Earth and Space Science Final Exam

Summer Solstice

June. Sun’s vertical rats are located at the tropic of Cancer (23 ½ north latitude)

Winter Solstice

December. Sun’s vertical rays are located at the tropic of Capricorn (23 ½ south latitude)

Autumnal Equinox

September. Sun’s vertical rays are locked at the equator (0 latitude)

Spring or Vernal Equinox

March. Sun’s vertical rays are located at the equator (0 latitude)

Lunar Phases

A consequence of the moon’s motion and the sunlight reflected from its surface; full to new: waning (seeing the moon at sunrise means it is waning); new to full: waxing (seeing the moon at sunset means it is waxing)

Synodic Month

cycle of the phases; takes 29 ½ days; difference between sidereal and synodic is due to earth-moon system moving in an orbit around the sun.

Sidereal Month

True period of the moon’s revolution around earth; takes 27 1/3 days; moon is “tidally locked,” mean it’s period of rotation on its axis is the exact same as its revolution around the earth (27 1/3 days), so same lunar hemisphere always faces earth

Umbra (first understood by Greeks)

Central, completely dark part of a shadow produced during an eclipse

Penumbra (first understood by Greeks)

Portion of a shadow with partial light source being blocked

Geo-centric

Most ancient Greeks believed in an earth-centered view of the universe: earth is a motionless sphere at the center of the universe

Celestial sphere

Part of geo-centric view; a transparent, hollow sphere that turns daily around Earth

Planetai

Part of geo-centric view; Seven heavenly bodies/wanderers including Sun, Moon, Mercury through Saturn (excluding Earth)

Helio-centric

Aristarchus first to propose: sun-centered universe

Retrograde motion

The occasional apparent westward drift that occurs as Earth, with its faster orbital speed, overtakes another planet

Deferents

Part of the Ptolemaic system using a geocentric model (by Ptolemy); large orbital circles 

Epicycles

Part of Ptolemaic system using a geocentric model (by Ptolemy); small circles

Stellar parallax

Sought by Tycho Brahe, who failed to observe it (thus disagreeing with Copernican system); the apparent shift in a star’s position due to the revolution of Earth

Telescope

First astronomical telescope constructed by Galileo Galilei in 1609; helped discover four large moons of Jupiter, planets appear as disks, phases of Venus, features of the Moon, and sunspots

Lookback time

Light travels at a finite speed (300,000km/s); the farther away we look in distance, the further back we look in time (e.g. moon = 1 second, sun = 8 minutes, sirius = 8 years, Andromeda Galaxy = 2.5 million years)

Light-year

The distance light can travel in one year; at greater distances, we see objects as they were when the universe was much younger

Speed

Rate at which object moves (e.g. speed of 10 m/s)

Velocity

Speed and direction (e.g. 10 m/s, due east)

Acceleration

Any change in velocity; units of speed/time (m/s^2)

Momentum

Mass x velocity; a net force changes momentum, which generally means an acceleration (changes in velocity)

Angular momentum

Rotational momentum of a spinning or orbiting object; cannot change unless an external force (torque) is acting on it

Mass

The amount of matter in an object; mass itself is a form of potential energy, and just a small amount of mass can release a great deal of energy

Weight

The force that acts upon an object (e.g. gravity); weightlessness is due to a constant state of free-fall

Escape velocity

If an object gains enough orbital energy, it may escape (change from a bound to unbound orbit); escape velocity from Earth = 11km/s from sea level (or 40,000 km/hr); escape and orbital velocities do not depend on mass

Tidal friction

Gradually slows Earth’s rotation; tides are dependent on the phases of the moon (spring tides: highest tides during new/full moon; neap tides: weaker tides during third/first quarter moons)

Kinetic energy

Motion

Radiative energy

light

Potential energy

Stored

Thermal energy

Collective kinetic energy of many particles; related to temperature (NOT the same); depends on temperature AND density

