In other news…

[badastro@mastodon.social]

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/

[robo105@mastodon.social]

@badastro wild ass guess here but about the size of our solar system???

[michael_w_busch@mastodon.online]

@Robo105

Considerably larger than that.

There is also an additional complication that @badastro did not have the space to get into:

The interstellar and intergalactic medium will eventually blur the wavefronts, making imaging impossible.

[robo105@mastodon.social]

@michael_w_busch @badastro Well there goes my business idea of selling videos of other planets as reality TV

[michael_w_busch@mastodon.online]

@Robo105 @badastro

There are other tricks one could play, such as using a star as a gravitational lens to magnify the image of the Sun and Earth.

But we cannot change the laws of physics.

[cliffsesport@mastodon.social]

@badastro ehh it doesn't work that way

[dpnash@c.im]

@badastro Phil Plait doubtlessly knows all this, so this is very much a "yes, and..."

Those of us who are amateur astronomers can guess just how extreme the size needed must be, even without knowing the exact numbers. We look at, say, Mars, and even with a big telescope (by amateur standards, that is -- let's say 20 inches or 0.5 meters in diameter), we're doing well to see Earth-continent-sized regions of the planet as distinct entities, and then mostly because of color contrast, not specific surface details. Under some very specific conditions, you can see smaller things, but again only by virtue of contrast. The smallest thing you can see on Mars with large amateur gear is Olympus Mons (and it's not recognizable as a mountain, just as a differently colored dot), which is roughly (in linear dimensions) the size of France.

That's for a planet a few light-*minutes* away, just to see things at best on the scale of an extremely large mountain. For millions of light years, and things on the scale of a T. rex, you realize you have to scale things up by an almost unfathomable amount even before you reach for the calculator.