It's important to clarify that nothing with mass can actually travel at the speed of light. This is a fundamental principle of Einstein's theory of relativity.

Here's what travels at the speed of light:

* Light itself: This is the most obvious one. Light, in all its forms (visible light, infrared, ultraviolet, etc.), travels at the speed of light in a vacuum, which is approximately 299,792,458 meters per second.

* Electromagnetic radiation: This includes all forms of light, as well as radio waves, microwaves, X-rays, and gamma rays. These are all forms of energy that travel as waves at the speed of light.

* Gravitational waves: These are ripples in the fabric of spacetime caused by the acceleration of massive objects, such as black holes colliding. Gravitational waves travel at the speed of light.

It's important to note that while we talk about "things" traveling at the speed of light, these are not objects in the traditional sense. They are forms of energy or disturbances that propagate through space at the speed of light.

Regarding engines, there is no known engine that can reach or exceed the speed of light. This is due to the fundamental limits of physics.

Let me know if you have any more questions about light speed!