Unit 1 – Big Bang Theory (Grade 11/12 Earth & Space Science)

20 question-and-answer flashcards covering key definitions, evidence, proponents, and concepts related to the Big Bang Theory, Hubble’s Law, redshift, and scientific method foundations.

What are the six classical steps of the scientific method?

(1) Prior observations, (2) Define the problem, (3) Formulate a hypothesis, (4) Perform the experiment, (5) Gather, analyse & interpret data, (6) Formulate the conclusion.

When does a hypothesis graduate to a scientific theory?

When repeated observations and experimental evidence consistently confirm it.

What is the Doppler Effect?

The change in wavelength or frequency of a wave caused by relative motion between the source and the receiver.

What is redshift in astronomy?

A shift of light toward longer wavelengths (the red end of the spectrum) that occurs when a luminous object is moving away from the observer.

According to the Big Bang Theory, approximately how old is the universe?

About 13.8 billion years.

State the Big Bang Theory in one sentence.

The universe began as an extremely hot, dense singularity that has been expanding and cooling ever since.

Which everyday model compares to galaxies separating in an expanding universe?

The raisin-bread (or raisin-dough) model—raisins (galaxies) move apart as the dough (space) rises.

In the balloon expansion activity, what does the increasing distance between dots represent?

Growing separations between galaxies as the fabric of space itself expands.

What is a singularity in cosmology?

A point of infinite density and temperature from which the universe is thought to have begun.

Define nucleosynthesis as used in Big Bang cosmology.

The formation of light elements (mainly hydrogen, helium, a little lithium) from protons and neutrons in the first few minutes after the Big Bang.

List three key pieces of evidence that support the Big Bang Theory.

(1) Universal expansion/redshift of galaxies, (2) Cosmic Microwave Background radiation, (3) Abundance of light elements (H, He, Li).

Who first proposed the idea of an expanding universe and the ‘primeval atom’?

Georges Lemaître.

What was Edwin Hubble’s pivotal discovery?

Galaxies are receding from us, and their recession velocity increases with distance—evidence that the universe is expanding.

What did Arno Penzias and Robert Wilson discover in 1965?

Cosmic Microwave Background (CMB) radiation—relic heat from the early universe.

State Hubble’s Law verbally.

The recessional velocity of a galaxy is directly proportional to its distance from Earth.

How does galaxy distance affect recession velocity according to Hubble’s observations?

Greater distance → higher recession velocity (a positive linear relationship).

Why don’t individual galaxies expand as the universe expands?

Internal gravitational forces hold the matter inside each galaxy together, counteracting cosmic expansion on that scale.

What present-day value has the Hubble Space Telescope measured for the expansion rate?

Approximately 21 km/s for every million light-years of distance.

How does redshift act as evidence for an expanding universe?

Because the wavelengths of light from distant galaxies are stretched, indicating those galaxies are moving away from us as space itself expands.

What relationship did Hubble’s original graph display between distance and velocity?

A straight-line (linear) increase—showing direct proportionality between a galaxy’s distance and its recessional speed.