Today if you find you are lost, you can usually just pull out your GPS (Global Positioning System) to find out exactly where you are, and find exactly where you want to go.  Many cars and nearly every cellular phone have GPS units or apps to use for finding your way.  But the GPS system didn’t become fully operational until 1995.  People have needed to find their way for hundreds of years!  What did people do before GPS to find where they were going?

Throughout the years humans have used a number of methods to find their way (that is, to navigate) to their intended destination x.  Hundreds of years ago people would use known landmarks, or the position of the sun, moon, and stars to decipher where they were.  Beginning about the year 1040 AD, the Chinese began using the compass for navigation1.  A compass (in this case, a magnetic compass) is simply a small magnetized needle or bar which is balanced on a point on which it can easily pivot or spin.  This magnetized needle will pivot on this point such that one end of the needle points toward North.  Generally this end of the needle is painted red, or otherwise indicates to the user which way is North.  Using this simple device, human beings of the ancient world were able to cross oceans and continents, and .find their way home again.

Why does Earth have a magnetic field surrounding it?  Recall that magnetic fields are created by the movement of charged particles (see our most recent blog about magnets and magnetism).  Scientists believe that Earth’s magnetic field is created by the movement of hot liquid and crystallized iron at its core2.  As the Earth revolves on its axis, the molten iron at the core—and thus the electrons in the iron—are also rotating.  These rotating electrons are what create the magnetic field.

TRY MAKING YOUR OWN COMPASS!

Here’s what you’ll need:

1.       A needle or other thin, lightweight piece of steel

2.       A Styrofoam cup

3.       A scissors

4.       A glass pie plate

5.       A strong bar magnet (good ones are available from eBay and Amazon.com, but you can always try your local hardware store)

Here’s what to do:

1.       Fill the pie plate with water from your kitchen sink.  Place the plate on a flat surface.

2.       Carefully cut the bottom off the Styrofoam cup using your scissors.  Be sure not to leave any of the cup edges.

3.        Magnetize your needle:  take the strong bar magnet and rub one end of it along the needle in only one direction at least 20 times.  This will align the atoms in the needle, causing it to become magnetized.  You can check to make sure your needle is magnetized using a few paper clips; if the needle will pick up the paper clips, it’s magnetized!

4.       Carefully place this needle on top of the disc of Styrofoam you cut from the cup earlier.  Float the Styrofoam with the needle in the pie plate of water.  The needle will slowly turn to point North!
What did you observe?  Did your needle point North?  Did it stay this way?  Be sure to write down all your observations!

CHALLENGE YOUR FRIENDS TO A TREASURE HUNT!

Hide a flag in a tree or in some tall grass.  Make up a map to the object telling your friends how many feet or steps North, South, East, or West they should go from where they start.  Then provide them with all the things they need to make their own compass to figure out which way is North!  This works when the area is not very familiar, so going to a State Park or wooded campground would likely be a good location.

References for further reading:

1.            Lowrie, W., Fundamentals of Geophysics. 2nd ed.; Cambridge University Press: Cambridge; New York, 2007.

2.            Brain, Marshall.  "How Compasses Work"  01 April 2000.  HowStuffWorks.com. <http://adventure.howstuffworks.com/outdoor-activities/hiking/compass.htm>  28 May 2014.

Magnets are everywhere.  From the small decorative pictures on your refrigerator to the giant cranes that separate metals in junkyards, magnets are found in many places and come in many shapes and sizes. 

But just how does a magnet stick to your refrigerator door, or to the metal in the junk yard?  What is a magnet, and how does it work?

A magnet is simply anything that produces a magnetic field.  It is this invisible magnetic field which allows the magnet to “stick” to some types of metal, like iron and steel.  We often see the magnetic field of a magnet represented as lines leading from one end of the magnet (the North pole) to the opposite end of the magnet (the South pole). 

While these magnetic field lines are invisible, you can see them by putting small pieces of iron metal  (also called iron shavings or iron filings) on a white sheet of paper, and placing the magnet beneath the paper.  The pieces of iron will align themselves along the magnetic field lines!  If you can find some iron filings (which you may be able to get from a metal working shop), try this with a bar magnet (that is, one that is a straight bar or tube)!

Magnetic fields are created by the movement of electrically charged particles, such as electrons (one of the building blocks of the atom).  This movement of electrons can be a permanent quality that comes from the material the magnet is made from, like a refrigerator magnet.  These are therefore called permanent magnets.  This movement of electricity can also be induced using electricity.  Let’s say you have a piece of wire, and you connect it to a battery.  The battery will produce an electric current in the wire—that is, it will cause electrons to flow through the wire.  The movement of electrons through the wire will create a magnetic field around it.  Because this field has been induced by electricity and will stop once the battery is disconnected, it is called an electromagnet (this type of magnet will not be a magnet once disconnected from the battery). 

