I would go back in time and meet the people who wrote the first ever USB standard. Then I would convince them that all USB connectors have to be reversible from day one so that nobody will ever need to struggle with the 20/80 odds of getting it right on the first try. Come on, it’s two possibilities and the probability of the wrong one is at least 80%. What’s the deal with a connector like that?
Go back to 1911 and convince Taft to concede the Republican nomination to Roosevelt. That allows Roosevelt to stomp Wilson, get the US into the war before Russia left, and get the war over with years earlier.
This prevents both Stalin and Hitler from rising to power, and prevents most of the European theater of WW2, as well as a host of other knock-on effects.
I'd like to say something noble like warn Amelia Earhart, or hookup Adolph with some Bob Ross videos. But if I'm being honest, I would probably be selfish. I would tell past me to not fuck up quite a few things that past me royally fucked up.
Warn about how plastic (especially single-use) is a major pollutant, with microplastics managing to get into our organs with long term consequences we are yet to grasp.
It did push our technology and way of living forward, but at what cost?
I'd go back and write a book with just enough truths to cement myself as a soothsayer. I'd then warn of wars, eco disasters, pandemics, natural disasters. Then I'd invest some money in some good places and make sure it made it to my kids after I'm gone.
I'd find the first motherfucker that started smoking stuff, whether it was first tobacco or whatever, and get rid of him/her before anyone else ever learned of the practice/habit.
Would have been better health for countless people afterwards, if simply nobody ever knew..
I would try to save the roman republic and prevent the roman kindgom. It would also be interesting to see what would have happend if they never switched to christianity.
I prefer to rewind time with me along, be young again, that kind of time travel. Of course with my knowledge and memories of up to before my "time travel", be retained. I could only remember what I could any way. The future would surely not happen exactly as the same before. Live a new younger life, a seemingly fresh restart at an early point in my life.
I'd invent the printing press during the classical era and watch what happens from there. I guess the folks at Carthage would also enjoy knowing about paper making, better wind-powered sails for ships and to be on the lookout for those "Romanes"
Changes could have so many repercussions even well meaning actions could make things worse. The safer bet would be to collect lost books and art.
That said, stopping the Lincoln assassination is tempting. I'd hope to change reconstruction to better wipe out the confederacy, prevent lost cause doctrine, and better integrate former slaves into full citizenship and society.
Bring back Sodium batteries and how to make them as well as solar panel production. Probably to Nikola Tesla.
To be a bit more precise whatever the easiest to produce versions of each are not the best ones so they could actually be produced at the tech level at the time.
I'm sure they would still end up creating equivalents of oil Barons etc. but at least it would be based on a cleaner tech and more able to improve from there.
As I wouldn't like to change something and go fully dystopian when I return to present, I just go back and buy 1 million bitcoins, then return to present and influence present things just using big amounts of money.
Well, I don't think anyone is really sure just how exactly time travel can mess with stuff. I would probably take a page from some time travel movie I saw. I would want to avoid any sort of temporal paradox and avoid too many changes.
So, I would probably remove myself from the equation as much as possible. Go to a hotel or somewhere where I can avoid accidentally running into anyone I might know. Leave all electronics behind, but take a book or something. Spend the whole day avoiding TV/News/People and just reading or work on perfecting a skill. At the end of the day I would call up a broker from the hotel room and find out which stock had the greatest percentage gain that day. Just enough information for one good trade.
Then I would go back to that morning, buy up a ton of that stock, live out life normally, then sell the stock at the end of the day.
I would install an automated missile system on every single would be colonizer country's waters, that would sink their ships when they tried to leave port