Galileo’s Middle Finger

Galileo’s Middle Finger

In 1737, Galileo’s body was moved from one burial place to another. During the move several of his fingers and a tooth were removed from the body. Gruesome as it seems, this was a common treatment for the bodily remains of famous people.

One of the fingers – his middle one – eventually ended up in a museum in Florence where it sits (standing straight up) on a marble plinth under a glass jar.

Galilieo’s Middle Finger. From Wikipedia – Photo by User Saliko

Galileo’s science won the day, eventually, and after much suffering. However, thanks to this wonderful museum display, Galileo also got the final word in his epic battle with the powers of the Roman Inquisition – he’s giving them the finger – until eternity.

References:

Galileo Galilei wikipedia page

Constellations of the Zodiac in Order

Learning the Zodiac constellations in order is a great way to get familiar with the ecliptic and the celestial sphere. The Zodiac is not just for astrology – astronomers use the constellations of the Zodiac to name 13 regions of the sky.

Zodiac Constellations zoomed in on Ophiuchus – the “13th” Zodiac Constellation between Sagittarius and Scorpio. The constellation borders (marked red) show how astronomers divide up the sky into named regions.

Zodiac Constellations List

These are the Zodiac constellations in the correct order from Aries to Pisces.

OrderMnemonicNameDescriptionEmojis
1AllAriesRam♈ 🐏
2TheTaurusBull♉ 🐄
3GreatGeminiTwins♊ 👯‍♂️
4ConstellationsCancerCrab♋ 🦀  
5LookLeoLion♌ 🦁
6VeryVirgoVirgin♍ 👰
7LovelyLibraScales♎ ⚖️
8ShiningScorpioScorpion♏ 🦂
9OrderlyOphiuchusSnake-wrestler⛎ 🐍🤼‍♂️
10StarsSagittariusArcher♐ 🏹
11CreatingCapricornGoat-Fish♑ 🐐🐠
12AnimalAquariusWater-bearer♒ 🚰
13PatternsPiscesFish♓ 🐟
Table showing the order of the Zodiac Constellations, their names, descriptions, and emojis

Memorize the Constellations of the Zodiac in order

This mnemonic (memory device) can help you remember the correct order of the constellations of the Zodiac. This is the best way to memorize the order of the constellations of the Zodiac. It starts with Aries and ends with Pisces.

“All the great constellations look very lovely; shining, (orderly) stars creating animal patterns.”

Alex Davo (original – orderly added by DC)

This sentence is good too – it’s a little bit more romantic.

“A time gone, cowboys loved viewing little stars, (oh) so cold and pretty.”

– Terry Johnson (original – oh added by DC)

Why does the Zodiac constellations list start with Aries?

When astrology was invented it was the same activity as astronomy – observing and cataloging sky objects and their locations) but over the years the two practices have become very different. Astrology is now concerned with how the movement of the skies affects humans while astronomy has become a science. Scientists build knowledge to make predictions about physical events.

During early astrology/astronomy times, the most important thing about the study of the stars was to know where the Sun, Moon, planets, and other solar system objects were located in relation to the steady, orderly background of stars.

Why does the order of the Zodiac constellations read right to left?

The Sun moving “through” Aries into Taurus over a month. Each frame of the animation is about 3 days.

The Sun, Moon, and planets seem to move “through” these 13 constellations in order through the year. Starting with Aries, let’s follow the movement of the Sun against the backdrop of the steady stars. The next constellation that the Sun “moves into” is Taurus. Taurus is to the east (left) of Aries! The Sun appears to move into the next Zodiac constellation about once a month.

We know that the Sun is not moving – that it only appears to move through the sky – and that it is the Earth’s orbital motion that is creating this apparent movement.

Why did we add Ophiuchus to the original 12 Zodiac constellations?

Ophiuchus is a constellation, not an astrology “sign.” However, it is an official constellation that intersects the ecliptic. So, while astrologers do not consider this a Zodiac sign, astronomers include it because the constellation is located on the ecliptic.

The Ecliptic is a path in the sky that solar system objects follow

The solar system objects move generally west-to-east in a small band of the sky – this band of sky is called the ecliptic. All the Zodiac constellations are “on” the ecliptic and all the Sun, Moon, planets and other solar system objects move along the ecliptic over time.

