As an object approaches the speed of light, it will not shrink down to zero size, but it will experience a phenomenon called length contraction or Lorentz contraction. Length contraction refers to the observed decrease in the length of an object in the direction of its motion as measured by a stationary observer.
According to special relativity, as an object's velocity increases towards the speed of light, its length in the direction of motion appears shorter to an observer at rest relative to the object. However, it's important to note that this contraction effect only applies along the direction of motion, and objects retain their sizes in directions perpendicular to the motion.
The magnitude of length contraction can be calculated using the Lorentz factor, which depends on the velocity of the object relative to the observer. The formula for length contraction is given by:
L' = L₀ / γ
Where L' is the contracted length, L₀ is the rest length (the length of the object in its own frame of reference), and γ (gamma) is the Lorentz factor, which is defined as:
γ = 1 / sqrt(1 - (v²/c²))
Here, v represents the velocity of the object relative to the observer, and c is the speed of light.
Regarding the effect of time dilation and length contraction on atoms and molecules, they are both consequences of special relativity. Time dilation affects the passage of time for rapidly moving objects, while length contraction affects the spatial dimensions of objects in the direction of their motion.
In the case of atoms and molecules, their internal processes, such as atomic vibrations or chemical reactions, would be subject to time dilation effects when they are moving at high velocities. However, it's important to note that these effects are typically negligible at everyday velocities and become more pronounced only when approaching relativistic speeds.
Length contraction, on the other hand, would affect the size of objects including atoms and molecules along the direction of their motion. However, the scale of atoms and molecules is already so small that the magnitude of length contraction at typical velocities is negligible and not experimentally detectable.
In summary, as an object approaches the speed of light, its length contracts in the direction of motion, but it does not shrink down to zero size. Atoms and molecules would also experience time dilation and length contraction effects, but these effects are typically negligible at everyday velocities and become significant only at relativistic speeds.