Since we know that the flow of electrons through a wire will create a magnetic field, and we know that this magnetic field is what causes some metal objects to stick to a magnet, we should be able to make our own magnet using a battery and wire, as in the previous example. 

TRY THIS!

Here’s what you’ll need:

1.       One 9-volt battery

2.       Three feet of thin copper wire

3.       Electrician’s tape (usually thick, black, stretchy tape)

4.       One three inch steel, galvanized nail (not stainless steel or aluminum)

5.       Several paper clips (metal ones, not plastic ones!)

Here’s what to do:

1.       Wrap the copper wire around the nail as tight as you can, at least 50 times.  Leave at least 4 inches of wire hanging off each end of the nail.

2.       Make a small hook at each end of the wire. 

3.       Use the hook at the head end of the nail to hang the wire onto the positive terminal of the battery.   The end of the wire should touch the inside bottom of the terminal.  Secure the wire firmly in place with electrician’s tape.

4.       Use the hook at the point end of the nail to hang the wire onto the negative terminal of the battery.  The end of the wire should touch the inside bottom of the terminal.  Secure the wire firmly in place with electrician’s tape.

5.       Hold onto the wires, and move your nail close to the paper clips.  The nail should now pick up the clips like a magnet! 

NOTE:   Use caution here, because the battery will get hot!! 

Did your magnet work well?  How many paper clips could you pick up? 

MAKE UP YOUR OWN EXPERIMENT!

Connect more than one battery together, and see how many paperclips you can pick up!  Just connect the head end of the nail to the positive terminal of one battery, and the point end of the nail to the negative terminal of the other battery.  Then cut a small piece of wire to connect the open terminals of the two batteries together.

Try using a 12-volt battery instead.  How many paper clips do you think your nail will be able to pick up?

Try using a longer nail, or a larger piece of steel. 


References for further reading:

1)      Magnet.  Wikipedia.  2014, Apr 26.  Retrieved 5-20-2014.  (http://en.wikipedia.org/wiki/Magnet)

2)      Magnetic Field.  Wikipedia.  2014, May 22.  Retrieved 5-22-2014.  (http://en.wikipedia.org/wiki/Magnetic_field)

3)      How Magnets Work.  HowMagnetsWork.com. Retrieved 5-21-14.  (http://www.howmagnetswork.com/)


Licenses

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Creative Commons Attribution-Share Alike 3.0 Germany license:

http://creativecommons.org/licenses/by-sa/3.0/de/deed.en

If you’ve ever eaten raspberries or apples, or seen white tufts of dandelions on the lawn, you’ve seen seeds.  Both the raspberry and apple have lots of little brown, hard seeds inside.  Those little white tufts that are so fun to blow off the dandelion head are seeds, too. 

Seeds are a very important part of a plant’s life, because producing seeds is one way they reproduce (that is, make more new plants): usually if you put plant seeds into some good soil and water them regularly, another plant like the one the seeds came from will begin to grow.

While nearly all plants can reproduce by producing seeds, many can also reproduce themselves in another way, through vegetative propagation (VEG-eh-tay-tive prop-uh-GAY-shun).  This is when the plant uses a part of its body, like a stem or a root, to produce a whole new plant!  Just think, this would be like a whole new you appearing by growing out of your leg!

There are several different ways a plant might naturally do this:

Runners and Stolons:  Stems that grow along the top of the ground, or just under the soil.  As they grow away from the original plant, a new plant will form at the end of this stem, or from nodes which appear in the middle of the stem. Strawberries and spider plants are both plants which use stolons to reproduce.

Rhizomes:  Root-like stems which grow mostly underground away from the original plant.  New plants form from nodes on this stem as it grows. Ginger is an example of a plant that reproduces using rhizomes.

Tubers:  Fleshy roots or stems which also act as food storage for the plant.   New plants are formed from buds or eyes on the tuber. Potatoes, including sweet potatoes, are a good example of a plant that reproduces using tubers.  Interestingly, potatoes also use stolons, at the ends of which are the new tubers.

Corms: Swollen underground plant stems that also serve as food storage for the plant.  New corms, or cormels, form at the end of short stolons to replace the original corm as its food stores are depleted by the plant.  Gladiolus is an example of a plant that grows from corms.

