Why does the disc glide so far?

• When the valve opens, air from the balloon rushes through the bottle cap and out the hole in the centre of the CD. This creates a thin cushion of pressurised air between the disc and the surface.

• That cushion lifts the CD a fraction of a millimetre off the table. The disc is no longer touching the surface directly.

Friction needs two surfaces in contact to exist. 

• Remove the contact, and friction almost disappears. One gentle push sends the disc gliding with almost nothing to slow it down.

Why does the air cushion work when a regular push doesn't?

• A book pushed across a desk stays in contact with the surface the whole time. Every millimetre of travel involves friction between book and desk.

•  The Ghost Glider's disc is riding on air — the actual surfaces never touch. The friction that would have acted simply has no surfaces to act between.

This is why hovercrafts can travel across water, ice, mud, and land equally well: none of those surfaces matters if you never touch them.

Why does it stops instantly when the balloon empties?

• As the balloon empties, air pressure through the hole drops. The cushion thins. Eventually, the disc settles back onto the surface.

• The moment contact is restored, friction returns — and the disc stops quickly.

Real-world connection

• Real hovercrafts use exactly this principle at a larger scale — a flexible skirt traps a cushion of high-pressure air beneath the hull, lifting the craft above whatever surface it's crossing.

• Maglev trains use magnetic levitation to remove contact with the track entirely, eliminating friction and allowing speeds above 600 km/h.

Try next

For a completely different role for friction — where it actively reverses a direction of travel — see [The Disobedient Hoop]. And in [Newton's Question: Who Moves?], friction against the floor is the only force that can prevent motion on rolling surfaces — which is why a smooth floor is essential for that experiment to work.