Ask the Scientist! Archives

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Questions and Answers by Date

  August 2012 July 2012 June 2012 May 2012
  April 2012 March 2012 February 2012 January 2012
  December 2011 November 2011 October 2011 September 2011
  August 2011 July 2011 June 2011 May 2011
  April 2011 March 2011 February 2011 January 2011


August 2012

Q:  What are the strange, charm, top, and bottom quarks for? --Graham, Grade 4, Concord, MA

A:  Everything from people to air to paperclips is matter (material or stuff) and is made of tiny pieces called atoms. Oxygen atoms are what we need to breathe to live, iron atoms are what make up magnets, water is composed of oxygen and hydrogen atoms stuck to each other, and so on.

All atoms are made of three types of even smaller particles mixed together: electrons (which have a negative electrical charge), protons (which have a positive electrical charge), and neutrons (which are neutral and have no electrical charge). Different types of atoms contain different numbers of electrons, protons, and neutrons. As far as we currently know, electrons are not composed of any smaller particles—you cannot whack an electron in two. However, both protons and neutrons are made of smaller particles called quarks.

To the best of our current knowledge, there are six types of quarks, which scientists have given the funny names of up, down, strange, charm, top, and bottom. (Actually there are also antimatter versions of each quark, but we won’t get into that here, since our particle physics bestiary already sounds sufficiently complicated.) A proton is two up quarks and one down quark all glued together. A neutron is two down quarks and one up quark all glued together.

All the atoms in and around us contain protons and neutrons, so there are zillions of up and down quarks around. Strange, charm, top, and bottom quarks are basically overweight versions of up and down quarks. Since they are overweight, they want to go on a diet, shed their extra weight in a quick burst of radioactive decay, and become nice slim up or down quarks. Within less than a billionth of a second, any particle that contains these overweight quarks goes kablooey, leaving behind only ordinary up and down quarks arranged into ordinary protons and neutrons. By bashing ordinary particles together at extremely high energies in particle accelerators, physicists can temporarily create strange/charm/top/bottom quarks, which are generally grouped together in various ways to form conglomerate particles with fancy names like sigma, delta, and lambda. Unfortunately, physicists barely have time to record these new particles before they vanish and turn back into ordinary particles.

To make paper models of atoms and the electrons, protons, and neutrons inside them, see [pp. 9, 18, 31, 32 of Mini Science Kit instructions]. Can you make your own paper models of the two up quarks and one down quark inside each proton, and the two down quarks and one up quark inside each neutron?

See also:

Wikipedia's explanation of Quark

July 2012

Q: How do wingtip devices (winglets) improve the flight performance on an airplane?? --Aaron, Grade 8, (no town given) Georgia

A: Wingtip devices (or winglets) are a great example of a technology that came out of a NASA program in the 1970s and has had a very important and visible effect on airplanes in our everyday lives. To understand how they work, though, let us first get a picture of what is going on around the wing itself during flight. An airplane flies because the wings generate lift, enough lift to get the airplane off the ground and into the sky.  To generate lift, wings are shaped so that air moves at a higher speed over the wing’s top surface than it does over the bottom surface. You can imagine, then, that the shape of the wing must be pretty important and it is (they call it “airfoil design” in aerodynamics). The top surface of the wing with the faster moving air has a lower pressure (you can see this from the “Bernoulli Equation”). That means that the top of the wing experiences a lower pressure than the bottom of the wing, and lift is formed!

Things get more complicated at the end of the wing.  To get the lift that we need, the wing has high pressure on the bottom surface and low pressure on the top surface. As an analogy, think about when you use a straw.  You create low pressure in your mouth while your drink experiences a higher pressure and your drink flows up the straw and into your mouth.  The same thing happens at the wingtips.  Instead of keeping the higher pressure airflow on the bottom of the wing, at the end of the wing some will slip around the wingtip to get to the lower pressure top surface (much like your drink flows up the straw).  This unintended airflow around the wingtip creates a wingtip vortex.  These can have a lot of energy and are part of the reason why air traffic controllers have to wait a certain amount of time before letting the next airplane take off (it can be very dangerous to fly through the last airplane’s vortices!). This energy has to come from somewhere, though, and ultimately it comes from the airplane’s engines which you would rather be using to generate lift than a long, inefficient wingtip vortex.  Aerodynamically, this flow around the wingtip is inefficient because it changes the pressure distribution on the wing and increases the drag.

At NASA in the 1970s, Dr. Richard Whitcomb studied the possible advantages of placing “winglets” at the end of wings.  Simply put, these winglets serve as a barrier to keep the air from sneaking around the end of the wing, reducing the inefficient wingtip vortices. The analysis and testing (in wind tunnels) at NASA showed that by using the winglets you could noticeably increase the aerodynamic efficiency of the wing.  While from a technical perspective that is exciting, what manufacturers and airlines really care about is what that means for fuel economy. Several scientists and engineers (including those at NASA) have shown the fuel efficiency to be increased by 6-7% by using winglets. These are huge numbers for the airlines. Winglets are not cheap (some advanced blended winglets can cost $600,000), but a few percent fuel efficiency increase can also mean hundreds of thousands of dollars in fuel savings every year. This is part of the reason why you see winglets becoming more popular.

