For humanity to survive in the long term, energy consumption must be balanced with the planet's resources and technological limitations. The fundamental laws of physics allow for an almost limitless source of energy – the nuclei of light chemical elements. When smaller nuclei combine to form larger ones, a tremendous amount of energy is released in the form of heat, but to start and maintain this fusion reaction, a temperature of millions of degrees and the pressure to hold the matter together for a long enough time are needed. In nature, such extreme conditions occur in stars.

It is the fusion of hydrogen nuclei that powers the Sun and thus indirectly drives all the renewable energy sources on Earth. Nuclear fusion energy has two major advantages: virtually inexhaustible fuel resources and a neutral impact on the climate.

Turning the principle of nuclear fusion into a practical and widely available technology is a major scientific and engineering challenge that tens of thousands of researchers around the world have already been working on for a long time. Their task is the mission of Prometheus – to bring down the spark of the Sun from the heavens to serve people. The Treaty of the European Atomic Energy Community is one of the oldest European cooperation frameworks. Latvian scientists also participate in it with their contribution to the creation of the prototypes of the world's largest nuclear fusion reactors – ITER and its successor DEMO.

The coin depicts the particles involved in the hydrogen fusion reaction. The beads represent elementary particles that make up nuclei: the small silver hollows are neutrons, while the gold-plated beads are protons. Hydrogen nuclei with one proton are the raw materials, while a helium nucleus with two protons and a free neutron are the products of the fusion reaction.

In stars the conditions for nuclear fusion are ensured by a strong gravitational field, while in nuclear fusion reactors, the hot plasma is held together by special magnetic fields. The arrangement of lines on the coin resembles both the magnetic fields of large space objects and the stylised cross-section of a toroidal fusion reactor – the so-called tokamak. The relief of the coin with a recess in the centre also echoes the gravitational potential near a star or the black hole.

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