WMAP Universe Flashcards
What is cosmology?
The scientific study of the large-scale properties of the universe as a whole, using the scientific method to test theories about the universe’s origin, evolution, and ultimate fate.
What are the two theoretical pillars of the Big Bang model?
1) General Relativity (Einstein’s theory of gravity as space-time distortion) and 2) The Cosmological Principle (the universe is homogeneous and isotropic on large scales).
What does the Cosmological Principle state?
The universe is homogeneous (looks the same at every point) and isotropic (looks the same in all directions) when averaged over very large scales.
What is the critical density of the universe?
The density threshold that determines whether the universe is open, closed, or flat (approximately 6 hydrogen atoms per cubic meter).
What is the Big Bang theory?
The theory that the universe originated 13.7 billion years ago from an extremely hot, dense state and has been expanding ever since.
What is a common misconception about the Big Bang?
That it was an explosion at a single point in space. Actually, it was the simultaneous appearance of space everywhere, with all points expanding away from each other.
Approximately how old is the universe according to WMAP measurements?
13.7 ± 0.13 billion years (with 1% accuracy).
What is the cosmic microwave background radiation (CMB)?
The remnant heat from the Big Bang - a nearly uniform glow of microwave radiation that fills the universe and is currently at a temperature of 2.725 Kelvin.
What are the three major observational pillars supporting the Big Bang theory?
1) The expansion of the universe, 2) The abundance of light elements (H, He, Li), and 3) The cosmic microwave background radiation.
Who discovered the expansion of the universe and when?
Edwin Hubble in 1929, by observing that galaxies are moving away from us at speeds proportional to their distance.
What is Hubble’s Law?
The observation that galaxies are receding from us at a speed proportional to their distance: v = Hₒd, where Hₒ is the Hubble constant.
What is Big Bang Nucleosynthesis (BBN)?
The process of light element formation (hydrogen, helium, and lithium) during the first few minutes after the Big Bang.
Who discovered the cosmic microwave background radiation and when?
Arno Penzias and Robert Wilson in 1965, accidentally while working at Bell Laboratories.
According to WMAP, what is the composition of the universe?
4.6% ordinary matter (atoms), 23% cold dark matter, and 72% dark energy.
What is dark matter and how do we know it exists?
A form of matter that doesn’t interact with light but exerts gravitational force. Its existence is inferred from galaxy rotation curves, gravitational lensing, and CMB fluctuations.
What is dark energy?
A mysterious form of energy with negative pressure that makes up about 72% of the universe and is causing the universe’s expansion to accelerate.
What is the ‘surface of last scattering’?
The moment about 380,000 years after the Big Bang when the universe cooled enough for electrons and protons to form neutral hydrogen, allowing photons to travel freely through space. This is what we observe as the CMB.
What is cosmic inflation?
A theory proposing that the universe underwent extremely rapid exponential expansion in the first fraction of a second of its existence, increasing in size by a factor of ~10^26.
What three major problems of standard Big Bang cosmology does inflation solve?
1) The Flatness Problem, 2) The Horizon Problem, and 3) The Monopole Problem.
What is the Flatness Problem?
The question of why the universe appears so precisely flat, which would require extreme fine-tuning in the standard Big Bang model but is naturally explained by inflation.
What is the Horizon Problem?
The puzzle that distant regions of space have the same temperature despite being too far apart to have ever been in causal contact without inflation.
How did structure (galaxies, stars) form in the universe?
From small density fluctuations in the early universe that were amplified by gravity over time.
What is the origin of the density fluctuations that led to galaxy formation?
Quantum fluctuations during the inflation period that were stretched to macroscopic scales.
When did the first stars in the universe form, according to WMAP?
Approximately 400 million years after the Big Bang.
How were elements heavier than lithium formed?
They were formed in the interior of stars through nuclear fusion and dispersed through space by supernovae explosions.
What does WMAP tell us about the geometry of the universe?
The universe is flat to within a 0.5% margin of error.
What is likely to be the ultimate fate of our universe based on current observations?
The universe will likely expand forever, especially since dark energy is accelerating the expansion.
What is the cosmological constant?
A term in Einstein’s equations of General Relativity, now associated with dark energy and the vacuum energy of space, that can cause accelerating expansion.
How does dark energy affect the expansion of the universe?
Unlike gravity which slows expansion, dark energy causes the expansion of the universe to accelerate over time.
What are the main components of the Milky Way galaxy?
A thin disk with spiral arms, a bar of older stars, and an extended dark halo.
What happens when a low-mass star like our Sun dies?
It exhausts its hydrogen, expands into a red giant, sheds its outer layers forming a planetary nebula, and the core becomes a white dwarf.
What happens when a massive star dies?
It undergoes a supernova explosion, dispersing heavy elements throughout space, and the core becomes either a neutron star or a black hole.
Why are supernovae important for life in the universe?
They disperse heavy elements like carbon, oxygen, and iron that are necessary for the formation of planets and life.
