Here on Earth, driving speed is as simple as watching the world go by. But when flying over an ocean, you’re just a stationary speck. Now imagine the vastness of Mars: no trees or cows, not even GPS. How do astronauts measure velocity? They use physics.

Speed and velocity are key concepts. Speed measures distance over time, but it doesn’t account for direction. Velocity does: speed in one specific direction. A bumblebee's path is a perfect example—its actual motion changes constantly, making it tricky to calculate its true velocity without breaking down the journey into tiny segments.

In space, reference frames matter. For instance, when pedalling a bike on a moving cruise ship, your speed depends on whether you’re heading east or west. The same applies to spacecraft: using Earth as a reference can be misleading during lunar landings. Instead, the moon itself serves as a more practical frame of reference.

A popular method for measuring velocity in space is the Doppler effect. Just like trains sound different as they approach and recede, so do light waves from moving objects. By comparing the frequency changes of radio signals bounced off spaceships, astronauts can pinpoint their exact speed. This technique is reliable because it’s not affected by Earth's atmosphere.

The universe has no stationary reference point; everything moves relative to something else. So while physics offers solutions, the journey through space remains a complex dance of motion and mathematics.