Category Archives: Astronomy 101

One of my main goals is to try and share a bit of knowledge and understanding about the incredible universe. I have been steadily writing and posting various articles to explain and educate the masses (that’s you, dear reader!) a bit more about some of the science behind the hobby. An urban astronomer might never see most of the things we talk about here, but it’s still good to know about them.

Did Herschell really see life on the Moon?

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Dear Urban Astronomer   I read recently that an important New York publication had reported in detail that the famous astronomer John Herschell had seen life on the Moon, with a powerful new telescope.  Can you tell me more about this?   Curious   Dear Curious.    Sorry to disappoint, but after doing a bit of research, I learned that the “Important New York Publication” you’re referring to was none other than The New York Sun, and the article in … Continue reading →

Will a hammer and a feather fall at the same speed in space?

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  Yes.  Although scientists have been predicting this for centuries, it was finally demonstrated by astronauts in 1971.  David Scott, commander of Apollo 15, took a hammer and a feather out onto the Moon’s surface and dropped them together.  You can watch the attached video to see them landing at the same time.  The only reason feathers fall slowly on Earth is wind resistance.  Feathers are very large for their mass (they have a very low density), so experience a … Continue reading →

What is an asteroid?

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The official definition of an asteroid is ambiguous, and boilds down to asteroids being rocky, dusty objects orbiting the Sun that aren’t planets.  They come in all sizes with the largest (named Ceres) being over 900 kilometers across and the smallest being mere specks of dust.  Some have been found to have small amounts of ice on them, so that nobody’s quite sure whether to call them asteroids or comets, and others cross over into the definition of Minor Planet. … Continue reading →

The Five Planets

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  The ancients had beautifully dark skies, dusted with thousands of stars of varying brightness. At some point, they noticed that five of these stars were quite different from the rest.  Not only were they conspicuously bright, but they also moved against the background of the sky, while all the rest were fixed in place.  These movements weren’t all at the same speed, and varied over time, so these special stars became known as “Planets“, from the greek word for … Continue reading →

How do you measure the brightness of stars?

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A star’s brightness in the sky is referred to as its Magnitude, which is a number with no unit.  In its original ancient form, the magnitude system ranked stars from 1 to 6, with the bigger numbers representing faint stars, so that the faintest star we can see has a magnitude of 6, and a very bright star would have a magnitude of 1.  Since then, a bit of mathematical rigour has been applied to make the system very precise … Continue reading →