Hi Guys, someone asked me this, HELP!!!!

[AstroTiger]

Hi Al

Thanks for giving me the opportunity to send a question. I realise this might not be a typical astronomy question, like where do I look for Venus, but if it was an easy question I would have probably found the answer by now on the web. Here goes:

We (the sun) are moving though the cosmic microwave background at a certain speed and direction, which is why the COBE CMB maps have an initial dipole before they are adjusted to compensate for this movement:

http://astsun.astro.virginia.edu/~jh...chapter14.html

Somebody on the web has asked what is the direction and speed of this movement:

"Q: What is the magnitude of our motion relative to the CMB (RA, Decl, km/s)?

A: The best number comes from analysis of data from the COBE satellite, and I will just quote those numbers. We are moving at a velocity of 370.6 +/- 0.4 km/s towards galactic coordinates (l,=(264.31+/-0.17,48.05+/-0.10). which corresponds to RA=11h12m, Dec=-7.2.

These numbers are specifically for the motion of the Sun relative to the CMB. Of course the Earth is in motion around the Sun, and so there is an annual variation in the Earth's motion relative to the background. In fact COBE was sensitive enough that it could detect the motion of the Earth by the changing temperature pattern in the sky throughout the year!"

(http://www.astro.ubc.ca/people/scott/faq_email.html)

I haven't a clue what that direction answer means.

I was just wondering whether somebody could give me a direction answer in non-astronomer laymans terms, e.g. as it relates to the earth at say midnight new years eve, i.e. what part of the earth in terms of longitude and latitude could you stand at, look directly up, and be pointing in that direction. Hopefully then I could get an appreciation of which direction I am moving though the CMB on a daily and seasonal basis, like having a good idea which direction the sun is thoughout the day and the year.

I originally got interested in CMB from this article:

http://www.astro.ubc.ca/people/scott/cmb_intro.html

I have avoided asking the guy behind the website questions though, since some of his answers seem too complicated, and I was hoping that if you talk to the general northants public about astronomy, you might be able to explain things in laymans terms.

Thanks

[Chubster]

:shock: Way over my head Im afraid but Astroman might be able to help you....sure he will be along shortly.

Welcome by the way !

[Astroman]

Well, I haven't time to read the articles now, but this news comes a s somewhat of a suprise. According to this, we are moving toward a point in northern Crater, the constellation due south of Leo's hind leg. I'd always thought we were moving toward M13. As for when to look due south at midnight and see which way we're going, that would be midnight, March 17th, (my ex-wife's birthday.)

[AstroTiger]

anyone?

[Astroman]

I didn't answer you? Guess I'll have to read the articles now...

...First link is dead...

[lunator]

AM

I agree with you about the Sun's motion. We are heading towards Hercules

I always thought that the CMB pervades space, as it is the cooled 'light' that 1st filled the universe 380,000yrs after the BB.

So I'm not sure how we can have motion relative too it?

Cheers

Ian

[Astroman]

Well, since space is expanding, we're moving away from the "origin" of the CMB, however so is everything else. The question is, can we detect which direction that is and if so, which way is it relative to things we can relate to? I kinda think not on both counts, since space is so mind-bogglingly huge.

[joelhall]

Although the CBR is uniform throughout space, I was of the understanding that there are velocity variations in different directions. Although the radiation is spread throughout space, this does not mean to say that it travels in all directions.

Surely as radiation is a wave, it would be a vector quantity, as it would have an origin point (the Big Bang), so its greater velocity would be away from the origin? This could be measured by the doppler effect, which would show us our relative velocity to the CBR. Although I haven't actually looked into this, I would imagine from the information in that answer, that we would measure a variation in red shift in opposite directions, showing that we (the Sun) are moving in the same direction, and at greater speed, and we would see the greatest blue shift in the direction we are heading.

[Kaptain Klevtsov]

But as everything started of as a singularity, everything started off in the centre by definition. So there is no middle except that everywhere is the middle. Strange stuff this.

Captain Chaos

[joelhall]

But as the singularity was a single point, then all matter would be travelling out and away from it, including the CBR, a bit like the rays from the Sun travelling in al directions... wouldn't it?

Anybody else help?

[joelhall]

Wouldn't everywhere only be the middle if we lived in an infinite universe?

[proflight2000]

well if the ideal that we are all in a sphere zillions of miles big, then when we reach the edge there is no escape as we just go round again, if so then what is outside this sphere. So are we all just being sucked towards the edge?? wished id done physics at school now.

[themos]

http://aether.lbl.gov/www/projects/u2/

U2 Anisotropy Experiment:

[Kaptain Klevtsov]

Because nothing can travel faster than light, anything so far away that light hasn't reached us yet doesn't exist in any real way. The universe is therefore bounded by the information horizon as we have no way of having any information from further away.

For us, and any other observer in a different place, the universe is spherical as anything outside the sphere has no bearing on us, at this time, at our location. The universe that we can know is expanding at the speed of light away from us, the observer, so the universe is infinite, and not , at the same time. If we were to move at a substantial fraction of the speed of light for a period of time, we would find ourselves at a different centre of an infinite spherical universe.

Hope that it made sense?

Captain Chaos

[CELESCOPE]

clear as a bell CC , i think i will stick with imaging , i got lost on the second response hehehehehehehhe .

[stargazer1980]

well i just think we should accept the fact that were here and not out there! We aint gonna see out there in our lifetime so i have the philosophy of not even contemplating thinking about! Just gaze at the heavens and enjoy what the big bang gave us to treasure!

Who care what direction were heading! Its not like its really gonna make much difference to our viewing really is it!!

Darren

[Kaptain Klevtsov]

Who care what direction were heading! Its not like its really gonna make much difference to our viewing really is it!!

Darren

It depends if there's anything in the way. It might be a good idea for somebody to figure out which way we are going and get somebody to look out for trees and stuff in the way.

Captain Chaos

[GordonCopestake]

I like your analogy CC, the information sphere is remarkably similar to an event horizon, only in reverse. Information can't leave an event horizon, and information can't leave an information sphere, or rather can't be perceived from beyond the information sphere. This would mean that our personal information sphere is exactly the same number of light years radius as the age of the univserse, some 14billion years i believe. This gives our information sphere a rough size of 14 billion light years (and expanding at the rate of 1 light year per year). In my (small) mind this means that the univserse really could be infinate, but we have no way of SEEING it. Great stuff!