Astronomy Overview and the Scientific Method

Practice questions covering introductory astronomy concepts, cosmic scales, planetary distances, and the fundamental principles of the scientific method.

What is the difference between Astronomy and Astrophysics?

Astronomy is the study of the positions, motions, and brightness of celestial objects, whereas Astrophysics is the application of physical principles to explain celestial phenomena.

How is Astrology defined in this course?

The belief that celestial phenomena govern or influence events on Earth.

What is an Astronomical Unit ($A.U.$)?

The average distance between the Earth and the Sun, which is approximately $150\,million\,km$ ($93\,million\,mi$).

What is a Light Year ($ly$) and its approximate value in distance?

A light year is how far light travels in a year, which is approximately $9.5\,trillion\,km$ ($6\,trillion\,miles$).

What is the constant speed of light ($c$)?

$c = 300,000\,km/s$ or $186,000\,mi/s$.

What are the approximate radii of the Moon, Earth, and Jupiter?

Moon: $1740\,km$ ($0.27\,R_E$); Earth: $6400\,km$ ($R_E$); Jupiter: $71,500\,km$ ($11\,R_E$).

What is the approximate radius of the Sun in comparison to Jupiter?

$696,000\,km$ ($432,000\,miles$), which is equal to $10\,R_J$.

What are the scales of the Milky Way and the Observable Universe?

The Milky Way is approximately $50,000\,ly$ in radius, and the Observable Universe is approximately $13.7\,billion\,ly$ in radius.

How long does it take light to travel from the Sun to Earth?

Approximately $8\,light-minutes$, representing a distance of $1\,A.U.$

What is the distance to the closest star, Proxima Centauri?

$4.23\,light-years$, which is approximately $40\,trillion\,km$ ($25\,trillion\,mi$).

What is the 'Pale Blue Dot'?

An image of Earth taken by Voyager 1 on February 14, 1990, from a distance of approximately $6\,billion\,km$ ($40.5\,A.U.$).

What is the origin and meaning of the word 'Science'?

It comes from the Latin word 'scientia', meaning 'knowledge', and is defined as a systematic study of the natural world.

What is an 'educated guess based on observation' called in science?

A Hypothesis, which must be testable and follow Occam's Razor.

What is the principle of Occam’s Razor?

The principle to accept as true the simplest explanation that satisfies all the data about a given thing.

In scientific terms, what is a 'Fact'?

An objective and verifiable observation that is measurable, specific, and independent of the observer.

What is the scientific definition of a 'Law'?

A statement based on observation that describes the world and how it behaves; it summarizes facts but does not explain why.

What is a 'Theory' in the context of the scientific method?

A verifiable and substantiated explanation based on facts and evidence that has been tested through the scientific method at least once.

According to Carl Sagan, what are the two rules of science?

First: there are no sacred truths and arguments from authority are worthless. Second: whatever is inconsistent with the facts must be discarded or revised.

According to Isaac Asimov, what phrase heralds new discoveries in science?

‘hmm…. that's funny….’

What unit system is primarily used in the science of astronomy?

The Metric System.