* Einstein's Theory of Relativity: The theory states that as an object approaches the speed of light, its mass increases infinitely. This means that the amount of energy required to accelerate it further also increases infinitely.

* Energy and Mass: The famous equation E=mc² tells us that energy and mass are interchangeable. As an object accelerates, it gains energy, and that energy translates into increased mass.

* Infinite Energy: To reach the speed of light, an object with mass would require an infinite amount of energy, which is impossible to achieve.

What Happens Instead?

* Approaching the Speed of Light: Objects can get incredibly close to the speed of light, but they will never actually reach it.

* Time Dilation: As an object approaches the speed of light, time slows down for it relative to a stationary observer. This is called time dilation.

* Length Contraction: The length of an object in the direction of motion also appears to contract from the perspective of a stationary observer.

In Summary:

It's impossible for an object with mass to reach the speed of light. Instead, it experiences relativistic effects like time dilation and length contraction as it approaches this speed.