Chapter 8 Reading Quiz

Suppose you start with 1 kilogram of a radioactive substance that has a half-life of 10 years. Which of the following statements will be true after 20 years pass? A. You'll have 0.25 kilogram of the radioactive substance remaining. B. You'll have 0.5 kilogram of the radioactive substance remaining. C. All the material will have completely decayed. D. You'll have 0.75 kilogram of the radioactive substance remaining.

You'll have 0.25 kilogram of the radioactive substance remaining. -After 10 years, only half of the original kilogram will remain. After 20 years half of that half, or one-quarter of the original amount, will remain.

According to modern scientific dating techniques, approximately how old is the solar system? A. 14 billion years B. 4.5 billion years C. 10,000 years D. 4.5 million years

4.5 billion years -This age has been well-verified by numerous independent measurements.

According to modern science, what was the approximate chemical composition of the solar nebula? A. 98% hydrogen, 2% helium B. 98% hydrogen and helium, 2% everything else C. Roughly equal proportions of hydrogen, helium, water, and methane. D. 50% hydrogen and helium, 50% everything else

98% hydrogen and helium, 2% everything else -The Sun still has this basic composition today.

According to our basic scenario of solar system formation, why do the jovian planets have numerous large moons? A. The large moons of the jovian planets originally formed in the inner solar system and these moons then migrated out to join up with the jovian planets. B. Because of their strong gravity, the jovian planets were able to capture numerous asteroids that happened to be passing nearby, and these became the major moons of the jovian planets. C. As the growing jovian planets captured gas from the solar nebula, the gas formed swirling disks around them, and moons formed from condensation accretion within these disks. D. The many moons of the jovian planets remains one of the unexplained mysteries of the formation of our solar system.

As the growing jovian planets captured gas from the solar nebula, the gas formed swirling disks around them, and moons formed from condensation accretion within these disks. -That is, the formation of large moons around jovian planets was much like a smaller version of the formation of planets around the Sun.

According to our present theory of solar system formation, why were solid planetesimals able to grow larger in the outer solar system than in the inner solar system? A. Because the Sun's gravity was stronger in the outer solar system, allowing more solid material to collect. B. Because gas in the outer solar system contained a larger proportion of rock, metal, and hydrogen compounds than the gas in the inner solar system. C. Because only metal and rock could condense in the inner solar system, while ice also condensed in the outer solar system. D. Because only the outer planets captured hydrogen and helium gas from the solar nebula.

Because only metal and rock could condense in the inner solar system, while ice also condensed in the outer solar system. -Hydrogen compounds were much more abundant than rock and metal, so their condensation into ice meant much more solid material was available to accrete into planetesimals.

According to our theory of solar system formation, what three major changes occurred in the solar nebula as it shrank in size? A. Its gas clumped up to form the terrestrial planets, nuclear fusion produced heavy elements to make the jovian planets, and central temperatures rose to more than a trillion Kelvin. B. Its mass, temperature, and density all increased. C. It gained energy, it gained angular momentum, and it flattened into a disk. D. It got hotter, its rate of rotation increased, and it flattened into a disk.

It got hotter, its rate of rotation increased, and it flattened into a disk. -Heating is a consequence of conservation of energy, faster rotation is a consequence of conservation of angular momentum, and flattening is a consequence of collisions between objects in a spinning system.

What do we mean by the frost line when we discuss the formation of planets in the solar nebula? A. It is a circle at a particular distance from the Sun, beyond which the temperature was low enough for ices to condense. B. It marks the special distance from the Sun at which hydrogen compounds become abundant; closer to the Sun, there are no hydrogen compounds. C. It is the altitude in a planet's atmosphere at which snow can form. D. It is another way of stating the temperature at which water freezes into ice.

It is a circle at a particular distance from the Sun, beyond which the temperature was low enough for ices to condense. -Therefore planetesimals were built only of metal and rock within the frost line, but beyond the frost line they included ices along with metal and rock.

