Has anyone seen this going across recently? Amazing sight, tonight you could also see the supply craft a few seconds behind it. Amazing to think it's flying past at over 17,000 MPH!

If anyone is interested search #ISS on Twitter for more information.

Saw it for about 45 seconds last night.

Serious question . Is it actually moving at 17k mph ? Or is it stationary (ish) and the 17k mph is just in relation to the rotation of Earth

To get into orbit it (or its pieces) needed to attain escape velocity and it retains that movement now. If it didn't it would crash to earth (unless it were in a geo-stationary orbit). I mean, this is the simple answer - but all movement in the universe is relative. Entire books have been written on this very complex question.

Is that a yes? Or a no?

Neither and both.

Galileo was the first to suggest that universe doesn’t care if you are moving or not. He noticed that he got the same results to his experiments if he were stationary or moving at a constant speed (impressive as he was on a boat, the sea must have been very calm). It was common knowledge at the time two people observing an object in motion would disagree on the object’s speed if one of them was moving. Galileo cast doubt on which one of them would be correct. It becomes very difficult to answer the question of how fast an object is moving if you do not have a reference frame in which we can measure all objects speeds. This reference frame is referred to as the absolute reference frame. Such a reference frame requires the very fabric of the universe to be full of a substance called luminiferous aether through which all objects move in time, and therefore the speed of any object could be obtained.

In 18887 Albert Michelson and Edward Morley performed a famous experiment which showed the absence of luminiferous aether. There is no absolute frame of reference. The result proves that there is no difference between an object being stationary and moving at a constant speed. Any object that is not accelerating (physicist called this an inertial frame of reference) no matter how fast it is moving is actually stationary. You can only quote a speed relative to another frame of reference, and therefore you can pretty much quote any value you wish and you will find a frame where this value holds true. Added to this, all inertial frames are equal in this theory, and the universe can’t tell the difference. Einstein used the Michelson Morley result in his paper "Zur Elektrodynamik bewegter Körper" ("On the Electrodynamics of Moving Bodies"), better known as special relativity. The year was 1905, his Annus Mirabilis.

If you have ever tried to dink a cup of tea in a moving car you will notice that when the car is not accelerating it’s easy. This reminds me of trying to do my homework on the bus on the way to school, bloody thing kept starting and stopping, it was nearly impossible. On an airplane it’s easy to do pretty much anything (space permitting), my three year old daughter on a recent flight to Lanzarote looked out of the window at the clouds below and said ‘Daddy we’re not moving’ I didn’t take the time to explain to her that she was indeed correct.

Most of the time all of this is meaningless because we live on a massive planet that will always try to return us to the same speed as it. Or more correctly, to zero miles per hour relative to the point on the surface that we are. When we quote the speed of an object it tends to be relative to the surface of the Earth. For all situations in most people’s lives the Earth is the absolute reference frame. Although most would be aware that the measurement of a year uses the Sun as its absolute reference frame. It is the inability to mentally let go of the surface as a frame of reference that make the ideas so alien.

17,000 mph? I suspect, but don’t know, that this figure is arrived at by taking the Centre of the Earth as the Centre of the space station’s orbit, calculating the circumference and then dividing it by period of the orbit. Interestingly if you do the same for a person on the surface of the Earth, the speed varies from 1000 mph at the equator to zero at the poles. As I mentioned earlier most of the time we would measure speeds relative to ourselves being stationary. This makes no sense for a satellite as the shape of its orbit would be incredibly complicated and its speed would be constantly changing.

Simple! Except none of the frames of reference mentioned are inertial fames.

Could only happen in The Sin Bin .

So . To simplify .
Is it actually flying at 17k mph around Earth ? Yes or no .

If Earth stopped rotating would the thing in space continue zooming around in orbit ? Yes or no .

Or ... Would it be stationary above one place ? Yes or no .

Its tied by a very fine but very strong and very long fishing twine tethered to a railing outside the offices of Lockheed Martin in Maryland, occasionally people forget when they want to use the railing to tie bedsheets with "Happy 40th Chuck" written in felt tip, and they'll accidently release said satellite twine which result in it soaring off into space never to be seen again, such satellites being filled with helium - its at those times when one or more Sky channels tend to disappear to be replaced a few weeks later by ones that are more shit simply because they've had to buy space on someone else's satellite.

It's clearly not in geostationary orbit and its use would be limited if it was.

If you were on it you'd be doing the above speed.
Relative speed to something else may be different.
Relative to the centre of the Earth it would be doing 17,227 miles per hour.
The Earths surface is itself moving at around 1,000 miles per hour relative to it's centre.

Spot on again Mr Field. Professor Brian Cox must be quaking in his boots!