Bulbs:  Underground vertical shoots with thick leaves that are used as food storage for the plant.  Generally a single plant will grow from a bulb each year, using the food stores during the life of the plant.  As the plant matures, food stores are again built up and stored in the bulb for another plant to grow from it the next year.  Onions are examples of plants that grow from bulbs.

Besides these natural ways the plant might reproduce without seeds, humans can get some plants to reproduce this way by using a few easy techniques:

Cuttings:  A part of the plant cut off the parent plant, and placed in fresh soil, sometimes with extra additives that help promote growth.  Usually the cutting has leaves attached.  New roots and leaves will begin to grow from the cutting, forming a new plant.

Division: A mature plant (usually from a bulb or a rhizome) is divided into multiple parts.  The root and crown (at the base of the plant, but still above ground) are kept intact for each divided part.

Probably the most familiar plant that reproduces vegetatively is the potato—you probably have some in your kitchen right now (or if not, you can find them in any grocery store).  As mentioned above, a potato is a tuber, a fleshy stem that stores food for the plant (and for people when we eat them!), and can also sprout to form a new plant. 

Take a close look at a potato.  You will see small, bud-like indentations all over the outside.  These are called “eyes”, and are the places where new potato plants will sprout.  In fact, if you leave a potato in your cupboard long enough, it will start to sprout without any help!  At this point the potato is not good to eat, but you could plant it in your garden and get new a potato plant!

TRY SPROUTING YOUR OWN POTATO PLANT!

NOTE:  This experiment will take at least a few days, but it gets better if you allow one month!

Here’s what you’ll need:

1.      One fresh potato that has not sprouted yet

2.      One drinking glass or a glass jar wide enough to fit your potato inside

3.      Four toothpicks

4.      Enough water to fill your glass about two-thirds full

5.      A journal to record your observations

Here’s what to do:

1.      Push the four toothpicks into the potato around the middle.  About half of each toothpick should still be sticking out of the potato.

2.      Lower the potato into the drinking glass or jar that is two-thirds full of water.  The tip of the potato should be submerged in the water, and the toothpicks resting on the mouth of the jar.

3.      Place the jar in a sunny spot, like a window sill.

4.      Watch the potato jar closely; add water if it becomes too low for the potato to reach, and dump the water out if it gets cloudy and add fresh water. 

5.      After a few days to a week you will see roots forming in the water!  In your journal, write down how long the roots took to appear, what they look like, and how much they grow each day .  REMEMBER TO CHECK THE WATER EVERY DAY, TOO!

6.      After two or three weeks, shoots and leaves will appear at the top of the potato.  In your journal, write down how long it took to form shoots and then leaves, as well as how much the shoots grow each day.

7.      After one month you can remove your potato from the water and plant it in a pot with soil to let it keep growing!

MAKE UP YOUR OWN EXPERIMENT!

·         Try taking cuttings from another plant, like a potted plant in your house (be sure to ask your parents first!).  Be sure to cut the stem so there are some leaves on the cutting.  Place it in some rich potting soil, and see if it takes root!

·         Try the jar and water experiment with a different tuber or rhizome, such as ginger.

References for further research:

1.      “Vegetative Propagation Techniques”.  Perennial Crop Support Series, Jalalabad, Afghanistan. Roots of Peace International Agriculture Programs.  (http://www.sas.upenn.edu/~dailey/VegetativePropagationTechniques.pdf)

2.      Vegetative Plant Propagation.  Science Learning Hub.  2013, September 24.  Retrieved May 13, 2014.  (http://www.sciencelearn.org.nz/Innovation/Innovation-Stories/Zealong-Tea/Articles/Vegetative-plant-propagation)

Licenses:

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Hello to all!!  Just a reminder that if you or your class need science project or science fair idea, we are always happy to help!  There are lots of great ideas that can be done in a short time.  Here are some examples for you to try:

Math: Exploring Probability

Physics: Levers and Leverage

Psychology: Memory

If you have more questions, or you need a little extra help, just go to the "Ask Dr. E" page!  Fill out the form, and tell us what you need for a project.  Be sure to include a few things:

What sorts of projects did your teacher say he or she would like?

When is the science fair, and when do you need to be done with the project?

What grade are you in?

And please be sure to type your email address very carefully, because we won't be able to write back if it's incorrect!

“I remember it like it was yesterday,” you’ll hear people say.  You probably have your own memories too, like what you ate for breakfast, or what you did on your last birthday.  Our memories are very important; they help us learn at school, recognize our friends and family, and even find our way around.  But just what are memories, and how do we get them?