There is another line in the sky called the celestial equator that is an imaginary line the rises from the equator of the Earth. The celestial equator and the ecliptic intersect at a “location” in the sky.

Right now in 2020 that intersection location is “in” the constellation Pisces.

The thin, diagonal line that connects the Zodiac constellations is called the ecliptic. This image shows the ecliptic intersecting with the celestial equator.

However, when astrology was created this intersection point was “in” the constellation Aries.

This image shows the intersection of the ecliptic with the celestial equator in the year 100 BCE.

This was known as the “First Point of Aries.” Astronomer Guy Ottewell writes about this imaginary point in the sky on his website UniversalWorkshop.

Summary

You can learn the order of the Zodiac constellations by using the mnemonic device shown in this article. There is a pathway in the sky that the solar system objects seem to follow. It is called the ecliptic. The Zodiac constellations are the 13 constellations lined up in the sky “on” this imaginary line.

The order of the Zodiac constellations is made because of the way the Sun, Moon, and planets seem to move east-to-west past these constellations in order during the year.

We start the Zodiac names list with Aries because the Zodiac constellations were first named thousands of years ago. At this time, the ecliptic intersected the celestial equator “in” the constellation Aries.

Earth Map in the Sky

Earth Map in the Sky – Landforms as Constellations

Learn how to see the map of Earth in the starry sky.

Stars help us find our way. Stars are like a giant map in the sky that tells us where we are on the surface of the Earth. Sailors use them as a “map” to navigate the world. For thousands of years, the stars were stationary markers of latitude and longitude.

We are going to learn to map something new onto the sky: locations on the Earth! We can create an exciting new set of “constellations” out of the shapes of the continents on the Earth.

We live on a sphere so we can see half of the sky (a hemisphere) at any one moment. It’s easy to imagine half the Earth mapped onto half the sky. Keep reading to learn how.

A new way to experience life on a sphere. It’s an Earth map projected onto the starry sky. Image created by: Daniel Cummings

Zenith Stars

Wherever you are on the Earth, when you look straight up (toward your zenith), you might see one star, but there are a bunch of other stars within view. All of the stars you see in the sky are directly overhead some other place on the Earth. Every place on Earth has their own set of stars directly overhead – their “zenith stars.”

Look up at any star in the night sky; that star is directly over some place on Earth. There are hundreds of “faraway zeniths” up there.

World Zeniths – See the Map of the Earth in the Sky

Every star maps to a location on Earth and every location on Earth maps to a star.

If you live in the western hemisphere, you can learn to look up and “see” the land borders of the North American and South American continents visible, projected into the sky like a giant painting on a curved ceiling. You can learn to see even more landforms in the sky – you can learn to see the entire western half of the Earth projected in the sky.

Visualize Countries in the Sky

We can learn to see country outlines in the sky. The key is to imagine yourself at the center of the Earth looking out into space “through” a translucent Earth surface.

Here is a good way to visualize these countries-in-the-sky even when you are on the surface. Imagine that you can look up and see your location at the zenith.

When I do this, I see southern New York state, Long Island jutting out into the water like a long pier, and the wide Hudson River emptying past New York City. Eastward is the dark expanse of the Atlantic Ocean and low on the eastern horizon are the countries of Europe and West Africa.

Westward in the sky, I can see the outline of the west coast of the US. Then, there is a big blank space of the Pacific Ocean and a spot near the western horizon that is Hawaii.

The Map of the Earth in the Sky is Reversed

Map of Earth landforms as they map to the starry sky. Map is reversed because it is projected into the sky. The places named at the cardinal directions (N, E, S, W) are the locations where New York horizon stars are zenith stars. Image created by: Daniel Cummings

There is one odd thing about the map as you see it in the sky… it’s reversed – as if seen in a mirror! This happens because we project the map lines outward into space toward the stars. When we look at the map this way it’s as if we are “inside” the Earth looking outward.

The map of the USA covers about 58˚ of sky from east-to-west. 58˚ is about 2x pinky-to-thumb (spread out all your fingers of both hands and touch thumbs). Your left pinky tip should be on your zenith. If you are in New York or somewhere on the east coast, the right pinky tip will indicate the approximate western edge of the USA.

