By Stacy Palen.

Often, in-class questions are presented as a binary choice: “Does the star grow, or does it shrink?”

I always couch these as, “How many of you think the star grows?" Wait for hands. "How many of you think it shrinks?" Wait for hands. "How many people think that 9:30 in the morning is an unfair time to ask that question?" (Wait for hands.)

The last choice, though it may seem frivolous, is really important.

I try to make these last choices light-hearted and a little bit funny. For example:

• “How many of you were asleep just now?”
• “How many of you were thinking about lunch?”
• “How many of you were thinking about puppies instead?”
• “How many of you wish we would just get to black holes already, and stop talking about nuclear fusion?”

You get the idea. The light humor helps them stay focused and makes it clear that I expect them to put up their hand for every question at some point, even if it’s the silly last choice. I expect them all to participate, every time.

The last choices -- and the way students react, by laughing or groaning, for example -- help me figure out where they are in their heads.  Do I have their attention? Are they feeling confident to take a risk and make a guess? Are they actually listening to me at all? Were they really thinking about puppies?

I often don’t interpret that response in the moment. After class, while I’m walking back to my office and putting my notes away, I’ll think about what was happening in the classroom right at that time when I asked the last question.

Was there a better way to explain before I asked the question? Had I been talking too many minutes in a row? And so on. I might make a note in my lecture notes about a sticky concept, or an analogy that worked particularly well. This reflection afterwards helps me improve for next time.

Most importantly, the last choice gives students an “out.” It is an acknowledgement on my part that they might not know the answer, and that’s OK. I expect them to go ahead and guess sometimes! Giving the last choice makes it clear the question is not a referendum on how smart they are. I am genuinely asking the question because I am trying to figure out what they have understood so that I can help them.

Really, that’s what the last choice question is all about: it’s a less intimidating way for them to say, “I don’t know.”

The last choice helps students to stay focused because they know there will be a moment when they can answer honestly, and often it will come with a laugh.

A closing note on classroom technology: Sometimes I use “clickers." Sometimes I use a piece of paper divided in 4, with A, B, C, D written on each square; students fold the paper to show me the letter of their answer. Sometimes I just have them put up their hands, because the question is an extemporaneous one that just happened naturally in the course of my lecture. In this post, I talk about the questioning strategy as though it applies to extemporaneous questions. But of course, you could use this strategy for a planned questions, too.

By Stacy Palen.

As of this writing, InSight has just landed successfully on Mars!  This mission is a little bit different from other recent missions: InSight (short for Interior Exploration using Seismic Investigations) is a lander, not a rover. Because it’s in the news, this is a great opportunity for a brief in-class discussion!

This illustration shows a simulated view of NASA's InSight lander descending on its parachute toward the surface of Mars. Credits: NASA/JPL-Caltech

InSight is designed to investigate the interior of Mars: the crust, mantle, and core.   

A seismometer will measure surface vibrations, which will be used to determine the size of the core, the thickness and structure of the crust, and therefore the thickness of the mantle as well. These same measurements will be used to measure how frequent and how powerful the tectonics are on Mars, as well as the frequency of meteorite impacts.

Heat flow measurements will be taken using a probe that is hammered 5 meters (16 feet) down into the surface. These measurements will be used to determine the temperature of the interior. All of these measurements will lend insight (ha!) into the formation and evolution of Mars.

Radar soundings back and forth to an orbiting spacecraft will be used to measure the wobble of Mars on its axis, which in turn is affected by the structure and composition of the core.

The InSight lander is the result of many technical advances. It’s the first lander to pick up and place instrumentation from the top of the lander onto the surface of the object being studied.

The plan is for InSight to place its seismometer on the surface of Mars, then place a heat and wind shield directly on top of the seismometer. The lander needs to make these placements autonomously, something that has never been done before.

In another major technological advance, InSight arrived on the Martian surface through a complex series of steps involving parachutes and retrorockets. The successful operation of these kinds of tools is a pre-requisite for future human exploration. Just InSight's successful landing represents a major step forward in the study of Mars.

An artist’s rendition of the InSight lander operating on the surface of Mars. Image Credit: NASA/JPL-Caltech

Discussion questions for students may be wide-ranging:

• How does this mission connect to earlier discussions about the formation and structure of planets? (Hooray for final exam review!)
• Why do we care about the structure of Mars? What implications might a study of the geologic properties of Mars have for future Mars exploration?
• Do you expect the meteorite impacts to be frequent (more than one per day) or rare (less than one per sol)? Why?

And here are some quick “Google It and Think” questions for small groups:

• How long did it take for this mission to get to Mars? What factors determined this “flight” time?  What challenges would humans face due to this travel time on a trip to Mars?
• How many spacecraft, rovers, and landers are currently functioning on Mars? Why is Mars a unique target for missions like these?
• There are three separate stages for the entry, descent, and landing sequence. What are they?  What problems can you think of that might have occurred in each stage? What steps did the engineering team take to make these problems less likely?

By Stacy Palen.

Summary: A red dwarf star in the Milky Way barely contains any heavy elements at all. Its age is estimated at 13.5 billion years.

Article: http://www.astronomy.com/news/2018/11/red-dwarf-is-one-of-the-oldest-in-the-universe.

Questions for Students:

1. Why does the lack of heavy elements imply that the star formed very soon after the Big Bang?

Answer: Because since the Big Bang, stars have been making heavy elements and returning them to the interstellar medium. Young stars have more heavy elements than older stars.

2. Why do astronomers think there must have been at least “one ancestor” before this star formed?

Answer: Because it has some heavy elements in it.

3. How is the birth of this small star connected to the first generation of stars, which were probably ALL very massive?

Answer: Supernova explosions from those first stars could trigger the formation of smaller stars.

4. Where would this star lie on an H-R Diagram?

Answer: This star, because it is a very small red dwarf, would lie at the lower right on a H-R diagram.

5. This star is one-seventh (about 0.15 times) the mass of the Sun. Which of the following is a reasonable main sequence lifetime for a star with that mass?
a. 10 million years
b. 100 million years
c. 1 billion years
d. 10 billion years
e. 1 trillion years

Answer: e.

6. Astronomers can confidently state that all stars like this one (with similar mass) are still around, and none have died yet. Why can they state this so confidently?

Answer: Because 1 trillion years is a lot longer than the age of the universe.