There are some people who think crop circles are made by aliens.

The nearest planet likely to support life is 13 light years away. At the speed of light - 186,000 miles per second - a space ship would take 26 years to make the return trip.

There would have to be three complete crews for the eight-hour shifts daily (union rules) and the ship would have to carry all the power, food, water and oxygen they would need.

Crew numbers would be gigantic as it takes Nasa 100,000 technicians just to get the Challenger space shuttle into orbit.

A 26-year trip would take many times that, say 500,000, so the spaceship would be about the size of the Isle of Wight and would include a hospital, creche and school (for children born during the trip).

It would also need radar capable of detecting objects on its flight path 1,000,000 miles ahead that would atomise it if it collided with them.

The ship would have to carry a very powerful radio to communicate with its base.

It would take 13 years for signals to reach base from Earth and another 13 years for the reply to be received. No radio signals have ever been received from space. So, do you still believe aliens make crop circles?

-Doug Streeter, Brighton