Category Archives: — By the Physicist

Q: When you write a fraction with a prime denominator in decimal form it repeats every p-1 digits. Why?

The original question was: How come the length of the repetend for some fractions (e.g. having a prime number p as a denominator) is equal to p-1? Physicist: The question is about the fact that if you type a fraction … Continue reading

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

Pluto!

Physicist: In 2006 a probe called New Horizons was launched to get a better look at Pluto and its moons Charon, Nix, and Hydra.  Since then, Pluto stopped being a planet and gained a couple more moons: Kerberos and Styx. This … Continue reading

Posted in -- By the Physicist | 7 Comments

Q: If atoms are 99.99% space, what “kind” of space is it? Is it empty vacuum?

Physicist: This is a bit of a misnomer. When we picture an atom we usually picture the “Bohr model”: a nucleus made of a bunch of particles packed together (protons and neutrons) with other particles zipping around it (electrons).  In … Continue reading

Posted in -- By the Physicist, Physics, Quantum Theory | 9 Comments

Q: Is geocentrism really so wrong? Is the Sun being at the “center” (i.e. the Earth orbiting the Sun) just an arbitrary reference frame decision, and no more true than the Earth being at the center?

Physicist: When you walk around in this big crazy world, there aren’t any immediate reasons to suspect that the ground under your feet is doing anything more than sitting perfectly still (ring of fire notwithstanding).  Given that, when you look … Continue reading

Posted in -- By the Physicist, Astronomy, Experiments, Physics, Relativity | 7 Comments

Q: Is there such a thing as half a derivative?

The original question was: Another one of those questions of the type “does this make sense”.  You have first derivatives and second derivatives.  f'(x), f”(x) or sometimes dy/dx and d^2y/dx^2. Is there any sensible definition of a something like a “half” … Continue reading

Posted in -- By the Physicist, Conventions, Equations, Math | 13 Comments

Q: Why is our Moon drifting away while Mars’ moons are falling?

The original question was: I know the Moon is getting further away because tides/friction/conservation of angular momentum.  This video claims Phobos is getting closer to Mars because of tidal forces, what gives?  Obviously no oceans to drag around but what … Continue reading

Posted in -- By the Physicist, Astronomy, Physics | 11 Comments