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33 Cards in this Set

  • Front
  • Back

Age of Universe

14 billon years ago

Age = separation distance / recessional velocity

Alan Guth

Developed the idea of inflation which solved the problem of how the universe on a large scale would have a fairly uniform temp. in late 1980

Big Bang Theory

Idea that the universe was a hot dense object of pure energy and then drastic outward expansion occured, thus the Big Bang Theory

Evidence: Half a sec. after the Big Bang, space was filled with electromagnetic radiation and the dominant wavelength was about 10^ -14 M, Universe was at about 10^ 12 K.

Big Crunch

Gravity halts expansion and reverses it - the universe collapeses in on itself - returns to a hot concentrated point

Contraction -----> Big Crunch

If the expansion velocity is too small, the universe will collapse and end as a "Big Crunch"

Rμv - ½ RGμv = 8пG Tμv


Compact quasar associated with supermassive black holes at the center of active giant elliptical galaxies

Clusters & Superclusters

Clusters: Collections of galaxies

Superclusters: Grouping of several clusters of galaxies into a larger, but not necessarily gravitationally bound unit.

Cosmic Microwave Background Radiation (CMBR)

Discovered by Penzias and Wilson.

Perfectly isotropic (intensity is the same in all directions). It is microwave radiation that is found everywhere and is left over from the BB.

Equal to 1 mm.

This is a problem because you cannot have different locations that are not causally connected that have the same temp. (inflation solves this problem) (Note: Alan Guth)

Cosmological Constant, Cosmological Redshift, & Cosmology

Hubble used doppler formula-redshift recessional velocities to show that the universe is expanding.

Space time is expanding, hence wavelengths increase/produce redshift.

Cosmological Constant: Introduced by Einstein to keep the universe in a "steady state" - works as an anti-gravity force.

Cosmological redshift: The wavelength shift we see from distant galaxies. A product of an expanding universe. Longer wavelengths have been detected. Hubble uses the doppler formula to find redshift.

Cosmology: Study of the universe, its origin, its current structure, and it's fate. Its framework is Einstein's theory of general relativity.

Dark energy

We can't see dark energy.

Origins: Virtual pairs which produce repulsive energy, thus dark energy is responsible for the expansion of the universe (Note: Big Bang Theory) (Note: Big Crunch)

The last 15 years we have noticed that instead of slowing down, the expansion of the universe is speeding up. This suggests a repulsive force that is pushing matter apart.

This measured acceleration expansion of the universe is described by dark energy and/or vacuum energy and/or cosmological constant.

Dark energy conveniently solves 2 problems: accelerated expansion and required mass/energy for a flat universe.

We know that about 4% of the universe ... but we don't know that for the other 96% - which is dark matter

We want to add up all the matter to see if it yields a flat universe (Note: Google doc for the chart).

Dark Matter

Makes up most of the Universe.

Invisible and glues everything together.

(Note: Dark energy)

Doppler Redshift

Object is moving AWAY from earth.

(Note: Cosmological redshift)

Edwin Hubble

Used doppler redshift to determine that the universe is expanding (Note: Edwin Hubble) (Note: Cosmolgical Constant) (Note: Cosmoligical redshift)

Electromagnetic force

Binds electrons to nucleus and forms atoms

10^ 10 times stronger than gravity

Electroweak Theory, Steven Weinberg

Steven Weinberg recognized the W-BOSON behaves like a photon in the early 1970s. Recognized that he could reproduce neutron decay with with a feynman diagram that looked a little different than the original diagram.

Electroweak force: Unites electromagnetism and the weak nuclear forces.

4 Fundamental Forces

1. Gravity - Binds objects that have mass.

2. Electromagnetic - 10^ 40 times stronger than gravity. Binds objects that have electrical charge.

3. Weak Force - Responsible for turning down quark into an up quark.

4. Strong Force - Binds quarks to form neutrons and binds these to form a nucleus.

Galactic collisions

Galaxies close together collide to form elliptical galaxy clusters dominated by a single larger elliptical galaxy

Gamma-Ray Bursts

A typical gamma ray burst emits as much energy in 1 min. as our sun will emit over its entire 10 billion year life span.

