3240: Bottle

Bottle

|< < Prev #3240 (May 1, 2026)

Title text: "I know it seems impossible, but the trick is that I sailed in here when I was very young."

|< < Prev Random Explanation

Explanation

This is one of 69 incomplete explanations: This page was bottled recently. Don't remove the cork too soon. If you can fix this issue, edit the page!

This comic shows a life sized ship in a bottle sailing along with other sail boats in the sea. The humor comes from the surreality of the situation.

In this comic, Beret Guy is inside a ship in a bottle. A common question when one sees one is "how was it put inside the bottle", due to the small size of the opening in the bottle compared to the ship. The answer is that the ship was assembled (or at least partially unfolded, from more compact original components assembled outside) within the bottle. The components are small enough to pass through the neck of the bottle, and the assembly is likewise done from outside through the neck, usually a difficult task. The title text alludes to this, by saying that Beret Guy grew up inside the bottle to fit (however, this is nonsensical, as he could likely fit into the bottle anyway, and ships do not grow as living things do). On the other hand, it would probably be easier for someone inside the bottle to assemble components of a ship there than for that assembly to be done from outside. This would especially be true of a seaworthy vessel of a size to carry a passenger, rather than a mere model.

The water level in the bottle is lower than the water outside. This is because the bottle will sink until the weight of the bottle and its contents (the water, the boat, and Beret Guy) equals the weight of the water displaced by the bottle. The weight of the missing water in the bottle is consequently equal to the weight of the bottle, the boat, and Beret Guy. If you added water to the bottle in an attempt to make the inside and outside water levels the same, the bottle would just sink deeper. This would continue until the boyancy became less than zero at which point the bottle would sink.

In practice, the bottle is horizontally unstable. The weight of the bottle is not equal along its length (it appears heavier at the neck), and the boyancy at each point will not equal the weight at that point. This is also true of the boats in the cartoon, the difference is that in the bottle much of the weight is the water which is free to move. If the neck of the bottle goes down (to increase the displacement to balance the weight), the water will move to the front of the bottle. This increases the weight at the front which will force the front even deeper. This will continue until the bottle is floating vertically. Beret Guy's boat would appear to fit in the width of the bottle so everything will be fine. This effect (known as the 'free surface effect') has real implications for ships with open decks, such as car ferries, and has been implicated in several disasters such as the 'Herald of Free Enterprise', the 'Princess Victoria', and the 'Estonia'.

Transcript

This is one of 44 incomplete transcripts: Don't remove this notice too soon. If you can fix this issue, edit the page!

[Three small single-masted sailboats are shown, all sailing towards the right. The ones on the left and right are on the ocean, while the one in the middle is contained completely by a large bottle. On the left, Cueball and Megan are in one boat; Cueball is near the stern, possibly holding the tiller, while Megan is before the mast. In the middle, Beret Guy is before the mast in the boat that's inside the giant bottle, with a cork plugging the bottleneck. On the right, Ponytail is directly aft of the mast of the third boat. All the boats are sitting on the water with ripples on the surface, but the water level in the bottle is lower than the rest.]

  Add comment        Create topic (use sparingly)       Refresh 

Discussion

So... is the meniscus drawn correctly, given the difference in shape of the front vs the back of the bottle??? BorQhue del Sol (talk) 18:54, 1 May 2026 (UTC)

Left-hand threads on bottle. Why? --PRR (talk) 18:49, 1 May 2026 (UTC)

I don't think those are threads on cap, they're wires around the cork. Barmar (talk) 19:19, 1 May 2026 (UTC)

I think it's a (perhaps reverse-threaded) screw-top bottle with no actual screw-top and a cork inserted instead. 81.179.199.253 21:36, 1 May 2026 (UTC)

this transcript is a work of art. raeb 18:54, 1 May 2026 (UTC)

Is part of the joke of the alt text the fact that he could easily fit into the bottle at his current age? 24.244.70.174 18:58, 1 May 2026 (UTC)

If he sailed in when he was very young, does that mean the ship grew up with beret guy? Commercialegg (talk) 18:59, 1 May 2026 (UTC)

That does seem to be what he's implying. When he sailed in, the boat must have been small enough to get through the bottleneck. Barmar (talk) 19:15, 1 May 2026 (UTC)

