According to Wikipedia, our planet — the first “w” in www — is 4.54 ± 0.05 billion years old, which frankly seems like a pretty big margin of error, if you ask me. But hey, they weren’t exactly keeping records back then!
The 4.54 billion year estimate comes from many sources, which are cited in the same article. The first source cited is a US Geological Survey link that is indexed at web.archive.org. The USGS article begins by mentioning: “So far scientists have not found a way to determine the exact age of the Earth directly from Earth rocks because Earth’s oldest rocks have been recycled and destroyed by the process of plate tectonics. If there are any of Earth’s primordial rocks left in their original state, they have not yet been found.”
This effectively means a detail that is most fundamental to human history is essentially a best-effort approximation. When I consider that such a basic detail seems arbitrary at best, it’s sincerely astonishing that civilization exists.
But before I fall down that rabbit hole, I will proceed.
During the twentieth century, radiometric dating started getting used to determine the age of really old rocks and stuff (I just read a Wikipedia page all about carbon dating, speaking of rabbit holes — but I’ll summarize that in another post). Prior to carbon dating, there existed several different techniques for estimating the age of earth. A popular method prior to carbon dating was analyzing the strata. In other words, if they could determine the age of one layer, they could then determine the age of the others. Early estimates using this estimate varied substantially, some predicted the earth was about 100,000,000 years old, whereas Isaac Newton estimated it to be 50,000 years old, as he calculated it would take 50,000 years for the earth to cool. However, all these estimates were not congruent with Charles Darwin’s evolution theories. Darwin estimated the Earth to be … no, that’s about to be wrong. Darwin actually estimated the “Last Universal Common Ancestor” lived ~3-5 – 3.8 billion years ago.
Me, I believe time is a loop, and these things are impossible to resolve conclusively.