Physics and aerospace
Why Light Speed Is More Than a Speed Limit
Light does not merely travel very fast. Its speed helps define the relationship between space, time, information and cause and effect.
Established ScienceWhat we actually know
c is not a property of light so much as a property of spacetime that light happens to travel at. Nothing carrying usable information has ever been observed to travel locally faster than it. A consequence often skipped over: looking farther into space means looking further into the past. The Sun you see is eight minutes old. Webb's deepest fields are more than thirteen billion years old. There is no way to see the universe as it is now, anywhere but here.
Where the extrapolation begins
This makes distance and time the same limitation wearing different clothes. A twenty-light-year bubble is not only a region of space; it is a twenty-year-old snapshot of that region.
What the novel invents
The novel's census of nearby stars is therefore always a census of the past — a point Hartmann makes and the room does not enjoy.
Questions to think about
- — If you cannot observe 'now' anywhere else, what does 'simultaneous' actually mean?
- — How does light-travel time change how you read any astronomical image?
Where to read next
- — Einstein, special relativity — the invariance of c
- — Light-travel time and lookback time in observational astronomy
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