Astronomy Cosmology and Deep Space 1 — Questions and Answers
Question 1: What is the Big Bang theory?
- The prevailing cosmological model explaining the universe's origin from an extremely hot, dense state approximately 13.8 billion years ago (Correct answer)
- A theory about how stars explode
- A model explaining only galaxy formation
- A disproven hypothesis about the universe
Correct answer: The prevailing cosmological model explaining the universe's origin from an extremely hot, dense state approximately 13.8 billion years ago
The Big Bang theory describes the universe expanding from an extremely hot, dense singularity approximately 13.8 billion years ago, supported by evidence including cosmic microwave background radiation, Hubble's Law, and primordial element abundances.
Question 2: What is dark matter?
- An unknown form of matter that doesn't emit or absorb light but exerts gravitational effects, comprising about 27% of the universe (Correct answer)
- Matter that exists only in darkness
- Black holes collectively
- Antimatter in deep space
Correct answer: An unknown form of matter that doesn't emit or absorb light but exerts gravitational effects, comprising about 27% of the universe
Dark matter is a hypothetical form of matter that doesn't interact with electromagnetic radiation but reveals its presence through gravitational effects on visible matter, galaxy rotation curves, and gravitational lensing.
Question 3: What is the cosmic microwave background radiation?
- Faint radiation from approximately 380,000 years after the Big Bang, filling all of space uniformly (Correct answer)
- Radio signals from distant alien civilizations
- Radiation from the Sun reflecting off cosmic dust
- Light from the first stars
Correct answer: Faint radiation from approximately 380,000 years after the Big Bang, filling all of space uniformly
The CMB is thermal radiation released when the universe cooled enough for atoms to form (recombination era, ~380,000 years after the Big Bang), now observed as microwave radiation at about 2.7 Kelvin.
Question 4: What is Hubble's Law and what does it tell us about the universe?
- The recessional velocity of galaxies is proportional to their distance — evidence that the universe is expanding (Correct answer)
- Stars are moving toward the Milky Way
- The universe is shrinking
- Galaxies orbit around a central point
Correct answer: The recessional velocity of galaxies is proportional to their distance — evidence that the universe is expanding
Hubble's Law (v = H₀d) states that the farther a galaxy is from us, the faster it's moving away, demonstrating that the universe is expanding and providing evidence supporting the Big Bang theory.
Question 5: What is a galaxy and what types exist?
- A gravitationally bound system of stars, gas, dust, and dark matter; types include spiral, elliptical, and irregular (Correct answer)
- A single large star
- A cluster of planets
- A nebula
Correct answer: A gravitationally bound system of stars, gas, dust, and dark matter; types include spiral, elliptical, and irregular
Galaxies are massive systems containing billions of stars, gas, dust, and dark matter held together by gravity. Major types are spiral (like the Milky Way), elliptical (round/oval), and irregular (no defined shape).
Question 6: What is gravitational lensing?
- The bending of light from distant objects by the gravity of intervening massive objects, as predicted by general relativity (Correct answer)
- A type of telescope lens
- Gravity affecting only light near black holes
- An optical illusion in Earth's atmosphere
Correct answer: The bending of light from distant objects by the gravity of intervening massive objects, as predicted by general relativity
Gravitational lensing occurs when massive objects (galaxies, galaxy clusters) warp spacetime, bending the path of light from more distant objects, creating arcs, rings, or multiple images, confirming Einstein's general relativity.
Astronomy Cosmology and Deep Space 1
What is the Big Bang theory?