[travisjungroth]

This reminds me of headwinds in airplanes. You might think that on average, wind cancels out. Sometimes you have a tailwind, sometimes you have a headwind and over time it will all average out. This is not the case.

On average, wind reduces your groundspeed. The short of it is you spend more time in a headwind, so you spend more time experiencing the bad than good.

There's also the fact that even a direct crosswind slows down you ground speed (you lose some speed for correcting your course) but I don't think this compares to block chains or hitchhikers.

[foota]

That's really neat, thanks!

An interesting related fact is that with equal distance traveled through headwinds and tailwinds a slower plane will be relatively more affected. From ~12% longer time with a wind speed 1/3rd plane speed down to ~1% with a wind speed 1/10th plane speed.

[travisjungroth]

That's one of the reasons it's easier to navigate in a fast airplane than a slow one (another being you see more ground in the same amount of time).

[foota]

Wouldn't cross wind cancel out in average though? (even though head and tail winds don't)

[travisjungroth]

No, because you spend some of your forward speed flying into the wind to keep the desired ground track.

Imagine an airplane that flies 100mph. You want to fly north, but you have a 90pmh crosswind from the east. You have to point almost directly into the wind just to keep from getting blown off course. You can turn a little to the north, and you'll go very slowly. If you instead have the wind come from the east, you still have the same problem.

Maybe easier analogy: to get directly across a river, would you rather swim across one going fast or slow?

[foota]

Sure, with a consistent cross wind of course you'll have to spend energy fighting it, but if you don't fight it and halfway it changes, you'll end up at your destination in the same time as you would have otherwise, no?

[aidenn0]

Sure; if you can predict the future, and the future happens to be that the crosswindws will oppose each other, then you can just set your heading and get there.

However, if the wind doesn't shift you are now taking even longer to get there because you'll have to turn to go straight upwind once your destination is directly upwind from you.

[travisjungroth]

This crazy world you describe applies in a different axis! Vertical movement of air happens on a much smaller scale, so it tends to cancel out as you fly through it. If you climb in the updrafts and descend in the downdrafts, you only make it worse. Better to ride it out.

[slededit]

The US air traffic control system is setup as a series of highways in the sky. You generally can't just fly in whatever direction you want (with the exception of general aviation).

[fny]

This isn't what the poisson distribution tells you.

You will, on average, wait 10 minutes. If you hitch hiked that road 1000 times, you'll have waited 10 minutes on average.

But that doesn't mean you won't wait longer that 10 minutes on a given wait. In theory, you're waiting time will follow an exponential distribution, so you could wait 1, 10, 50, or even 1000 minutes (although quite unlikely)!

But again... On average, you'll be waiting for 10 minutes from car to car.

[photojosh]

Same with riding a bike in hilly terrain... you spend an hour climbing a hill, only to descend back down the other side in 10 minutes.

[thaumasiotes]

> You might think that on average, wind cancels out. Sometimes you have a tailwind, sometimes you have a headwind and over time it will all average out. This is not the case.

Only if you didn't have to do the standard physics problem comparing swimming X meters upstream and back downstream to swimming X meters across and then back across.