Physical Astronomy – Stars Map to Places on Earth

Physical Astronomy Activity Instructions to learn to see the Map of the Earth in the Sky. Faraway Zenith stars help us visualize what it is like to live on the surface of a sphere. Image created by: Daniel Cummings

Learn to see the zenith map in your sky using this Physical Astronomy technique.

Exercise 1: face south and point high in the sky.

Face south. Then, reach both hands straight up over your head and point above your head with both pointer fingers. You are pointing at your zenith. Now, bring both arms down until they are pointing one due east and one due west. You are pointing at two points in the sky that are zeniths for someone else.

When I do this exercise in New York, my left hand (the eastern) points at a spot in the starry sky that is the zenith star for someone in the country of Nigeria in West Africa. This is a location on the globe that is 6 time zones east. My right hand (the western) points at a spot in the sky that is the zenith for someone in the island state of Hawaii in the middle of the Pacific Ocean. This location is 6 time zones west of New York.

So, when I look at the eastern horizon sky I am looking at the starry sky that is already directly above a place 6 time zones ahead of me. I am looking at someone else’s zenith stars.

Exercise 2: Repeat exercise 1. But this time, face east.

Face east, point up. Now, bring your arms down and point toward the north and the south directions. This time your right hand points south and your left hand points north. Your right hand points at a spot in the sky that is over the city of Cuzco, Peru (the closest city to Machu Pichu) and your left hand points to sky that is over Yekaterinburg, Russia – the 4th largest city in Russia.

Secret! You Can See a Star That Another Person Can’t

If you do this physical astronomy exercise right after sunset, the eastern and southern zenith locations are in night, but the western and northern sky points are over Earth locations that still have daytime.

This means that you can see the star that is at their zenith, but they cannot see that star. For example, Seattle still has 3 hours of sunlight left in their day so stars are invisible behind blue sky. The city of Yekaterinburg is on the opposite side of the world and just after sunset in New York it faces the Sun and has a bright daytime sky!

We are on the night time side of the Earth and we can see the current zenith stars of Seattle and Yekaterinburg – but people who live in these cities cannot see them! They have to wait to rotate to the night time side of the Earth to see stars.

The Math – How High Up is the Zenith Map?

Guy Ottewell’s illustration from Astronomical Companion (page 8). This schematic shows how we experience the celestial sphere – the array of stars in the sky. It shows zenith, cardinal direction points, the meridian, the celestial equator, the ecliptic, and the viewer – you, in England – sitting on the globe at latitude 40˚ north, looking up at the sky. Credit: © 2016 Guy Ottewell – UniversalWorkshop.com – used with permission.

Project an imaginary map of the Earth into the sky. The map has to be the correct size so that when it is viewed from a distance it “covers” the same distances.

If a map is too close, it is just the same size as the territory. So, we have to choose the correct distance to project the zeniths. As the zenith map “projector screen” moves away from the Earth we see more of the borders of the Earth. But, at some point the distance of the map corresponds exactly to the faraway zeniths.

Our question is: “How far away from the Earth do you have to be so the landforms (like the continents) have an angular diameter that is equivalent to their “actual size” in the sky?” How far away does our imaginary zenith map USA (about 3000 miles wide) image have to be to cover 58 degrees of arc in the sky?

To answer this we need math.

The Zenith Map Distance from Earth

Earth map showing close up of Algol passing over New York City while Gorgonea Tertia approaches Washington DC. Almach is the Zenith Star somewhere near Chicago, IL. The Earth’s rotational speed at this latitude makes the stars appear to travel a little bit faster than the speed of sound. They will be Zenith Stars for a location about 800 miles west in 1 hour. Image created by: Daniel Cummings

The Earth is approximately 24,901 miles in circumference at the equator. If we can see half the sky from any point on the Earth, then we can “see” half the Earth projected onto the sky by the zenith map. That means that for 180˚ of sky we can “see” about 12,450 miles of the Earth’s surface projected into space. 12,450/180 = 69 miles. When 1 degree of arc spans 69 equatorial miles the image is “at” the correct distance.

1 Degree of Sky equals 69 Miles

So, at the equator every degree of sky covers about 69 miles in every direction. As you go towards the poles the longitude degrees (east and west) cover less and less zenith map distance, but the latitude degrees (north and south) always stretch 69 miles. Every 15˚ of sky equals about 1035 (69*15) miles.

