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studying non visible waves (CMB, hydrogen 21)

  • fguihen
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can you explain how people study this CMBR, and also hydrogen 21 as i believe its called. from what i understand , these things both need radio telescopes to pick up. with CMB, if it is , everywhere, then what can we learn from it? i can see how the extending wavelength of it can tell wherebouts it originated, but with CMB comming from everywhere, how do you decide what piece to look at and what to ignore? the same with the 21cm wavelength hydrogen. its wavelength extends and people look for 1.3 m wavelengths now, but that only tells them how far the wave has travelled. also, can you study these radiowaves way out in space, so as to see them in a younger state, as we do with visible light? ( you know the way that the light we see on earth could be many thousands of light years old, but hubble will see the same object a lot younger).does this work for non visible light? i know its a bit of a noobe question, but i read about it all the time in magazines and want to understand exactly what im reading.thanks
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16 years 2 months ago #35263

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can you explain how people study this CMBR, and also hydrogen 21 as i believe its called. from what i understand , these things both need radio telescopes to pick up. with CMB, if it is , everywhere, then what can we learn from it? i can see how the extending wavelength of it can tell wherebouts it originated, but with CMB comming from everywhere, how do you decide what piece to look at and what to ignore? the same with the 21cm wavelength hydrogen. its wavelength extends and people look for 1.3 m wavelengths now, but that only tells them how far the wave has travelled. also, can you study these radiowaves way out in space, so as to see them in a younger state, as we do with visible light? ( you know the way that the light we see on earth could be many thousands of light years old, but hubble will see the same object a lot younger).does this work for non visible light? i know its a bit of a noobe question, but i read about it all the time in magazines and want to understand exactly what im reading.thanks


The CMBR tells us a lot by it's general properties. It's temperature tells us a lot, it's polarity tells us a lot and in particular it's small but non-zero fluctuations tell us a lot. By looking at the properties of that 'light' we can learn about the early universe. The fact that it's everywhere doesn't take away from properties like temperature, polarization and anisotropy.

As for Hydrogen 21, radio waves travel through obstacles much better than light waves so we can see through obstacles at these wave-lengths. At each wave-length we learn some extra, when we combine what we see in them all we begin to get a full picture of the universe.

Bart.
My Home Page - www.bartbusschots.ie
16 years 2 months ago #35264

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can you explain how people study this CMBR, and also hydrogen 21 as i believe its called. from what i understand , these things both need radio telescopes to pick up. with CMB, if it is , everywhere, then what can we learn from it? i can see how the extending wavelength of it can tell wherebouts it originated, but with CMB comming from everywhere, how do you decide what piece to look at and what to ignore?


In the case of the CMBR you look at all of it. Then factor in the local doppler effects to get the overall picture. Finding the CMBR being so uniform tells us a lot, and its temperature constrains the models of the early universe. The small fluctuations in it are one of the most interesting things in cosmology at the moment as they are thought to give clues about how the universe ended up in its present state with galaxies in some places and apparent voids in others. Models of how these fluctuations originated also help to constrain ideas of dark matter in the early universe.

On a related note the CMBR is the glow of the photons from that early point in the universe, there is also a cosmic neutrino background. Detecting this will be much harder.

the same with the 21cm wavelength hydrogen. its wavelength extends and people look for 1.3 m wavelengths now, but that only tells them how far the wave has travelled. also, can you study these radiowaves way out in space, so as to see them in a younger state, as we do with visible light? ( you know the way that the light we see on earth could be many thousands of light years old, but hubble will see the same object a lot younger).does this work for non visible light? i know its a bit of a noobe question, but i read about it all the time in magazines and want to understand exactly what im reading.thanks


I don't really understand the question to be honest. The 21cm line is the emission line of neutral Hydrogen. Thats assuming of course that there is no relative motion, with the doppler effect and cosmological redshifts the lines will change. One application of the 21cm line is to study the doppler shifts of it across galaxies which can give us the rotational speed of the galaxy. The doppler effect and cosmological redshift work for all wavelenghts of light.

( you know the way that the light we see on earth could be many thousands of light years old, but hubble will see the same object a lot younger).


I'm not following here. A telescope on earth and Hubble will see the same light from the object. The photons that each sees will be the same age and the object will look the same to both.

hth
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16 years 2 months ago #35265

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( you know the way that the light we see on earth could be many thousands of light years old, but hubble will see the same object a lot younger).

sorry, i thought hubble could see objects as they were many millions of years ago, as it is looking at light from them that has not yet reached us. am i wrong in this assumption?
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16 years 2 months ago #35266

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( you know the way that the light we see on earth could be many thousands of light years old, but hubble will see the same object a lot younger).

sorry, i thought hubble could see objects as they were many millions of years ago, as it is looking at light from them that has not yet reached us. am i wrong in this assumption?


Slightly wrong. When Hubble looks at a distant galaxy it will see it as it was millions of years ago. Thats how long it took the light to get to us. If you look at the same galaxy through a telescope here on Earth you will see the exact same galaxy at the same age. The photons are the same age as the ones that Hubble sees.

What Hubble can do thanks to its optics and being above the atmosphere is see other galaxies that telescopes on earth cannot see. These are fainter objects and further away and hence are older.

Cheers,
~Al
Albert White MSc FRAS
Chairperson, International Dark Sky Association - Irish Section
www.darksky.ie/
16 years 2 months ago #35267

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thanks for clearing that up for me :)
I know my questions may seem a bit silly but i jst want a better understanding of whats going on , and these questions are the things that magazines take for granted that readers know
"Success is the happy feeling you get between the time you do something and the time you tell a woman what you did." Dilbert.
16 years 2 months ago #35276

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thanks for clearing that up for me :)
I know my questions may seem a bit silly but i jst want a better understanding of whats going on , and these questions are the things that magazines take for granted that readers know


There's no such thing as a silly question! The whole point of these boards is to give people a place to share their experiences and broaden their understanding of astronomy. If there's something you're not sure if this is a great place to ask!

Bart.
My Home Page - www.bartbusschots.ie
16 years 2 months ago #35277

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The only silly questions are those that aren't asked. I'm certainly glad you asked it - I've learned a lot from Bart and Al!

Cheers

Dave
16 years 2 months ago #35298

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