Archive | November, 2016

Circles on Circles D.12.01

30 Nov

A “circles on circles” system used by Ptolemy to explain retrograde motion where circles rotate uniformly, but their rotation rates and rotation directions can differ – Deferent-Epicycle


The Placement of the Moon D.11.30

29 Nov

It can be inferred that the moon is between the Earth and the Sun due to the crescent phases of the Moon.

Greek Astronomy D.11.29

28 Nov

The geocentric model of planetary motion that lasted for 1600 years was proposed by Ptolemy

Days of the Week D.11.28

27 Nov

The days of the week get their names from the planets in our solar system.


Eratosthenes D.11.27

26 Nov

Eratosthenes was the first to calculate the circumference of the Earth.

A Light Year D.11.26

25 Nov

The distance that light travels in one year is what is called a light year.

Observable Universe D.11.25

24 Nov

The Observable Universe is the portion of the entire universe that can be seen from Earth which only makes up a tiny fragment of what is out there.