Hiatus Again

Hello girls!  Unfortunately, it's finals time again, and FSG has to go on a break while I work on school.  It's a busy time, and FSG will be taking a rest for two weeks.  Remember, the better you do in school, the more choices you have of what you want to do next--so even though I'd rather be having fun, there's a time for play and a time for work, and now is the time for work.  Check out the archives for projects you never got to, make some experiments of your own, or just try something different, like arts and crafts, for a little while.  Science will return!

Mini Monday: Blind Spot

Hello girls!

 This is Megan again, and I’m going to be doing another guest Mini Monday! We’ve all seen some pretty spiffy stuff in our lives, from a gorgeous sunset to the way water looks when the sun reflects off of it. Thanks to our eyes, our brains get to experience some pretty cool stuff. But we’ve also probably had our eyes “play tricks” on us- sometimes the information the eyes give to the brain is a little misleading. We call these “tricks” optical illusions. Today we’re going to experience an optical illusion using just an index card (or other stiff piece of paper) and a long, straight stick.

First, mark an “x” on the index card (big enough to see!). About two inches to the left of the “x” we’re going to put a dot. Now is where the stick comes in. A ruler stick works great, but if you don’t have one you can get creative (I used a broom). Now hold the card about an arm’s length away from you, facing you so that you can see the dot and the x.  Hold the stick so one end is up against you, resting on your cheek (Be careful! You don’t want to poke yourself in the eye!) and the other end is pointing away from you, out like a telescope. If you are looking down the stick, it should look something like this.

  Holding the card at arms’ length, close your right eye. Using only your left eye, stare at the “x”, but keep track of the dot out of the corner of your eye. Now, keeping your right eye closed and your left eye looking at the x, slowly move the card towards your face. At some point, (for me it was when the card was about 10 inches from my face, it might be different for you), the dot will seem to disappear! (It might take a couple of tries- just make sure you’re looking at the cross directly). What’s going on here?

What is happening here is this: the inside of your eyes are covered with “rods” and “cones”, two different types of “photoreceptors”. These receptors take in the pictures your eye is seeing and send them to the brain through a bunch of cells called the optic nerve. As you can see from this picture here (from thechildrenshospital.org), the optic nerve leaves from the back of your eye.

 At the spot where the optic nerve is, there are no rods and cones, so there is nothing to take in what the eye is seeing so that it can be sent to the brain. This is what we call the blind spot. When the dot seemed to disappear, really the picture of it fell on our blind spots. Normally we don’t notice things missing because we have two eyes so pictures are almost never in the blind spots of both eyes at once. But as we saw today, sometimes the blind spot can make our eyes lie to our brain!

Color Clock Reaction

Bloomin' billowing blue!  That was weird!  I just created my own color clock reaction--a chemical reaction that waits, waits, waits--then bam turns blue just like that!   

To make your own color clock reaction, you'll need:

Four cups

Corn starch or liquid laundry starch (liquid laundry starch is better, but it's hard to find, and corn starch is still good. I used corn starch.)

Vitamin C (You'll find this in a pharmacy like the ones in large grocery stores)

Hydrogen peroxide (pharmacy)

Iodine tincture (pharmacy)

Measuring cups and spoons: ¼ cup, 1 tablespoon, 1 teaspoon, ½ teaspoon

1 baggy

You will definitely need an adult for this one!  For one thing, iodine stains--if an adult was helping, it's not your fault if something gets ruined.  Also, glasses or goggles (ones for snow, water, or construction work just as well as science ones) are a good idea to protect your eyes.

First, zip two tablets of Vitamin C (1000 milligrams) into your baggy and crush them with the back side of a spoon.  Crush them into complete oblivion!  Crush them until the pieces are powder!  Then, mix the powder with ¼ cup hot water in the first cup.  Stir it well, like you wanted to make a whirlpool to suck down Odysseus (Odysseus was a Greek hero who was actually a total jerk, and thought he was more important than the people he was supposed to lead-- his soldiers--and the person he was supposed to love--his wife).  So stir well and suck tiny invisible Odysseus into your whirlpool!  Now take 1 teaspoon of your well-stirred liquid, and put it in a new cup with ¼ cup of hot water and 1 teaspoon of iodine (notice how the iodine changes from brown to clear!).  You can pour the first cup down the sink now—we won’t need it again.

Now, take your third cup and mix ¼ cup of hot water (kind of a theme, isn’t it?), 1 tablespoon of hydrogen peroxide, and ½ teaspoon of either corn starch or liquid laundry starch.

Now for the good part!  Put your last cup on center stage, because the show is about to begin!  If anybody besides you and the adult helping you is around, you should call them over so they get to watch.  Okay, ready?  Pour everything from both cups into your final cup together.  Swirl or wiggle the cup just a little bit to mix it, then sit back and hold your breath!  After a few seconds (maybe even as long as minutes!) it will suddenly bloom into blue!  Isn’t it crazy to watch?

