@Alexander, it's always a challenge to solve a problem, be it old or brand new! Scientist essentially likes challenges, and when solution arise we call it pleasure, right! A scientist is a dreamer who is always solution driven!
Old problems in pure science that remain unsolved are always a challenge and involve substantial ingenuity and ability to see from a different viewpoint in order to solve. Of course the developments in analysis and technological methods makes it easier to attempt to solve.
My domain of research is in applied science where research is always in an incremental fashion starting with something that is already partially known and finding ways of improving it incrementally. In engineering new problems are always cropping up because of the developments.
Both kinds of engagements to find solutions can be a challenge. But I´m convinced, that everybody should research in an area, where s/he can be productive and successful.
@Alexander, it's always a challenge to solve a problem, be it old or brand new! Scientist essentially likes challenges, and when solution arise we call it pleasure, right! A scientist is a dreamer who is always solution driven!
I prefer an intermediate route: Starting from the suggested solutions for old problems, I work and present mine better solution. It has worked since now and has given me inspiration to do also 100% new works.
@Alexander: If a problem is already solved there is no need to revisit. But if it can be solved elegantly utilizing new methodologies, it is preferred.
"I don't know, what I'll sing- my song is ripening". A creative process is a combination of different experiences. As a result there will be a new-unexpected- product.
Age of a problem doesn't matter. Mostly you have no real choice. In practice you meet certain problems and in rare cases you smell a trace of a potential general solution, and then the race begins... I think that luck is an important ingredient. But without education you have no chance at all. Character elements like toughness, a thick skin (preferably more then one skin...), and some love for adventures are relevant. If you catch the smell of a trace, you possibly need to follow it over decades, until breakdown or success. Most employee scientists vote for "no experiments" as they have families. So many factors! But education remains possibly as THE invariant & necessary condition number one.
There is greater satisfaction in recognising a novel research topic and then finding a solution. Yet, such an approach is not possible unless you have a good understanding of existing problems. Indeed solutions to "old problems" can often be found en route to a new one when a new class of insight has been gained.