Speeds and Motion

[jamesabrown]

I'm writing an article on the various speeds we experience as we travel through space, and I'm hoping the fine members of this board can check my math.

I've already addressed that speed and velocity are tricky in a relative universe, so for simplicity I'm making my measurements compared to either background stars or the Cosmic Microwave Background. My numbers are:

Rotation of the Earth: 0465 kilometers per second (at equator)
Orbit of Earth around Sun: 30 kps
Sun's motion (relative to nearby stars): 20 kps
Orbit of Sun around galactic center: 220 kps
Galaxy orbit around common center with other galaxies (with respect to CMB): 550 kps

Total: ~820 kilometers per second.

Thanks!

[PraedSt]

Those numbers may be right, but you're not thinking of adding those vectors are you?

[Argos]

Right now, sitting on my chair, I´m experiencing zero speed.

[astromark]

Quote from -jamesabrown-
"Rotation of the Earth: 0465 kilometers per second (at equator)
Orbit of Earth around Sun: 30 kps
Sun's motion (relative to nearby stars): 20 kps
Orbit of Sun around galactic center: 220 kps
Galaxy orbit around common center with other galaxies (with respect to CMB): 550 kps"

I feel your grasp of this is flawed... We do not experience rotational velocity ie: you are not lighter because of Earths rotational velocity. It does play a role in orbital velocities when launching from west to east or not. When noting the velocity against the motion of near by stars and then the orbital velocity about the galactic center. They are all moving... the best you can do is guess. The movement of the Galaxy in relation to what? the near by cluster or the CMB. Again just a average guess., and none of it matters at all. We have been to the moon. That ' One small step' was just that. So fraught with risk and cost that we have not done it since.
So if you just want to know the relative velocities of Earth in the systems you mention then just go check with 'Wickie' your numbers are as right as they need to be. The movement over the distances are so small that a more accurate picture is not available. From year to year the night sky map does not change as you would think it should. Its all so far, far away that movement is almost not perceivable.

[PraedSt]

Right now, sitting on my chair, I´m experiencing zero speed.

But you're thinking Felipe Massa.

Back to OP (who seems to have disappeared)...if you're thinking of adding those velocities, you have to do some adjusting. They all occur on different planes, so you have to pick one as your base, and do some trig on the rest.

[Argos]

But you're thinking Felipe Massa.

Oh, poor boy.

[jamesabrown]

Quote from -jamesabrown-
"Rotation of the Earth: 0465 kilometers per second (at equator)
Orbit of Earth around Sun: 30 kps
Sun's motion (relative to nearby stars): 20 kps
Orbit of Sun around galactic center: 220 kps
Galaxy orbit around common center with other galaxies (with respect to CMB): 550 kps"

I feel your grasp of this is flawed... We do not experience rotational velocity ie: you are not lighter because of Earths rotational velocity. It does play a role in orbital velocities when launching from west to east or not. When noting the velocity against the motion of near by stars and then the orbital velocity about the galactic center. They are all moving... the best you can do is guess. The movement of the Galaxy in relation to what? the near by cluster or the CMB. Again just a average guess., and none of it matters at all. We have been to the moon. That ' One small step' was just that. So fraught with risk and cost that we have not done it since.
So if you just want to know the relative velocities of Earth in the systems you mention then just go check with 'Wickie' your numbers are as right as they need to be. The movement over the distances are so small that a more accurate picture is not available. From year to year the night sky map does not change as you would think it should. Its all so far, far away that movement is almost not perceivable.

Wow, I'm not sure I'm following you. If I'm standing on the Earth's equator, am I not moving as fast as the earth's equator?

I specified what I'm comparing to, such as the sun's movement compared to nearby stars, and the galaxy's movement against the CMB.

I don't understand your reference to having been to the moon. Was that an aside?

I have wiki'd the numbers, but it also involved lots of conversions (m/s to kph, etc.) and since I'm intending this for public consumption I really want to make sure I've got my numbers right.

Again, I don't understand your reference to perceiving our motion compared to the night sky. This was just an interesting exercise demonstrating how, despite all appearances, we are moving quickly through the universe. Of course, that's quickly compared to ordinary human movements, but not so quick compared to astronomical distances. But our intuition would tell us that we're not moving at all.

[jamesabrown]

But you're thinking Felipe Massa.

Back to OP (who seems to have disappeared)...if you're thinking of adding those velocities, you have to do some adjusting. They all occur on different planes, so you have to pick one as your base, and do some trig on the rest.

