History of Astronomy and Basic Concepts About the Earth

Question 1

In the development of astronomical thought, certain original and imaginative individuals began to make systematic observations of celestial objects to formulate ________ and explain their behavior.

Answer 1

theories

(Explanation)

Ancient observers assumed the Earth was vast, immobile, and the center of the universe. Only when scientific procedures were developed did man’s concept of the universe begin to change.

Question 2

The ________ must call upon all his resources of ingenuity and employ more clever devises than the most astute detective to solve the problems of his business.

Answer 2

astronomer

(Explanation)

Astronomy is the science of the universe, and the laboratory for this science is afar and untouchable, other than the observations of fallen meteorites.

Question 3

The first significant development of astronomy as a science took place in ancient ________.

Answer 3

Greece

(Explanation)

China, India, Mesopotamia, and Egypt had also made celestial observations, even before the Greeks. But the Greeks were the ones who explored a reservoir of ideas and inspirations, and carried out experiments and observations that contributed to the development of astronomy as a science.

Question 4

The earliest Greek scientists were the _______, who lived in what is now Asia Minor.

Answer 4

Ionians

(Explanation)

The foremost astronomers of the Ionians were Thales and Anaximander. Thales introduced the concept of geometry and surveying. Anaximander may have been the first to speculate on the relative distances of the sun, moon, and planets.

Question 5

__________ was originally an Ionian in belief, but later founded a school of thought of his own regarding the shape of the planets.

Answer 5

Pythagoras

(Explanation)

Pythagoras pictured a series of concentric spheres in which each of the seven moving objects, the planets, the sun and the moon, was carried by a separate sphere from the one that carried the stars, so that the motions of the planets resulted from independent rotations of the different spheres about the Earth.

Question 6

A member of the Pythagorean school, _________ was the first to introduce the concept that the Earth is in motion.

Answer 6

Philolaus

(Explanation)

His concept proved to be erroneous in that he believed that there were two earths and that they each revolved equidistant from a central fire. However, he had set the “moving earth” concept in motion.

Question 7

One of the most famous of the Greek philosophers was _________.

Answer 7

Aristotle

(Explanation)

He wrote encyclopedic treatises on nearly every field of human endeavor during his time. Unfortunately, his expositions in astronomy were less sound than some of his other work. The greatest of the Greek accomplishments in the fields of physics and astronomy came post-Aristotle.

Question 8

The shape of the Moon in the sky depends simply on how much of its ________ hemisphere is turned to our view.

Answer 8

daylight

(Explanation)

The phases of the moon and of eclipses are the results of illumination by sunlight. The moon itself is not luminous (it does not emit its own light).

Question 9

___________ of Samos was the first astronomer of the Alexandrian school and devised an ingenious method to find the relative distances from the Earth to the sun and moon.

Answer 9

Aristarchus

(Explanation)

His procedure rests on the three assumptions:

1. that the moon goes about the Earth in a perfectly circular orbit,
2. that the moon’s orbital velocity is perfectly uniform, and
3. that the sun is near enough that its rays travel along diverging paths to different parts of the moon’s orbit.

Although all three of these assumptions are incorrect, he pioneered a scientific approach that could be used to determine the distances from the Earth to the sun and moon.

Question 10

___________ also devised an ingenious technique to determine the relative sizes of the sun, moon, and Earth.

Answer 10

Aristarchus

Question 11

The _________ hypothesis states that the Earth orbits the Sun and the Earth is not the center of the universe.

Answer 11

Heliocentric

(Explanation)

Aristarchus was the first to profess this belief. This is opposed to the geocentric model of the universe, which states that the Earth is at the center of the universe and all objects revolve around it. Aristotle and Ptolemy were believers in the geocentric model.

Question 12

___________ is the belief tha earth is at the center of the universe.

Answer 12

Geocentric

Question 13

The greatest astronomer of ancient times was __________.

