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Open A Beer Bottle With A Magnet - An Instant Internet Hit... That's Likely Fake

by Eric Hall

February 15, 2014

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Donate This week a viral video made the rounds showing a guy demonstrating how to open a bottle of beer with simply a rectangular refrigerator magnet and a quarter. It seemed like most people either accepted it as truth or tried to debunk it with their own tests (hint: it didn't work). No one seemed to tackle the plausibility nor the hints within the video itself that would make it very likely fake.

First, go ahead and look at the video if you'd like:

Let's first tackle the plausibility. Go ahead and take one of your fridge magnets and pull it a few centimeters away from the fridge. Let go of the magnet. Does it stick to the fridge or does it fall to the floor? The magnetic field drops off approximately as 1/r^3. A magnet with the strength of a fridge magnet is unlikely to have any effect on a bottle cap that is at least 20 cm away.

If we were to assume the magnet was strong enough to have an effect on the cap, there is another issue. Because the cap is not magnetized, the effect would be to attract the ferromagnetic material, thus holding it on the bottle, not launching it off.

Would the magnet have an effect on the contents of the bottle? Well, beer is mostly water. While water is a dipole, it takes a pretty strong magnet to have any effect on the water to the point it would be noticeable. Same with the carbon dioxide. A quick look at the research on water and CO2 in magnetic fields show it would take at least 3 orders of magnitude more than the magnet used in the video.

Another clue it is fake is the expulsion of some kind of cloud of material from the bottle when it opens. When you open a bottle of beer, you might notice that a fog forms in the neck of the bottle. This is because the reduction in pressure causes an adiabatic expansion and cooling, which condenses the water vapor into a fog. But it doesn't shoot out of the bottle because it is cooler than the surrounding air. Certainly a little spray comes out, but I haven't ever witnessed a vapor come out like in the video, and unless the beer was very warm or the contents were not beer, the physics make it unlikely it would happen as in the video.

The tapping of the quarter on the side also does not make sense from a physics perspective. We've all clanked our bottle together and nothing happens. The bottles get shook around during transport and nothing happens. While it is true when the bottle is open if someone clanks the top of the bottle you get a beer volcano. This is due to a quick impulse causing the carbon dioxide bubbles to explode upward and gather more CO2 into a foam. But clanking the side does not have the same effect. The quarter tapping doesn't have physics on its side.

The magnet and the quarter are not related. US quarters are not magnetic. Anyone who has ever used a coin counter kiosk or in a bank would know there is a magnet in the machine to catch other currencies while the US coins go past it without being caught. Also, the distance from the magnet and quarter would negate any effect even if the quarter were magnetic.

A non-science clue is in the video production itself. The camera pans left before the top even pops off. If the top really was a pop top and not a twist top, there would be no way to predict which way the top was going to go. Why set the bottle on one edge of the counter while having the camera pan the other way? One could argue that it is the direction of the quarter tapping that did it, but the alignments are just a bit too perfect to be real.

The other non-science clue is the way the bottle was handled after it is opened. It is hard to know for sure if the angle the bottle is held at would cause some to spill out, but it seems like at least a little would have come out. Also, if I actually came up with a cool demonstration for opening an IPA, I think I would celebrate with a nice long pull off the bottle. Why not take a drink?

It would seem this is a pretty simple case of a manufactured viral video. Various searches show several people trying it with no success. I even found a discussion saying the person in the video is known to produce these type of trick videos simply to create buzz, and that for the most part turn out not to be true. As usual, be wary of what you see on the internet, especially from unknown sources. Bonjour!

by Eric Hall

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