It's a reference to Williams pears, which do grow inside a bottle like that.37.59.41.98 19:41, 1 May 2026 (UTC)

Could it be that the boat inside the bottle is the one talking, not Beret Guy? SovereignFinn

It may be worth noting that Beret Guy's boat's sail visibly isn't getting any wind, which of course makes sense. Also, I like that Ponytail's boat has a gaff rig. 63.229.212.46 20:33, 1 May 2026 (UTC)

Off-screen, they are all in an even larger bottle. Fephisto (talk) 16:46, 2 May 2026 (UTC)

I see a totally different context and joke here: the water level in the bottle is lower than the water level outside. (Which requires a bit of physics thinking to figure out why this would be so.) At first intuitive glance, the water levels should be the same, hence, as the title text says "... seems impossible ...". Then the title text offers a (wrong, but intuitive) explanation for the different water levels: he entered the bottle at very young age when he was lighter (equal levels). Now as an adult he is heavier, thus the whole bottle is heavier and hence it is dipping deeper into the outer water (creating different levels). 31.16.254.255 20:38, 1 May 2026 (UTC)

I think it's sort of what would happen with a glass bottle. Glass is far more dense than water. If you part-filled a bottle (sideways, supported) so that it is level with the water it is sitting in and then plug it and release it, the air-filled bottle would then sit lower in the water than its previously established level.

i.e. the trapped water itself is neutral, versus the volume of external water that it displaces. The bottle-material that is below that level is denser than the water it directly displaces, so is negatively buoyant (and the above-the-water glass is less buoyant than the external air). It needs to sink enough that the internal air is also contributing to the displacement of the whole sealed bottle enough to equalise the whole thing.

And, the marvelous thing is that the bottled boat itself is completely neutral. As it's floating at a level that is neutrally buoyant across the (internal) water+air interface, so long as it is floating, thus the whole container weighs (as well as displaces) the same, for any given internal water-level. (i.e. how boat lifts operate... two 'troughs' that essentially weight the same regardless of whether they have a boat in them, that can be hauled up and down essentially perfectly counterbalanced by the paired trough going in the opposite direction. Which I still think is rather clever.) 81.179.199.253 21:36, 1 May 2026 (UTC)

Hi, new here, thanks for explainxkcd. Not sure about this sentence: "The weight of the missing water in the bottle is consequently equal to the weight of the bottle, the boat, and Beret Guy." I think the weight of the missing water is actually a bit less than the weight of the bottle. Here's the reasoning. First, imagine a bottle containing only water, no boat. We know that the weight of the displaced water equals the weight of the empty bottle plus the water inside (m_wd = m_b + m_wi, dropping earth gravity on both sides). And we know that the volume of the displaced water equals the volume of the bottle walls underwater plus the volume of the water inside plus the volume of the missing water (V_wd = V_bu + V_wi + V_wm). Multiply the latter by the density of water to get m_wd = rho_w * V_bu + m_wi + m_wm, and set equal to the first equation to get m_b + m_wi = rho_w * V_bu + m_wi + m_wm, or: m_wm = m_b - rho_w * V_bu. In other words, the mass of the missing water equals the mass of the bottle minus the mass of water with the same volume as the submerged parts of the bottle walls. Second, we can now take water out of the bottle with the same mass as the boat and Beret Guy, and put in the boat and Beret guy. The water level inside the bottle will not change (as the amount of water displaced by boat and Beret guy is just the amount we took out). If the water level doesn't change when we insert boat and Beret Guy, the amount of missing water remains unaffected. In conclusion, the weight of the missing water in the bottle is a bit less than the empty weight of the bottle. More precisely, the volume of the missing water equals the volume of an amount of water with the same mass as the empty bottle, but reduced by the volume of the submerged bottle walls. Or not? Cheers, Fab 203.218.42.181 08:07, 2 May 2026 (UTC)

Did not see this until I (just) addressed that statement my own way. Slightly messily, but also trying to consciously remove BG+Boat from the basic equation (at least until the bottle is so filled that it starts pushing up on the bottle/the bottle pushed down on it, and BG needs to hope it had enough closed-cell buoyancy to not suffer too much from being flooded).

