Is it possible to work on physics independently outside academia? The traditional physics career is an academic job at some university, with the eventual goal of becoming a tenured professor. Is it possible for a mostly self-educated outsider working outside academia to come up with significant results in physics? Let's take significant to mean accepted in a high ranking peer review journal with a high citation count. Let's just say due to external life circumstances, the academic path is unfeasible.
Are there any examples of notable physics results coming from outsiders? e.g. a third class patent clerk coming up with light quanta, Brownian motion and relativity.
 A: Eric Betzig did this... kinda. He was a trained physicist who worked in academia, but produced some significant results during a break from professional science. Notice, though, that when Betzig got finished dreaming in isolation, he motivated a team of excellent scientists to help make his dream reality. Very few papers in Science and Nature have an author list of one person.
Even if you don't get a job at a university, consider associating yourself with one, somehow. If you're planning to work for free anyway, you might as well volunteer in someone's lab. In my personal experience, I work much more productively when surrounded by other scientists, especially if they care about my work. It's hard to have truly original thoughts without at least some outside stimulus, and it can be hard to stay motivated without the social reward of 'showing off'.
A: It is certainly possible, given the many who have done so in the past.
Problems however quickly arise in modern physics, and that's the enormous cost of the equipment needed for a lot of fundamental research. The cost of this is beyond the means of most individuals, and even most corporations.
A: I think the opportunities for "amateurs" are quite extensive these days. There is an increasing move towards open-access publishing, which means that in many fields you can keep bang up to date without having to have deep pockets or access to a university library.
In addition, the computing resources that are available (and the open source software movement) mean that with the correctly chosen problem you can make significant contributions to some areas without needing loads of equipment or access to expensive research facilities.
So the message would be - choose your problem wisely.
Just as an example: it would be relatively easy for an amateur to download the entire database of Kepler light curves and make interesting discoveries using software written in python or other open source software designed to analyse light curves to find periodicities, relationships between stellar and planetary properties etc. etc. But what is required is a thorough understanding and knowledge of the literature. It is also of course very useful to have others to discuss and bounce your ideas off. And I think this is where many amateurs fall foul. Working in isolation is difficult. For anybody.
A: Short answer: Yes.
Slightly longer answer: Yes, but you will have to prove your chops.
Discussion: 
This is the physics "career path" of many garden variety crackpots, so you may meet some initial skepticism. Take care to understand and speak the language. Don't overstate your preparation or competence; nor the significance of any particular findings. Be prepared to show that you work is consistent with known physics. Establish some connections with people on more traditional career paths.
Another concern: it may be hard to find a problem that can be given meaningful work without a lot of time devoted to it. They are out there, but you need to know the landscape to find them.
A: Most probably, no. This opinion is based on two considerations.
1)Being unable to join the academic stream means that other work decisions have been taken. Inevitably this leads to inability to focus 16/24 on a physics problem ( I put some time in for sleep). People who have left their mark in the history of physics were very focused on it, and  focusing I would consider  a prime prerequisite.
My no is not a complete one  because in this day and age we have the internet. If the reason one is unable to join academia is something like Hawking would have suffered if his disease caught up early with him, or if one is taking care of a very sick loved one, there is still the internet to learn the latest and discuss the most important, currently. As long as time is not a problme . Which brings me to the second consideration:
2) I had a professor in ancient greek who imparted the following wisdom: Knowledge is a circle. There is a frontier where explorations go on, but the more you know, the larger the radius, the greater the frontier. Unfortunately now there is an enormous body of knowledge continuously expanding and continuously needing new tools. Within academia a sifting takes place through discussions, coffee in the cafeteria, informal lectures, conferences, long before papers for  peer review are ready. Ideas are threshed out and collaborations set up that allow for faster knowledge accumulation. Some of this may start to happen on the internet  and it would need a particular type of personality to be able to survive without the face to face interactions.
Now if he/she has the focus and the time to pursue a physics problem that is not contradictory to known experimental facts and proposes new experiments ( i.e. it is falsifiable) then  I wish them luck. I think the peer review process in physics is not too biased to look at a paper on its merits, but in any case there exist the archive locations where a paper can be put up on the internet and discussed on sites like this . 
A: Gerard 't Hooft certainly thinks so.

What if you are older, and you are not at all looking forward to join those noisy crowds of young students ?
It should be possible, these days, to collect all knowledge you need from the internet. [...] This way, the costs of becoming a theoretical physicist should not exceed much the price of a computer with internet connection, a printer, and lots of paper and pens.

http://www.staff.science.uu.nl/~hooft101/theorist.html

This is a site for ambitious people. I am sure that anyone can do this, if one is gifted with a certain amount of intelligence, interest and determination.

A: Becoming an independent researcher isn't a choice. You either have it in you or you don't. Physics is about passion and relentless pursuit of an ideal, not about position and participation. You don't need permission to think about concepts. but you can't fool the experts with just ideas. You must have a firm grasp of all the math and science that supports your idea. Good luck.
A: NO, it is not.. i tried but i could not get a PHD , to work in physics you need an ADVISOR who can tell you what to work in and give you suggestion, even though you have internet and can ask HERE in physics.stackexchange you will need to know a teacher to publish on journals and to develop new ideas.
A: The question is relative to the state of each field of science.  Mathematics as a  science has a lot of examples.  Physics on the other hand, has gone through many significant changes most which makes it almost impossible to be recognized for a contribution.  Physics is trending and depends on public funding more than every.  In the past, private wealth and business was the funders of science and anybody could contribute because it was ultimately about money.  Theoretical physics has become so far removed for practical application that it is more profitable to search than to discovery.  A discovery is literally the death blow to physics at the fundamental research level.
