3 ms·
Aside: I want to point out the currently known composition of the universe: ~5% matter. Most of this is H and He though, bit of Li in there too. And it's all m
by Balgair 4y ago
Aside: I want to point out the currently known composition of the universe:
~5% matter. Most of this is H and He though, bit of Li in there too. And it's all mostly burning in a star's gravity well. Like, 99.99999% of it. The stuff you and I are made of (C, N, P, Fe, etc), that we would wish aliens would be made of too, is really rare.
~25% dark matter. We know a little about it. We know that it falls down and doesn't like to touch just about anything. But that's really kinda it.
~70% dark energy. It falls ... up (?!). We know pretty much nothing about it. And it's the large majority of 'stuff' in the universe.
If there are friends out there, then we may want to look at stuff that is a bit more common than ourselves too.
- chiefalchemist 4y agoInteresting. It's not the vast size of the universe that matters. It's the concentration (or not) of particular elements that's (likely) the metric that matters. Good to know. Thx.
- gus_massa 4y agoNitpicking: Instead of Li, you probably mean He. From https://en.wikipedia.org/wiki/Abundance_of_the_chemical_elements https://en.wikipedia.org/wiki/Abundance_of_the_chemical_elem... > Hydrogen and helium are estimated to make up roughly 74% and 24% of all baryonic matter in the universe respectively. Despite comprising only a very small fraction of the universe, the remaining "heavy elements" can greatly influence astronomical phenomena. Only about 2% (by mass) of the Milky Way galaxy's disk is composed of heavy elements.
- andrewflnr 4y agoI don't know if they corrected their comment, but there's definitely some primordial Li out there along with the H and He. For example: https://en.wikipedia.org/wiki/Cosmological_lithium_problem https://en.wikipedia.org/wiki/Cosmological_lithium_problem
- gus_massa 4y agoMy guess is that I made a mistake and I skipped the "He" in the GP comment.
- russdill 4y agoDon't worry, there's a very timely periodic table for your viewing pleasure: https://xkcd.com/2723/ https://xkcd.com/2723/
- jvanderbot 4y agoTo me, if someone were to find that no life can be created out of 99% of the stuff in the universe (by mass) that would be a very unsurprising result. By some kind of power law argument, it doesn't strike me as particularly strange that the stuff that makes up life, a very complex chemical process, requires a sensitive mixture of the rarer components.
- Balgair 4y agoIt may be that our definition of life is then too narrow if it requires that life be made of chemical processes.
- jvanderbot 4y agoIt's not like our definition has any impact on reality, so "life as we know it requires chemistry" seems a reasonable starting point.
- QuantumGood 4y agoHumans as a percentage of all matter are even rarer than the element they are comprised of. For example, the biomass of ants on planet Earth is much, much greater than that of humans.