The statement that matter and energy cannot be created or destroyed, known as the law of conservation of mass-energy, is a fundamental principle in physics. However, when discussing objects approaching the speed of light, we need to consider the principles of special relativity, which introduce some counterintuitive effects.
According to special relativity, as an object with mass accelerates and approaches the speed of light, its relativistic mass increases. This increase in mass is often referred to as "relativistic mass" to distinguish it from the rest mass, which is the mass of an object at rest. The formula that relates relativistic mass (m) to rest mass (m₀) and velocity (v) is given by:
m = m₀ / sqrt(1 - v²/c²)
In this formula, c represents the speed of light in a vacuum. As the velocity of an object gets closer to the speed of light, the denominator of the equation approaches zero, resulting in an infinite mass. However, it's important to note that this is a mathematical result and doesn't imply that the object actually becomes infinitely massive.
The increase in relativistic mass is a consequence of the equivalence between mass and energy in special relativity, expressed by Einstein's famous equation E = mc². As an object accelerates, its kinetic energy increases, and this increase in energy is equivalent to an increase in mass.
It's crucial to understand that the conservation of mass-energy still holds true in these scenarios. The increase in mass-energy of an object as it approaches the speed of light is accounted for by the conversion of kinetic energy into mass-energy, satisfying the overall conservation principle.
In summary, the mass of an object doesn't increase in the traditional sense as it approaches the speed of light. Instead, its relativistic mass increases due to the equivalence between mass and energy described by special relativity. The conservation of mass-energy is still respected, as the increase in mass is accompanied by a corresponding increase in the object's energy.