You’re strolling along on a fresh spring day,
on your way to an important appointment, perhaps an interview or a date, you’ve
blow dried your hair and you’re wearing that nice cashmere jumper you got for Christmas.
When suddenly the clouds darken and you feel the first drop of, what is about to be,
cascading sheets of rain. You’re a good hundred meters from your nearest cover.
But how should you get there, will frantically dashing into the rain actually get you wetter
than if you calmly continue to stroll through it?
I’m Stu, this is Debunked, and we’re here to sort the truths from the myths,
and the facts from the misconceptions.
It would be fair to say that a natural response to finding yourself at the mercy of the elements
is to run, the thinking being that less time in the rain means less rain on you.
Sounds reasonable enough, right? Well, perhaps not.
For decades, people have speculated that running through the rain may, somewhat
counterintuitively, result in you actually getting wetter than if you had just walked.
This is based on the idea that, although you’ll spend less time in the rain if you
reach your destination faster, moving forward quickly through the rain that
is falling in front of you will mean you’ll hit more raindrops than if you’d just walked,
resulting in a wetter you when you arrive at where you want to be.
Let’s look at this a little closer. Assuming that the rain in which you find yourself is
falling consistently and vertically downwards (and that’s already quite the assumption),
over the same period of time you’ll be hit by the same number of raindrops regardless of your speed.
This is because it doesn’t matter how fast you’re going; moving out of the way of a falling drop
of rain is always going to move you into the path of another one at exactly the same rate.
As a result, it actually works out that in any given period of time in which you’re in the rain,
you’ll actually get less wet by standing still.
Moving through the rain means that in addition to the rain falling directly on top of you,
more raindrops will hit your body head on as you move. Like rain hitting you from above,
this amount is also constant; it doesn’t matter specifically how fast you’re going
because moving out of the way of one rain drop moves you into the way of another.
Of course, this doesn’t get to the core of the issue. Obviously, standing still literally
doesn’t get you anywhere, and you probably want to be indoors as soon as possible when
it starts chucking it down rather than just standing there getting drenched.
But before we get moving,
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Right, the question at hand is whether walking or running to your destination will leave you
drier when you arrive. If you’re actively trying to get out of the rain as the question assumes,
although the speed at which you’re moving doesn’t affect how many raindrops will hit you,
the amount of time you spend exposed to the rain
very much does, and that is dependent on how fast you’re moving to get there.
So yes, running through the rain does mean that you’ll end up drier.
But how much drier? Is the difference significant enough to justify the effort?
Lucky for us, a whole bunch of theoretical and practical studies have been conducted
on this very topic so we can stay nice and dry!
Firstly we have Harvard mathematician, David E. Bell who published a paper back in 1976,
and found that even if you’re running at a speed comparable to that of a professional
sprinter (which, let’s face it, you probably aren’t) you’ll only get about 10% less wet.
Then, in 1987, physicist Alessandro De Angelis made his own assessment of the
problem and seemed to be broadly in agreement with Bell, concluding pretty brusquely that
“...by running faster you get less wet, but the benefit that you get
beyond the speed of a brisk walk does not justify the supplementary effort.”
This obviously begs the question,
is it worth expending the energy to run for such a small benefit?
So, in 1996, a pair of meteorologists decided
to throw their hypothetical hats into the proverbial ring, suspecting that previous,
purely theoretical studies had over-estimated the average speed at which people walk.
They also wanted control over certain variables
including the effects of wind and the fact that runners tend to lean forward.
Using themselves as test subjects, one of the intrepid researchers walked through a
100 metre track while being rained on, while the other academic ran.
When their relative wetness was assessed, they found that the runner was 40%
drier than the walker, a difference that might actually justify the effort it takes to speed up.
But the boffins haven’t stopped there. In their voracious quest for knowledge,
scientists have also factored in things like wind direction and intensity.
For instance, our old pal Bell pointed out in his study…
that when rain is falling either vertically or the wind is blowing it towards you at an angle,
the faster you run, the less wet you will get over the same distance,
so theoretically you should try to run as fast as possible.
However, if the wind is blowing the rain at you from behind, you should still run, but this time
there is actually an optimal speed at which you need to move that is equal to that of the wind.
Running either slower or faster than this speed
reduces how relatively dry you’ll be upon arrival compared to walking.
These claims were expanded upon by another study,
entitled ‘Whether or not to run in the rain’, written by another Italian called
Franco Bocci and published in the European Journal of Physics in 2012.
He found that one’s exposure to rain also depends somewhat on body shape;
for people who are particularly thin, there might be an optimal speed at which to move,
whereas for most other people the best strategy is generally just to leg it as fast as you can.
So, as you can see, the question of whether or not to run or walk in the rain
throws up a range of unexpected concerns and considerations,
and indeed, much of the scientific discussion of the issue deals with very specific theoretical
aspects of the problem that aren’t at all practical to consider in the real world.
I don’t know about you, but having to factor wind speed and direction,
as well as how fat you are, into your decision on
whether to walk or run through the rain feels just a little like over-doing it.
So, to answer the original question, it appears pretty clear that running in the rain will
leave you drier upon arrival when compared to walking, perhaps up to as much as 40% drier.
On a human level, however, whether or not it’s worth rushing through the rain is up for debate.
Maybe you just hate being rained on and trying to avoid getting wet is your primary concern.
But many people might honestly prefer to get wetter if running
means a higher chance of splashing yourself in puddles, tripping over,
or arriving at your destination not only wet, but hot and sweaty too.
It’s also a simple fact that any amount of physical exertion is horrible,
I don’t want to do it, and you can’t make me.
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