Answer 13

Hipparchus

(Explanation)

His studies are credited with the development of both plane and spherical trigonometry, highly accurate observations, the use of old observations to determine changes, and the invention of a geometrical representation describing the motions of the Sun and Moon more precisely than ever before.

Question 14

Another Greek astronomer, Cladius Ptolemy, compiled a series of thirteen volumes on astronomy known as the ________.

Answer 14

Almagest

(Explanation)

Most of the Almagest is a compilation of the astronomical achievements of the past, especially Hipparchus. However, it does contain some of his own contributions including the measurement of the distance to the Moon by a technique essentially identical to the one used today.

Question 15

Nicolas Copernicus was born in Thorn on the Vistula in Poland. His forte was ___________.

Answer 15

mathematics

(Explanation)

His great contribution to science was a critical reappraisal of the existing theories of cosmology and the development of a new model of the solar system.

Question 16

Copernicus’s excellence as a mathematician and astronomer gave him the information to determine values for the distances of the various _______ from the Sun.

Answer 16

planets

(Explanation)

He lived from 1473 to 1543, yet his calculations compared to modern calculations show how advanced he was in his observations and mathematical genius.

Question 17

After beginning training for a medical career, _______ found that he had little interest in the subject and later switched to mathematics.

Answer 17

Galileo

(Explanation)

His refusal to accept dogmatic statements without proof allowed his mathematic abilities to proliferate. In 1589, he became professor of mathematics and astronomy at the university at Pisa.

Question 18

Question 17 of 56

Galileo’s greatest contributions were in the field of _________.

Answer 18

mechanics

(Explanation)

Galileo experimented with pendulums, with balls rolling down inclined planes, with light and mirrors, with falling bodies, and many other objects. Galileo showed that if a heavy and light object were dropped together, even from a great height, both would hit the ground at practically the same time.

Question 19

_______ has often been called the father of modern astronomy.

Answer 19

Galileo

(Explanation)

Galileo probably has been the person most widely recognized as the “father of modern astronomy”, although there are many historians that have given the title to Nicholas Copernicus or Johannes Kepler.

Question 20

The actual first telescope that attracted much notice was built by the Dutch spectacle maker _______________ in 1608, but was only about three power.

Answer 20

Hans Lippershey

(Explanation)

Historians generally credit Lippershey with the invention of the telescope, as he was the first to apply for a patent for a design. There is uncertainty about whether others had built telescopes earlier in the past.

Lippershey’s telescope was a simple refracting telescope which involved two lenses.

Question 21

The geocentric model, also known as the __________ system, is a theory that was developed by philosophers in Ancient Greece and was named after Claudius Ptolemy (circa 90 to 168 A.D.). It was developed to explain how the planets, the Sun, and the stars orbit around the Earth.

Answer 21

Ptolemaic

Question 22

Who presented the Heliocentric Theory first?

Answer 22

Aristarchus of Samos (c. 310 c. 230 BC)

(Explanation)

He was an ancient Greek mathematician and astronomer; he presented the first Heliocentric model. Heliocentric theory places the Sun at the center of the known universe with the Earth and the planets revolving around it. Before this, it was believed that the Earth was at the center of the universe (geocentric theory). Although Aristarchus was the first to propose the Heliocentric theory, it wasn’t until 1549, when Copernicus presented his Heliocentric model that the idea began to be accepted.

Question 23

_______ was the first known astronomer to build a telescope for the specific purpose of observing and recording celestial bodies. His telescope was about thirty power.

Answer 23

Galileo

(Explanation)

Hans Lippershey invented the telescope in 1608, intending it for use as a military device. Having heard of the discovery of Hans Lippershey, it was in 1609 that Galileo constructed a much improved refracting telescope of his own. He is the first person credited with using the telescope for looking at the stars. With the aid of his telescope, he was able to make keen observations that were recorded in his book Message from the Stars.

Question 24

It was Isaac Newton who formulated the basic laws of modern _________ and showed them to be universal throughout the solar system, applying to the motions of the celestial objects as well as to objects on the Earth.

