Category Archives: Math

Q: Why are determinants defined the weird way they are?

Physicist: This is a question that comes up a lot when you’re first studying linear algebra.  The determinant has a lot of tremendously useful properties, but it’s a weird operation.  You start with a matrix, take one number from every … Continue reading

Posted in -- By the Physicist, Math | 18 Comments

Q: Are white holes real?

Physicist: The Big Bang is sometimes described as being a white hole.  But if you think of a  white hole as something that’s the opposite of a black hole, then no: white holes aren’t real. They show up when you … Continue reading

Posted in -- By the Physicist, Astronomy, Math, Physics | 21 Comments

Q: Why is Schrodinger’s cat both dead and alive? Is this not a paradox?

One of the original questions was: A basic rule of logic is that something cannot contradict itself. It is impossible for P to be true and not true. Doesn’t Schrödinger’s cat violate this law and therefore invalidate logic? Physicist: The … Continue reading

Posted in -- By the Physicist, Logic, Physics, Quantum Theory | 48 Comments

Q: Why doesn’t life and evolution violate the second law of thermodynamics? Don’t living things reverse entropy?

Physicist: In very short: nope. The second law of thermodynamics is sometimes (too succinctly) stated as “disorder increases over time”.  That statement seems to hold true, what with mountains wearing down, machines breaking, and the inevitable, crushing march of time.  … Continue reading

Posted in -- By the Physicist, Biology, Entropy/Information, Evolution | 90 Comments

Learning intro number theory

Physicist: We occasionally get questions about free learning resources.  Khan academy is excellent, and if you poke around you can find a smattering of free class notes and text books, but generally speaking the more more detailed/advanced the material, the … Continue reading

Posted in -- By the Physicist, Brain Teaser, Math, Number Theory | 5 Comments

Q: Is it a coincidence that a circles circumference is the derivative of its area, as well as the volume of a sphere being the antiderivative of its surface area? What is the explanation for this?

Physicist: For those of you not hip to the calculus groove, here’s what’s going down:  The derivative of Y with respect to X, written , is just a description of how fast Y changes when X changes.  It so happens … Continue reading

Posted in -- By the Physicist, Math | 14 Comments