Why so much voltage? history 5
 Energy and mass One reason for using such large amounts of energy is to try to turn that energy into the mass of new particles. At the beginning of the twentieth century, Albert Einstein showed that mass and energy are equivalent and are related by the equation E=mc2. Energy into mass

M4e
 When two particles crash into each other, they will break up and often form new particles. Amazingly, the new particles can sometimes have a bigger mass than the crashing particles. This is because some of the energy of the collision has become part of the mass of the new particles. This is rather like firing two eggs at each other and producing a three-egg omelette (the combined kinetic energies of the eggs would have to be enormous – equivalent to the mass of an extra egg multiplied by the speed of light squared – about 1016 joules). Increasing the energy
 By increasing the energy of the colliding particles, the allowable mass of the products can be increased. So, in the egg analogy, if the energy of the eggs is doubled, then it would be possible to produce a four-egg omelette. This is important for physicists looking for new particles that have a large mass. They can increase the energy of the colliding particles to match it to the mass of the new particle that they are looking for.
 Temperature of soup Also, by increasing the energy of the particles, physicists are trying to recreate the conditions that existed in the early seconds of the Universe, soon after the Big Bang. At this time there was an extremely hot and very dense soup of particles, called the primordial soup. The temperature of this soup meant that the particles had an enormous kinetic energy. The high energy collisions at this time produced lots of new particles. It is these conditions and these particles that physicists are now trying to make in accelerators. This will help them to understand the beginnings of the Universe.
The story so far
 • In a high energy collision, some of the energy is turned into extra mass of new particles • The higher the energy of a collision, the bigger the possible mass of particles after the crash • Particle accelerators can represent the sort of energies that particles had right at the beginning of the Universe
 Question H5

a) What are the two reasons for using higher and higher energies in particle collisions?

b) Why is it more difficult to find new particles if they have a large mass?

c) The law of conservation of energy says that the total energy in the Universe is aconstant (energy cannot be created or destroyed). How does this tally with the idea that particles can annihilate each other and release energy?

 The story so far Linear accelerators and synchrotrons are used to probe into the make up of tiny particles Scientists are constantly aiming to use bigger accelerators and synchrotrons