Do you get less wet if you run in the rain? | Hacker News Reader

Do you get less wet if you run in the rain?

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27 pointsvinutheraj34 comments

Conclusion: To get to a specific place you get more wet by walking. To travel for a specific period of time you get more wet by running.

In other words, running in the rain gets you more wet, given that all running is doing is reducing your exposure time.

(Yes, sometimes that exposure time can result in you coming out ahead, but it's not really answering the question)

EDIT: What the hell's with the downmods? What is this, reddit?

If I've parsed that correctly, you're wrong. The following are true:

For a given amount of time, running in the rain makes you more wet.

For a given distance, running in the rain makes you less wet.

Running reduces your exposure time by more than the increase in rain_per_time.

Perhaps I've simply mis-understood you.

You've basically repeated what I said.

My point is that reducing your exposure time is basically altering a different variable in the equation.

If you control that variable by not running to a place where the exposure to rain stops, it becomes clear that by running you will get more wet than if you were simply walking.

And yes I understand that practically, running to a dry spot is the whole point.

Nope, I still don't understand you. One more try, then I'll give up.

You originally said:

    In other words, running in the rain gets
    you more wet, given that all running is
    doing is reducing your exposure time.

The running is reducing your exposure time, and that reduce is enough to get you less wet. Hence your claim that it gets you more wet is nonsense.

What have I misunderstood?

The running is reducing your exposure time, and that reduce is enough to get you less wet.

Um, the "exposure time" variable is exactly that. The act of running causes you to increase your rain exposure, so unless I'm missing something, at some point the "exposure time" will become long enough that the act of running is rendered ineffective, and then actually becomes worse. (For example, if you ran around in a circle for a set time, instead of from point to point).

Like I said, I do get that by that point it may not functionally matter, and that if you ran from your car to the store you will not be as wet as if you walked, but it is important to understand the subtleties in order to properly understand why.

Nope, I give up. It seems to me that what you're saying is either trivially true and therefore completely pointless, or simply wrong. I can't believe you're as clueless as my parsing/reading seems to make you, so I guess we're just talking past each other.

Maybe others will understand you and gain something from it, but I doubt there's much to be gained by you continuing to explain to me, and me trying to understand.

Thanks for trying.

what he means is that running gets you more wet per time unit compared to walking

But isn't that completely obvious? Surely he must mean more than that, otherwise his "contribution" is completely pointless.

I've been running on and off for the past 16 years. In my experience, I do not get as wet while running in the rain as I would just standing in it.

I think there must be a missing variable, such as excess water whisking off more quickly, greater evaporation due to heat transfer or maybe something else.

Perhaps a more forward posture causes the front of your body to be "shaded" by the rest of your body, leaving the front (that you notice more) drier?

I've spent a lot of time learning math (have a CS degree, which required lots of math). But sadly, I'm not comfortable enough with differential equations to come up with a solution like the first part. It makes sense once someone else has done it, but I wouldn't have gotten that far.

Perhaps I just need more practice. Practice makes perfect with math like everything else?

You don't really need much math to understand this. Imagine that a person is a perfect cube. The amount of rain hitting the top of this cube is constant-- does not depend on the speed of the cube. The amount of rain hitting the front of the cube is proportional to how fast the cube is moving. From this insight, everything else is algebra.

I was referring to coming with the differential equation first presented.

Understanding it is one thing, but coming up with it independently is different.

I wonder if the multivariate nature of this problem is throwing you off more than the differential equation aspect of it. If you know multivariable calculus you can think about this problem at a higher level of abstraction (vector fields and flux). The integral you see is the output of the thinking at that higher level of abstraction.

I bet with proper background and practice you could set things like this up rather easily. You just need to learn to think about the problems at the proper abstraction level and then develop some intuition by actually doing lots of problems.

Your CS degree required "math", but not much calculus or analysis. If your degree was in, say, mechanical engineering instead (or anything in the family of applied physics), you'd be much more comfortable with the differential equations. But then, you'd probably have a harder time with discrete stuff like statistics, and the number theory behind RSA would completely baffle you.

Yes, basically. You just need more practice.

I think there is a simpler way to picture this. Imagine a volume of water suspended in the air - the height and width is the person's cross section, and the length is distance to be travelled. All of that water is going to get onto you regardless of how fast you travel. So speed is not relevant there. But for the water hitting the top of the cube, it gets wet only with respect to time, and not to speed.

Conclusion: if the rain is falling straight down, it always makes sense to run.

What contributes to how I feel when I arrive isn't the factor of my wetness, but how long I spent being rained on.

http://en.wikipedia.org/wiki/Peak-end_rule begs to differ.

It can beg all it wants, I'm still gonna run :)

I stop thinking about being in the rain as soon as I'm sheltered, so I'd rather minimize being in an unpleasant situation.

Interesting rule, however I disagree with the extent of the assumptions taken from the experiment in the wiki, because:

Blasting the second group with a less painful noise AFTER a more painful noise will result in a sense of relief when the less painful noise occurs. I believe this relief has a big impact on what people remember.

Also, I believe the second group would insist on increased unpleasantness if the less painful noise preceded the more painful noise.

Nonetheless, I believe there is some truth to the rule.

I, like you, try to optimize a different thing than the article: I want the time at which my wetness level is normal to be as soon as possible. As such, it makes sense for me to run to shelter if only because I will get to start drying off sooner.

Oddly enough, all three optimizations lead to the same conclusion: that the best thing to do in any case is to run until you escape the rain.

Nice. A fun/rational way to look at what is at heart an emotional decision. :)

Another angle on this is that running spreads the wetness over more surface area (less on top, more on front). If you're wearing a hat, you might choose to walk, etc.

I won't argue the conclusion, just introduce an anecdotal observation.

When it is spitting or raining very lightly, sit in a stopped car and watch the rain on the window.

Now, speed that car up to about 80km and see what happens. Disregarding spray from other vehicles, odds are that there will be more rain on the windshield in the same amount of time.

Like I said just an observation.

Yes, but for a given distance you get less rain on the windscreen when you drive fast, rather than driving slowly.

Of course, because you've substantially reduced your exposure time. But the act of increasing your speed itself actually causes you to come in contact with more raindrops, not less.

Per unit time, yes. Per unit distance, no.

I'm just not getting you. I'm giving up.

I once asked this question on a calculus exam.

This question is the reason I went into engineering.

I learned calculus by correspondence in high school. Solving this problem transformed calculus in my mind from just some abstract problems to solve into something useful. It was a big turning point for me, and focused my interests in areas of applied math.

didn't the mythbusters test this in one of their first couple of seasons? iirc, they did, and came to the same conclusion

They originally said if you ran you got more wet: http://en.wikipedia.org/wiki/MythBusters_%28season_1%29#Who_...

But then they changed their mind after that show: http://en.wikipedia.org/wiki/MythBusters_episodes:_Season_3#...

I used to ride my bike to class in the rain, and I would always get more wet than if I walked.

It's possible for this to be true, since on a bicycle you may tend to expose both your back and front to the rain more so than when walking.

Also, chances are that you kick up water as well

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