Category Archives: Astronomy

Lightning and the Earth’s Electric Field

A photograph showing some spectacular lightning bolts above a city skyline at night.Earth’s Electric Field

The Earth has an electric field.  On average, this field points vertically downwards and it has a magnitude of about 100 N C-1 (Newtons per Coulomb).  It exists because the Earth’s surface carries a negative charge of – 5 x 10C, while the upper atmosphere carries a compensating positive charge.  An average of 400,000 thunderstorms a day  Continue reading Lightning and the Earth’s Electric Field

How to Weigh a Supermassive Black Hole?

An artist's impression of a black hole.Black Holes

Black holes are known to exist at the centres of most galaxies, including our own Milky Way.  The masses of those black holes are correlated to many of the properties of their host galaxies, which strongly suggests that galaxies and black holes evolve together.  Measuring their masses Continue reading How to Weigh a Supermassive Black Hole?

World Views

Astronomical Beginnings

Early astronomers already make the distinction between stars and planets, as the former remain relatively fixed for centuries, while the latter wander an appreciable amount in a comparatively short time.  But that’s not all!

Continue reading World Views