Ugh, I can guarantee I'm not doing any trig (never had it in school). Okay, I see your point about the different vectors. If I'm walking at three miles an hour toward the back of a ship traveling twenty-five miles an hour, it would be incorrect to say that my position is changing by twenty-eight miles an hour.

I'm not sure how I would finish this article then. I originally wrote it to summarize all the different ways we are moving with a grand finale ("By the time you've read this, you've traveled a total of XXX kilometers. Hope you buckled your seatbelt!") But sure, add all the vectors and our planet may be stationary relative to the CMB. That's no fun.

[PraedSt]

Never had trig at school

You can still have a grand finale. Just use the speed around our galactic centre and stop there. If you look at your figures, you'll see that it's much, much larger than our rotation speed, or our orbital speed. Finding out that you've travelled several thousand kilometres around a black hole while reading an article is a nice finale.

[NEOWatcher]

Ugh, I can guarantee I'm not doing any trig (never had it in school). Okay, I see your point about the different vectors...

I think that was the main point...you can't add the numbers.

My minor nitpick was that the movement to local stars is made irrelevent when considering movement relative to the galaxy.

Anyway, to close it, how about something relating how the reader's experiences in traveling in relation to the surface is nothing compared to each and every number you gave?

[jamesabrown]

Never had trig at school

You can still have a grand finale. Just use the speed around our galactic centre and stop there. If you look at your figures, you'll see that it's much, much larger than our rotation speed, or our orbital speed. Finding out that you've travelled several thousand kilometres around a black hole while reading an article is a nice finale.

But the speed of the galaxy's motion is much, much faster than it's rotation, right? Shouldn't that count for something? I picture an ant hanging on for dear life on one arm of a pinwheel that's circling, and the pinwheel is in the hand of a boy running for all he's worth. Sure, the ant's speed relative to the ground will go up and down slightly as the pinwheel arm first moves forward and backward around it's central point, but overall the ant's motion is blistering, particularly from the ant's normal point of view.

Perhaps I can just close the article with the galaxy's speed (550 kph), acknowledging that all the other forms of motion are swallowed up by the much larger motion of the galaxy itself (plus vectors cancelling each other out, etc.) 550 kph is still awfully fast.

[jamesabrown]

I think that was the main point...you can't add the numbers.

My minor nitpick was that the movement to local stars is made irrelevent when considering movement relative to the galaxy.

In my article, only the sun's motion is compared to local stars. The galaxy's motion is compared to the Cosmic Microwave Background. Or am I just confused?

Anyway, to close it, how about something relating how the reader's experiences in traveling in relation to the surface is nothing compared to each and every number you gave?

I already do that at the end of each form of motion--Earth's rotation, Earth's orbital velocity, Sun's velocity, etc. Now to tie up the whole article with a bow somehow. I think I'll go with PraedSt's idea.

I knew it was a good idea to ask this board for advice.

[mugaliens]

Right now, sitting on my chair, I´m experiencing zero speed.

Exactly. And I am experiencing a 1 G upwards acceleration imparted to me by my chair.

[Robert Tulip]

But the speed of the galaxy's motion is much, much faster than it's rotation, right? Shouldn't that count for something? I picture an ant hanging on for dear life on one arm of a pinwheel that's circling, and the pinwheel is in the hand of a boy running for all he's worth. Sure, the ant's speed relative to the ground will go up and down slightly as the pinwheel arm first moves forward and backward around it's central point, but overall the ant's motion is blistering, particularly from the ant's normal point of view.Perhaps I can just close the article with the galaxy's speed (550 kph), acknowledging that all the other forms of motion are swallowed up by the much larger motion of the galaxy itself (plus vectors cancelling each other out, etc.) 550 kph is still awfully fast.

That was KPS in your first list. And the 220 KPS galactic orbit speed would either add to this speed or reduce it, depending on the angle of the galactic movement vector to the galactic plane. With all the other factors it could mean our pace varies between about 300 and 800 KPS over the course of the 240 million year galactic rotation, if the galaxy is moving side-on, but sticks at a steady 550 KPS if the galaxy is moving straight up or down. RT

[jamesabrown]

That was KPS in your first list. And the 220 KPS galactic orbit speed would either add to this speed or reduce it, depending on the angle of the galactic movement vector to the galactic plane. With all the other factors it could mean our pace varies between about 300 and 800 KPS over the course of the 240 million year galactic rotation, if the galaxy is moving side-on, but sticks at a steady 550 KPS if the galaxy is moving straight up or down. RT

You are correct; thanks for the catch.

