Category Archives: Astronomy

The Big Dipper and Ursa Major Across Time and Cultures

On a given night

With stars labelled
Image by Ken Christison

North American interpretation

Shang-di, aka, the Jade Emperor
Stone carving from the Wuliang Shrine, ca. 150 CE

Starry Plough flag of the Irish Citizen Army, 1914

From Abdul Rahman bin Omar al-Sufi’s Pictures of the forty-eight planets, ca. 950 CE

Egypt, from the tomb of Seti I at the Valley of the Kings, ca. 1280 BCE
Photograph by M. Sanz de Lara

Charles’s Wain, aka Charles’s Wagon, Europe, ca. 1500s CE

From Gaylord Johnson’s The Star People, 1921

As part of Ursa Major, described by Ptolemy ca. 150 CE

From Johann Bayer’s Uranometria, 1603

“Galaxy Song” with Notes and Alterations

Just remember that you’re standing on a planet ever changing,
Rotating at 1,000 miles an hour
Original: Just remember that you’re standing on a planet that’s evolving,
Revolving at 900 miles an hour

“If you were to hang above the surface of the Earth at the equator without moving, you would see 25,000 miles pass by in 24 hours, at a speed of 25000/24 or just over 1000 miles per hour.”*
It’s orbiting at 19 miles a second,* so it’s reckoned19 miles per second = 68,400 miles per hour.

“Earth is also moving around the Sun at about 67,000 miles per hour.”*
A sun that is the source of all our power“The energy we capture for use on Earth comes largely from the Sun or from nuclear forces local to our own planet. Sunlight is by far the predominant source, and it contains a surprisingly large amount of energy.”*
The sun and you and me and all the stars that we can see
Are moving at a million miles a day
In an outer spiral arm, at 40,000 miles an hour
Of a galaxy we call the Milky Way
1 million miles per day = 41,667 miles per hour.

“Relative to the local standard of rest, our Sun and the Earth are moving at about 43,000 miles per hour (70,000 km/hr) roughly in the direction of the bright star Vega in the constellation of Lyra….”*
Our galaxy itself contains a hundred billion stars“We can only see a few thousand stars at most with our unaided eyes. These are a mixture of stars which are nearby, and bright stars which are further away; but they are only a tiny fraction of the 100,000,000,000 stars in our own galaxy.”*
It’s 100,000 light years side to side“The disk of the Milky Way galaxy is about 100,000 light years in diameter (one light year is about 9.5 x 10^15 meters).”*
It bulges in the middle, 16,000 light years thick“The central bulge is about 16,000 light years thick.”*
But out by us, it’s just 1,000 light years highOriginal: But out by us, it’s just 3,000 light years wide.

“Astronomers estimate that the disk in the vicinity of the Sun is relatively thin—‘only’ 300 pc thick….”*

300 pc (parsecs) = 978.47 light years
We’re 30,000 light years from galactic central point“Of course, the edge on perspective represents the view from the vicinity of our Sun, a star located in the disk about 30,000 light years out from the center.”*
We go ’round every two hundred million years“At this rate it takes us 240 million years to make one revolution around the galactic core.”*
And our galaxy is only one of millions of billions
In this amazing and expanding universe
The universe itself keeps on expanding and expanding
In all of the directions it can whiz
As fast as it can go, at the speed of light, you know
11 million miles a minute,
and that’s the fastest speed there is
Originally, “12 million miles a minute.”

The speed of light is actually about 671 million mph which is 11,183,333 miles per minute.
So remember, when you’re feeling very small and insecure
How amazingly unlikely is your birth
And pray that there’s intelligent life somewhere up in space
‘Cause there’s bugger all down here on Earth

Light from Andromeda to Earth

The nearest large galaxy to the Milky Way is the Andromeda Galaxy. Sometimes astronomers call it M31, by its number in the famous Messier catalog of fuzzy celestial objects. The Andromeda … Galaxy lies about 2 1/2 million light years from Earth. The light we see from it tonight left it more than 2 million years ago, when our species was just beginning to establish its fragile foothold on planet Earth.