Chapter 3

Physics and Astronomy

Physics is everywhere around us. You’ve always had a direct experience of it even if you were not aware of it. You experienced physics every time you sat in a bathtub full of water. You definitely felt it every time you moved a box or heavy object, or when you went bowling with family or friends.

Astronomy is the oldest of the sciences known to us. Celestial objects have always intrigued human beings. Since the dawn of our species’ existence, humans have relied on those heavenly objects to navigate through space and to identify the seasons.

This chapter will help you and your child explore some examples of the physics principles that surround you, many of which show up in your own home. In addition, this chapter introduces some basic concepts in astronomy and highlights some of the careers available to people who study physics or astronomy.

ACTIVITY: Racing Juice Cans

Sir Isaac Newton was an English physicist and mathematician who is considered by many physicists to be the father of classical physics. He was born in England in 1643 and died in 1727. He was once sitting under an apple tree when an apple fell on his head and led him to formulate the universal law of gravitation. According to Newton’s first law, sometimes called the law of inertia, when an object is in motion it wants to stay in that same motion, unless a force acts on it to make it change. This also means that if an object is not moving, it wants to remain still unless a force acts on it. For example, if you place an ice cube on a horizontal surface—perhaps in a baking pan on your kitchen countertop—it will stay put. But if you tilt the pan and let the force of gravity act on the cube, it will most definitely move.

It’s a property of matter to want to keep moving if already in motion, or to remain still if it’s not moving. In other words, when it comes down to motion or stillness, matter always, always, always resists change.

STEM Career Choices

Physicist

Physicists study the science of physics, which attempts to understand the laws that govern nature. Physicists explore all aspects of matter and energy, as well as the interaction between them. Some of the topics studied in physics are space and time, quantum physics, electricity, magnetism, relativity, and thermodynamics.

Physicists specialize in some specific field in physics, such as particle physics, nuclear physics, biological physics, optical physics, condensed-matter physics, and astrophysics. Theoretical physicists, such as Albert Einstein, explore the theory underlying principles in nature. They rely heavily on mathematics to construct models that explain natural phenomena. Experimental physicists, like Marie Curie, work in laboratories conducting experiments in order to observe physical phenomena.

The motion of the ice cube moving across the baking pan is called sliding, or translational, motion. But what if an object rolls instead of slides? Does Newton’s first law still apply? A simple experiment will yield the answer.

Materials Needed:

The question this experiment will investigate is whether matter—in this case, the juice inside the can—resists change in its motion more when it’s in liquid form or when it’s in solid form. The real question is whether it’s easier for the juice to go downhill when it’s sliding inside the can because it’s a liquid, or when it’s rolling with the can because the juice is frozen.

To prepare for the experiment, keep one of the frozen fruit juice concentrate cans in the freezer and allow the other to sit on your countertop for a day so that it completely thaws.

When the cans are ready, prop the wooden board up on one end using a stack of books or magazines. This will create the incline necessary for racing the two cans.

Before proceeding with the experiment, ask your child to make a prediction about the results. Which do you think will reach the bottom of the incline first, the frozen juice or the liquid juice? Remember that the frozen juice will roll down the incline, while the liquid juice will slide inside the can. Talk with your child about how this could impact the movement of the cans.

After you’ve made your prediction, place the two cans side by side at the top of the incline. Use a ruler to line up the two cans so that when you remove the ruler, the cans will begin their downhill descent at the same time.

Ready . . . set . . . let go!

9781507200643 juice1

The result might surprise you both. You might have predicted that the frozen can would reach the bottom first, but it turns out to be the opposite!

Since the liquid juice can reaches the bottom faster, the conclusion can be made that it’s easier for the juice to slide inside the can than it is to roll inside the can. Since it’s easier for the can containing the liquid juice to get to the bottom, the conclusion can also be made that the liquid-juice can resists change in its motion less than the frozen-juice can.

The result of this experiment reveals that it’s easier to slide than to roll, which is something you can definitely feel when a car’s tires lock up and start sliding on an icy road.

Repeat the racing juice cans experiment for a friend or family member. See if your friend or family member can predict which juice will win the race.

ACTIVITY: Exploring Newton’s Third Law

You might have heard the statement “For every action there is an equal and opposite reaction.” This law of force pairs is what we call Newton’s third law. This is because when a first object acts on a second object with a force, the second object automatically does the same back, but in the opposite direction. Specifically, the force from Object 1 cannot show up on its own without the opposite force from Object 2 showing up as well. They are always paired. If you wonder where in your daily life you can observe this principle, here are a few hints: Newton’s third law is what makes a space shuttle fly up and away from the earth, and it’s also what makes you able to stand up from a seated position. How does this principle work?

