ingridscience

To make a sheet of sugar crystals:
Combine the sugar and water in the heat-proof container. Heat on a stove top to dissolve the sugar, stirring to help the sugar grains dissolve. Be careful not to heat it to much so that it boils over. The sugar solution is very hot, so best if an adult handles it while heating.
Pour into a shallow baking dish, or leave in the container it was heated in. A shallow layer will yield more crystals.
Place in an undisturbed spot. Crystals are seen in two days, a week is best to allow the crystals to grow larger.

The crystals form as the sugar molecules dissolved in the water come out of solution, to form a solid.

Crystals grow down from the surface or up from the bottom of the tray. Chip out a group of crystals and rinse very briefly in cold water to remove the sugary syrup. Allow to dry. Look for the shape of the sugar (sucrose) crystals. They are monoclinic prisms.

To make sugar crystals to eat:
Students will love to eat the crystals that they make. They are pure sugar, so very sweet - only a small amount for a child is needed.
After pouring the hot sugar solution into a baking dish, lay over the mesh. Students write their name on a popsicle stick, then are assisted in lowering the popsicle sticks through the mesh into the sugar solution. Use a clothes peg to support the stick on the mesh.
Crystals will grow on the popsicle stick where it is immersed. The sticks will need to be chipped out of the layer of crystals that form on the top of the sugar solution. Once the syrup is licked/washed in cold water off the crystals, their shapes can be seen quite well.

Tell students that as a crystal grows, the atoms add on in a regular way. Depending on the pattern that the organize in, different shaped crystals are made.
This activity uses building toys to show how a regular arrangement of smaller units can make some common crystal shapes.
When you build, make sure that you add the units in the same repeating pattern (show example).
See which crystal shapes you come up with.

Students model two masses orbiting together. They represent the coupled orbits of two stars (a "binary star system"), or a star orbiting a black hole, or a planet orbiting a star. The movement - the orbit path and speed - of each mass depends on the relative sizes of each object.

Tell students that they will investigate coupled orbits, to discover how orbits and speeds vary with the masses, and then find out how astronomers study couple orbits to discover objects in the universe.

Give students the equipment, ask them to add masses to each end of the skewer. They should try both equal-sized masses, and unevenly-sized masses during their experimentation. They should then make sure the masses are balanced i.e. the skewer is horizontal.
For the masses supported by a post they should find the appropriate hole to put the pin through. For the masses supported by string they can slide the string along the skewer until the balance point is found.
Once the masses are balanced, they can be spun slowly around each other.
Students should note the path that each mass takes and the size of its orbit. For the mass on a post, a flashlight can be shone from a fixed point above the spinning masses, and the path of their shadows traced on the paper.
Students may also look at how fast each of the masses move, but the size of the orbit is the most important.

They should find that the masses both orbit around the balance point (a small mass does not orbit around a stationary large mass, but they both move around another point).
They should find that with unequal masses, the smaller mass has a larger orbit (and moves much faster) than the larger mass.

Astronomers study couple orbits to discover new objects in the universe. If they find a star in orbit with an invisible companion, they can measure the size and speed of the star's orbit to figure out the size of the invisible companion, and therefore what it might be.
If a star is discovered moving in a large orbit around "nothing", the invisible companion may be a (relatively massive) black hole. The black hole has a huge mass which moves very little, while the orbiting star moves in a large, fast orbit around it. The more massive the black hole, the larger and faster the orbit of the star. In the students' model, their large mass is the black hole and their small mass is the star.
If a star is found to be moving in a small orbit (which will be seen as a "wobble" back and forth), the invisible companion may be a (relatively small) exoplanet with a large orbit around the star, that is too small to see itself. In the students' model, their large mass is the star and their small mass is the exoplanet.
(The wobble of a far away star is measured by reading its Doppler shift as it moves away from and towards us.)

