life in the universe

chapter three

How do we know that the elements that make up life exist throughout the universe?

We detect their presence spectroscopically.

What do we mean when we say that we and our planet are made from "star stuff"?

Most of the elements that make up Earth and life were manufactured by stars.

Which best describes why it seems plausible that we live in universe full of life?

Earth's circumstances seem ordinary in the scheme of the universe.

Which of the following is most directly associated with the Big Bang?

The beginning of the expansion of the universe.

According to current scientific estimates, when did the Big Bang occur?

about 14 billion years ago

On the cosmic calendar, which compresses the history of the universe into a single year, about when did our solar system form?

in early September

The word universe literally means "one story." By this literal definition, when did we first learn that we live in a "universe"?

when Newton recognized that the same physical laws apply both on Earth and in space

The Milky Way Galaxy is ________.

a giant collection of more than 100 billion stars

What is not a general difference between a planet and a star?

Planets are made of rock and stars are made of gas.

In what sense are we "star stuff"?

Nearly every atom from which we are made was once inside of a star.

best describes the structure of an atom?

A tiny nucleus, made of protons and neutrons, surrounded by a "cloud" of electrons that give the atom its physical size

What is not a major pattern of motion in the solar system?

Nearly all comets orbit the Sun in same direction and roughly the same plane.

When considering light as made up of individual "pieces," each characterized by a particular amount of energy, the pieces are called ________.

photons

The energy attributed to an object by virtue of its motion is known as ________.

kinetic energy

The discovery of exoplanets has provided strong validation for the nebular theory, but it also forced scientists to recognize that the theory was incomplete (as it stood before the exoplanet discoveries).Which idea below was added to the theory after the discovery that some massive planets orbit very close to their stars?

Planets can migrate inward or outward from the orbits on which they originally formed.

What most definitively rules out the possibility that planets form following close encounters between stars?

Many stars have planets.

In essence, the nebular theory holds that _________.

our solar system formed from the collapse of an interstellar cloud of gas and dust

From shortest to longest wavelength, which of the following correctly orders the different categories of electromagnetic radiation?

gamma rays, x-rays, ultraviolet, visible light, infrared, radio

Thermal radiation is defined as ________.

radiation with a spectrum whose shape depends only on the temperature of the emitting object

Terrestrial Planets are?

Mars, Venus, Mercury, Earth (M.M.E.V)

Jovian Planets are?

Uranus, Saturn, Jupiter, Neptune (U.S.J.N)

One of the key lessons from astronomy is that the elements of life are widespread in the universe. How is this fact relevant to the search for life in the universe?

It tells us that we can expect to find the chemical building blocks of life on many worlds.

A television advertisement claiming that a product "is light-years ahead of its time" does not make sense because ________.

it is using "light-years" to talk about time

Which of the following statements about nuclear fusion is not true?

It refers solely to the process of fusing hydrogen to make helium.

The fact that the elements of life were produced in stars suggests the following two things:

(1) These elements have become more common as the universe has grown older.

(2) These elements should be found in nearly all star systems.

When we say that the Universe is expanding, we mean that...

galaxies are, on average, becoming farther apart with time

The extent of the observable universe (that is, how far the observable horizon is located from us) is determined primarily by...

the age of the Universe

When we observe a galaxy that is 10 billion light-years away, we are seeing this galaxy as it...

was when the universe was about 4 billion years old

The term organic molecules generally refers to ________.

molecules containing carbon

In which case are the two atoms are isotopes of one another?

carbon-12 and carbon-14

If we imagine the history of the universe compressed into a one-year "cosmic calendar," dinosaurs became extinct ________.

yesterday morning

Characteristics of terrestrial planets.

Few moons, no rings, orbit close to the sun, rock and metal composition

Characteristics of Jovian planets

Orbit far from the sun, made mostly of hydrogen, helium, and hydrogen compounds, many moons, many rings.

Suppose you want to know the chemical composition of a distant star. Which piece of information is most useful to you?

The wavelengths of spectral lines in the star's spectrum

A rock held above the ground has potential energy. As the rock falls, this potential energy is converted to kinetic energy. Finally, the rock hits the ground and stays there. What has happened to the energy?

The energy goes to producing sound and to heating the ground, rock, and surrounding air.

Planetary systems discovered around other stars...

exhibit a range of different layouts, some being very similar to our solar system while others being very different

The close encounter model suggested that the planets of our solar system formed as a result of...

material being gravitationally pulled out of the Sun by another star

Close encounter model means..?

Planetary systems should be rare.

What is a key prediction of the nebular theory of planetary formation?

Planetary systems should be common.

What do we mean by accretion in the context of planet formation?

The growth of planetesimals from smaller solid particles that collided and stuck together

According to the nebular theory of solar system formation, what three major changes occurred in the solar nebula as it shrank in size?

It got hotter, its rate of rotation increased, and it flattened into a disk.

