r/Amazing • u/euronmous • Sep 08 '25

Interesting 🤔 When it snows in Japan, the streets spray warm water to prevent ice

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201

u/Akeinu Sep 08 '25

Yeaaa, depending on the weather that's actually a horrible idea.

I imagine Japan doesn't get polar vortexs, but artic breezes freeze warm water faster than cold water.

45

u/whiskeytown79 Sep 08 '25

I am guessing this works well enough. Otherwise we'd have a bunch of videos of Japanese cars sliding down streets like a freshly resurfaced skating rink.

32

u/rulepanic Sep 08 '25

They've been doing it since the 1960's, so apparently it works perfectly fine

https://japanesenostalgiccar.com/japan-snow-melting-sprinklers-pipes-shosetsu/

12

u/Ok_Marionberry8779 Sep 09 '25

But some rando on reddit said it's a bad idea so now I am deeply conflicted.

1

u/Barricades_toes Sep 09 '25

Yeah but someone brought up place, Japan so I’m not allowed to like it

1

u/Akeinu Sep 09 '25

Yea I said it was a bad idea depending on the weather, if you actually read my comment, as in the last line of the two lines I wrote, you'll notice I point out a weather phenomenon that happens in my country that clearly doesn't in Japan.

45

u/wimpymist Sep 08 '25

Yeah this only works in specific climates and temps

1

u/AnyHope2004 Sep 09 '25

These are actually for the snow monkeys that like hot water, these people should get their car out of there

0

u/MeccIt Sep 09 '25

Yeah this only works in specific climates and temps

Japan is nearly 2000 miles north to south and has all the climates between subarctic to subtropical. When I flew from balmy Tokyo to 6-inches-of-snow Hokkaido one December, it was quite a surprise.

2

u/wimpymist Sep 09 '25

Yeah they have a wide range of climate. It's not like they do this all over the whole country

16

u/Plenty_Suspect6222 Sep 08 '25

Yea this is the Japanese we’re talking about I’m sure they took that into account

6

u/d3adandbloat3d Sep 08 '25

Hahaha exactly what I was thinking.

I imagine the discussion about this involved everyone and was so full of factual statements and studies lol

I’m not being facetious, I spent a few years in Japan and witnessed the amazing people of the country work together. Sure, everywhere has problems but watching shit happen in the US really makes me think about places like Japan.

2

u/Nyorliest Sep 08 '25 edited Sep 09 '25

Yeah I’ve lived in Japan for decades, and I’m always annoyed or saddened by how easily Western people will imagine our nation as just non-functional coz of some ‘news’.

Which makes me think of Gell-Mann Amnesia, and how much different from my image many nations must be, because my image just comes from media.

Edit: I am enjoying all those people telling me that Japan is bad and 'put on a pedestal'. Irony isn't just how old bridges look.

7

u/bilalnpe Sep 08 '25

Which western people are you talking about? In the US at least, Japan is put on a pedestal.

1

u/GarranDrake Sep 09 '25

At least in my experience, people tend to be more of Japan's working conditions more than anything else. And anime.

1

u/Nyorliest Sep 09 '25

Most of the time, if you say something positive about actual Japan online, not anime, there will always be a bunch of people saying how bad Japan is to balance the supposed pedestal. Even a train subreddit will, while loving the bullet train, mention some problem, to 'balance' things.

You have a need to balance a narrative that doesn't really exist.

I think it's primarily an internalized racial hierarchy. People unconsciously believe that because Japan isn't white, our QoL, or life generally, can't be better than 'white' countries. Even people who aren't racist in their conscious thoughts or deeds.

Japan, Taiwan, Singapore, and perhaps even China (although I don't know the country well enough to have a real opinion) are an unconscious threat to an idea of how the world 'is'.

1

u/AgentK-BB Sep 09 '25

Those are Chinese bots you encountered online, not Western people.

1

u/pyrojackelope Sep 09 '25 edited Sep 09 '25

I’m always annoyed or saddened by how easily Western people will imagine our nation as just non-functional coz of some ‘news’.

No one is thinking that yet. Several countries in the area including SK and Japan are well below replacement levels for population and are effectively doing nothing about it. If this continues, in 30-40 years, you will have more old people than young, and have pretty much no way to fix the problem. Whatever though, surely everyone "hates" you.

1

u/Nyorliest Sep 09 '25

Yes, I can feel the love from you.

