Chapter 28

According to calculations made by modern astronomers, the age of the universe is close to

14 billion years.

In what year did Einstein publish his general theory of relativity?

1915

The ordinary matter of the universe is made of about

25% helium

How many dimensions are there in spacetime?

4

Electrons, protons, and neutrons (ordinary matter) make up not more than

4% of the universe

According to recent evidence, how long ago did the expansion of the universe start accelerating?

7.5 billion years ago

If we can't see dark matter, how do we know it is there?

Because of its gravitational effects

When we speak of time dilation, we mean that time

stretches with speed.

Relativity is the

study of how space, energy, and mass are related to time.

Dark Matter is matter that

cannot be seen or felt, but can be measured through its gravitational effects.

It currently appears that within this universe we have mostly

dark energy.

Dark energy appears to have a greater effect on regions of the universe that are

empty

Edwin Hubble discovered that the farther away a galaxy is the

faster it is receding from us.

Compared to a clock at the bottom of a very tall skyscraper, a clock at the top of this skyscraper will appear to run

faster.

The modern theory of dark energy arises from observations showing that

galaxies are accelerating away from each other.

The universe as a whole is

has yet to be determined, although most astrophysical data points to a flat universe.

Is dark matter found mostly within a galaxy or just outside a galaxy?

just outside a galaxy

Dark matter is not affected by

light

The Big Bang

marked the beginning of space and time.

Spacetime is curved by

mass.

In a flat universe parallel lines

never converge.

Where is dark matter found in the periodic table?

no where at all

What type of matter is visible?

ordinary matter

Light bends when it

passes a massive star passes through a gravitational field

The "Big Bang" refers to the

point in time in which the known (and perhaps knowable) universe came into being.

According to cosmic inflation theory, the distribution of galaxies we see today is a consequence of

quantum fluctuations in the exceedingly small early universe.

Heat death refers to the universe

reaching the lowest energy state possible, which will mean the greatest level of entropy.

Evidence for dark matter is exhibited by the

relatively similar speeds at which all stars in a galaxy orbit the galactic nucleus speed at which galaxies orbit one another within clusters degree to which galaxy clusters exhibit gravitational lensing effects.

A greater gravitational field causes time to

slow down.

What did Einstein refer to as the greatest blunder of his life?

the creation of the cosmological constant

Cosmology is the study of the overall structure and evolution of

the universe

The theory of dark energy tells us that

there is still much to learn about this universe there is a force that behaves like an anti-gravity empty space is seething with a form of energy.

What else are you moving through?

time

Cosmic background radiation refers to

uniformly distributed residual radiation that resulted from the Big Bang.

Dark energy

would be considered to be the opposite of gravity is energy that exerts an outward pressure, causing spacetime to expand is the phenomenon responsible for the acceleration of the universe.

According to relativity theory, it is possible to reverse time and grow younger when you

you can never grow younger.

If you travel at high speed, then compared with your friends who "stay at home," you are

younger.

Which is more abundant: dark matter or ordinary matter?

Dark matter is six times more abundant than ordinary matter.

Clocks on fast-moving spaceship whizzing past Earth appear to run slow when viewed from

Earth.

Did Einstein first believe that the universe was static or dynamic?

He believed the universe was static.

In a huge cloud of ordinary matter and dark matter, the two are uniformly mixed together. Over time, the ordinary matter becomes concentrated toward the center of this cloud. Why?

Ordinary matter collides with other particles of ordinary matter. It releases some of its kinetic energy as electromagnetic radiation, and it then slows down and falls together.

The average temperature of the universe right now is about 2.73 K. Will this temperature likely go up or down over the next billion years?

The average temperature of the universe should to decrease.

What was Einstein's cosmological constant?

The cosmological constant was a hypothesis that there was a repulsive force to balance gravitational attraction to keep the universe static.

What would happen to the curvature of a balloon if it could be inflated to the size of the Sun?

The curvature of the balloon would decrease and seem almost flat.

Light is without mass, so how can gravity have an effect on light?

The space through which the light passes is curved.

Distant galaxies are

accelerating away from each other

The Big Rip refers to the

accelerating influence of dark energy, causing all matter to become completely ripped apart.

Cosmic Inflation refers to

an extremely rapid expansion of the early universe that occurred in an extremely brief period of time.

What Einstein discovered about space and time is that they

are parts of one whole.

Astronomers who subscribe to the Big Bang theory believe the Big Bang occurred

at the beginning of time about 14 billion years ago.

If dark matter were to be found on this planet it would likely be

at the center of Earth's core

The "redshift" of a galaxy refers to the rate

at which is receding.

Space and time are

bound together