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Old 31-08-2005, 06:01 PM
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Sausageman (Mike Boggan)
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Questions from a Non Astronomer.

I got asked some serious questions today at work, by a Non Astronomer, and I couldn't answer them.

1. How fast does our galaxy spin?
2. How long does it take to complete one revolution?
3. How long does it take our Solar System to complete an orbit of the Galaxy?
4. How fast does our Solar System travel at in it's orbit around the galaxy?

I could answer the last one though.
5. How fast does the Earth move in it's orbit?

Geez, how ignorant am I, being stumped by all those questions?

Someone help me out here please, so I can answer the questions.

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Old 31-08-2005, 07:12 PM
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acropolite (Phil)
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I saw those figures just recently in an astro mag, If I can find it I will post. (imagine a short period of pondering...) ......
Actually just googled and this link gives some of the answers of course the speed would be proportional to our distance from the centre of the galaxy. Here's the google search so you don't even need to type...

It would take the solar system about 200-250 million years to complete one orbit ("galactic year"), and so is thought to have completed about 20-25 orbits during its lifetime. The orbital speed is 217 km/s, i.e. 1 light-year in ca. 1400 years, and 1 AU in 8 days.
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Old 31-08-2005, 07:20 PM
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janoskiss (Steve H)
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All the info you need is in Monty Python's Galaxy Song from The Meaning of Life.
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Old 31-08-2005, 07:27 PM
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asimov (John)
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question 3 answer: 250 million years.
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Old 31-08-2005, 07:39 PM
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Starkler (Geoff)
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Questions 2 & 3 seem to be the same question, assuming that our solar system doesnt move in relation to the rest of the galaxy.
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Old 31-08-2005, 09:12 PM
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Ahh, but it does. It undulates, up & down, as well as into, through & out of, the spiral arms. We, at present, just happen to be 'in the clear' at the moment.
A few years ago, 2 young American Uni students did some calcs. on 'Solar' recession/movement, & found that at about 60/65,000,000 years ago, 'WE' were in close proximity, (if not actually in it), to an arm. It could have been a Supernova in the spiral arm close to 'US' that caused the demise of the dinosaurs..... ie; radiation etc etc from it.
Ahhh, theories. They make you think, don't they?
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Old 01-09-2005, 05:28 PM
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Thanks everyone, especially you Phil.

That google was great, why didn't I think of it? I'm just getting old probably and absent minded

The guy that asked me the questions is apparently a bit of a deep thinker and philosopher. I only found that out today.

Thanks again

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