Lecture4: relationship between physics and

other fields of sciences

Physics is at the crown of science • Physics method is very useful, now used in many

different areas• Physics laws are very useful, universal.• Other areas of studies have also helped advances in

physics.• Physics is at the crown of science.

Physics is closed related to other fields• Math• Chemistry• Biology• Engineering• Financial market• Social science• Archeology• ….

Physics and Math

• Physics is science but math is not• Math starts with definitions and axioms and derive

consequences, no observation is need, no falsification needed.• Math in some sense is a logical system. • However, it is amazing to see that math is a useful

language for physics.

Why it is so amazing?

• How can the moving trajectory of an object can be described by a math equation or curve? • Almost all laws of physics can be written down as

math equations: differential equations• Thus exploring the consequence is solving the

equations.• The equations have certain beauty, like F=ma,

Maxwell equation, Schrodinger equation, Dirac equation, Einstein equation…

Relationship

• New math is discovered in physics, but math is also useful for physics discoveries.• Math is useful for smart thinking: an important part

of physics• Math is an indispensive tool.• We still don’t have enough math to understand

some deep physics• However, physics is not math. Many traditional

teaching of physics turning into math exercise!

Computer Science

• Software, hardware, applications• Hardware, closely related to physics• Software: algorithms, applied math, logical analysis, information science• Applications: Can be used to do math and physics• Simulations, great ways to solve complicated

differential equations.• Physics: theory, experiment and computer

simulations (cannot do experiment)

Chemistry

• Old chemistry deals with classification of stuff and reactions among them. • At a deep level, chemistry is related to interaction

between atoms and molecules.• These interactions are quantum mechanical in

certain cases. • Therefore we have quantum chemistry.• Rutherford received Nobel prize in Chemistry.

Biology

• Many biologists had physics background. • Many physics methods have been used for biology

(structure study, dynamics) protein folding! • Now many physics dept also study biology, they are

called bio-physicists. Umschneider, David Cai

Energy conservation and biologyJulius R. von Mayer (1814) was a German physician and physicist and one of the founders of thermodynamics. He is best known for enunciating in 1841 one of the original statements of the conservation of energy "energy can be neither created nor destroyed". In 1842, Mayer described the vital chemical process now referred to as oxidation as the primary source of energy for any living creature. He also proposed that plants convert light into chemical energy.

How nerve works?

Cell and enzyme

• Many elaborated chemical reactions, a whole series of molecules change from one to another in a sequence or cycle of rather small steps.• It requires something called enzyme in cell, which

helps the reactions, letting atoms to go from one place to another.• Krebs cycleChanges GDP to GTP

Protein and amino acids

• All proteins are not enzymes and all enzymes are proteins.• Proteins are series of amino acids (twenty or so)• DNA, a substance in the nucleus of a cell. • DNA contains the blueprint, how to make enzyme.

Astronomy

• Astronomy is as old as physics if not older.• Physics laws were discovered through astronomy.• Optics and astronomy has a close relationship. Galielo invented the telescope. • Modern astronomy is closed related to physics, it is called astrophysics. Start burning: nuclear physics, Creation of different nuclei, Supernova explosion, neutron stars, black hole

Social sciences

• Social science is an academic discipline concerned with society and the relationships among individuals within a society. It includes anthropology, economics, political science, psychology and sociology. In a wider sense, it may often include some fields in the humanities such as archaeology, history, law, and linguistics. The term may however be used in the specific context of referring to the original science of society, established in the 19th century, sociology. Émile Durkheim, Karl Marx and Max Weber are typically cited as the principal architects of modern social science by this definition.

methods

• Positivist social scientists use methods resembling those of the natural sciences as tools for understanding society, and so define science in its stricter modern sense. Interpretivist social scientists, by contrast, may use social critique or symbolic interpretation rather than constructing empirically falsifiable theories, and thus treat science in its broader sense. In modern academic practice, researchers are often eclectic, using multiple methodologies (for instance, by combining the quantitative and qualitative techniques). The term social research has also acquired a degree of autonomy as practitioners from various disciplines share in its aims and methods.

Financial market

• Many physics Ph.D.s went to financial market• I have two Ph.D.s at Goodman-Sachs• Why financial market interested in theoretical

physicists? • Modeling. Differential equations. Laws of Finances.• Try to find simple rules to make money!• However, it is difficult to find a universal rule. There

are many rules. • Financial engineering.