NATS 1572: Class 2 - A Model for the Universe

[Original iClicker] The Big Bang is the name we use for ________.

The event that marked the beginning of the expansion of the Universe

What observation supports the idea that the Universe is expanding?

Distant galaxies in all directions are moving away from us

What does the raisin cake analogy help explain about the expansion of the Universe?

As the cake expands, the distances between raisins increase, illustrating how distances between galaxies can increase

Why does the expanding Universe cool over time?

Its volume increases, spreading energy over a larger volume

What happened during Big Bang nucleosynthesis?

Nuclei of light elements formed through nuclear reactions in the early Universe

What is the predicted approximate composition of the Universe after Big Bang nucleosynthesis, by mass? 

75% hydrogen, 25% helium, with trace amounts of lithium

What happened approximately 380,000 years after the Big Bang during recombination?

Electrons combined with nuclei to form atoms, allowing radiation to travel freely through much of the Universe

What is the cosmic microwave background (CMB)?

Leftover radiation from the early Universe that has been stretched to microwave wavelengths by cosmic expansion

[Original iClicker] In what sense are we “star stuff”?

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

How do stars and supernovae contribute to the formation of heavier elements?

Nuclear fusion in stars and processes associated with stellar explosions produce heavier elements

Why are heavier elements important for the formation of planets and life?

They provide material needed to form rocky planets and organic molecules

What role do dust grains in molecular clouds playing in the formation of organic molecules?

They provide surfaces where molecules can form

[Original iClicker] With just a few exceptions, all planets and moons in our solar system rotate and orbit in…

The same direction as the Sun rotates

[Original iClicker] In essence, the nebular theory holds that _________.

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

What happens to a cloud’s rotation as it contracts under gravity, assuming negligible external torque?

It spins faster as it contracts

Why does a collapsing, rotating cloud of gas and dust flatten into a disk?

Collisions between particles help reduce motion in directions other than the cloud’s overall rotation

What causes a protostar to become a star?

Its core becomes to hot enough for nuclear fusion to begin

[Original iClicker] Which of the following types of material can condense into what we call ice at low temperatures?

Hydrogen compounds

What is the frost line in a protoplanetary disk?

The boundary beyond which certain hydrogen compounds, such as water, can condense into solid ice

Why can giant planets form more easily in the colder outer regions of a protoplanetary disk?

Additional solid ices can help build large planetary cores that accrete more gas

What does the giant impact hypothesis propose about the origin of Earth’s Moon?

Material blasted from the early Earth during a giant collision later accumulated in Earth’s orbit and formed the Moon

[Original iClicker] What implications does the nebular theory have for life beyond Earth?

Other planetary systems should exist, with significant diversity

What does the concept of a fine-tuned Universe refer to in this lecture?

The idea that certain fundamental properties and physical conditions appear to affect whether a Universe can develop galaxies and life

According to the fine-tuned Universe discussion, what could happen if the Universe expanded too quickly?

Matter might not have enough time to gather into galaxies

In the Big Bang nucleosynthesis lab, why would changing the cooling time or reaction rates affect the final abundances of elements?

They change the opportunities for nuclear reactions to occur, affecting how much of each element forms