Tagged “Observing”

6 articles

Solar and lunar eclipses: two shadows, not one phenomenon

A solar eclipse is the Moon's shadow sweeping across Earth; a lunar eclipse is the Moon entering Earth's shadow. That difference sets how wide the viewing zone is, how long it lasts, and whether eye protection is required.

3 min read1

The Solar System

Comets: origin, structure and fate

Barely heated or altered in 4.6 billion years, comets are the closest thing we have to the raw material the planets were built from — and Rosetta's in-situ data revised a good deal of what was believed about them.

3 min read2

Observing the Sky

Aurora: light made by Earth's own atmosphere

What arrives from the Sun is energy; the light itself comes from oxygen atoms and nitrogen molecules high in the atmosphere after electrons strike them — and the lifetime of each excited state is why each altitude has its own colour.

2 min read2

Observing the Sky

Why astrology is not a science

Not because it is old, nor because Earth's axis has shifted. The decisive reason is elsewhere: whenever it is tested double-blind, astrology performs no better than chance.

3 min read4

Stars and Galaxies

The 20 brightest stars in the night sky

Ranked by apparent magnitude — brightness as seen from Earth, not true luminosity. Sirius leads because it is close; Deneb makes the list from hundreds of times farther away.

3 min read2

Observing the Sky

The constellations of the zodiac

The ecliptic is the Sun's yearly path across the celestial sphere. Under the modern definition of constellation boundaries it crosses thirteen of them, not twelve.

2 min read3