Science > Physics > one billionth degree above absolute zero, how did they measure it?
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Science > Physics |
| User: |
"John Smith" |
| Date: |
12 Apr 2007 07:47:38 PM |
| Object: |
one billionth degree above absolute zero, how did they measure it? |
The lowest temperature achieved in the lab is one billionth degree
above absolute zero. How is this temperature measured and how
precise is the method? Any references would be greately appreciated.
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| User: "Uncle Al" |
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| Title: Re: one billionth degree above absolute zero, how did they measure it? |
12 Apr 2007 07:58:32 PM |
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John Smith wrote:
The lowest temperature achieved in the lab is one billionth degree
above absolute zero. How is this temperature measured and how
precise is the method? Any references would be greately appreciated.
In the gas phase you can do it by Doppler frequency shift. Frequency
counting by beats from a calibrated source is pretty good for
accuracy. You can also do it by ratio of spin states vs. transition
energy - though if you get a population inversion you go negative
degrees kelvin, and that's hot - but not translationally.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/lajos.htm#a2
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| User: "Androcles" |
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| Title: Re: one billionth degree above absolute zero, how did they measure it? |
13 Apr 2007 12:49:55 AM |
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"Uncle Al" <UncleAl0@hate.spam.net> wrote in message =
news:461ED5B8.D709BE3D@hate.spam.net...
[snip river of *****]
1: GPS works.
2) Fuckhead.
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| User: "John Smith" |
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| Title: Re: one billionth degree above absolute zero, how did they measureit? |
13 Apr 2007 06:17:37 PM |
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Uncle Al wrote:
John Smith wrote:
The lowest temperature achieved in the lab is one billionth degree
above absolute zero. How is this temperature measured and how
precise is the method? Any references would be greately appreciated.
In the gas phase you can do it by Doppler frequency shift. Frequency
counting by beats from a calibrated source is pretty good for
accuracy. You can also do it by ratio of spin states vs. transition
energy - though if you get a population inversion you go negative
degrees kelvin, and that's hot - but not translationally.
Frequency of what?
Gas phase at one billionth degree above absolute zero? I don't
think so.
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| User: "Uncle Al" |
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| Title: Re: one billionth degree above absolute zero, how did they measureit? |
13 Apr 2007 06:18:51 PM |
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John Smith wrote:
Uncle Al wrote:
John Smith wrote:
The lowest temperature achieved in the lab is one billionth degree
above absolute zero. How is this temperature measured and how
precise is the method? Any references would be greately appreciated.
In the gas phase you can do it by Doppler frequency shift. Frequency
counting by beats from a calibrated source is pretty good for
accuracy. You can also do it by ratio of spin states vs. transition
energy - though if you get a population inversion you go negative
degrees kelvin, and that's hot - but not translationally.
Frequency of what?
Gas phase at one billionth degree above absolute zero? I don't
think so.
Work out the velocity of an atom at temp and think "laser speed gun."
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/lajos.htm#a2
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| User: "Androcles" |
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| Title: Re: one billionth degree above absolute zero, how did they measureit? |
13 Apr 2007 07:55:29 PM |
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"Uncle Al" <UncleAl0@hate.spam.net> wrote in message =
news:46200FDB.BEAB9F4E@hate.spam.net...
[snip river of *****]
Work out=20
HAHAHAHA! You work it out.=20
1) GPS works.
http://users.erols.com/dlwilson/gpswaypt.htm
2) Fucking imbecile.
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| User: "The Ghost In The Machine" |
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| Title: Re: one billionth degree above absolute zero, how did they measureit? |
13 Apr 2007 10:05:10 PM |
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In sci.physics, Androcles
<Engineer@hogwarts.physics.co.uk>
wrote
on Sat, 14 Apr 2007 00:55:29 GMT
<5EVTh.13013$Zb2.1007@fe2.news.blueyonder.co.uk>:
"Uncle Al" <UncleAl0@hate.spam.net> wrote in message news:46200FDB.BEAB9F4E@hate.spam.net...
[snip river of *****]
Work out
HAHAHAHA! You work it out.
1) GPS works.
http://users.erols.com/dlwilson/gpswaypt.htm
2) Fucking imbecile.
An orbiting GPS satellite describes a nearly circular orbit from point A to
point A. What is its speed? Since the distance from A to A is zero,
and the satellite takes 12 hours to orbit from A back to A, the orbital
speed is also zero, is it not?
Or is there something you're missing here?
--
#191,
Useless C++ Programming Idea #12995733:
bool f(bool g, bool h) { if(g) h = true; else h = false; return h;}
--
Posted via a free Usenet account from http://www.teranews.com
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| User: "Andy Resnick" |
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| Title: Re: one billionth degree above absolute zero, how did they measureit? |
16 Apr 2007 09:08:57 AM |
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John Smith wrote:
The lowest temperature achieved in the lab is one billionth degree
above absolute zero. How is this temperature measured and how
precise is the method? Any references would be greately appreciated.
That's a good question- and it shows that a common-sense idea about
'temperature' can't be extrapolated down to these values.
First, recall that thermodynamics and statistical mechanics has a
fundamental relationship between energy and temperature, encoded in
terms like exp(E/kT). One result is that temperature is actually a
logarithmic scale- getting to a temperature of 0 K requires infinite
energy. Also, the precision of the measurement isn't as amazing as it
may seem.
Another result is that 'temperature' has less to do with how hot or cold
something is, but how the energy in a collection of objects is
distributed. For example, take 100 atoms, each with 1 femto-erg of
energy. That's our common sense idea of atoms at about 7 K. Now, let's
elastically collide the atoms together somehow so that one atoms ends up
with nearly all of the 100 femto-ergs of energy, while the others have
nearly no energy. Then remove that single atom. The remaining atoms are
much 'colder', meaning they have much less energy.
I couldn't easily find any good references, but atom trapping
experiments, which are presumably what you read about, assign
temperature by measuring energy, specifically energy shifts by collision
with carefully tuned 'cooling' lasers. And these temperatures are of
very small numbers of atoms, not something macroscopic. The experiments
are also done in a vacuum, so air atoms at 300 K don't collide with and
heat up the cold atoms.
There's a lot on low-temp physics and methods on the web: magnetic
cooling, spin cooling, laser cooling, etc. that have nothing to do with
putting a sample in thermal equilibrium with, for example, liquid helium.
--
Andrew Resnick, Ph.D.
Department of Physiology and Biophysics
Case Western Reserve University
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