On the other hand, the 220 kps was in reference to the galaxy's rotation, not its orbital speed, so we're even.

[Gigabyte]

I've been wanting to create an animation about these very things. Relative velocities and points of view, in regards to "motion" for somebody standing still on the surface of the earth. But never got a solid answer on what these velocities actually were.

So those figures are all correct?

[PraedSt]

I think so. Haven't checked to be honest.

But you'd have to be careful with all the angles. Those figures are all speeds really.

[Gigabyte]

Using software, the "angles" will be generated by the animation. I just need accurate figures, especially relative to "stationary" points somewhere, to place the camera.

[Gigabyte]

OK I guess I don't really need accurate numbers, but if I am going to show it to anybody who actually knows the right figures, I better have them. Or I will never hear the end of it.

[PraedSt]

I'll check them for you. The list above keeps changing the 'stationary point'. I suppose your software can use multiple cameras and then join everything up?

[Gigabyte]

Yes, the animation can be either from imaginary points, or from the stationary observer. It would be interesting to do both.

Picking the points is the really hard part. There is no such thing as a stationary point.

[Jeff Root]

James,

The info is undoubtedly also on the Internet, but if you can, look up this
article in the May, 1978 issue of Scientific American magazine: 'The Cosmic
Background Radiation and the New Aether Drift' by Richard A. Muller.
It has diagrams that may help you.

-- Jeff, in Minneapolis

[astromark]

I will try to clear my mumblings for 'Jamesabrown' I see the confusion as just my inept linguistic skills. Sorry. When I mentioned the lunar landing it was only because that is as far as we have been. When we are talking of Galaxy velocities it seems sort of pointless. Interesting and worthy of some study.
As has now been well said, Nothing in this universe can be correctly described as still or, motionless. So calculating the relative velocities is always going to be wrong. Dependant on from where you are observing from. From here on planet Earth we see movement and can plot with some accuracy the path and relative position.
At approximately 4 am if you go out doors and look directly up. You are looking in the direction this planet is moving. When you look to wards Sagittarius and the central hub of this galaxy you can not see or even imagine the actual movement. Needless to say there is lots Not wanting to make fun of any point here , I will add that there is no up or down. Navigating across space is just a we tad complicated enough ... Never mind the fact that every thing is rushing off....

[NEOWatcher]

In my article, only the sun's motion is compared to local stars. The galaxy's motion is compared to the Cosmic Microwave Background. Or am I just confused?

I was considering movement relative to the local stars vs orbit of the sun in the galaxy. The suns movement is not dependent upon those stars (as in orbiting) although it is perterbed by them. But; by the time the overall orbit around the galaxy is considered, those perterbations cancel out.

[PraedSt]

I'm writing an article on the various speeds we experience as we travel through space, and I'm hoping the fine members of this board can check my math.

I've been wanting to create an animation about these very things. Relative velocities and points of view, in regards to "motion" for somebody standing still on the surface of the earth. But never got a solid answer on what these velocities actually were.
So those figures are all correct?

This is an excellent answer; has everything you need to know. How fast do I move through the Universe?

[Gigabyte]

Your speed with respect to the surface of the Earth. I do not know what this speed is. It is not constant, is probably usually smaller than 150 km/h (100 mph), and changes with a certain regularity but also with irregular deviations.

http://www.astro.uu.nl/~strous/AA/en...ging.html#v487

The very first "answer" doesn't fill me with surety about the accuracy of the site. What the heck does that even mean?

[Gigabyte]

OK I am going to assume, because the site doesn't explain, that this is about driving in cars or riding on trains. Which is funny, since that is the only movement that is actually true motion.

And leaves out aircraft travel.

[NEOWatcher]

The very first "answer" doesn't fill me with surety about the accuracy of the site. What the heck does that even mean?

The site can not know or predict how fast you are moving or in what direction. But; it is making the assumption that you are rarely exceeding 100kph in any direction.

In other words, there's a factor here, but it's not a uniform motion like the rest of the movements.

[Gigabyte]

You may have missed my second post on the matter. If so, you have time to edit.

[PraedSt]

OK I am going to assume, because the site doesn't explain, that this is about driving in cars or riding on trains. Which is funny, since that is the only movement that is actually true motion.

And leaves out aircraft travel.

Yes. For your animation, assume an observer that's stationary with respect to the Earth's surface. As I am right now...