Unit 1 Intro/ Chp 1: Big Bang Theory Flashcards
What observations led to the acceptance of the Big Bang theory?
“Three Pillars of Proof”
- Recession of stars/galaxies (as described by Hubble’s Law)
- The characteristics of cosmic microwave background radiation
- The abundance of light elements.
What are the steps of the scientific method?
begins with observation, proceeds to the formulation and testing of a hypothesis, and
eventually to theory and possibly to law.
How to define and measure time and space
define distance in terms of light years and parsecs, measure by
- Trigonometric Parallax (up to 500 ly)
- Main-Sequence Fitting (500- 500 million ly away)
- Cephid Technique (500- 500 million ly away)
- Hubble’s Law (Beyond 500 Million ly)
What is a singularity?
it can be said that a ‘singularity’ is an area in space-time where gravitational force is so high that all known laws of physics break down and do not apply.
What is the Big Bang theory? What does it describe?
The Big Bang theory is an effort to explain exactly what happened at the very beginning of the Universe.
-Before the Big Bang, the Universe did not exist. At the birth of the Universe, time and space were created in a gigantic expansion that emanated from a ‘singularity.’
Describe the Doppler shift
If the light source is moving toward the observer the light wavelength appears to shorten (i.e., to move into the blue spectrum, becoming “blue-shifted”), and if the light source is moving away from the observer the light wavelength appears to lengthen (i.e., to move into the red spectrum, becoming red-shifted)
-the faster the light-emitting object was moving, the greater the shift.
What are the possible shapes of the universe?
- sphere (positive curvature, ‘closed universe’)
- saddle-shaped (negative curvature, infinite, unbounded)
- flat (infinite, parallels are always parallels)
What makes up the most matter in the universe, dark matter or stars?
dark matter makes up more of the matter in the universe compared to stars. Dark matter accounts for 25% of the universe while starts account for <5%
What is the difference between dark matter and dark energy?
dark energy repels matter, while dark matter gravitates towards conventional matter (i.e. stars).
How can we know the age of the universe? (3 ways)
- Radioactivity
- Hubble’s Expansion Constant
- Cosmic Microwave Background Radiation
Hypothesis
educated guess based upon observation
Theory
A scientific theory summarizes a hypothesis (or group of hypotheses) that explain a set of observations, supported by repeated testing.
Law
A law governs a body of observations. At the time it is made, no exceptions will have been found to that law. A law does not say “why” things happen, rather it predicts how they happen.
Explain cosmic microwave background (pillar of proof)
The only explanation that makes any sense is that this CMB represents the very last remnants of the light/heat energy of the Big Bang’s initial expansion.
Abundance of light elements (pillar of proof)
the ratio of all the various atoms of the three lightest elements: hydrogen (75%), helium (25%) and lithium (trace). The observed abundance of all the different atoms of those elements can be explained only if they originated from one single ratio of the first subatomic particles of matter that can be formed from a super-hot environment.
