At what speed does a spaceship move relative to the earth if the clock on it runs 2 times slower than on Earth?

To find the speed of the starship, we use the formula: t = t0 / √ (1 – V ^ 2 / C ^ 2), whence 1 – V ^ 2 / C ^ 2 = √ (t0 / t); V ^ 2 / C ^ 2 = 1 – (t0 / t) ^ 2 and V = √ (1 – (t0 / t) ^ 2) * C.

Constants and variables: t0 – time on the starship; t – time on Earth (t = 2t0); C is the speed of light (C = 3 * 10 ^ 8 m / s).

Let’s make a calculation: V = √ (1 – (t0 / t) ^ 2) * С = √ ((1 – (t / 2t0) ^ 2) * 3 * 10 ^ 8 ≈ 2.6 * 10 ^ 8 m / s …

Answer: The spaceship relative to the Earth must move at a speed of 2.6 * 10 ^ 8 m / s.