Human beings have always looked

into the sky

and marveled at its beauty.

Theyâ€™ve also speculated about its

nature,

and tried to impose system and order on it.

into the sky

and marveled at its beauty.

Theyâ€™ve also speculated about its

nature,

and tried to impose system and order on it.

A Brief History of Cosmology |

The Greek philosopher Aristotle was

an early speculator. His theory was

based on the common-sense

observation that the sun, moon and

stars seemed to move around the

earth. This was satisfying to humans,

who liked to put themselves in the

middle of things.

Aristotle developed the theory of eight

crystal spheres on which the sun,

moon, planets and stars rotated in

perfect, unchanging paths. Their

circular perfection was in contrast with

the earth, where all changed and

decayed, motion was in straight lines,

and the earth itself stood still.

an early speculator. His theory was

based on the common-sense

observation that the sun, moon and

stars seemed to move around the

earth. This was satisfying to humans,

who liked to put themselves in the

middle of things.

Aristotle developed the theory of eight

crystal spheres on which the sun,

moon, planets and stars rotated in

perfect, unchanging paths. Their

circular perfection was in contrast with

the earth, where all changed and

decayed, motion was in straight lines,

and the earth itself stood still.

Claudius Ptolemaeus in the 2nd century

A.D. agreed with Aristotle that the

universe orbits about a stationary

Earth, but he refined the theory by

suggesting that the planets move in

circular epicycles with a center that

moved in a larger circular orbit around

a point near the earth.

The Ptolemaic system was the

longest-lasting of the universe models.

A.D. agreed with Aristotle that the

universe orbits about a stationary

Earth, but he refined the theory by

suggesting that the planets move in

circular epicycles with a center that

moved in a larger circular orbit around

a point near the earth.

The Ptolemaic system was the

longest-lasting of the universe models.

Ptolemaeusâ€™ theory reigned supreme

for some 13 centuries, when the Council

of Trent in 1543 asked a mathematician,

Nicholas Copernicus, to address a

difficulty with the calendar, the difference

between solar and lunar months, which

caused days to be lost and made it

particularly difficult to determine Easter.

Copernicus ended up questioning the

entire Aristotelian concept of an earth-

centered universe, suggesting instead that

the earth, as well as the other planets,

revolved around the sun. The Copernican

theory enabled accurate and repeatable

observation, the basis of science.

for some 13 centuries, when the Council

of Trent in 1543 asked a mathematician,

Nicholas Copernicus, to address a

difficulty with the calendar, the difference

between solar and lunar months, which

caused days to be lost and made it

particularly difficult to determine Easter.

Copernicus ended up questioning the

entire Aristotelian concept of an earth-

centered universe, suggesting instead that

the earth, as well as the other planets,

revolved around the sun. The Copernican

theory enabled accurate and repeatable

observation, the basis of science.

Galileo Galilei, who became professor

of mathematics at Padua in 1591,

decided that science should be based

on regular occurences, which could be

repeatedly observed and reduced to

mathematics. He determined that

falling objects accelerated as they fell.

In 1610, he identified the three moons

of Jupiter, positing that, if they circled

Jupiter while Jupiter circled the sun,

our moon could do the same. He

discovered sunspots. And in 1624, he

argued that the tides were due to the

earthâ€™s movement.

Finally, in 1632, his*Dialogues on the *

Two Chief Systems of the World

attacked the opponents of the

Copernican system and led to his

house arrest, which continued until his

death in 1642. The book was in the

Index of Prohibited Books until 1835.

of mathematics at Padua in 1591,

decided that science should be based

on regular occurences, which could be

repeatedly observed and reduced to

mathematics. He determined that

falling objects accelerated as they fell.

In 1610, he identified the three moons

of Jupiter, positing that, if they circled

Jupiter while Jupiter circled the sun,

our moon could do the same. He

discovered sunspots. And in 1624, he

argued that the tides were due to the

earthâ€™s movement.

