The concept of mass increasing as an object's velocity approaches the speed of light can be a bit counterintuitive, but it arises from the theory of special relativity. According to Einstein's theory, the mass of an object is not a constant but depends on its velocity.
To understand this intuitively, let's consider a thought experiment using a hypothetical object, such as a spaceship. As the spaceship accelerates and approaches the speed of light, we'll observe some interesting effects.
Time dilation: According to special relativity, time runs slower for objects moving at high speeds relative to an observer at rest. As the spaceship accelerates, time dilation occurs, and the onboard clocks appear to tick slower from our perspective. This means that the time experienced by the crew on the spaceship is different from the time experienced by an observer on Earth.
Energy and momentum: As the spaceship accelerates, it gains kinetic energy. According to special relativity, the total energy of an object is given by the famous equation E = mc², where E represents energy, m represents mass, and c is the speed of light. Since energy is related to mass, an increase in energy also implies an increase in mass.
Relativistic momentum: When an object moves at speeds much lower than the speed of light, we can use the classical formula for momentum, p = mv, where p is momentum, m is mass, and v is velocity. However, when an object's velocity approaches the speed of light, we need to use the relativistic momentum formula, which is p = γmv, where γ (gamma) is the Lorentz factor given by γ = 1 / √(1 - (v²/c²)). As the velocity approaches the speed of light, γ becomes larger, and this causes the momentum to increase. Since momentum is related to mass, an increase in momentum implies an increase in mass.
In summary, as an object's velocity approaches the speed of light, its mass appears to increase due to the effects of time dilation, increased energy, and relativistic momentum. These effects are consequences of the fundamental principles of special relativity.