Materials Needed:

Procedure:

  1. Tell your child to insert the straw about 11⁄2" into the neck of the balloon.
  2. Assist your child in securing the straw at the opening of the balloon, so that the opening is totally taped onto the straw with no gaps.
  3. Have your child blow through the straw to inflate the balloon so that it’s full to the max.
  4. Once the balloon is fully inflated, help your child clip the straw with the clip sealer so that the air is sealed tight inside the balloon.
  5. Ask your child to stand at one end of a long table or wooden floor (a hallway is ideal), and place the balloon so that the straw is lined up parallel to the length of the hall or table.
  6. Now tell your child to block the end of the straw with her finger to prevent the air from escaping, and release the clip sealer. Ready, set . . . let go. What do you observe?

Did the balloon move along the floor like it had a small turbo engine attached to it? Well, in a way it does! But what exactly happened? Here is where Newton’s third law comes to the rescue.

When the air inside the balloon begins to release and move out through the straw, the air is actually being forced out by the balloon’s deflation. In other words, the balloon pushes the air out. This is the action force. The reaction force is the force that the air pushes back on the balloon, so the balloon begins to move. Those two action and reaction forces are what Newton’s third law is all about. Without the reaction force showing up, the balloon would never have moved!

9781507200643 newtons1

This is exactly how the space shuttle is able to move up into the sky. The engine attached to the shuttle pushes the exhaust gases out downwardly (action). In response, the gases push back upwardly on the shuttle and its attached engine (reaction). The action force acts on the gases as they are being expelled downward, and the reaction force acts on the shuttle being propelled upward.

STEM Words to Know

Newton’s cradle

Newton’s cradle is a set of steel balls (often five or seven balls) that are hanging right next to each other at the same height. When you lift an end ball off to the side then release it, it strikes the ball adjacent to it, transferring the action and reaction forces to the ball on the far end. That ball, in turn, moves off to the side.

Here’s another example from your everyday life where you’ll find Newton’s third law at work. Next time you find yourself attempting to stand up from being seated in a chair, become aware of Newton’s third law action and reaction force pairs. As you attempt to stand, you actually push downward on the floor with your feet. This is the action. The reaction is the floor pushing back on your feet, helping you to stand up. Think about this: If your feet were pushing downward on a floor that can’t push back up, like a thick layer of mud, would you be able to stand up? If the floor’s reaction that pushes back on your feet were to vanish, you would be stuck in your chair!

STEM Career Choices

Nuclear Physicist

Nuclear physicists focus their investigations on the nucleus of the atom. They explore the subatomic particles that compose the nucleus as well as the forces that hold the nucleus together.

Nuclear physicists can work in careers involving the harnessing of nuclear energy as a form of alternative energy. Such physicists work in nuclear power plants. Another possible career path includes working in radioactive medicine to explore medical applications of nuclear radiation. Nuclear physicists can also be found working in astronomy as well as in archaeology since both fields use radiocarbon dating.

ACTIVITY: The Velocity of Bowling Balls

Bowling balls are the heaviest balls used in any sport. If you’re a small person, you might wonder why there aren’t small bowling balls to match your tiny physique. But the truth is that you can’t play the game with a small, light ball.

To begin to understand the physics involved in a game of bowling, you must first know something about forces. There are two forces that act on a bowling ball when it’s placed on a level wooden floor (such as a bowling lane). There’s the force of gravity pulling the ball down, but there’s also the force of the floor pushing the ball up to support it.

If the floor weren’t hard—if it were made of Jell-O, say—it wouldn’t be able to push the ball up hard enough. The force of gravity and the force of the wooden floor are equal in strength, but opposite in direction (one is up and the other is down), so they balance each other and the ball just sits there. If the floor were pushing up harder than the force of gravity pulling down, the ball would float up. Or if the force of gravity were stronger than the force of the floor, the ball would sink into the floor.

What forces affect the bowling ball after you throw it down the bowling lane? Believe it or not, they’re exactly the same forces that affect the ball when it’s just sitting on the floor or lane. Once the ball leaves your hand and is rolling down the lane, there’s the force of gravity pulling it down and the force of the floor pushing it up, and they’re exactly equal but opposite in direction. Note that there’s very little friction from the floor because the bowling lane is so smooth. The friction is so small, like a penny to a hundred-dollar bill, that it’s negligible.

You may be thinking that when you roll the bowling ball, your hand gives the ball a force. But there’s no way you can “send” a force with the ball. Once it leaves your hand, you have no power over the ball, and definitely no force on it. When you set the bowling ball into motion, what you give it is velocity.

So what is it about the bowling ball that keeps it moving once it starts rolling? You don’t necessarily have to visit a bowling alley to find out.

Materials Needed:

Note that if you don’t have a bowling ball available, you can try the experiment with a billiard ball.

Procedure:

  1. Have your child place the bowling ball on the flat, smooth wooden surface, and give it a tap to make it start rolling. (If you are using a table, make sure you catch the bowling ball before it falls off the edge of the table.)
  2. Ask her to crumple the newspapers into a big ball the size of the bowling ball. (If you’re using a billiard ball, crumple the newspaper into the size of the billiard ball.)
  3. Place the paper ball on the wooden surface, and give it the same tap as you gave the bowling ball.

