(Courtesy to Microsoft Encarta for these photographs.)

After the Universe's period of inflation, many different kinds of particles were created. This was caused by the huge amount of energy released. Particles could be made suddenly and then those particles would "decay" and create some other type of particle. Most of these particles are not around today, but we can recreate them in a particle accelerator. All of these particles are smaller than an atom, so they are usually called subatomic particles. Subatomic particles can be grouped into different categories: hadrons (strong force), leptons (electromagnetic and other weak forces), and bosons (particlelike objects that have to do with different interactions). All particles however also have antiparticles. Antiparticles are have the same mass as its particle counterpart, but it either has a different charge or different electromagnetic property. All of this happened when the Universe was only ten billion trillion trillionths of a second old.

During this stage of the Universe's life, there were equal amounts of antimatter and matter. When the two opposite particles met up, they would annihilate each other. This created more radiation that sparked even more particle births. By the first second of its life, the Universe had only matter. Scientists think that the larger particles "decayed" into smaller particles. This was true on both the matter and the antimatter particles. Particles decay into smaller particles because the larger particles are unstable. For example, the X-boson, the heaviest subatomic particle, and its counterpart, the anti-X boson. They decayed into both particles and antiparticles but for each 100 million particles, there were only 99,999,999 antiparticles. Even though this was a tiny imbalance, it created all of the matter in the Universe.

When all of the larger particles were unstable and started to decay, the smaller particles stayed the same. Even lightweight leptons and quarks decay too. There are six types of leptons and quarks. The leptons include the tau, muon, and the electron. All of these leptons have their own neutrino named after them too. Quarks include the top, bottom, charm, strange, down, and up quarks. The tau and the muon are unstable and they decay to become electrons and neutrinos. All neutrinos are stable. The top, bottom, charm, and strange quarks eventually decay to become the down and up quarks.

All of the four forces that we know today used to be subatomic particles. Scientists believe that all forces used to be one large force until they split into the four forces: gravity, the strong force, the electromagnetic force, and the weak force. Gravity used to be carried by gravitons, the strong force was carried by gluons, and photons convey the electromagnetic and the weak force. Gravity, the weakest, affects all types of matter, and the strong force is inside of the nucleui of atoms. The electromagnetic force and the weak force grow stronger as the amount of energy increases, while the strong force grows weaker. All of this is known as the Grand Unified Theory.

In atoms, there is always at least one electron circling the nucleus. The nucleus is made up of protons and neutrons. Protons are made up of two up and one down quark. Neutrons are made up of two down and one up quark. Protons are positively charged, while neutrons have no charge at all. Neutrons by themselves are unstable, so they started decaying also. One neutron would equal one proton, one electron, and a neutral antineutrino. These neutrons and protons then made the atoms of the kinds of elements we see today. Three minutes after the Big Bang occurred, the first elements appeared. They included hydrogen (one proton nucleus), hydrogen-2 or deuterium (one proton and one neutron nucleus), helium-3 (two protons and one neutron nucleus), helium-4 (two protons and two neutrons nucleus), and lithium (three protons and four neutrons nucleus).

Name of Particle	Image*	Information
Cosmic String		A thin strand of energy that is theorized by some scientists. It may have started some galaxies, and it can be light-years long.
Gluon		Gluons carry the strong force and it ties together the quarks in the nucleui of atoms.
Graviton		Gravitons are theorized to carry the force of gravity.
Higgs Boson		A heavy particle that is theorized to give particles mass. It is named after Peter Higgs, a British physicist.
Magnetic Monopole		Large particle with one magnetic pole. It is thought to determine the charge of other subatomic particles.
Neutrino		Neutrinos are leptons and are the second most common particle in the Universe. They could make up the dark matter in the Universe.
Primordial Black Hole		Stephen Hawking, a British physicist, theorized that there were many primordial black holes created in the Big Bang. It weighs as much as a mountain, but it is only the size of an atom.
Photon		Photons are the most common particle in the Universe. They carry radiation, light, and the electromagnetic force. Photons do not have any mass.
Quark		Quarks build up the neutrons and protons. There are six known types or "flavors:" Top, Bottom, Charm, Strange, Down, and Up.
WIMP		Large particles that may make up most of the dark matter of the Universe.
W & Z Boson		Particles that convey the weak force. W and Z bosons have mass.
X Boson		X bosons have the power to change leptons into quarks and quarks into leptons. They are the heaviest kind of subatomic particle.

*=These pictures are not the correct size and the correct color.
Click here to continue on to the next lesson (Inflation Theory).
Click here for a printable version of this page.