Astronomy: The Universe (Unit 5)

Question 1

True or False: The phenomenon, known as the Doppler effect, relates to how sound and light travel in waves

Answer 1

True

Question 2

What is the difference between sound wave compressions and rarefied sound waves? How does distance influence sound?

Answer 2

A vibrating object on Earth, like the speaker in a siren, generates waves that include alternating regions where the waves are closer together (compressed) and where they are farther apart (rarefied). Sound wave compressions are closer together (more frequent) when the source of the sound is traveling toward the observer. Sounds with higher frequency have higher pitch. Waves are farther and farther apart as the source of the sound travels away from the observer. They have lower pitch.

Question 3

Doppler Effect Definition

Answer 3

An increase or decrease in the frequency of waves relative to the observer, due to motion of the wave source

Question 4

How is the Doppler Effect identified in stars?

Answer 4

Other waves types also show the Doppler Effect. Stars produce light—and light, like sound, travels in waves. Because stars can be moving toward or away from Earth, light waves can compress or spread apart relative to an observer

Question 5

How do stars exhibit the Doppler Effect?

Answer 5

In stars, vibrating plasma particles, which are charged, generate waves in electromagnetic fields. Because the stars move relative to Earth, the appearance of this light from the stars is altered by the Doppler Effect. When a star is approaching Earth, its light wave frequencies increase. This causes the lines within the light spectrum of the star to shift toward the blue end of the electromagnetic spectrum. When a star is moving away from Earth, its light wave frequencies decrease, which causes the lines within the light spectrum of the star to shift toward the red end of the electromagnetic spectrum. Scientists observe this redshift and blueshift in many stars they can see with powerful telescopes

Question 6

Redshift Definition

Answer 6

The change to lower frequencies in the light coming from distant celestial objects moving away from the observer

Question 7

Blueshift Definition

Answer 7

The change to higher frequencies in the light coming from distant celestial objects moving toward the observer

Question 8

What did Edwin Hubble discover about redshift?

Answer 8

American astronomer, Edwin Hubble, identified a pattern in the redshift of stars and galaxies throughout the universe. In 1929, he observed that nearly all galaxies exhibit redshift. Hubble explained that this pattern is due to an expanding universe

Question 9

What are Redshift and Blueshift measured by?

Answer 9

Emission spectra

Question 10

How does Redshift and Blueshift change the spectrum of a luminous object?

Answer 10

When light frequencies coming from a star, galaxy, or other luminous object change due to the Doppler effect, one or more lines in the spectrum are shifted toward one end of the electromagnetic spectrum. For example, if redshift occurs, one or more lines will have longer wavelengths (lower frequencies). They will be shifted toward the red end of the spectrum. The shift is apparent when comparing the expected light spectrum for the space’s object (according to its composition) with the actual spectrum

Question 11

True or False: The Coma Super Galaxy Cluster is one of the densest collections of galaxies in the known universe

Answer 11

True

Question 12

Big Bang Definition

Answer 12

Theory that says the universe began with a massive explosion of very dense matter

Question 13

How have telescopes contributed to our understanding of galaxies and their part in the universe?

Answer 13

As telescopes have gotten bigger and more precise, astronomers have been able to see galaxies in deep space. The light coming from the galaxies takes millions of years to travel to Earth. This means scientists are looking at the galaxies as they appeared long ago. The farther back in time we can look, the more we learn about conditions in the universe when it was young. The galaxies in the Coma Super Galaxy Cluster are 300 million light years away from Earth

Question 14

When does redshift due to universe expansion show consistently?

Answer 14

Redshift due to universe expansion does not show consistently until space objects are tens of millions of light years away. A light year is nearly six trillion miles. When close to Earth, spectra changes reveal the motion of galaxies due to their particular situation, which scientists refer to as the galaxy’s “peculiar motion”. Some galaxies are in orbit around each other, for example. Gravity is pulling others together

Question 15

What does the peculiar motion of the Andromeda Galaxy result in?

