Should I backup gradle dependencies to git?

I always like to backup project dependencies myself in case they can't be resolved due to a down website or because certain versions aren't available for download any more.

Should I trust the maven central repository to be up and running when I try to build my project in 2020? Or should I backup dependencies manual?

If I should backup manual, then where does gradle store the downloaded dependencies? Or does gradle come with an build in solution for this?