ASTR 101 Chapter 17 Hw

During the history of the universe, what important event occurred about 380,000 years after the Big Bang?

Light began to travel freely through the universe.

The__________ is the name we give to the moment when the expansion of the universe began.

Big Bang

Electroweak Era

3 forces operated: gravity, strong, electroweak

Planck Era

all 4 forces operated as one

The current temperature of the universe as a whole is

a few K

What is the earliest time in the universe that we can directly observe?

a few hundred thousand years after the Big Bang

The ____________ is our name for the photons we see that were first released when the universe was about 380,000 years old.

cosmic microwave background

A very short period of extremely rapid expansion, called_______, is thought to have occurred when the universe was about 10-38 second old.

inflation

Which of the following does inflation help to explain?

* - the uniformity of the cosmic microwave background* - the amount of helium in the universe - the temperature of the cosmic microwave background

Today, most scientists accept the Big Bang theory because its predictions agree so well with observations. But a scientific theory can always be revised or discarded if future observations do not agree with its predictions. Consider the following hypothetical future observations. Which one(s) would be inconsistent with the Big Bang theory?

- Astronomers discover distant protogalactic clouds with a helium abundance below 20%. - Over the next 10 years, the temperature of the cosmic microwave background falls to 1 K. - Careful studies of quasar spectra show that, 12 billion years ago, the temperature of the cosmic microwave background was slightly lower than it is today.

Observations

- Large-scale structure looks about the same in all directions. - The helium abundance is at least 25% in every galaxy studied so far. - The temperature of the cosmic microwave background varies slightly with direction. - The cosmic microwave background temperature is 2.73 K.

Which of the following represent observations or measurements that have confirmed key predictions of the Big Bang model?

- The abundance of helium in the universe. - Characteristics of the cosmic microwave background.

What happened within the first 5 minutes of the Universe

- inflation occurred - strong force and electroweak force first became distinct - antielectrons (positrons) as common as electrons - temperature fell to 10^15 K

Which of the following does not provide strong evidence for the Big Bang theory?

- observations of the cosmic microwave background *- observations of the amount of hydrogen in the universe * - observations of the ratio of helium to hydrogen in the universe

The Big Bang theory is closely linked to Hubble's discovery that the universe is expanding, which seems to imply that there was a time in the past when the expansion first began. Nevertheless, the Big Bang theory did not gain widespread acceptance among scientists until the 1960s. Why wasn't expansion alone enough to convince scientists that the Big Bang really happened?

Although expansion seems to imply a Big Bang, no other specific predictions of the Big Bang theory were tested and confirmed until the 1960s.

Coolest to hottest

Era of Galaxies - Planck era

List the eras of the Universe from top to bottom based on what First Occurred to what Last Occurred.

First occurred - Planck era - GUT era - Electroweak era - Particle era - Era of Nucleosynthesis - Era of Nuclei - Era of Atoms - Era of Galaxies Last occurred

The _______ era refers to a time period in which the strong, weak, and electromagnetic forces were all unified.

GUT

During the history of the universe, what important event occurred about 0.001 seconds after the Big Bang?

Most matter was annihilated by antimatter.

The charge of an antiproton is

Negative

The __________ refers to a time period in which all four forces are thought to have been unified.

Planck era

Smallest to Largest

Plank era - era of galaxies

What kind of particle does the Large Hadron Collider accelerate?

Protons

Which of the following important events occurred earliest in the history of the universe?

Space-time rapidly expanded during a brief period of inflation.

What famous (or infamous) United States collider, set to be built in Texas, was cancelled in 1993?

Superconducting Super Collider

Which of the following best explains why the night sky is dark?

The observable universe is not infinite.

"Large-scale structure grew around density variations present in the early universe." Observational evidence that such density variations really existed comes from the fact that the cosmic microwave background exhibits __________.

Tiny temperature variations in different directions - These variations served as "seeds" for the later formation of large-scale structure; without such seeds, gravity could not have created such large structures in only 14 billion years.

When a proton and an antiproton collide, they

They convert into two photons

According to the article, the scientific impact of the Large Hadron Collider can be summarized by which of the following statements?

Unknown. It will not explore truly new territory until it has been verified at lower energies for the first few years of use.

Most of the helium in the universe formed during the_________

era of nucleosynthesis

Compared to when the cosmic microwave background was first released, the radiation of the cosmic microwave background today is __________.

fainter and has most of its photons at longer wavelengths

Era Of Nucleosynthesis

fusion created helium nuclei

Era of Atoms

neutral atoms existed, but not stars

Which of these pieces of evidence supports the idea that inflation really happened?

observations of the cosmic microwave background that indicate a flat geometry for the universe

Particle Era

protons, neutrons both common

Era of Galaxies

stars and galaxies common

GUT Era

strong, electroweak forces unite as GUT force

Which of the following accelerators held the record for the highest energy collisions before the Large Hadron Collider broke it?

the Tevatron at Fermilab

The Large Hadronic Collider set a new world record in December, 2009. What was the record for?

the highest ever kinetic energy of a proton colliding in a human-made particle accelerator

Essentially all the hydrogen nuclei that will ever exist in our universe were created __________.

by the time the universe was about 3 minutes old

What happened sometime after the first 5 minutes of the Universe

- stars formed - galaxies formed - photons of cosmic microwave background released - carbon nuclei formed by fusion

Rank these times from Shortest Peak Wavelength in the spectrum of the cosmic microwave background to Longest

- 500,000 years after the Big Bang - 1 million years after the Big Bang - 100 million years after the Big Bang - 1.5 billion years after the Big Bang - today

Inferences from model

- The cosmic microwave background is radiation left over from the Big Bang. - Large-scale structure grew around density variations present in the early universe. - Fusion during the universe's first five minutes produced 75% hydrogen and 25% helium (by mass). - Photons of the cosmic microwave background have traveled through space for almost 14 billion years.

Which of the following does inflation help to explain?

- the origin of hydrogen *- the origin of galaxies* - the origin of atomic nuclei

Era of Nuclei

H, He nuclei and electrons existed but no neutral atoms

Rank these times from top to bottom the Coolest Temp of the universe to the Hottest Temp

Coolest - today - 1.5 billion years after the Big Bang - 100 million years after the Big Bang - 1 million years after the Big Bang - 500,000 years after the Big Bang Hottest

Which of the following offers at least some evidence that inflation really occurred in the early universe?

Measurements of brightness variations in the cosmic microwave background.

"Photons of the cosmic microwave background have traveled through space for almost 14 billion years." This statement follows from our model of the Big Bang, because the Big Bang model is based on the idea that __________.

the universe began very hot and dense and has been cooling as it expands - Photons could first travel freely when the universe was about 380,000 years old and had a temperature of about 3,000 K. These photons are what we see today—almost 14 billion years later—as the cosmic microwave background.

The Large Hadron Collider is designed to reach high energies. The results of this experiment are relevant to which of the following astrophysical situations?

the universe in its first trillionth of a second after the Big Bang

When the universe was 380,000 years old, its thermal radiation spectrum consisted mostly of

visible and infrared photons.