Answer 15

The Andromeda Galaxy is only two and one-half million lights years away. Its peculiar motion causes light captured from the galaxy to show a slight blueshift. It is moving toward Earth at a speed of 130 km per second

Question 16

Example of Frames of Reference

Answer 16

Observations can be different if they are made from frames of reference that are moving relative to each other. For this reason, scientists often explain a reference frame for observation of light emitted from space objects. For example, a person on Earth will observe the light coming from the sun as being a consistent frequency. From the frame of reference of another galaxy, however, light coming from the sun and other stars in the Milky Way Galaxy probably will show a decrease in frequency, resulting in a redshift. This change occurs because the Milky Way Galaxy is a distant object, and the two galaxies probably are moving away from each other as the universe expands.

Question 17

What type of energy do nuclear power plants supply? What type of energy does nuclear fusion supply? For what?

Answer 17

Nuclear power plants convert the energy released by nuclear fission into electrical energy that powers homes and buildings. At the end of 2018, there were 60 nuclear power plants supplying about 20% of the energy used in the U.S.A. In contrast, nuclear fusion provides the energy that fuels the sun and stars

Question 18

How does the process of nuclear fission work?

Answer 18

Nuclear fission takes place in the nuclei of atoms. It occurs when a larger atom splits into two or more smaller ones. Nuclear fission starts when a neutron slams into a larger atom. As a result of the collision, the nucleus of the larger atom receives additional energy and is raised to a higher energy state. Physicists call this excitation. The excited nucleus splits into two smaller atoms, releasing a huge amount of energy in the process. When the nucleus of an atom splits, it can release some neutrons, which slam into other atoms, setting up a chain of fission reactions

Question 19

Nuclear fission Definition

Answer 19

Nuclear reaction that occurs when a larger atom splits into two or more smaller atoms

Question 20

How does nuclear fission work in the context of a nuclear power plant?

Answer 20

In the context of a nuclear power plant, fission is initiated in the nucleus of atoms in elements such as uranium or plutonium (radioactive). The energy released by nuclear fission is used to heat water until it changes to steam. The steam is used to turn turbines that generate electricity

Question 21

What is the cycle of nuclear fission in power plants?

Answer 21

During nuclear fission in power plants, uranium is kept in a nuclear reactor, and the energy released from splitting the atoms is used to heat water until it changes to steam. The steam turns the blades of a turbine. As the blades turn, they generate electricity. Water from a cooling tower is used to cool the steam until it changes back into water. The cooled water is run back into the system and reheated to produce steam once again

Question 22

Nuclear fusion Definition

Answer 22

Nuclear reaction that occurs when two atoms fuse to form one, heavier atom

Question 23

True or False: Nuclear Fission is 1 million times greater than other energy sources

Answer 23

True

Question 24

True or False: Nuclear fission is a controlled reaction and nuclear fusion is not

Answer 24

True

Question 25

True or False: nuclear fission is a controlled reaction and Nuclear fusion is not

Answer 25

True

Question 26

True or False: it has taken astronomers and other scientists decades to figure out how old the universe is

Answer 26

True

Question 27

What does the Big Bang theory suggest about the universe’s age?

Answer 27

The Big Bang Theory suggest that the universe was born approximately 12.5 to 13.8 billion years ago and has been changing ever since

Question 28

What does the Big Bang theory state?

Answer 28

The Big Bang theory proposes that the universe began with a sudden explosion from a hot, dense point. The universe cooled very quickly after this event, which allowed key elements to form. It has been expanding for billions of years

Question 29

What does the Big Bang theory state?

Answer 29

The Big Bang theory proposes that the universe began with a sudden explosion from a hot, dense point. The universe cooled very quickly after this event, which allowed key elements to form. It has been expanding for billions of years

Question 30

When did the first piece of evidence for the Big Bang theory appear? How long did it take the scientists to accept it?

Answer 30

Evidence for the Big Bang Theory first appeared in the 1920s, but scientists found the data hard to believe. Only when modern telescopes, space probes, and computers produced supporting evidence did scientists finally accept the theory. Such high-tech equipment has helped astronomers look back through time and space to explore the very beginning of the universe. Scientists continue to find evidence from different fields of study that supports the Big Bang theory

Question 31

Big Bang Theory Definition

Answer 31

An explanation of how the universe began from a small point and expanded

Question 32

Where do scientists believe the universe started from?

