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# If a helicopter stays high enough can it travel one time zone per hour without moving

Due to the Earth's rotation, you see... Why don't objects above ground including the atmosphere move at a different speed to the Earth's rotation? Centrifugal force, Inertia, Gravity, Magnetism or something else?

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Momentum. It's all relative (yay! non-lightspeed Relativity talk!). The helicopter's still moving at the speed at which the Earth is rotating, so it doesn't move "back" (wait, it'd be forward, wouldn't it) through the time zones.

You're sitting in a chair? Not moving at all? You're really going a few tens of thousands of miles per hour (across a few different vectors that are all changing constantly, but that's less important). Earth's spinning on its axis (1,000 MPH), going around the sun (90 miles a second), the sun's hurtling around the galaxy (14,000 MPH), and the Milky Way's shooting off into the Universe (can't measure that speed because there's no point of reference; we can only measure the relative speeds of the other galaxies around us).

Speed is just relative to the notion that the Earth isn't moving, because to us, it doesn't look like it is.

Oh, here's an experiment you can do to prove that. So you're in a moving car. Don't do this while you're the driver. You toss a ball up from knee height to eye height. The ball will come right back down into your hand instead of flying backward and hitting you in the face. It has to do with the current moment of all objects involved. Since the ball has the same momentum as the car (because it did when you threw it up), it will continue to have that horizontal momentum even as you add the vertical vector of the throw. If you toss the ball up and have the driver slam on the brakes, the ball will fly forward and miss your hand. Don't try that, though. You'd have to slam fairly hard.

Now all this evolves into neat talk about ships moving at 99.999999995% light speed and what happens if you throw a baseball in the direction the ship is moving at 0.000000006% light speed.

But that gets complicated.
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Quote:
Originally Posted by nvidia2008

Due to the Earth's rotation, you see... Why don't objects above ground including the atmosphere move at a different speed to the Earth's rotation? Centrifugal force, Inertia, Gravity, Magnetism or something else?

They do move at a different speed than the Earth's rotation. Why? Heat transfer and drag.

Heat transfer makes the atmosphere create weather which moves heat from the equator towards the poles. The otherwise longitudinal flow of air gets bent by the drag against the rotating earth and slowed longitudinally because the airflow gets squeezed together as it tries to get to the poles where there are fewer miles per degree of latitude. So the winds curve and then speed up latitudinally because Bernoulli wrote a law that forces that kind of thing . Throw in some chaos theory because we cannot precisely measure, store and compute the effect of every component of drag and heat transfer and we get messy weather in a moving atmosphere.

The helo, of which I am a pilot, measures it's movement relative to the local airmass because that's what has drag on the helicopter and the helicopters rotors "push" against*. So a helo with no airspeed will have a groundspeed that matches the movement of the airmass over the ground with small lags for inertia as the airflow makes directional changes.

All that makes for some very fast winds at altitude away from the Earths surface drag. Helo's generally don't ever feel that though because helo pilots know things will soon go badly in the mass of 40 thousand moving parts or so. So we generally don't like to fly any higher than we would prefer to fall. And even that doesn't make much sense, but we like to say it. Really the altitude just magnifies the fact that helicopters are ridiculously inefficient flying machines and you can only get so high before you run out of lift.

*(Lift also has a drag component, although lift isn't all about drag and it really pulls, but downwash is directly proportional to lift so push works as an intuitive explanation at a non-pilot level)
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Originally Posted by Tallest Skil

Now all this evolves into neat talk about ships moving at 99.999999995% light speed and what happens if you throw a baseball in the direction the ship is moving at 0.000000006% light speed.

But that gets complicated.

Naw. Only if you ignore time and how the town hall clock looks as watch it out the back window flying away.

Once I heard that thought experiment Einstein used to sort out a large part of the framework for General Relativity the speed limit and running/throwing on a train problem went right away because then it makes sense. I won't try to explain it, I won't do it justice, I'll just recommend finding the description of it for those interested.
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Originally Posted by Hiro

They do move at a different speed than the Earth's rotation. Why? Heat transfer and drag.

Absolutely right; I just ignored that because the difference is almost indistinguishable.

Here's an example where it wouldn't be, though:

Designers of the Space Elevator (a tether from Earth to the Clarke orbit) have to take into account this drag and build an elevator car that can handle the difference in angle from the ground to the station at geo. Projections assume that the Elevator will be up to an entire degree off of vertical due to drag.

Which adds up over 36,000 kilometers.
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Great answers everyone! Cheers. Some intelligentsia describe this brain satisfaction as some kind of pseudo-orgasm for some folks.
Quote:
Originally Posted by Tallest Skil

Designers of the Space Elevator (a tether from Earth to the Clarke orbit) have to take into account this drag and build an elevator car that can handle the difference in angle from the ground to the station at geo. Projections assume that the Elevator will be up to an entire degree off of vertical due to drag.

Which adds up over 36,000 kilometers.

The gravity experienced at x distance from the earth has been playing on my mind for some time, also because I probably always took "microgravity" (free fall) for granted.

Finally found a good chart:

Space Odyssey 3001 talked a lot about your beloved space elevator/tower and how a certain "lost and found" astronaut could not ever live on the lower levels. (Don't want to reveal any spoilers in case anyone hasn't read it yet.. I didn't think it was a good book though \)

As per the chart, the g is surprisingly low at geostationary altitude.
Quote:
Originally Posted by nvidia2008

Finally found a good chart:

Indeed you did.

Quote:
I didn't think it was a good book though.

Why's that? [NAME REDACTED]'s recovery from the depths too implausible? Or just how it was written differently than the others?

Tom Hanks wanted to do a movie of 3001 for a while. He was kicking it around at the beginning of the last decade, if I remember correctly. They never did it, but they should, particularly now when the CG is possible to make it look good.

But obviously we need 2061 first.
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Quote:
Originally Posted by Tallest Skil

Why's that? [NAME REDACTED]'s recovery from the depths too implausible? Or just how it was written differently than the others?

Tom Hanks wanted to do a movie of 3001 for a while. He was kicking it around at the beginning of the last decade, if I remember correctly. They never did it, but they should, particularly now when the CG is possible to make it look good.

But obviously we need 2061 first.

The writing and concepts. It threw away a lot of the mystery and magnificence of the previous books/films... See:
http://www.amazon.com/3001-Odyssey-A...owViewpoints=1
Quote:
Originally Posted by nvidia2008

The writing and concepts. It threw away a lot of the mystery and magnificence of the previous books/films... See:
http://www.amazon.com/3001-Odyssey-A...owViewpoints=1

I ought to reread it again, then. I first read it when I was eight (perfectly standard reading level for me then) and again when I was fourteen. All I remember is the awesome "guy from today gets shoved into the world a thousand years from now and he's coping while the then-natives are gushing over him and their living anachronism" storyline, I suppose.

Oh, and the fact that there's a freaking tower to Geo.

<------That (obviously) stuck in my mind.
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Originally Posted by Tallest Skil

Oh, and the fact that there's a freaking tower to Geo.
<------That (obviously) stuck in my mind.

Yes, we're well aware of that.

Fountains of Paradise was quite amazing for me. I think I read it... 15 years ago?

Songs of Distant Earth is my favourite.

But nothing compares to 10 years ago when I went through the whole Dune series. (Original only, none of this posthumous stuff).
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