Please log in or register. Registered visitors get fewer ads.
Forum index | Previous Thread | Next thread
International Space Station fans 20:02 - Mar 28 with 1498 viewsBrixtonBlue

It went over at 5 to 7 tonight and will be back round again in half an hour (8.31).

Amazes me it's that quick at going round the entire planet. 17,130 mph! How many astronauts on it at the moment? They must be the safest humans right now!

Anyone with telescopes or binoculars had a look? Can you see the shape of it rather than just a bright star?

Love space, me.

Poll: If you work in an office, when are you off over Christmas (not booked holiday)?

2
International Space Station fans on 21:23 - Mar 30 with 254 viewsNewcyBlue

International Space Station fans on 20:58 - Mar 30 by Nthsuffolkblue

Not a whoosh. Try Einstein's theory of relativity instead.

Are we stationary or are we circling the Sun at so many million mile per hour? Are we stationary or spinning around at whatever it is miles per hour?


“ Are we stationary or spinning around at whatever it is miles per hour?”

At the equator the earth spins at 1037.9mph. At say, 50° of latitude it is less, you can work it out by the cosine of the latitude. So 667.15mph.

Poll: So, which of the season ending votes do we think will win?

0
International Space Station fans on 21:37 - Mar 30 with 243 viewsNthsuffolkblue

International Space Station fans on 21:23 - Mar 30 by NewcyBlue

“ Are we stationary or spinning around at whatever it is miles per hour?”

At the equator the earth spins at 1037.9mph. At say, 50° of latitude it is less, you can work it out by the cosine of the latitude. So 667.15mph.


You are right … as long as you take the centre of the Earth as your fixed point. Then you are travelling faster the closer to the equator you are.

However, why does it not feel like we are travelling at that speed? Because everything else around us is travelling at the same speed.

Take an example of a train. If you look outside and see another train on the adjoining track is it moving? If it appears stationary it may be because it is moving at the speed as you. If it appears to be moving backwards it could be because you are moving faster or moving and it is stationary or it could even be moving backwards. Now changing the fixed point to the Earth instead of you on your train changes how each motion is perceived.

Without fixing a certain point in the Universe and comparing everything to that, all speed is relative. The fixed point we usually choose is ourselves, or the centre of the Earth, or the Sun depending on what we are discussing.

This is my (possibly simplistic) understanding of Einstein's theory of relativity.

Take another example. When you look overboard on your ship and you see the water moving does it necessarily tell you which way you are travelling and how fast or would you go by your instruments and maybe the stars/Sun instead?

Poll: Should there be a second referendum?
Blog: [Blog] Ghostbusters

0
International Space Station fans on 21:42 - Mar 30 with 241 viewsNthsuffolkblue

International Space Station fans on 21:15 - Mar 30 by BrixtonBlue

Yes, we're moving. But so is the ISS. I gave you a link to it.


Your link begins to explain the difference between geostationary and other types of orbits.

I was actually referencing relativity instead.

Sorry for any confusion. I was trying to be a bit clever.

Poll: Should there be a second referendum?
Blog: [Blog] Ghostbusters

1
International Space Station fans on 21:51 - Mar 30 with 232 viewsNewcyBlue

International Space Station fans on 21:37 - Mar 30 by Nthsuffolkblue

You are right … as long as you take the centre of the Earth as your fixed point. Then you are travelling faster the closer to the equator you are.

However, why does it not feel like we are travelling at that speed? Because everything else around us is travelling at the same speed.

Take an example of a train. If you look outside and see another train on the adjoining track is it moving? If it appears stationary it may be because it is moving at the speed as you. If it appears to be moving backwards it could be because you are moving faster or moving and it is stationary or it could even be moving backwards. Now changing the fixed point to the Earth instead of you on your train changes how each motion is perceived.

Without fixing a certain point in the Universe and comparing everything to that, all speed is relative. The fixed point we usually choose is ourselves, or the centre of the Earth, or the Sun depending on what we are discussing.