Answer 32

Scientists believe the universe started from a super-hot, dense point called a singularity. They do not know where the singularity came from, but once it appeared, it expanded rapidly. The “bang” in the Big Bang theory suggests the universe exploded into existence, but it did not. It inflated like a balloon and has been expanding ever since

Question 33

What is evidence for the Big Bang theory?

Answer 33

1) light from distant galaxies is shifted into the longer, redder wavelengths, or redshift—proof that the universe is expanding. 2) as the universe cooled from its super-hot state, the intense light band radiation ended up in the microwave range and spread evenly throughout the universe. This is called “cosmic background radiation”, and it has been detected by microwave telescopes. This is solid evidence of the “big inflation”. 3) the Big Bang theory predicts that the early universe was made up of roughly three-fourths hydrogen and one-fourth helium, with a bit of other matter. If that were true, then the modern universe would be composed of the same kind of matter in those same proportions. Guess what? Matter in our universe is just about three-fourths hydrogen, one-fourth helium, and little bit of “other”

Question 34

What are the current, three pieces of evidence that support universe expansion?

Answer 34

There are currently three pieces of evidence for universe expansion, based on scientist’s observations, that support the Big Bang theory: 1) galaxies are moving away from each other 2) cosmic microwave background radiation (CMB) appears uniformly across the universe 3) universal temperature has changed over time

Question 35

True or False: the Big Bang theory was an outward force on space and objects in that space

Answer 35

True

Question 36

How did Edwin Hubble contribute to the evidence supporting the universe’s expansion?

Answer 36

Edwin Hubble delivered the first piece of evidence: that galaxies are moving away from each other, other objects weighing the universe, and space. Hubble’s law also states that galaxies farther away from us are moving more rapidly

Question 37

What was the initial temperature of the universe? What is the temperature now?

Answer 37

The initial temperature was approximately 10 billion degrees Fahrenheit, and the current temperature is negative 455 degrees Fahrenheit. The hypothesis is that the temperature decreases as the cosmos disperses

Question 38

What evidence was added to the support of the universe’s expansion in 1970?

Answer 38

More evidence was revealed in 1970. It was assumed that after a grand explosion, there would have been an enormous amount of radio emissions. This was missing until 2 astronomers stumbled across radio emissions coming from every direction in the sky

Question 39

Who is the Hubble Telescope named after?

Answer 39

The Hubble Space Telescope orbits Earth, giving it a sharp, crisp view of objects in the galaxy. It is named after Edwin Hubble, who was the first to prove that the universe is expanding. He observed through a powerful 100-inch telescope that the Milky Way was not the only galaxy. In his observations of other galaxies, he found they were moving away from each other by studying the redshift of light from distant galaxies

Question 40

True or False: Astronomers constantly look for patterns

Answer 40

True

Question 41

How do we detect CMB?

Answer 41

CMB exists as weak background radiation spread uniformly across the universe. Technology allows scientists to detect this radiation as microwave photons. These photons pick up added energy as they pass through galaxy clusters with high energy electrons. Telescopes can detect this added energy, which helps astronomers on Earth map galaxy clusters and explore other properties of the universe

Question 42

Cosmic Background Radiation Definition

Answer 42

Electromagnetic radiation that is a remnant of the Big Bang

Question 43

Photon Definition

Answer 43

Particle of electromagnetic radiation

Question 44

How does the temperature of the CMB relate to the temperature of the universe?

Answer 44

Many astronomers consider the temperature of the universe to be the temperature of CMB, which is currently 2.735 degrees above absolute zero

Question 45

How has CMB helped astronomers see into the past?

Answer 45

CMB radiation gives astronomers an idea of what the universe was like when it was around 400,000 years old. Astronomers have found that the universal temperature is dropping as the universe expands, just as the Big Bang theory predicts it will. They gathered this evidence by studying the temperature of CMB at different distances across the universe

Question 46

True or False: CMB has appeared to be uniform throughout the universe, but thanks to modern technology, we know now that the temperature has tiny fluctuations that we could not see before

Answer 46

True

Question 47

About how much of the universe is dark matter?

