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GCSE Physics Unit 2 > Formation And Explanation > Flashcards

Formation And Explanation Flashcards

1
Q

How many stars does a galaxy typically contain?

A

One billion stars

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2
Q

How many galaxies is the Universe thought to contain?

A

Over one hundred billion

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3
Q

What are stars mainly made of?

A

Hydrogen and helium

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4
Q

What does hydrogen exist as in a star’s centre?

A

Nuclei (not atoms or molecules).

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5
Q

How does nuclear fusion happen in stars?

A

Hydrogen nuclei are positive so normally repel each other.
The temperature of a star’s centre is more than 15 million degrees.
This means the nuclei move very fast.
They collide to form a heavier nucleus: helium.
Vast quantities of energy (electromagnetic radiation) are released.

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6
Q

How are stars formed?

A

Clouds of hydrogen and dust are called stellar nebulae.
The particles coalesce due to gravity.
The clouds become more and more dense.
Hydrogen particles begin to spiral inwards and temperature rises to about 15 million degrees.
Nuclear fusion begins and the star is born.

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7
Q

What main force forms stars, galaxies and planets?

A

Gravity.

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8
Q

How are planets formed?

A

As a star burns, it pulls dust particles closer to it.
They are pulled more strongly as they have more mass.
They coalesce to form the inner rocky planets (Mercury, Venus, Earth and Mars).
This process is called accretion.
Gas particles have less mass so they are left further out.
They coalesce to form the gas giants (Jupiter, Saturn, Uranus and Neptune).

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9
Q

What are Pluto and Ceres believed to actually be, as opposed to planets?

A

Captured asteroids.

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10
Q

Why do planets orbit the Sun in the same plane and direction?

A

The gas and dust clouds originally spiralled in the same direction.

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11
Q

What does a star do to planets formed around it?

A

Catch them in its orbit. This is due to gravity.

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12
Q

Why does the Sun remain the same size?

A

The inward gravitational force equals the outward force of radiation pressure (which is due to thermonuclear explosions).

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13
Q

What model is mostly accepted that explains the origin of the Universe?

A

The Big Bang Theory

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14
Q

When did the Big Bang occur?

A

About 13.8 billion years ago.

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15
Q

From what did the Big Bang occur?

A

A tiny point called a singularity.

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16
Q

Explain the formation of the Universe.

A

An explosion occurred 13.8 billion years ago from a tiny point called a singularity.
The universe rapidly expanded and formed high-energy radiation like quarks.
As it got bigger, it cooled down and the quarks came together to form protons and neutrons.
As the universe cooled even more, electrons combined with nuclei to form atoms of hydrogen.

17
Q

What is the doppler effect?

A

Where as a source of waves moves, the wavelength in front of the source decreases and the wavelength behind the source increases.
This is why sirens have a lower pitch when they are moving away.

18
Q

Each colour in the spectrum has what associated with it?

A

A certain wavelength.

19
Q

What effect is red-shift associated with?

A

The doppler effect.

20
Q

What is red-shift?

A

Where the light we observe from a source is shifted towards the red end of the spectrum, as it is moving away from us and so has a longer wavelength.

21
Q

What does red-shift from distant galaxies suggest?

A

The galaxies are moving away from us. Therefore, it suggests the universe is expanding. It supports the Big Bang Theory.

22
Q

What is Cosmic Microwave Background Radiation (CMBR)?

A

Microwaves coming from various parts of the universe believed to be the remnant of the Big Bang.
It is further evidence of the Big Bang, as this is the only theory that can explain CMBR.

23
Q

What evidence approves the Big Bang? [2]

A
  1. Red-shift

2. Cosmic Microwave Background Radiation.

24
Q

What three events may happen to the Universe in the future?

A
  1. Big Freeze
  2. Big Crunch
  3. Big Bounce
25
Q

What is the Big Freeze?

A

If there is too little mass in the Universe, it will expand forever, becoming colder and colder and ending in a Big Freeze.

26
Q

What is the Big Crunch?

A

If there is enough mass in the Universe, gravity will cause expansion to stop and the galaxies will contract inwards and collide.

27
Q

What is the Big Bounce?

A

If gravity is big enough, the Universe may contract entirely back to a singularity. Then, another Big Bang would occur.

28
Q

How do we detect planets outside our Solar System?

A

We observe light coming from stars, watching for a transition. This is a small reduction in light reaching us when an orbiting planet passes between the star and us.

29
Q

How do we know that stars are mainly composed of hydrogen and helium?

A

We look at light we receive from the Sun.

30
Q

What evidence supports the idea that the Solar System was formed from a nebula?

A

Planets orbit the Sun in the same plane and direction.

GCSE Physics Unit 2 (15 decks)

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