Viruses are very tiny and they are right on the edge of being defined as alive, but they have an enormous impact on humans. Refer to this Scale of the Universe to see the size of viruses relative to other things. (Hint: drag the scroll bar to the left, viruses are after cells and bacteria.) Visit How Stuff Works for an overview of how viruses work. Or, watch this great NPR video about how the flu virus works.
Historically, viruses have been very deadly, but humans have learned how to fight back and win. Smallpox has killed hundreds of millions of people over thousands of years. Edward Jenner created the first smallpox vaccine in 1798 and the World Health Organization declared that virus eradicated in 1977! Explore the links, below, to learn about viruses and how to prevent and fight them:
American Museum of Natural History: Infection Detection Protection This site has several interactive activities about microbes that are for elementary children or for parents and children together.
KidsHealth Flu Basics This site has information about the flu for elementary children.
PBS: Making Vaccines This flash player-based activity allows you go through the process of designing a vaccine.
World of Viruses This site has a lot of resources, activities, and even comics that explain viruses.
MedMyst In this game, you investigate outbreaks of disease around the world.
PBS: American Experiences: Spanish Influenza 1918 Adults might be interested in the online articles, interviews, timelines, and more about this deadly outbreak. The flu killed more Americans than WWI.
The Big Picture Book of Viruses This online collection has information and images for thousands of viruses.
So, remember to cover your cough (with your elbow), wash your hands, and get vaccinated!
Our bodies have many senses. These include sight, hearing, touch, taste, and smell. They also include senses for motion, balance, pain, pressure, and more. One of these senses is for heat. It is called thermoception.
Thermoception does not exactly measure the temperature of something (how much heat energy it has), but how well the heat energy moves to (or away from) your skin where your nerve endings are. This is why a tile floor and carpeted floor of the same temperature feel different temperatures to your skin. The carpet is an insulator and will not allow the heat energy to move very quickly. The tile floor, on the other hand, allows the heat energy to move more quickly. Follow this link to boingboing for a video about this.
Another factor in heat loss is convection. For example, if the air temperature is lower than your body temperature your body is constantly warming the air around it. If the air is not moving, that warm air will tend to stay close to you longer. If the air is moving, your body will constantly have cooler air arriving that will absorb heat energy from you more quickly. Moving air also speeds evaporation from your skin, which cools you faster. Wind chill numbers are a way that weather reporters have of describing how much more quickly you lose heat due to moving air. Learn more about wind chill at howstuffworks. And, follow this link to learn about how it affects your car.
You can also try these experiments (or just read them to learn more):
So, remember to insulate yourself and cover your skin with a barrier that keeps the wind away from your skin when it is cold outside. Stay safe in extreme temperatures!
The existence of what we call black holes was predicted by John Michell using Newton’s laws in 1790s and by Einstein’s theory of relativity in 1915. Most of the detected black holes used to be stars. To form a black hole, a star would need to be at least 1 1/2 times larger than our sun. As stars burn, the explosion of the nuclear fusion pushes out to counteract the pull of gravity. As the fuel is consumed and the nuclear reaction slows and weakens, the force of gravity pulls the mass toward the center of the star eventually collapsing to a singularity. The singularity has no dimension (length, width, height) and is infinitely dense and can generate infinite gravity (but the actual amount of gravity is determined by the amount of mass pulled to the singularity).
The thing that makes a black hole so remarkable is that light cannot escape its gravitational pull. Since light is the fastest thing- nothing else can achieve an escape velocity faster- nothing can escape the pull of the black hole once it has approached within the event horizon. The event horizon for light is called the Schwarzschild radius. However, outside the event horizon the gravity of the black hole functions the same as the gravity of other bodies. Earth would orbit a black hole with the same mass as the Sun just the same as it orbits the sun.