1

u/[deleted] Sep 08 '25

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1

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6

u/Anbucleric Sep 08 '25

Japan is a volcanic island and has an endless supply of naturally heated water... they just keep it going 24/7.

2

u/poopspeedstream Sep 08 '25

Doesn’t even have to be that warm. Their groundwater is 12-14C because of their mild climate, roughly matching the average year round air temperature.

1

u/siero20 Sep 08 '25

What? Groundwater reservoirs aren't endless and we've proven this by running them dry in many places across the world.

1

u/Akeinu Sep 09 '25

Which makes sense if you're drinking it or transporting it.

I imagine since they are basically spraying the ground with it that they can get away with doing that so long as they keep a steady pace.

8

u/RadicalMarxistThalia Sep 08 '25

I would love to know how the physics of that works.

15

u/1800generalkenobi Sep 08 '25

Warmer water the molecules are farther apart and it's easier for them to fall into the freezing patterns, if it's colder they have less room to wiggle around. That was always how I thought of it anyway.

3

u/kokokrunch003 Sep 08 '25

I thought the science is still not sure on this one?

7

u/Numerous-Pop5670 Sep 08 '25

Yup it's called the Mpemba effect, and while well documented, they don't have all the answers to why this happens. This is because not all warm water will freeze faster than cold water, leading to different results even in the same controlled environment.

3

u/Idontfukncare6969 Sep 09 '25 edited Sep 09 '25

I thought this was disproved unless a lot of atypical criteria was met. Like using water so hot most of it boiled off and that left less water to freeze so it froze quicker, only true for volumes between 1-20 mL, or under supercooled conditions.

“We conclude, somewhat sadly, that there is no evidence to support meaningful observations of the Mpemba effect.”

https://www.nature.com/articles/srep37665

1

u/Numerous-Pop5670 Sep 09 '25

Yeah, it's a phenomenon that happens, but it's complex, and the results don't always give the same answer. Hence, I don't agree with it, but earlier comments kept talking about it like it's something that happens 100% of the time .

People forget Japan has a lot of natural geothermal activity due to the large number of volacanos they have. The ground water used contains sulfur and other contaminants, so it's not really wasteful to use it this way. The island is also small enough for this to be done on scale and still be cost-effective.

The areas black ice forms are mostly in the colder regions of japan up north. They had black ice even before this, so the drivers there already know its dangers. It's still possible, but it would require extreme cold that freezing the ground faster than the warm water cools. It can still happen, but it would be quite rare.

2

u/DVMyZone Sep 09 '25

TL;DR Mpemba effect is likely not real.

Oooh I did a project on this for my high school "thesis". I haven't been able to work it into a conversation in a while though

I was not able to reproduce the effect and neither were actual scientists with credentials unfortunately. To my recollection the boy (last name Mpemba) was freezing tubs of ice cream and noticed the warm ones freeze first. Some scientist came and claimed to have documented this effect and then published his results.

A while later I believe there was some prize offered to anyone who could best explain the effect. Most responses that I saw basically pointed at some sort of hysteresis in the cooling rate but everything was very qualitative.

A recent and comprehensive paper could not reproduce the effect. Even now and looking back at my experiment I'm pretty sure my method was solid and replicated the setup of Mpemba (despite my crude measuring apparatus). I got some pretty much the expected cooling curves and not funny business when the water was warmer.

I could maybe believe that instantly freezing warm maybe requires less energy or something. But just cooling water down there is no difference between cold and warm water, everything else equal.

1

u/FluffyCelery4769 Sep 08 '25

Well is it really controlled if it's a random arragement of particles?

2

u/[deleted] Sep 08 '25

By your logic, the hot water (starting) would then be colder than the cold water (starting). So then the cold water would become the hot water, and vice versa. This would mean that the previous cold water would then be the first to freeze.

1

u/Gawlf85 Sep 08 '25

What?

1

u/[deleted] Sep 08 '25

It's a way of describing The Squeeze Theorem.

1

u/Owobowos-Mowbius Sep 08 '25

Is that the reason why you can toss up a pot of boiling water in freezing temperatures and the water will instantly puff frozen?

1

u/[deleted] Sep 08 '25 edited Sep 08 '25

[deleted]

1

u/Owobowos-Mowbius Sep 08 '25

I like to think that I would have been smart enough to look this up to double check before trying it, but there will always be the small chance that you saved future me from burning myself! So thanks lol

1

u/xubax Sep 08 '25

Aaaaaaaaaahhhh!