Terrestrial planet

Rocky, relatively small, and close-to-the-sun planets; inner, rocky, less, inferior (e.g. Mercury, Venus, Earth, Mars); largest to smallest terrestrial planets: Earth, Venus, Mars, Mercury; largest to smallest terrestrial worlds: Earth, Venus, Mars, Mercury, Moon

Jovian planet

Gaseous, larger, and farther-from-the-sun planets; outer, giant (ice of gas), greater, superior (e.g. Jupiter, Saturn, Uranus, Neptune)

Rock-metal condensation line

The temperature is cool enough for rocks/metals to condense

Frost line

Border where anything within is too hot for hydrogen compounds to form ices (where you typically get your terrestrial planets); anything beyond is cold enough for ices to form (where you get your jovian planets)

Planetesimals

Tiny particles that stick together 

Accretion

Process of assembly in which gravity draws planetesimals together to form planets (heavy bombardment)

Differentiation

Gravity pulls high-density material to the center; lower-density material rises to surface; material ends up separated by density

Lithosphere

A planet’s outer layer of cool, rigid rock that “floats” on warmer, softer rock beneath it

What are Kepler’s three laws of planetary motion?

Orbits of planets are elliptical, planets revolve around Sun at varying speed, there is a proportional relation between a planet’s orbital period and its distance to the sun (measured in AU; one AU = 93 million miles)

What is the consistency found in the motion of large bodies in our solar system? What is the exception?

All large bodies in the solar system orbit and rotate in the same direction and nearly in the same plane (except for Venus)

What is a synodic month and how long does it take?

Cycle of the moon phases; takes 29 ½ days

What is a sidereal month and how long does it take?

True period of the Moon’s revolution around Earth; takes 27 ⅓ days

Why is there a difference between synodic months and sidereal months?

The Earth-Moon system moving in an orbit around the sun

What causes the phases of the moon?

Moon’s orbit is elliptical, and the relative positions of the Sun, Earth, and Moon constantly change; the motion of the Moon and the sunlight reflected from its surface

What causes the seasons?

Changing sun angle and length of daylight, as well as Earth’s changing orientation to the Sun (Earth’s axis inclined 23 ½ degrees and always pointing in the same direction)

What causes eclipses? What is the difference between solar and lunar eclipses?

Shadow effects; solar eclipse during new moon (moon’s shadow on earth), while lunar eclipse during full moon (earth’s shadow on moon); for any eclipse to take place, the moon must be in the plane of the ecliptic at the time of new- or full-moon; usual number of eclipses is four per year

What is an astronomical unit and what is equal to one AU?

A measurement for distance from the Sun; one AU is equivalent to 150 million km or 93 million miles, which is the approximate distance Earth is from the Sun

What is the geocentric model of the solar system? Who believed in it? What concepts derived from it?

Earth-centered universe supported by many ancient Greeks including Ptolemy and (to a lesser extent) Tycho Brahe; concepts include the celestial sphere, Ptolemaic system, planetai, retrograde motion, deferents/epicycles

What is the heliocentric model of the solar system? Who first proposed it?

Sun-centered universe; first Greek to profess it is Aristarchus; also believed by Copernicus, Kepler, Galileo

What did Nicolaus Copernicus discover/conclude?

Concluded Earth was a planet and sun was at the center; used circular orbits (NOT: Aristarcus first to discover heliocentric model, but Copernicus rediscovered and added circular orbits)

What did Tycho Brahe discover/conclude?

Could not find stellar parallax and dismissed Copernican system

What did Johannes Kepler discover/conclude?

Planets have an elliptical (not circular) orbit around the Sun; three laws of planetary motion (described previously in definitions)

What did Galileo Galilei discover/conclude?

Supported Copernican theory; constructed first astronomical telescope in 1609 (more detail in above definitions)

What is stellar parallax?

The apparent shift in a star’s position due to the revolution of Earth

How is light-year and look-back time related?

