Scientific Method, Theories and Astronomy

• A hypothesis is more tentative and less exact.
• Two major types of data collected in the scientific method are quantitative and qualitative.
• Theories have more supporting data and are more certain than hypotheses.
• The principle of Uniformitarianism: "the present is the key to the past," also known as the principle of uniformity.
• A theory and/or law is more certain and/or has more data to support it.
• The first step in the scientific method is asking questions.
• The discovery that the universe is expanding led to the Big Bang Theory.
• Our galaxy is called the Milky Way.
• A common unit to express the distance between stars is the light-year.
• The Astronomical Unit: Describes the average distance between the Sun and Earth and between the planets.
• The Big Bang Theory helps explain the origin and expansion of the Universe.
• An Astronomical Unit measures interplanetary distance based on the distance between the Earth and the Sun.
• Copernicus first proposed a Heliocentric (Sun-centered) model of the Solar System.
• Isaac Newton developed the concept of gravity.
• Kepler developed three laws of planetary motion.
• Galileo used a telescope to see Jupiter's four largest moons (Galilean moons).
• Ptolemy used epicycles and deferents to describe the apparent retrograde motion of Mars.
• Tycho Brahe collected detailed observations of Mars and other objects for nearly 20 years.
• Planets maintain elliptical orbits around the Sun.

Terrestrial Planets

• Have all of these characteristics:
  • Small and dense
  • Rocky
  • Located in the inner solar system

Jovian Planets

• Have all of these characteristics:

  • Large and gaseous
  • Possess rings
  • Have many moons

• Venus is NOT a Jovian planet

• Asteroids orbit between Mars and Jupiter.

• Kuiper Belt objects and comets formed beyond Neptune's orbit.

• Pluto is a member of the Kuiper Belt.

• Pluto differs from other Kuiper Belt objects like Eris.

• Nuclear fusion within stars requires temperatures over 1,000,000°C.

• Planets that condensed closer to the Sun are richer in heavier elements.

• Hydrogen and helium are the most abundant elements in gas clouds in the Solar System and the Universe.

• Nuclear fusion is when hydrogen atoms combine to form helium under intense pressure and high temperature.

• Hydrogen and helium make up 98% of the universe.

• Uranus is NOT one of the four inner planets.

• The Solar Nebular Hypothesis explains:

  • The formation of planets
  • The formation of the sun
  • The general layout of our solar system

• Terrestrial planets have an iron-rich metallic core.

• Planets are separated into terrestrial and Jovian types primarily based on density.

• All terrestrial planets experienced accretion, meteorite impacts, volcanism, and differentiation early in their history.

• Early Earth's molten phase was caused by accretionary impacts, gravitational compression, and radioactive decay.

• Differentiation is when a homogeneous Earth developed a dense core and a light crust.

• Mars, Venus, and Earth are geologically active terrestrial planets.

• Mercury is NOT currently geologically active.

• Our Solar System contains various planetary objects including:

  • Planets
  • Dwarf Planets
  • Moons
  • Asteroids
  • Comets

• The Universe is approximately 14 billion years old.

• Major planets and the Sun formed simultaneously in a rotating nebular disk.

• Stellar Parallax determines the distance between nearby stars.

• Planets maintain elliptical orbits around the Sun in our heliocentric model.

• Most of the solar nebula material is found in the Sun.

• Jovian planets have a large mass due to a large amount of matter.

• Terrestrial planets have high densities due to their composition.

• Angles associated with stellar parallax cannot be seen visually.

• Terrestrial planets have low densities.

• Pluto is not considered one of the eight major planets.

• The Earth is composed of layers of different thickness and composition.

Mass vs. Density

• Mass is the amount of matter in an object.
• Density is mass divided by volume, in grams per cubic centimeter.
• Weight is the mass under the influence of gravity, which can vary upon location.
• Mars is not one of the giant outer planets.
• Asteroids orbit between Mars and Jupiter.
• Terrestrial planets have an iron-rich metallic core.
• Planets are separated into terrestrial and Jovian based on density.
• Accretion, meteorite impacts, volcanism, and differentiation are common early events for terrestrial planets.
• Jupiter is composed mostly of hydrogen and helium.
• Early Earth was heated by accretionary impacts, gravitational compression, and radioactive decay.
• The Earth's core is made of iron and nickel.
• Iron melts at approximately 2,000°C, leading to planetary differentiation.
• Early Earth heated up due to collisions, gravitational compression, and radioactive decay.
• Differentiation is the process by which a uniform Earth developed a dense core and a light crust.
• The crust is divided into continental and oceanic crust.
• Oxygen makes up a large proportion of Earth's atmosphere, oceans, and crust.
• Iron is the whole Earth’s most abundant element.

Planetary Material Order (Outer to Inner Solar System)

• Ice

• Gas

• Rock

• Metal

• The layer separating the crust from the core is called the mantle.

• Continental crust is "Sialic," rich in silicon and aluminum.

• Earth is the largest terrestrial planet.

• Both Mars and Earth show evidence of water erosion.

• Europa, a moon of Jupiter, has a relatively un-cratered, recent ice-covered surface.

• Mars contains Mons Olympus (Olympus Mons), one of the largest volcanoes in the solar system.

• Uranus is the only planet whose axis of rotation nearly parallels the ecliptic plane.

• Venus is the only terrestrial planet whose rotation is clockwise.

• Both Mars and Earth have ice caps that change in size with the seasons.

• Jupiter is the Largest Jovian planet.

• Mercury, Venus, and Earth are geologically active terrestrial planets.

• Our Solar System contains the following types of planetary objects:

  • Planets, Dwarf Planets, Moons, Asteroids, and Comets.

• Outgassing by volcanoes produced Earth's primitive atmosphere (carbon dioxide, sulfur compounds, and water vapor).

• Chemosynthesis processes chemical nutrients by organic life without sunlight or oxygen.

• Earth developed an oxygen-rich atmosphere via photosynthesis.

• Mercury has essentially no atmosphere.

• Mars has an atmosphere thinner than Earth's.

• Kuiper belt objects and comets formed beyond Neptune's orbit.

• Venus has the densest atmosphere, contributing to its greenhouse effect.

• Io is volcanically active, even more than Earth.

• Only Terrestrial and Jovian planets are major planets in our Solar System.

• Jupiter's Great Red Spot is a large rotating hurricane-like storm.

• Comets are like large, dirty snowballs made of frozen gases and rocky material.

• Pluto was demoted to a Kuiper belt object and an icy, dwarf planet.

Objects in the Solar System

Includes major planets and Kuiper Belt Objects, asteroids, comets, meteoroids, and satellites.

• Kuiper Belt Objects like Pluto and Eris are icy, dwarf planets, and are located in the outer solar system.
• Meteorites are classified as iron, stony, or stony-iron.
• The most abundant meteorite "falls" are stones.
• Stony-iron meteorites:
  • Are made of silicates (silicates rich in iron and magnesium)
  • Metallic iron
  • Nickel alloys.
• Iron meteorites consist of iron- and nickel- alloys or metallic iron and nickel.
• The Moon formed from a collision between the Earth and a Mars-sized body.
• The Moon's composition is similar to Earth's due to this collision.
• An Ejecta Blanket is a uniform, symmetrical pattern made of material ejected upon meteorite impact.
• Lunar highlands are ancient, heavily impacted Mountains called Lunar Terrae.
• Most of the Moon's craters were produced by meteorite impacts.
• Maria lowlands on the Moon are large lava-filled impact craters.
• Most material from the solar nebula is found in the Sun.