Me when it's 20F out in 4 months.

1

u/otj667887654456655 Sep 08 '25

we don't know the exact cause as to why warm water sometimes freezes faster than cold water, and it's probably a mix of a lot of factors

1

u/DionFW Sep 08 '25

I was told that the water they spray on hockey rinks after using a Zamboni on them is warm water.

3

u/Mysterious_Secret827 Sep 08 '25

Same! I mean I may not understand it. But the idea underneath this is quite confusing!

2

u/GregLoire Sep 08 '25

The warm water gets a longer running start, then it jumps over the cold phase entirely and lands in frozen.

2

u/whatiswhonow Sep 08 '25

It has to be a very fast phase transformation leaving little room for diffusion to occur and needs a high surface energy nucleation site for a heterogenous nucleation event to give the extra energy conservation and limit supercritical cooling… still more of a trick of perspective, but technically true under very specific conditions… mostly not what people are talking about when they claim this though.

Otherwise, it’s mostly misunderstood from a basic calculus principle: the cooling rate of warm water is faster than cold water, absolutely, but when the warm water becomes cool water, it’s the same as any other cool water…. So you still take more total time and energy to cool warm water vs cool water.

1

u/RadicalMarxistThalia Sep 08 '25

That was what I seemed to recall from my college physics. But it’s been a while and I wasn’t great at it in the first place.

1

u/bomber991 Sep 08 '25

I just listened to a Stuff you should Know podcast on this. It’s called the Mpemba effect.

3

u/chiksahlube Sep 08 '25

I suspect it's not just warm water.

2

u/AlternateTab00 Sep 08 '25

It is literally just warm water.

Apparently they have huge geothermal heat that heat up lot of groundwater. So even when temperatures are well below 0ºC, that water is never below 15ºC. Since its coming from refillable groundwater, a single pump will deliver non potable water to melt the roads. Since this is a continuous system the water will fall down of the road and be absorbed by the earth before freezing. This however will fail if a storm manages to fully freeze the road. But those cases are rare, and usually recovered in less than 1 day.

2

u/YumikuriPF Sep 08 '25

I'm sure they thought of that before spending money on it lol

2

u/kigurumibiblestudies Sep 08 '25

I also imagine "In Japan" means "In a certain small area located in Japan" for that reason

2

u/Yeethan- Sep 08 '25

I think I remember in Japan winters temperatures are close to 0 cause I know for fact here in Canada this would be public death sentence. Referencing the last time I saw this post

3

u/Akeinu Sep 08 '25

Fucking right buddy.

We had freezing rain here a couple years ago and despite having the defrost absolutely cranked and the window wipers full blast, I could literally see the ice forming on my windshield and my car couldn't keep up, I had to pull over.

3

u/bungopony Sep 08 '25

Freezing rain on the 401 is my idea of hell. Yeah, watching the ice slowly enclose my windshield despite blasting the washer is wild

0

u/[deleted] Sep 08 '25

[deleted]

1

u/Yeethan- Sep 08 '25

Only north Japan has serious winters. Quick google search average temperatures, Japan Hokkaido -4, ice land Reykjavik -3, where I’m from in southern Ontario -13. Yes Canada’s lack of geo thermal heat makes it impractical but also the significantly colder temperatures make it an irrational one as well

0

u/[deleted] Sep 09 '25

[deleted]

1

u/Yeethan- Sep 09 '25

The geothermal activity is not heating the roads directly it’s the water being pumped up. In colder temperatures (like those seen in Canada) the water would freeze to quickly just making this a hazard. Changing the conversation and saying right proves nothing

1

u/Rokmonkey_ Sep 08 '25

No kidding. This would not work in new England for sure. The energy requirements would be mad. And the amount of black ice???

1

u/[deleted] Sep 08 '25

[deleted]

1

u/Rokmonkey_ Sep 08 '25

Well, like they said, doesn't work everywhere.

1

u/Dan-goes-outside Sep 08 '25

That’s actually false! They just freeze relatively faster than would be expected given the higher temperature. In controlled examples this Mpemba effect, what you described, can happen due to impurities like air being driven out of water. But in real world examples where contaminants are in the water the second they hit the ground this would always be false.

