Blueberry Earth

This paper explores the physics of the what-if question “what if the entire Earth was instantaneously replaced with an equal volume of closely packed, but uncompressed blueberries?”. While the assumption may be absurd, the consequences can be explored rigorously using elementary physics. The result is not entirely dissimilar to a small ocean-world exo-planet.

Here is the full analysis, via M.

Comments

Author: "Given how exotic exoplanets have turned out, the physics of blueberry earth is actually fairly normal compared to much that is out there." Out where? In space? Or in science? If tech billionaires fund scientific research, "this kind of exploration is worthwhile", to find both the science of (their) longevity and of (their) home in the stars.

I hope I did not subsidize this research.

Your tax dollars fund your local fire department, which includes large, heavy, disc-shaped lumps of iron that the firefighters lift up into the air, bring back to the ground, lift back up, bring back down, ad infinitum. This seemingly pointless, repetitive process is known as "weightlifting".

I simply assert that if you're okay with your local police and firefighters lifting weights, you shouldn't have a problem with academics and intellectuals engaging in hypothetical thought experiments, including exercising their brainpower on analyzing blueberry planets.

"This paper explores the physics of the what-if question “'what if the entire Earth was instantaneously replaced with an equal volume of closely packed, but uncompressed blueberries'".
Ah, OK then.

Consultants have been solving the problems of packing golf balls into 747s for ages. So for a physicist to solve this hypothetical problem does not seem too far of a stretch.

It is different. Golf balls and airplanes actually exist. Strawberry-made planets do not exist.

Pay attention Thag! Blueberries not strawberries. Better, imagine Brazil replaced by a big blue blueberry.

It is impossible.

"This paper explores the physics of the what-if question “what if the entire
Earth was instantaneously replaced with an equal volume of closely
packed, but uncompressed blueberries?”"

We'd all die a rather sudden and horrible death?

Yeah, a gradual replacement offers the possibility of some good pies, muffins, and maybe a cobbler or two on our way out. That's the much more intriguing scenario here.

Thread winner!

How do we know there are no blueberry planets? All we know is based on our own experience, and that does not include a blueberry planet. The point of the research isn't blueberry planets, but planets unlike our own. I am old enough to remember that the moon was made of cheese. That was in a time when people had more imagination than they do today. Blueberry planets, cheese planets, they may be more hospitable to life than our own sometime in the not too distant future.

In the multiverse, blueberry planets haven't only happened, they have happened an infinite number of times.

And yet every single time, they were inferior to strawberry planets. Unfortunately in both cases, the very high chemical state of the matter resulted in an extreme amount of volcanic activity. Which we call juicy burst.

Maybe Trump supporters should move to a vanilla planet cuz you know racists.

There is an old chestnut about the mass of a mole of cats (it is just under half of the earth’s) and a geochemistry professor I once had asked a very open ended question about the geochemical composition of such a planet, giving a breakdown of what elements make up a cat and their relative quantities. It was a very good exam question.

This was great. Thanks for sharing. My kids will love hearing about it as they're constantly coming up with ridiculous situations and trying to figure out their implications.

I believe xkcd has a book out which is a collection of serious treatments of crazy questions asked by kids, like 'what would happen if the moon disappeared?' or 'how much would it cost to build a ladder to the top of Mt. Everest?' It's pretty entertaining.

Yes, the book is great- perfect gift for someone who loved high school physics.
There's a website too. Relevant to the comment upstream, what if there were a more of moles?
https://what-if.xkcd.com/4/

The author seems to be a Norwegian, given his name, with a small probability of either Swedish or Danish. Should I criticize a fellow viking? (After looking, I found he's a Swede!)

Hell yes!

He writes: "Note that these are the big, thick-skinned highbush blueberries (Vaccinium corymbosum) rather than the small wild thin-skinned blueberries (bilberries, V. myrtillus) I grew up with; the latter would have higher unpacked density due to their smaller size and break far more easily."

Unless there is some unstated assumption, the author seems to think the density (packing efficiency) of spheres depends on the size of the spheres. That is patently incorrect!

Anyway, the uncertainty in density does not materially alter any of the following conclusions, the paper is pretty interesting, and quite impressive for somebody who is not a physicist!

What if all the Blueberries are mixed sizes? Does that allow packing density to change much?

Yes, and if you use discrete sizes with a large difference, it is easy to demonstrate how.

First with a single size, the packing density of spheres is around 0.74.

https://en.wikipedia.org/wiki/Crystal_structure

Assume 2 discrete sphere sizes S1 >> S2. To be clear (not patronizing!), ">>" means "much bigger". Starting with the S1 sized spheres, the packing density is about 0.74 or 74%, leaving 0.26 empty. Now start packing the S2 sized spheres in the remaining gaps. At this time, the final density is 74% + 74% of 26% ~ 93%. If you continued with spheres of size S3 << S2, you could further increase the packing density. At some point, this scheme would break down, as you start wanting spheres that are smaller than individual atoms. But as a starting point, bowling balls + marbles + sand will stack more densely than just marbles.

https://en.wikipedia.org/wiki/Sphere_packing

(Pedanting tone off, and those that studied materials science or solid state physics or advanced math or chemistry, sorry to bore you!)

Remember the Professor in Cat's Cradle who found a more efficient packing.

The author notes there are many more avenues to research, so clearly more funding is needed.

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