You could use the sun as the lens of a telescope to resolve city-size details on exoplanets. Might be easier to go 500 AU than several light years.

You mean the sun as the Sun or as their local star? Not sure how you'd use ours as a lens.

I mean using our sun as a gravitational lens. There's a schematic at https://www.planetary.org/space-images/solar-gravity-lens-te...

One big problem (besides getting out there - hehe) is that you are looking in one very particular direction and need to move big distances (at a distance of ~500 au from the sun) to look elsewhere. I guess you could wait until the planet you are aiming at does another orbit around its star and flies through your point of focus again.

PS Voyager launched in 1971 and is now at 158 au! These distances are truly vast. 1 light year is 63241 au.

That's incredible. How are the photons from the planet not entirely drowned out by those emanating from the sun?

When you are using the sun as a gravitational lens you block out the sun and look at the area of the sky around the sun.

There's a wikipedia page for the concept at

https://en.wikipedia.org/wiki/Solar_gravitational_lens

This is the space project that most excites me and the one I most hope we solve in my lifetime. Much more interesting than Mars (not that you can't do both).

This video on gravitational lensing blew my mind https://youtu.be/NQFqDKRAROI

What do you think the odds are of if it being done IRL?

I don’t know anything specific about what the parent is proposing, but I imagine it is using the mass of the sun as a gravitational lens. Because of the solar radiation there isn’t really much sunlight (read:any) that is directly reflected to an observer peering on the edge of the sun.. light travels in straight lines.

Basically, the way scientists used a solar eclipse to confirm the theory of relativity and gravitational lensing of stars ‘behind’ the sun to in front of it. Or like the way certain objects were lensed in the massive JWST shot that came out a couple months ago.

But beyond that I know nothing

Here's the paper discussing this idea:

https://arxiv.org/pdf/2002.11871.pdf

They take pictures at night when there’s no sunlight.

Thanks for the perspective, I was curious about this.

Or are mindbogglingly slow. If we can reach 90% of lightspeed we would have a good Lorentz number to travel the whole milkeyway in a few weeks. We would see a very different earth though when we come back.

Time dilation at 0.9 c is only 2.3x (where 1x is no dilation).

   Lorentz factor γ = 1 / sqrt(1 - (v/c)²) = 1/sqrt(1 - 0.9²) = 2.29

To travel 87,400 light years at near light speed, in a subjective time of a month requires a dilation of 87400 years * 12 months / year = 1048800, with a speed of:

   (1-(1/1048800)²) c = 0.9999999999990908 c

which is about 0.27 mm/s slower than the speed of light.

For comparison, the protons at CERN only hit 0.999999991 c (https://public-archive.web.cern.ch/en/LHC/Facts-en.html) and the electrons at SLAC only hit 0.99999999995 c (https://www.slac.stanford.edu/pubs/slacpubs/5500/slac-pub-56...).