“A clock accurate to a second over the age of the cosmos would allow tests of whether physical laws and constants have varied over the universe’s history,” says physicist Patrick Gill. https://harpers.org/archive/2023/04/the-science-of-the-perfect-second/?src=longreads&utm_source=Live+Audience&utm_campaign=3fb1c5122a-briefing-dy-20231222&utm_medium=email&utm_term=0_b27a691814-3fb1c5122a-50179668
