Brain Teasers about astronomy
The following questions about the earth, moon, and sun all have simple
solutions that can be constructed without any advanced
technology. Just careful reasoning, cleverness and creativity.
How would you determine ...
- The shape of the earth.
- The size of the earth (circumference).
- The shape of the moon.
- Whether the earth goes around the sun, or vice versa.
- The relative distance of the sun and moon.
- The relative sizes of the sun, earth, and moon.
- Whether the earth spins under the heavens or vice versa.
Answers:
1. Eclipses occur at varying times, yet the shadow is always a
circle. The shadow of the earth on the moon during a lunar
eclipse was always circular. The only shape that always casts a
circular shadow is a sphere.
2. Eratosthene's heard there was a place where at midsummer's day
the sun could be seen at the bottom of a well. So he knew the sun
would be directly overhead. So on this day at noon he measured
the angle of the shadow cast by a vertical pole in Alexandria (500
miles north of the well.) The angle was measured at 7 degrees, so
he knew that 500 miles was 1/51 of a circle, and was able to estimate
the circumference.
3. The moon isn't a disk else we would see all light or all dark.
Phases of moon can only be caused by a sphere.
4. We must simply go outside every night for a year. At first the stars
will look like a jumbled mass, but as we get more familiar with them,
certain patterns become clear. Over a few months, the patterns will
slide sideways, disappearing over the edge of the horizon. At six
months, the original patterns will be completely out of view. Then,
over the next few months, they will turn back into view, and at the one
year mark they will return to their original configuration.
By keeping a careful record of the stars at night, including their
proximity to each other, we are able to see apparent shifts in star
position over time. These shifts in star position, paradoxically
enough, prove that universe around us is (relatively) stationary, and
we are the ones moving.
5.At first quarter, the angle from the moon to the sun is 90
degrees. So using a piece of paper he measured the angle from
earth to sun and calculated the ratio of angles. His crude
calculations were a ratio of 1 to 11. Modern measures are 1 to
400. (details).
6. Sun and moon have same apparent diameter, so since the sun is 11
times farther away, it was 11 times larger.
7. Foucault Pendulum