Magic Trick Anti-Gravity?

Question

I was at the movies last night to see Inception, great movie by the way... but before the movie starts they have this "Fredo the Magician" guy do a trick. He had a glass maybe 5 inches tall with an opening at the top maybe 3 inches in diameter filled about halfway with ice. He then poured some pink liquid into the glass, one can only assume that it was juice, up to the level of the ice, or halfway up the glass. He then put a card over the top of the glass, turned the glass upside down, and removed the card. The juice did not fall! then he moved his finger near the top of the glass and the juice and ice fell. 

I have seen it done before where the card remains in place, and does not fall, and i understand why that happens. However, with no card, I can see no reason why the juice would stay in the glass. My friends believe that it is capillary action but i disagree because i feel that the ratio of the area of the glass to the mass of fluid being held is not high enough. Some even say that you can get more cappillary action because of the ice, but even there i do not agree, especially because the ice is not fixed to the glass in any way and would only be an internal force in the whole matter. 

The only thing I can think of is that the magician placed some sort of a membrane over the top of the glass using the card, and upon removing the card, the membrane remained in place. Then he removed his finger from the (hole at the top of the glass?) and enough pressure pushed the membrane down. 

Let me know your thoughts on this matter.

Gary B · Accepted Answer

very simple trick!!!!

For liquid to come OUT of the glass, something must move in to replace it -- AIR!  Prevent AIR from entering the glass, the and liquid cannot fall out, even if the glass is upside down.

Near the bottom of the glass is a small hole.  That hole is covered with a small clear plastic "dot", or even by the "magician's" finger (if he held the glass while filling it).

ALSO --- there is a clear plastic cap, hidden the by card.  When he puts the card on the glass, the cap is snapped in place over the glass. [YOU WERE RIGHT!!!!}

Pour liquid in the glass, put on the card (and snap the secret cover into place), put you finger over the small hole (sliding the "invisible" plastic dot away) and turn it upside down.  Since air cannot enter into the glass, the card and cover is held in place by air pressure which is TRYING to get in.  Remove the card but keep the cap, and the liquid "magically" stays in place!

Now, when he moves his fingers he uncovers the small hole drilled in the glass, air CAN enter the glass through the small hole, and the plastic cap, the liquid, and the ice all fall out!

NO capillary action involved!!  All done with simple air pressure (and a SECRET clear plastic cap for the glass).

Anonymous · Answer

You must have been paying really close attention to notice the finger. Either that or it was a bad magician. Usually stuff like that you are supposed to distract the audience from.

And you are right about capillary action. The ice is not fixed to the glass, but neither are the gaps between the ice small enough to get any capillary action.

Soon as I read "moved his finger", I thought that he had to be uncovering a hole. Though I didn't think of using the card to put a clear membrane over the top of the glass, it sounds very reasonable. I think your theory is on the right track.

Anonymous · Answer

your explanation is exactly correct - it will not work without the thin membrane ( cling film) as capillary action/atmospheric pressure  only works on very narrow tubing. My friend is a magician and showed me the trick

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Magic Trick Anti-Gravity?

3 Answers