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The Sun and the Earth


We are discussing : where the Sun sets in April and September.

Can we see the motions (in our minds), of the Sun and the Earth, that

make those Sunsets?

Start at the Beginning


09/10/19
Maddy,
1. Imagine the Sun, and the Earth in it's orbit.
2. The Earth is rotating.
3. Imagine that  today  is the Summer Solstice.
4. Sit in a chair at the North Pole.
5. The time is Noon.
6. Your horizontal line of sight is downward by 23.5°, below the Sun.
7. Your chair is tipped forward by 23.5°, right ?
8. Now, make a change in perspective and orientation, by
9.     tilting the universe to your backward by 23.5°.
A. Now the Sun is 23.5° above the horizon.
B. Now, in your imagination, slow the spin of the Earth to one rotation per year.

What is the path of the Sun that you imagine to see for the year?

More to come ...

09/09/19
Maddy,
Your parents say that your guess for the dates, when the Sun will set behind
    Mt. Washington are: the Summer Solstice ±45 days.

    ±72 days is closer.


I have been thinking about this problem.

In our problem, we will assume the following:

1. The Earth's orbit around the Sun is a circle.
2. The Earth's orbit is in a flat plane, called the Ecliptic.
3. We will call Ecliptic Axis, the line that is perpendicular to the
    Ecliptic, and that passes through the Sun.
4. The Earth takes 365 days (one year) to orbit the Sun.
5. The Earth is spinning (the Earth rotates), and its axis of rotation
    points from the South Pole to the North Pole of the Earth.
6. The Earth rotates once, every 24 hours (one day).
7. The axis of rotation of the Earth is tilted by 23.5° from the
    Ecliptic Axis of the Earth's orbit.

This picture is not exact, but it will work well enough for us.

So, in your mind, imagine the Sun in the center of the picture, and the
Earth is orbiting around the Sun, and the
Earth is spinning (rotating) about its axis of rotation, which is
tilted 23.5° from the Ecliptic Axis.

Easy, right?

Our problem is to see ourselves sitting on the rotating Earth, and to see where, and
when, the Sun sets.

08/29/19
Maddy,                         ←  START HERE

If you look down my driveway at Sunset at about 6:30 PM, the Sun will be setting.

The direction down my driveway is 12 degrees North of West.

You can see Mt. Washington in that direction.

To Learn:

1. Understand the orbit of the Earth around the Sun.
2. Understand that the Earth rotates around its axis every day.
3. Understand that the axis of rotation of the Earth is NOT
    parallel to the axis of the Earth's orbit around the Sun.

Your Problem: on what two days of the year will the Sun
    set directly behind Mt. Washington, looking down my driveway?

An orrery may help to give perspective.


Good Works Party