Which type of waves can travel through a vacuum?

Electromagnetic waves are capable of traveling through a vacuum because they do not require a medium to propagate. These waves can move through the empty space that exists between planets and stars, which is why we can see light from distant celestial bodies. Electromagnetic waves, such as light, radio waves, and X-rays, are fundamentally different from mechanical waves, which require a medium (like air, water, or solid materials) to travel through.

In contrast, mechanical waves, including both transverse and longitudinal waves, cannot travel in a vacuum because they rely on the movement of particles in a medium to transmit energy. Transverse waves, such as waves on a string, move perpendicular to the direction of wave propagation, while longitudinal waves, like sound, move parallel to the direction of propagation. Both types need a physical medium to compress and expand, which is why they cannot exist in a vacuum.

Therefore, the ability of electromagnetic waves to propagate through a vacuum distinguishes them from other types of waves, making them the correct answer.