* Electromagnetic Radiation: In this case, the fastest ray is light, specifically gamma rays. These are the highest-energy form of electromagnetic radiation, and they travel at the speed of light in a vacuum, which is approximately 299,792,458 meters per second.
* Cosmic Rays: These are high-energy particles that travel through space. While they aren't "rays" in the same way as light, they are often called "cosmic rays." The highest-energy cosmic rays recorded are thought to travel close to the speed of light, but they aren't quite as fast as light itself.
* Other Types of Rays: Other types of rays include alpha, beta, and neutron rays, all of which are emitted during radioactive decay. These particles travel at speeds much slower than light, typically a significant fraction of the speed of light.
So, the answer to your question really depends on what you mean by "ray." If you're referring to electromagnetic radiation, the fastest is gamma rays. If you're talking about cosmic rays, the fastest ones travel at speeds incredibly close to the speed of light.
