# What weight does light have?

**What weight does light have?**

First of all, you have to explain the difference between mass and weight:

When I climb a scale here in Frankfurt, I measure my weight.So I measure the power with which the earth attracts me. However, the scale shows my mass (in kg). The difference is easy to explain: when I’m on the moon, I feel much lighter than on Earth, but my mass has remained the same because I haven’t lost weight.

The question is therefore clearer: “**What mass does the light have?**“

**But to weigh I have to stand still, otherwise the measurement varies.**Physics says: This is the mass of an unmoving object.

**Photons** are the smallest energy units of **light** and lose their existence through the complete energy release to matter.They always move at a constant speed c = 300 000 kilometers per second in a vacuum. And photons, i.e. “light particles”, do not exist at all in peace. **Well, if photons didn’t move, they wouldn’t be photons, of course!**Photons therefore have no resting mass, they cannot be in peace in any system.

Therefore, it is also quite good that photons have no mass, because Einstein taught us with the theory of relativity that no object with finite resting mass can be accelerated to the speed of light.This is because in addition to the resting mass in the theory of relativity, there is also the moving mass, which even increases the faster something travels, i.e. the more kinetic energy has something. And then the mass is infinitely large.

**Attention, now I will confuse you:** Photons, I write, are completely massless.In physics in quantum electrodynamics, the photon belongs to the calibration bosons, as it serves as a mediator of electromagnetic interaction.

The resting mass is the mass that a body has in a reference system in which it rests. ** **The light *always* has waves and particle properties.

However, only either / or! The energy and impulse of the photons thus have a connection with the wave properties of the light.

Each photon has a certain energy and this thus also contains mass – according to the mass-energy equivalence E= mc2 (mass and energy are two sides of a coin) .

Photons therefore have no resting mass.However, a mass can be assigned to a photon. There are several formulas to calculate the mass of photons and go back to the physicist Albert Einstein. A very important finding: The mass of a photon depends on its energy. The following are the formulas with variable names:

Here is:

- “m” is the mass of a photon in kilograms [ kg
- “E” is the energy of the photon in Newton meter [ Nm
- “c” is the speed of light in meters per second [ m/s
- “h” is the Planck effect quantum in Joule-Second [ Js
- “f” is the frequency in Hertz [ 1/s
- “A” is the wavelength of light in meters [ m

**The following applies:**

This mass causes photons to be distracted by gravitational fields and can lose or gain energy.