How can light travel in an empty space?

All electromagnetic waves, and only they and gravitational waves, can travel in a vacuum at the speed of light, 300,000 kilometers per second, because they have no mass. In a vacuum, any electromagnetic wave, including light, could travel in a straight line forever and at that speed.

Explanation:

Light is an electromagnetic wave, that means it is made up of an electric field and a magnetic field that oscillate with a certain frequency. This oscillation propagates, travels, and that causes it to have a spatial periodicity that we call wavelength and which is, together with frequency, what characterizes electromagnetic ones. Light can propagate in a vacuum or in other media. The speed at which it propagates depends on the medium. In a vacuum (or in air) it is 3 · 108 m / s; in any other medium its value is less. This speed is given by a quantity called the index of refraction, n, which is the relationship between the speed of light in a vacuum and the speed in that medium. Light does not transport matter in its movement, it is made up of electromagnetic waves, consisting of an electric field that varies over time, generating a magnetic field and vice versa. Variable electric fields generate magnetic fields and variable magnetic fields generate electric fields. In this way, the wave propagates indefinitely through space, with magnetic and electric fields continually regenerating. Electromagnetic waves transmit energy even in a vacuum. What vibrates in its path are the electric and magnetic fields that they create to spread. The vibration can be captured and that energy absorbed.

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