This is my (possibly simplistic) understanding of Einstein's theory of relativity.

Take another example. When you look overboard on your ship and you see the water moving does it necessarily tell you which way you are travelling and how fast or would you go by your instruments and maybe the stars/Sun instead?


You can’t tell the speed just by looking overboard or at the celestial bodies.

You can get an indication of speed from looking overboard, but that’s only when you know how the ship behaves.

Otherwise it’s all from the instruments. We measure speed through the water, normally a Doppler log, and speed over ground. SOG is usually measured using GPS (corrected using SBAS). Sometimes our Doppler log will measure bottom track and we can get speed over ground that way too.

A professional seafarer keeps the radar in speed through the water, the only way to correctly apply collision regulations.

Relativity has a lot to do with the marine environment, especially radar.

We use a fixed point in the celestial sphere, Aries, and calculate everything relative to that. Nautical Almanacs have the Greenwich hour angle for Aries, Moon, Sun, and certain planets.

Stars are in with sidereal hour angles. Relative to Aries.

I think that relativity goes beyond practical application.

Poll: So, which of the season ending votes do we think will win?

2
International Space Station fans on 23:16 - Mar 30 with 214 viewsRyorry

International Space Station fans on 21:51 - Mar 30 by NewcyBlue

You can’t tell the speed just by looking overboard or at the celestial bodies.

You can get an indication of speed from looking overboard, but that’s only when you know how the ship behaves.

Otherwise it’s all from the instruments. We measure speed through the water, normally a Doppler log, and speed over ground. SOG is usually measured using GPS (corrected using SBAS). Sometimes our Doppler log will measure bottom track and we can get speed over ground that way too.

A professional seafarer keeps the radar in speed through the water, the only way to correctly apply collision regulations.

Relativity has a lot to do with the marine environment, especially radar.

We use a fixed point in the celestial sphere, Aries, and calculate everything relative to that. Nautical Almanacs have the Greenwich hour angle for Aries, Moon, Sun, and certain planets.

Stars are in with sidereal hour angles. Relative to Aries.

I think that relativity goes beyond practical application.


Interesting stuff, thanks Newcy :)

Poll: Wd there be so many posts on pees/poos/urinals etc if we were still tabletoppers

0
International Space Station fans on 11:32 - Mar 31 with 163 viewsBrixtonBlue

International Space Station fans on 21:42 - Mar 30 by Nthsuffolkblue

Your link begins to explain the difference between geostationary and other types of orbits.

I was actually referencing relativity instead.

Sorry for any confusion. I was trying to be a bit clever.


Hmm. Well you said, "It is not moving at 17,130 mph. It is stationary while we are moving at that speed." Both parts of that second sentence are wrong. The Earth spins at around 1,000mph.

Poll: If you work in an office, when are you off over Christmas (not booked holiday)?

0
International Space Station fans on 11:35 - Mar 31 with 162 viewsNewcyBlue

International Space Station fans on 11:32 - Mar 31 by BrixtonBlue

Hmm. Well you said, "It is not moving at 17,130 mph. It is stationary while we are moving at that speed." Both parts of that second sentence are wrong. The Earth spins at around 1,000mph.


1037.9mph at the equator.

Poll: So, which of the season ending votes do we think will win?

0
International Space Station fans on 11:54 - Mar 31 with 141 viewsBrixtonBlue

International Space Station fans on 11:35 - Mar 31 by NewcyBlue

1037.9mph at the equator.


I did say "around."

Poll: If you work in an office, when are you off over Christmas (not booked holiday)?

0
Login to get fewer ads

International Space Station fans on 11:58 - Mar 31 with 138 viewsNewcyBlue

International Space Station fans on 11:54 - Mar 31 by BrixtonBlue

I did say "around."


Oblique spheroid.

Poll: So, which of the season ending votes do we think will win?

1
International Space Station fans on 14:03 - Mar 31 with 119 viewsEwan_Oozami

International Space Station fans on 11:35 - Mar 31 by NewcyBlue

1037.9mph at the equator.