Finally, in 1632, his

Two Chief Systems of the World

attacked the opponents of the

Copernican system and led to his

house arrest, which continued until his

death in 1642. The book was in the

Index of Prohibited Books until 1835.

Johannes Kepler studied planetary

motion in detail, discovering that Marsâ

€™ path around the sun was not

circular, but elliptical. It speeded up

when it was closer to the sun and

slowed down when it was farther away.

Kepler discovered geometrical laws

which applied to planetary orbit: the

duration of a planetary orbit equals its

distance from the sun cubed.

motion in detail, discovering that Marsâ

€™ path around the sun was not

circular, but elliptical. It speeded up

when it was closer to the sun and

slowed down when it was farther away.

Kepler discovered geometrical laws

which applied to planetary orbit: the

duration of a planetary orbit equals its

distance from the sun cubed.

In 1631, the frenchman Rene Descartes,

in*The Discourse on Method*, said to

doubt everything, accept as probable

what was considered certain, and reject

everything else. The only certainty was

thought or critical doubt. The simplest

solution should be examined before the

more complex, straight lines before

curves. He imagined a problem solved

and studied the consequences of the

solution to determine whether his solution

was right or wrong.

He described a universe that wasnâ€™t

a vacuum and didnâ€™t need attraction

to function, postulating that three kinds of

matter--solids, light and ether--filled

space. The spinning of the planets in a

vortex created gravity. â€œThe world is

a machine,â€� he concluded, using

graphing to determine position.

in

doubt everything, accept as probable

what was considered certain, and reject

everything else. The only certainty was

thought or critical doubt. The simplest

solution should be examined before the

more complex, straight lines before

curves. He imagined a problem solved

and studied the consequences of the

solution to determine whether his solution

was right or wrong.

He described a universe that wasnâ€™t

a vacuum and didnâ€™t need attraction

to function, postulating that three kinds of

matter--solids, light and ether--filled

space. The spinning of the planets in a

vortex created gravity. â€œThe world is

a machine,â€� he concluded, using

graphing to determine position.

Isaac Newton, an Englishman,

discovered how the universe worked in

two years, but didn't publish his

findings until 20 years later, in 1687, in

*Principia Mathematica*. By limiting

his search to how, not why, he

developed calculus to measure the

changing forces involved in planetary

dynamics.

Differential calculus measured the

difference caused by change. Integral

calculus studied how the rates of

change varied due to mutual attraction.

discovered how the universe worked in

two years, but didn't publish his

findings until 20 years later, in 1687, in

his search to how, not why, he

developed calculus to measure the

changing forces involved in planetary

dynamics.

Differential calculus measured the

difference caused by change. Integral

calculus studied how the rates of

change varied due to mutual attraction.

Modern scientific cosmology began in

Germany in 1917 with Albert Einsteinâ

€™s general theory of relativity, which

enabled the study of very distant

objects. Earlier physicists assumed the

universe to be static and unchanging.

General relativity consists of a set of

equations that must be solved from the

distribution of mass-energy and

momentum throughout the universe.

Einstein postulated matter without

motion and that matter was uniformly

distributed in a uniformly curved

spherical space.

Germany in 1917 with Albert Einsteinâ

€™s general theory of relativity, which

enabled the study of very distant

objects. Earlier physicists assumed the

universe to be static and unchanging.

General relativity consists of a set of

equations that must be solved from the

distribution of mass-energy and

momentum throughout the universe.

Einstein postulated matter without

motion and that matter was uniformly

distributed in a uniformly curved

spherical space.

The Russian, Alexander Friedmann,

pointed out in 1922 that the universe

expands then recollapses.

The curvature is negative but

unbounded, so theoretically the

universe can expand indefinitely. That

paved the way for the Big Bang theory

of origins.

pointed out in 1922 that the universe

expands then recollapses.

The curvature is negative but

unbounded, so theoretically the

universe can expand indefinitely. That

paved the way for the Big Bang theory

of origins.