Einstein's theory of relativity says that nothing can travel faster for the speed of light. Is this still true?

Physicists at the CERN and Gran Sasso laboratories have made a startling discovery - they measured neutrinos travelling faster than the speed of light!

What's a neutrino?

Neutrinos are tiny subatomic particles produced by reactions in the Sun. They hardly weigh anything, they don't have an electric charge and they can travel through solid objects as if they weren't there. Billions of neutrinos are flowing through your body right now, without you noticing.

So what if neutrinos can travel faster than light? Does it really matter?

It matters to physicists and it will matter to us too. Light travels at an incredible billion kilometres per hour. According to Einstein's theory of relativity, nothing can travel faster than light. This speed limit gives us causality: causes always come before their effects. If I knock a cup of tea over, the cup will fall and then the tea will spill. The tea won't spill out before the cup of tea is knocked.

If you remove the light speed limit, time could become much more fluid and, frankly, weird. It won't be one-directional like we think it is now. Time travel could be possible, just like in Back to the Future!

Could your computer solve a problem before you'd even asked it to?

The speed of light limit is also important for computers and the internet. What if information could travel faster than light? Could your computer solve a problem before you'd even asked it to?

Can neutrinos really travel faster than light?

Many scientists are sceptical. Even the scientists who carried out the experiment are cautious about their findings. They are repeating their experiments and testing for every possible source of error. Professor Jim Al-Khalili, a physicist and TV presenter, has said that if neutrinos really can travel faster than light, he will eat his shorts live on TV.

What else could explain the results?

Physicists are repeating the experiments to make sure the results are not due to experimental error. If it's not an experimental error, what could have caused the results?

This is where it gets really strange. Some scientists believe that extra dimensions could be responsible. Neutrinos could have taken a 'shortcut' through extra dimensions of space and appear to arrive faster than light. This would mean that neutrinos don't actually travel faster than light. Instead, they take a crafty shortcut through a dimension that scientists haven't found yet. Weird, right?

If neutrinos can take a shortcut, could we take a shortcut through space?

If there are extra dimensions in space, this would mean that the wormholes loved by sci-fi writers could potentially exist. We could use these to travel from one place in space to another place millions of light years away!

To find out more about the experiment, read the BBC's article Light speed: Flying into Fantasy.