Cosmic Scale
Near light speed
Flying at 99% of light's speed: how the sky would crowd ahead and go dark behind, and what the trip would cost
A what-if: physics allows it on paper, but no one has ever seen one. Everything shown follows the theory as it stands.
Step by step
The cosmic speed limit
Nothing with mass can reach the speed of light, 299,792 km a second, but a ship could come close. This is the sky as it would look from one flying at 99% of that.
Einstein's special relativity of 1905 rests on one fact: light's speed is the same for everyone, however fast they move. Chase a beam of light and you would still measure it leaving you at 299,792 km a second. To keep that true, space and time themselves must behave differently for anyone who moves fast.
The view behind
Turn round and the other half of the stars is spread over almost all of the sky, dimmed and reddened: behind a ship at this speed lies a dark, nearly empty-looking void.
The half of the stars that lie behind you in the sky's own frame must fit everywhere outside the small circle ahead, which is nearly the whole view. Each is seen farther towards the back than it really is, so the sky seems to stretch out and thin.
Objects in this story
More simulations
- S301: the fastest known star
- Comet Shoemaker-Levy 9 hits Jupiter
- The asteroid that ended the dinosaurs
- How a star is born
- Pulsar
- Earth's magnetic shield
- The Sun's death
- A star torn apart
- A massive star explodes
- Type Ia supernova
- How black holes are made
- Two black holes merge
- Two neutron stars collide
- Magnetar
- Quasar
- Gravitational lensing
- The brightest gamma-ray burst
- The Milky Way meets Andromeda
- The Big Bang