Obviously there are loads from history but I was thinking about the past 20 years or so.
Depends with what you mean with "amateur".
For example, Einstein was an amateur because he did not get paid to do science. He did have a PhD and obviously wasn't a layman. But he wasn't a professional scientist, because his job was in a patent office.
Some other "amateurs" would include Fermat and Descartes, who were lawyers and not professional scientists. But again: these people were very knowledgeable about the field they contributed to!
But these are examples of more than 100 years ago. I honestly don't know any examples from the last 20 years. I think science has advanced so much that it is really hard for non-professionals to have meaningful contributions. That is: to make a contribution, you need to work day and night. It's very hard to do if you already have another job.
Furthermore, to make a contribution now requires a lot more knowledge than 100 years ago.
Here's one from 2010.
Wow, what a beautiful story!!
One heard this past weekend.
A custom officer
This story is a load of rubbish (not you Astro! The story). There are hundreds upon hundreds of varied, blue sky and downright bizzare cancer treatments under research. Sound is an old and simple idea, just look up therapeutic ultrasound for tumour treatment. The fact that this story is being peddled as a cure in combination with some magic eureka moment that cancer researchers are too involved to see pretty much tells me anything I need to know.
I would throw out Julian Barbour. Phd, no academic position. A long, long, amount of thinking on his own. Now commands respect, and gets his theory papers published in major peer reviewed journals. So far as I know, still no professional position.
http://www.bbc.co.uk/radio4/features/sywtbas/ (though I guess most PF members would not qualify to enter for it).
Astronomy is still a field where amateurs make regular contributions. There's just too much sky for the professionals to watch all of it all the time. Often the first indication that "something interesting just happened" comes form amateurs, followed by a scramble among the professionals to get telescope time to observe it in more detail.
Discovering long-period comets used to be an amateur "speciality", since the basic method is just "keep looking till you see something that isn't on the star charts", but some of the space telescopes are now "hoovering up" comets as a by-product of what they were designed to observe, and of course they aren't limited by the earth's atmosphere.
Signing your organ donor card?
how about http://en.wikipedia.org/wiki/John_R._Hendricks" [Broken]
Uh, what about those Japanese soldiers in WW2? They cut up some Chinese bodies and did some research on that...sounds horrible, but I guess they did learn a thing or two from that.
Computing science is an example for that, since effectively most people are amateurs since the field, or rather, education didn't exist twenty or thirty years ago. So, especially in software engineering, you find people from physics, EE, math, chemistry and even sociology.
I doubt that going into CS without a CS, or math, degree makes a lot of sense these days though. I went to university twenty years ago, it was professional, but most teachers weren't all-rounders in the field as their students are now, and I expect some of them have a hard time keeping up these days.
That's a fantastic story and a really neat thing to lean about bees.
I've been doing some "amateur" behavioral studies myself. I only have preliminary findings, but it seems that you cannot condition your girlfriend to enjoy video games even if you associate the sound of dragon-swooping and swords-on-shields with chocolaty treats. She will still just associate the chocolaty treats with chocolaty treats.
Several years ago amateurs were largely esponsible for cataloging a lot the near earth asteroids, but I'm not sure if that's still being done that way or if it's largely governmental organizations now.
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