Invisibility has been something that has captured our imagination in books and movies from The Invisible Man (1933) to Harry Potter (2001). And, these characters make invisibility seem so cool.

Well, science fiction has become a science fact. Scientists have made objects invisible in their labs.

In order to understand how to make something invisible, we have to think about light. Light moves in straight lines. When it hits a surface, it bounces off, and heads for our eyes. And, the brain interprets this bounced light as an image.

If we want to make something invisible, we have to bend light around the object so that our eyes and brains cannot see it. Bending light is an optical illusion. Invisibility is an optical illusion too.

What scientists have done is get some magnifying glasses and put then in a row so that they collect light into a small beam and then bend it. When you look through those lenses, you cannot see anything. So far, they have been able to make something the size of a hand invisible.

As you can imagine, soldiers and spies would love to get their hands on this invention. But, artists would too. With an invisibility cloak, they could bend light so that windows are not needed, but light still comes into the room.

All in all, art continues to inspire science with new ideas. And invisibility cloaks change how we see and don’t see the world.


You can try this invisibility cloak for yourself at the link below. Impress your students and friends.

Get your own invisibility cloak today!

Pi (π) is an old number. It is found in the ratio of a circle’s diameter to its circumference. This might not seem like a big deal for our modern sensibilities, but this was important in the construction of arches for buildings and churches. And, let us not forget the wheel.

Circles are everywhere from wheels of a car, to wheels on a bike, to the shape of a pizza. If you don’t think pizza boxes don’t have to consider pi when making them, you are mistaken. The problem of a circle in a square has perplexed many mathematical geniuses over the centuries.

Talking about mathematicians, they have some funny words to describe pi.  Mathematicians would call pi irrational, which means that you can never find a fraction that is equal to pi.  For ancient people, or for anyone without a calculator, this is maddening. It is nice to be able to simplify pi.  But, there isn’t a way to do that.  For centuries, people looked for a fraction for pi and the closest is  22/7, but this doesn’t exactly equal  pi.  The other weird thing about pi is that it is transcendental, which means it will never be the solution to an algebraic expression.

Pi is a number that is everywhere but it just doesn’t fit in our standard way of thinking about numbers.

Another weird thing about pi is that it goes on for infinity, without end. Computer scientists have calculated pi for billions of digits. Like this …3.14159265358979323846264338327950288419716939937 …  And on and on and on.

The last thing about pi is that it is use in statistics without our knowing. Whenever there is a bell curve shape, the mathematical expression for the bell curve, also known as a normal distribution, has pi in it. That means that pi is not only in every circle you see, but in any poll where an average is taken.

Pi is everywhere, which is why we take a day out of the year to celebrate it.

Happy 3.14!


For those serious about pi:

A history of Pi

A pi-shaped pi pan

We tell time by measuring a repeating pattern. The earth spins — causing it to be light and dark, which we translate as a day. Pendulums swing back and forth, which we translate as a second. Scientists would call things-with-repeating-patterns oscillators. However, there is a problem.

Researchers have found that the earth speeds up and slows down in unpredictable ways. So, the earth is not a good way to measure the passing of time. The earth is a bad clock.

This is unfortunate, since we need precise clocks for many of the technologies we use,  like GPS. So we need a better clock–a more precise clock, a clock that is stable for a long time.

To make a better clock, it needs three parts: An oscillator to produce a repeating pattern; a counter to measure how often the pattern occurs. And, a part to make sure that the oscillator is creating this pattern correctly—which is called a discriminator.

Deep in a precise clock, or an atomic clock, is an oscillator. In this case, it is a quartz gem that is vibrating—the quartz acts like a piece of jello that wiggles when hit. And, those wiggles are counted to tell time.

To make sure that the quartz is wiggling correctly, atoms are used to check it. Cesium atoms


Well, inside the atoms are electrons. And, electrons live at different levels from the center. Electrons can move up and down these levels, like a ladder, when they get zapped with energy. However, the electrons can’t keep that energy, so they give back a precise amount of energy when they return to their original level. It ends up that that energy given back has a precise oscillation to it. This is compared to the wiggles made by the quartz to see if the quartz is correct.

Sure, there are lots of steps, but it is worth it, since atoms are very precise. They lose their precision every 1.4 million years.

So it seems that atoms take a licking, and this keeps clocks ticking.