Answer 47

1/4

Question 48

Baryonic matter Definition

Answer 48

Matter that is made of atoms

Question 49

Dark matter Definition

Answer 49

Matter that humans cannot see

Question 50

How did Fritz Zwicky influence the idea of dark matter?

Answer 50

In 1933, Swiss astronomer and physicist Fritz Zwicky was studying the Coma Cluster of galaxies. He observed that the galaxies rotate around the cluster’s center faster than predicted. Zwicky found that the sum of masses of all galaxies in the cluster was not enough to posses the gravity needed to keep the cluster from flying apart. He hypothesized that there was something with mass keeping the Coma Cluster intact—something he could not see. He named the “something” dark matter

Question 51

How did Vera Rubin influence the idea of dark matter?

Answer 51

In the 1970s, American astronomer Vera Rubin noticed a similar phenomenon as Zwicky. Rubin was studying spiral galaxies, including the Andromeda Galaxy. She observed that stars at the edges of the galaxies orbited faster than they should, based on their mass. Like Zwicky, Rubin decided there must be something with mass she could not see. She hypothesized that the missing mass was in the form of a halo of dark matter around the edges of the galaxy

Question 52

How can an astronomer formulate the masses of galaxies, according to Fritz Zwicky?

Answer 52

In the early 1930s, Fritz Zwicky discovered that galaxies in clusters orbit around each other. An astronomer could formulate the masses of galaxies by the speed of the orbits of the surrounding galaxies

Question 53

True or False: Zwicky’s theory of black matter was not touched until Vera Rubin verified it

Answer 53

True

Question 54

What do most scientists agree on concerning dark matter?

Answer 54

Most scientists concur that dark matter controls where ordinary matter collects to form stars, planets, galaxies, and life

Question 55

How did astronomers know dark matter is there?

Answer 55

Although black matter does not react with electromagnetic radiation, they know it is there because of its gravitational effects on celestial objects such as galaxies

Question 56

What does Baryonic matter interact with?

Answer 56

Electromagnetic radiation and other baryonic matter

Question 57

Does dark matter interact with baryonic matter?

Answer 57

Dark matter does not interact with baryonic matter, but it’s gravity puts constraints on where and how baryonic matter gathers together. Galaxies and galaxy clusters, for instance, would break apart if not for the mass (and thus gravity) of dark matter holding them together

Question 58

What is gravitational lensing?

Answer 58

People looking at galaxies through telescopes sometimes see arcs or rings of light. This phenomenon, called gravitational lensing, is one way to indirectly observe dark matter. The arcs of light are actually light from a distant source (usually a galaxy) that is being distorted and magnified by the gravity of the dark matter surrounding the galaxy the person is observing

Question 59

What are the people at the European Organization for Nuclear Research (CERN) doing? What is the Large Hadron Collider (LHC)?

Answer 59

Thus far, scientists have been unable to observe dark matter directly. However, the physicists at the European Organization for Nuclear Research (CERN) are working on a solution to that problem. CERN boasts the Large Hadron Collider (LHC), the largest and most powerful particle accelerator in the world. Scientists are using the LHC to try to produce particles of dark matter. The LHC, which is a ring of superconducting magnets, is in a circular tunnel on the border between France and Switzerland. Inside the 27 km (17 mi) long tunnel, two high-energy beams of particles collide, forming new particles. Because the particles are so small, it’s very difficult to make them collide. The LHC is most likely capable of producing dark matter, but the particles will be too light for the LHC’s detectors to sense them. To address this issue, CERN built the Forward Search Experiment (FASER), an instrument that identifies the decay products of light and weakly interacting particles. FASER is expected to be fully operational in 2021. Dark matter may contain particles that are companions to elementary particles called quarks and leptons, from which matter made of protons, neutrons, and electrons is composed. Scientists will continue to use the LHC to search for these and other particles.

Question 60

What are some theories of the nature of dark matter?

