VISUAL ARCHIVE / IMAGE STORY
A Tiny Motion Across an Enormous Distance
Different motions produce different assignments of distant simultaneity.
The difference between the observers is almost invisible near Earth, yet distance acts as an enormous amplifier. Extend two slightly different definitions of simultaneity across millions of light-years and the events assigned to the present can separate by days.
THE OBSERVATION
What we can actually see.
In special relativity, the time coordinate assigned to a distant event depends on the observer’s inertial frame. At Andromeda’s distance, a small relative walking speed can make the assigned times differ appreciably.
THE ILLUSTRATION
What the artwork imagines.
The split clocks and sweeping lines are a diagrammatic analogy, not a measurement of Andromeda’s local time. Nearby observers still agree about their shared event here on Earth.
FROM THE ILLUSTRATED ARTICLE
The story that inspired it.
The Andromeda thought experiment distinguishes the delay of light from the relativity of assigning a distant event to a local present. Different motions produce different assignments of distant simultaneity.
Read There Is No Such Thing as “Right Now” Across the UniverseCHECK THE RECORD
The image interprets the research below. Follow the original work for the measurements and limits behind the scene.
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