The universe is expanding, that doesn't mean items within it grow, they just distance themselves from eachother and that we do observe.
Imagine a balloon you put some marbles into while it's completely deflated. Now inflate the balloon. Marbles stay the same size but the space between them increases.
quax747 t1_jefnd6o wrote
Reply to Eli5 if the universe is expanding, then why isn’t the earth, and everything in it (us) getting measurably bigger too? by Far-Contribution-632
The universe is expanding, that doesn't mean items within it grow, they just distance themselves from eachother and that we do observe.
Imagine a balloon you put some marbles into while it's completely deflated. Now inflate the balloon. Marbles stay the same size but the space between them increases.