astronomy

Dot Physics

Category archives for astronomy

When is noon?

I was at the zoo this weekend, it was fun but hot. Somewhere near the middle, there was a sun dial. The cool thing (well, I think sun dials are cool anyway) was that the shadow was pointing about to the “12″. I looked at my watch and it said 1:05 PM. What is up…

I am going to try to answer another Ask a ScienceBlogger question. This one is from George P. Burdell. He asks: “If the universe is expanding from the big bang, has anyone tried to reverse plot the galaxies to figure out the exact point where the big bang occurred?” Actually, he asked two questions, but…

Debris field for a broken meteor

I happened to catch two parts of two different episodes of Meteorite Men – a show about two guys that look for meteorites. In both of the snippets I saw, they were talking about a debris field for a meteor that breaks up. In these fields, the larger chunks of the meteorite are further down…

xkcd and Gravity Wells

Wow. In xkcd 681 comic, there is an impressive illustration of the common term “gravity well”. Here is a small part of that large image: I can’t resist. I must talk about this awesome illustration. My goal for this post is to help someone understand that comic (although the comic itself does a pretty good…

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…

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).…

Scale Model of the Solar System

The solar system is difficult to show correctly. Why? It is difficult because the size of things are vastly different. Let me use units common in solar-system astronomy, the Astronomical Unit (or AU). One AU is the distance from the Sun to the Earth. If I want to look at all the planets, I would…

A small version of the seasons

So, it snowed here (in Louisiana). Sure, it wasn’t a lot, but it was still a big deal. The following day, there was still some snow on the house roofs. I took some pictures. Here is a shot looking at the North side of a house. And here is a view of the South side…

Parallax, what is it good for?

Very simply, parallax is an apparent motion of an object due to a change in observation position. Let me start with an example. Here are two photos. I took a picture of the cabinet in the background from two slightly different positions. In the foreground is a clone trooper that did not actually move. I…

Seasons, short and simple

I love this question: Why is it warmer in the summer than in the winter (for the Northern hemisphere)? Go ahead and ask your friends. I suppose they will give one of the following likely answers: The tilt of the Earth The tilt of the Earth makes us closer to the Sun We are closer…