Answer 24

mechanics

(Explanation)

His greatest contributions in the fields of astronomy, mechanics, optics, and mathematics were conceived by the time he had reached the age of 24.

Question 25

Newton is also often credited with developing the next big development in telescopes in 1668 (about sixty years after Galileo’s first telescope), the __________ telescope.

Answer 25

reflecting

(Explanation)

The reflecting telescope (also called a newtonian telescope) uses a curved mirror instead of a lens. Netwon’s development of the use of mirrors instead of lenses opened the door to development of telescopes of millions of times magnification–far beyond what could ever be achieved with a lens.

Question 26

Newton’s entire system is based on three laws of ______.

Answer 26

motion

(Explanation)

These three laws are:

1. In the absence of outside forces, the momentum of a system remains constant.
2. If a force acts upon a body, the body accelerates in the direction of the force, its momentum changing at a rate numerically equal to that force.
3. Forces are always mutual, thus if a force is exerted upon a body, that body reacts with an equal and opposite force upon whatever exerts the force upon it.

Question 27

In 1905, _______________ published a paper in which he outlined his theory of relativity.

Answer 27

Albert Einstein

(Explanation)

Einstein’s theory was based on two postulates:

1. There is no absolute reference system with which we can measure absolute motions in space. The best we can hope to measure is the relative motion of one object with respect to another.
2. The speed of light, with respect to all observers, is always the same.

Question 28

The __________ circumference of the Earth is 24,900 statute miles.

Answer 28

equatorial

(Explanation)

The Earth is not quite perfectly spherical. Along the Earth’s equator one degree is about 60 nautical miles and a nautical mile is 1.1516 statute miles. The formula for figuring the circumference is 360 (degrees in a circle) x 60 (nautical miles in a degree) x 1.1516 (nautical miles in a statute mile).

Question 29

The study of stresses that build up gradually in the crust of the Earth and cause earthquakes is called _________.

Answer 29

seismology

(Explanation)

Energy is often released by slippages along fissures or faults resulting in earthquakes. Some of these vibrations travel along the surface and others pass directly through the interior of the Earth. Seismology is studied through the use of instruments that pick up vibrations and record the activity.

Question 30

______ on the young Earth came from two sources, volcanic eruptions and bombardment by comets.

Answer 30

Water

(Explanation)

Scientists have calculated that the amount of gas that collected to form Earth’s early atmosphere could not have come entirely from volcanic eruptions (also known as outgassing). Numerous impacts by meteorites and comets carried gases and ice, including water, carbon dioxide, methane, ammonia, nitrogen, and other volatiles from elsewhere in the solar system.

Question 31

The ___________ increases about one degree Celsius for every one hundred feet you go downward into the crust of the Earth.

Answer 31

temperature

(Explanation)

As the core slowly cools, conduction gradually transmits heat from the Earth’s interior out through the crust. Cooling of the hot core occurs at a very slow rate.

Question 32

The chemical composition of the Earth’s __________ is mostly nitrogen.

Answer 32

atmosphere

(Explanation)

At the Earth’s surface, the constituent gases are found to be 78 percent nitrogen, 21 percent oxygen, and 1 percent argon, with traces of water, carbon dioxide, and other gases. At lower elevations, variable amounts of dust particles and water droplets are also found suspended in the air.

Question 33

Who built the first reflective telescope?

Answer 33

Isaac Newton

(Explanation)

Isaac Newton built the first reflecting telescope (also called a Newtonian telescope) in 1668. It used a curved mirror instead of a lens. Newton’s development of the use of mirrors instead of lenses opened the door to development of telescopes of millions of times magnification–far beyond what could ever be achieved with a lens.

Question 34

The Earth has a magnetic field similar to that produced by a __________.

Answer 34

bar magnet

(Explanation)

The magnetic poles of the Earth are located near, but not on, the geographical poles: the north magnetic pole has long been in Northern Canada, but its position is gradually changing and appears to be moving towards Siberia.

The origin of this magnetic field is unknown, although it may be connected with the Earth’s rotation and possibly with electrical currents in the Earth’s core.

