Astronomy

• Newton’s 1st Law says an object at rest stays at rest, and an object in motion stays in motion unless acted on by a force. Gravity relates because it acts as the force keeping planets in orbit.

  a. Newton’s 1st Law applies to planetary motion because planets stay in orbit unless a force, like gravity, changes their path.

• Mass is the amount of matter in an object, but weight is how much gravity pulls on it. Weight changes on different planets because gravity changes.

• Surface gravity is the gravitational force felt on a planet’s surface. If two planets have the same mass, the one with a larger radius has weaker surface gravity because the distance from the center is greater.

  a. A larger planet has weaker surface gravity because gravity is weaker the farther you are from the planet's center.

• Escape velocity is the speed needed to break free from a planet’s gravity. Bigger planets with stronger gravity need a higher escape velocity.

Unit 4

1. The electromagnetic spectrum is the range of all types of light waves, from radio waves to gamma rays.

a. The parts include radio, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.

b. Wavelength splits the spectrum: long waves like radio are low energy, and short waves like gamma are high energy.

2. A blackbody is an object that absorbs all light and gives off radiation depending on its temperature.

3. Different colors are related to wavelength because shorter wavelengths (like blue) have higher energy and longer wavelengths (like red) have lower energy.

4. A photon is a tiny particle of light that carries energy.

5. Doppler shift happens when light or sound waves change due to motion, like how a car horn sounds higher as it moves toward you.

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Unit 5: Earth

1. Earth is almost a perfect sphere, but it bulges slightly at the equator.

a. This happens because Earth spins, which pushes outward at the middle.

2. Earth’s crust has layers: the continental crust, which is thicker, and the oceanic crust, which is thinner and denser.

3. Scientists believe Earth’s center is hot because of leftover heat from its formation and radioactive decay inside the core.

4. Earth is differentiated because its layers separate based on density.

a. Dense materials sink to the core, and lighter materials stay near the surface.

5. The center of the Earth is hot due to intense pressure and radioactive materials heating it up.

6. Convection currents are the movement of hot, less dense material rising and cool, dense material sinking. They help move tectonic plates on Earth’s surface.

7. Plate boundaries are where two tectonic plates meet.

a. At boundaries, mountains, earthquakes, and volcanoes can form, depending on how the plates move.

8. In subduction, one plate is forced under another plate into the mantle. This creates volcanoes and trenches.

9. Earth’s atmosphere has layers: the troposphere, stratosphere, mesosphere, thermosphere, and exosphere.

a. Ozone is important because it absorbs harmful UV radiation from the sun.

10. Earth’s magnetic field is created by the movement of molten iron in the outer core.

a. It proves convection currents because they power Earth’s internal heat and movement.

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Unit 7: The Moon

1. The Moon’s density is lower than Earth’s because it has no iron-rich core like Earth.

2. The Moon was likely formed when a Mars-sized object hit Earth, and debris came together to form it. Competing theories include it forming separately or being captured by Earth’s gravity.

3. Maria are flat, dark plains on the Moon, while highlands are bright, mountainous areas. Craters are holes from impacts, rilles are channels, and regolith is the Moon’s dusty surface layer.

4. The Moon causes tides on Earth through its gravity, which pulls on Earth’s oceans.

a. Tidal bulging is the ocean stretching toward the Moon, and tidal breaking slows Earth's rotation.

5. The Moon has layers: the crust, mantle, and core.

a. The near side of the Moon faces Earth and has maria, while the far side is covered in more craters and highlands.

• The celestial sphere is an imaginary sphere of stars surrounding Earth. It relates to the Earth's equator as an extension of it into the sky.

• Constellations are groups of stars forming patterns in the sky. The zodiac is a band of constellations around the ecliptic, the path of the Sun. The ecliptic gets its name from the fact that eclipses can only occur when the Moon crosses this plane.

• Rotation is the spinning of a body around its axis, revolution is the orbiting of a body around another, and orbit is the path an object takes around another in space.

• The oddity about the Moon's orbit is its tilt compared to Earth's orbit around the Sun, causing the alignment for eclipses to not occur every month. Lunar eclipses happen when the Earth is between the Sun and the Moon, while solar eclipses happen when the Moon is between the Earth and the Sun.

• The seasons are caused by the tilt of the Earth's axis as it orbits the Sun, leading to varying sunlight distribution throughout the year.

• The moon phases in order are: New Moon, Waxing Crescent, First Quarter, Waxing Gibbous, Full Moon, Waning Gibbous, Third Quarter, Waning Crescent. It takes about 29.5 days to cycle through all the moon phases.

• Eudoxus: Ancient Greek astronomer, created a model for planetary motion.
  Aristotle: Greek philosopher, proposed geocentric model.
  Aristarchus: Greek astronomer, proposed heliocentric model.
  Eratosthenes: Greek mathematician, calculated Earth's circumference.
  Ptolemy: Ancient astronomer, developed geocentric model.
  Copernicus: Renaissance astronomer, proposed heliocentric model.
  Tycho: Danish astronomer, made precise planetary observations.
  Kepler: German astronomer, formulated laws of planetary motion.
  Galileo: Italian astronomer, supported heliocentrism with observations.
  Newton: English scientist, formulated laws of motion and universal gravitation.