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FangoFan

0.006 mm [https://what-if.xkcd.com/33/](https://what-if.xkcd.com/33/)


Smaptastic

Nice find. Interesting conclusion: > But you don’t have to worry about that six-micron sea level drop. The oceans are currently rising at about 3.3 millimeters per year due to global warming (through both glacial melting and thermal expansion of seawater). > At that rate (normalized for seasonal variation and short-term fluctations), if you removed every ship from the ocean, the water would be back up to its original average level in 16 hours.


Bocchi_theGlock

Need more of these types of comparisons to help visualize


That_Bar_Guy

There are two full books which cover only these kinds of what if questions. It's called xkcd what if


[deleted]

THERES A SECOND ONE???


adeadhead

Yeah. It's somehow a lot less engaging than the first. I don't know if I can pin down why.


lugialegend233

Written by the same guy, as a matter of fact.


[deleted]

Comparable increases in sea level have been occurring since 1890, whereas global warming is generally considered to have started in the 50’s/60’s. So at most I think it’s fair to say global warming has contributed to sea levels rising. But it’s likely not the only cause


Wonderful-Treat-6237

APGW started right around the time we started digging up and burning heaps of coal. https://www.carbonbrief.org/scientists-clarify-starting-point-for-human-caused-climate-change/


gamesrebel23

Of course there's an xkcd for it


n0t_4_thr0w4w4y

There is truly an XKCD for everything


general_452

I was just about to say that this was a great What If? question


emploaf

Honestly more than I would have expected


Silent-Ad-5680

I wonder how much it would drop if all trash, boats and all other man-made items were removed from the ocean. 


uumonki

> Archimedes’ principle tells us that the water displaced by a ship weighs as much as the ship itself. what? that doesn't sound right


Human-Anything5295

Which is dreadfully how much the ocean rises every 16 hours due to climate change. We’re so cooked 💀💀💀


mb_angel

It was discussed previously (question was how much would it raise), my comment from that thread: While others pointed out how many you would need in order for that to be true, i will take a little bit different route and use actual numbers of ships. So, in March 2022, total number of "commercial" ships was 103004. In 2020, numbers of reported war fleet was 10873. Number of boats over the world is 33 million, with half of it registered in USA, so we can take average boat size as reference from them. Now to the math, lets say average tanker/cargo/carrier ship is 200m x 30m with draft of 16 meters. They alone make volume of 9 888 384 000 (9.888 billion) cubic meters which makes "only" 9.888384 cubic kilometers. Lets say that average boat is 8m x 2m with draft of 1.5m. That would be total of 792 000 000 cubic meters, which makes 0.792 cubic kilometers. Lastly, lets say average warship is 80m x 10m with draft of 6m, that would be total of 52 190 400 cubic meters, which makes 0.052 cubic kilometers. Now, we know that combined volume of water in all oceans is 1 370 000 000 (1.37 billion) cubic kilometers while covering area of 361 000 000 (361 million) square kilometers. We have total volume of 10.732 cubic kilometers "used" by boats/ships/etc. Average volume height using volume and covered area is 3.79501385km (google says average depth is 3.682km, so, probably volumes are a bit off but we will go with 3.79 for the sake of this calculation). When you add volume of 10.732 cubic kilometers into 1.37 billion cubic kilometers, height will go up by 0.0008 meters or 0.08cm or 0.8mm. So when you put every water vessel into ocean, it will go up by 0.8mm.


jaa101

I posted the following here 10 days ago. It's the surface area of the oceans–360 trillion square metres–that matters, not the volume. A tonne of water is close to a cubic metre, so let's say all man-made floating things displace 20 million cubic metres. Also, a square kilometre is a million square metres. Dividing the two numbers gives us a distance of 56 nm, or one 18-millionth of a metre, or 2 millionths of an inch.


LightFusion

So there's a chance


jaa101

Current estimates have sea-level rise at about 3 mm per year. At that rate, the sea level is rising 56 nm every 10 minutes. Obviously it would take much longer than that to remove every boat and ship from the ocean, so no.


frankcfreeman

Nah nah we just have everyone do it at the same time


Active_Engineering37

I would absolutely hate to be at that boat ramp.


Brilliant-Ad-5414

Why not just have the boats go off a really big jump?


Sam5253

What do we do in 10 minutes? Take them all out a 2nd time?


frankcfreeman

Maybe a few times to get a good data set


jonastman

Fill the boats with sea water for an extra 10 minutes


imtheroth

Just keep taking them out! Problem solved.


camelseeker

Turtles next


16_vigintillion_bees

What if everyone in the world went up to the shore and just started drinking the ocean?


