My kids and I have been excitedly plugging away at our Big History lessons all summer and fall, although (until now!) I have found no time to chronicle our activities here on the Homeschool PDX blog. I am going to do my best to backtrack to Unit 3 – Stars and Elements, and summarize the activities we did last spring.
Every time we get to a new unit in Big History my first thought is, “This is the most important unit yet!” And that is exactly how I felt the entire time we studied stars and elements. What could be more important that learning about where EVERYTHING originated? And I’m not talking about the Big Bang, which, for all it’s theoretical loveliness, is still incredibly abstract … I’m talking about stars: the furnaces that created all of the elements in our universe, which in turn created all of the “stuff” in our universe, including us.
Yes, we are made of stardust. In fact, everything everywhere is made of stardust. But what are stars themselves made of and how did they come into existence?
3.0 How Were Stars Formed?
Imagine early space: the Big Bang spewed subatomic material in every direction, creating a diffuse “soup” of primordial matter (i.e. mostly gluons and quarks). This period in our universe’s history is lovingly referred to as the Quark-Gluon Plasma Soup by physicists. Eventually, after a long fraction of a fraction of a second, the subatomic material floating within the plasma soup cooled down and started “sticking” together, forming neutrons and protons.
(Side note: protons and neutrons are composed of three quarks each, “held together” by gluons.)
After a big more cooling, this time lasting just under 400,000 years, neutrons and protons slowed down and stuck together themselves, forming the first atomic nuclei.
(Another side note: two of the simplest nuclei are hydrogen nuclei, composed of one proton, and helium nuclei, composed of two protons and two neutrons. This is why the early universe was teaming with hydrogen and helium nuclei, and why 70% of matter in the universe is still in the form of hydrogen.)
Eventually, after even more cooling, electrons got into the mix, triggering the formation of our universe’s simplest atoms – yep, hydrogen and helium 🙂
Now, that is just my quick layman’s rundown of where it all began – for a more detailed breakdown of quark-gluon soup dynamics and the development of the early universe you can check out this dense but fascinating article, or you can check out this equally dense but more easily digestible time frame of the early universe.
Now let’s talk about stars. How did they start forming?
Spacetime, the fabric of our universe within which the first atoms formed, had slight variations in its structure. Rather than being perfectly uniform in all directions, there were areas where gravity, pressure and temperature fluctuated. These slight variations were critical to the formation of stars. Had the early universe been absolutely uniform, stars would not have formed, elements would not have been made, and we would not be here.
In order to understand this. think about making your bed. You smooth out your top sheet as much as possible, eliminating every wrinkle within sight. It might look like you have made it absolutely flat and even … but of course you haven’t. If you zoom in and look at your bedsheet from a magnified perspective, you will notice tiny ridges and valleys – places where the sheet does not lay flat but instead dips and rises.
The valleys in the bedsheet are analogous to valleys in the fabric of spacetime. Slight imperfections, originating at the moment of the Big Bang and becoming more pronounced as the universe expanded, created an uneven spacetime “surface”.
As the universe slowly cooled, atoms begin pooling into these uneven dips – these dimples of increased gravity. Hydrogen atoms began smooshing themselves next to other hydrogen atoms, congregating in small spacetime valleys. The more atoms that gathered in a particular gravitational dip, the greater the gravitational force became in that location and the more atoms that would consequently fall in. In this way, huge balls of hydrogen and helium gases began to take shape. These “balls” of gas are called interstellar molecular clouds, or stellar nebula.
As the interstellar clouds grew larger, their centers’ became hotter. This tremendous increase of heat and pressure caused nuclear fusion reactions to occur. Nuclear fusion is when nuclei fuse together – in this case, hydrogen atoms fused together to create helium – and release energy in the form of electromagnetic radiation in the process.
Since there were millions upon millions of nuclear fusion reactions happening all at once, streams of electromagnetic radiation (i.e. photons) started flowing out of the cores of these molecular gas clouds. Eventually, these photon streams reached the gas clouds’ surfaces and escaped.
What were these photon streams? You got it – light. All at once, light sources were everywhere. The universe literally lit up.
Stars had been born.
Activity #1 – Star Formation Paper Plate Project
The first activity we did was a simple art project to illustrate nuclear fusion. It entailed making tissue paper balls out of red and yellow paper. The red balls represent hydrogen and helium, and the yellow balls represent photons. As soon as a a decent amount of red tissue paper balls are glued into the middle of the plate, yellow photon balls are added to illustrate the immersion of light from the dense pile of hydrogen and helium.
- tissue paper in 2 or 3 colors (we used red and yellow)
- Elmer’s white glue
- white paper plates
- scissors (optional)
- Yellow marker
Step 1 – Designate one color to be hydrogen and helium and the other color to be photons. (You are welcome to use separate colors for hydrogen and helium, just be sure to create more hydrogen balls than helium balls). Tear or cut the tissue paper into smallish pieces, approximately 2″x2″.
Step 2 – Roll the tissue paper squares into tiny balls.
Step 3 – Glue the tissue balls to the plate. Hydrogen and helium should be in the middle of the plate in a dense “cloud” (if you are using separate colors, be sure to glue down more hydrogen balls than helium balls to accurately represent the distribution of elements). Photon balls should be either streaming out of this cloud, surrounding it, or somehow representing light being emitted from the center of the dense gas.
Step 4 – My kids chose to accentuate their newly formed stars by drawing yellow photon streams around the edge of their paper plates.
The plates my kids made are pictured below (in the middle, high up on the wall) and you can see how my 10 and 7 year olds chose different ways to represent nuclear fusion. This was a simple, hands-on project and we all enjoyed it. My 3 year old did it as well (in fact, I came up with the idea because it seemed right up her alley) although her plate ended up migrating out of the schoolroom and is probably sequestered in her bedroom somewhere 😉
Activity #2 – Understanding the Non-uniformity of Spacetime
Next, I came up with this simple way to demonstrate how hydrogen and helium gather in the valleys of spacetime, creating denser, hotter areas in the interstellar space medium (i.e. star nurseries) that eventually lead to star formation.
I adapted this idea from something I read about stretching plastic wrap over a hulla-hoop in order to create a spacetime surface. Since we are very careful about minimizing our plastic use, I decided to try using a blanket instead. It worked just fine for my purpose, which was to convey the concept that there are nonuniform regions in the fabric of spacetime.
Our supply list was short and sweet:
- Flat surface
- Something small and roundish to drop – marbles, counting bears, etc.
I chose a large, flat ottoman covered in a blanket to represent spacetime. We flattened the blanket out with our hands as much as possible. Then we used my preschooler’s bin of counting bears to represent hydrogen and helium atoms. Pouring it from a few feet above the ottoman, we observed how the bears (I mean hydrogen and helium) fell, then rolled or slid into dips in the blankets where denser groups of atoms had already landed.
We did this a few times to get a sense of how the first groups of atoms that fall create bigger dips in the spacetime fabric that then attract more atoms.
Ultimately, large groups of bears collected in some areas but not others, increasing the valleys in the blanket. It was easy to see that had we had a limitless supply of hydrogen and helium bears, huge groups would have formed in certain locations but not others.
I feel like my kids got a lot out of this simple demonstration … we’ve played around with versions of it for months now, really solidifying the concepts of gravity, density, and star formation.
We covered so many topics in this unit that I don’t want to rush through them in one blog post, so I will continue Unit 3 – Stars & Elements in my next post, beginning with the life cycle of stars.
Thanks for reading! And please be sure to follow the blog if you’d like updates on the rest of our BHP activities 🙂