I just finished up some hypothetical maths, as I saw yesterday that someone else on the internets repeated my repeated assertion that a really big telescope lens would collapse into a black hole.(adsbygoogle = window.adsbygoogle || []).push({});

I don't think that's correct. OmCheeto said: ↑My very bad maths told me yesterday that it would take a telescope that is 3 light years in diameter to get a clear visual image of the event.

I googled feverishly to get confirmation that my maths was wrong, and found a web site* that said an optical telescope of that size would be so massive, it would collapse into a black hole.

[edit] *found it in my browsing history: http://quarksandcoffee.com/index.php/2015/07/08/aliens-and-dinosaurs/

Now, the original author of the claim, claims to be an Astrophysicist PhD student, so I'm hesitant to correct his maths, as I am notoriously bad at maths.

But we did come up with the same number for a "spherical" silica telescope:

248,544,369,352 m Om's Schwarzschild radius

252,000,000,000 m quarksandcoffee radius

My problem was, that telescope lenses are disks, and not spheres.

Given that I no longer know how to do calculus, I did some very basic maths on the gravitational pull at the edge of a very large and flattish type mirror, and kept coming up with diminishing values for "g" at the edge of my extraordinarily large mirror:

g = 0.0000000005 m/s^2

given:

radius = 130 billion meters

thickness = 0.001 meters

The above radius was based on us extracting all of the silica from the earth's crust (1.4E23 kg of SiO_{2}), as, it seems people like to make mirrors out of glass, even though the working parts of the mirrors are made of aluminium.

ps. According to my calculations, it would take a quadrillion earth crust's worth of silica to reach the Schwarzschild radius.

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# B The League of Extraordinarily BIG Telescopes

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