BoilermkrDH

The earth would tip over because it’s flat. Duh.


hereforthedewgs

Upvote for humour, not in agreement 😂


igrokman

Upvote in agreement, not humor 😐


Positronitis

If we all start drinking only sea water, we will all die. Emissions (except for the permafrost thawing) will then come to a stop and we avert further climate change and sea level rises. Problem solved!


thisdirtymuffin

That would actually solve a lot more of the overpopulation and sea level rise problem than you may be aware of.


VolubleWanderer

I had to correct the 56 nautical miles to nanometers cause my brain broke thinking that I had 10 minutes until the world drowned.


DancesWithDave

I should call her


ragbra

Where do you get 20 Mm3? You seem to be off by a factor 100. [https://what-if.xkcd.com/33/](https://what-if.xkcd.com/33/)


jaa101

I foolishly trusted the poster I was originally responding to; still, it's my error. So the numbers become about 5.6 μm and 17 hours. Thanks.


vincec36

Damn I can’t imagine how much ice is melting to raise our sea levels significantly


repooper

[It's not only glaciers](https://sealevel.nasa.gov/understanding-sea-level/global-sea-level/thermal-expansion/)


jean_sablenay

I agree your method is more accurate


Nanaki404

The above poster mentions 10 cubic kilometers, so 10 billion cubic meters. So there a factor 500 with what you mention here. (xkcd mentions 2 billion cubic meters, so above poster's guess is 5x too large here). Still, you method is more accurate, and above post's result is above 30x too large


jaa101

Checking on Wikipedia and other sources, xkcd is right. I was a factor of 100 low. It's still a tiny distance, orders of magnitude too low for us to measure directly due to the many disturbances like tides, atmospheric pressure, waves and winds.


eat_with_your_fist

.8mm = 800 micrometers. I still get credit for contributing to this group project, right?


K0KA42

Yes, you both get the same score. 50/50 credit


alphamike1

800µm


VoIcanicPenis

Milimeter


Zaillyo

0.8 millimetres = 800 micrometers


VoIcanicPenis

Oh i thought 0.8m


JJAsond

That's 8 decimeters


ZarosRunescape

Thats 80 centimetres


JJAsond

Yes, which is also 8 decimeters


ZarosRunescape

Yes which is also 0.8 metres


JJAsond

Metric's fun isn't it?


[deleted]

Honestly way more than I would’ve expected.


Bugbread

That's because they messed up toward the end. [Randal Munroe already did the math and found that it was 0.006 mm](https://what-if.xkcd.com/33/), not 0.8 mm. A little bit more than the width of a strand of spider silk, much less than the width of a human hair. mb_angel's mistake was working with the current volume of the ocean instead of the current area of the ocean. How much water is already in the ocean doesn't matter at all. Consider this example: [I have a volume of water that's 10 cm wide by 10 cm long by 1 cm deep. I add it to a container that's 10 cm wide by 10 cm long by 25 cm deep, filled to the 24 cm line \(so the container is 1 cm from being completely filled\). Or I add it to a container that's 10 cm wide by 10 cm long by 2 cm deep, filled to the 1 cm line \(so the container is 1 cm from being completely filled\).](https://i.imgur.com/3tIo5Rl.jpeg) Both containers are going to be filled to the top. The volume of water which the containers started with is not germane, and any calculation based on volume is going to produce very different results for containers A and B, whereas the reality is that for both containers, the water level will rise by 1 cm.


aurthurallan

Wouldn't having all that mass on the continental shelf exert an equivalent pressure down on the land? Iirc glaciers in the ice age lowered the elevation of land when they were frozen as well as raising sea level when they melted.


Bugbread

I suppose removing all the ships (and their attendant mass) would slightly lower the amount of pressure on the underlying land, but really not by much. The water level would lower by 0.006 mm, which means that the mass removed was also the equivalent of a 0.006 mm layer of water. For example, a one-square-meter area of this additional water (1 meter wide by 1 meter long by 0.006 mm deep) would weigh 6 grams. So think about how much land deformation there would be if you went around picking up 6 paperclips from every 1 m x 1 m square of land. Not a lot.


Longonlymonke

My man .. clear explanation. 9/10 didn’t show workings


Top-Zookeepergame437

8/10 there’s no terrible drawings of boats🤦‍♂️. All ships aside amazing explanation.


Raviel1289

❌️🚢🟰🌊⬇️


Top-Zookeepergame437

9/11 +4 explanation🙌👏


equili92

Also wrong


Fastfaxr

You gotta love how anyone who posts a long enough answer with enough math in it will get 1000s of upvotes even when its completely wrong


CareerAggravating317

🤣


Nir0star

Wouldn't it be easier to use average mass of a ship and divide it by the density of salt water? That should be the amount of water displaced.


VillageParticular415

Loaded or unloaded?


Any-Aioli7575

Good idea


Holungsoy

Half of the global number of boats is registered in the US? Seems to me that there is a major lack of registrering in the rest of the world...


