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Astrophysics is a great area of physics. It represents, both in the scale of the phenomenon of interest and the conceptual basis of the required physics, the opposite pole of knowledge from the fundamental physics of quantum field theory. For an astrophysicist, the Earth is "microscopic," the physics is the physics of complexity, the complexity that dominates the physical world in which we live, and the astrophysicist must be highly educated in a vast range of topics, almost all of which are incompletely understood. For a field theorist, a single atom is huge, the physics is the physics of ultimate simplicity, and the physicist must be educated in a vast range of highly mathematical topics, many of which are incompletely understood. In both areas, physicists have divided the labor between observational scientists who build and use vast instruments of daunting complexity to probe regions of space-time far removed from the every-day world, and theoreticians who struggle to bring order to the data these instruments yield and to understand the mind-bending, mathematically-intense conceptual frameworks necessary to support that order. For a look at the observational side you might look at two cutting edge instruments described at these websites:http://www.almaobservatory.org/http://home.web.cern.ch/about/accelerat ... n-collider
It’s harder to point you at comprehensible information on the theoretical side. For quantum field theory I would recommend a little, easily accessible book; it’s out of date in a sense, but the basics have not changed: “QED: The Strange Theory of Light and Matter” by Richard P. Feynman. Quantum Electro-Dynamics (QED) is the foundation upon which most quantum field theories are built. Feynman, one of the inventors of QED, manages, somehow, miraculously, to make this mathematically-difficult subject readily accessible to pretty much anyone with a high-school education and the will to learn. To get a real knowledge of astrophysics, stripped to its essentials and presented at a level suitable for (a smart) college undergraduate, try: “The Physical Universe: An Introduction to Astronomy,” Frank H. Shu. Even though it is WAY out of date (astrophysics changes rapidly, and this book is 30 years old), you will not find a better introduction to astrophysics for serious students of science at the undergraduate level (pre-calculus). You should be able to find these books in a library, but because of their technical nature be sure to check the extended, interlibrary loan catalogs; if you live in California this service is called LINK+, ask a reference librarian for a suitable service available to you. Worst case: you can buy them used; since they are old but not antiques, they will be cheap; see:http://www.abebooks.com/servlet/SearchR ... 503&tn=qedhttp://www.abebooks.com/servlet/SearchR ... l+Universe
So that covers the basics. For science fair topics you could take a look at our topic selection “wizard” that can be reached from our top-level web page: http://www.sciencebuddies.org/
Hope this helps. When you have a few ideas, feel free to come back, an we’ll see what we can come up with.