Did you observe how the bowling ball wanted to keep rolling beyond the 3-yard length of the wooden surface? Did you notice that the paper ball didn’t, that it stopped shortly after you tapped it? But they are the same in size. Why didn’t they act the same?

Newton’s first law (the law of inertia) states that when an object is in motion it stays in motion when all the forces acting on it are balanced. But why does the object stay in motion? The more “stuff” packed into an object, the more it wants to stay in motion. The “stuff” in any object is called mass. The bowling ball has more “stuff” in it than the paper ball, so the bowling ball has a bigger mass than the paper ball. That’s also why a bowling ball is heavier than the paper ball, because it has more mass in it.

Once an object with a mass is moving, and as long as the forces on it are balanced, it doesn’t want to slow down. It wants to keep moving. That’s simply how mass behaves. This property of mass is known as inertia.

STEM Career Choices

Condensed-Matter Physicist

Condensed-matter physics is a subfield of physics. It studies the physical properties of different condensed phases of matter (such as solids and liquids).

Condensed-matter physicists are researchers. They use physics laws that include quantum mechanics and electromagnetism to better understand properties of the condensed phases of matter. Some of the experiments in condensed-matter physics include examining the behavior of electrons in material. Researchers in some universities are creating exotic electrons that behave in ways that may lead to new semiconducting, superconducting, and quantum material.

ACTIVITY: Static Electricity

You’ve probably reached for a doorknob in the winter after rubbing your feet on carpet, only to get zapped. You may have also been shocked attempting to close your car door after you’ve slipped out of your car seat. You’ve perhaps noticed warning signs at gas stations regarding static electricity. What is this thing called static electricity, and why can it be dangerous enough at gas stations that it demands a warning sign? Static electricity is an accumulation of excess electrical charges on an insulated object. The word static means “stationary” or “not moving.”

In order to understand static electricity, it is helpful to learn about atoms and what they consist of. The classical model of an atom includes two types of particles with electrical charge: protons and electrons. The protons reside in the center of the atom inside the nucleus. Protons have positive electrical charge. The electrons are negatively charged, and move around the nucleus in orbits like the planets move around the sun. Opposite charges attract, so the electrons (–) are attracted to the protons (+), and the atom stays intact. There is one other type of particle inside the nucleus that is electrically neutral. Such neutral particles are called neutrons.

STEM Career Choices

Particle Physicist

Particle physics is also known as high-energy physics. It pertains to the study of elementary particles that lie inside the nucleus of the atom. Examples of such particles are quarks, leptons, muons, bosons, neutrinos, and others. Particle physicists work either in theoretical or experimental research.

Theoretical particle physicists require knowledge in theories such as quantum field theory. One area of research for a particle physicist is finding a unified field theory that can explain all physical phenomena. Experimental particle physicists may work in particle accelerator laboratories such as CERN in Switzerland, which is the largest particle accelerator in the world.

A carbon atom, for example, has 6 positively charged protons (p+) and 6 negatively charged electrons (e–), making it electrically neutral. The carbon atom also has 6 neutrons (n) that do not affect its electrical charge.

9781507200643 static1

A carbon atom

All objects are made of matter, and matter is made of atoms. When there’s an equal number of protons and electrons, there’s no excess electrical charge in the object. However, when the object acquires extra charges for some reason, there’s an imbalance between the positive and negative charges. This imbalance causes the object to be “charged.”

STEM Words to Know

atoms

Atoms are the smallest building block in nature. Everything is made up of atoms. Examples of atoms are helium, calcium, iron, gold, silver, etc. When atoms bond together they form molecules. Examples of molecules are oxygen, hydrogen, carbon dioxide, water, etc.

How can an object become “charged”? Only insulated objects can be charged. For example, plastic, Styrofoam, acrylic, and rubber are all insulated objects that can easily be charged. So if you’re wearing shoes with rubber soles, any extra charge your body acquires will stay on you. One way you can get extra charges on your body in the winter (when the air is so dry) is by rubbing your feet against carpet while wearing rubber-soled shoes.

How about an object made of metal; can it be insulated? A metal can be insulated if it’s not touching the ground or any non-insulated body. If a metal can be insulated, then it can also be charged. An interesting thing about charged metals is that they make the extra charges sit on the most outside surface of themselves, so they can be as far apart as possible from each other. This is because charges of the same kind repel each other. For example, if one stands on the inside of a charged metal cage and touches the inside of the metal, the extra charges on the outside wall will be out of reach. This means the person won’t be zapped when touching the inside wall of an insulated metal cage.

STEM Words to Know

Faraday cage

A Faraday cage is an insulated metal object, like the metal body of a car. At the moment lightning strikes, if a person is only touching the inside of the cage (car), the charges that are discharged by lightning will not transfer to the person and will not cause harm to the person within the cage (car).

Charges that are not paired with opposite ones always strive to find a partner of the opposite kind. When your body has extra electrons in the dry winter from rubbing your feet on the carpet, these electrons need a way to go find other protons to pair with. Since most people don’t walk around totally barefoot in the winter with their skin touching the floor, their bodies are insulated by what they wear on their feet. The only opportunity the extra electrons have to escape being trapped on your body is when you touch a metal doorknob. At that instant, all the excess electrons escape your body in a mass exit, and that’s when you feel “zapped”!