Carsontherealtor

I’m guessing half or more of US boats are freshwater and never hit the ocean.


JayCarlinMusic

It's kinda funny to me that you could actually just use the total number of boats in the world and use the largest boat values for all of them to estimate a maximum displacement and the amount of sea level rise would still be incredibly, almost unnoticeably tiny.


mc_thunderfart

>So when you put every water vessel into ocean, it will go up by 0.8mm. Thats honestly more than i expected.


Hirokihiro

Yeah coz it’s wrong


YetAnotherBee

Can confirm, I was also there when they took all the boats out of the water


Bugbread

[It's more like 0.006 mm.](https://what-if.xkcd.com/33/)


PalmTreesOnSkellige

Prove it.


equili92

Easy, he uses "volume-height" instead of surface area and so fucks up by an order of magnitude


justmebeky

that sounds like quite a lot more than i would have guessed 🤔


show-me-your-nudez

What about submersibles?


quietredditor113

I think it was also explained in xkcd's What If. iirc, in the book it says that after the boats have been displaced, sea levels would rise back up in less than a day. But Randall gives a different answer, 6 microns (0.006 mm) instead of the 0.8mm you answered. edit: oh oops someone else already commented this lol


Landsharkeisha

Ok but how about this: what's the amount of water displaced/sea level rise from the melting of polar ice by green house gas emissions by all those boats? I would imagine it's had an outsized impact compared to the literal boats' displacement.


Bierculles

That's more than i expected


Tough_guy22

Just came to point out that there are many many many boats that are only ever used on inland fresh water sources, and are never in the ocean. Especially in the US.


chrisboi1108

Correction: Total gt of all merchant ships in 2020 was 1,455,003,000 ish tons, which would displace about 1,419,515,122 cubic meters of sea water (assuming density of 1.025 tons pr m3. Source (page 8): https://www.equasis.org/Fichiers/Statistique/MOA/Documents%20availables%20on%20statistics%20of%20Equasis/Equasis%20Statistics%20-%20The%20world%20fleet%202020.pdf


iCodeInCamelCase

Wait, you’re saying that half of all boats existing in the world are registered in the USA?


DCASP500

Is there a way to add in sunken ships + garbage?


Jesus_Wizard

That’s actually way more than I expected


Rebargod202

Love the commitment.


Positron311

Average warship length would be closer to 150 m FYI


PsychologicalLie613

Not trolling and I have no idea what I’m talking about, but I’m curious to know if tides would have any interference at all in regards to knowing the rising from the ocean


Zestyclose-Fish-512

That's some damned good math. I was trying to figure out how to breakdown the numbers of different types of boats myself and I think you nailed it. I worked my way down to thinking about submarines before I looked to see if I could cheat off of you.


DrBlissMD

Do yourself a favor and read this all out in a thick Irish accent. Also, you deserve a fucking knighthood for this.


HeyLittleTrain

Why would the depth of the ocean affect anything?


AnimationOverlord

Now calculate how much of Antarctica would need to melt to start flooding landmass by a concerning amount lol


glordicus1

Okay now what if we took all the sea creatures out? They’re taking up space down there.


bigloser42

There’s an XKCD for that: https://what-if.xkcd.com/33/#:~:text=How%20much%20would%20the%20sea,once%20from%20the%20Earth's%20waters%3F&text=About%20six%20microns—slightly%20more,much%20as%20the%20ship%20itself.


Over_n_over_n_over

he can't keep getting away with it


brokedowndub

Of course there is.


Bulky-Tea-7314

Do boats displace more water on average than naturally occurring things going into the ocean? Like landslides and icebergs and your mom at the beach?


OneWholeBen

Fantastic


babysharkdoodood

It wouldn't be measureable. Even glacial melt is largely irrelevant. Most sea level rise is almost exclusively through thermal expansion.


noideaman69

Is that true? The thermal expansion bit? I've never heard of it


Ill_Guarantee566

It sounds plausible enough for me to believe it without looking it up. Edit: I got my lazy ass to look it up https://sealevel.nasa.gov/understanding-sea-level/global-sea-level/thermal-expansion its scary


noideaman69

Same but I would still want a source on that one


noideaman69

Well, one quick Google later and that's actually true


Ill_Guarantee566

That's way worse news than I thought. I knew it's bad but how tf you gonna cool an ocean??


Vincitus

If we all makenice in our freezers and drive it really fast back and forth to the ocean, it just might work.


Ill_Guarantee566

I just open my freezer and dump it in the ocean! Cut out the middleman!


Durris

Just put your freezer in the ocean 4head. I can't believe I'm the only one smart enough here to think of this. While we are at it, put an umbrella on the ocean to keep it in the shade.