This seems like a really weird thing to happen.  So, what’s going on?

Well, a lot, actually.  Iodine comes in two forms in iodine tincture--it can be I_2, two iodine atoms bonded (stuck) together, and it can be I-, an iodine atom that has an extra electron.  Vitamin C breaks I₂ apart into two I-.  That's why the brown iodine turned clear in the first cup--I₂ is brown, and I- is clear.  Vitamin C turned it all into clear I-.

Hydrogen peroxide, on the other hand, has the opposite reaction: it causes two I- to bond back into an I₂.
Meanwhile, left to their own reaction, I- and I₂ would react and bond into three iodine atoms together, I₃-.  But, the Vitamin C reaction is very fast, so at first there aren't any I₂ around long enough to make I₃-.  Vitamin C turns them into I- before they get a chance to become I₃-!  Once all the Vitamin C is all used up, though, there is still enough hydrogen peroxide to make plenty of I₂, and that makes it possible to make I₃-.  This can get confusing, I know, but we're at the color part.  Vitamin C runs out quite suddenly, and that means I₃- can be made quite suddenly, too.  I₃- and starch (whether it's from laundry or corn) form a complex together which is dark blue.  And that's where the sudden blue bloom comes from! Whew, that was a lot of chemistry in a row.  And the effect is spectacular!

Once you're through with the blue, it's perfectly safe to wash it down the drain.  Wash out anything that touched iodine really, really well--it's poisonous if you eat it!

Mini Monday: Liquid Layers

Hello girls! In February, we used liquids of two different densities to make lava lamps.  Things that are more dense have more mass packed in; things that are less dense have less mass packed into the same space.  If you pour both into the same glass, the less-dense liquid will float on top of the more dense liquid!  That's what we'll do today--except we're going to have six liquids in layers!

You will need:
Maple or corn syrup
Milk
Liquid dish soap
Water
Vegetable oil
Rubbing alcohol
A clear glass

No adult supervision required--but keep this away from anybody that might try to drink it, like little brothers or sisters!

If you like, you can use food coloring on the boring-colored liquids (like milk, water, and rubbing alcohol) to make your glass a rainbow!

Pour each liquid in one at a time, and very slowly.  Pour them in the same order that they're listed above, and keep anything from touching the walls of the glass as your pour.  The exception is rubbing alcohol--since it's last, you can touch the sides of the glass as you pour.  Be extra careful with rubbing alcohol--if it goes through the vegetable oil as you pour, it will mix with the water layer and stay there! (That happened to me).  Which is the densest?  Which is the least dense?  Pour very carefully--and enjoy your colorful layered result, courtesy of density!

Liquid layers after rubbing alcohol mixed with water

Pendulum Wave

Hello girls, and welcome to this Thursday's FSG project!  Today I have a really cool project that I'd never done before!  I tried it and knew I had to show you.

We've done an experiment with a pendulum before--so you might already know that a pendulum is a hanging weight, and it swings back and forth for a long time when it gets a little push.  What you might not realize is that how far the pendulum swings depends on the length of its string.  In today's project, we're going to made a bunch of pendulums and hang them all right next to each other--and each pendulum will have a different string length.  When they all swing together, they make really cool patterns!

You will need:
As many weights as you want (but I'd say have at least 5 or 6 to see the patterns).  I recommend using fishing weights that already have a nice place to tie your string.
Thin fishing line
A long bar to hang the pendulums on--I used one in a playground
A long flat thing, like a plank of wood, binder, or piece of cardboard

No adult supervision required!

Cut a piece of fishing line at a length you like--about 3 feet works well--and loop it over the bar.  Tie the ends onto one of your weights.  Next, cut a new piece of string that is longer than the first one--and measure exactly how much longer.  Each new string will be exactly this much longer than the string before it.  (You don't need a ruler to do this--I picked a piece of bark about 2 inches long, and made each new string as long as the one before it, plus the length of my bark.)  If you have lots of weights, you can make each string only a little bit longer--say, half an inch.  If you only have a few weights, you'll be able to see the cool patterns better if you make them about 2-3 inches longer.

Once you've cut your strings, loop them over the bar and tie the ends to the a weight, just like the first one.  Line the weights up in height order (it doesn't matter if you go longest to shortest or shortest to longest).

They should look something like this diagram when you're done.


Blue string looped around a black bar, and tied to green weights

Now is the best part!  Use your long, flat thing (I used cardboard) to lift all the pendulums, and release them at the same time (there's an example in the video at the top of the page).  Look at the patterns!  What do they remind you of?  I thought mine looked like a glowing silver snake!  The shape of the snake is a famous line in the math world, and you see it everywhere in nature, too--it's called a sinusoid.