Black holes are fascinating. For more information, please follow the links, below:
For kids: http://www.kidsastronomy.com/black_hole.htm
Also, visit your local library. There are many books about astronomy, but A Brief History of Time by Stephen Hawking is a great place to start. In 1974, Hawking discovered that black holes evaporate over time through a process called Hawking radiation.
Use these resources to find out what would happen if you fell into a black hole, how black holes affect time, and how long it would take for a black hole to evaporate!
Simply cut off the top of a plastic bottle and stretch a balloon across the opening. It works better if you roll up the balloon a bit so that it looks more like a drum than a bag. Load your confetti or other projectile of choice through the bottle opening into the balloon. Pinch the balloon and confetti and stretch the balloon then launch the confetti back through the bottle opening slingshot-style.
Can you think of any games to play with these launchers?
On December 14, China became the third nation to successfully complete a soft landing on the Moon. Please refer to this article at Space.com for an overview. This is the first soft landing on the moon in 37 years! The last to do it was the Soviet Union in 1976. Here is a link to a list of all moon missions. Note the success/fail rate and nationality. And, here is a link to NASA’s Apollo Missions. Back in the day, the U.S. successfully completed the most manned missions to the moon.
You know what the Moon looks like from Earth and you’ve seen pictures of Earth from the Moon. This short clip, explained by the Bad Astronomer, shows a view of Earth and the Moon from a different perspective. Even though the Moon is our closest neighbor, it is still pretty far and moving fast. Successfully completing a mission to the Moon is an amazing feat.
The legendary narration excerpt from the series Cosmos, The Pale Blue Dot by Carl Sagan was inspired by the image of Earth from the perspective of Saturn. While reaching the Moon is an astonishing accomplishment. It is merely stepping out the front door- there is a lot more to explore and learn! And, while astronomers are concerned with what is “out there,” astronomy gives us some interesting insight into what is “right here,” too.
Back in 1885, Wilson “Snowflake” Bentley was the first person to photograph an individual snow crystal. He went on to photograph 5000 of them. None of the snowflakes he photographed were the same, but they were almost all incredibly detailed hexagonal structures that were formed due to the molecular structure of water (H2O) crystalizing under certain temperature and humidity conditions.
Others have continued the study of snow crystals. Some look for the most perfect, symmetrical specimens to photograph. Others study the physics of snowflake formation. Snowcrystals.com is a comprehensive, fascinating site about snowflake formation, myths, classification, and structure. This site also has good information if all you want to do is better understand the tiny crystals on your sleeve.
Of course, in southern Kentucky a beautiful blanket of snow doesn’t happen too often. Luckily, you can make your own snow!
-Snowcrystals.com has directions for making actual ice crystals using an empty plastic bottle, dry ice, and other things. This is suitable for big kids.
-Paper snowflakes are easy, fun, and beautiful. Here is how Vi Hart does it.
-Sodium polyacrylate, a polymer, is sold in kits (and is also found inside diapers) for making snow- just add water! (I found some sodium polyacrylate in Make Your Own Snow kits for a dollar at the local “everything is a dollar” store.)
Let it snow!
‘Tis the season for holiday specials! Whether you like Charlie Brown, cute animals, or wacky elves, there is a Christmas show for you. Modern television and movies are a relatively recent innovation, but the process of producing a more and more realistic moving image has been underway for much longer. The thaumatrope, zoetrope, praxinoscope, phenakistoscope, and flip books are examples of the evolving technology for producing moving images. To see examples of these in action, visit one of the links below:
It is easy to build your own version of a thaumatrope, zoetrope, or flip book. Simply use your favorite search engine and select the set of directions that you like the best. Here are a few things I learned while building my own zoetrope:
- You should have at least 12, but ideally 24, equally spaced vertical slits around the circumference of your zoetrope.
- The slits should be about 1/8th inch wide, but no wider.
- The number of slits and number of images in your animation should be equal.
- Bold, high contrast images work best. A bold, dark line separating the images may also help.