Question 35

In 1851, a French physicist named Jean Foucault proved that the Earth rotates through the use of a ________.

Answer 35

pendulum

(Explanation)

Foucault suspended a 200 feet pendulum weighing 60 pounds from the domed ceiling of the Pantheon in Paris. He started the pendulum swinging evenly and the direction of swing of the pendulum was recorded on a ring of sand placed on a table beneath its point of suspension. At the end of each swing, a pointed stylus attached to the bottom cut a notch in the sand. After a few moments, the plane of oscillation of the pendulum was slowly changing with respect to the ring of sand, and hence, with respect to the Earth.

Question 36

The _______ effect is any apparent deflection in the motion of a body resulting from the Earth’s rotation.

Answer 36

Coriolis

(Explanation)

Any object moving freely over the surface of the Earth appears to be deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere because of the rotation of the Earth beneath it.

Question 37

The Earth’s equator is a great circle on the Earth’s surface halfway between the North and South _____.

Answer 37

poles

(Explanation)

A great circle is any circle on the surface of a sphere whose center is at the center of the sphere. The equator is such a circle.

Question 38

There is also a series of imaginary great circles that pass through the North and South Poles called _________.

Answer 38

meridians

(Explanation)

These circles intersect the equator at right angles and can be used to specifiy the east-west location of that place.

Question 39

The _________ of a place is the number of degrees, minutes, and seconds of arc along the equator between the meridian passing through the place and the one passing through Greenwich, England (the Prime Meridian), the site of the old Royal Observatory.

Answer 39

longitude

(Explanation)

The measurement for longitude is either to the east or west of the Greenwich meridian from 0 to 180

Question 40

The latitude of a specific location is the number of degrees, minutes, and seconds of arc measured along its meridian starting at the _______.

Answer 40

equator

(Explanation)

Latitudes are measured either to the north or south of the equator from 0 to 90.

Question 41

In denoting positions of objects in the sky, it is often convenient to make use of the _________________, a concept that earlier observers accepted literally.

Answer 41

fictitious celestial sphere

(Explanation)

The celestial sphere can be thought to be a hollow shell of extremely large radius centered on the observer. Coordinate systems, analogous to latitude and longitude can be devised to designate the positions of objects in the sky.

Question 42

By imagining that the meridian of the observer on the Earth is projected upward and outward until it reaches the celestial sphere, it then becomes the observer’s celestial ________.

Answer 42

meridian

(Explanation)

The celestial sphere stays still; it’s the Earth that rotates. As the Earth turns, the observer’s terrestrial meridian moves under the celestial sphere and the stars pass by the observer’s stationary celestial meridian.

Question 43

The ______ is the overhead point along the extension of a line from the center of the Earth up through the observer.

Answer 43

zenith

(Explanation)

The zenith is the point on the celestial sphere that’s directly over our heads at any given time. Together with the horizon, the zenith is used to denote the position of objects in the sky.

Question 44

The _______ is a great circle on the celestial sphere 90 from the zenith.

Answer 44

horizon

(Explanation)

The horizon passes through the center of the Earth and is parallel to the sensible horizon of a given position or the plane of such a circle.

Question 45

A system that is relative to the observer for specifying the position of a star is the __________ coordinate system.

Answer 45

horizontal

(Explanation)

The horizontal coordinate system uses measurements relative to the observer’s horizon, therefore two people standing in two different parts of the world will have different measurements for the same star. The system consists of two measurements–the azimuth and the altitude. The azimuth runs from 0 to 360 and tells the observer what direction to look in, while the altitude tells the observer how high to look.

Question 46

The azimuth runs from 0 to 360 and tells the observer what _______ to look in.

Answer 46

direction

Question 47

The ________ tells the observer how high to look.

Answer 47

altitude

Question 48

The plane in which the Earth revolves is 23.5 different than the plane of the equator and this is called the _________ of the ecliptic.

