Phil PlaitFeb 20

In other news…

This was fun: a reader asked if aliens were in a galaxy 66 million light-years away, how big a telescope would they need to see dinosaurs on Earth?

Guess!

No; bigger. Try again. Nope, still bigger. Third try? Nope. Way, WAY bigger.

https://www.scientificamerican.com/article/could-aliens-in-another-galaxy-see-dinosaurs-on-earth/

Could aliens in another galaxy see dinosaurs on Earth?

How big would a telescope need to be to see Earth’s dinosaurs from 66 million light-years away? Think big—and then think bigger

Scientific American
Show threadFlipper 🐬🏳️‍🌈

@badastro well, the Rayleigh criterion says that it should be bigger than 1.22 lambda / theta, where lambda is the wavelength of the light and theta is the angular resolution of the observed object (in this case a dinosaur of order of 10m)

This gives:
D = 1.22 * 0.5x10^-6 / inv sin(3.4x10^-14)

I can't get any inverse sin calculator to return a result for such a small value that wasn't zero, so I'm going to estimate it as being approximately 10^-14.

So my guess for the telescope diameter is anywhere between a million kilometers and infinity.

Edit: I read the article and I think they got the 66ly in metres wrong (they said it was 6.6x10^23m) -- but they use the angular resolution as 10^-21 radians which increases my calculation by 10^7.

Feb 20 at 10:18pmWeb