The internal water-level (the boat's 'plimsol line', flattening out the 'wavy nature' of the water) is effectively constant (for a given similar 'plimsol line' of the bottle w.r.t. to the open sea), regardless of whether the boat is there. The weight of water that the Boat+BG displaces (plus also the weight of the air), by being there, is the total weight of the Boat+BG. Without B+BG, but the same water level, the water and air volumes that fit into the appropriate gaps (no 'bottle half empty'-type trickery allowed!) provides the same weight and volume.

So, to calculate the bottle-weight minus the weight of the water(+air) that the substance of the bottle-body (and cork!) already displaces, imagine the boat isn't there and 'weigh out' the water that would be there in the 'slice' between the two surfaces, within the bottle (as if the boat was not there, everything else the same). Then go back and find the volume of the total bottle-glass, consider that in terms of water-density (almost as accurate as accounting for which slices are to be given water-density equivalence, and which are to be 'converted' to air). Add that bottle-body water-weight to the surface-gap water-weight, and this equals the bottle(+stopper) weight, with Boat+BG not being a factor (so long as it is not at all grounded and/or 'ceilinged', within the bottle).

I'm sure with a bit of calculus, we could do the whole thing. Calculating the volume of rotation of the hollow-bottle-shape, assuming a degree of cylindricality of profile, and integrating the 'sideways slice of semi-cylindrical contents' that exists between the two nominal surface-planes (reducing the 'peak and trough' water profile to equivalent flatness-level, especially considering that this involves the intersection of surfaces sloping/curving in multiple directions, might be the most hand-'wavy' part of the estimation, that's trickiest to be sure about) is left as an excercise to anyone sufficiently nerd-sniped enough to actually plug numbers into this. But the concept, at least, seems 'simple' enough.

And it shows that Randall didn't lazily draw the same water levels through both. Though there are arguments that they need to be different, in order to emphasise the full isolation of the bottle interior from the open sea, it could also have been done with a higher internal water level than the outside (implying the bottle-material was significantly less dense than water, or even that it's an 'air gap' between two line-thick 'skins', or maybe that the 'air' in the bottle is hydrogen, helium and/or lower-pressure than outside or...). I choose to believe that Randall (without necessarily enumerating the degree of the effect) chose a 'realistic' outcome of a floating bottle with a small amount of water in its 'bilgewash' bottom. (Saving that the natural attitude of such a bottle is either neck-up or neck-down, but then RealityIsUnrealistic. Or at least less visually aesthetic.)

In fact, my only true concern is the attitude of the bottle. Sideways, as it is, smaller-BG could not have (as implied) sailed the smaller-boat into the neck, as it is now. Either there was more water originally (pumped out before BG then pulled the cork-stopper into place, or (knowing BG), he just drank it and... somehow, and without affecting his admitedly rather ambiguous personal density too much... 'retains' it all, still), or the bottle was tilted down at an angle (not vertical!) and he floated 'up and in' before/during the twist in which the bottle underwent its current 'leveling sideways' orientation. 82.132.239.222 09:28, 2 May 2026 (UTC)

Hover text

Is the hovertext also a potential reference to animals that get stuck within a particular location as they grow? I'm thinking hermit crab, but this might be an imagining. Kev (talk) 14:58, 2 May 2026 (UTC)

Hermit crabs don't get stuck in one location, as they grow, though. They go and find a suitably-sized 'upgrade' of shell (or useful piece of seafloor rubbish, if they find one of those that they like the look of), either unclaimed or about to be vacated by a larger crab who is lining up their own 'upgrade' (often as a chain of such stepwise upgrades).

At most, I'd expect it to be like "caught their neck in beer-can packaging, when young, get slowly strangled/garotted to death as they grow up with it still around their neck", rather than anything else. Some tree-hole nesting birds get effectively sealed in by closing the hole up with mud until it's more predwtator-proof, leaving only enough hole for their mate to give them/the eventual chicks bits of food (and chuck out waste), and no doubt creatures (like livestock) have escaped certain fenced/naturally-barriered areas when small and later couldn't get back through the gap if they tried to. And queen-insects of various kinds might be practically confined to the nests/hives in their fully developed 'egg-laying machine' form. But nothing that seems (to me) to have been directly or tangentially alluded to, to be honest. Though I might be missing something (other than already noted pears, and similar "bottled on the tree" novelty versions of such things). 82.132.239.222 16:42, 2 May 2026 (UTC)
        Add comment