The Rest Is Science How To Use a Black Hole To See Your Past
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May 4, 2026 They explore how light always shows the past and how mirrors make us see earlier versions of reality. A nanosecond ruler demo reveals how tiny delays shape perception. Black holes and photon spheres could bend ancient light back toward Earth. The Sun as a gravitational lens and using atmospheres as giant telescopes are weighed against practical limits, scale, and ethical questions.
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Five Tomatoes Mnemonic For Feet In A Mile
- Michael Stevens shares a mnemonic: 'Five tomatoes' to remember there are 5,280 feet in a mile.
- He uses this lighthearted aside while introducing the topic to illustrate how his research scattered him into many small facts.
Everything You See Is Already History
- Every photon you see left you in the past so there is an expanding sphere of 'ghost' photons recording your earlier states.
- Michael Stevens demonstrates with a 30 cm nanosecond ruler: each 30 cm of distance equals ~1 nanosecond of visual delay, so nearer observers see only nanoseconds-old versions of you.
Nanosecond Ruler Demonstration With Thumb
- Michael Stevens physically demonstrates with a transparent 30 cm 'nanosecond ruler' to show how light travel creates visual delay.
- He holds his thumb and explains that light takes ~210 picoseconds to cross a thumb and a nanosecond per 30 cm.