According to the theory of relativity, as an object with mass approaches the speed of light, its behavior and appearance undergo significant changes. However, it is important to note that matter with mass cannot actually reach or exceed the speed of light, as it would require an infinite amount of energy.
As an object with mass approaches the speed of light, its momentum and energy increase dramatically. The equation that describes this behavior is E = mc^2 / √(1 - v^2/c^2), where E is the object's energy, m is its rest mass, v is its velocity, and c is the speed of light.
When an object with mass accelerates towards the speed of light, its energy increases without bound. As the object's energy increases, its relativistic mass also increases. This phenomenon is known as mass dilation. As a result, the object's momentum and the forces acting on it also increase.
Additionally, the Lorentz transformation, which is a mathematical expression in relativity, predicts that as an object's velocity approaches the speed of light, its length contracts along the direction of motion. This is known as length contraction. Therefore, when an object is moving at a significant fraction of the speed of light, it appears compressed in the direction of motion.
As the velocity of an object with mass approaches the speed of light, its time dilation also becomes significant. According to time dilation, as an object's velocity increases, time slows down for that object relative to a stationary observer. This means that the object's internal processes, such as the ticking of a clock within the object, will appear slower from the perspective of an observer.
Now, when we consider matter particles like electrons or protons moving at speeds close to the speed of light, they exhibit behavior that is similar to that of high-energy radiation. This is because their energy, momentum, and relativistic mass have increased significantly due to their high velocities. As a result, they can exhibit properties similar to radiation, such as the ability to penetrate matter or cause ionization.
However, it is important to note that matter particles and radiation (such as photons) are fundamentally different entities. Matter particles have rest mass and obey the laws of quantum mechanics, while photons are massless particles that travel at the speed of light. The behavior of matter particles at high speeds is a consequence of the relativistic effects described by the theory of special relativity.