stop herself by grabbing on with her hands, IIRC)? Or do
> space stations typically live within a few kilometers of each other?
>
> Never got to see the movie in imax.
>
>
I think the real problem is that orbital mechanics is not cinema
friendly. The public expect (from their experience on Earth) that if you
accelerate towards an object you get closer, quicker in a straight line.
Not that your orbit will get higher or lower. That is what stopped me
watching any of the Star Wars follow ups.
--
Regards
Stephen
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