Chapter 3

In 1054 CE, the Chinese recorded a very interesting and powerful cosmic event. What was this event?

What did Eratosthenes measure very accurately?

Who were the two great authorities of Greek astronomy?

Whose writings became so famous that he was known throughout the Middle East simply as “The Philosopher”?

Which of the following statements reflects beliefs that were almost universally held in pre-Copernican astronomy?

In what circumstances is retrograde motion observable?

You are observing the night sky from Mars. In what circumstances is retrograde motion observable?

What is the term for the apparent westward motion of a planet in the sky compared to the background stars (as viewed from the Earth) when observed on successive nights?

What is parallax?

Why did ancient astronomers believe that the Earth did not move?

In Ptolemy’s view of the universe, what is at the centre of a planet’s epicycle?

Which of the following astronomers described the universe in a way that matches the diagram?

What was the greatest inaccuracy in Copernicus’s model of the solar system?

Which of the following objects cannot transit (i.e. pass in front of) the Sun, as seen from Jupiter?

What was Tycho Brahe’s greatest contribution to astronomy?

What two numbers tell us the size and shape of an ellipse

The orbit of planet A has an eccentricity of 0.5 and the orbit of planet B has an eccentricity of 0.01. What can be said about the shape of the orbits of these two planets?

Which of the following masses exert higher gravitational force on each other?

Which of the following masses exert smaller gravitational force on each other?

Which of the following masses exerts the largest gravitational force on mass M?

A hypothetical solar system has planets evenly spaced in circular orbits from the sun in the following distances and with the following masses, that they are given in terms with the mass of Jupiter MJ. Which of the following planets exerts the larger gravitational force of the star.

Given its orbital period of 76 years, what is the average distance of Comet Halley from the Sun?

An object has been located orbiting the Sun at a distance of 65 AU. What is the approximate orbital period of this object?

On average, Saturn is 10 AU from the Sun. What is the approximate orbital period of Saturn?

The orbit of the planet Jupiter is an ellipse with the Sun at one focus. What is located at the other focus?

The orbit of the Moon is an ellipse with the Earth at one focus. What is located at the other focus?

A comet is found in a highly elliptical orbit with a semi-major axis equal to one astronomical unit (AU). According to Kepler’s third law of planetary motion, what would the sidereal period of this comet be?

At perihelion the gravitational force of the sun exerted on the Earth is the following equation. What is the force exerted on the sun by the Earth?

At which position (A, B, C) is the gravitational force of the Earth on the spaceship (green capsule) going to the Moon is the greatest?

An object moves in a straight line at a constant speed. Which number of forces could not act on the object?

What does the orbital velocity of an object with respect to the distance does?

Would your mass and weight change if you went to the Moon?

At which lunar phase(s) are tides at their lowest?

If Mars rises approximately the same time as a particular star. If Mars is in normal prograde motion at what time Mars will rise next night?

A planet orbits a planet in a circular orbit. How many forces are acting on the planet?