A solar gravitational lens will be humanity's most powerful telescope (2022)

Is there anything stopping you from putting 2+ satellites out "closer" but in the path of the lensed light, capturing the light simultaneously, and then resolving the image via async computation later? I think this is called interferometry and I know it's hard because you need _very_ precise timing, but I'm curious if that would be possible or not. (Maybe you can get the timing in sync with atomic clocks, or by sending a laser to both from a central point that lets them keep time with some very tight tolerance?)

Weird idea but I wonder if there are ways to take this from "crazy tech" to "hard tech".

> Is there anything stopping you from putting 2+ satellites out "closer" but in the path of the lensed light

The Sun. Literally.

Satellites have to be that far for the Einstein ring to be bigger than the apparent size of the solar disk.

Edit: to make it a bit more clear, the gravitational lens does not quite behave like a normal lens. Instead, you see the light from _behind_ the object. So if you're too close to the lensing object so that the Einstein ring is not larger than it, you'll just see a part of the object to be a bit more bright.

Also, the gravitational lens does not actually _focus_ the image, it distorts it into a band around the lensing object.

>to make it a bit more clear, the gravitational lens does not quite behave like a normal lens. Instead, you see the light from _behind_ the object.

Or to put it another way: A gravity lens bends space so that the light from behind an object curves around it while travelling straight.

"Normal" lenses bend light more strongly farther out towards the edges. Gravitational lensing is shaped differently.

The point is you aren't bending the light, no the light is travelling straight.

You are bending the dimension, the light travels straight through a bent dimension thus coming out curved.

I think that's mindblowing.

No, light doesn't travel in straight lines.

Stronger gravity around massive objects causes slow down of the part of a light wave closer to object, compared to outer part.

This difference in speed, caused by _interaction_ between the photon and gravitational field of the body, results in the bending of the light's trajectory.

Bending of spacetime is just a simplification of this process to model that easier.

> Stronger gravity around massive objects causes slow down of the part of a light wave closer to object, compared to outer part.

That only matters in areas with _really_ high fields, this effect is negligible for areas far away from a singularity of a black hole.

Instead, it's really the space that curves. The light does not slow down, it always moves at the speed of light. In the general relativity there is no "gravity field", gravity is a fictitious force.

Edit: also, gravitational lensing applies to massive point-like particles as well. For slow-moving particles and weak fields, it's negligible compared to regular Newtonian orbits, but if a particle moves at a speed that is close to lightspeed, it'll be lensed just like the light.

You forgot about conservation of momentum. Photon cannot change it's direction without interaction with something to exchange momentum.

"Bending of spacetime" is just computational trick to increase precision of the model.

Bending of trajectory because of change of speed of light is negligible, yes. It's only visible on light-year long distances.

Photon is very wide. Dual slit experiment show that single single photon interacts with two slits up to millimetre apart. Even small difference in speed/frequency at such large distance will accumulate to noticeable change of course at light year long distances.

I can calculate bending radius, if you wish.

> You forgot about conservation of momentum. Photon cannot change it's direction without interaction with something to exchange momentum.

No. I'm not forgetting anything. Photons _do_ _not_ change direction. They always move in straight lines (from their "point of view"). It's just that if you step a bit away, these straight lines are not actually "straight" globally.

A classic example is a 2D ant crawling on a surface of a sphere. From the ant's point of view, it moves in a straight line, but a 3D observer will see that a straight line is actually a 3D circle.

Conservation laws are not violated. A photon (or another particle) will cause its own slight bending of the space-time, that in turn will slightly bend the star's trajectory.

It does sound like an interaction between gravitational fields, but the models give different numeric predictions.

> "Bending of spacetime" is just computational trick to increase precision of the model.

It really is not.

> Photon is very wide.

Facepalm. Sorry dude, but you have no idea what you're talking about. Lensing and time dilation also happen for point-like particles like electrons.