See Mercury and Venus orbits during the day

Your hands and arms help you see the orbits of Mercury and Venus and the shape of solar system

Question: If you could see the orbit of Venus would it fill the whole sky?

The answer might surprise you!

You can use your hands and arms to see the size of the orbits of the solar system’s inner planets: Mercury and Venus.

Imagine (as pictured below) if the orbit of Mercury were visible as a red oval and the orbit of Venus were visible in green.

Use your hands and elbows to see Mercury and Venus orbits any time of day or night. The orbits of Mercury and Venus can be seen.
Two hand spans show Mercury’s orbit, elbows show Venus’s orbit.

Physical Astronomy – see Mercury and Venus orbits

Caution! Do not look directly at the Sun without proper solar safety glasses on.

Turn toward the Sun, hold your arms out straight, hands up in the air with fingers spread wide and thumbs touching. Your pinky fingers now span the width of the orbit of Mercury and your elbows span the width of the orbit of Venus.

Both of the entire orbits of Mercury and Venus orbits would be visible in the sky all at once – if they could be made visible during the day.

Continue reading “See Mercury and Venus orbits during the day”

Galaxy Rise

Physical Astronomy by Daniel Cummings

A still more glorious dawn awaits Not a sunrise, but a galaxy rise A morning filled with 400 billion suns The rising of the milky way.

The Sun rises. The Moon rises. Stars rise. The Galaxy rises – twice.

Each day the Earth rotates and sky objects (seem to) rise in the Eastern sky. The Sun, the Moon, the Stars, and the Galaxy rise at various times.

The Sun “rises” once-a-day at the start of the day.

The Moon “rises” once-a-day at different times of the day and night depending on the moon’s orbit around the Earth (its phase).

The Stars “rise” once-a-day – all night long, one after another and in groups.

The Milky Way Galaxy “rises” twice a day – once on its bright (center) side and then 12 hours later on its dim (outer arm) side.

We can orient our bodies to the rising of the Milky Way. And we can experience our daily movement as “plunging through” this flat disk of stars.

Continue reading “Galaxy Rise”

Walk to Mintaka

Physical Astronomy by Daniel Cummings
Mistakable rises toward the zenith as you walk toward the equator
As you walk toward the equator, Mintaka appears to rise higher in the sky.

In this post we will learn how to use one bright star of Orion’s belt to visualize the Earth’s equator.

Mintaka is a Star in Orion’s Belt

When you look up at the winter sky in the northern hemisphere, Orion and his famous belt are impossible to miss. The belt is made up of three stars of equal brightness.

One of these stars is called Mintaka and it is a guidepost for finding the Earth’s equator in space. Continue reading “Walk to Mintaka”

Arms around the ecliptic

Learn to see the ecliptic

Physical Astronomy by Daniel Cummings

Ecliptic Arms

The sun follows the same path through the sky every day.

Sun up. Noon. Sun down.

The sun starts the day in the east in the morning, rises high in the sky at noon, and settles down again in the west for a nap at night.

See the ecliptic

Here is an exercise to discover that path – the ecliptic.

Continue reading “Arms around the ecliptic”

Stars like ours – 9 bright “Life Stars”

Life Stars – Visible Exoplanets

Physical Astronomy by Daniel Cummings

Life Star in the night skyA “Life Star” is a visible star that could host life. This is a name I came up with in February 2017 (around the time of the TRAPPIST announcement) to describe visible stars with confirmed planets orbiting in the habitable zone. “Life Star” is easier to say and explain. I hope it catches on! Continue reading “Stars like ours – 9 bright “Life Stars””

Stars in Your Eyes

Graphic showing text and milky way galaxy of stars. Stars end their trips in your eyes

The light of a star…

…no matter how long it has been traveling through space, ends its journey in your eye. The light hits your retina and is transformed into thought. As long as you let that star light stream into your view, the star itself lands in you and settles its motion.

When I was 17 years old I went on a weekend retreat run by the Christian Brothers near Melbourne, Australia. It was a weekend of spiritual teaching, introspection and reflection.

Saturday night, one of the other boys at the retreat surprised me. As we stood outside under the stars, he spoke in that matter-of-fact way typical of Australians.

Continue reading “Stars in Your Eyes”

The Moon Dance – Learn Moon Phases

PHYSICAL ASTRONOMY BY DANIEL CUMMINGS

The moon dance helps you learn and understand the phases of the moonAt sunset.

Face the sun.

Point your right hand toward the Sun.

Now point your left hand toward the Sun.

Both hands should be pointing at the sun.

Now, turn a little bit to the left, keeping both hands pointing at the sun.

Swing your left arm out until it is pointing in the opposite direction from the sunset. Bring your hands together again and repeat this swinging motion.

Bring your hands together again and point them both at the sun. This time, instead of swinging, bounce your left hand, leftward, some number of times… (14 is perfect if you can do it) …until it is pointing in the completely opposite direction from the Sun at sunset. Your left hand should now be pointing East.

Was the moon at any one of those 14 hand bounce spots? That is the age of the moon in days.

Please post your questions in the comments!

The Moon Moves Toward the Dawn – a Mnemonic

The moon moves toward the dawn

Memorize this mnemonic: The moon moves toward the dawn. This phrase describes the day-by-day movement of the moon. With this simple phrase, you can understand the phases of the moon. You will actually begin to see the moon’s beautiful orbit traced out in the sky.

Repeat. The moon moves toward the dawn. The moon moves toward the dawn. 

The moon moves toward the dawn.
It rises higher in the dusky sky after each day. It sweeps over the hills.
It circles and rolls. It transits. It leaves the Sun, then chases the Sun.
The moon moves toward the dawn.
Look East! That’s where the moon wants to go.
Once arrived, it crosses the face of the Sun and once again moves toward the dawn.
The moon moves toward the dawn.