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justinv3
2006-Sep-13, 03:15 AM
So we know that we are all in motion in the universe. And I know that, since we are moving, and everything around us is moving, we have to take that fact into consideration when we do any kind of calculation and observation. I think general relativity comes in handy here.

But...

Could we not measure how fast we are moving? and maybe launch a spaceship in the opposite direction enough so that we will come to a stand still in the universe? If that could happen, would everything become easy to measure? The expansion of the universe for example or the rate at which it expands? maybe?

hhEb09'1
2006-Sep-13, 05:47 AM
But...

Could we not measure how fast we are moving? The ultimate question is, relative to what? Answer that, and the measurement is usually fairly easy.

Jens
2006-Sep-13, 06:56 AM
Could we not measure how fast we are moving? and maybe launch a spaceship in the opposite direction enough so that we will come to a stand still in the universe? If that could happen, would everything become easy to measure? The expansion of the universe for example or the rate at which it expands? maybe?

First, we can't measure "how fast we are moving," since there is no absolute reference frame. People used to believe there was an "ether", but it was shown not to exist. So motion cannot be measured in the way you imagine.

So that invalidates the second question.

Then, for the third and fourth question, if one accepts the "cosmological principle", the expansion of the universe would be the same wherever you measure it from.

antoniseb
2006-Sep-13, 02:58 PM
First, we can't measure "how fast we are moving," since there is no absolute reference frame.

Actually, we can measure how fast we are moving, and what direction relative to the frame in which the Cosmic Microwave Background Radiation does not have a bipolar temperature distribution.

We do not (currently) have the capability of building a rocket that could get a probe going nearly that fast.

hhEb09'1
2006-Sep-13, 03:23 PM
Actually, we can measure how fast we are moving, and what direction relative to the frame in which the Cosmic Microwave Background Radiation does not have a bipolar temperature distribution.

We do not (currently) have the capability of building a rocket that could get a probe going nearly that fast.Actually? That is still not assured to be an absolute reference frame.

antoniseb
2006-Sep-13, 05:20 PM
That is still not assured to be an absolute reference frame.

I didn't claim it to be absolute, and the OP didn't say they were looking for absolute. The OP was about looking for a reference frame that required less work subtracting the effects of ou peculiar movement. I specifically named a frame of reference in which the probe would not be considered to be moving.

Squink
2006-Sep-13, 09:20 PM
Here's A lovely Image of the Cosmic Microwave Background Dipole (http://apod.nasa.gov/apod/ap010128.html)
Our local group of galaxies is moving at about 600 kilometers per second relative to the CMB.

hhEb09'1
2006-Sep-14, 01:11 AM
I didn't claim it to be absolute, and the OP didn't say they were looking for absolute. Sorry, I thought you were responding to Jens's post.

antoniseb
2006-Sep-14, 12:31 PM
Sorry, I thought you were responding to Jens's post.

I was, but if you read my brief post entirely you'd have seen the phrase:

...relative to the frame in which...

I didn't read Jens as using the phrase absolute reference frame either. Those were your words needlessly injected into Jens request.

hhEb09'1
2006-Sep-14, 01:30 PM
I didn't read Jens as using the phrase absolute reference frame either. Those were your words needlessly injected into Jens request.I was confused by this response at first, until I noticed that Jens did not make a request. Are you confusing Jens with the OP justinv3?

Jens did use the phrase, in their only post to this thread.

antoniseb
2006-Sep-14, 01:41 PM
Are you confusing Jens with the OP justinv3?

Yes, that is correct.

publiusr
2006-Oct-06, 06:32 PM
This is a good idea for a sci-fi story.

Sir--we nulled out our planets rotation around the sun, stopped outside the galaxy--and now we've dropped out of the universe altogether.

Huh?