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What are the four fundamental forces of nature?


Uniting the Fundamental Forces
The magnet core of the Large Hadron Collider might one day unite the strong force with the electroweak force.
The magnet core of the Large Hadron Collider might one day unite the strong force with the electroweak force.
Fabrice Coffrini/AFP/­Getty Images

­Science never rests, so the work on fundamental forces is far from finished. The next challenge is to construct one grand unified theory of the four forces, an especially difficult task since scientists have struggled to reconcile theories of gravity with those of quantum mechanics.

That's where particle accelerators, which can induce collisions at higher energies, come in handy. In 1963, physicists Sheldon Glashow, Abdul Salam and Steve Weinberg suggested that the weak nuclear force and electromagnetic force might combine at higher energies in what would be called the electroweak force. They predicted that this would occur at an energy of about 100 giga-electron volts (100GeV) or a temperature of 1015 K, which occurred shortly after the Big Bang. In 1983, physicists reached these temperatures in a particle accelerator and showed that the electromagnetic force and weak nuclear force were related.

Theories predict that the strong force will unite with the electroweak force at energies above 1015 GeV and that all the forces may unite at energies above 1019 GeV. These energies approach the temperature at the earliest portion of the Big Bang. Physicists are striving to build particle accelerators that might reach these temperatures. The largest particle accelerator is the Large Hadron Collider at CERN in Geneva, Switzerland. When it comes online, it will be capable of accelerating protons to 99.99 percent the speed of light and reaching collision energies of 14 tera-electron volts or 14 TeV, which is equal to 14,000 GeV or 1.4 x 104 GeV.

­If physicists can show that the four fundamental forces indeed came from one unified force when the universe cooled from the Big Bang, will that change your daily life? Probably not. However, it will advance our understanding of the nature of forces, as well as the origins and fate of the universe.