The distance between your pointer finger and your pinky (when you hold your arm and hand stretched out in front of you) is 15˚ – so you are measuring about 1035 miles on Earth with that sky measurement. One pinky width is equal to 1˚, which is 69 miles of zenith map!

The Math – Inverse Tangent and Angular Diameter

There is a simple calculation that helps us determine how far away something needs to be to fill just 1˚ of the sky. Here we use just a tiny drop of trigonometry to discover the “tangent of 1 degree.”

The tangent of 1˚ is 0.017455. The inverse of something is when you divide 1 by the number you want to invert. So, the inverse of 0.017455 (1/0.017455) is 57.29. The inverse of the tangent of 1˚ helps us figure out the distance something has to be to appear to be 1 degree angular diameter.

This page explains how to calculate distance from a known angular size. “When an object’s distance is 57.29 times its size, it has an angular size of 1 degree.”

So, 57.29 * 69 miles = 3,953 miles away! This is how far away the “map” has to be to show you your hemisphere of the Earth map. 3,953 miles is higher than low Earth orbit (LEO) satellites (lower than 1200 miles); it’s closer than geosynchronous satellites (at about 23,000 miles); and it’s about 1/60 the way to the Moon.

So, imagine that the Earth map is projected onto a screen – an imaginary celestial sphere, shell-shaped – that is quite close to the Earth and encircles us. It shows us our Earthen landforms and the oceans beside, superimposed in the sky.

Summary

We live on a sphere. When we look at out night sky we are able to see stars low on our horizon that are visible directly above someone else – one-quarter the way around the around the world in all directions.

If you live within 6 time zones of someone that means that you share some “simultaneous sky.” Anyone living further than 6 time zones away sees a completely different sky – unless you can see circumpolar stars that dip under the North Star. That means that you can see countries past the North Pole and down the other side of the globe.

Your zenith is yours – it is unique and changing all the time. Not even someone standing right beside you shares your zenith. You can use this idea of the zenith stars to comprehend the vast and mysterious experience of life on a sphere.

References

A list of extreme geographic points in the USA – Wikipedia – https://en.wikipedia.org/wiki/List_of_extreme_points_of_the_United_States

Your Eyeball Sun – Scale Model of the Solar System

The Sun is the Size of your Eyeball

The solar system is huge. A good way to understand it is to create a scale model. In this scale model, the Sun shrinks to the size of an eyeball and the rest of the planets shrink too. Credit: https://pixabay.com/en/eye-blue-macro-sun-yellow-human-2938947/
What would the rest of the solar system look like if you shrank the Sun to the size of an eyeball?

You are the center of the universe.

Well, at least you are for this scale model. You will be the Sun.

Imagine that the Sun shrank to the size of one of your eyeballs (about 24mm diameter) and it got placed inside your head. You are now the Sun, center of the solar system, looking out into the vast expanse of the solar system and space beyond.

Mercury is just 1 meter away – it is microscopic, essentially invisible at one tenth of a millimeter (0.1mm), the tiniest grain of sand. But if you reach out your arm and point your fingertip as far as it will go, you can almost touch it. Swing your arm around and you trace its orbit around your eyeball sun.

Venus is 1.86m (6ft) away – about the height of a tall-ish man. The second planet from your eyeball Sun is a little bit bigger than Mercury, but still almost invisible at the size of a single grain of fine sand (0.2mm).

Earth is 2.5m (8ft, 2in) away – just a bit farther away than Venus. You can’t reach it with your outstretched hand; you would have to take a step towards it. Earth is also a little bit bigger than Venus, but not by much. And at this scale, the Earth is just another fine grain of sand so it’s almost impossible to find anyway.

The Moon, smaller than Mercury, orbits just 0.6cm from the Earth sand. Imagine… your eyeball and two tiny grains of sand held in a 5m (16ft) diameter orbit.

Imagine all the empty space in the solar system. Imagine all humans on the surface of that Earth grain – and we have only visited the first 3 planets.

Mars is smaller than Earth and orbits 3.9m (12ft 10in) away. It is another grain of sand – with a red tint.

