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Astronomy Test Unit 1

Terms in this set (39)

Spherical
What is the shape of Earth?
Independent
Variable that changes?
Trials under "normal" conditions
Control trials
Keep all other potential variables
Contacts or controlled variables
we see the round shape of Earth on the Moon during lunar eclipses. We can see boats disappear over the horizon as they sail away from an observer. We have images of Earth from space.
How do we know earths spherical?
About 25,000 miles in circumference.

You can find a distance from the equator to a spot directly north or south from the equator. On the equinox, you can measure the angle of the shadow of an object at this point. Using geometry, you can calculate the circumference of Earth from this.
What is the size of Earth? How do we know?
The crust is the rocky surface. Under that is the mantle. This rock that is under extreme pressure and heat, making this layer somewhat fluid. Beneath that is the semi-molten iron and nickel core of Earth.
Describe the composition of the inside Earth (crust, mantle,
core)
Weathering (wind and water erosion), meteor or comet strikes, and plate tectonics
What processes can change the surface of Earth over time?
Earth's magnetic field
What extends from Earth's poles and protects us from the solar
wind and radiation from outer space?
Earth rotates on its axis every 24 hours. Only half of the planet is facing the Sun at any one time.
Why does Earth experience days and nights?
Earth is tilted on its axis, allowing the Northern and Southern Hemispheres to be facing toward or away from the Sun throughout the year as Earth orbits the Sun.
Why does Earth experience different seasons?
The Moon and the Sun move across our sky at different rates. Depending on where they with respect to one another, we will see different parts of the Moon illuminated by the Sun's light.
Why do we see different lunar phases?
The Moon has very little atmosphere, so there is not very much weathering. The Moon is geologically dead, so there is no tectonic activity going on. Meteor/comet strikes are relatively rare events.
Why hasn't the lunar surface changed very much many years?
The Moon does not orbit Earth on the same plane as Earth orbits the Sun. Thus, the Moon is not always perfectly aligned with Earth during the Moon's full phase to allow for a lunar eclipse.
Why is there not a lunar eclipse every time we see a full Moon?
the most massive object in our Solar System
What is the sun?
The ecliptic
The planets all orbit the Sun in the same plane. What is this plane called?
Solar eclipses happen when the Moon is perfectly between the Sun and Earth
When do solar eclipses happen?
The moon is in its new phase when this happens. Again, since the Moon doesn't orbit in the ecliptic, it won't always be lined-up with the Sun during a new phase.
Why don't we see a solar eclipse every time there is new Moon?
A grouping of stars seen on the Celestial sphere. They were once used for navigation at night.
What is a constellation?
the Zodiac Astronomical Sizes
What are the twelve constellations called that the Sun moves through as we go through each calendar year?
an astronomical unit is equivalent to the average distance between Earth and the Sun.
What is an astronomical unit?
A light year is the distance light travels during a year
What is a light year?
Astronomical units are good for distances within or near our Solar System. Light years are good for larger distances, like the distances between stars or across a galaxy.
In what situations might astronomical units and light years be used in astronomy?
attractive force between all masses. It acts over large distances
Gravity
opposite charges attract; like charges repel. Not seen as important over large distances
Electromagnetic
holds protons and neutrons together in the nuclei of atoms.
Strong nuclear
causes nuclei of atoms to break-down, releasing particles and radiation.
Weak nuclear
Dark Matter
What is the unseen mass causing galaxies to rotate at their edges faster than expected?
Dark energy
What is the force that is causing the Universe to accelerate in its expansion?
the word planet literally means wanderer. Ancient astronomers saw that these bodies moved against the background stars throughout the course of weeks.
How did planets get the name "planets?"
they appear in the ecliptic.
Where can we see the planets in the night sky?
Some planets appear to move from west to east, opposite the motion of background stars. This is retrograde motion. Planets outside Earth's orbit show this kind of motion, because Earth is moving faster than these planets, catching-up to them and passing them
Explain what retrograde motion is and why planets outside of Earth's orbit show this type of motio
Galileo didn't have his own model. His observations with a telescope helped to cement the heliocentric model.
Galileo
used the measurements of Brahe to show that planets orbit the Sun in elliptical orbits. He came-up with the three laws of planetary motion that we still use today.
Kepler
had an early heliocentric model showing the planets had perfect circular orbits
Copernicus
had a geocentric model where everything orbited Earth. Each body orbiting Earth also moved in small circles (called epicycles) in their orbital pathways.
Ptolemy
made very precise measurements of planetary movement from his observatory, which he passed on to Kepler when he died.
Bache
was the first to show that Earth was bigger than the Moon and the Sun was much bigger than Earth. He also showed that the Sun was much farther away from Earth then the Moon.
Aristarchus
was the first to accurately gauge the size of Earth with his geometrical measurements.
Eratosthenes
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