When you think of space, you think of emptiness. You probably could not be more wrong. Using the 54km of underground tubes and tunnels that is the LHC we explore the vacuum. In an environment where the air pressure is lower than on the moon, it is quite possibly the best vacuum humanity can produce.
Extremely low energy, but definitely not empty. The vacuum of space is populated by virtual particles which pop in and out of existence on a time scale that is undetectable by our current technology. This odd appearance is allowed by the laws of quantum mechanics.
Energy is also added to the vacuum through the interaction of quark-antiquark pairs (chiral condensate) which contribute mass to particles, which can be thought of as energy. Chrial condensate is something that the LHC is very interested in studying through use of the ALICE experiment.
The Higgs: the fluctuating quantum fields are not the only thing filling the ‘empty’ vacuum of space. The Higgs field is omnipresent and permanent and is thought to be responsible for the mass of all fundamental particles. The Higgs boson is the accompanying particle and would definitively prove the Higgs field if detected.
The energy of the vacuum is something quite different on the astronomical scale, instead of minuscule points of undetectable energy, it becomes the mammoth and unknown dark energy. Current predictions for the expansion of the universe do not hold with new observations and the LHC is hoping to learn some more about dark energy so that we can reconcile our modern observations with physics.
A purely speculative particle, which is presumed to travel faster than light. According to Einstein’s equations of special relativity, a particle with an imaginary rest mass and a velocity greater than c would have a real momentum and energy. Ironically, the greater the kinetic energy of a tachyon, the slower it travels, approaching c asymptotically (from above) as its energy approaches infinity. Alternatively, a tachyon losing kinetic energy travels faster and faster, until as the kinetic energy approaches zero, the speed of the tachyon approaches infinity; such a tachyon with zero energy and infinite speed is called transcendent.
Special relativity does not seem to specifically exclude tachyons, so long as they do not cross the lightspeed barrier and do not interact with other particles to cause causality violations. Quantum mechanical analyses of tachyons indicate that even though they travel faster than light they would not be able to carry information faster than light, thus failing to violate causality. But in this case, if tachyons are by their very nature indetectable, it brings into question how real they might be.