Solar System Homework
How fast does light travel? What is a light-year?
Light travels 300,000 kilometers per second. A light-year is the distance that light takes to travel in one year, which is approximately ten trillion kilometers.
What is precession, and how does it affect the sky that we see from Earth?
Precession is a gradual wobble that alters the orientation of Earth's axis in space. This changes our sky at night every 26,00 years by pointing to a different star (or no star at all).
Define astronomical unit, ecliptic plane, and axis tilt. Explain how each is related to Earth's rotation and/or orbit.
The Astronomical unit, or AU, is the Earth's average orbital distance, which is roughly 150 million kilometers. The ecliptic plane is the Earth's orbital path in a flat plane. The axis tilt is connected to the ecliptic plane by definition, and is 23 1/2 degrees from a line perpendicular to it.
Describe at least one way to put the scale of the Milky Way Galaxy into perspective and at least one way to put the size of the observable universe into perspective.
The Milky Way can be explained as being the size of a football field, with our galaxy being centered over midfield and our solar system as a microscopic dot around the 20-yard line. The observable universe can be put into perspective by thinking about how many grains of sand there are in all the beaches in the world, which would be comparable to the number of stars there are in the observable universe.
Why don't we see an eclipse at every new and full moon? Describe the conditions needed for a solar or lunar eclipse.
The moon's orbit is slightly inclined to the ecliptic plane. For an eclipse will only happen if the phase of the moon must be full or new, and must occur during one of the periods when the nodes of the moon's orbit are aligned with the sun and earth.
what do we mean by the observable universe? Is it the same thing as the entire universe?
The observable universe is the part of the universe that we can see currently. It is not the same thing as the entire universe, which may have light which hasn't reached us yet.
Photographs of distant galaxies show them as they were when they were much younger than they are today. True or False?
This is true, galaxy's shown in pictures today are much younger than actual today due to the light being shown as it was in the past.
The star Betelqeuse is about 425 light-years away. If it explodes tonight, what will happen?
We won't know about it until 425 years from now because we won't see the light that it creates until 425 years have passed, which is the time it would take for light to travel the distance from the star to the Earth.