The development of the atomic model

I love this story. It is a story of how ideas changed about the nature of the atom. These are the notes (and diagrams) I use when I teach the atomic nature of matter to non-science majors. The best thing about this story is that it is a great example of science. Science (or scientists)…

Tides. Why are they so hard?

Every introductory astronomy text and most intro physics texts talk about tides. The usual explanation is something along the lines of: The moon exerts a gravitational force on the Earth and all the stuff on the Earth. This force decreases with distance (1/r2). Thus the moon pulls greater on one side of the Earth than…

Pluto. Planet, or not?

Still moving stuff over from my last server. Here is one that keeps coming up. Surprisingly, I STILL get comments and questions from students and teachers about Pluto. Questions such as: “Why do scientists hate Pluto?” “How did they discover that Pluto was not a planet” “What will happen to our planet songs without Pluto?”…

Error propagation and the distance to the sun

Some time ago, I wrote about the awesome things the Greeks did in astronomy. Basically they calculated the size of the Earth, distance and size of the moon and distance and size of the sun. The value obtained for the distance to the sun was a bit off, but still a bang up job if…

Buzz Out Loud and Black Holes

Buzz Out Loud is one of my favorite tech podcasts. Unfortunately, I am a little behind in the episodes. However, in the episode 900 there was an email from a listener regarding LHC and black holes. The emailer claims that a massive black hole would mess up Earth’s orbit. This is not quite true. I…

When is the Sun directly overhead?

Question: When is the Sun directly overhead? (assume you are in the United States of America) Common Answers: Everyday at noon. On the summer solstice (June 21ish) Answer: For continental U.S. the answer is never. Since the Earth’s rotation axis is tilted 23.5 degrees with respect to its orbital motion around the Sun, one would…

Cool things the Greeks did in astronomy

One of things I like to think about in science is “how do we know that?” It is interesting how one thing builds on another. This is a story of how the Greeks estimated the distance from the Earth to the Sun (an important idea in the development of the model of the solar system).…

Status of Pluto – Zombie Feynman Replies

I can’t believe there is still all this talk about what to call Pluto. Can’t we just move on? In an effort to help, I have summoned the Zombie Feynman to get his words on the subject. This is what he said: