# What size is the largest known molecule anywhere in the universe?

I understand that generally, beings get as big as the thing(land, sea etc)they live on or in however another celestial object can interfere with size, like the moon and ppl got smaller. But can a molecule somewhere completely foreign to this realm be for instance as large as a dog or horse, human or house? Large enough to see with the naked eye?

• different but somewhat related: What is the maximum amount of carbon atoms that can comprise a fullerene?
– uhoh
Dec 21, 2021 at 11:00
• "I understand that generally, beings get as big as the thing(land, sea etc)they live on or in" I would say it is the other way around! Yes, you see bad science fiction which have a huge planet with huge aliens but,in fact, any creatures living on a huge planet would be very small because of strong gravity.
– gene
Dec 21, 2021 at 13:13
• @gene but what of flying creatures that live within a gas giant's "atmosphere"? It could be a massive planet with minimal density, i.e. Jupiter only has 2.4 times the gravity of Earth "at it's surface", while being 11 times larger. Just saying, I don't think it's black and white, and large beings can exist on a large planet without any "bad science" Dec 21, 2021 at 18:43

Polymers can be as large as you like.

Th best examples are probably car tyres or other rubber objects which are (mostly, probably) one large cross-bonded molecule. A textbook example (literally) is a bowling ball. Of course, those tend to have other layers underneath, but the principle is there - and comments have found some impressive ones.

A polymer is a chain of monomers (hence the name), where each unit is pretty much the same as the next. Occasionally, the head of a chain binds to something that isn't a monomer, and it ends. (Or perhaps manages a complete loop.)

However, carbon-based chemistry has up to four different covalent bonds from a single atom, and so you can "decorate" your polymer strand with other things which are still chemically part of the same molecule. If one of those things happens to be a link to another polymer strand, you now have two chains which are, in theory, part of the same molecule. If you mix in a lot of "cross-link me" and "fork the chain" impurities so that any given chain links to an average of two dozen others, it's easy to see how virtually all the chains will be connected to each other somehow.

On a typically-smaller note, still working with covalent-bonded carbon:

Graphite (as found in pencils) is a flat-sheet and a single molecule. It may form in non-earthlike atmospheres as a kind of snow.

Diamond is three-dimensional, and works on the same principle. If you're willing to settle for a crystallised stellar remnant, then a 4000km molecule is about 50ly away, apparently known as "Lucy". (Link in comments, credit where it's due.)

Some designs for a space elevator based on carbon-filament cables stretching into orbit would count. These are made as covalent-bonded structures because fibres tied to each other just can't handle their own weight when they're supporting over 100km of cable.

• polymers would be my answer as well. under my definition of a molecule (atoms bonded together by covalent bonds). graphite and diamond would count as well under that definition. if on the other hand you adopt a looser definition of (atoms chemically bonded) then additionally any 'welded' metal and crystal will count. Dec 21, 2021 at 9:06
• Here's a good picture of 3 giant rubber molecules that you can add to your post: assets.newatlas.com/dims4/default/25f4905/2147483647/strip/true/… Dec 21, 2021 at 14:56
• On this principle, I think I've seen it claimed somewhere that the largest molecule is therefore almost certainly the world's largest car tyre. One was apparently constructed at 24.4m tall for a Uniroyal promotion: bigtyres.co.uk/blog/worlds-largest-tyre.html Dec 21, 2021 at 16:59
• I think bowling balls might have you fooled. youtube.com/watch?v=aFPJf-wKTd0. They are way more complicated than a single molecule Dec 21, 2021 at 20:58
• Lucy is pretty big. But Lucy isn't strictly a polymer, since its just one element...
– Aron
Dec 22, 2021 at 4:30

While no longer in the realm of chemistry a neutron star would also sort-of count. And here you are talking about a significant fraction of a Sun-size star's mass.

• Hmm, I think that a molecule must at least be made out of atoms. Dec 21, 2021 at 7:49
• @PostlimFort That strains the definition of 'atom' a bit too far IMHO. An atom should be the smallest possible division of an element. Dec 21, 2021 at 10:15
• @PostlimFort IUPAC does not recognise an element with atomic number zero; they stipulate that an atomic nucleus must be positively charged. However, the unofficial name neutronium is sometimes used for this substance. Dec 21, 2021 at 13:23
• neutrons are atoms - definitely not. neutrons are one of the building blocks of atoms. that's like saying tires are cars Dec 21, 2021 at 17:32
• @FranzGleichmann Neutron stars aren't made exclusively of neutrons. True, deep under the surface, pressure from the gravitational weight of the mass above it exceeds the electron degeneracy pressure, and thus electrons collapse into protons, forming neutrons. But you will notice that the shell of the neutron star does NOT have such pressure. Therefore, there are protons and electrons on the shell of the neutron star, which means that a neutron star is not "atomic number 0". A better counter to "neutron star are atoms" are that they aren't held by atomic forces.
– Aron
Dec 22, 2021 at 4:24