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September 2019

Big History Science 06 – Formation of Stars

High school students were to read Foundations of Astronomy section 10-3 Gas-Star-Gas cycle and Ch 11 Star structure & formation and/or watch the videos for Big History Project Unit 3.0 and the following Crash Course Astronomy videos.

As students arrived for class I had them fill out a moon journal page, starting with today’s date and then stepping outside to view the moon and sketch what they saw.  I also had my telescope set up so students could take a closer look.  I told the students to keep the observation log on their fridge or somewhere they will see it and remember to step out and observe the moon each day.IMG_7478.jpeg

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Photo of the moon taken after class on Sept 24, 2019 with my iPhone mounted on my Skymax 102 telescope.  I used the Moon Phase Photo Maps app on my iPad to identify a few craters.

Once everyone had their first moon observation, I gave a slideshow on star formation, different type of nebula and the life cycle of stars.  You can find a slideshow on the Lives of Stars at the Night Sky Network.  This site has a ton of fantastic resources for astronomy, just use the search window to find activities, slideshows, posters, etc for your topic.

SNFusion1
Nuclear Fusion in Stars Activity

After the slideshow, we did the Nuclear Fusion in Stars activity, also from the Night Sky Network.  In this activity we had a bowl of mini-marshmallows represents protons (Hydrogen nuclei) and a bowl of short pasta representing gamma ray photons.  I asked each student to grab two protons (marshmallows) and asked them what they knew about protons – they have positive charge.  So do two protons want to be close to each other? No!  They repel each other.  For two protons to undergo nuclear fusion they must be traveling very fast and collide just right, and when they do they release energy in the form of gamma radiation. At this point everyone squishes their two marshmallows together and grabs a piece of pasta to represent the gamma photon that was released.  We’ve now made a helium atom (2 protons) and need to make two more.  One you have 3 helium atoms you squish two of them together, producing another gamma photon and then the last helium nucleus fuses with the 4 protons so that you now have 6 protons in your nucleus, which means you made carbon.  I mentioned that we didn’t make lithium (3 protons) because its not stable and falls apart almost immediately, which is why stars are mostly H and He.   Protons do not undergo nuclear fusion with every collision, most collisions just send them flying off in different directions. But at the high temperatures and densities inside a star,  the number of collisions is very high, so even though only a small percentage of the collisions end in fusion, its still a ridicuously high number of events per second (10 38 )!

The second activity, a Star Scale Model,  is one I found on Astronomy Professor Kate IMG_7468Follette’s website.  Students are given a table of 25 of the closest star systems to our sun, with the type of star, its distance and position (right ascension and declination).  A second table has the ballon specs for each type of star,  for example if the star is an M type then they need to blow up a red balloon so it has a radius of 2.5 inches.   I didn’t have enough red balloons for all the M stars so we substituted circles of red paper of the appropriate size.  This entire activity could be down with paper circles instead of balloons.  We divided up the list of stars so each group of students made 6 to 7 stars and then came the hard part…. figuring out where to put them.

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Wikipedia: Right ascension (blue) and declination (green) as seen from outside the celestial sphere 

 The farthest stars are 12 light years away. We used 1ft = 2 ly, so all the stars should be within 6 feet of our sun (a star shaped toy in the middle of the room).  To figure out right ascension (R.A.) for each star, I placed signs at four points around the room 0/24 hours, 6 hr, 12 hr, 18hr.  If a star is 4 ly from our sun with R.A. 14:29 hr then the students would place the star 2 feet from the ‘sun’ about half way between 12 and 18 hr.   We didn’t worry about declination since we didn’t have an easy way to suspend the stars (ballons) in the air.  The activity sheet has a number of questions that we answered as a group and everybody made a histogram of the star type distribution.

Lastly we did the Causation – Star Formation Part 1 activity from the Big History Project Unit 3.0.  The activity has a causal map, showing the causes and effects for star formation.  The map is complete with the exception of one circle, the trigger for star formation, which students filled in.

IMG_7493The middle school class also started with the moon observation page, the slideshow on star formation and nuclear fusion with mini-marshmallows.  But instead of doing the entire Star model from scratch, I handed them balloons already labeled with one of the star names and they had to look it up on the table and figure out where it would go in our model.   I also had them put together a Life Cycle of a Star from an interactive notebook, Astronomy & Space Science by Nitty Gritty Science that I bought on TeachersPayTeachers.com.  The yellow sheet in the photo above has a one page description of the life cyce of a star that goes with the diagram they made.

 

 

Big History Science 05 – Fieldtrip & Gravity

CWSF0379Over the weekend, my students and I took a private tour of the Lick Observatory on CWSF0309.jpgMount Hamilton.  We got to see a couple different telescopes, hear about the research they’re involved in, and learned about the life of James Lick.  Unfortunately, clouds were rolling in and the humidity was too high to use the big telescope for viewing (don’t want condensation on the optics).   But I was able to set up  my  telescope (outside the dome in the photo above) so everyone got to see Saturn and Jupiter before we had to head down the mountain.   It was actually pretty dark when the above photo was taken, that is the Milky Way appearing vertically by the dome and an airplane trail crossing over the dome.  I highly recommend taking a fieldtrip to a local observatory if you have one in your area.

