Question: Could we use light to move bigger things in the future rather than atoms and cells?

Susan Skelton answered on 13 Nov 2013:

Hi callumh and u12hillc!

This is a brilliant question, because it is exactly what scientists are trying to do! The answer is both yes and no, depending on what exactly you want to do …

It is quite easy to move very small things. They are not very heavy so we don’t need to use a lot of force to pick them up. But big things are usually much heavier: we need to use a lot more force to pick up a whole person than just a single cell!

So for us to get our light to produce a strong enough force to move bigger things, we need to make the light beam much stronger. But if the light beam was strong enough to move a person, the light would be so strong that it would set the person on fire and fry them!! This is probably not what we want (!) so unfortunately, although I would personally love to be able to pick up a person or a car, this will probably not ever be possible.

On the other hand, if we don’t need to hold something very precisely and are happy to just push it along, then things are much more promising! Actually this is exactly what is done in space to fly space rockets through space!

How does this work? Well, light particles, which come from the sun and other stars, bounce off very large mirrors attached to the spacecraft. As the light particle bounces off the mirror, the spacecraft is pushed forward through space, in the same way as the white cue ball on a snooker table pushes the coloured balls in to the pockets.

By using just light from nearby stars, spacecraft can fly on for ever without needing to stop for fuel! Pretty cool, huh?!