Answer 60

One idea is that dark matter might be composed of large numbers of black holes. Another idea is that dark matter is made of as-yet-undiscovered elementary particles that scientists call “weakly interacting massive particles” (WIMPs). Scientists think WIMPs might have been produced not long after the Big Bang. They hypothesize that WIMPs are electrically neutral and that they interact with the weak force and gravity. Other scientists speculate that dark matter may be made of baryonic matter contained in objects called “massive compact halo objects” (MACHOs). These objects include brown dwarfs, objects with a mass somewhere between the biggest planets and the smallest stars. They form from clouds of gas and dust, as stars do. However, brown dwarfs do not have enough mass to conduct nuclear fusion, so they cannot produce their own light. The light they give off is caused by residual heat from the gas cloud that formed them. Because their luminosity is so low, it is difficult for scientists to detect brown dwarfs with telescopes. Scientists think there may be a connection between WIMPs and gamma rays.

Question 61

How are gamma rays and WIMPs connected?

Answer 61

Gamma rays have the shortest wavelengths of any type of radiation. They also have more energy than any other type of radiation. High-energy events and objects, such as supernovas, pulsars, and neutron stars, produce gamma rays. They are not visible to humans. Because their wavelengths are so short, specialized instruments are required to detect gamma rays. Some scientists think that as-yet-undiscovered elementary particles called weakly interacting massive particles (WIMPs) might make up dark matter. They hypothesize that when WIMPs undergo a certain type of reaction,
they may give off gamma rays. Because of this possible connection, scientists are studying gamma rays
more closely.

Question 62

What is driving the expansion of the universe today?

Answer 62

An unidentified energy, known as dark energy

Question 63

How do computer models help us visualize dark matter?

Answer 63

Scientists analyze the gravitational influence of dark matter on visible objects to determine its location and structure. Computer models help scientists to visualize the web-like tendrils of dark matter between stars and galaxies

Question 64

What is the structure of galaxies most likely a result of?

Answer 64

The structure of galaxies is likely the result of the interactions between dark matter and baryonic matter. Galaxies form as a result of differences of density in space. The earliest galaxies in the universe formed shortly after the Big Bang. However, the matter in the universe was still moving too fast to exert enough gravity for galaxies to form. So, how did those galaxies form? Scientists theorize that shortly after the Big Bang, the universe was almost perfectly uniform, but with some clumps of ordinary matter and dark matter. They theorize that pancake-shaped and rope-like structures of dark matter were present, and it was these structures that seeded the formation of the early galaxies

Question 65

How much of the Milky Way’s mass is surrounded by a large halo of dark matter?

Answer 65

90%

Question 66

How did Type 1A supernovas help scientists see that the universe is expanding?

Answer 66

Scientists hypothesized that the universe would expand outward after the Big Bang until it eventually stopped. At some point, they thought, gravity would cause the universe to begin a collapse inward. Scientists tried to find evidence for this idea by observing the distance to Type 1A supernovas, which have a standard brightness. They discovered that the supernovae were much farther away than expected. Through this measurement they learned that the universe is not contracting; rather it is expanding. What’s more, the rate of expansion is accelerating

Question 67

Accelerating Definition

Answer 67

Increasing the speed of motion

Question 68

When did the expansion of the universe begin?

Answer 68

The expansion of the universe began a few billion years after the Big Bang. As the universe began to expand, dark energy began to dominate over the force of gravity, speeding the expansion. The process of acceleration requires an enormous source of energy, although scientists do not know what the source of this dark energy might be

Question 69

Dark Energy Definition

Answer 69

Energy that humans cannot observe directly

Question 70

How do we know that dark matter makes up about 70% of the mass in the universe?

Answer 70

Scientists have estimated the amount of energy that would be required to pull apart the universe. The energy can be converted to mass through Einstein’s mass-energy equivalence. The mass-energy relationship gives the mass equivalent of dark energy. Consider Einstein’s mass-energy equation: E = mc^2. The letter “c” denotes the speed of light. To more full appreciate the amount of dark energy in the universe, consider the value of “c” in the equation to compare the equivalence of energy and mass: you can see how a small amount of mass is equivalent to a phenomenally large amount of energy. Using this equivalence, it is known that dark energy makes up 70% of the mass of the universe.

Question 71

Why is known the total amount of mass in the universe important?

Answer 71

The total amount of mass in the universe is important to scientists in part because it is used to find the total density of matter. Scientist use this density to model the geometry of the universe. It was once thought that the low density of the universe would lead to a sphere-shaped universe, which would eventually collapse. This was wrong.