According to our theory of solar system formation, what are asteroids and comets? A. The shattered remains of collisions between planets B. Chunks of rock or ice that condensed after the planets and moons finished forming C. Leftover planetesimals that never accreted into planets D. Chunks of rock or ice that were expelled from planets by volcanoes

Leftover planetesimals that never accreted into planets -Asteroids are the rocky leftovers of the inner solar system and comets are the icy leftovers of the outer solar system.

What is the giant impact hypothesis for the origin of the Moon? A. The Moon formed when two gigantic asteroids collided with one another. B. The Moon originally was about the same size as Earth, but a giant impact blasted most of it away so that it ended up much smaller than Earth. C. The Moon formed from material blasted out of the Earth's mantle and crust by the impact of a Mars-size object. D. The Moon formed just like the Earth, from accretion in the solar nebula.

The Moon formed from material blasted out of the Earth's mantle and crust by the impact of a Mars-size object. -This is now considered the most likely explanation for the origin of our Moon.

What do we mean by the period of heavy bombardment in the context of the history of our solar system? A. The first few hundred million years after the planets formed, which is when most impact craters were formed. B. The time during which heavy elements condensed into rock and metal in the solar nebula. C. The period about 65 million years ago when an impact is thought to have led to the extinction of the dinosaurs. D. The time before planetesimals finished accreting into planets, during which many growing planetesimals must have shattered in collisions.

The first few hundred million years after the planets formed, which is when most impact craters were formed. -The heavy bombardment ended once most of the objects that could create impacts had either crashed into a planet or attained a stable orbit around the Sun.

What do we mean by accretion in the context of planet formation? A. The solidification of ices, rocks, and metal from the gas of the solar nebular B. The growth of planetesimals from smaller solid particles that collided and stuck together C. The formation of moons around planets D. The growth of the Sun as the density of gas increased in the center of the solar nebula

The growth of planetesimals from smaller solid particles that collided and stuck together -At first, accretion probably arose from electrostatic attractions, but as planetesimals grew larger their gravity allowed them to accrete more efficiently (as long as they didn't suffer collisions with similar-size planetesimals).

The terrestrial planets are made almost entirely of elements heavier than hydrogen and helium. According to modern science, where did these elements come from? A. They were produced by stars that lived and died before our solar system was born. B. They were produced by gravity in the solar nebula as it collapsed. C. They were made by chemical reactions in interstellar gas. D. They have been present in the universe since its birth.

They were produced by stars that lived and died before our solar system was born. -That is why we say that we and our planet are made from "star stuff."

According to our present theory of solar system formation, which of the following lists the major ingredients of the solar nebula in order from the most abundant to the least abundant? A. hydrogen and helium gas; hydrogen compounds; rock; metal. B. hydrogen, water, methane, helium C. hydrogen and helium gas; rock; metal; hydrogen compounds D. hydrogen compounds; hydrogen and helium gas; metal; rock

hydrogen and helium gas; hydrogen compounds; rock; metal. -Hydrogen and helium gas were the most abundant by far, comprising about 98% of the solar nebula.

Which of the following types of material can condense into what we call ice at low temperatures? A. hydrogen compounds B. hydrogen and helium C. metal D. rock

hydrogen compounds -Hydrogen compounds such as water, ammonia, and methane are gaseous at high temperature but condense into ice at low temperature.

According to our theory of solar system formation, where did the comets originally form? A. far beyond the orbit of Pluto B. in the inner solar system C. in the outer solar system beyond the frost line D. in the asteroid belt.

in the outer solar system beyond the frost line -That is why they are icy leftovers from planet formation.

In essence, the nebular theory holds that _________. A. nebulae are clouds of gas and dust in space B. the planets each formed from the collapse of its own separate nebula C. The nebular theory is a discarded idea that imagined planets forming as a result of a near-collision between our Sun and another star. D. our solar system formed from the collapse of an interstellar cloud of gas and dust

our solar system formed from the collapse of an interstellar cloud of gas and dust -This cloud of gas and dust that gave birth to our solar system is called the solar nebula.