Properties of Light/Solar System

Question 1

A speed of 186,282.397 miles per second is called the speed of ___________.

Answer 1

Light. The speed of light is the highest possible speed and universality of the observed speed is one of the postulates of the theory of relativity.

Question 2

The fact that the speed of light is finite means that the deeper into space we look, the further back in _______ we are seeing.

Answer 2

Time. Looking far into space is actually looking back in time. That’s because the light that is reaching our telescope left its origin a long time ago. For instance, if we’re looking at a galaxy 10 billion light years away, that light took 10 billion years to reach us–we’re looking back in time 10 billion years!

Question 3

The ____________ to a surface is simply a line or direction perpendicular to that surface at that point.

Answer 3

Normal. This term is used when discussing the laws of optics and visible light.

Question 4

The law of ______________ describes the manner in which light is reflected from a smooth, shiny surface.

Answer 4

Reflection. If light strikes a shiny surface, it must make a certain angle (the angle of incidence) with the normal to the surface at the point where it strikes. The angle it forms with the normal to the surface as it reflects is the angle of reflection.

The law of reflection states that the angle of reflection is equal to the angle of incidence, and that the reflected ray lies in the plane formed by the normal and the incident ray (in other words, all three line up)

Question 5

The law of ______________ deals with the deflection of light when it passes from one kind of transparent medium into another.

Answer 5

Refraction. Every transparent substance can be characterized by its index of refraction, a measure of the degree to which the speed of light is diminished in passing through it. Whenever light passes from a medium having one index of refraction into a medium having another index, it is always bent or refracted at the interface between the two media. The image below illustrates the refraction of light as it passes from air through glass and then back to air.

Question 6

_____________ of light is the manner in which white light, which is a mixture of all wavelengths of visible light, can be decomposed into its constituent wavelengths or colors when it passes from one medium into another. The beam of light is spread out or dispersed.

Answer 6

Dispersion. The phenomenon of dispersion occurs because the index of refraction of a transparent medium varies slightly for light of different wavelengths. Whenever light is refracted in passing from one medium into another, the violet and blue light of shorter wavelengths is always bent more than the orange and red light of longer wavelengths. Nature provides an excellent example of the dispersion of light in the production of a rainbow.

Question 7

The _________ is the Earth’s nearest celestial neighbor and its only known natural satellite which accompanies the Earth in its annual revolution about the sun.

Answer 7

Moon. Although the moon shines only by reflected sunlight, it is nevertheless the second most brilliant object in the sky.

Question 8

The approximate _____________ from the center of the moon to the center of the Earth is 238,857 miles.

Answer 8

Distance.

Question 9

The surface of the moon is covered with ___________ of varying shapes and sizes.

Answer 9

Craters. Some of these craters were named “seas” during early observations as they were assumed to be large bodies of water. However, the lunar “seas” are craters of different sizes, shapes, and textures.

Question 10

_____________ occur whenever any part of either the Earth or the moon enters the shadow of the other.

Answer 10

Eclipses. When the moon’s shadow strikes the Earth, people on Earth within that shadow see the sun covered by the moon, or a solar eclipse. When the moon passes into the shadow of the Earth, people on the night side of the Earth see the moon darken, or a lunar eclipse.

Question 11

The _________ ___________ consists of the sun and a large number of smaller objects gravitationally associated with it.

Answer 11

Solar system. Almost 99.9 percent of the matter in the system is the sun itself. The smaller objects that comprise the remainder of the solar system include planets, their satellites, the comets, the minor planets or asteroids, the meteoroids, and an interplanetary medium of very sparse gas and microscopic solid particles.

Question 12

The sun is a typical _______, a great sphere of luminous gas, which practically is the solar system.

Answer 12

Star. The sun is composed of the same chemical elements that compose the Earth and other objects of the universe, but in the sun, these elements are heated to the gaseous state.

Question 13

The visible part of the sun is 864,000 __________ across.

