• Question: I know that lasers can heat things up or cool things down, but can they speed up or slow down objects?

    Asked by Sorrel to Stef, Guido on 6 Mar 2015.
    • Photo: Mariastefania De Vido

      Mariastefania De Vido answered on 6 Mar 2015:

      Excellent question! 🙂

      Yes, they can!

      Actually, when you use a laser to heat up or cool down an object, you are already speeding things up or slowing them down, but on a really tiny scale! Indeed, you are modifying the speed of the atoms making up the object: atoms in an object are constantly in motion and the faster the atoms move, the hotter the object is.
      Laser light shone on an object can increase the energy of its atoms, which start wiggling faster and faster, resulting in an increase in temperature of the whole object.

      The same idea can be used to speed up or slow down things which are much bigger than atoms. For example, scientists are now thinking of using lasers to modify the speed of spacecraft or asteroids. One way of doing this is to direct a extremely energetic laser beam towards the object, causing many atoms on its surface to start shaking so fast that they eventually manage to escape from the object itself at a very high speed. This results in a force which modifies the speed of the object.

    • Photo: Guido Bolognesi

      Guido Bolognesi answered on 12 Mar 2015:

      That is an excellent question indeed.

      Oh yes, they do!!

      That was the idea of the German astronomer Kepler who proposed that reason comets tails point away from the sun is because they are pushed in that direction by the sun’s radiation. In the 19th century, Maxwell demonstrated that this is actually the case and light (like lasers) can apply forces to objects, and thus they can speed them up or slow down.

      I use lasers to move objects (1/20 smaller than human hair) . Lasers can do more than just speed up or slow down objects. They can also precisely move the objects the way you want. It is all about modifying the laser in specific ways with lenses and mirrors so that you can control the position and the speed of many objects simultaneously. However, this only works for very small objects, as I said smaller than human hair. At the moment, unfortunately you can’t you lasers to trap your mobile or the TV remote controller when you are lying on the sofa but you have still to use your hands 🙁

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