According to the nebular theory of solar system formation, which law best explains why the solar nebula spun faster as it shrank in size?

The law of conservation of angular momentum

best describes why we think the terrestrial planets formed in the inner solar system and the jovian planets formed in the outer solar system?

The terrestrial planets grew from "seeds" of metal and rock, while the jovian planets grew from seeds that also contained hydrogen compounds that condensed only in the cold outer solar system.

In what sense are telescopes like time machines?

They allow us to see distant objects as they were long in the past.

Because we live in an expanding universe, distant galaxies are farther away from us today than they were when the light we see from them started on its journey to us. So what do we mean when we say that a galaxy is 7 billion light-years away?

Its light has taken 7 billion years to reach us.

Suppose we observe a galaxy that is 13 billion light-years away. Which of the following can we conclude?

The galaxy formed before the universe was 1 billion years old.

How far would you have to walk to reach Alpha Centauri?

the distance across the United States (2500 miles)

In the Voyage model you have to walk the roughly 600-meter distance from the Sun to Pluto and if then you decide to keep going to find the nearest star besides the Sun. How far would you have to go?

Surprisingly, you would need to walk to California.

best describes what astronomers mean when they say that the universe is expanding?

The average distance between galaxies is increasing with time.

Based on what you've learned from the raisin cake analogy, which two properties of distant galaxies do astronomers have to measure to show that we live in an expanding universe?

their distances and speeds

Today, the evidence that we live in an expanding universe is extremely strong because astronomers have measured the motions of millions of galaxies. Nevertheless, in science, we must always remain open to the possibility that some future observation could call even our most strongly supported theories into question. Which of the following hypothetical observations would not be consistent with what we expect in an expanding universe

You discover an extremely distant galaxy that is moving toward us.

According to current scientific estimates, when did the Big Bang occur?

about 14 billion years ago

On the cosmic calendar, which compresses the history of the universe into a single year, about when did Earth form?

in early September

On the cosmic calendar, which compresses the history of the universe into a single year, about when did life arise on Earth?

in September

On the cosmic calendar, which compresses the history of the universe into a single year, about when did early humans first walk on Earth?

just a few hours before midnight on December 31

Red light has a _____ wavelength and a _____ frequency than does blue light.

longer, lower

X ray photons have a _____ wavelength, _____ frequency, and _____ energy than do ultraviolet photons.

shorter, higher, higher

If you have a telescope that is observing light with wavelengths of a few meters, you are observing __________.

radio waves

Suppose that you had "X-ray vision" that allowed you to see X rays. What would you notice when you looked at a friend standing near you that you could not notice with your visible light vision alone?

nothing

Most interstellar clouds are made mostly of hydrogen (because hydrogen is the most common element in the universe). Why are these clouds usually dominated by the color red?

Because the strongest visible emission lines from hydrogen are red.

Most continuous spectra are examples of what we also call thermal radiation spectra. Why do we call them "thermal" spectra?

Because the peak wavelength of the spectrum depends on the temperature of the object producing the spectrum.

For an object producing a thermal spectrum, a higher temperature causes the spectrum to have ___________.

a peak intensity located at shorter wavelength

Thermal radiation gets its name because __________.

its spectrum depends on the temperature of the object emitting it

Compared to a cold object, a hotter object of the same size emits most of its light at __________ wavelengths and emits _____ light overall.

shorter, more

Imagine being on the Moon and looking at the thermal radiation spectrum of Earth. How would it compare to the spectra shown on the graph in the video?

It would be very similar to the spectrum of the human.

Incandescent light bulbs emit thermal radiation because their filaments are heated to about 2500 Kelvin. LED light bulbs emit only at particular visible wavelengths. Why do incandescent bulbs require more energy to shine with the same amount of visible light as LED bulbs?

Incandescent bulbs emit most of their energy as infrared light.

Suppose that Mars had a higher surface temperature. How would its spectrum be different?

The peak in the infrared would be at shorter wavelength.

Why does Mars appear reddish in color?

It reflects most of the Sun's red light while absorbing most of its blue light.

We expect a scientific theory to be able to make predictions that can be tested. Which of the following is a prediction of the nebular theory that has been verified by observations?

Many stars should have planets.

The "giant impact hypothesis" refers to the idea that ___________.

our Moon formed when a Mars-size object collided with the young Earth.

What substances were found in the innermost regions (within about the inner 0.3 AU) of the solar system before planets began to form?

rocks, metals, hydrogen compounds, hydrogen, and helium, all in gaseous form

What substances existed as solid flakes within the innermost regions (within about the inner 0.3 AU) of the solar system before planets began to form?

none

Where would you expect terrestrial planets to form in the solar nebula?

anywhere between the innermost regions (within about the inner 0.3 AU) and the frost line

The jovian planets are thought to have formed as gravity drew hydrogen and helium gas around planetesimals made of __________.

rocks, metals, and ices