3 levitation tricks

No magic – just physics!

Safe­ty pre­cau­tions

Warn­ing! This ex­per­i­ment in­volves the use of small mag­nets. Only un­der adult su­per­vi­sion.

Equip­ment

  • par­al­lelepiped neodymi­um mag­nets;
  • graphite plate;
  • sty­ro­foam;
  • CD;
  • cap with valve;
  • bal­loon;
  • hot glue;
  • stove;
  • fry­ing pan;
  • pipette;
  • wa­ter.

Step-by-step in­struc­tions

Fly­ing House: Make a “rug” from neodymi­um mag­nets, ar­rang­ing the poles of neigh­bor­ing mag­nets in a checker­board pat­tern. Put a graphite plate on the rug: it will be sus­pend­ed a few mil­lime­ters above the mag­nets! You can build a foam house on the re­sult­ing "fly­ing foun­da­tion"!

Hov­er­craft: Hot glue a plas­tic cap with a valve to a CD, care­ful­ly seal­ing the joint. Put an in­flat­ed bal­loon on the valve: as soon as it starts to de­flate, the CD be­gins to slide over the sur­face, hov­er­ing above it!

Lev­i­tat­ing droplets: Heat a fry­ing pan to a high tem­per­a­ture and drip wa­ter on it from a pipette: ob­serve how the wa­ter doesn’t spread, but col­lects in droplets that skit­ter over the sur­face and take a long time to evap­o­rate!

Process de­scrip­tion

Fly­ing House: Graphite placed in an ex­ter­nal mag­net­ic field is mag­ne­tized against it. This re­pels the graphite plate from the sur­face of the mag­nets with a force that ex­ceeds the force of grav­i­ty. As it moves up­ward, away from the mag­nets, the force of its in­ter­ac­tion with them de­creas­es, and as soon as this force be­comes equal to the force of grav­i­ty, the plate hov­ers in the air! The poles of the mag­nets are stag­gered to cre­ate a restor­ing force when dis­placed: there is a hor­i­zon­tal com­po­nent to the in­ter­ac­tion with the mag­nets in ad­di­tion to a ver­ti­cal one, and this keeps the plate from fly­ing out of the bound­aries of the rug. The mag­nets thus coun­ter­bal­ance each oth­er hor­i­zon­tal­ly and cre­ate a “trap” for the plate.

Hov­er­craft: As the bal­loon de­flates, in­creased pres­sure aris­es un­der the CD, which lifts it off of the ta­ble. Since the CD is not in con­tact with the ta­ble sur­face, it can slide over it fric­tion­less­ly!

Lev­i­tat­ing droplets: Upon con­tact with a sur­face with a much high­er tem­per­a­ture than the boil­ing point of wa­ter, a droplet forms a va­por lay­er due to the in­stan­ta­neous evap­o­ra­tion of part of it. This lay­er in­su­lates the wa­ter from the hot sur­face, so the evap­o­ra­tion of the re­main­ing droplet is slow­er than if it were in di­rect con­tact with the sur­face. In ad­di­tion, due to the pres­ence of a va­por lay­er, the drop is sus­pend­ed above the hot sur­face, eas­i­ly mov­ing above it in the ab­sence of any re­sis­tance to move­ment.

You can find more cool ex­per­i­ments in the MEL Physics sub­scrip­tion!

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