CERN Accelerating science

Alvaro De Rujula as seen by the CERN student Alexei Sergeev

A few questions to Alvaro and Rolf:

What is matter?
What is antimatter?
Where is antimatter gone?

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What are particles?

Rolf Landua as seen by the CERN student Alexei Sergeev

How do we make antimatter?

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CERN physicists Alvaro de R�jula and Rolf Landua answer your most frequently asked questions.

� What can antimatter be used for?
There are several different uses for antimatter, the main one being for medical diagnostics where positrons are used to help identify different diseases with the Positron Emission Tomography (or PET scan). For other uses, we are still in the first phases of development and it's difficult to foresee what will happen in the next ten years!

� Can we use antimatter to propel a car or a spaceship?
In principle, yes, but in practice it is very difficult. You all know that the Star Trek Spaceship Enterprise flies around powered by antimatter. But in reality, making antimatter is so difficult that it is hard to foresee it ever being used as a propellant fuel. In order to propel a matter spacecraft weighing several tons up to the speed of light, you would need an equal amount of antimatter and, using the present technology, it would take millions and millions of years to produce a sufficient amount.

However, if you had a gram of antimatter, you could drive your car for about 100.000 years!

� Is it possible to build an antimatter weapon?
The military use of antimatter has the same limitations as spaceship propulsion: both would require a huge amount of antimatter, taking million of years to produce.

But if you define a weapon as something which shoots bullets, an accelerator could be considered an antiparticle gun! But we are talking about single particles, so the amount of energy you release when you shoot one of these "bullets" is so small you wouldn't even tickle your enemy.

� How do you store antimatter?
Antiparticles have either a positive or a negative electrical charge, so they can be stored in what we call a trap which has the appropriate configuration of electrical and magnetic fields to keep them confined in a small place. Of course, this has to be done in good vacuum to avoid collisions with matter particles.

Antiatoms are electrically neutral, but they have magnetic proprieties that can be used to keep them in "magnetic bottles".

� What does antimatter look like?
Matter and antimatter are identical. Looking at an object means seeing the photons coming from that object; however, photons come from both matter and antimatter. If there were a distant galaxy made out of antimatter, you couldn't distinguish it from a matter galaxy just by seeing the light from it.