Hi Antonio:
It turns out that the atmosphere has instabilities that make the
position of a star appear to vary a few arc seconds and that effect is
called "seeing".
Because of the seeing you can not use an optical telescope to make a
measurement of the Earth's rotation to the accuracy needed to see the
slowing down.
See: http://www.prc68.com/I/StellarTime.shtml
If you're interested in modern developments in our understanding of the
universe have a look at these:
Richard Feynman Messenger Lectures - Gravity
http://research.microsoft.com/apps/tools/tuva/index.html#data=4%7C0%7C%7C6b89dded-3eb8-4fa4-bbcd-7c69fe78ed0c%7C%7C
TED Talks
http://www.ted.com/talks
Some interesting talks about astronomy, a 6 dimensional model that
predicts new particles to look for, gravity lens image, etc.
Have Fun,
Brooke Clarke
http://www.PRC68.com
[email protected] wrote:
[email protected] wrote:
Beside the general theoretical considerations as of what answer is more
acceptable (sincerely I agree so far) and what method could be used to
solve
the matter, can anybody out there point me please to any article on actual
measurements of the variation rate of the earth's rotational speed, not
based
on clocks?
Antonio,
Consider that you need at least two clocks before you can
make a rate measurement. One is the DUT; the other the
REF. So it is not possible to measure the earth (DUT) without
using some other clock (REF). Make sense?
To some extent, yes. I was wrong using the word "rate" in my text above. If we
remove that word, then there is no need for clocks.
Quoting Bob
"When the sun rose 100 years ago the stars looked like this. Today when the
sun rises, the stars are in slightly different positions. "
there should be a possibility of noticing a variation (not its rate) simply
looking at the sun and distant stars.
(Speculative hint: We accept that the universe is expanding. Might this
affect
the fine structure of matter, including cesium atoms? Is there any adverse
proof? What is easier to think? a) the expansion of the universe doesn't
affect
at all the properties of matter. b) it might.).
There is no small amount of effort being put into this question.
The results are not usually given as yes/no, zero or non-zero.
Instead they just calmly establish a new lower bound on what
the drift rate might be.
Yes.
Whether the answer is (a) or (b) doesn't change the fact that
the earth day is a poor clock compared with other clocks now
available. Besides tidal friction effects which might be hard to
imagine, or lunar effects which you already know about, note
that every time it rains or glaciers form and melt it changes the
angular momentum of the poor spinning planet. Then again,
many OCXO are also affected by humidity...
I think the answer is in your previous post, that is the year is more stable
than the day as compared to the same clock.
And this measurement very likely has been actually made.
Antonio I8IOV
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