Note that with coupled orbits, both masses orbit around a separate balance point, or centre of mass, called a "barycentre". If one mass is a lot larger than the other the barycentre may be within the large object, but it will not be at its centre. The large mass will still make a (small) orbit itself. For simulations of coupled orbits see the gallery near the bottom of https://en.wikipedia.org/wiki/Barycenter
More information on barycentres and discovering exoplanets: https://spaceplace.nasa.gov/barycenter/en/

Coupled orbits can have more than two objects - our solar system is the coupled orbits of the sun, the planets and other bodies that orbit the sun.
Technically, solar system objects, including Earth, are not orbiting the sun, but the sun and all the masses in the solar system orbit the barycentre of the solar system (which is sometimes outside the surface of the sun and sometimes near the centre of the sun). Try this link for the orbit path of the sun around the solar system barycentre:
https://www.researchgate.net/figure/The-orbit-of-the-centre-of-the-Sun-…

Astronomers are searching for "Planet 9" to explain the orbits of the trans-Neptunian objects (objects orbiting the sun beyond Neptune). The apparent location of the barycentre of the solar system cannot be explained by the known objects orbiting the sun, so astronomers are searching for another mass in orbit.
Try Wikipedia entry on Planet 9 for image: https://en.wikipedia.org/wiki/Planet_Nine#/media/File:TNO-Planet9-Diagr…
See NASA webpage on Planet 9 for more information: https://solarsystem.nasa.gov/planets/planetx/indepth

One line summary: astronomers use the phenomenon of coupled orbits to discover black holes, exoplanets and new planets in our solar system.

Before the lesson:
Buy cheap wine glasses. Knock the base off them by tapping the stem just above the base with a metal file or other long, heavy object. Sand down the sharp edges.
Alternatively, use an intact wine glass, but be careful about breakages in the classroom.

Hand out wine glass base lenses, and optionally, other cut glass objects that bend light into interesting patterns.
Hand out paper with printed geometric designs (attachment), and coloured markers for students to make their own designs.
Ask students to move the lenses over the designs and notice how the lenses bend images.
Challenge them to specifically make a circle from a dot. If they need help: slide the wine glass base over the dot until the stem is directly above it, when the dot changes to an arc then a circle.

The wine glass base models how gravitational lensing works. When the wine glass lens is run over a dot, the light from the dot is bent by the lens, so our eyes above the wine class see a circle.
In the same way, astronomers use their telescopes to look for rings of light to discover dense masses in the universe, which can bend light around them. When light from a far away galaxy passes through a nearer black hole or cluster of galaxies, their immense gravity bends the light around them, so that the light that reaches our telescopes appears as an arc, or even a circle.
Try these webpages for images of gravitational lensing of light around black holes or galaxies: https://en.wikipedia.org/wiki/Einstein_ring http://static.ddmcdn.com/gif/blogs/6a00d8341bf67c53ef01630128de99970d-8…

Gravitational lensing images provide information on several astronomical phenomena:
They can be used to map where black holes are.
They can be used to map the dark matter in the universe, which cannot be seen but has enough mass to bend light.
Dark energy existence has been supported by gravitational lensing images.
Cosmic microwave background radiation is also bent by gravitational lensing, so is studied this way.
Galaxy clusters can be weighed with from gravitational lensing images, as the amount of lensing depends on the mass.
Early universe galaxies can be seen and studied with gravitational lensing, which magnifies light images (lensing arc image).

If no tornado connector is available:
Drill out the centre of the caps, then hot glue them together face to face, without sealing over the hole. More hot glue and duct tape will be needed to minimize leaks from the bottles during the activity. Have a towel ready.

Fill one of the bottles with water two thirds full.
Add the optional floating bits.
Add the tornado connector, or the home-made connector, before screwing on the other bottle.

Turn the bottles upside down so that the water is in the upper bottle, hold the bottles tightly at the join and rotate in a large circle to initiate a tornado of water down into the lower bottle. The floating bits will help visualize the rotation of the water through the tornado.

This activity can be used to model several real phenomena including:
1. Black hole accretion discs: the cloud of gas and dust swirling around a black hole form a spinning "accretion disc". Long streamers of gas are pulled into the black hole by gravity, travelling faster as they are pulled in. Although a black hole itself is not visible, the accretion disc around it is.
2. Tornadoes, hurricanes and waterspouts - although note that these swirl upwards not downwards.

