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Myth busted: Copper pennies didn't help our overheating laptop

Our handy-dandy thermal camera helped lay this myth to rest.

Now playing: Watch this: Can copper pennies keep your laptop cool?

Copper is a fantastic conductor, and the top of your MacBook is where the heat likes to party. If you placed some copper coins there, wouldn't that heat go away?

It's not hard to see why that idea became such a popular myth. But we busted it wide open.

The CNET offices had everything we needed for a test:

  • An old MacBook Pro from our video team, guaranteed to overheat
  • A stack of pre-1982 (95 percent copper) pennies scrounged from change piles
  • A borrowed CAT S60 smartphone with built-in FLIR thermal camera
  • A videographer willing to expense a copy of the Temperature Gauge app to see our laptop's internal temperatures
  • A free copy of the Prime95 benchmark to keep our Mac nice and toasty

Without any pennies, we measured 88°F at the laptop's surface, and a blazing 93°C (nearly 200°F) at the core. Clearly, change was needed.

At first, plopping down some copper pennies seemed to cool things down -- by a degree or two. But the thermal camera showed the truth: as the cold coins warmed up, the temperatures shot right back up again.

Here's our theory:

Heatsinks work by spreading out heat over a larger surface area, so more of the surrounding air can carry it away. But the aluminum deck of our MacBook Pro is already a huge surface area -- the pennies are just stacking that heat vertically instead of spreading it out horizontally.

Maybe if you had a ridiculous amount of copper spread out over a far larger surface area, you might have better results. That's what that Japanese Twitter user -- the one credited with the original idea -- is laughingly suggesting now.