Re: A question about cosmic microwave radiation and specialrelativity
From: N:dlzc D:aol T:com \(dlzc\) (net_at_nospam.com)
Date: 03/20/05
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Date: Sun, 20 Mar 2005 16:07:30 -0700
Dear Bill Hobba:
"Bill Hobba" <bhobba@rubbish.net.au> wrote in message
news:%cn%d.5286$C7.3397@news-server.bigpond.net.au...
>
> "Michael Levin" <mlevin77@comcast.net> wrote in message
> news:BE63606D.20EB1%mlevin77@comcast.net...
>> On 3/20/05 6:56 AM, in article
>> 6yd%d.4957$C7.1245@news-server.bigpond.net.au, "Bill Hobba"
>> <bhobba@rubbish.net.au> wrote:
>>
>> > "Michael Levin" <mlevin77@comcast.net> wrote in message
>> > news:BE62C8D3.20D21%mlevin77@comcast.net...
>>
>> Hi Bill -
>>
>> >> If it got
>> >> generated at the time of the big bang, as space expands
>> >> outwards, it
> will
>> >> either zoom past us if the expansion is slow, or if the
>> >> inflation is
> much
>> >> faster than the speed of light, will take a while to get to
>> >> us.
>>
>> > Light a candle inside an expanding balloon - the light fills
>> > the inside
> of
>> > the balloon.
>>
>> if a candle is the right analogy, then I see it. But I
>> thought a better
>> analogy would be a camera flash, not a constantly-on candle.
>> The process
>> which generated the microwave radiation - was it time-limited
>> or is it
> still
>> going on?
>
> It occurred at the big bang when light decoupled from matter
> (ie no longer
> strongly interacted with it) and is now not going on -
> http://www.damtp.cam.ac.uk/user/gr/public/cmbr_dec.html
>
>> If it's still going on, then I get it. But if it was some
>> process
>> which happened and then stopped (perhaps at the big bang),
>> shouldn't it be
>> more like a flash inside a balloon, which would spread out
>> from the center
>> of the balloon, leaving the center dark while the light heads
>> outwards
>> towards the periphery?
>
> Imagine the flash happening at all points in the balloon thus
> filling it
> with a gas of photons (like blackbody radiation contained by
> the size of the
> unversed at the time). As the balloon expands the gas expands
> to fill up
> the increased space and gets 'redshifted' in the process (the
> increase in
> the velocity of observers in the expanding space redshifts it).
This part of your analogy is really appropriate too, because if
you expand a gas, it cools down... just like the CMBR is observed
to cool down. Of course it fails when you look at average
velocities of gas particles... as compared to light.
David A. Smith
- Next message: N:dlzc D:aol T:com \(dlzc\): "Re: I'm a wandering fool, wandering the path: cosmology => polyhedra => 4-D => hyberbolic solids, tossing questions along the way just like Johnny Appleseed"
- Previous message: Ken S. Tucker: "Re: General Relativity question"
- In reply to: Bill Hobba: "Re: A question about cosmic microwave radiation and specialrelativity"
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