what historical event would like to go back in time and witness?

I want to see that apple hit Sir Isaac Newton on the head.

I would like to have been on the ground (anywhere but in Japan) the day the atomic bombing of Hiroshima was reported. A weapon that destroys whole cities. And only USA has it.

I'd love to go back to when the band KISS was first gathered together so I can talk them out of forming the band.

What was it like to be inside the twin towers on 9/11 or what was it like being inside the hijacked planes as a passenger. Specifically, what it was like to be on the top floors of the towers above the plane impact.

I have morbid curiosity about death and stuff like that. Plus, I just watched a documentary on 9/11.

When my grandfather (my father's father), was a young child or young adult, in our home village. Just to witness how he lived his life, while a single man or married would be very insightful.

Per your question includes "witness"; it would be difficult for me not to try and interact; though I understand if I did it my unravel the entire universe.

i'd like to go to that public meeting where thomas huxley supposedly said he'd rather be descended from an ape than a bishop or something like that. i doubt the actual event would be as great as the legend, but i'd still like to see it.

wright brothers' first flight, maybe?

I like true crime, so I'd say the day Lizzie Borden, killed or didn't kill her parents.

I recently listened to Spies on Audible...Here's someone very interesting, Chevalier d'Éon.

https://en.wikipedia.org/wiki/Chevalier_d%27%C3%89on