Chapter 28 Lecture Flashcards

Flashcards covering key vocabulary from the Chapter 28 lecture notes.

Hubble's Law

The velocity of an object is proportional to its distance.

Blueshift

Light emitted from a source moving toward us will be shifted to the blue (high frequency).

Redshift

Light emitted from a source moving away from us will be shifted to the red (low frequency).

Implication of Hubble's Law

The universe is expanding.

The Big Bang Theory

The beginning of space and time.

Evidence for the Big Bang

Continuing expansion of the universe, cosmic background radiation, and measurements of element abundances.

Cosmic Microwave Background (CMB)

Observed by Arno Penzias and Robert Wilson in 1964, provides evidence for the Big Bang.

Condition of the Early Universe

The early universe must have been extremely hot and dense.

Inflation Theory

An early episode of rapid inflation can solve all three mysteries!

General Relativity

Gravity is the consequence of mass distorting the fabric of spacetime.

Principle of Equivalence

Einstein's idea that observations in an accelerated reference frame are indistinguishable from observations made in a Newtonian gravitational field.

Bending of Light by Gravity

Einstein predicted that starlight passing close to the Sun would be deflected by an angle of 1.75 seconds of arc.

Gravity and Time

Gravitation causes time to slow down.

Gravity and Space

Mass produces the curvature, or warping, of spacetime.

Gravitational Waves

Ripples in the overall geometry of spacetime.

Newtonian and Einsteinian Gravitation

Einstein showed that Newton’s law of gravitation is a special case of the broader theory of relativity.

Frame of Reference

The place from which motion is observed and measured.

Postulates of Special Theory of Relativity

All laws of nature are the same in all uniformly moving frames of reference; the speed of light in free space has the same measured value for all observers.

Simultaneity

Two events occur at the same time.

Spacetime

Space and time are intimately linked together, forming the spacetime continuum.

Time Dilation

Gravitation causes time to slow down

Length Contraction

Space if contracted, making objects look shorter when they move at relativistic speeds.

Mass, Energy, and E=mc^2

A piece of matter, even at rest, has an "energy of being" called rest energy.

Correspondence Principle

Any new theory or description of nature must agree with the old where the old gives correct results.

Dark Matter

Matter that does not exert the electromagnetic force, making it invisible and unable to interact with normal matter.

Dark Energy

Theory that says the universe is expanding faster and faster.

Fate of the Universe

Two possible scenarios for the end of the universe include Heat Death and The Big Rip.

Hubble's Law Importance

The beginning of our modern view.

Hubble's Measure of Distance

Hubble could deduce the distance of a star from the Earth by comparing its luminosity (energy) and brightness.

Analogy for the Expanding Universe

The expansion of the universe is like an ant on a balloon that is being blown up.

Observable Universe Limit

The farthest we can possibly see is about 14 billion light-years away.

Origin of the Whole Universe

The (whole) universe did not expand from a single point; it was probably always infinite in size.

The Big Bang

Theory - our universe began with a primordial explosion some 13.7 billion years ago.

Cosmic Microwave Background Origin

If the Big Bang did occur and the universe is expanding, the light emitted would have been red-shifted and appear as microwave signals.

Inflation's Role in Structure Formation

Tiny quantum ripples stretched to enormous size during inflation, becoming the seeds for all structures in the universe.

Inflation and Uniformity of CMB

Regions now on opposite sides of the sky were close together before inflation pushed them far apart.

Principle of Equivalence Definition

Observations made in an accelerated reference frame are indistinguishable from observations made in a Newtonian gravitational field.

Trajectory of Light in Gravity

The trajectory of a flashlight beam is identical to the trajectory of a baseball “thrown” at the speed of light.

Artificial Gravity

The acceleration needed to simulate gravity inside a spaceship.

Time Dilation on a Rotating Disk

Clocks 1 and 3 run at the same rate, while clock 2 runs slower reflecting relativity of time.

Motion of Mercury

Near the Sun, the planets elliptical orbits should precess.

Nature of Space

Space is a flexible medium that can bend and twist.

Geodesic Lines

Lines of shortest distance on a curved surface.

Gravitational Wave Ripple

When an object undergoes a change in motion, readjustments produce ripples in the overall geometry of spacetime.

Motion is Relative

Motion observed and measured is a frame of reference.

Relativistic Simultaneity

Two events that are simultaneous in one frame of reference need not be simultaneous in a frame moving relative to the first frame.

Spacetime Continuity

Space and time are linked together, forming the spacetime continuum and the greater the measured distance in space, the greater the measured interval of time.

The Twin Trip is Unsymmetric

When the traveling twin makes a distinct change of reference frame, evidenced by acceleration in turning around.

Difference Between Ordinary and Dark Matter

We cannot walk through a wall because it is made of atoms that we can interact with through the electromagnetic force which is one difference between ordinary and dark matter.