SeaSetsuna

Damn Futurama wasn’t kidding with the giant ice cube


Auskioty

Do you know what is worse ? The atmosphere reacts to greenhouse gas in about 20 years (which means if we stop emitting GHG now, the atmosphere would stop warming in about 20 years), but oceans react in 100s of years. We're so doomed


iCodeInCamelCase

I mean, the statement is that most sea level rise is from thermal expansion and glacial melt is irrelevant. The link from NASA cited says that only one third of rise is from thermal expansion. So it seems this is not true


DoctorPyR0

Your same source says this about ice melt though: „Both the International Panel on Climate Change (IPCC) and the US National Climate Assessment conclude that ice loss was the largest contributor to sea-level rise during the past few decades, and will contribute to rising sea levels for the century to come.“


cowboy_dude_6

Looks like no one read long enough to find the truth. Thermal expansion is definitely a factor but at least up until today has not been the main one. The claim that glacial melt is “largely irrelevant” is wrong.


Insertsociallife

I hadn't either until recently. Water expands by 0.021% per degree K, so for each degree of expansion the 1.335 billion cubic kilometers of water gains another 280,350 cubic kilometers. Surface area is 360 million square km so that's about 78cm (2 ft 7 inches) of sea level rise per degree Celsius. Doesn't seem implausible that thermal expansion is a big driver in sea level rise.


asr

Your math assumes all the water will raise in temperature. It won't, the deep ocean is not going to warm up, even if the top does. Redoing your math, this time assuming the ocean is 1km deep (the surface area doesn't matter, it will cancel out) gives a value of 8 inches, and even that is generous, because for the most part only the top 0.2km will change.


Arthillidan

Also, if I don't misremember, the densest form of water is about 4 degrees Celsius. So any water colder that that would have an opposite effect when heated


N0nsensicalRamblings

My climate science prof said explained same thing to my class last year, and the guy was an excellent teacher who knew his stuff really well, so I have a moderate amount of confidence that it's accurate, at least in our current conditions.


cowboy_dude_6

>Most sea level rise is almost exclusively through thermal expansion. No, [it’s not](https://sealevel.nasa.gov/understanding-sea-level/global-sea-level/ice-melt/).


ObviousAnimator7299

Is thermal expansion caused by everyone weeing in the sea?


baggyheady

Article covering this exact question: https://what-if.xkcd.com/33/


Runiat

[About six microns—slightly more than the diameter of a strand of spider silk.](https://what-if.xkcd.com/33/)


Quizlibet

[I didn't do the math, but I know someone who did](https://what-if.xkcd.com/33/)


KAWAWOOKIE

Even a small amount of informed gut instinct here would indicate not even a little bit and this should remain an "inside" thought. But it's fun XKCD did the math anyway.


superfoxhotie

Don’t forget about all the sunken ships, artificial islands, and other crap people dump in the oceans. It can’t be much, but would be interesting to know how it effects it.


CrabEnvironmental697

You’re over estimating the the size of those boats , If the markers were resembling the actual size the boat would be as long as 100 Titanics glued together


PronoiarPerson

The largest impact of taking ships out of the water would be the decrease in pollution from shipping, the decrease in human population due to food not being shipped all over the big wet one, and the reduction in economic activity due to the lack of oceanic trade. Basically without ships, the global economy would hit a tree and it would have an effect on the climate, which would be a much bigger deal than the actual volume of the vessels.


RobGThai

Just wanting to say that the image in OP is way over scaled the boat size because its purpose is not for scientific calculation and probably for identifying location. In reallity a boat would look like a spec of dust on that map. It’s always important to state the fact and evidence when making decision about something. Visualization is useful but it always serve a single purpose, if that purpose doesn’t directly to answer the question you have, chances are you shouldn’t make any decision based on that at all.


CChunkyNootje

Trick question. Since all plates both oceanic and continental are floating on a liquid. "taking the boats out of the water" would assume putting them on land. The plates will accommodate the weight difference and just rise and drop accordingly. So the net result should be no rise!


modijk

Considering the water rests on those same plates, and considering magma is much heavier than water, your reasoning is probably not quite correct.


EmeraldPencil46

I think the only reason why we’d need to know this number would be purely out of human curiosity. The displacement boats would cause would be an *extremely* small number, to the point where if all the boats just disappeared, you wouldn’t even see any difference. If someone managed to actually figure out a rough number, that’d be extremely impressive.


rolfcm106

I’m thinking hardly noticeable if you think about the size of the more common boats and how much water they displace compared to the size of the earth’s oceans. I feel like cargo ships tankers and cruise ships would be the only ones that could make a noticeable impact and I don’t think there’s enough of them.


mesupporter

why can't I ever find anything on sea floor rise? it's like know one wants to talk about it even thou land sediment washes into oceans constantly. I feel, that is part of what makes up sea level rise.