Chapter 5:
Part 1: Galactic Gives a Quiz
Galactic: “Let’s get to the quiz on my last few lectures. Please write down your answers and then volunteer your answers. Thank you. Let’s begin. What is the hottest planet in our solar system?”
Student: “Mercury.”
Galactic: “Mercury is the closest planet to the sun but it’s not the hottest planet; anyone else?”
Student: “Venus.”
Galactic: “Correct. The next lecture will cover why Venus is the hottest. What is the huge black hole in the center of our galaxy called?”
Student: “Sagittarius.”
Galactic: “Almost, but not quite right.” Anyone else?”
No one answers. “It’s Sagittarius A. Where’s the point of no return where nothing can escape a black hole?”
Student: “At the event horizon.”
Galactic: “Can light escape Sagittarius A?”
Student: “I think so because it travels 186, 000 miles per second.”
Galactic: “It’s great that you know how fast light travels, but it still can’t escape Sagittarius A.”
Galactic: “What’s the mass of Sagittarius A? No one knows the answer? It’s 4.6 million times the mass of our sun.”
Student: “That’s unbelievable. I love this course.”
Galactic: “The universe is amazing. Let’s continue. What happens if two black holes collide?”
Student: “They merge.”
Galactic: “Yes, they produce gravitational waves, merge and become a bigger black hole.”
Galactic: “What kind of galaxy is the Milky Way?”
Student: “A spiral galaxy.”
Galactic: “Correct. It’s a barred spiral galaxy. What’s the name of the galaxy that will eventually collide with ours?”
Student: “Andromeda.”
Galactic: “What’s the closest large Galaxy to the Milky Way?”
Student: “Andromeda?”
Galactic: “Correct. It’s the nearest major galaxy to the Milky Way. It’s 2.5 million light years away from earth. You can see it with the unaided eye. Isn’t that amazing? What shape is Andromeda?” No one answers. “It’s also s spiral galaxy. The larger galaxies are elliptical. “Where’s the asteroid belt?”
Student: “It’s situated past Mars.”
Galactic: “Excellent. What surrounds all galaxies?”
Student: “Dark Matter.”
Galactic: “Getting back to Andromeda, how many stars does it have?”
Student: “Five hundred billion.”
Galactic: “Not even close. “It has one trillion stars almost twice as much as the Milky Way’s estimated two to four hundred billion stars. What’s a planet that orbits a star outside our solar system called?”
Student: “An asteroid.”
Galactic: “No, an asteroid isn’t a planet. Anyone else?” No one answers.
“Exoplanet. Okay, you didn’t do well on this quiz. Please leave your answers on my desk when you leave but first we have an hour left of class. I will lecture on our Solar System.”