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Astronomical Question - 10/19/2006 3:20:21 AM

LadyEllen

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No - not how much money do I earn in a year......... that would be more of a microscopical question.

We were watching two documentaries the other day about the universe. The first said that the universe is expanding in all directions. The second said that the Andromeda galaxy is approaching and will collide with the Milky Way in a few billion years. We already heard both these theories, but the juxtaposition in two successive documentaries got us to thinking - how can the Andromeda galaxy be scheduled to collide with the Milky Way, if the universe is expanding in all directions? Surely the expansion should mean that Andromeda must be moving away from us?

Over to the astronomical brains of CM!

E

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RE: Astronomical Question - 10/19/2006 4:51:09 AM

FangsNfeet

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Here's a shot.

With the expansion, the Milkyway is moving at a different speed than the Andromeda. I don't know which one is in front but the galaxzy in the back will sooner or later catch up.

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RE: Astronomical Question - 10/19/2006 5:26:46 AM

Zensee

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Andromeda is the closest galaxy to our own, about 2.5 million light years. Although the universe in general is expanding, clusters of galaxies may experience gravitational interactions within the group. The following excerpt is from a Wikipedia article on Andromeda.

quote:

The Andromeda Galaxy is approaching the Sun at about 300 kilometres per second (186 miles/sec.), so it is one of the few blue shifted galaxies. Given the motion of the Solar System inside the Milky Way, one finds that the Andromeda Galaxy and the Milky Way are approaching one another at a speed of 100 to 140 kilometres per second (62–87 miles/sec.).

However, this does not mean it will collide with the Milky Way, since the galaxy's tangential velocity is unknown. If it is on a collision course, the impact is predicted to occur in about 3 billion (109) years. In that case the two galaxies will likely merge to form a giant elliptical galaxy.[15] Such events are frequent among the galaxies in galaxy groups.

0

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RE: Astronomical Question - 10/19/2006 5:56:56 AM

Rule

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At close distances the spectral shift as a result of the proper motion of stars exceeds the spectral shift of the socalled 'expansion' of the universe, which is additional and thus negligible at relatively nearby, small distances.

We have to distinguish between observed facts and interpretation, though. We know that nearby galaxies have a proper motion and that the shift of their spectrum is the result of the Doppler effect.

However, we do not know at all that the spectral shift of far galaxies is the result of a proper motion: that is merely and quite lazily assumed.

The expanding universe interpretation is supported by only a few pillars: the redshift of far galaxies, the cosmic background radiation and the hypothesis of general relativity. In the little known book that I wrote about my discoveries in astronomy I provide alternative explanations for the first two observations and throw strong doubt upon the hypothesis of general relativity.

I blame the redshift of far galaxies on the photons getting 'tired' the farther they travel, exchanging wave energy for their increase in angular momentum the farther they move from their source. I deduced a formula that accurately describes the redshift of a photon emitted with a particular frequency. (It needs a calibration factor, though).

It is this shedded wave energy that we perceive as the cosmic background radiation. (It all comes neatly together.)

< Message edited by Rule -- 10/19/2006 6:01:30 AM >

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RE: Astronomical Question - 10/19/2006 9:17:09 AM

MasterFireMaam

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Zensee is correct. While the Universe, as a whole, is expanding, if things get clumped together, gravity makes the clumping even more pronounced. This is how we get galaxies in the first place..as well as galactic clusters, stars and solar systems, to name a few. Think of it as kinda like how grits clump when they cool. LMAO

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RE: Astronomical Question - 10/19/2006 9:46:28 AM

ToGiveDivine

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Personally, I just think the Milky Way and Andromeda have the hots for each other - in a few billion years, they will produce some little bitty galaxies to bounce on their knees :-D

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RE: Astronomical Question - 10/19/2006 10:09:05 AM

LadyEllen

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Thanks everyone. Especially TGD, who I think gave the loveliest explanation, even if not based on science like the others!

E

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RE: Astronomical Question - 10/19/2006 10:39:08 AM

philosophy

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"Think of it as kinda like how grits clump when they cool. LMAO"

....ewww.....grits.......now i'm going to have a horrible taste in my mouth every time i look at a galaxy.........why couldn't it have been porridge, with honey and flaked almonds?

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RE: Astronomical Question - 10/19/2006 12:49:54 PM

Lashra

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Gee, I hope I remember to bring my camera when it happens...

~Lashra

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