Level B1, Protons, neutrons, electrons Atoms are made of smaller parts, called protons, neutrons and electrons. Protons and neutrons occupy the nucleus at the centre of atoms. Electrons orbit the nucleus in a form of motion that obeys the laws of quantum physics.
Protons carry a positive electric charge, electrons carry an equal but opposite negative electric charge and neutrons are electrically neutral (ie they carry no electric charge).
Neutrons are about 0.1% heavier than protons. Protons and neutrons are 1836 times heavier than electrons. Therefore, nearly all of the mass of an atom comes from its protons and neutrons.
An isolated proton is stable, however, an isolated neutron will spontaneously decay into a proton and an electron within an average of approximately 15 minutes. This process is called beta decay and is responsible for beta radiation (β radiation), which is one of the three forms of ionising radiation (the two other forms are alpha and gamma radiation).
Level B2, Quarks, leptons, bosons Electrons have no known internal parts but protons and neutrons are made of smaller particles called quarks. Electrons are members of a family of particles called leptons. Bosons include the particles that make up visible light and all electromagnetic radiation. These three particle families make up the Standard Model of Physics.
Level B3, Unknown Nobody knows if quarks are made of even more fundamental particles. Therefore, basement 3 level of the model may or may not exist.
Level 6, Earth includes all humans, animals, plants and microbes and the natural and built environment. This level therefore includes all human relationships, societies, politics and economics, ecosystems, weather systems as well as the Earth’s finite natural resources.
Level 7, Solar System includes all the other planets, comets, asteroids and the sun, which provides all of the energy for photosynthesis and weather.
Level 8, Galaxy The sun is just one of 100 billion stars in our galaxy, which is called the Milky Way. Our nearest star is Alpha Centauri, a triple star system approximately 4 light years from Earth (i.e. the photons that our eyes receives from Alpha Centauri departed the system approximately four years ago).
Level 9, Universe Our galaxy is just one of 100 or possibly up to 2000 billion galaxies in the universe.
Level 10, Unknown Nobody knows what, if anything, lies beyond the known universe. Therefore, level 10 of the model may or may not exist. The many worlds interpretation of quantum mechanics holds that there are many worlds which exist in parallel to our own, produced by the bifurcation of our universe every time a quantum event occurs one way, which could have occurred in another way. A different theory called the multiverse hypothesis posits the existence of multiple universes, each with different conditions to our own.
Dark matter and dark energy are not depicted in the model but are believed to make up most of the mass of the universe. Dark matter is believed to make up approximately 27% of the universe. Dark energy makes up a further 68% and everything else, including the Earth and all other planets, stars and space dust accounts for less than 5% of the total mass of the cosmos. Nobody knows what dark matter and dark energy are made of so, for now, the name is best interpreted as an acronym for Don’t Actually Really Know.