Jupiter is 13.4m (44ft) away. Imagine the outside length of a large school bus – that’s how far away Jupiter is. Jupiter is the first planet in this scale model that is visible – it is 2.5mm diameter – at this scale, Jupiter is about the size of a small peppercorn.

Saturn is 24.6m (about 81ft) distant. It has shrunk to the size of half a sprinkle. This sprinkle crumb is far enough away from your eyeball Sun that you probably couldn’t see it.

Uranus disappears at 0.8mm and 50m (162ft) away. It’s about the size of a small ant’s head.

Finally, we reach the similar-sized ant-head Neptune at 0.8mm which is an astonishing 77m (255ft) away at this scale. This is a bit closer than the entire length of a football field or a soccer pitch – Neptune would be at the other team’s 20 yard line or 18 yard line respectively.

Summary

Close your eyes. Imagine your eyeball is the Sun.

All these tiny objects are orbiting your head at different distances in a more-or-less flat plane.

Out. In. Space.

References

Thanks to Guy Ottewell for his insights into how to use everyday objects to communicate the scale of the solar system – especially his groundbreaking Earth as A Peppercorn.

10 ways to wear a Moon Hat

Wear the Moon Hat – have fun!

The Moon Hat is no ordinary hat. 

The Moon Hat keeps your head warm – yes!  And, every day it gently reminds you to be curious about the Moon. It reminds you to observe what usually stays hidden. It reminds you to #doscienceeveryday.

There are many ways to wear a Moon Hat. You can wear the Moon Hat in at least 10 different ways. The Moon Hat is made of soft stretchy fleece with small embroidered Moon phase images placed all around the brim.

The Moon Hat fabric is flexible and foldable.

10 ways to wear the Moon Hat

  • Moon Finder – where is the Moon right now
  • Phase Reminder – what is the Moon phase right now
  • Hidden Moon outside – hide the moons outside
  • Hidden Moon inside – hide the moons inside
  • Tidal Shores no tag – longshoreman style
  • Tidal Shores show tag – longshoreman style
  • Moon Slouch – Moon Finder, pull the fleece backward
  • Moon Beret – Moon Finder, pull the fleece forward
  • Moon Disk – Hidden Moon inside, show one embroidered disk
  • Moon Peeker – Hidden Moon inside, peek one embroidered disk
  • Halfsies (Bonus #11) – Hide half the phases, wear the hat straight

#1 – The Moon Finder

The Moon Hat style The Moon Finder. This is the standard style for wearing the Moon hat. The phases are oriented in the correct way and you can face the Sun and find the Moon using the Moon Hat moon phase images.

The standard way to wear the Moon Hat with the new Moon image in front. This creates the model of the Moon, Earth, Sun relationship and helps you understand how the motions of the Moon create the phases that we see from Earth.

Get the current Moon phase. Put the hat on with the New Moon image on your forehead. Face the Sun. Now, all of the Moon phase images point to where the Moon is in the sky. Amazing!

#2 – The Phase Reminder

The Moon Hat style The Phase Reminder This is another standard style for wearing the Moon hat. The current phase is oriented to the front and you can face the Moon and find the Sun using the Moon Hat New Moon phase image.

This everyday style is for people who want to remind themselves of the phases of the Moon and how they change over the 29 and a half days of the cycle. Just choose a Moon phase and put it at the front.

This is a subtle way to keep track of the Moon phases and learn their sky location. Before you put on the hat, pause for a second and consider which phase to wear. And, it doesn’t feel like a Moon phase quiz – it’s fun to put your thinking cap on!

#3 – Hidden Moon outside

Man wearing the Moon Hat hiding all the embroidered images of the Moon Phases. Sometimes you just want to wear a cap.

Don’t want any Moon phases to show? Just fold up the brim toward the outside of the hat and all of the Moon phase images disappear.

Sometimes a hat is just a hat.

#4 – Hidden Moon inside

Moon phase images are all hidden by folding the brim of the Moon Hat inside the hat. It gives a slightly exotic look to the cap.

Another way to hide the Moon phase images… tuck the brim of the Moon Hat towards the inside. All the Moon phase embroidery is now hidden and you have a sleek cap.

Looking for a unique style? The Moon Hat is flexible.

#5 – Tidal Shores no tag

The Moon Hat style the Tidal Shore No Tag - the hat starts inside out and the brim is folded up to reveal the images. This is another standard style for wearing the Moon hat. The New Moon image is oriented to the front and you can face the Sun and find the Moon using the Moon Hat New Moon phase image.