Similarly, your body can also acquire extra electrons in the dry winter when you brush against your car seat as you slide out of your car. When you have excess electrons on your body, you’ll feel the spark the instant you touch the car door. But you can experience static electricity in a manner that’s less shocking.

Materials Needed:

Procedure:

  1. Do this experiment in the dry winter season. Tell your child to rip the sheet of paper into tiny pieces about 1⁄4" in length and width each, making a small pile of them on the table.
  2. Using the comb, ask your child to comb the hair of the designated person who has hair longer than 5".
  3. Now bring the comb close to the paper pieces, hovering over them without touching them with the comb. What do you observe? Does the comb pick up some of the torn pieces of paper?
  4. Have your child try something else. Ask her to open the water faucet just enough to have a slender continuous stream of water.
  5. Tell your child to comb that same hair again, then bring the comb close to the water stream at the top without touching the water. What does she observe? 9781507200643 static2

If your child was amazed by the water stream bending due to the comb’s presence, explain that it’s the effect of the static electricity that causes this trick. The extra electrons that the comb picked up from the hair attracted some of the protons in the water molecules, bending their path.

Static Electricity Cautions

There was obviously no danger in the simple static electricity experiments described here. So why is there a warning against static electricity spark at gas stations?

Your body gets charged with a lot of extra electrons in the dry winter when rubbing your clothes on the car seat while exiting the car. By the time you stand up outside your car, you’re very highly charged. When these charges escape your body at the instant of discharging, they do so very quickly, creating a spark. If there’s flammable material connected in some form to your body, for example via the metal handle of the gas nozzle, it could spell disaster.

Here’s how you can safely handle yourself. Touch your car door every time you exit your car seat before touching anything else at the gas station. This contact with metal should remove any excess electrical charge that has built up on you.

ACTIVITY: Magnetizing (and Demagnetizing) a Sewing Needle

Magnets are found everywhere in daily life. You probably have some of them on your refrigerator door glued to the back of a picture or an advertisement. To magnetize a metal object means to give it a magnetic property, so that it can pick up some metal objects via attraction. If you use tools a lot, you might prefer magnetized screwdrivers that make it easy to hold screws while placing them where you want them.

Perhaps you’ve played with magnets at some point in your life to see what kinds of metal objects a magnet can pick up. But what’s more fun than playing with a magnet is making one. If you think this is a sophisticated task that requires some serious equipment, you might be surprised.

Materials Needed:

Procedure:

  1. If the bar magnet sides are not labeled N (for North) and S (for South), then have your child use the compass needle to identify N and S. Have him bring one side of the bar magnet near the side of the compass needle that’s labeled N (it is usually the side that’s colored in red). If the N side of the compass needle is attracted to the side of the magnet he brought near it, then that side of the magnet is S (South). Tell your child to make a note of which side of the magnet is S.
  2. Ask your child to scatter the straight pins on a table, just a few inches apart so they are not touching.
  3. Tell your child to hold the head of the needle in one hand. 9781507200643 needle1
  4. Now have him hold the bar magnet in the other hand. 9781507200643 needle2
  5. Ask your child to stroke the needle, from head to tip, with one side of the bar magnet (say with the north side). Have him do this repeatedly in the same direction at a steady, medium speed, about 5–10 times.
  6. Now tell your child to touch the tip of the needle in his hand to one of the straight pins on the table. Ask him to lift up his hand holding the needle. Does the needle pick up the pin?
  7. Tell your child to see if his needle can pick up more than one of the pins on the table. Ask him to test whether his needle can pick up all four pins at the same time.

By now your child has figured out that he has just made a tiny magnet out of his needle. How exciting! By stroking a metal object like a needle (which is made of steel) with one side of the bar magnet, a permanent magnet is created out of a sewing needle. However, such a magnet is small and weak, so it can only pick up tiny objects like pins and needles. Maybe it would be better to let the needle just be a needle, rather than a magnet. There is a quick way to demagnetize objects. To demagnetize a metal object means to make it lose its magnetic property.

Materials Needed:

Procedure:

  1. Assist your child in holding the head of the needle with a pair of pliers.
  2. Lighting the wand lighter, hold the hand of your child that is gripping the pliers in your hand, and bring the needle inside the flame. Keeping the needle in the flame will make it glow. Let the needle glow for about 10 seconds, then set it aside on a piece of paper for a few seconds to cool.
  3. Now ask your child to touch the tip of the needle to one of the straight pins on the table. Ask him to lift up his hand holding the needle. Does the needle pick up the pin?

STEM Words to Know

Curie temperature

The Curie temperature, or Curie point, was discovered by a French physicist named Pierre Curie in the late nineteenth century. He worked with his Polish-born wife, Marie Curie, who was also a physicist, working on experiments related to radioactivity. They were both honored for their extraordinary scientific contributions by being awarded the Nobel Prize in Physics in 1903.