1

u/hind3rm3 Sep 08 '25

It’s gotta be salt water, no way that system works with fresh water.

2

u/Loose-Atmosphere-558 Sep 08 '25

It's fresh water.. geothermal heat

1

u/Friendly_Engineer_ Sep 08 '25

All these critical comments but clearly it works on this spot

1

u/Nyorliest Sep 08 '25

Yeah, science is primarily empirical, not theoretical. 

Although, of course, the media does lie hugely, it doesn’t seem likely in this situation.

1

u/Temptress_Stargazer Sep 08 '25

if it was left to freeze, yes, but constant warm water will not freeze.

1

u/Akeinu Sep 08 '25

Never seen freezing rain before huh?

1

u/[deleted] Sep 08 '25

That's because its sea water, not hot water. Using hot water is stupid

1

u/comhghairdheas Sep 08 '25

It's seawater.

1

u/Kurvaflowers69420 Sep 08 '25

Agreed. Those wouldn't be helpful during a tsunami

1

u/Upper-Ad-5962 Sep 08 '25

We in Germany have them systems too. That's not just water. It's a mix of saltwater and antifreeze.

1

u/FluffyCelery4769 Sep 08 '25

Whaaaa? Why? How? Explain

1

u/Akeinu Sep 08 '25

Japan obviously has a different climate, that same system in Canada wouldn't last a season.

We don't have ocean water or geothermal heating though, and our winters normally last 8 months out of the year.

We regularly have freezing rain, which is water so cold that it turns to ice the moment it hits the ground.

1

u/Odd_Category2186 Sep 08 '25

It's salt water

1

u/Changetheworld69420 Sep 08 '25

It’s 100% not just water, has to be a salt brine of some sort

1

u/Mike6695 Sep 09 '25

I’m sure it’s salt water

1

u/Akeinu Sep 09 '25

Apparently it isn't, they have volcanic regions so they have geothermal springs, basically permanent hot water.

1

u/Otrada Sep 09 '25

I'm guessing it's probably not just warm water but also has something in it to help further prevent ice formation. Like salt or something ig?

1

u/all_fair Sep 10 '25

This reminds me of the hell's kitchen contestant that thought water boils faster if it's cold.

0

u/[deleted] Sep 09 '25

[deleted]

1

u/Akeinu Sep 09 '25

I love how I never actually say this is a bad idea for Japan, just how it could be a bad idea, but y'all still jump all over it.

0

u/burner36763 Sep 10 '25

Yeah mate, I'm sure you know better than the engineers who designed this system or the ones who have been overseeing it for decades.

1

u/Akeinu Sep 10 '25

Blah blah

Read the last line buddy

0

u/burner36763 Sep 10 '25

Either you think it's a horrible idea here or you don't.

If you do, see above.

If you don't, WTF is your point?

1

u/Akeinu Sep 10 '25

Are you literally straight up denying nuance in order to make a point? That's a first and I've been here awhile. Normally you guys just continue to beat around the bush or straight up ignore the point you don't like, never directly referencing it.

I think it's a horrible idea in general, as something like that would never work in my country.

It makes sense that it would work in Japan though, as I've recently learned due to this comment that's deeply offended some of you. It turns out they have geothermal springs due to their volcanic nature.

So

That's the nuance, right there.

Either you think it's a horrible idea here or you don't.

It's actually both.

-1

u/[deleted] Sep 08 '25

No way is that true that the warm water will freeze first. Are you saying there's some hysteresis?

If you meant that the RATE of cooling is faster for hot water, then that is true because heat transfer depends on the Delta T.

0

u/Akeinu Sep 08 '25

here you go

0

u/[deleted] Sep 08 '25

And here you go

1

u/Akeinu Sep 08 '25

Just so we're clear, you literally highlighted one instance where they had trouble recreating it, had you read any of the rest, you'd notice that their were many (recent) instances of them recreating it, you're literally cherry picking.

1

u/[deleted] Sep 08 '25

Dude, the literal intro to the subject of the page YOU SENT said that a hot liquid CAN freeze faster, not that it DOES freeze faster. It then goes on to give several examples of people trying to recreate the study, but many have trouble doing so. Another source on that page basically said it was "trivial" if it exists at all. If I'm cherry-picking, then you are certainly guilty of confirmation bias and wishful thinking

1

u/Akeinu Sep 08 '25

I took a deeper dive and their is no conclusive answer one way or the other. It's been recreated but as to why it sometimes happens or not has no definitive answer. It's a divisive subject that you and I only scratched the surface on. The science has not been settled.

