Ch. 5 & Ch. 6 Tests

What percentage of the Earth's surface is covered by water?

71%

What does the long, flowing tail of a comet tell us about the solid body of the comet?

It is composed of ice.

Which of the following scenarios best describes the evolution of the surface of the Earth under the action of plate tectonics?

Oceanic plates form and move around slowly and are eventually subducted back into the mantle under the continental plates that remain floating on top.

CO2 is a minor constituent in our atmosphere, with an abundance of less than 0.05% of the gases in this atmosphere. Why, then, is an increase in this gas considered to be important in the continued viability of life upon Earth?

Small increases in CO2 will prevent more IR radiation from escaping from Earth, thereby leading to a dangerous warming of the Earth.

What is happening to the length of a day on the Earth, as a result of the gravitational pull of the Moon?

The Earth is gradually spinning more slowly, with the result that our day is gradually getting longer.

What have we learned about the Moon's magnetic field?

The Moon has no global magnetic field at the present time, but there is a relatively strong magnetic field over some areas of the Moon's surface.

What has happened to the Moon's distance from the Earth over the last four billion years?

The Moon's distance from the Earth has gradually increased.

How does the Moon's iron-rich core compare to that of the Earth?

The Moon's iron-rich core is much smaller than the Earth's. The Moon's iron-rich core takes up less than 5% of the Moon's mass, whereas the Earth's core takes up more than 30% of the Earth's mass.

How does the gravitational microlensing technique work for discovering planets around some stars?

The light from a distant star is focused on the Earth, making it appear brighter, when a nearer star passes in front of it as seen from the Earth. If the nearer star has a planet, then the planet also focuses the light, causing a short-duration secondary peak in brightness.

A gas giant planet has been found in orbit around the star HD 209458. How have astronomers been able to study the atmosphere of this planet?

The planet frequently passes in front of the star as seen from the Earth, and its atmosphere absorbs some of the star's light at wavelengths characteristic of hydrogen and other elements in the planet's atmosphere.

The eight major planets of our solar system can be classified on the basis of their properties and orbits in which of the following ways?

They divide naturally into two main groups.

Do we have any direct evidence that stars can swallow their planets?

Yes. The presence of a rare element in one star's spectrum indicates that stars can swallow their planets.

The magnetosphere is

a cavity within the high-speed solar wind, caused by the Earth's magnetic field.

Our planetary system is believed to have originated in a disk of gas and dust that surrounded the Sun shortly after the Sun formed. Such disks around young stars are

an observational fact, having been observed around other stars in our Galaxy.

The most common type of rock on the lunar surface is

anorthosite.

An object less than 1000 km across, composed of rock and iron and orbiting closer to the Sun than the planet Jupiter, would be called a(n)

asteroid

The majority of earthquakes occur

at the boundaries of tectonic plates.

Where in the solar system would you find Kuiper Belt objects?

beyond the orbit of Neptune, extending perhaps as far as 500AU from the Sun

Which components of the present solar system have probably remained essentially unchanged since the solar system was formed and can therefore provide valuable clues to the manner of this formation?

comets, asteroids and meteoritic material

One curious fact about the overall surface of the Moon is that

compared to the many maria on the Earth-facing side, there is only one moderate mare and a few very small ones on the far side of the Moon.

There are three processes in nature for transferring heat energy from one place to another: conduction, convection, and radiation. Which of these processes is dominant in the Earth's interior?

convection, the bulk motion of hotter material within cooler material

The origin of the Moon in the early history of the solar system appears to have been the

ejection of debris from a collision of a planet-sized object with the Earth, and subsequent coalescence into the Moon.

The material in the innermost core of the Earth is

hot and solid

Suppose a small object is discovered in orbit around the Sun, with a mass of 1 million kg and a volume of 1000 m3. This object is most probably made almost entirely of

ice

A fundamental process that shaped the Moon's surface was

impacts of asteroidal debris onto a hard, immobile crust.

The most abundant elements in the universe are hydrogen and helium, but there are also small but significant amounts of heavier elements in stars and planets and in our own bodies. Where did these heavy elements originate?

in nuclear fusion deep in the interiors of stars

The reason that the Earth has a core of almost pure iron is that

iron is the most abundant heavy element, and it sank while the Earth was molten, by chemical differentiation.

Which of the following groups of planets have average densities close to that of water, that is, about 1000 kg/m3?

large outer planets because of their composition, mainly H and He

What major fact common to the giant planets leads to the conclusion that they are composed mainly of light elements such as hydrogen and helium?

low average density

What method has been used in the successful search for planets around stars other than the Sun?

measurement of the "wobble" of a star, caused by the orbital motion of the planet, detected either by accurate positional measurement of the star or by wavelength shifts in the star's spectrum

The age of the solar system has been measured by radioactive dating. Which of the following objects gives the most precise value for this age?

oldest meteorites

What is the process by which the terrestrial planets are believed to have formed?

process of accretion, in which dust particles stick together to form asteroid-like objects and then collide to eventually form the planets

What is a proplyd?

protoplanetary disk

The ages of lunar rocks brought back to Earth by astronauts and robotic spacecraft have been determined by measuring the

relative concentrations of radioactive elements.

What process heated the early solar nebula as it slowly condensed toward a central protosun?

release of heat from the kinetic energy in collisions of particles as they fall toward the center of the nebula

Which of the following sources of heat has NOT contributed significantly to heating the interior of the Earth?

solar heating

The reason the inner planets are mostly rock and iron and the outer planets are mostly lighter material, such as hydrogen and ices, is that

the inner solar system was warm enough that the lighter material vaporized (or never solidified), leaving rock and iron to form the inner planets.

Most of the mountains on the Moon are

the raised rims of ancient impact craters and maria.

What is the lunar regolith?

the surface layer, consisting entirely of fine powder and rock fragments

The ozone molecule, important in absorbing harmful solar UV radiation before it reaches the Earth's surface, consists of

three oxygen atoms.