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PostPosted: Mon Mar 22, 2010 10:48 am 
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Location: England,UK
I was looking though a library book the other day and it go me thinking, how do astronomer know stuff about the stuff for example,when they`ve not even been there,or we`ve not even sent a probe there? i mean how can we say what the sun looks like or how big a star is made of or what a planet or moon etc is like or what happens,when we haven`t been to that planet moon etc?

Cheers

Carl


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PostPosted: Mon Mar 22, 2010 9:38 pm 
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Joined: Fri Jan 23, 2009 11:30 pm
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Location: Lancashire
Physics, dear boy!

OK seriously now. Don't know if you're into podcasts but if so you could do worse than to look up http://www.astronomycast.com/ which explains "...not only what we know, but how we know what we know".

I'm pretty well up on most things astronomical but the other day a colleague asked me how we know how far away the planets are and I couldn't give him an answer. Just goes to show how much we take for granted.


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PostPosted: Tue Mar 23, 2010 9:43 am 
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Thanks for the reply.
But how can we know what the sun is made of when it`s inpossible to even get close to it? :roll: I know there`s physics but in science you need proof.And considering we can`t get close to the sun i can`t see where the answer can come from :lol:


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PostPosted: Tue Mar 23, 2010 10:09 am 
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Scientists can study the light emitted by the sun. For example: when light passes through a gas some wavelengths are absorbed by the gas' atoms. Those wavelengths will show as dark areas, or missing areas, in a spectrum produced here on Earth. These are like signatures. We know from laboratory experiments that hydrogen has its own particular signature and therefore if the spectrum from the Sun has the same dark areas then we know that it was hydrogen that caused it.

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PostPosted: Sun Mar 28, 2010 7:51 pm 
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Joined: Tue Mar 04, 2008 11:24 am
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Carl wrote:
I was looking though a library book the other day and it go me thinking, how do astronomer know stuff about the stuff for example,when they`ve not even been there,or we`ve not even sent a probe there? i mean how can we say what the sun looks like or how big a star is made of or what a planet or moon etc is like or what happens,when we haven`t been to that planet moon etc?

Cheers

Carl

Like Joe says each element has a spectrum signature when light is passed through it or emmited from it. We can detect elements on stars billions of light years away because of this signature. We can detect how hot stars are through the use of our own infrared and ultraviolet spectrum. We can filter out visible light coming from distant objects to reveal other spectrums such as Gamma and Xrays which tell us lots of things. We observe the way objects behave and apply laws we have learned on Earth concerning gravity, motion and enertia. Laws which we learned from Newton are applicable in these scenario's.
We have sent probes to many parts of the Solar system including some of the larger planets which we have collected data from. There are many ways in which we collect data without having being there.


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PostPosted: Sat Apr 17, 2010 6:06 pm 
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Forgot to say thanks alot both of you for your help.You`ve help but my mind at rest and helped me enjoy space and astronomy abit more. :lol:


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PostPosted: Sun Apr 18, 2010 1:57 pm 
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Dear Carl
If you are not convinced by what you read, I think you might find it worthwhile looking through a telescope at some astronomical objects which might answer some of your questions.
Probably the easy way to look through a telescope at astronomical objects is to go to an astronomical society when they have a public viewing night and hopefully you would get the chance to look through a telescope. It probably won't answer all your questions at one go but it is the best way to find out some of the things that I gather you are not happy about. I have been interested in doing practical astronomy for a few years now - I still do not understand much, but I think I understand things better by doing it than just reading books or watching TV programmes about it.
Best of luck from Cliff


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