> why not just say "for every pound (or kilogram) of matter, there are roughly 5 pounds (or kilograms) of dark matter".
Your suggestion is better writing. As for why? Likely the author and editors rushed the content or lack strong skills in this particular style of writing. The author Paul Sutter seems to have a strong background in writing. The original sentence is awkward enough that it looks like it was written by one person and edited by another.
> Dark matter is the mysterious, unknown substance that seems to make up the bulk of all the mass in the universe; for every 2 pounds (1 kilogram) of regular matter, there's roughly 10 pounds (5 kg) of dark matter.
If I had to guess, I bet it only originally had one set of units and an editor added converted units to match some style guide. I doubt that Paul would have originally gone with
> for every 2 pounds of regular matter, there's roughly 10 pounds of dark matter.
Because 2:10 ratio is not a natural thing to write. He's an astrophysicist who did post-doc fellowships in Paris and Italy, so most likely he submitted an article with SI units:
> for every 1 kilogram of regular matter, there's roughly 5 kilograms of dark matter.
And I bet a livescience.com editor changed that to pounds to match a US-centric style guide.
Your suggestion is better writing. As for why? Likely the author and editors rushed the content or lack strong skills in this particular style of writing. The author Paul Sutter seems to have a strong background in writing. The original sentence is awkward enough that it looks like it was written by one person and edited by another.
> Dark matter is the mysterious, unknown substance that seems to make up the bulk of all the mass in the universe; for every 2 pounds (1 kilogram) of regular matter, there's roughly 10 pounds (5 kg) of dark matter.
If I had to guess, I bet it only originally had one set of units and an editor added converted units to match some style guide. I doubt that Paul would have originally gone with
> for every 2 pounds of regular matter, there's roughly 10 pounds of dark matter.
Because 2:10 ratio is not a natural thing to write. He's an astrophysicist who did post-doc fellowships in Paris and Italy, so most likely he submitted an article with SI units:
> for every 1 kilogram of regular matter, there's roughly 5 kilograms of dark matter.
And I bet a livescience.com editor changed that to pounds to match a US-centric style guide.