Assembling the spectroscope:

Flatten a cereal box.
Image 1:
Draw panels so that the cereal box can be folded into a square tube, using the folds already present (side panels of cereal box may become one or two sides of the spectroscope).
Score folding lines, on the outside of the fold (printed side of the box) all the way across the box. (The brown inside of the box will end up on the inside of the tube, as it is darker and will reflect less light.) Cut all the way through the cardboard when you reach the end tabs.
Cut end tabs at one end of the cereal box, so that they can fold down to close the end (the length depends on the size of the cereal box). Cut off one of the middle tabs, and on same panel, cut a hole (4-5.5cm from end and 1cm wide). This viewing hole is on “the top” of the spectroscope.
Cut the tabs at the other end of the cereal box, so that they fold in to make a narrow slit, 1mm wide, across the box.
Image 2: tabs folded to show the slit (this will be folded last in the assembly)
Fold the cardboard into a tube and tape the long side with duct tape or masking tape. It can be easier to put short pieces of tape in a couple of places first to align the edges before adding the long strip. Tape the flaps closed, leaving the top edge open near the viewing hole.
Image 3:
From the opening near the viewing hole, measure a 60 degree angle from the vertical, on both sides, and mark a line at this angle in pencil.
Image 4:
Cut slits 4cm long along this line. Alternatively, these slits can be cut in the cardboard ahead of time for the students.
Cut a DVD in half (or quarters with smaller cereal boxes) with sharp scissors (less likely that the layers will separate than trying to snap it). Insert the DVD piece into the 60 degree slit, making sure the recordable side (with the grooves) is up.
Check the spectrum is visible before taping the DVD in place: point the slit directly at a light source, then look through the hole at the reflection of the light off the DVD.

Using the spectroscope to look at different light sources:

The spectroscope separates the colours of light. They are seen as a "spectrum".
Students can look at various bulbs in the classroom to see what kinds of spectra they have. Or field trip: visit the local stores and look at their various lights through the spectroscope, to find out what kind they are (a supermarket has a god selection of lights with the fridges, displays and overhead lighting.
Primaries can look for different kinds of spectra (broken or continuous) and the colours (see primary worksheet attached). Intermediates can be challenged to find their own patterns in the spectra.

Expected results:
Viewing an incandescent or LED bulb with the spectroscope will show a continuous spectrum - the colours are all smeared together. Every wavelength of light is emitted by these bulbs. See image 8. LED bulbs of one colour will have continuous spectra within these colours.
A fluorescent bulb will show distinct lines of colour - a broken spectrum. The colour of the lines present depend on the gases inside the fluorescent bulb (often mercury and argon). The lines are made as the different gases emit light of certain wavelengths. See image 9.

Additional activity to show sodium emission line:
A candle will give a continuous spectrum. Throw a little salt in the candle and a yellow line will flare up. The sodium in the salt emits light of this yellow wavelength when it is excited (by the heat of the candle). As the sodium atoms lose energy again they emit it as light of this particular wavelength.

Viewing the sun's spectrum:
Take the students outside to view the sun's spectrum with their spectroscope. DO NOT allow students to look directly at the sun. Ideally they point at light clouds in the other direction from the sun, or the blue sky.
They will see that the sun's light makes a continuous spectrum, so emits all wavelengths of light.
If they are lucky they will see Fraunhofer lines - dark lines crossing the spectrum that are the result of gases in the sun (and also the earth's atmosphere) absorbing certain frequencies of light. Try links for images of Fraunhofer lines in sun's spectrum: https://media1.britannica.com/eb-media/02/96902-004-856CCB82.jpg or http://jazzistentialism.com/blog/wp-content/uploads/2014/05/fraunhoferl… Scientists look at the position of these dark lines to deduce what molecules our sun is made of. Ask students where they see the lines and tell them what molecules in the sun's atmosphere they are detecting.

Extension with Fraunhofer lines for older students:
The position of the dark lines tell astronomers what other stars are made of and what type of star they are looking at: http://www.cnyo.org/wp-content/uploads/2014/02/2014feb26_WhiteDwarf.jpg
The lines also tell them how fast and in what direction the stars are moving, by how red-shifted the lines are. Red-shift image try http://en.wikipedia.org/wiki/Doppler_effect#mediaviewer/File:Redshift.s…. See Doppler effect activity to model how red-shift works using sound.