If you had ever asked the question "Why?" or "How?" when you encountered something that puzzled you, you had entered the realm of Physics. Simply put, Physics is the study of nature. Physicists seek to uncover the most basic laws that govern the behavior of nature. It is thus the most fundamental of all the sciences. All phenomena in the basic sciences (astronomy, biology, chemistry, and geology) and the applied sciences can be related back to these underlying principles of Physics. Advances in Physics are responsible for much of the modern conveniences we enjoy everyday and have taken us from the horse and buggy to the space shuttle, from the mud hut to the skyscraper, from the candle to the laser, from the carrier pigeon to live satellite transmission, from cave drawings to digital holography, from clay tablets to the world-wide-web, and from the abacus to the super-computer.

Also, Physics attempts to answer some of the most intriguing questions that have challenged mankind - what is the universe and why is it so? At their most fundamental, these questions satisfy our natural curiosity and define who we are. The pursuit of these questions has led to a whole new outlook of our role in the universe. The knowledge gleaned allows us to do away with superstitions and harness nature to our advantage. Even with all these successes, there are still many more discoveries awaiting us. Basic research in Physics continues to push the envelop of our understanding of nature and subsequent applications will continue to better our quality of life.

All Physics majors share a common set of core knowledge. They include mechanics, electricity and magnetism, quantum Physics, and thermal and statistical Physics. The sub-fields of Physics arise when this core knowledge is applied to different disciplines. The following are an alphabetical listing of the major sub-fields of Physics.

Acoustical Physics: The study of sound and how it is transmitted. It is one of the oldest branches of Physics with an active area of research that has many important applications. Examples include the compact disc recording method, concert hall designs, hearing aids, and the medical ultra-sonic scanner. Studies of shock waves, vibration, noise, and underwater sound are all important areas of applications of acoustics.

AstroPhysics: The study of the universe. Astrophysicists are interested in the origin of the universe, its age, how long will it last and how will it end. Models for the formation, maturation and death of stars are examined. Detection and formation of extra-solar planets and possibility of extraterrestrial life are studied. Also, the study of our sun including sunspots and the solar cycle, and how they influence the earth, are active areas of research.

Atomic and molecular Physics: The study of what atoms are and how they interact to make molecules. Due to their relative simplicity, work in this area is used to probe the fundamentals of quantum mechanics. It provides the basis for understanding chemical reactions and is a test-bed of much of quantum computing. Spectroscopic data is used to learn how Renaissance artists mixed their paints, to detect dangerous chemicals or pollutants, and in diagnostic medical tests.

BioPhysics: The study of Physics applied to biological system. A quantitative understanding of this complex system is sought from the fundamental laws of Physics. They include physical mechanisms of seeing and hearing, how the brain works, how nerve impulses travel, the effects of X-rays and nuclear particles on cells and tissue, the composition and structure of proteins or DNA, non-invasive or non-destructive diagnostics, cellular structure, micelles, etc.

Condensed matter Physics: The study of the properties of materials. This is the widest sub-field of Physics and perhaps, has the most direct impact on our life. Properties studied include the structural, optical, magnetic and electronic properties of metals, alloys, semiconductors and liquids. The ubiquitous integrated circuit is perhaps the most useful outcome. Advances in this sub-field brought about lasers, the semi-conductor industry, light weight space-age composite materials, the scanning-tunneling and atomic-force microscopy, carbon nanotubes, etc.

Education Physics: The study of how students learn Physics concepts. New pedagogy that deviates from the traditional lecture mode is tested and introduced to learn how to best teach Physics. Includes the use of multi-media, peer instruction, and visualization modules in instruction.

Elementary-particle Physics: The study of Nature's most fundamental building blocks. What are the nuclear particles - the protons and neutrons made of? How do these particles interact? What is the electron? What are the fundamental forces of Nature? Research in particle Physics strives to unravel these questions and the picture formed is that all particles are either leptons or baryons. Elementary-particle physicists strive to understand the members of these families and how they interact with each other.

Fluid and plasma Physics: The study of the flow of fluids. Fluids are gases or liquids and if they are electrically charged, we refer to them as plasmas. The streamlining of cars, boats and planes, designs of jet engines, fuel systems, and inkjet printers, lubrication, and oil flow are some examples of the Physics of fluids. Plasma Physics has applications ranging from the re-entry of space vehicles, space plasmas, our sun, the ionosphere, and controlled fusion for power production.

GeoPhysics, atmospheric Physics and physical oceanography: The study of the Physics of the earth. This ranges from the upper atmosphere down to the earth's core and includes long-range weather prediction, exploring for minerals and oil, ocean currents, greenhouse effect, plate tectonics, geomagnetism, volcanic activities, and earthquake prediction.

History of Physics: The study of the development of fundamental ideas in Physics from a historical perspective. Offers valuable insights into the leading figures in Physics, influences that shaped their thinking, and interconnections between ideas and people.

Nuclear Physics: The study of the atomic nucleus. The structure and stability of nuclei are probed by using high-energy accelerators where heavy nuclei are made to collide. Models are used to understand how the constituents interact. Applications of Nuclear Physics include nuclear power and the use of radioactive material for dating and for medical treatment.

Optical Physics: The study and use of light. The generation and control of light in the design of lens systems for observations and detection, applications of lasers ranging from eye surgery to cutting tools, efficient ways to use solar energy, and image processing are some of the concerns of this sub-field.

Space Physics: The study of the regions from the upper atmosphere to the near-vacuum of outer space. Applications include planetary exploration, and communication and weather satellites.