3 ms·
Seeing Triple (Annotated)
- Cthulhu_ 3y agoSee also: Einstein Ring [0], where a light source passes 'through' a strong gravitational source which refocuses the light spreading out, and the Einstein Cross [1], similar, but where the light source (a quasar) passes a gravitational source and shows up as four points of light "due to the elongated shape of the lensing galaxy and the quasar being off-centre" [0] https://en.wikipedia.org/wiki/Einstein_ring https://en.wikipedia.org/wiki/Einstein_ring [1] https://en.wikipedia.org/wiki/Einstein_Cross https://en.wikipedia.org/wiki/Einstein_Cross
- bobbylarrybobby 3y agoAlso fascinating is that celestial bodies that get duplicated by lensing always produce an odd number 2n+1 of images, n of which are inverted and n+1 of which are upright. I won't pretend to understand why this is. https://en.m.wikipedia.org/wiki/Odd_number_theorem https://en.m.wikipedia.org/wiki/Odd_number_theorem
- kmill 3y agoA handwavy argument for this is that if you continuously deform your picture, you can bring an upright and an inverted image toward each other until they cancel out (if you've ever played around with curved mirrors you probably can imagine how that would look). Eventually, after doing enough of these cancelations, you're left with an undistorted picture with a single upright image -- so, you must have had n inverted images and n+1 upright ones. The morse theory the wikipedia article mentions is roughly about being able to do this argument rigorously.
- LoganDark 3y agoNon-mobile link: https://en.wikipedia.org/wiki/Odd_number_theorem https://en.wikipedia.org/wiki/Odd_number_theorem
- tomcam 3y agoI hate it when the universe just cuts and pastes instead of spawning a new galaxy like the rest of us would