Main Page

Welcome to the explain xkcd wiki!
We have an explanation for all 3209 xkcd comics, and only 60 (1.9%) are incomplete. Help us finish them!

 Go to this explanation

Latest comic

Chemical Formula

|< < Prev #3200 (January 28, 2026)

Title text: Some of the atoms in the molecule are very weakly bound.

|< < Prev Random Explanation

Explanation

The supposed "chemical formula for the universe" merely lists the numbers of atoms of each element. As is common practice for real compounds that contain organic structures or substructures, the numbers of atoms of carbon and hydrogen are listed before all of the others; the others are listed in alphabetical order. There are estimated to be 10⁸⁰ atoms of hydrogen (H), by far the most common element in the universe. The next most common element, helium (He), is a long way to the right in the list, and out of view, but would be about a third as many as the hydrogens.

These numbers are large, but they are not nameless. Using the short scale, these numbers can be described as:

• C_10⁷⁶ - Ten quattuorvigintillion carbon atoms
• H_10⁸⁰ - One hundred quinvigintillion hydrogen atoms
• Ac_10⁶⁷ - Ten unvigintillion actinium atoms
• Ag_10⁶⁹ - One duovigintillion silver atoms
• Al_10⁷⁵ - One quattuorvigintillion aluminium atoms
• Am_10²⁶ - One hundred septillion americium atoms
• Ar_10⁷⁵ - One quattuorvigintillion argon atoms
• As_10⁷⁰ - Ten duovigintillion arsenic atoms
• At_10⁴⁷ - One hundred quattuordecillion astatine atoms
• Au_10⁶⁹ - One duovigintillion gold atoms
• B_10⁷¹ - One hundred duovigintillion boron atoms
• Ba_10⁷⁰ - Ten duovigintillion barium atoms
• Be - An unknown quantity of beryllium atoms

The matter originally created in the Big Bang was bare, unbound protons and neutrons. In the first few minutes, some of these combined to form lightweight nuclei, but most remained as protons, i.e. the nuclei of hydrogen atoms. Other, more complex atoms formed later as a result of stellar nucleosynthesis.

This may be poking some fun at the relative usefulness (or rather, uselessness) of chemical formulas for large organic molecules. While it is a useful concept for teaching people about chemistry and balancing equations, and it was useful in the early days of chemistry to try to categorize and learn about molecules via stoichiometry - it does not give much useful information. For example even the simple formula C11H15NO2 has 302 registered isomers. Many of them are NOT good to eat.

Transcript

[A long panel with a chemical formula trailing off the right side]

C_10⁷⁶ H_10⁸⁰ Ac_10⁶⁷ Ag_10⁶⁹ Al_10⁷⁵ Am_10²⁶ Ar_10⁷⁵ As_10⁷⁰ At_10⁴⁷ Au_10⁶⁹ B_10⁷¹ Ba_10⁷⁰ Be

[Caption below the panel:] The approximate chemical formula for the universe

---

        View comic discussion

New here?

Last 7 days (Top 10)

Rank Score Pages Changes Username 1 28 23 29 TheusafBOT 2 16 13 16 Natg19 3 16 9 22 Elizium23 4 13 6 17 BunsenH 5 8 6 7 FaviFake 6 8 5 7 DKMell 7 7 5 6 Elektrizikekswerk 8 6 2 7 Megan 9 6 4 5 Qwertyuiopfromdefly 10 5 5 5 Victoria

Lots of people contribute to make this wiki a success. Many of the recent contributors above have just joined. You can do it too! Create your account here.

You can read a brief introduction about this wiki at explain xkcd. Feel free to create an account and contribute to the wiki! We need explanations for xkcd comics, characters, What If? articles, and everything in between. If it is referenced in an xkcd comic, it should be here.

• If you're new to wiki editing, see the explain xkcd:Editor FAQ for a specific guidance to this wiki and the more general help on how to edit wiki pages. There's also a handy wikicode cheatsheet.

• Discussion about the wiki itself happens at the Community portal.

• You can browse the comics from the list of all comics or by navigating the category tree at Category:Comics.

• The incomplete explanations are listed here. Feel free to help out by expanding them!

Rules

Don't be a jerk!

There are a lot of comics that don't have set-in-stone explanations; feel free to put multiple interpretations in the wiki page for each comic.

If you want to talk about a specific comic, use its discussion page.

Please only submit material directly related to xkcd and, of course, only submit material that can legally be posted and freely edited. Off-topic or other inappropriate content is subject to removal or modification at admin discretion, and users who repeatedly post such content will be blocked.

If you need assistance from an admin, post a message to the Admin requests board.