Memory is one of the things our brains do for us: they take information from all around us and store it so we can retrieve it (get it back) at a later time.  The part of the brain mostly responsible for our memory is called the hippocampus, a seahorse-shaped ridge of tissue buried in the middle-lower part of the brain (it would be near the base of your skull, behind your eyes).  People who have damage in this part of the brain cannot form new memories, so despite its being pretty small, it’s very important!

So how good is your memory?  Well, let’s find out!  Go get a piece of paper, a pencil, and a stopwatch.  Take a look at the objects below for 30 seconds (be sure to use a stopwatch or a clock with a second hand so you only get 30 seconds)!  Try to memorize all the different objects you see here.  When 30 seconds is up, scroll down so you can’t see the pictures anymore, and write down all the items you can remember.   Don't cheat by looking at the pictures!!

Now from the list below circle the two items that were in the picture.

1.      Eggs

2.      Slide

3.      Coat

4.      Hat

5.      Guitar

6.      Shoes

7.      Books

8.      Banana

9.      Bell

10.    Radio

Did you list books as being in the picture?  Take a look at the picture again; books are not one of the objects (the two that were in the picture were the slide and the guitar)! 

How did that happen?  All of the items in the picture are things you see at school, so your memory categorized the picture as being of things you see at school.  So when you saw the word books, your memory decided that is also something you must see at school, and so it must have been among the items in the picture.  This is called a false memory, and it happens when our memories cause us to believe we saw or experienced something that did not really occur.   (Don’t worry, false memories like these are not dangerous, and are not a sign of any problems with your memory!)

TEST YOUR FRIENDS WITH A FEW MEMORY CHALLENGES!

Challenge #1: Memory Test

Here’s what you’ll need:

1.      A lunch tray, or a small table

2.      A towel or a sheet

3.      Paper and pens for all your friends

4.      A stopwatch, timer, or a clock with a second hand

5.      15-20 different items

 


Here’s what to do:

1.      Place all the items you selected on the tray or table, and cover them with the towel.

2.      Invite your friends to stand around the table, and uncover the items.  Allow 30 seconds to look at the objects and try to memorize them.

3.      After 30 seconds, cover the objects again and hand out pens and paper.

4.      Ask everyone to write down the objects they remember.

After everyone has finished, allow your friends to look at the items again. 

Were there any items that all your friends remembered?  Were there any that nobody remembered?  Write down items that were either easy or hard to remember.

Challenge #2: False Memory Test

Here’s what you’ll need:

1.      Pens and paper for all your friends

2.      A timer or stopwatch

3.      The lists of words below*

List 1*: read, pages, letters, school, study, reading, stories, sheets, cover, pen, pencil, magazine, paper, words

List 2*: house, pencil, apple, shoe, book, flag, rock, train, ocean, hill, music, water, glass, school

Here’s what to do:

1.      Read List 1 aloud to your friends.

2.      Wait 5 minutes.  Be sure to set a timer!

3.      Pass out paper and pens.

4.      Ask them to listen to the next list, and write down which words they remember from List 1.

5.      Read List 2 aloud.  Allow everyone to write down the words they believe they heard on List 1.

6.      Read List 1 aloud again. 

How many people thought “book” was on List 1? 

This is a false memory (only “pencil” and “school” were on List 1)!  Be sure to let them know false memories aren’t dangerous!

MAKE UP YOUR OWN MEMORY TESTS!

·         Try having your friends walk around a room for 30 seconds.  Then have them leave the room, and you make some change, like remove something or turn something upside-down.  Let them re-enter the room and see how many people notice the change.

·         Make up your own lists of words like the ones you used for Challenge #2, or groups of pictures like those on pages 2 and 4.  See if you can create a false memory!

REMEMBER:  Always be sure to write down all your observations!

*These lists were created by Eric H. Chudler, PhD.  For more memory tests created by Dr. Chudler, please visit Neuroscience For Kids at https://faculty.washington.edu/chudler/chmemory.html

When someone says, “What are the chances of that happening?” what are they asking?  Usually when you hear this, it means ‘that’ is very unlikely (as in, “What are the chances that Santa will bring me a pony for Christmas?”).  However, this question really has a deeper meaning.  Let’s explore what this question really means by focusing on the key word: chances.

When we talk about chances, we are really talking about something called probability.  Probability is just how likely an event is to occur.  So if something has a high probability, this means it is very likely to happen (as in, what is the probability your mom will make you brush your teeth before bed?).  If something has a low probability, it means it is not very likely to happen (as in, what is the probability your mom will let you eat cupcakes for dinner?).  Although in reality, it is not always so obvious how likely or unlikely an event is to happen!

So how do we decide how likely or unlikely an event is to happen?  More importantly, can we predict how often this event will happen?  As it turns out, we can!  If we know how many different outcomes there are for a certain event, we can figure out just how likely each one really is. 

