Does light and darkness have mass?

There is a simple question in physics but not all of us know: 'Is light light and if so, how much is it?'.

Light is a miracle, it helps us to see everything, it is the electromagnetic radiation whose wavelength lies in the visible spectrum of the naked eye. In the daytime, we can see light everywhere, it is an indispensable part of life. Scientists have devoted a lot of effort to studying light, its nature, along with special applications such as solar energy or photosynthesis.

To answer this question, we first need to know which light is made up of the movement of photons, and especially that the photons are massless. Thus we can easily conclude that light has no mass.

However, everything is not that simple, because photons are massless but they have energy. And according to Einstein, E = mc2; energy is equivalent to the mass of an object multiplied by the square of the speed of light. So how photons can have energy while its mass (m) is zero.

Actually what Einstein wants to prove is that energy and mass are interchangeable. Light may not have constant mass - the weight describes the weight of an object. However, according to Einstein's theory, we can conclude that: energy and mass coexist.

In fact, scientists have shown that light is affected by gravity . That is when light is bent when approaching the Sun, as well as the light being swallowed by the black hole of the universe. Only weighted objects are affected by gravity (according to Newton's gravitational formula, F = GMm / r2).

In this case the scientists call it the relative mass, the mass when an object moves. Thus, we can understand that light itself has no mass, it only has relative mass when moving (understood to be equivalent to energy). It should be noted that light is the movement of photons, so light is always moving and it also means that it always has a relative mass.

So light does not move without mass, while light with photons that do not move will not produce visible and synonymous radiation to the dark. So we can draw the conclusion that darkness has no mass , it has no relative mass, darkness is nothing. It could be imagined that if a box could contain light and a box containing darkness, the box containing light would be heavier.

But how much is the light? Scientists have yet to give an exact number. However, moving light has energy, relative mass, which also means that it acts on the object it hits. Scientists have measured this interaction force of light. And the result is 1 square inch (about 6.5cm ² ), this force is 1 / 500,000kg. If we count on a larger area we will have a more interesting figure. For example, on a sunny day in the city of Chicago, the entire city suffers from a pressure of about 140kg from sunlight.

Reference: howstuffworks, io9, wiki