If most of the needle glowed hot inside the lighter flame, then the needle would have become demagnetized. This means the needle would no longer pick up the pins. Its magnetic effect was removed by heating it. When the metal of a permanent magnet is heated above what is known as the Curie temperature, the metal loses its magnetization.

ACTIVITY: What Are Magnets Made Of?

Magnets come in different sizes, shapes, and colors. Some are plated with a silver color, some black, and some even gold, among other colors. But what do they all have in common? Are there certain materials magnets must have inside them to become permanent magnets?

As a rule of thumb, if a magnet cannot strongly attract a particular substance to the point where it will stick to the magnet, then it can never be made out of that substance. For example, if a magnet cannot attract plastic, then a magnet cannot be made out of plastic alone. There are magnets coated with plastic, but the plastic has nothing to do with the magnet being a magnet. So what material is needed to make a permanent magnet?

Materials Needed:

Ask your child to make a prediction as to which items may be attracted by the magnet. It’s always fun to compare the results of an experiment to a prior prediction.

Procedure:

  1. Ask your child to use the two sheets of paper to record her results. Tell her to write at the top of one page the word ATTRACTED, and at the top of the other page the words NOT ATTRACTED.
  2. Tell your child to place the objects in the materials list on a table so they are available for her to test them. Ask her to hold the magnet in one hand.
  3. Now touch the magnet to each object, one at a time. Ask your child to write the name of each object that sticks to the magnet on the sheet with the ATTRACTED label. Have her remove that object from the magnet so she can be ready to test the next object. All objects not attracted by the magnet should be listed on the other sheet.
  4. Have your child test the objects that are not attracted by the magnet twice, so that she can be certain they weren’t. If she wants to add other objects to the list, encourage her to do so, and ask her to record them on one of the two data sheets.

Were you surprised by some of the results of this experiment? Did you expect the penny or the copper pipe to stick to the magnet? What about the gold and silver rings and the aluminum pan?

These items just named are metals, and it’s easy to assume that all metals would be attracted to a magnet. The penny is copper-plated, but is really made out of zinc, which is another metal. By now your child has figured out that some metals aren’t attracted to a magnet. Some of the metals she tested that ended up on her NOT ATTRACTED list were zinc, copper, gold, silver, and aluminum. These are metals that cannot alone be made into a permanent magnet.

Now have her examine the ATTRACTED list. She should find there the iron nail, the sewing needle, and the screwdriver. What material do they all have in common? Ask your child what she thinks.

If your child guessed iron, as the “iron nail” suggests, then she guessed right. Iron is ferromagnetic. Ferromagnetic refers to elements that either can become permanently magnetized or are strongly attracted by a permanent magnet. There are three metals that are ferromagnetic: iron, nickel, and cobalt. Other ferromagnetic materials include some rare-earth elements, such as neodymium. The sewing needle and the screwdriver are made of steel, which has iron in it. The sewing needle is also plated with another metal called nickel, which happens to be ferromagnetic as well.

A magnet has a magnetic field. The magnetic field is invisible, but can be felt when bringing the two north sides of two different magnets close to each other. The repulsive effect between the two close north poles that refuse to touch indicates the presence of a magnetic field that is “sensed” by them at a distance.

When a magnet is brought close to an item that contains ferromagnetic material, the ferromagnetic material “senses” the presence of the magnetic field. The ferromagnetic material reacts to the presence of the magnetic field by becoming strongly attracted by it. In other words, once the magnet is at a certain distance from the item, the item starts to move toward the magnet as it is guided by the magnetic field of that magnet.

STEM Words to Know

permanent magnet

A permanent magnet is made out of ferromagnetic material. Once it becomes magnetized, a ferromagnetic material does not lose its magnetic property easily unless heated above a certain high temperature.

Since the items that contained ferromagnetic material were strongly attracted to the magnet, then the material those items are made of can be used to make a permanent magnet. Most magnets nowadays are not made of one element alone. Magnets today are made of an alloy (which is a combination of different elements) that must contain ferromagnetic material.

ACTIVITY: Keeping a Moon-Phase Journal

When the moon is visible at night, it’s the brightest object in the night sky. People in ancient cultures were constantly aware of the cycle of the moon as it changed its phase, and this information was significant to their daily lives. Some calendars today still follow the moon’s cycle, such as the Jewish and Islamic calendars. There are still indigenous peoples around the globe who use the moon as a method to count elapsed time in lunar cycles. The moon’s cycle was important not only for religious purposes, but also for telling time and for navigational purposes.

These days there are so many distractions in everyday life that people rarely look up at the sky, let alone take note of the presence of the moon. It’s very simple to learn to become aware of the moon’s phases, and to learn to tell time, and directions, simply from the moon. It all starts with keeping a moon journal for one full cycle of the moon.

