GUT epoch:
general relativity:
gravitational waves:
Hubble constant:
inflationary scenario:
MACHOs:
microlensing:
negatively curved:
neutralinos:
neutrino oscillations:
neutron stars:
positively curved:
Quantum gravity:
quasars:
Schwarzschild radius:
Superconductors:
Superstring theory:
spontaneous symmetry breaking:
superforce:
TOE epoch:
thought experiment:
WIMPs:
the time period from 10−43to 10−34after the Big Bang, when Grand Unification Theory, in which all forces except gravity are
identical, governed the universe
Einstein’s theory thatdescribes all types of relative motion including accelerated motion and the effects of gravity
mass-created distortions in space that propagate at the speed of light and that are predicted by general relativity
a central concept in cosmology whose value is determined by taking the slope of a graph of velocity versus distance, obtained
from red shift measurements
the rapid expansion of the universe by an incredible factor of 10−50for the brief time from 10−35to about 10−32s
massive compact halo objects; microlensing objects of huge mass
a process in which light from a distant star is focused and the star appears to brighten in a characteristic manner, when a small
body (smaller than about 1/1000 the mass of the Sun) passes between us and the star
an open universe that expands forever
a type of WIMPs having masses several orders of magnitude greater than nucleon masses
a process in which any type of neutrino could change spontaneously into any other
literally a star composed of neutrons
a universe that is closed and eventually contracts
the theory that deals with particle exchange of gravitons as the mechanism for the force
the moderately distant galaxies that emit as much or more energy than a normal galaxy
the radius of the event horizon
materials with resistivity of zero
a theory to unify gravity with the other three forces in which the fundamental particles are considered to act like one-
dimensional vibrating strings
the transition from GUT to electroweak where the forces were no longer unified
hypothetical unified force in TOE epoch
before 10−43after the Big Bang
mental analysis of certain carefully and clearly defined situations to develop an idea
weakly interacting massive particles; chargeless leptons (non-baryonic matter) interacting negligibly with normal matter
Section Summary
34.1 Cosmology and Particle Physics
- Cosmology is the study of the character and evolution of the universe.
- The two most important features of the universe are the cosmological red shifts of its galaxies being proportional to distance and its cosmic
microwave background (CMBR). Both support the notion that there was a gigantic explosion, known as the Big Bang that created the universe.
- Galaxies farther away than our local group have, on an average, a recessional velocity given by
v=H 0 d,
wheredis the distance to the galaxy andH 0 is the Hubble constant, taken to have the average valueH 0 = 20km/s ⋅ Mly.
- Explanations of the large-scale characteristics of the universe are intimately tied to particle physics.
- The dominance of matter over antimatter and the smoothness of the CMBR are two characteristics that are tied to particle physics.
- The epochs of the universe are known back to very shortly after the Big Bang, based on known laws of physics.
- The earliest epochs are tied to the unification of forces, with the electroweak epoch being partially understood, the GUT epoch being
speculative, and the TOE epoch being highly speculative since it involves an unknown single superforce.
- The transition from GUT to electroweak is called spontaneous symmetry breaking. It released energy that caused the inflationary scenario,
which in turn explains the smoothness of the CMBR.
34.2 General Relativity and Quantum Gravity
- Einstein’s theory of general relativity includes accelerated frames and, thus, encompasses special relativity and gravity. Created by use of
careful thought experiments, it has been repeatedly verified by real experiments.
- One direct result of this behavior of nature is the gravitational lensing of light by massive objects, such as galaxies, also seen in the
microlensing of light by smaller bodies in our galaxy.
- Another prediction is the existence of black holes, objects for which the escape velocity is greater than the speed of light and from which nothing
can escape.
CHAPTER 34 | FRONTIERS OF PHYSICS 1231
