# Can matter be created from energy

## Column: Five minutes of physics: matter becomes energy

When protons soon collide head-on in the new LHC particle accelerator in Geneva, each almost at the speed of light, energy densities will be created such as those last prevailed during the Big Bang. The kinetic energy of a single proton in the LHC only roughly corresponds to that of a fly buzzing around - even if this is already a respectable energy for a single elementary particle - but in fact significantly more energy is released when two protons collide than when two collide Houseflies.

When two protons crash, the entire mass of the two particles can be converted into energy. It was Albert Einstein who discovered the equation with which this conversion of matter into energy (E) can be described: E = mc *, where the symbol c stands for the speed of light. If one substitutes the mass of two protons for m and multiplies this by the square of the speed of light, the result is the energy that is released in the smallest of spaces and leads to a huge energy density.

The fact that the mass of the protons circling in the LHC is almost 7500 times greater than that of a proton at rest is then of little importance. According to the general theory of relativity, also formulated by Albert Einstein, it is the case that the mass of particles - i.e. of matter of all kinds - increases with their speed. The ratio of the speed of particles to the speed of light appears in the corresponding formula. If one were to use the value c as the particle speed, the result would be an infinite value for the mass of the particle in purely mathematical terms. Since there cannot be particles with infinite mass and thus infinite energy, it follows from this that no material object can ever reach the speed of light. It is a barrier that is only broken in science fiction, where spaceships like to jet through space at multiples of the speed of light.

At most, light can travel at the speed of light, as the name suggests. If you consider light as particles, as photons, then it applies to them that they have zero rest mass. Due to its nature, light is forced to always hurry at the speed of light. But there is no resting light. On the other hand, Einstein's formula can also be used to assign a mass to a light quantum.