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.
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.
See The Orbit of Mercury – Aldebaran to Pollux
At night, you can use stars to help visualize the size of the inner planet’s orbits.
To visualize that in the night sky (in springtime) Mercury’s orbit spans from Aldebaran to Pollux.
Astronomers use “hours” to measure east to west sky movement. Mercury’s orbit spans 3.5 hours.
See The Orbit of Venus – Regulus to the Pleiades
Venus’s orbit spans 7 hours of the sky.
To visualize that in the night sky (in springtime) Venus’s orbit spans from Regulus to the Pleiades (the seven sisters).
Summary
We answered the question: If you could see the orbit of Venus would it fill the whole sky? The answer is no, it would fill only part of the sky. We learned a Physical Astronomy technique for how to see the orbits of the two inner planets Mercury and Venus.
Nicely done. Perhaps you could define an ‘orbit’ for the younger children? Also, have the’details’ fields fill in automatically for fans who’ve previously posted. Probably would increase the number of comments? Keep those posts coming!
Thanks for the feedback. That’s one of the hardest things about teaching these concepts to a wide range of ages – it’s also one of the most challenging and fun aspects too. Orbit means flying around in a “circle” around something bigger.
I’ll look into a way to avoid making you type your email each time – that’s a good idea!
Image of venus orbit is shown a hour or two (ie 2-4 sun-travel weeks) off, compared to stellar signposts noted….shown extending from Cancer out toward Aries). I get that you’re trying to use the same sun-point, but it’s confusing to not find Regulus in the image.
Aha! Good catch. I will regenerate a more accurate image that matches the text of the article. Thanks Jim!