Anything, eg, a spherical object, spinning around an internal axis does not have a collective speed/velocity measurable in mph, or m/s as such, because as people have said, that depends on where you are on the object. You measure angular velocity (usually in radians per second, or RPM), which is a vector.

Knowing the radius of the object (r) and it's angular velocity (AV), you can calculate the velocity (V) at any point on the surface using the formula:

V = cos(a) x AV x r

where a is effectively the angle of latitude.

Now if that spinning spherical object is orbiting another spherical object, the actual velocity is a combination of the velocities arising from the spinning of the object and the orbiting of the spinning object itself around the other spinning object.

So, in the case of the Earth around the Sun, at equivalent latitudes the side of the Earth facing the Sun is travelling slower relative to the Sun, than the side facing away from it - even though they are travelling at same speeds relative to the centre of the Earth.

The ultimate example of this is the Moon, which, due to the gravitational pull of the Earth, has had its rotational period around its own axis, synchronised to its rotational period around the Earth. Hence relative to the Earth, the Moon does not appear to rotate, but the side facing us is still travelling a lower velocity (relative to the Earth), than the side facing away from us.

You can tell I'm a bit bored today..

Am viewing TWTD in Table Mode on this browser so apologies if replying to a completely different post to the one I intended.
Poll: How do you view the TWTD forum?

0
International Space Station fans on 14:09 - Mar 31 with 116 viewsRadlett_blue

International Space Station fans on 20:58 - Mar 30 by Nthsuffolkblue

Not a whoosh. Try Einstein's theory of relativity instead.

Are we stationary or are we circling the Sun at so many million mile per hour? Are we stationary or spinning around at whatever it is miles per hour?


"Einstein can't be classed as witless.
He claimed atoms were the littlest."
Ian Dury.
0
International Space Station fans on 14:19 - Mar 31 with 112 viewsNewcyBlue

International Space Station fans on 14:03 - Mar 31 by Ewan_Oozami

Anything, eg, a spherical object, spinning around an internal axis does not have a collective speed/velocity measurable in mph, or m/s as such, because as people have said, that depends on where you are on the object. You measure angular velocity (usually in radians per second, or RPM), which is a vector.

Knowing the radius of the object (r) and it's angular velocity (AV), you can calculate the velocity (V) at any point on the surface using the formula:

V = cos(a) x AV x r

where a is effectively the angle of latitude.

Now if that spinning spherical object is orbiting another spherical object, the actual velocity is a combination of the velocities arising from the spinning of the object and the orbiting of the spinning object itself around the other spinning object.

So, in the case of the Earth around the Sun, at equivalent latitudes the side of the Earth facing the Sun is travelling slower relative to the Sun, than the side facing away from it - even though they are travelling at same speeds relative to the centre of the Earth.

The ultimate example of this is the Moon, which, due to the gravitational pull of the Earth, has had its rotational period around its own axis, synchronised to its rotational period around the Earth. Hence relative to the Earth, the Moon does not appear to rotate, but the side facing us is still travelling a lower velocity (relative to the Earth), than the side facing away from us.

You can tell I'm a bit bored today..


We did speeds for different latitudes earlier on in the thread.

Poll: So, which of the season ending votes do we think will win?

0
International Space Station fans on 14:28 - Mar 31 with 109 viewsEwan_Oozami

International Space Station fans on 14:19 - Mar 31 by NewcyBlue

We did speeds for different latitudes earlier on in the thread.


Ah yes, that's true! But I wanted to (in a roundabout way) get the Moon in there somewhere, because in the "are we moving/stationary, if so, how fast?" debate, that is an interesting example! :-)

Am viewing TWTD in Table Mode on this browser so apologies if replying to a completely different post to the one I intended.
Poll: How do you view the TWTD forum?

0

Please log in or register. Registered visitors get fewer ads.
About Us Contact Us Terms & Conditions Privacy Cookies Advertising
© TWTD 1995-2020