June 15, 2010
Is the World Cup Trophy Hollow?
Thirty-two football (soccer) teams from around the globe are battling it out in South Africa this month for the World Cup. The trophy isn’t a cup, though. It’s a gold statue of a man holding up a globe. The trophy’s creator, Italian artist Silvio Gazzaniga, described it:
The lines spring out from the base, rising in spirals, stretching out to receive the world. From the remarkable dynamic tensions of the compact body of the sculpture rise the figures of two athletes at the stirring moment of victory.
The FIFA World Cup trophy (via wikimedia commons)
FIFA says that the trophy is 36 centimeters (14.2 inches) tall, weighs 6175 grams (13.6 pounds) and is made of solid 18-carat gold with two layers of malachite at the base. However, University of Nottingham chemist Martyn Poliakoff, in the video above, says that there is no way that the trophy could be solid gold. If it were, he says, it would weight 70 to 80 kilograms (154 to 176 pounds) and be far too heavy for a member of the winning team to lift over his head in celebration of a tournament win.
Gold is very dense: think of any heist movie in which the criminals are making off with gold bars and you should remember them straining under the weight if they were lifting more than one at a time. A standard gold bar is 400 ounces (25 pounds) and only 7.8 inches long. The gold in the World Cup trophy will be lighter—18-carat gold is only 75 percent actual gold; pure gold is too soft to be used in a statue—but will still be very heavy. A statue more than a foot tall would have to weigh at least as much as one gold bar, if not more, I would think.
Poliakoff suggests that the globe section of the statue, despite FIFA’s claims, is actually hollow, like a chocolate Easter bunny. What do you think?
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why dont the scientists just ask the sculptor?
Eureka!
It’s easy to approximate. Construct an outline from a photo, scale it to the known height, measure the width at regular intervals (I took 5mm apart) and treat it like a lot of disks. Add them all up and it’s going to be of the right order (it’s not a round section of course, so it tends to overestimate the volume). I get a figure of about 3,660 cubic centimetres. 18 carat gold comes in a range of densities according to what it is alloyed with, but the average of the range is 15.55 gm/cubic centimetre, which yields a weight of 57Kg. A bit less than the professor’s calculations (maybe he used the density of 24 carat gold which is 19.32 gm per cubic centimetre which would have produced about 70Kg). There’s a few other adjustments that I could have made, but it is certainly impossible that it is solid gold if it only weights about 5Kg.
In fact I can estimate the wall thickness (if it is roughly the same) and I make it a bit under 3mm thick. It wouldn’t be sufficient for the ball at the top to be hollow, the lower part would weight considerably more than 5Kg on its own. It is conceivable that the hollow space is filled with wax or something similar to provide a bit more rigidity.
In fact this would be a jolly good puzzle to give a class of kids to see if they can work out how much something like this would weight if solid.
Nb. I’ve no idea why I typed the noun “weight” consistently in place of the verb “weigh”.
Actually I had no idea about actual weight of FIFA World Cup Trophy.