Answer 48

obliquity

(Explanation)

The ecliptic plane is the imaginary plane defined by the projection of Earth’s orbit (the path the Earth follows around the Sun) onto the celestial sphere.

Question 49

The seasons of the Earth result because the plane in which the Earth revolves does not coincide with the plane of the Earth’s _______.

Answer 49

equator

(Explanation)

The Earth’s axis is tilted from the vertical by 23.5 as it makes its orbit around the sun. The result of this tilt (or obliquity of the ecliptic) is that the Northern Hemisphere is inclined toward the sun in June and away from it in December.

Question 50

The measurement of ____ is based on the rotation of the Earth.

Answer 50

time

(Explanation)

As the Earth turns, objects in the sky appear to move around us, crossing the meridian each day. Time is determined by the position in the sky, with respect to the local meridian, of some reference object on the celestial sphere. The interval between successive meridian crossings or transits of that object is defined as a day and each day is divided into 24 equal parts called hours.

Question 51

The _____ day is the period of the Earth’s rotation with respect to the sun.

Answer 51

solar

(Explanation)

A solar day is one complete rotation of the Earth. There are about 365 days in a year (the time it takes to make one complete revolution around the sun) and 360 in a circle. Therefore, the daily motion of the Earth in its orbit is about one degree.

Question 52

With the development of railroads and the telegraph, it became necessary to establish time _____ for the standardization of time within the nation.

Answer 52

zones

(Explanation)

In 1883, the continental United States was divided into four time zones; Eastern Standard Time (EST), Central Standard Time (CST), Mountain Standard Time (MST), and Pacific Standard Time (PST). In 1884, an international conference was held in Washington, D.C. in which 26 nations were represented. At that conference it was agreed to establish a system of 24 international time zones around the world.

Question 53

To take advantage of the maximum amount of sunlight during waking hours, _______ Saving time was established during the spring and summer.

Answer 53

Daylight

(Explanation)

Daylight saving time is simply the local standard or zone time of the place plus one hour. Thus, on a summer evening, when it would ordinarily get dark at about 8:00 p.m. standard time, it does not get dark until 9:00 p.m. daylight saving time. The practice of having a daylight saving time is not universal–it varies from country to country.

Question 54

An _______ occurs when the geometric center of the sun is above the horizon for 12 hours.

Answer 54

equinox

(Explanation)

An equinox marks the exact moment twice a year when the Earth’s axis is not tilted toward or away from the Sun. The equinox occurs when the sun passes directly over the equator. Equinoxes occur each year, around 20 March and 22 September. The vernal equinox occurs around 20 March and the autumnal equinox occurs about September 23.

Question 55

Life on Earth began about 3.8 billion years ago, initially with single-celled prokaryotic cells, such as ________.

Answer 55

bacteria

(Explanation)

A 3.8 billion-year-old rock, the Isua sediments, found in western Greenland offers the earliest evidence for life on Earth. The evidence for life in these rocks comes from a peculiar chemical signature of living organisms. These rocks were deposited on the surface of an oceanic crust on what was thought to be a deep ocean. Consequently, the Isua sediments are believed to have originally been part of an ancient sea-floor.

Question 56

The natural units of the calendar are the ___, based on the period of rotation of the Earth.

Answer 56

day

Question 57

The month is based on the period of revolution of the ____ around the Earth.

Answer 57

Moon

Question 58

The ____ is based on the period of revolution of the Earth around the sun.

Answer 58

year

(Explanation)

The three units of calendar measure–day, month, year–do not divide evenly into any of the others. The period of revolution of the moon around the Earth is about 27 1/3 days. The period of revolution of the Earth around the sun is 365 days, 6 hours, 9 minutes, and 10 seconds. Those extra 6 hours in our orbit around the sun account for why we have a leap year every four years–to accommodate for the extra day that has accumulated.

Question 59

The week is an independent unit probably invented by man, although its length may have been based on the interval between the _______ phases of the moon.

Answer 59

quarter

(Explanation)

The seven days of the week are named for the seven planets including the Sun and Moon as recognized by the ancients.