Materials Needed:

Procedure:

  1. Using a search engine on the Internet, find out when the next new moon will be. (A moon cycle is generally considered to begin with the new moon.) Have your child start his observations of the moon on that day.
  2. Help your child create a table with four columns on his paper sheets. Ask him to make 30 rows in the table, one for every day of observation. (He will most likely need to use more than one sheet of paper for the entire table.) The provided table can serve as an example to illustrate what his table would look like. He will need to expand this table into 30 rows to accommodate every day of the lunar cycle.
  3. Tell your child he does not need to stay up late or wake up very early on the days when the moon rises and/or sets at times outside his normal waking hours. Assist him in finding the rising and setting times with an Internet search for those days. He can simply search for “data for moon on” and type the date, including the year as well as the city where you live.
  4. On days or evenings that are clear, walk outside with your child and observe the moon’s shape if it is visible that day or night.
  5. Have your child record the moon’s data for each day in his table. Assist him in making it a daily habit to either step outside to look for the moon or (in case of cloudy days or days when the moon is not visible during his waking hours) find moon information for that day online.

Use this sample table to help your child make an expanded version for all the days in the moon’s cycle. In the column that lists the shape of the moon, have your child draw the shape of the moon for that day.

Sample Moon-Phases Record
Day Number Shape of Moon Moonrise Time Moonset Time

1

   

2

   

3

   

Once an entire lunar cycle is recorded (from one new moon to the next new moon), you can sit down with your child to look at his record and see what he can learn from it.

Ask your child first to examine the Shape of Moon column in his table. What does he notice about the shape of the visible moon day after day? Quiz him on whether he notices more of the moon’s disk becoming illuminated with each subsequent day until the full moon. Prompt him to notice what happens to the moon’s illumination in the second half of the cycle following the full moon phase. Does he observe that the disk of the moon becomes less and less illuminated as the moon goes through the second half of its cycle?

Next, have your child examine the Moonrise Time column. What does he notice about the rising time of the moon day after day? Ask him if he observes that the moon rises later every day. Ask him to calculate the number of minutes the moon rises later every day. Using a separate sheet of paper, tell your child to start at the top of his table, subtract the moonrise time in the first row from that in the second row, and write the difference on a new sheet of paper. Ask him next to subtract the moonrise time in the second row from that in the third row and record it underneath the first difference he calculated. Tell him to do the same calculation for all subsequent numbers in the Moonrise Time column until he reaches the end of the table in his moon phases record. If he took all the numbers he calculated and wrote on the separate sheet of paper, then found their average, he would find that the moon rises (on average) about fifty minutes later every day.

Next, have your child examine the Moonset Time column. What does he notice about the setting time of the moon day after day? Ask him if he observes that the moon sets later every day just like it rose later every day. Ask him to calculate the number of minutes the moon sets later every day, and write down that number on another separate sheet of paper. Tell him to make the same calculation for the entire fourth column in his moon phases record. If he took all those number of minutes and found their average, he would find that the moon sets (on average) about fifty minutes later every day.

The reason the moon rises (and sets) about fifty minutes later every day is due to the moon’s rotation about planet Earth. If the moon didn’t rotate around Earth, then it would always rise and set at a precisely fixed time day after day.

ACTIVITY: Moon Navigation

Before modern times a skilled navigator was a prized person in society. Navigation was accomplished using objects in the sky—the sun, moon, planets, and stars. Notable to those fine navigators were the movements of those objects in the sky. The canopy overhead that we call the sky was like a map that helped people find their orientation in space while also helping them tell time.

How can you use the moon to navigate through space and time? It all boils down to understanding the phases of the moon as the moon moves around Earth.

Everything in the sky rises in the east and sets in the west. That basic reality is a consequence of the earth’s rotation. The moon is the closest celestial object to Earth, and it moves around the earth. It takes the moon about 29–30 days to complete one cycle around the earth. Because of this gradual rotation of the moon around Earth, the moonrise time (and moonset time) occurs later every day for each moon cycle.

New Moon Phase

At the beginning of a moon cycle, the moon is lined up in the same direction as the sun relative to an observer on Earth. In other words, if an observer on Earth faces the direction of the sun, the moon will be in that same direction as well. The moon is said to be in a new moon phase when it’s in the same direction as the sun relative to Earth. In this phase, both the moon and sun rise above the horizon at the same time. They also set below the horizon at the same time. This means that a new moon rises in the east at sunrise, and sets in the west at sunset. Also, because the moon and sun in this phase are in the same direction relative to someone on Earth, the side of the moon that’s lit by the sun is facing away from Earth. This makes the new moon not visible on that day because the side of it that is lit is facing away from Earth.

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First Quarter Phase

At a quarter of the way through the moon’s cycle, the moon is said to be in a first quarter phase. For an observer on Earth, this is when the right half of the moon’s disk appears lit. A first quarter moon rises in the east at noon, and sets in the west at midnight. The first quarter moon is exactly halfway between a new moon and a full moon. Note that its rising time at noon is halfway between sunrise and sunset, and its setting time at midnight is halfway between sunset and sunrise.

