Tractor beam



 The beam is emited by a laser source with a opaque material in its center and is composed of  a ring of laser light with a cool dark center and a hot bright circular edge.



The laser ray heats a narrow band of air molecules around the target, but the interior of the laser beam is hollow,  dark and the target remains cold.

Particles remain inside the laser beam as the heated surrounding molecules exert pressure on them.



  During the experiment, heat from resonant absorption with the laser warms up the air around the cool center. The particles absorb heat until their surfaces form hotspots.

 Air particles that run into the hotspots gain momentum and cause the spheres to repel in the opposite direction.

 Their gain in momentum -p is accompanied by an equal gain in momentum +p so that the total momentum is conserved.

 If we make the back of the sphere hotter than the front of the particles, the air molecules push them upward and  they levitate.  By modifying the polarization of the laser beam, we control where the hotspots form.

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<p class="MsoNormal" style="margin-bottom:0in;margin-bottom:.0001pt;line-height: 10.0pt;mso-line-height-rule:exactly;mso-pagination:none;mso-layout-grid-align: none;text-autospace:none"><span style="font-size:12.0pt;font-family:"TimesNewRoman","serif"">

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