This Is How Much Dark Matter Passes Through Your Body Every Second

[Judi Lynn]

Ethan Siegel
#Cosmology Science writer, astrophysicist, science communicator & NASA columnist.
Jul 10

This Is How Much Dark Matter Passes Through Your Body Every Second
There’s a halo of dark matter permeating every galaxy, and that means its particles pass through us, too.


The Universe, despite all the planets, stars, gas, dust, galaxies, and more we find within it, doesn’t quite add up. On the largest cosmic scales, we find the same story everywhere we look: there isn’t enough matter to account for the gravitational effects we observe. Matter clumps into a cosmic web; galaxy clusters grow to enormous sizes with fast-moving galaxies inside; individual galaxies rotate at large speeds that remain large all the way to their edges.

Without the presence of about five times as much matter as protons, neutrons, and electrons can account for, none of this would be possible. Our picture of the Universe requires dark matter for self-consistency. Yet, if dark matter is real, that means our Milky Way has a dark matter halo, too, and some of that matter passed through the Solar System, Earth, and even you. Here’s how to know how much is inside you right now.

Back in the young Universe, everything was hotter, denser, and more uniform than it is today. Early on, there were regions of ever-so-slight overdensity, where there was a greater-than-average amount of matter there. Gravitation preferentially attracts more matter to a region like this, but radiation works to push that matter back out.

If all we had was normal matter and its constituent particles to go with this radiation, the galaxies and galaxy clusters that exist today would be vastly different than what we observe. But if dark matter is present in this 5-to-1 ratio with normal matter, we can theoretically reproduce the cosmic web of structure to match our observations and measurements.

More:
https://medium.com/starts-with-a-bang/this-is-how-much-dark-matter-passes-through-your-body-every-second-c4aca24f288c

[byronius]

1. Cool article.

[yonder]

2. Interesting on the skim, bookmarked for later. Thanks JL

I'm halfway through a Neil deGrasse Tyson book "Astrophysics for People in a Hurry". In it, he explains how we and our knowledge got to where we are at today, in a fairly understandable manner. Basically it is an easy read.