Category Archives: Biology

Q: How do we know that everyone has a common anecestor? How do we know that someone alive today will someday be a common ancestor to everyone?

The original question was: From biology and genetics we know that any group of living organisms had a mitochondrial most recent common ancestor (mitochondrial Eve): a female organism who lived in the past such that all organisms in this group … Continue reading

Posted in -- By the Physicist, Biology, Evolution, Probability | 3 Comments

Q: If you were shrunk to microscopic size would you be able to see normally? Would you be able to see microscopic things?

The original question was: In the ‘60s sci-fi classic “Fantastic Voyage,” the crew of a submarine crew are shrunk to microscopic size and injected into the body of an injured scientist.  I realize that this film is rather sloppy from … Continue reading

Posted in -- By the Physicist, Biology, Physics | 10 Comments

Q: If the Sun pulls things directly toward it, then why does everything move in circles around it?

Physicist: Newton’s laws of motion say: Where MP and AP are the mass and acceleration of a planet, MS is the mass of the Sun, R is the distance between them, and G is a universal constant.  What this rather … Continue reading

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

Q: If the number of ancestors you have doubles with each generation going back, you quickly get to a number bigger than the population of Earth. Does that mean we’re all a little inbred?

Physicist: In a word: yes.  But it’s not a problem in large populations. The original questioner pointed out that in the age of Charlemagne (more or less when everybody’s 40-greats grandfolk were living) the world population was between 200 and … Continue reading

Posted in -- By the Physicist, Biology, Evolution, Probability | 12 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 | 5 Comments

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 | 1 Comment