phildonnia
Master Poster
- Joined
- Oct 20, 2001
- Messages
- 2,439
Here's a hastily drawn space-time diagram to help.
For clarity, I've drawn the spaceship going 70% the speed of light, and then firing a bullet going 70% of the speed of light in the same direction. Everything here is travelling inertially. The yellow line represents the speed of light.
Some things to notice:
The spaceship never overtakes the bullet.
Both the spaceship and the "stationary" observer judge the speed of the bullet to be less than the speed of light; the thin lines show that from each perspective, the space covered is less than the time.
For clarity, I've drawn the spaceship going 70% the speed of light, and then firing a bullet going 70% of the speed of light in the same direction. Everything here is travelling inertially. The yellow line represents the speed of light.
Some things to notice:
The spaceship never overtakes the bullet.
Both the spaceship and the "stationary" observer judge the speed of the bullet to be less than the speed of light; the thin lines show that from each perspective, the space covered is less than the time.