The question behind it
Nothing travels faster than light. That's not a technological limit, it's built into the causal structure of the universe. Every single thing you observe — the sun, a friend across the room, your own hand — is already history by the time it reaches you, because light takes time to travel and nothing can outrun it.
This project turns that idea into runnable, testable code instead of just narration: given a distance, exactly how old is the light you're seeing? And given two events that are simultaneous for one observer, what does a second observer moving at a different velocity actually measure?
"You never observe a true, universal present — what you call 'now' is always already in the past, and how far in the past depends on both distance and who's asking."
What it actually computes
- Light-delay calculator — for any distance, or a built-in catalog of real objects (the Moon, the Sun, Proxima Centauri, Andromeda...), how many seconds/minutes/years old the light you're seeing is right now.
- Relativity-of-simultaneity calculator — the real Lorentz-transform math. Give it two events simultaneous in one reference frame and a velocity, and it computes the time gap a moving observer would measure between them.
- Light cone visualizer — a Minkowski diagram showing an observer's past light cone (what they can observe), future light cone (what they can affect), and the causally-disconnected "elsewhere."
Some real numbers out of it
| Object | Light delay |
|---|---|
| The Moon | 1.28 seconds |
| The Sun | 8.32 minutes |
| Proxima Centauri | 4.25 years |
| Andromeda Galaxy (M31) | ~2.5 million years |
And for relativity of simultaneity: two events exactly 1 light-second apart that are simultaneous on Earth are measured as up to 7 seconds apart by an observer moving at 99% the speed of light — the same two events, genuinely different orderings, and both observers are correct in their own frame.
Why it's built the way it is
Every physics claim in the code is checked in a test suite against a known closed-form result — one light-year of travel takes ~1 year, the spacetime interval is invariant under a Lorentz boost, the Sun's delay is ~8 minutes — rather than just asserting the code runs. It doesn't attempt to test or "prove" the deeper metaphysical question (whether past, present, and future are all equally real — the "block universe" debate); there's no known experiment that settles that. What it does do is make the one part of the picture that is checkable — finite propagation speed causing observation delay — concrete and verifiable.
Code
Source, tests, and a runnable demo are on GitHub: github.com/ribeshbk/now-delay.
Last updated: August 2026 · Personal research project, built with Claude.