STEM Career Choices

Astronomer

Astronomy includes the study of planets, moons, asteroids, comets, stars, galaxies, nebulae, dark matter, and everything pertaining to the universe. Astronomers focus on specific areas of study. Examples include solar astronomy, planetary science, evolution of galaxies, and the origin and evolution of stars.

Theoretical astronomers focus on developing computer models of the phenomena they are studying in order to understand its evolution in time. An example is creating simulation models that allow astronomers to understand the physical processes that underlie a star’s physical appearance. Observational astronomers focus on collecting data by using a telescope—or sometimes a spacecraft—and analyzing their findings to test theories or answer questions. Most astronomers work in research in universities, though others work at aeronautics companies or agencies such as NASA.

Full Moon Phase

Half a moon cycle later, when the moon is on the opposite side of the sun (relative to an observer on Earth), the moon is said to be in a full moon phase. In this phase, when the sun sets the moon rises, and vice versa. This means that a full moon rises in the east at sunset, and sets in the west at sunrise. Because the lit face of the full moon that’s facing the sun is also facing the earth, the entire disk of the moon is fully illuminated on that day.

Third Quarter Phase

At three-quarters of the way through the moon’s cycle, the moon is said to be in a third quarter phase. This is when the left half of the moon’s disk appears lit for an observer on Earth. A third quarter moon rises in the east at midnight, and sets in the west at noon. The third quarter moon is exactly halfway between a full moon and the next new moon. Note that its rising time at midnight is halfway between sunset and sunrise, and its setting time at noon is halfway between sunrise and sunset. Note that reference to rising and setting times at noon and midnight are approximate, not exact. Those times change slightly from season to season. They also move forward by one hour when daylight savings is added.

The previous four phases are the main four phases of the moon on its cycle around Earth. If you place them on the perimeter of a circle, they would be separated from each other by a quarter of the circle’s circumference. But what about the moon’s phases in between these four primary phases? The following two paragraphs introduce the “in-between” phases.

The Waxing Journey

When the moon is in the first week of its cycle, a crescent moon is visible in the sky with its horns facing the left side of an observer. This crescent moon appears thicker night after night, and is known as a waxing crescent moon. In its second week, the moon no longer has a crescent shape; it starts to gradually become more and more rounded on the left side. In this second week of the moon’s cycle (after the first quarter) it is known as a waxing gibbous moon.

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The Waning Journey

Once the moon is past its full moon phase, it is at the beginning of the third week of its cycle (before the third quarter). The moon is still rounded on both sides, but now the illuminated right side seems to get less and less rounded day after day. This is known as a waning gibbous moon. In the last week of its cycle, the moon’s lit face becomes a crescent shape, but its horns are facing the right side of an observer. This crescent moon appears thinner night after night, and is known as a waning crescent moon.

The moon’s motion in the sky is like a clock that’s always been there. With this knowledge of the phases of the moon, and their rising and setting times, you and your child can now learn how to navigate using it. Make sure to study the phases of the moon with your child before you start using the moon to navigate.

Materials Needed:

Procedure:

  1. On a full moon night, step outside with your child right after sunset and look at the moon. Ask your child the following question: If the full moon rises at sunset, which direction are you looking at? Ask her if the full moon will be visible all night (since it just rose).
  2. On the day of a third quarter moon, when the moon’s disk is half-illuminated on the left, step outside with your child an hour before noon and look at the moon. Which direction are you both looking at when you see it? Remind your child that a third quarter moon sets around noon. Ask your child if this third quarter moon will be visible for the rest of the day into the evening.
  3. A day after a new moon, when there is a thin crescent moon in the sky, step outside with your child right after sunset and look at the moon. Which direction do you both have to look at in order to see the crescent moon? Is it in the direction the sun is setting? Ask your child if this crescent moon will be visible all night.
  4. On the day of a first quarter moon, when the moon’s disk is half-illuminated on the right, step outside with your child an hour after noon and look at the first quarter moon. In which direction are you both looking when you see it? Remind your child that a first quarter moon rises around noon. Ask your child if this first quarter moon will be visible for the rest of the day into the evening.

STEM Q&A

Why does the full moon appear bigger near the horizon?

This phenomenon is called the Moon Illusion. It’s been known since ancient times, but has no real answer. In the early eleventh century, Ibn al-Haytham provided an explanation for the Moon Illusion. The apparent change in the moon is a psychological illusion because the mind perceives the moon as a closer object when it is near the horizon and “interprets” the moon as seemingly bigger. When the moon is higher in the sky, there are no objects around it (like trees) to compare it to, and so it feels more distant and seems smaller.

If your child’s answer pertaining to the first question about the full moon was that she would look east because the full moon rises in the east (as everything else does), then she’s correct. And if she said the full moon will be visible all night because it just rose at sunset, then she nailed it.

Examine your answers to the questions related to observing the third quarter moon. If you said you found the third quarter moon in the west because it was about to set at noon, then you’re correct. And if your child figured out that this moon will not be visible for the rest of the day and into the evening because once it sets it disappears from the sky, then she’s really beginning to tune into the moon phases.

