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mopc
2004-Aug-19, 05:24 PM
The earth revolves around the sun, the sun, around the Milky Way's core, and the milky way strays from neighboring galaxies.

Counting all that, at what speed is a person standing on the surface of the earth?

Squink
2004-Aug-19, 05:36 PM
The Cosmic Microwave Background (http://zebu.uoregon.edu/~js/glossary/cosmic_microwave_background.html) provides a good reference for the earth's overall motion through space:
Precise measurements made by the Cosmic Background Explorer (COBE) satellite launched in late 1989 determined the spectrum to be exactly characteristic of a blackbody at 2.735 K. The velocity of the satellite about the Earth, the Earth about the Sun, the Sun about the Galaxy, and the Galaxy through the universe actually makes the temperature seem slightly hotter (by about one part in 1,000) in the direction of motion rather than away from it. The magnitude of this effect--the so-called dipole anisotropy--allows astronomers to determine that the Local Group of galaxies is moving at a speed of about 600 km/sec in a direction that is 45 from the direction of the Virgo cluster of galaxies.

Glom
2004-Aug-19, 05:39 PM
Blasphemy! [-X

dvb
2004-Aug-19, 07:14 PM
ain't it all relative? :lol:

dvb
2004-Aug-20, 12:56 AM
ain't it all relative? :lol:

Well isn't it? :-?

The Supreme Canuck
2004-Aug-20, 01:08 AM
Yep. Everything is. The quote, though, seems to indicate that it means relative to the Virgo galactic cluster:


*snip* allows astronomers to determine that the Local Group of galaxies is moving at a speed of about 600 km/sec in a direction that is 45 from the direction of the Virgo cluster of galaxies.

Don't quite know what the 45 means. 45 degrees, maybe?

Squink
2004-Aug-20, 02:22 AM
Don't quite know what the 45 means. 45 degrees, maybe?I think that's it. This PDF (http://arxiv.org/pdf/hep-ph/9209209) goes into more detail and uses the phrase "at an angle of 45 away from the direction of the Virgo cluster."
The CMB isn't a universal frame of reference, but it's pretty good for sorting out the motions of things that lie within a few billion lightyears of earth.

The Supreme Canuck
2004-Aug-20, 02:27 AM
Got it, thanks. Neat method, that.

John Kierein
2004-Aug-20, 01:49 PM
Don't quite know what the 45 means. 45 degrees, maybe?I think that's it. This PDF (http://arxiv.org/pdf/hep-ph/9209209) goes into more detail and uses the phrase "at an angle of 45 away from the direction of the Virgo cluster."
The CMB isn't a universal frame of reference, but it's pretty good for sorting out the motions of things that lie within a few billion lightyears of earth.

Actually, according to my "gravity is a push of long wavelength radiation" theory, the CMBR IS the universal frame of reference for Mach's Principle. But this should go on the against the mainstream page.

mopc
2004-Aug-20, 08:36 PM
so lemme see if i got that strainght:


we're traveling at 600km/sec (that's 2,160,000km/h) towards one of the eliptic constellations... +45 degrees....wait a sec (woops there goes 600km :) ) 45 degrees which way? Why dont they mention the constellation that's "45 degrees" from Virgo?? but the direction of Virgo is changing all year around. Hmm I get it... w're spinning but the "constellations" are there.

But the sun spins around the galaxy core in one direction, our galaxy probably floats about toward another direction! Ok, maybe the spinnig of the sun is irrelevant in relation to our galaxy's motion. But 600 km/s in relation to what? To the "Virgo galactic cluster"? What if it's virgo cluster that's moving towards us and the scorpion cluster is moving even faster towards us, but all other galaxies are fleeing from us twice the speed?

I mean, is EVERY galaxy distancing itself from EVREY OTHER galaxy or are there random movements?
And how can they know if all we can see happened millions of years ago?

Squink
2004-Aug-20, 09:38 PM
so lemme see if i got that strainght:Here's a picture of the CMB dipole (http://antwrp.gsfc.nasa.gov/apod/ap010128.html) The 600 KPS figure is relative to the microwave background radiation.

russ_watters
2004-Aug-22, 09:02 PM
I mean, is EVERY galaxy distancing itself from EVREY OTHER galaxy or are there random movements?
And how can they know if all we can see happened millions of years ago? Except for small clumps moving together, yes, every galaxy is moving away from every other galaxy.