Category Archives: Physics

Q: Why are many galaxies, our solar system, and Saturn’s rings all flat?

Physicist: This may be the shortest answer yet: “accretion“. Accretion is the process of matter gravitationally collapsing from a cloud of dust or gas or (usually) both.  Before thinking about what a big cloud of gas does when it runs … Continue reading

Posted in -- By the Physicist, Astronomy, Physics | 4 Comments

Q: What does “E=mc2” mean?

Physicist: This famous equation is a little more subtle than it appears.  It does provide a relationship between energy and matter, but importantly it does not say that they’re equivalent. First, it’s worth considering what energy actually is.  Rather than … Continue reading

Posted in -- By the Physicist, Equations, Philosophical, Physics, Relativity | 8 Comments

Q: How can the universe expand faster than the speed of light?

Physicist: You’ll often hear that “the universe is expanding faster than the speed of light”.  However, this statement is akin to statements like “green is bigger than happy”.  It’s not even wrong. There are two big things to remember about … Continue reading

Posted in -- By the Physicist, Astronomy, Physics, Relativity | 16 Comments

Q: How fast are we moving through space? Has anyone calculated it?

The original question was: Considering the spin of the earth, it’s orbit around the sun, the sun’s orbit around the Milky Way and the Milky Way’s journey through interstellar space, has anyone calculated our speed though the universe? Physicist: The … Continue reading

Posted in -- By the Physicist, Astronomy, Physics | 13 Comments

Q: What is radioactivity and why is it sometimes dangerous?

Physicist: Here’s every particle you’ve ever interacted with: protons, neutrons, electrons, and photons*.  Dangerous radiation is nothing more mysterious than one of those particles moving crazy fast. The nucleus of some kinds of atoms are unstable and will, given enough … Continue reading

Posted in -- By the Physicist, Biology, Particle Physics, Physics | 1 Comment

Q: Why does carbon dating detect when things were alive? How are the atoms in living things any different from the atoms in dead things?

Physicist: As far as carbon dating is concerned, the difference between living things and dead things is that living things eat and breathe and dead things are busy with other stuff, like sitting perfectly still.  Eating and breathing is how … Continue reading

Posted in -- By the Physicist, Biology, Particle Physics, Physics | Leave a comment