# [time-nuts] UTC and leap seconds

Brooke Clarke brooke at pacific.net
Fri Jun 11 16:20:25 UTC 2010

```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

iovane at inwind.it wrote:
>
>
>> tvb at LeapSecond.com 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
>> 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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```