Category Archives: Questions and Answers

Most people have many questions about astronomy, and aren’t happy with the standard answers. Here are some articles trying to change this. If you have any questions you would like to see answered, ask me in an email to the address below, and I will answer your question in an article on this list

How old is the Earth?

Urban Astronomer avatarPosted on by

The Earth is about 4.5 billion years old.  This age is deduced by radiometric dating (Carbon-14 dating is one form of radiometric dating, suitable for archaeogical timespans.  Other isotopes are needed to measure really long periods of time) — the oldest rocks anybody has found on Earth are about four and a half billion years old.  Extreme ages of the planet are backed up by the times required for geological features to form, life to evolve, the age of the … Continue reading →

Did Herschell really see life on the Moon?

Urban Astronomer avatarPosted on by

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?

Urban Astronomer avatarPosted on by

  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?

Urban Astronomer avatarPosted on by

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 →

How do you measure the brightness of stars?

Urban Astronomer avatarPosted on by

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 →