So that means it only took the ship 5.21 days to arrive on Earth (from the spaceship's perspective) ? If so, that means if the spaceship can travel at 99.9999999999999% of the speed of light, it will only takes 1.41 second to arrive on Earth from the spaceship's perspective. It would be almost...
Does time dilation only affect matter that has mass?
For example, A spaceship is 1 light year away from Earth at rest. It sent out a radio wave to Earth then travels at 99.99% of the speed of light. On Earth, from our perspective, we will receive that radio wave 1 year later but the spaceship...