Ooh! Got another one…the OP says I’m arriving in my pajamas, right? Well, the shirt I’m wearing now is typical of what I might wear to bed. It’s a very well-worn old T-shirt that happens to be a 50% polyester blend. It’s made in the USA, but the next shirt in my laundry basket is only 10% polyester, but was made in El Salvador, apparently. 
I’ve seen them all, and man, they’re all the same.
-P. Simon
Seriously, I like this one.
Back when I was working towards my doctorate, and for several years afterwards, I had proofs in my head of a good number of mathematical theorems that hadn’t yet been proven in 1950. That wouldn’t prove I was from the future; they’d just think I was some sort of super-genius. But if I kept on jokingly giving the explanation that I was really from the future until ‘I’ was born a few years later, and then said, no seriously, I am from the future, this is how I know this stuff, and there’s a kid at a certain house on Woodrow Wilson Drive in Los Angeles whose fingerprints are the same as mine…
Of course, unlike with panache45 who had already been born by 1950, that wouldn’t work for me: in the ‘new’ post-1950 timeline, even if my parents had a boy child at about the right time, he wouldn’t be me, wouldn’t have the same fingerprints, etc.
I’d still spend some time writing down the lyrics to every Elvis Presley song I could remember, and quietly copyright them. Elvis might or might not become a phenom in this new timeline, but if he did, he might just wind up having some hit songs that were more or less like the ones he’d made famous in our timeline. It would be an interesting test of robustness of events.
Tough question! I’d probably spend my days in a booby hatch.
I went to grad school with a woman who had returned to grad school after stopping out for years to raise her family. She said the biggest change in physics was that what was called Electro-Quantum Dynamics in the 1960s was called Quantum Electro Dynamics in the 1980s, giving a much cooler acronym QED. There may not be enough differences between my 2000s recollections of physics and technology and the reality of 1950 to get noticed.
There might be some physics stuff I remember that the 1950 folks would believe, or confirm experimentally. My best bet might be building a scanning tunneling microscope. I’ve never done it before, but the concept would not be totally foreign (QM was well established before 1950, and off the top of my head field emission microscopy had been invented by them). As I recall the development of the STM was easier than Binning and Rohrer had anticipated. Could 1950s electronics make an STM? I don’t know.
Maybe I could tell someone that “deathane” (the contaminant that made early semiconductors unusable) was gold. The transistor was invented in 1957 as I recall, so there was plenty of semiconductor research at the time.
Maybe I could meet George Gamow and suggest that Big Bang cosmology implies the universe is full of black-body radiation. If we got drunk together he might believe me.
Naw - I’d probably be stuck in an ansylum for the rest of my days. 
Hans Bethe being the atom spy …
WHAT?
Dr. Bethe was never anyone’s spy.
Do you have a cite?
In looking at the responses so far this is actually an excellent challenge. Even if you could convince them with sports predictions etc., it’s interesting just how narrow and limited most people’s knowledge base is regarding anything hard and practical you could tell them about in enough detail that it would allow them to build anything based on your knowledge.
It’s easy to forget how amazingly complex modern technology is re the stuff we take for granted.
All I’d have to do is find an Icelandic geologist and convince him to run magnetometer readings either side the Mid-Atlantic Ridge. We’ll co-publish, and pre-empt the Morley-Vine-Matthews hypothesis by 13 years.
I’d arrange it so my parents never meet. People will believe me when I fade into oblivion.
Except that you can’t knowingly make a paradox because should you do so the time police show up and stop you.
Proving to them you have no gallbladder could be nasty.
X–rays could only do so much back then.:eek:
I’d try to get John Campbell to quit smoking, doubt it would work, but,
it would be worth a shot.
Couldn’t you just point out peptic ulcers can usually be treated with anti-biotics? I mean they could then check that fact out fairly easily and find out it was true.
A dental examination, perhaps? I was always cavity-prone despite brushing regularly and not eating sweets that often, but would some of my fillings, and a cap I have, be made of materials or composites that were unknown in the era?
I’m an urban planer. There was a LOT of bad planning in the 1950s; massive housing projects, urban renewal, advocacy for urban expressways, zoning that encouraged visual pollution, and the like. Some projects, like Pruitt-Igoe in St. Louis, became failures shortly after they were built. Maybe being a vocal rebel against what was considered prevailing good planning practice in the day, and accurately describing the what would result from the projects civic leaders supported, would demonstrate I was from 2010.
Industrial design? The design of furniture, appliances, electronics, and so on from the 1980s is fairly simple to replicate, and the look is much different than what designers from the 1950s thought future design would appear like. Same thing with graphic design.
EDIT: looks like dental work was already taken.
This is worrth repeating: again, without the impossible for 1950 tech or procedures, how do you convince someone? Most responses depend upon something in their body or something performed in 2009.
Well, my parents were still in diapers themselves in 1950, so in my mind I’m pushing the present and past dates ahead a couple decades, but I think you’ve got it with starting with the parents. Assuming little me is around, removing my shirt to show the exact same spots of skin discoloration (I have neurofibromatosis) would be pretty much undeniable.
I would think that most folk have some combinaiton of birthmarks, scars and such things that are unique enough, that would at least get them to start listening to anything else I’d have to say, which is when I would start in with the predictions about world events and tech developments.
whew.
I’m thinking maybe a very knowledgeable archaeologist could do it.
If you know exactly where people would have to dig, and you could give a pretty accurate description of what they would find, that’d be damn hard to explain a way.
A lot of this stuff people have suggested might be waved off as “a genius who speculated correctly” or it goes against the “prediction” rules laid out by the OP. But archaeological digs would be very hard to dismiss.
Especially once you’ve shown not once but many many different digs all over the world, in places where the artifacts are way too well covered and in which there is no way you could have “planted” such an elaborate dig.
How else would you know this stuff other than being from the future?
You could also give the exact coordinates of famous shipwrecks that were totally unknown in 1950. There’s no way they could really dismiss that.
Even the argument of “well, you discovered it independently then acted like you just know about it because you’re from the future” wouldn’t hold water; a major operation such as what would be required to actually dive deep enough to see some of the major wrecks that have been discovered in the past 20 years (especially of old Spanish era stuff that had mostly been forgotten to history) couldn’t have been put together in total secret with no other living persons able to pipe in “hey, I helped that guy find that, he’s just fooling you if you think he’s from the future…”