Here’s an example:  take a normal die (this is the singular of dice...so if you have a pair of dice, just use one for this!).  A normal die has six sides, each with a different number 1 through 6. 

If we roll this die, there are six possible numbers we could get, so there are six possible outcomes, and each one is equally likely to happen; one of these outcomes is rolling a number 3.  To find the probability of rolling a number 3, we first count how many times the number 3 appears on the die—we know the number 3 appears only one time on this die.  Now we count how many possible outcomes there are—we know there are six different possible outcomes, since there are six sides on the die, and each one is equally likely to happen.  To find the probability of rolling the number 3, we take the number of times this outcome appears on the die (it appears one time), and divide this number by the total number of possible outcomes (six).

When we divide 1 by 6, we get 0.167 (rounded to three decimal points).  What does this mean?  Probability may always be expressed as a decimal number between 0 and 1, with 0 meaning the event will never happen, and 1 meaning the event will always happen.  This event is closer to 0 than to 1, meaning it is not very likely, but it is not impossible either.  Probabilities can also be expressed as a percent (%), with 0 being 0%, and 1 being 100% (just multiply the decimal number by 100 to get the percent chance of this event happening).  Rolling a number 3 on our six-sided die therefore has a probability of 16.7% (0.167 X 100 = 16.7%). 

An important thing to note about our die is that each of the numbers has an equal chance of coming up on a roll.  Since each number only appears one time, we know that each of these numbers has an equal probability of coming up.  So the probability of each number is the same as for the number 3, or 16.7%.  If we add up the probability of each of the numbers appearing (that is, 16.7% + 16.7% + 16.7% + 16.7% + 16.7% + 16.7%--we have six numbers, all with the same probability, so we add 16.7% six times), we should get a number that is just about 100%.  16.7% + 16.7% + 16.7% + 16.7% + 16.7% + 16.7% = 100.2%; this extra 0.2% is because we rounded to three decimal places—this number is close enough to 100% that we know we calculated correctly.  When you calculate probabilities, remember:  IF YOU ADD UP THE PROBABILITIES OF ALL THE POSSIBLE EVENTS, THEY SHOULD EQUAL 100%!

TRY THIS!

Here’s what you’ll need:

1.       A small bag of Skittles® candies

2.       A small paper bag

3.       A piece of paper

4.       A pen or pencil

Here’s what to do:

1.      Pour 10 Skittles out of your bag onto the table.  DON’T PICK OUT THE COLORS YOU WANT; JUST MAKE SURE THERE ARE 10 SKITTLES!

2.       Write on your piece of paper the names of the different colors in your sample: Red, Orange, Yellow, Green, and Purple, and divide these with long, vertical lines.  Beside the names of the colors, write down the number of the Skittles of that color you have in your sample.  For example, if you drew 3 red Skittles, write Red 3.

3.       Under the names and numbers for each color, write the number of Skittles of that color, divided by 10 (the total number of Skittles).

4.       Place all 10 Skittles in the paper bag.
5.       Calculate based on these numbers the probability of each color being drawn from the paper bag at random (that is, without looking or actively choosing the color).  For example, for 3 red Skittles, 3/10 should be written, and this works out to 0.3 or 30%.  So we know there is a 30% chance of a red Skittle being chosen at random from this sample.

6.       Add up all the percentages.  They should equal 100%, or very close. 

7.       Reach into the paper bag containing the 10 Skittles, and pull one out.  Look at the color, and make a tick mark under that color on your sheet of paper.  Put the Skittle back into the bag, and shake the bag to mix the Skittles well.

8.       Repeat this process 99 times, for a total of 100 tick marks.  Be sure to put the Skittle back in the bag each time!

9.       Count the number of times each color was randomly selected from the bag.   Calculate the percent of the time this color was randomly selected by dividing this number by 100.  Compare this number to the percentage you calculated earlier. 

What have you found?  How close was the percentage you calculated to the number of times out of 100 that each color was chosen?  If any of the percentages were very different, why might that be?

WHAT ELSE CAN YOU TRY?

·         For this experiment, you pulled a Skittle out of the bag 100 times.  That’s a lot, but the more times you repeat your experiment, the more accurate the number will be.  Try repeating this experiment 1,000 times!  See if the actual numbers get any closer to your predictions!

·         You can also try the same experiment with a new sample of Skittles.  Pick out 20 different Skittles this time and instead of dividing by 10 to get your probability divide by 20!

·         Try this with something different:   Use a different candy, or a deck of cards!


Skittles® are a trademark of the Wm. Wrigley Jr. Company.