This is the longshoreman style. Turn the Moon Hat inside out and then fold the brim outward. The brim should be wide enough to both show the Moon phase images and hide the instruction tag.

A close-fitting style that uncovers your ears.

#6 – Tidal Shores show tag

The Moon Hat style the Tidal Shore Show Tag - the hat starts inside out and the brim is folded up to reveal the images. This is outre style for wearing the Moon hat because the tag is showing. The Full Moon image is oriented to the front and you can face the Full Moon and find the Sun using the Moon Hat New Moon image.

Just like the Tidal Shores no tag, but the brim of the hat is folded thinly so that the tag is revealed. You can wear the tag on the side, or the back, or if you are feeling daring, on the front!

This style makes a strong statement – show off the instruction tag.

#7 – Moon Slouch

Man wearing the Moon Hat in slouch style. The hat is loosely bunched and then pulled backward to give a relaxed ring of Moon phase images that are carried above the ear.

This is the Moon Finder style, but pull the Moon Hat upwards to get some amount of fabric standing up away from your head and then pull it backward and flatten it for a sleek look

You can easily wear the Moon Hat pulled up above your ears.

#8 – Moon Beret

Man wearing the Moon Hat in beret style. The hat is loosely bunched and then pulled forward to give an intense ring of Moon phase images that are carried above the ear.

This is the Moon Finder style, but pull the Moon Hat upwards to get some amount of fabric standing up away from your head and then pull it forward and flatten it for an intense look.

Folding and bunching the fabric in the hat leads to a renaissance or jester look.

#9 – Moon Disk

A single Moon Phase image shows at the back of Man's head but hiding all the other phases.

The Moon Disk style starts with the Hidden Moon inside, but then you pull the embroidered disk of your favorite Moon phase and place it somewhere – it could be centered on your forehead or placed round the side of your head just behind the ear, or all the way at the back. It’s your choice.

This style lets you show an individual Moon image disk.

#10 – Moon Peeker

This is the same as the Moon Phase disk, but more discreet. Just a tiny Moon phase image disk peeks out from just in front of the right ear.

This style is the same as the Moon Disk, but pull the Moon phase under the fabric of the brim until it is just peeking out. This style looks particularly good when the disk is just in front of your left or right ear.

This look makes a sly statement.

#11 – Halfsies 

Half the Moon Hat brim is folded upwards to hide a set of embroidered moon phase images. Hat is adjusted to make it look symmetrical.

Fold down half the Moon Hat brim to hide 4 of the phases, then adjust, and angle the hat so that it looks like it is sitting flat on your head.

An alternative way of hanging your hat.

Go out and play with the Moon Hat

This is a fun and flexible bit of fabric with lots of science and a mountain of style potential. Hide and show the Moon phase images, fold and flex the fabric. Get outside and get curious about the Moon and its motion.

How can I see Venus?

You can see Venus in the sky at two times and locations:

  • in the early evening, shortly after sunset in the west or
  • the early morning, shortly before sunrise in the east. 

Venus orbits the Sun and moves from evening sky to morning sky and back again over the course of about 18 months. Venus makes beautiful sweeping motions in the sky that reveal secrets of the solar system.

See Venus, see the plane of the solar system

Solar system plane
The planets all orbit the sun in the same plane. Image not to scale.

All the planets in the solar system orbit the sun. All of the orbits line up in neatly nested concentric rings. And all of the rings are lined up with each other as if they are placed on a single surface together.

The orbits are all in the same plane. It’s like they are all marbles circling around the sun on the same giant plate. This is called the “ecliptic” and it is visible in the sky if you know how to find Venus.

Intersecting space planes

The “space plane” is not an airplane

The “plane” is a tool you can use to see the way things move in space. This “plane” is not an airplane, but a flat slice of space.

Here is an image of two intersecting planes. Imagine the blue plane is the earth’s surface and the brown plane is up-and-down from ground to sky.

Each object (and movement) in space creates a “plane,” an imaginary slice through physical space. The blue “plane” above looks like the surface of a pond, lake or ocean. A wall or roof of a house is a plane. A dinner plate is a plane. Stretch your arms out and spin in a circle and you have created a plane with your arms.