You guessed right if you said you’re looking west when observing a thin crescent moon, right after sunset, the day after a new moon. And yes, that moon was found in the same direction in which the sun was setting. And if your child said that the crescent moon will not be visible all night because it would shortly set in the west, then she’s got it.

Finally, examine your answers to the questions related to observing the first quarter moon. If you said you found the first quarter moon in the east because it just rose at noon, then you’re on target. Your child has most likely figured out by now that this moon will be visible for the rest of the day and into the evening, because it has just risen and will be visible for the next twelve hours.

STEM Career Choices

Astrophysicist

While astronomers are concerned with measuring the positions and properties of celestial objects, astrophysicists focus on applying physics to astronomy in order to understand these objects.

Astrophysicists are also found doing research in universities as well as at places like NASA. However, an astrophysicist is mostly interested in the physics of celestial phenomena. For example, an astronomer may be interested in observing a black hole in some region in space and documenting its location in space. An astrophysicist would be involved in mathematically calculating how massive a star must be in order for it to become a black hole. Astrophysicists heavily use physics laws, including those in relativity, nuclear and particle physics, thermodynamics, and electromagnetism.

ACTIVITY: The Easiest Constellations to Recognize

It’s fun to look up at the sky and take notice of stars and the patterns they make. It’s something that people have done throughout the world and throughout time.

Observed star patterns haven’t changed their shape throughout millennia. When the ancient Greeks looked up at the sky, they perceived the patterns, as did the Babylonians and the Egyptians before them. The ancient Greeks gave a few names, based on their mythological figures, to the star patterns that were visible in the Northern Hemisphere. These star patterns, also known as constellations, still hold the names of many of the ancient Greek mythological figures today.

There are 88 known constellations throughout the Northern and Southern Hemispheres. This lesson will focus on four well-known and easily recognizable constellations in the Northern Hemisphere. You can observe some of these constellations throughout the year, but others only during certain seasons.

Materials Needed:

Procedure:

  1. On your sky chart, identify with your child the shape of the star pattern known as the Big Dipper (which is part of the constellation Ursa Major). The Big Dipper has the shape of a ladle that’s easy to spot. Also, its stars are bright enough to see even with a little bit of light pollution.
  2. Step outside in early August, around 9–10 P.M. Help your child find the direction north, using the compass. Looking over the northwestern horizon, gaze up gradually until you both find the Big Dipper.
  3. The next constellation to help your child locate on the sky chart is Orion. Orion is easy to identify, starting with the three stars that are lined up diagonally close together. These three stars make up what is known as the belt of Orion (a legendary hunter from Greek mythology). The best time to observe Orion is in the winter. In fact, Orion is visible all winter long. To easily find Orion, have your child look for it above the east-southeast horizon around 9 P.M. sometime in early December.
  4. The next constellation to help your child locate on the sky chart is Cygnus. Cygnus is easy to identify because its stars make the shape of a cross. In fact, Cygnus is known as the Northern Cross. The best time to observe Cygnus is in late summer, in late August or early September. Have your child look high in the sky, almost overhead, around 9–10 P.M. in late summer, and try to identify the stars that make a cross pattern.
  5. The last constellation to help your child locate on the sky map is Cassiopeia. Cassiopeia is easy to identify because it looks like a W or M. Cassiopeia never sets; the constellation is always above the horizon all year round. Such a constellation is called a circumpolar constellation. Pick a time to observe Cassiopeia, say in late October. Have your child look above the northeastern horizon at around 8–9 P.M. in late October, until he identifies the stars that make a W pattern.

STEM Q&A

Q: What’s the meaning of these constellations’ names?

A: Some of the constellations were named after characters in ancient Greek mythological stories. For example, Ursa Major was the big bear, Orion was a giant hunter, Cygnus meant “swan,” and Cassiopeia referred to a queen, the wife of king Cepheus. Each one of these names was part of an elaborate mythological story that left its imprint on the night sky.

Once your child learns to identify these constellations, have him trace how they change their position in the sky night after night. For example, by late April, Orion would have drifted westward far enough that it would have gone out of view below the horizon. Most of the Big Dipper is visible year round, and so is Cassiopeia. However, Cygnus would be totally out of view by winter, as it also would have drifted westward and disappeared below the horizon.

Identifying constellations is always a fun activity, especially when taking a walk or traveling by car at night. The next time you’re on a night trip in the car, you can help pass the time by asking your child which constellations he can identify.

STEM Career Choices

Biophysicist

Biophysics bridges the field of biology, which studies life, with physics. A biophysicist is concerned with the study of life on every level, from the smallest level of atoms and molecules to cells and organisms to the environment surrounding them.

Research in biophysics helped reveal the double helix structure of DNA. Biophysicists identified the locations and functions of all the genes in human beings, and some of the genes in more than 100,000 species.

Biophysicists’ research extends into the development of new drugs as they discover how proteins work. This is significant since protein molecules are involved in every chemical reaction in the body. Biophysicists explore using microorganisms to generate biofuel, to clean water, and to create new drugs.