Poltergeist in a glass?

Since I drink in bars frequently, I have seen this phenomena before. Think gravity and a super slick surface.

Beer. It's not just for breakfast anymore!

I guess that's one explanation. I went the more complicated way and gave this explanation.

The glass has a curved underside, creating a pocket of air as the water pools around the glass. When the water reaches the depth where the air starts to push up the glass, the glass will float and magically slide along the surface until the surface either gets shallow or the air pocket leaks and the glass sinks back to the table top.

'Seemed logical at the time.

I think conditions come right for the glass to sit on a film of water that acts as a bearing. I've seen this myself, if you touch the glass, you can feel there is very little friction.

In addition, as the glass warms up, the pocket of air under the glass expands, lifting the glass enough to overcome the static coefficient of friction between the bottom of the glass and the water-slicked table.

Yep, I could'nt agree more!

Definitely the hover craft thing going on here.

Curved underside, trapped, expanding air and water providing the seal.

This sounds like...and would likely have made a good..."Challenge Question"

You have all the right pieces of the correct explanation here, by the way. Good post to think about. Too bad the condensate can't be resupplied down the glass at the rate that it is lost to the table, so it could keep going (at a speed below that which would entrain any of the air)!

Also, this happens more quickly when a drink has been taken, reducing the weight of the glass, and the glass is replaced onto an existing ring of water. As the glass is placed down vertically, it contacts the water at a raised elevation and traps more air than when it was first placed onto the dry table. The water seal allows the glass to compress a bit of the air, which produces a bit of upward force with which to start.

That's only true if the glass is set on a water ring, and not on pooled water.

Maybe not. If the underside of the glass is concave, it could still trap some air.

You're right about the question being a challenge. I realize that now.

I often wondered if the pool of water had spread evenly around the table. Would the glass float around, sailing from port to port like it had a mind of its own? I think it would!