Instead of lecturing on the force of gravity this week, I had the high school students use a physics simulator at the Physics Classroom website to figure out for themselves how the force of gravity depends on the distance between objects and the mass of the objects. Screen Shot 2019-09-17 at 1.08.05 PM They have an activity sheet you can download that steps you through this activity.  By moving the sliders you can change the mass of the moon and the planet, or you can move the moon closer or farther from the planet. This interactive works on smart phones and tablets as well as laptops.

Students set the masses and then recorded the Force at different distances.  The handout does not require a graph, but I had them make a graph of their data.  One student used a graphing calculator to do a best fit to his data and found that the force depends on 1 over the distance squared.Screen Shot 2019-09-17 at 12.51.05 PM

Students then kept the distance fixed and changed one of the masses and found that the force of gravity depends linearly on mass.IMG_7398

I also set up a demo that demonstrates how massive objects curve space-time by stretching a large piece of spandex-like fabric over a hula-hoop and then balancing it on chairs to keep it level.  When a large marble is place in the center the fabric stretches and curves the fabric (space-time)IMG_7408.jpeg

The larger the mass, the more the fabric is curved.  Students took turns making smaller marbles orbit the large marble.  We also increased the ‘mass’ of the ‘star’ in the middle by pulling down on it from below.   I also talked about LIGO and how they’re measuring the vibrations on the fabric of space-time, which are gravitational waves.  Here are videos on the subject.

Students were to read Chapter 5 Gravity in Foundation of Astronomy and watch the following Crash Course Astronomy this week.

We also did the How Do We Know What the Milky Way Looks Like? Activity from the Big History Project Unit 2 under Other Material.  Since we can leave the Milky Way galaxy, the images that we see of it are not photographs but artists renderings based on what we can infer from our observations.  Students were asked to pretend that they had never seen the outside of the building we were in and to write down a description of the house using only information they could gather from inside.  They also had to write down what they could tell about about an ancient group of people from just a few photos of archeaological evidence.

The middle school class did the same activity sheet on gravity using the website but I started the class with a presentation on Newton’s Laws, the difference between speed and velocity, acceleration, forces and gravity.  I skipped the presentation with the high school class since many of them had taken physics with me already.  I did not require the middle school students to graph their data, but sketched the graphs on the white board.  We also did the BHP How Do We Know What the Milky Way Looks Like? activity and played with the fabric of space-time.

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Big History Science 04 – Changing Views

This week we’re discussing Big History Project 2.2 & 2.2 and Chaper 4, Origins of Astronomy in Foundations of Astronomy.  I gave a presentation on how our view of the universe has changed over the last few thousand years, starting with the geocentric (earth-centered) view of the ancient Greeks and their various attempts to explain the wandering of the planets (retrograde motion).  Most of these early models were wrong, but at least they were making attempts to explain their observations, and their observations became better and more systematic.  Copernicus finally published his heliocentric (sun-centered) view of the solar system in 1543 just before he died.  It wasn’t widely accepted but it influenced the scientists that followed, Kepler, Galileo and Newton.  Here are some videos about our changing view of the universe.

And I have to include this rap battle.

Here’s a playlist on youtube made for BHP unit 2 by another homeschooler (Homeschool Playlists) if you want more videos.

We did three activities in class, the main one involving Kepler’s laws and a planetary orbit simulator (click on image below).  The simulator uses flash so students had to take turns using the one computer in class and worked on the other two activities while waiting for the computer.  The simulator lets you change the semimajor axis (a) and eccentricity (e) of the ellipse representing an orbit around the sun.  It makes exploring Kepler’s 3 laws fairly painless and the website has a handout that walks students through the lab.

Planetary Orbit Simulator (NAAP)
The second activity is based on the BHP 2.1 Activity, Scale – Changing Views Timeline.  Instead of doing the timeline I printed out a sheet with 9 images of the astronomers discussed today and 9 descriptions of said scientists and their work.  Students had to cut them out and put them together.

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Lastly, I handed each group of students a set of Discipline cards from BHP 2.2 Disciplines – What Do you Know? activity.  Students were to put together a team of 3 people for a mission to Mars to determine if its possible for humans to live there.  This activity is mainly to get students to think about different disciplines and think about the different information and expertise that would be needed for such a mission.

IMG_7143.jpegI did not do the planetary orbit simular or worksheet with the middle school class, instead they drew ellipses using two tacks and some string.  Once they had drawn an ellipse, they measure the semi-major axis and c, the distance from center to one of the tacks (focus) and calculated the eccentricity, e = c/a.   The middle school class also did   the lift the flap page for the scientists and came up with teams for the mission to Mars.   They spent quite a bit of time discussing and debating what they would require and who they should send to Mars.  The activity sheet said to only give them a subset of the discipline cards, but I gave them all of them.

Next week we finish BHP Unit 2.

