sun and earth

From the height of the sun, day length and shadow, to the coordinates of the sun, solar terms and disk orientation.

Let’s do the four-season experiment first, and then look at the calculation of solar term dates and solar coordinates.

Let’s look at the phenomena in life first →

• Why does it get dark earlier when the sun is lower in winter?

  Standing in the same place, watching the sun in winter and summer take two different paths.

• Why isn’t the vernal equinox the same day and hour every year?

  Seasons are defined by the instant the sun passes in a prescribed direction, and calendars and clocks are simply ways of recording it.

• If you stand a needle on the ground, why can its shadow tell you the time?

  When the direction of the sun changes, the shadow of the needle tip moves along the disk. Test on a flat surface first, then mount the panel to the wall.

• Why does the sun move in different directions in the starry sky throughout the year?

  Calculate the background direction of the sun as seen from the center of the Earth, with the date fixed.

• Say where the sun is, why are there three numbers X, Y, and Z?

  The same direction and distance from the earth to the sun are projected onto three coordinate rulers.

• Why is the "north" in the sun photo not necessarily directly above the picture?

  The sun's rotation axis has its own tilt, and the sun's surface also has coordinates like the earth's longitude and latitude lines.