The speed of light (300,000km/s, or 10 trillion km per year/ 6 trillion miles per year) determines how things may appear in the universe; the farther the distance, the further back in time

What is the acceleration of gravity?

All falling objects accelerate at the same rate (not counting friction of air resistance); it is the same for all falling objects, regardless of mass (according to Galileo)

Who discovered laws of motion and gravity?

Isaac Newton

What are Newton’s three laws of motion?

First: an object moves at constant velocity unless a net force acts to change speed or direction; Second: force = mass x acceleration; Third: for every force, there is always an equal and opposite reaction force

What is the Universal law of gravitation?

Every mass attracts every other mass; attraction is directly proportional to the product of their masses; attraction is inversely proportional to the square of the distance between their centers

How does gravity cause tides?

The Moon’s gravity pulls harder on near side of Earth than far side and stretches Earth

What happens to gravitational potential energy  when a (celestial) cloud contracts?

Gravitational potential energy is converted to thermal energy (when there is more gravitational energy, there is less kinetic energy, and vice versa)

What is angular momentum?

Rotational momentum of a spinning or orbiting object (momentum = mass x velocity)

What is the conservation of angular momentum?

Angular momentum = mass x velocity x radius; cannot change unless an external twisting force (torque) is acting on it; explains why planets rotate and orbit the sun and why objects rotate faster as they shrink in radius

How can the orbit of an object change

Friction or atmospheric drag (e.g. tidal friction); gravitational encounter; escape velocity (enough orbital energy to become an unbound orbit)

What is orbital energy?

(gravitational + kinetic); stays constant if there is no external force; cannot change spontaneously

What is the difference between thermal energy and gravitational potential energy?

Thermal energy is a measure of total kinetic energy of particles in a substance (depends on temperature and density); gravitational potential energy relies on mass and strength of gravity; with less gravitational energy, more thermal energy (and vice versa)

What is the Conservation of Energy?

Energy cannot be created nor destroyed, but it can change form/exchange between objects; total energy content of the universe determined by Big Bang and remains to this day

What is galactic recycling?

Elements that formed planets were made in stars and recycled through interstellar space

What is the “flattening” process of a nebular cloud?

Collisions between particles in cloud cause it to flatten into a disk and gradually reduce random motions, as well as up/down motions; spinning cloud flattens as it shrinks (into a disk-like shape)

What serves as evidence for nebular theory of the formation of star systems?

Stars forming in other interstellar gas clouds, observations of disks around other stars

List the compounds within the universe in order of greatest to least.

 (1) hydrogen and helium (98%), (2) hydrogen compounds (1.4%), rocks (.4%), metals (.2%)

What happens between the border of the rock-metal condensation line and the frost line?

The temperature is cool enough for rocks/metals to condense

What happens beyond the border of the frost line?

Temperatures are cool enough for ice compounds to condense

What is heavy bombardment in accretion?

Leftover planetesimals bombard other objects in the late stages of solar system formation

What is the order of density for planet layers?

Rocky crust (lower density), mantle (medium density), metal core (highest density)

How does size affect planet development?

Smaller worlds cool off faster and harder earlier

What is the role of convection in geological activity and where does it occur?

Hot rock rises, cool rock falls (one cycle takes 100 million earth years); occurs in mantle

What is the role of conduction in geological activity and where does it occur?

Transfers heat from hot material to cool material; occurs in crust

What is the role of radiation in geological activity and where does it occur?

Sends energy into space (occurs in space); radioactive decay is most important heat source today

What causes planetary magnetic fields?

Moving charge particles; electrically conducting, convecting, and rotating in planet interior

What does Earth’s magnetosphere protect us from? What can charged particles create?

Protects against charged particles from the Sun; can create aurorae (“Northern lights”)

What causes tectonic forces, and what can happen in tectonic compression/convergence and divergence (one listed example each)?

Convection of the mantle creates stresses in the crust; compression makes mountain ranges, divergence makes valleys

How did the moon form?

A massive object (Theia) collided with early Earth; the debris combined to form the Moon