There are planes in space everywhere.

Your own personal space plane

You create a plane with your vision and balance. You can imagine a flat surface like the surface of a pool of water and your eyes are just above the waterline. This surface moves and tilts when you move your head.

Your head has two eyes that define your plane of vision. Also, your body is oriented to gravity because of your sense of balance – the “personal horizon” is the first plane for you to orient to. Your body naturally coordinates your visual sense with your sense of balance and gives us the sense of being located level on a surface. This is the “sense of horizon.”

A new horizon – choose a plane!

To get good at Physical Astronomy, we have to learn to coordinate our main “personal horizon” plane with other planes of the earth, moon, solar system, galaxy, and universe.

The earth for instance, has a lot of planes, the range of latitudes, the north and south poles, the Arctic and Antarctic circles, the equator, the tropics, a range of longitudes, the prime meridian, the international date line, the ecliptic, the galactic plane and more.

To keep things simple, let’s focus on just one other plane for now: the plane of the solar system. A wonderful thing will happen when you learn to link the plane of vision with the plane of the solar system. It’s pretty easy to do, and it’s a skill that gets better with practice.

The key to linking vision and solar system planes is to know that the plane of the solar system is visible as the ecliptic. One easy way to see the plane of the solar system is to see the bright inner planet Venus.

See Venus see the orbit of Venus in the western sky just after sunset. See how the line from Venus to the Sun defines the ecliptic.
See Venus and you can see the orbit of Venus

See Venus and the Orbit of Venus

Venus is closer to the Sun so we are able to see its entire orbit. Actually, we can’t quite see the entire orbit because sometimes it goes in front of the sun and sometimes it goes behind the sun.

We can see Venus in the early evening and in the early morning. Venus is visible in our sky when it is at the left and right extent of its orbit around the sun. We only see Venus in the sky when it is swooping around the left or right of the sun.

If you want to see the orbit of Venus and see the plane of the solar system you can do it! All you have to do is imagine a line connecting Venus to the Sun.

If you are looking at Venus early in the morning before sunrise or early in the evening before sunset, the process is the same. Imagine a line connecting Venus to the Sun; this is the ecliptic. Venus’s entire orbit covers roughly 1/4 of the sky.

Summary

We learned about two main planes in space: your personal horizon (which changes as the Earth carries you around the Sun) and the plane of the solar system: the ecliptic. 

By learning to visualize these two space planes, we can begin to experience the extremely large dimensions of space.

References

Venus information from In the Sky.

8 Ways to Find the North Star

Find the North Star

You can use these 8 ways to find the North Star (Polaris). These are all fun ways to find the North Star.

Can you find the North Star in this image? It is the star that is closest to the middle of the concentric rings of star trails. This is a long exposure photograph of real stars as seen over the course of several hours during the night.
A long exposure photograph showing all of the other northern sky stars circling around the North Star. Image provided by ESO.

8 ways to find the North Star

  1. Look north and guess – you can find the North Star in a relatively dark region of the sky and there are not many other bright stars around it. If you are south of the equator, head north before you try to look for the North Star because you won’t be able to see it until you get the Earth out of the way.
  2. Use the Big Dipper cup stars as pointers. This is the classic way to find the North Star. The two stars of the Big Dipper cup are known as the “pointer stars” and they show you which star is the North Star. The North Star is about 5 lengths of the pointer stars away.
  3. Camera timelapse – ooh! I love timelapse. A great timelapse of the night sky is an unbeatable way to relax. By taking a timelapse of the starry sky you can detect the apparent motion of the stars. If your timelapse covers enough of the sky  (with a wide angle view) chances are that you will be able to identify the North Star because it is the star that moves the least.
  4. Phone app – grab a planetarium app like SkySafari. Almost every star app these days has a “Augmented Reality” view that you can use to find Polaris. Just use the AR method of holding the phoone up above your head and searching around or you can type the name of a star into the search box in the app.
  5. Observe the sky, patiently measuring the movement of every star. The one that moves the least is Polaris. This might take a long time because the stars move pretty slowly.
  6. Mark a known spot as your North Star viewing spot. This is easy to do with a product like the Star Spot. You can return to that spot any time of day or night  to sight the star – the North Star is always in the same place in the sky.
  7. The North Star is located in between the two easy-to-identify constellations The Big Dipper and Cassiopeia – the Queen.
  8. Memorize its color and the stars around it – this is easier than it sounds! Polaris is a yellow supergiant and has a faint yellow tint. Also, the North Star is located in a region of the Milky Way that has fewer stars so it is surrounded by dark areas of the night sky.

