[gardano]

Here's one thing that has bugged me for a while. Why is it said that the great red spot is around 500 years old? How do we know that it hasn't been around for much longer?

Do we have before/after evidence that at one point it didn't exist, and then around 500 years ago it existed?

[Turing_Machine]

In fact we don't even know that it's been there for 500 years. It's only been continuously observed for 187 years.

While there were earlier observations of large spots on Jupiter, it's not 100% certain they were actually the same storm.

https://en.wikipedia.org/wiki/Great_Red_Spot

To extend, a series of disjoint astronomical observations of the Earth would likely show a hurricane/cyclone/typhoon somewhere, but it wouldn't necessarily follow that they were all the same one.

[lordCarbonFiber]

I've always heard the "at least 500 years old" sentiment, because Galileo describes it in his observations.

[Sniffnoy]

Where is that said?