- A faster rate of spin provides a smoother animation. One rotation per second is a good goal.
In the past, it was believed that we perceive moving images because of “persistence of vision.” This is the same reason you see an afterimage if you look at a bright light or stare at something. However, science now attributes our ability to see moving images to something called the beta effect. Visit The Brain from Top to Bottom to find out more about our perception of moving images and other interesting information about our sense of vision.
Happy Thanksgiving! The foods on your plate can be used to illustrate some very interesting math concepts. Enjoy!
In the following set of short, lighthearted YouTube videos, Vi Hart shows you geometry with potatoes, vectors with green beans, binary trees with turducken, and Borromean rings with onions!
The kernels of corn on the cob are generally irregular hexagons. Hexagons maximize the area to the perimeter and they are also really great at tessellation. Examples of hexagons around you are: honeycombs, wasp nests, snowflakes, Allen wrenches, pencils, some animal scales, and some carbon molecules. The tendency toward hexagons for certain circumstances is one of many instances of mathematical patterns in nature.
Please refer to the previous post to find out more about leavening, because Thanksgiving is better with fluffy rolls!
When baking soda, or baking powder that contains baking soda, is added to the recipe there is an immediate chemical reaction. The baking soda is a base, and when it is mixed with an acid, carbon dioxide is released. Recipes that use baking soda as a leavener will direct you to mix the dry and wet ingredients separately then combine them at the end. Also, these recipes will direct you not to over mix. Both of these directions are intended to capture as much of the carbon dioxide from the chemical reaction as possible and not release it before the bread is cooked. To watch this process in action, stir some baking powder into warm water. Also, cook some of your favorite pancakes, biscuits, or banana bread!
Yeast, on the other hand, is a living organism. It is a single-celled fungi that eats sugars and starches and produces carbon dioxide as a by-product. This process is much slower than the reaction of baking soda. It can take two to three hours for yeast bread to be ready to bake. The yeast continues to produce carbon dioxide until the baking process becomes hot enough to kill it. To try it, you can mix one tablespoon baker’s yeast with two tablespoons warm water, allow to stand for five minutes, then add two tablespoons sugar. Set this mixture aside and watch it for two to three hours. Doughnuts, rolls, and sandwich bread are all examples of breads that use yeast for leavening.
As a bonus, in the Elephant Toothpaste experiment, yeast acts as a catalyst to release oxygen from hydrogen peroxide. Mix one table spoon baker’s yeast with two tablespoons warm water, let stand, then add a half cup of hydrogen peroxide. Some dish soap and food coloring is optional. This reaction will last about 20 minutes.
The last post was about polymers, sometimes called slime. Corn starch was one example. When mixed with water, corn starch forms an interesting, slimy substance that has non-Newtonian properties. It is often called oobleck.
The molecules in a Newtonian fluid flow past each other easily, but they maintain the same density and viscosity (flow rate) regardless of stress as long as the temperature is constant. On the other hand, a non-Newtonian fluid reacts quite differently to stress. For some non-Newtonian fluids, the viscosity goes up under stress. These are called shear thickening. For others, the viscosity goes down under stress. These are called shear thinning.
Oobleck is an example of a shear thickening non-Newtonian fluid. Press it or hit it, and it acts like a solid. It may even form cracks. Handle it gently and it flows like thin pancake batter.
DO try this at home! Rheology is the study of the flow of matter, particularly liquids, and oobleck is a great place to start:
Oobleck with kids, what to do and not to do: http://www.learnwithplayathome.com/2013/08/cornflour-slime-how-to-make-and-what.html
How to make oobleck dance:
(I didn’t have a suitable speaker and was able to use my rotary sander under the metal pan.)
Walking on oobleck:
For an overview of non-Newtonian fluids with references to sci-fi:
Here is some information about some possible future uses of rheology:
Use your favorite search engine to find other examples of non-Newtonian fluids. What other ways could they be used?