Want to see what this looks like when a professional does it?  Here are two mesmerizing examples:

Detective Days Mini Monday: Tips and tricks

Hello girls!  Last Thursday we learned how to lift latent fingerprints to identify who's been where.  That is certainly an important skill for anyone doing detective work to know.  However, there are many small tricks that a detective might need to use.  Today's Mini Monday is a collection of them!

Makeshift magnifying glass:
A magnifying glass is curved: when light hits it, instead of just passing through the glass like a window, the light is refracted, or bent.  The bent light makes the object look bigger to your eye, and that makes it easier to see very small details--details that could be very important.  But you don't need to carry a magnifying glass around with you--or even own one!  The bottoms of many glass cups are also curved.  You know what that means--you have yourself a makeshift magnifying glass!  Peer down into the glass and slide it over things, like a page out of a book, to see if it's magnified (and how much).  Different glasses will magnify things differently--so try them out!

Picking locks:  
Sometimes, detectives need to get inside locked doors--maybe someone behind them needs help, and can't open the door from the inside because they're passed out, or only a baby.  Picking locks like the one on your front door is difficult, and takes serious training--it's not something I know how to do.  But some locks, like those on most bathroom doors, are easy to pick and every girl should know how.  The locks you can pick have small, round holes instead of a place to put a key.  You can pick this lock by sticking something skinny, long and hard straight back into the hole and pushing.  Things that work well are Allen wrenches, bobby pins, or a straightened-out hook of a wire hanger (the last one is my favorite).  It is important to hold the lock-pick perfectly straight as you slide it in; if it doesn't work at first, just pull it out and try again.  I recommend having somebody inside the bathroom when you try this, or locking it while it's open--that way if you have trouble you won't be locked out of the bathroom for hours!  Oh, and be sure to check that nobody's using it first, of course.

How to tell if something has been added to a copied document:
Detectives don't only catch thieves who grab things and run: they also catch thieves who cheat and trick to steal.  One of the ways thieves cheat people is by adding things to contracts after they've been signed, and pretending the extra writing was there all along.  If somebody used computer programs to do this, you'll probably need equally fancy computers programs to catch it.  But one really common way of altering documents can be caught with your own eyes--if you know where to look.  Often, criminals simply write  extra things on their copy of the contract, and then copy it again to make it look like it was always there.  So how do you catch this?  Every time a document is copied by a photocopier, it loses some of its fidelity--that is, it is a little less clear and crisp.  It can get noise, small black and white speckles, on it.  Writing looks more jagged, with tiny little sharp edges, instead of smooth writing like with a pen.  So here's the trick: when a perfidious bad guy has a copy of something, writes on it and copies it again, the first writing has been copied twice and the added writing has only been copied once.  The real writing will be twice as jagged and noisy as the fake writing added later.  So if some writing looks a lot newer and smoother than other writing, your suspicions should be instantly raised.  Try this by writing your own note, copying it (most libraries make copies for only about ten cents), writing something new on the copy, and copying that.  See the difference?  It may be very small, but you can learn how to see it, just like a detective would.

Should you trust an alibi?
If a crime took place and you are interviewing a suspect, chances are they'll have an alibi--something else they say they were doing, or somewhere else they say they were, when the crime happened.  The problem is, people telling the truth and liars all want you to believe their alibi.  So how can your spot a lie?  There are two good ways.  First, their story might have lots of holes in it.  This requires real detective work--check in on every tiny detail, because if they're lying, they might have missed something.  Perhaps the suspect said they went to a diner the day of the crime--but if you go to the diner and check, you might find out there was a kitchen fire during that time, and everybody had to stand in the parking lot for ten minutes while it was put out.  That's something they would know if they'd actually been there!

But there is another way to spot a lie, too.  Really professional criminals won't make many mistakes like that--they are sure to check these things themselves, the same way you would.  They will have absolutely spotless alibis that you can't find even the tiniest thing wrong with--and that's the giveaway.  If they're really innocent, the day of the crime was just a day in their life--and life isn't spotless.  Real people, in real life, do not remember every detail of a random day in their life perfectly.  They do not remember the exact time they did everything, and they do not remember what everybody they met that day was wearing--you get the idea.  If someone remembers everything perfectly and nothing can be questioned, they probably thought it up beforehand.  Don't forget about them and don't let it go.

Now you have a full set of skills to investigate with.  You can find and preserve fingerprints, make a magnifying glass nearly anywhere, pick locks, spot fraud on a contract, and spot fake alibis by clumsy crooks and professionals alike.  Use your new skills well.  Investigate with honor, and never give up.  Even the cleverest, richest, slipperiest malefactor can always be brought to justice, if one dogged detective refuses to give up.