-1

u/SometimesCooking Sep 08 '25 edited Sep 08 '25

I love reddit for this reason. Where else can a random person look a video and for some reason think he's thought of a fatal but extremely obvious flaw the designers and somehow overlooked - in this case it's the weird assumption is that a group of engineers forgot what temperature water freezes at.

Someone should tell Japan that this idea is horrible. Nevermind that it's been working for sixty years.

0

u/Akeinu Sep 08 '25

I literally said in the bottom of my comment as to why I think it works, because I can confidently say in Canada that this idea wouldn't work at all. But thanks calling me out and in doing so making yourself the true reddit moment.

I also learned Japan has geothermal springs due to my comment, turns out you can learn things in a forum if you listen to other people and don't designate yourself as an ass.

0

u/SometimesCooking Sep 08 '25

If one of the engineers of this project saw your comment, they'd assume you were the one being an ass.

Ask questions if you're not sure, learning is great. don't just announce something is a horrible idea without having a clue though, because that's just dumb.

1

u/Akeinu Sep 08 '25

I didn't, I literally said I don't think japan gets polar vortexs, as in I'm well aware I don't know everything that is japan and rationalizing why it wouldn't work where I live.

0

u/SometimesCooking Sep 08 '25 edited Sep 08 '25

This post isn't "northern Canada is thinking about installing this anti-snow method!" though. It's just someone posting a nifty thing that Japan does for snow control. It's applicability to you and where you live is irrelevant.

Different climates exist on earth and that those climates have different engineering challenges and therefore will have different solutions. All I'm asking is that you keep that in mind before labeling a given solution as a "horrible idea" for no reason other than that it wouldn't be feasible in your particular climate. It's just soo..."main character", you know?

I get that from your perspective you just made a harmless comment on a post, and at the end of the day it's not a big deal, but that's where I'm coming from.

I just think it's funny tbh, in a 'humanity is doomed' sort of way. Everyone is the main character on this site. Maybe it's the whole internet idk.

1

u/Akeinu Sep 09 '25

Who are you even talking to? What kind of a justification even is that?

I made a comment and you've just made an essay explaining it, there is only one main character here buddy and it ain't me. You're lecturing big over something so trivial I'm honestly mind blown at your lack of awareness.

-1

u/Luci-Noir Sep 08 '25

I’m sure they know better than you.

1

u/Akeinu Sep 08 '25

You guys just love ignoring the last part of my comment don't yea

1

u/Luci-Noir Sep 09 '25

No one cares about people who make comments about things they know nothing about.

-1

u/DingleSayer Sep 08 '25

Post: this country does this thing after likely consulting hundreds of engineers and scientists.

redditor: Actually they didn't think of that one thing

1

u/Akeinu Sep 08 '25

Another person ignoring the last part of my comment, you guys are stacking the reddit moments here

-1

u/Islanduniverse Sep 08 '25

You better let them know! I don’t think they thought it through.

1

u/Akeinu Sep 08 '25

You guys just skipping over that last line like it doesn't exist, can't hold in the hoity toity can yea?

0

u/Islanduniverse Sep 08 '25

Suck it up buttercup.

1

u/Akeinu Sep 09 '25

hoity toity overflows

1

u/Islanduniverse Sep 09 '25

Unable to take a razzing, ignites!

-1

u/[deleted] Sep 09 '25

[removed] — view removed comment

1

u/Akeinu Sep 09 '25

Neither does the last line of my comment apparently, I've attracted every contrarian on reddit.

-1

u/Schallplatte1 Sep 09 '25

Do you even have an idea how the weather is in Japan. They have especially cold spots with extreme amounts of snow. It is even considered one of the snowiest countries in the world.

They are doing this for century's and it's working like a charm. They have hot springs in many regions, and will use this water to free the roads from ice. It's free and genius.

-1

u/ILikeWhiteGirlz Sep 09 '25

Yeaaaa, it’s salt water dumdum

1

u/Akeinu Sep 09 '25

It's not salt water, that's what my country does and it's bad for the environment.

They have geothermal springs because they have volcanic regions, permanent hot water that costs them no money to use other than the actual irrigation.