When I was about ten (?) years old, I had the brilliant idea that cars should carry laser beams in order to melt snow they’re about to drive on. My father, an engineer, said just that it couldn’t work, but didn’t explain that day why not. To dash the dreams of future youth with the same idea, let me spell out now why not.
Let’s pick some reasonable figures. Let’s work in SI, because, well, it’s a Sunday.
- two 12.5 cm wide front tires
- 1 cm deep snow, density equivalent to 1mm rain
- -1 degC snow temperature
- 4 m/s crawling speed
We need to compute how much dihydrogen oxide we want to liquify. Its total volume is: 4 m/s * (2 * 0.125 m) * 0.001 m = 0.001 m^3 = 1 L/s. And since water’s density is pretty close to 1 kg/L, let’s just say it’s 1 kg/s.
The energy required to heat up the -1 degC snow to its melting point of 0 is around 4.2 J/g. The additional energy needed to actually melt it is called the latent heat of fusion, which for water is about 333 J/g. The total energy is therefore around 337 J/g.
Now let’s calculate the amount of power needed to melt even this minimal snow cover. 1000 g/s * 337 J/g = 337000 J/s = 337 kW. A common power level for handheld laser pointers is on the order of 3 milliwatts, so you’d need 100000 of them. Before you try to find room for them in your car, consider that 337 kW is about 450 horsepower. Your car’s engine had better put out far more power than that, to power an unusually manly alternator, and of course to keep the car moving through the snow-cum-water.
So yeah, it is not going to work.
Echoing this EU Referendum article, I will send somewhat less money across the pond – and none to the New Scientist magazine.
It’s not just the mediocre science reporting, examples of which abound, reaching absurdity as the title feature of the issue shown above.
It’s that this putatively science-oriented magazine has infused so much of its content with fashionable politics of the day that I can’t enjoy reading even the good stuff any more. Every other blurb, on whatever subject, will take time to put some digs into Stupid President Bush or Evil America or whatever. I’m not even an American but it embarrasses and angers me.
Unless the claim of the magazine is that science is inherently political, and they come clean with this, they are hereby punished for treating the matter so lightly. “The week’s best ideas”? Stop that subscription.
Interesting coincidence: my family’s first names’ initials, in decreasing order of age are: F, J, E, S.
One of the first airplanes I learned to fly in was called C-FJES.
It’s hard to outdo this article about the fashionable trend for “activism” in order to raise “awareness”. If you support “earth hour”‘s effort to cut electricity use 5-10% in certain locales next saturday night, let me make you aware of a simple mathematical fact. Even 10% savings over the course of the entire hour translates to a rather unwhopping 0.0011% savings over the rest of the year. Good job though, keep it up.
UPDATE during earth hour:
