Despicable Science Part 1: Freeze Ray
What's the science behind Gru's freeze ray in Despicable Me? Is such a device possible? Everyday Einstein investigates.
A few nights ago, my children and I were watching one of our favorite movies, Despicable Me. The main character's favorite weapon to use against his opponents is the freeze ray. Whether he uses it against rival villains or the people in front of him in the checkout line, the freeze ray creates an instant block of ice around the target. As we watched, I started to wonder: What might the science behind a freeze ray be? Let's take a look.
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Forecast Calls for Extreme Lows...
The first thing we have to consider is just how cold the air would have to be in order to freeze instantly. Earth's atmosphere is made up of about 78% nitrogen, about 21% oxygen, with the remaining 1% being other stuff. Since most of the atmosphere is nitrogen, let's concentrate on freezing that. Most people are familiar with liquid nitrogen, which is nitrogen that has been cooled so much it has turned from a gas to a liquid. If you cool nitrogen even further, you can turn it into a solid.
While water becomes a liquid at 100 degrees Celsius, nitrogen becomes a liquid at around -196 degrees Celsius; and while water freezes at 0 degrees Celsius, nitrogen freezes at around -200 degrees Celsius.
So we've got 2 possibilities for the freeze ray:
- The freeze ray makes the air cool down to -200 degrees Celsius, freezing the air around the person.
- The freeze ray makes the air cool down to 0 degrees Celsius, freezing the water vapor in the air around the person.
Since the extremely low temperatures of the first option would probably kill the target, and since nobody in the movie seemed to suffer any ill-effects from the freeze ray, let's take a look at option 2.
Water, Water Everywhere
Humidity is the measurement of how much water vapor there is in the air. Most of the time when you hear about humidity in a weather report, the meteorologist is referring to relative humidity. Relative humidity tells you how much water vapor is in the air compared to how much water vapor could be in the air. So when you hear on the news that the humidity is 90%, that doesn't mean that 90% of the air is water vapor. It means that water vapor has filled up 90% of the space that water vapor could take up in the air. Just how much water vapor the air can hold depends on the temperature. The hotter it is, the more water vapor it can hold.
If our freeze ray does in fact operate by freezing the water vapor around a person, then it would have the notable drawback of only working well on days with high relative humidity.
If You Can't Take The Heat...
So how exactly would you go about freezing the water vapor around someone? While many of us think of freezing as an excess of cold, it is better to think of it as a lack of heat. There is no such thing as cold energy. If we want to freeze something, we want to lower its temperature by removing heat energy.
In your freezer, for example, a cold refrigerant is passed through tubing inside the freezer. Heat energy leaves the food and enters the colder refrigerant. Since the food is losing heat energy, it cools down.
So one idea is that the freeze ray is shooting some kind of super-cold refrigerant around the person, which causes heat energy to pass from the water vapor into the refrigerant, resulting in the water vapor freezing. Unfortunately this super-cold refrigerant would likely also cause harm to the target.
So despite extensive scientific analysis, I was unable to find a way to turn the freeze ray depicted in the film into reality. This is perhaps why nobody has yet invented a portable freeze ray (as of the time of this writing).
See also: Do the Minions Speak a Real Language?
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