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Why do we need a Large Hadron Collider?

Updated Monday, 11th February 2013
If particle collisions like the ones in the LHC (Large Hadron Collider) are happening all the time, then why do we need to build the LHC?

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Large Hadron Collider Large Hadron Collider  Watch this animated video on the Large Hadron Collider

If particle collisions like the ones in the LHC are happening all the time, then why do we need to build the LHC? Cosmic rays are coming in from space all the time, getting trapped in the Earth's magnetic field, and being squirted down to the North and South magnetic poles. You could in principle build a particle detector there, and just sample the collisions that are happening naturally.

The trouble is you won't have any control over the types of particles coming in, so it can be quite hard to set up experiments. This turns out to be an insurmountable problem for the scientific questions that the LHC is there to answer, so the only way is to build the LHC and to do our own collisions.

The naturally-occurring particle collisions can still do something very useful for the LHC: they demonstrate that the LHC particle collisions pose no risk to the safety of the Earth or the Universe. In fact cosmic rays can get to even higher energies than the LHC reach, and they've been hitting the Moon and the Earth and the other planets for billions of years.

The Moon and planets are still there, which is a very strong argument for the LHC's safety. If you take an even wider view the safety looks even stronger. Across the whole Universe, the natural high energy particle collisions are equivalent to 10 million million LHC-like experiments every second. The very existence of galaxies and stars is a very strong argument for the safety of the LHC.


Question: Particle physicists sometimes describe their Standard Model of Particle Physics as "elegant" or "beautiful". Do you think these are words that should be used to describe scientific theories? Are there other theories that you could describe as elegant or beautiful? Share your answers using the Comments facility.

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