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Physics · Calculator · Interactive explainer

Relativistic travel calculator

Model constant-acceleration trips where the ship accelerates halfway, flips, and brakes for the second half. Compare Earth time, traveller time, peak speed, signal lag, and the energy scale that makes fast interstellar travel hard.

Set the trip

Target search intent: relativistic travel calculator, 1g trip to Alpha Centauri, time dilation space travel.

0.1g is gentle. 1g gives Earth-like gravity on board but drives the ship into obviously relativistic territory for long trips.

tonnes

Mass only changes the kinetic-energy estimate. It does not try to solve propellant, waste heat, or engine design.

What this page assumes

  • The ship starts and ends at rest relative to Earth.
  • It accelerates halfway, then flips and brakes at the same rate.
  • The model ignores gravity wells, orbital transfers, propellant mass, and shielding.
  • The point is intuition about time dilation and speed, not a full mission architecture.

That narrower model is what makes the comparison between Earth clocks and traveller clocks clean enough to trust.

Read the launch note for this calculator.

Trip snapshot

Timeline and scale

Reading the numbers

Why this is useful

A lot of relativity pages stop at one formula. This one tries to answer the more human question: how much time passes for the crew, how much for Earth, how fast the ship gets, and what sort of energy budget that implies.

Browse more tools and guides in the same area.

Try a few adjacent pages while you are here.