Two sources behind gamma-ray burst:

1: binary system of 2 neutron stars.

2: binary system of a black hole and a neutron star - black hole swallows neutron star.

General Relativity Theory (GR)

Produced by Einstein

Universe must either expand OR extract


(Note: Cosmology).

Gravity Force

Responsible for binding any object that has mass.

High Energy Physics & Length Scales

The study of particles that comprise the basic building blocks of the universe. The particles that make up the nucleus and particles such as electrons.

High energy physics is the study of the "very small."

All energies that physics does become "high energy." High energy physics: 100 MeV

Max Plauch: Energy of photon: E = hc

Length Scales: orders of magnitude

Hubble flow

Distant galaxies are all moving away from us.

Speed increasing with increasing distance.

Hubble's Constant and Law Inflation

Hubble's Constant: Ho = -75 km/s/MPC

Hubble's Law: The observation that the farther away a galaxy is, the faster it's moving away.

Law inflation: Moments after the Big Bang, the universe rapidly expanded - Horizon Distance.

Lawrence Krauss

Created quintessence - an atlernative theory to the vacuum energy of dark energy which allows for a variable vacuum energy. This is a very new theory.

Krauss was the first to suggest Dark Energy (Note: Dark Energy).

Local Group

Collection of a few dozen galaxies.

Matter Dominated & Radiation Dominated Universe

Matter-dominant: From 300,00 years until today we have had a matter dense universe. This is when the universe began to expand and cool, and the photon density drops below the Baryonic (matter) density.

Radiation-dominant: From the Big Bang until 300,000 years, the universe was radiation-dominant. This is when the density of photons exceeds the density of matter (Baryonic). This means photons had a greater effect than matter.


When we force quantum theory onto General Relativiy, it produces an effect that allows for a variable vacuum energy density.

Alternative theory to dark energy/vacuum energy (Note: dark energy)

Gets rid of "fine tuning."

New theory developed by Larry Krauss (Note: Lawrence Krauss).

Recessional Velocity

Part of Hubble's Law - the "V" variable. Hubble used the doppler formula to get redshifts and recessional velocities. Recessional velocity is also used to find the age of the universe. (Note: Age of universe) (Note: Edward Hubble) (Note: Google doc to see Feynman Diagram)

Special Relativity's Constraint on Fluctuating Objects

Luminoisity of Quasar fluctuates, special realitivity puts a limit on the size of the fluctuating, luminous object.

Strong force

Responsible for binding quarks to form netruons and protons that then bind together to form nuclei of atoms (Note: 4 fundametal forces)

Superstrings and Brane Theorry

Superstrings: the leading framework for Quantum Gravity. Quantum Theory of Gravity is needed to describe the inner structure near the singularity of a black hole.

String Theory / M Theory / Brane Theory: Theory that interprets all particles and forces in terms of particular modes of vibration of submicroscopic strings.

Tully & Fisher's Relation and Law

Tully & Fisher's Relation: A relation used to determine the absolute luminosity of a spiral galaxy. The rotational velocity, measured from the broadening of spectral lines, is related to the total mass, and hence the total luminosity.

Tully & Fisher's Law: The luminosity is calculated by multiplying the galaxy's apparent brightness by 4πd2, where d is its distance from us - relationship between a spiral galaxy's luminosity and velocity

Emission lines: Lines of EM on and emission spectrum: lines of light through black.

Vacuum Energy

The cosmological constant in the Einstein field equation represents the energy of space. In space (vacuum), particles are constantly appearing and disappearing. This adds energy to the vacuum. This energy produces a repulsive gravitational force. Recall that matter produces an attractive gravitational force.

As the universe continues to expand, the density of matter will decrease. However, the vacuum energy will win out over attractive gravity. Thus, we should see acceleration in the expansion.

Big Bang occurs, kinetic energy causes expansion. Because matter exists, it gives rise to a repulsive gravitational force. This causes an accelerated expansion.

This is the problem: The scenario described above requires what we call a "fine tuning" between the matter density and vacuum energy.

Weak Force

Force that converts a down quark into an up quark. Explains Neutron Decay.