 

Big History Science 03 – The Expanding Universe

We started BHP 2.0 The Big Bang this week.  Students watch videos and read articles from BHP at home.  Those who want to dig deeper into the astronomy can also read Chapter 17 Cosmology in Foundations of Astronomy.    I started class with a slideshow about cosmology, redshift/blueshifts and the expansion of the universe.    I had originally planned on just doing the Big Bang Balloon from BHP 2.3 but while putting the slideshow together I found this great lab, The Incredible Expanding Rubber Band.   You can download a pdf version from links at the top of her page.  Students take a rubber band (cut so its no longer a loop) with 7 marks on it and measure the distance of those marks from the first one – with the rubber band relaxed.  Then they stretch the rubber band so that the distance between the first two marks doubles – if it was originally 1 cm, they stretch it until its 2 cm.  Then they record the position of all the stretched marks.  IMG_6994

Students find the change in the distances and then the speed (change in distance divided by 2 seconds, the time we’re assuming it took to stretch the rubber band).  They will see that the marks farther away from the starting point have moved farther and the speed is also greater…. just like galaxies that are farther away from us have a bigger redshift and are moving away from us at a faster rate.  Plotting the speed as a function of the original distance gives the students a linear graph (or at least it should) and the slope is equivalent to the Hubble constant for the rubber band universe.   If you take one over the slope you have a time, the ‘age’ of the rubber band universe or the time it took for to expand from a size of zero to the relaxed length at the beginning of the lab.

This was a nice lab, data is easy to take and the math involved is pretty simple but the graph provided in the hand out is blank so students had to figure out which parameters to graph and what scale to use on the graph paper.  They also got some practice with finding the slope.  The handout and website by Michele Stark go through an example set of data making it pretty easy for students to follow along with their own data.

IMG_7006Since this lab didn’t actually take very long, I also had the high school class do the balloon universe lab provided by the Big History Project.  Each group blew up a balloon to about 10 cm in diameter and used a sharpie to put 5 dots on it, 1 for the Milky Way galaxy and 4 other galaxies labeled A, B, C, D.  They then measured the distances (with string) from the Milky Way dot to each of the other dots and recorded them in the table.  Then they blew the balloon up a bit bigger and repeated the meaurements and repeated this procedure 2more times so they had a total of 4 sets of measurements.   They should see all the points getting farther away each time the balloon universe expands and the points that started out farthest away from the Milky Way dot moved the farthest with each expansion.

Lastly, I handed out a color printout of the last page of the Narrative and Thresholds activity (BHP 2.0) and the students filled in the Big Bang space with some hashtags that they felt described the first threshold.  I told them to make sure they saved this sheet since we’l be coming back to it as we learn about each threshold.  I did this activity with both the high school and middle school classes.

For the middle school class, I did the same slideshow and demonstrated the expanding rubber band universe but only had them do the expanding balloon lab from BHP.  We also took a look at parallax since we didn’t get to it last week.  Instead of having the students measure the angles, I just had them sketch 4 stars that I placed around the room  while standing on one side of the room and then move to the other side and sketch them again.  The two stars that were on the back wall (blue and yellow)  didn’t really change much, but the two stars that were closer (orange and green) to them moved quite a bit in relation to the back ground stars.  If you were to list the stars from left to right, you’l notice the order of the stars is different in the two photos,  yellow, green, orange, blue when viewed from the left side of the room and  orange, green, yellow, blue when viewed from right side.  Not to mention the green and orange stars appear much closer together in one image than the other.  I explained to the students that by measuring the apparent motion of the stars we can calculate their distance.  Closer stars, like the orange and green ones in the activity, appear to move more than stars that are farther away.

I finished the middle school class with Our Place in Our Galaxy: Size and Distance Scale, an activity you can find on the Night Sky Network website.  This scale model asks the students to imagine our solar system shrunk down to the size of a quarter and then asks, what size is the Milky Way Galaxy on this scale?  Well, the distance from the Sun to Pluto is about 5 1/2 light hours (takes light 5.5 hours to travel from the Sun to Pluto) and the Milky Way is approximately 1000 light years across so its going to be a LOT bigger than our quarter…. 2500 miles, about the distance from one side of North America to the IMG_7048other!  The activity then asks the students how many stars are in the Milky Way (200 billion), and how can we represent them in our model?  I pulled out some millett bird seed and explained that even one of those little seeds was much bigger than most of the stars in this scale model but that’s what we’re going to use.  So what does 200 billion little seeds look like?  Would it fill a shoe box?..a room?  How about a football field, 4 feet deep!!!  Eveyone’s eyes get pretty big at this… that is a lot of bird seed and they finally start to understand the large numbers involved.  To complete our scale model of the Milky Way we have to distribute the stars (seeds) across the Milky Way (North America).  To show how far apart the stars will be, I explained that our nearest star, Alpha Centauri is about 4 light years away, so for our model we’d have to put one bird seed 2 football fields (600ft)  away from our Solar System quarter.  The link to the activity  has resources to print out and a script you can use with your students.

 

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