this post was submitted on 05 Aug 2023
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Showerthoughts

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A "Showerthought" is a simple term used to describe the thoughts that pop into your head while you're doing everyday things like taking a shower, driving, or just daydreaming. The best ones are thoughts that many people can relate to and they find something funny or interesting in regular stuff.

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Explanation: Random walk in 2D has a unity probability of making it back to the starting point as the number of steps approach infinity but random walk in 3D only has ~0.34.

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[–] [email protected] 32 points 11 months ago (1 children)

TL;DR: birds can fly up and down so they are more likely to get lost

[–] Widowmaker_Best_Girl 10 points 11 months ago (1 children)

Thank you, OP put his thought out so confusingly

[–] [email protected] 1 points 11 months ago
[–] zkfcfbzr 21 points 11 months ago (2 children)

Expanding on what OP is talking about:

In this context, a random walk happens on a 2D coordinate plane. Your drunk person starts at the origin, (0, 0), and for a "random walk" they move either left, right, up, or down by exactly 1 unit each step. It's a mathematical fact that this process, taken to its limit where infinitely many random steps are taken, will always have the drunk return to the origin - in fact, for any given integer coordinate on the plane there's a 100% chance the drunk will eventually visit that coordinate following a random walk.

This doesn't work in 3D though, where there's an x, y, and z axis. A random walk there won't always return to the origin - it only will about 34% of the time. If the drunk gets too far away the probability of ever finding their way back at random quickly drops to 0.

[–] o_oli 12 points 11 months ago (1 children)

So if we ignore that birds can't fly infinitely high, and also that they don't live in the air they live on a surface, in essentially a 2D area the same as humans, maybe this is interesting? But not really lol.

[–] zkfcfbzr 5 points 11 months ago

If you limit the extent of the third dimension to any finite value then my intuition says the probability is probably back to 100% but I don't know for certain.

[–] [email protected] 4 points 11 months ago (1 children)

That doesn't make sense to me. Sure, the probability in 3D is gonna get really low. Never 0 though since there is a chance the previously taken steps will be done in reverse. And since we talk about infinity here .. the drunk bird should also find home.

[–] zkfcfbzr 8 points 11 months ago* (last edited 11 months ago) (1 children)

I was maybe a bit sloppy when I said it "quickly drops to 0" instead of it "quickly tends to 0". It'll of course always be positive - in fact if N is the sum of the absolute value of the three coordinates of its current position, the probability of returning to the origin is strictly greater than 1/6ᴺ.

But it does tend to 0 in such a way that the probability of its random walk ever returning to the starting position is not 100%. It has a 34% chance of ever getting back at the very start of its journey - but if it gets too far off track that probability is going to tend to 0 fast enough that it's not likely to ever make it back, even with infinitely many steps. Here's a youtube video (that I did not watch myself) that seems to go over the topic.

[–] [email protected] 2 points 11 months ago

Here is an alternative Piped link(s): https://piped.video/watch?v=iH2kATv49rc

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[–] [email protected] 13 points 11 months ago

Gravity gives up and down a lack of symmetry that left and right maintain. A drunk bird is more likely to fall than fly to the moon.

Also, in materials science, randomly walking atoms (Brownian motion) in a crystal structure displace roughly at, if I recall, the square root of their velocity, on average.

[–] jesterraiin 10 points 11 months ago

Everyone is always equally drunk, and the road is always the same

Guys, an unpopular opinion, but perhaps you shouldn't take too long showers, eh?

[–] [email protected] 9 points 11 months ago (1 children)

I don't think a drunk bird can fly

[–] foggy 5 points 11 months ago (1 children)
[–] Sylver 5 points 11 months ago

More like ALTITUDE amiright lmao xD

[–] [email protected] 6 points 11 months ago (1 children)
[–] t_jpeg 5 points 11 months ago* (last edited 11 months ago) (1 children)

We're fine at finding our way home because we only have to navivate an effectively 2d space (as we are on the ground). Imagine if we had to fly and so had to navigate 3 directions (height as well) whilst being intoxicated. We'd be fucked... is what I think OP is trying to say.

[–] [email protected] 5 points 11 months ago

But a drunk bird will start from the ground, and probably end on the ground, which collapses its random walk back to a 2d plane

[–] [email protected] 3 points 11 months ago

The thing is that drunken walking/flying is still not completely random.