Yearly Archives: 2013

Q: How do you prove that the spacetime interval is always the same?

The original question was: Here’s my current dilemma: how does one rigorously prove the invariance of the space-time interval?  In Taylor & Wheeler’s Spacetime Physics, they basically show one very good example of the invariance, then they instruct the reader … Continue reading

Posted in -- By the Physicist, Geometry, Math, Relativity | 19 Comments

Q: Are numbers real?

Physicist: This question usually comes in the form of “are complex numbers real?” or “are negative numbers real?” or something along those lines.  Turns out you can answer all of these questions at once (if you make up a nice … Continue reading

Posted in -- By the Physicist, Math, Philosophical | 11 Comments

Q: If time were reversed would things fall up?

Physicist: Reversing time seems to reverse how things work.  Instead of growing, plants shrink.  Instead of going forward, airplanes fly backward.  And, “intuitively”, instead of falling down, things fall up.  If you have a video of someone jumping into water, … Continue reading

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

Q: Why don’t “cheats” ever work on the uncertainty principle? What’s uncertain in the uncertainty principle?

Physicist: The Uncertainty Principle is often stated as “the position and momentum of a particle cannot be simultaneously and perfectly measured”.  Mathematically, it’s written as , which means that the product of the uncertainties in the position, x, and momentum, … Continue reading

Posted in -- By the Physicist, Physics, Probability, Quantum Theory | 2 Comments

Q: Do the past and future exist? If they do, is the future determined and what does that mean for quantum randomness?

Physicist: This is a difficult question to even ask, because the word “exist” carries with it some “time-based assumptions”.  For example, if you ask “does the Colossus of Rhodes exist?” the correct answer should be “it did, but it doesn’t … Continue reading

Posted in -- By the Physicist, Philosophical, Physics, Quantum Theory, Relativity | 52 Comments

Basic math with infinity

Physicist: Several questions about doing basic math with infinity have been emailed over the years, so here’s a bunch of them!  (More can be added later) Infinity comes in a lot of shapes and flavors.  However, the most straightforward infinity … Continue reading

Posted in -- By the Physicist, Math | 16 Comments