Answer 13

Miles. This distance is 109 times the diameter of the Earth.

Question 14

Most of the material of the solar system that is not part of the sun itself is concentrated in the __________.

Answer 14

Planets. In contrast to the sun, the planets are small, cool, and solid. They give off no light of their own, but shine only by reflected sunlight. All of the planets revolve around the sun in the same direction.

Question 15

The ______________ of the planets are the next most prominent members of the solar system.

Answer 15

Satellites. A satellite is a body that revolves about a larger one, such as a moon of a planet. Only Mercury, Venus, and Pluto do not have known satellites. Jupiter has sixty-three, Saturn has sixty, Uranus has twenty-seven, Neptune has thirteen, Mars has two, and Earth has one.

Question 16

There are a great number of small solid objects orbiting the sun that are too small to observe with telescopes called ________________.

Answer 16

Meteoroids. These small objects often plunge through the Earth’s atmosphere and heat with friction until they vaporize. These are commonly known as “shooting stars”.

Question 17

A meteoroid that can survive its flight through the Earth’s atmosphere and land on the ground is called a _____________.

Answer 17

Meteorite. Many of these meteorites can be seen in museums. The largest known meteorites have masses of about fifty tons and a chemical analysis reveals them to be formed of the same elements that exist on Earth.

Question 18

________________ dust and gas is a sparse distribution of micrometeorites and atoms or electrons of gas throughout the solar system.

Answer 18

Interplanetary. Individual particles have been detected as they strike rockets and collectively, the particles can be observed by the sunlight they reflect. Evidence of interplanetary gas also comes from space probes whose instruments have recorded rapidly moving atoms and charged atomic particles.

Question 19

____________ is the planet nearest to the sun and has the shortest period of revolution about the sun, 88 of our days.

Answer 19

Mercury. Mercury is the smallest of the planets and has a diameter of only about 3,000 miles. The lighted side of Mercury has a temperature of about 610° K (640° F), hot enough to melt tin and lead. The dark side of the planet is too cold to radiate a measurable amount of heat.

Question 20

Named for the goddess of love and beauty, _________ is sometimes called the “Earth’s sister”, for it is most like the Earth in mass and size of all the planets.

Answer 20

Venus. Mercury and Venus are the only planets in our solar system that have neither rings nor moons.

Question 21

________ is sometimes called the “newspaper planet” as it is the most favorably situated of the planets for observation from the Earth.

Answer 21

Mars. Mars has a thin atmosphere which is composed almost entirely of carbon dioxide (95%). The surface of Mars has many signs that the planet may once have had an abundance of water, which would indicate that at one time it had a much thicker atmospher. Due to the thinness of its atmosphere today, any water on the surface would instantly vaporize.

Question 22

Named for the leader of the gods, ___________ is the largest and most massive object in the solar system next to the sun.

Answer 22

Jupiter. Jupiter has 63 known satellites.

Question 23

The unique ring around __________ makes this planet one of the most impressive telescopic objects.

Answer 23

Saturn. Saturn is the second largest planet. It is named for the god of seed sowing, the father of Jupiter. Saturn has sixty known satellites.
Galileo first saw the rings of Saturn, but was unable to discern them clearly with his crude telescopes. In 1655, Huygens was able to describe their true form. The rings have the appearance of the brim of a straw hat surrounding the planet at its equatorial plane.

Question 24

The largest moon of Saturn and one of the largest moons in the solar system, ________ is larger than Mercury and Pluto.

Answer 24

Titan. Titan has a planet-like atmosphere which is denser than Earth’s atmosphere, which has made it very difficult to look at the surface. Recent missions to Titan have revealed that methane in liquid form rains from the skies and even forms stable bodies of liquid on the surface–the only place in the solar system other than Earth where stable bodies of liquid are known to exist.

Question 25

Discovered accidentally on March 13, 1781 by William Herschel, _____________ was studied for several months and found to be a new planet.

