#37 Retrogrades and Transits

What is the term used to describe the apparent reversal of a planet's movement in the sky?

• Retrograde motion

• Direct motion

• Circular motion

• Linear motion

Which planets exhibit a similar apparent motion to Mars from our viewpoint?

• Venus and Mercury

• Jupiter and Saturn

• Earth and Moon

• Neptune and Uranus

What causes the apparent retrograde motion of Mars?

• Earth overtaking Mars in its orbit

• Mars moving faster than Earth

• The Sun's gravitational pull

• Mars changing its orbit

What is the effect called that astronomers use to measure the distances to faraway objects like stars and planets?

• Refraction

• Parallax

• Diffraction

• Reflection

How can the effect of parallax be demonstrated using your thumb?

• By moving your thumb up and down

• By holding your thumb in front of you and looking at it with one eye closed

• By rotating your thumb in a circle

• By tapping your thumb on a surface

What is the baseline provided by the diameter of Earth for measuring distances using parallax?

• 10,000 km

• 12,742 km

• 15,000 km

• 20,000 km

What is the angular diameter of the Sun in the sky used for calculating the parallax angle for Venus?

• 0.25°

• 0.53°

• 1.00°

• 1.25°

What is the formula used to calculate the distance to an object using parallax?

• D = 0.5B / tan(0.5α)

• D = B / tan(α)

• D = 2B / tan(α)

• D = B / sin(0.5α)

What is the first step in creating a parallax angle measuring tool?

• Push a pin completely through one end of the straw.

• Place a protractor on a corkboard or thick cardboard and tape it in place.

• Place the straw on the protractor and push the pin through the hole.

• Lay down a measuring tape to act as your group's baseline.

In the parallax measurement activity, what should the measuring student do at the start of the baseline?

• Turn the straw of the parallax measuring tool to 45°.

• Turn the straw of the parallax measuring tool to 90°.

• Lay down a measuring tape parallel to the baseline.

• Stand directly in front of the target student.