Here is the classic way to find the North Star! Use the pointer stars of the Big Dipper. This is a reliable method for finding the North Star that has been taught to generations.

Find the Big Dipper to find the North Star

Look at the two stars in the picture below. One is Dubhe – which is labeled a for alpha, and the other Merak – which is labeled b for beta. These form the outer lip of the Big Dipper’s cup. These two stars can be used to create an imaginary line to “point” at the North Star.

The distance from the pointer stars to the North Star is about 5 times the distance between Dubhe and Merak.

The North Star is shown in this image as a red dot labeled “Polaris.”

You can find the North Star using the two pointer stars of the Big Dipper (Dubhe and Merak) The North Star is also called Polaris and is part of the constellation Ursa Minor.
Use the two pointer stars of the Big Dipper to find the North Star (Polaris). Picture credit user Bonĉ source Wikipedia

These instructions work for the 80% of people who live in the northern hemisphere – anywhere north of the equator. For the 20% of people who live in the southern hemisphere the North Star is not visible because it is blocked by the Earth. As you move south toward the equator (and eventually move past the equator), the North Star gradually sinks lower in the sky until it stays completely below the northern horizon.

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Where is the Sun?

Where is the Sun right now?

Can’t see the Sun? Maybe there is something blocking it. Here is a list of 10 surprising things that can block the Sun.

IMAGE of floating/flying things overhead (in roughly size order) that can block all or part of the SUN: Flying animals (Bugs, Birds/Flying Mammals), Flying objects (Drones/Balloons/Airplanes/Helicopters/Rockets/Bombs/Blimps), Smoke/Clouds, Spacecraft (Satellites/Space Stations/UFOs), Asteroids, Moon, Mercury, Venus, Earth.
Things that block the Sun.

Where is the Sun during the day? On a clear day, this is a very simple question. The Sun is “up there” in the sky – it’s a big, bright, fiery ball and it’s generally a yellowish orange color. You just point to it – there it is, up in the sky, the Sun.

However, many things can block the Sun. Usually, it is clouds that block the Sun, but not always. Let’s take a tour of the astonishing number of things that can block the Sun.

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Animal constellations in the night sky. How many are there?

There are 42 animal constellations in the night sky.

That is almost half of the official 88 constellations!

Here are the other types of constellations you will find in the celestial sphere. This is a fun activity for kids astronomy!

There are 42 animal constellations, 28 objects, 14 humans, 2 chimeras (a mix of human and animal), and 2 natural features (a river and a mesa).

Constellations are of many types. There are 42 animal constellations, 28 objects, 14 human constellations, 2 chimeras, and 2 natural features
88 official constellations broken down into 5 groups: 42 animals, 28 objects, 14 humans, 2 chimeras, and 2 natural features.

The 88 constellations listed by type:Click here to continue reading…

Blue Moon, Dark Moon, Nose Moon, Tail Moon

What is a Blue Moon?

The year 2018 is a Blue Moon bonanza! There was one in January and one on March 31st. The next one won’t arrive until October 2020. But, don’t worry… we’ve got 3 other types of moons lined up for you.

A blue moon tinted blue to make it look like the moon is actually blue. A blue moon means 2 full moons in a calendar month.
A Blue Moon. (This image was tinted to make it blue. No, a Blue Moon is not blue.)

The Basics

A Blue Moon happens when there is a Full Moon on the 1st* day of the month and a Full Moon on the last* day of the month. Two full moons in one month!

In other words, a Blue Moon is when there is a full moon twice in the same month. These two full moons always happen on the 1st or 2nd and the 30th and 31st of a month. “Blue Moon” is just a name for the second moon in that month – the moon does not turn the color blue.

Read on to learn about how the Blue Moon came to be and some suggestions for giving the other moon phases “Blue Moon” style names when they appear twice in a month. Suggestions are: Dark Moon, Nose Moon, and Tail Moon.Click here to continue reading…