Answer 25

Uranus. Uranus has twenty-seven satellites and is named after the father of Saturn. It is the coldest planet in our solar system. It has an extreme axial tilt of 98 degrees, meaning that while the rest of the planets are closer to an upright position, Uranus is laying on its side.

Question 26

Whereas Uranus was discovered quite by accident, ____________ was found as the result of mathematical prediction.

Answer 26

Neptune. Through mathematical calculations and observance of the orbit of Uranus, it was determined that there was another planet that was affecting the angle of its orbit. Knowing where and when to look for this new planet was based on the calculations of John Couch Adams and Sir George Airy.

Question 27

While originally classified as a planet, __________ is now considered the largest body of a distinct region in the solar system called the Kuiper belt.

Answer 27

Pluto. It is composed primarily of rock and ice and is relatively small. From its discovery in 1930 until 2006, Pluto was classified as the ninth planet. However, the discovery of many similar objects in the outer solar system changed Pluto’s classification to that of a dwarf planet and it was numbered as a minor planet.
Note that that same region on the outer edges of our solar system is where comets are thought to be born.

Question 28

In medieval Europe, ___________ were usually regarded as poisonous vapors in the Earth’s atmosphere and as bad omens, making them the most superstitiously feared of any astronomical object.

Answer 28

Comets. Comets slowly shift their positions in the sky from night to night, remaining visible for periods that range from a few days to a few months and appear at unpredictable times.

Question 29

The calculations relating to the orbits of comets led to the discovery by Edmund ____________ that the same comet could be returning at intervals of about 75 or 76 years.

Answer 29

Halley. While Mr. Halley’s life did not extend long enough for him to verify his discovery, his calculations were used and his predictions confirmed. The comet was named Halley’s Comet in honor of the man who first recognized it to be a permanent member of the solar system. Subsequent investigation has shown that Halley’s comet has been observed and recorded on every passage near the sun at intervals of from 74 to 79 years since 240 B.C.

Question 30

It is believe that most comets are members of the solar system and that they travel on elliptical _________, most of which are extremely long and have high eccentricity near unity.

Answer 30

Orbits. The orbits of comets are oriented at random in space. A comet can be observed from the Earth only when it traverses that end of its orbit where it passes close to the sun.

Question 31

The head of a comet is made up of two parts–the nucleus and the ______.

Answer 31

Coma. The nucleus is primarily made of ice and dust. For this reason, it is often compared to a “dirty snowball.” The coma is the diffuse gaseous component of the head of a comet. As a comet approaches the sun, the coma usually grows in brightness, but sometimes it becomes so diffuse that it disappears. As they approach the sun, many comets develop tails of gas and dust that extend for millions of miles away from the head.

Question 32

An _____________ is different from a comet in that it doesn’t have a coma or a tail.

Answer 32

Asteroid. This difference is caused by the composition of the two objects–a comet is made up of ice and dust, which have the potential to heat up and form a coma and tail, while an asteroid is solid rock.

Question 33

Nearly all measurements of astronomical distances depend directly or indirectly on the principle of ________________.

Answer 33

Triangulation. Six quantities describe the dimensions of a triangle: The lengths of the three sides and the values of the three angles. Any three of these quantities in succession around the perimeter of the triangle determine the triangle uniquely. If you have two sides and an included angle or two angles and an included side, you can determine the triangle. Distances can be determined without having to span them directly.

Question 34

The ______________ motion of a star is the rate at which its direction in the sky changes, and is usually expressed in seconds of arc per year.

Answer 34

Proper. This motion is almost always an angle that is too small to measure with much precision in a single year. In an interval of 20 to 50 years, many stars change their directions by easily detectable amounts. The star of largest known proper motion is Barnard’s Star, which changes its direction by 10.25 arcseconds per year.
Just to get an idea of how small the motion is, there are 360 degrees in a circle. An arcminute is 1/60 of a degree, and an arcsecond is 1/60 of an arcminute.