From: Georgi Guninski <gunin...@guninski.com>
On Thu, Aug 04, 2016 at 02:22:05AM +0000, jim bell wrote:
>> http://www.dailymail.co.uk/sciencetech/article-3720772/China-launch-unbreakable-quantum-spy-satellite-say-one-day-lead-megascope-size-Earth-spot-license-plate-Jupiter-s-moons.html
>> [quote]
>> China to launch unbreakable quantum spy satellite - and it could one day
>> lead to a megascope the size of Earth that could 'spot a license plate on
>> Jupiter's moons'>China (Austria is also involved) launched this on 16 August
>> 2016:
> https://en.wikipedia.org/wiki/Quantum_Experiments_at_Space_Scale
>Also in many news.
When I originally posted this, I briefly noted that I had a problem with this
news item. As I recall, one of the problems was that they referred to
this'megascope', without explaining the connection. It was as if two
high-techarticles collided, and bounced off each other, leaving a bit of
detritus on the other.What does this quantum link have to do with building a
super telescope? Thearticle was less than even unclear: It was totally silent
on that matter.
Currently, the largest single-lens telescope mirrors are made in a rotating
furnace in Arizona, about 8.5 meters in diameter. the purpose of the rotation
is to make them very close to the idea curvature from the beginning,rather than
polishing them out of a flat blank of glass as was the previous process.Other
telescopes are going to use multiple-mirrors to increase the
light-collectingarea. That's important, but another factor is that the larger
effective diameter of a telescope mirror, the smaller angular difference that
can be imaged. I recall a data point: A 4.5 inch mirror has a resolution of
about 1 second of arc.(defined, I think, as a line/space pair, not merely a
line.)A telescope based on an 8.5 meter lens will have, ideally, a resolution
of 0.0134arc seconds. Combine seven of them subtending a larger-diameter, and
you'dget perhaps 3 times the diameter, and one third the angular resolution:
About 0.00448 arc seconds.
https://en.wikipedia.org/wiki/Giant_Magellan_Telescope
Would it be possible to 'mount' three such 8.5 meter mirrors in an array where
theyare millions of kilometers away from each other, and somehow combine their
images and to produce and preserve the resolution of the larger diameter? It
wouldn't multiplylight-gathering ability, but it would increase the angular
resolution immensely, perhaps bya factor of 100 million to one billion.I
speculate that this is what is being alluded to in the article's reference to a
'super telescope'. It would not be sufficient to merely detect the images
generated by each mirror; somehowit would be necessary to combine the light
signals to include phase information. Perhaps thiscould be done by some sort
of quantum process.
Jim Bell