For more information and activities, see:

Wikipedia has a good picture illustrating two wing tip vortices

For more information on the history and science of winglets:
- Air Space Smithsonian web article: "How Things Work: Winglets" (pdf)
- Smart Cockpit's web article: "Understanding Winglets Technology" (pdf)
NASA has some excellent material on winglets:
- Fact Sheet on Winglets,
- Ebook: NASA Innovation in Aeronautics (large file)

June 2012

Q: What types of genes are most prevalent in cancerous tissues? On the other hand, what types of genes should be prevalent in normal cell tissues that aren't in cancerous tissues? --Julia, Grade 9, Westford, MA

A: Your body is made of building blocks called cells, which are too small to see without a microscope. Each cell contains genes, pieces of DNA that tell the cell how to operate. As you grow from an embryo to a child to an adult, your cells have to divide and multiply—one cell grows and turns into two cells, which grow and turn into four cells, etc. Even after you are an adult, some of your cells still have to divide, in order to make replacements for worn-out cells, like the layers of your skin that flake off when you get a sunburn.

Unfortunately, sometimes a cell goes haywire and keeps dividing—making lots of copies of itself—even when it is not supposed to. Such a cell is called a cancer cell, and groups of them form tumors. Because cancer cells and tumors grow so fast compared to the rest of a person, they can threaten someone’s life if they are not removed and prevented from growing back.

Two types of mutations, or changes, must occur in the DNA or genes of a cell in order to convert it from a normal cell, which only divides when it is supposed to, to a cancer cell, which keeps dividing all the time. The first change is that genes called proto-oncogenes that tell the cell when to divide get mutated into a permanently “on” state called oncogenes.

As a backup safety system, all of the cells in your body also contain genes called tumor suppressor genes. If the tumor suppressor genes in a cell detect that the proto-oncogenes have become oncogenes and the cell is starting to become a cancer cell, the tumor suppressor genes will make that cell kill itself, ending the threat of cancer. Thus in order to become successful cancer cells, the cells must also have a second type of mutation, which permanently switches off their tumor suppressor genes.

Therefore, cancer cells tend to have proto-oncogenes that have been mutated into oncogenes, and also tumor suppressor genes that have been switched off or deleted entirely. In contrast, healthy cells should have normal proto-oncogenes and fully functional tumor suppressor genes.

Generally mutations in several proto-oncogenes and several tumor suppressor genes are required to produce cancer. Some people are born with one or more mutations, usually inherited from their parents, and thus are a step or two closer to getting cancer than everyone else. However, anyone can develop cancer if they accumulate enough mutations in their genes, so stay away from stuff that mutates DNA, especially sunbathing, tanning beds, tobacco products, radon gas in basements, excessive medical X-rays, human papillomaviruses (HPV), and other known carcinogens.

For more information and activities, see:

Wikipedia article on Oncogene

Wikipedia article on Tumor supressor gene

Best textbook on cancer

Microscope slides of cancer cells and other diseased human cells

Microscope slides of healthy human cells for comparison with diseased cells

Good-quality microscopes (avoid microscopes sold in stores and catalogs—they are nearly useless)

Simple biology experiments - Experiments 13-16

Simple forensics & DNA experiments - Experiments 25-28

May 2012

Q: Can you see yourself in a projected hologram of a mirror?  --Kurtis, Grade 12, Lansing, KS

A: A hologram is a recorded image of an object that appears three-dimensional. Usually holograms are recorded on film, just as cameras can record ordinary two-dimensional photographs on film. (If you haven’t heard of photographic film, ask your parents or another old geezer who remembers Kodak and Polaroid.) When light bounces off a two-dimensional photograph or other flat surface, normally all the light goes the same way, and your eyes can tell that the light came from a flat image. However, when light bounces off a flat piece of film that has a recorded hologram, different portions of the light go in different directions, creating different views in different directions, just as if the light had bounced off a three-dimensional object. Thus your eyes see a floating image of whatever object was recorded on the film.

If you used a camera to record a normal two-dimensional photo of a mirror, in the photo you would see whatever had been reflected in the mirror at the time the photograph was taken—say the photographer and camera. Holograms are the same, just three-dimensional. Therefore a hologram of a mirror would show whatever was reflected in the mirror at the time the hologram was made, probably the proud science nerd who made the hologram, not the person who is currently viewing the finished hologram.

For more information and activities, see:

Wikipedia article on holograms

Mirage Maker—uses mirrors instead of a hologram recorded on film

Hologram-making kits

Holography Handbook: Making Holograms the Easy Way

Holography Projects for the Evil Genius

Shoebox Holography

Simple optics experiments

April 2012

Q: Is it true that vestigial structures were used by our early ancestors and not by us today? --Amore, Grade 9, Cambridge, MA

A: There are many examples of vestigial structures that were used by human ancestors but not by modern humans. The best-known example is the appendix, which is now just a small dead-end street connected to our intestines. Modern plant-eating animals have (and presumably human ancestors had) larger versions of the appendix, which they use to digest leaves. Generally the only modern humans who still eat a lot of leaves are supermodels.

Another example of a vestigial structure in modern humans is the tailbone, a leftover version of the full-fledged tails that many animals have. Every once in a while, a human baby is born with a more extensive tail, a little like Nightcrawler in the X-Men but with fewer “bamfs.”

A third example of a vestigial structure in modern humans is wisdom teeth. Our ancient ancestors had large jaws and lots of teeth for chewing whatever food they could find. Humans have been eating more easily-chewed Happy Meals and "TV dinners" for so long that our jaws have gotten much smaller, but we still have the same number of teeth. As a result, most people do not have enough room for their wisdom teeth, the final set of teeth that appear in the back of the mouth around age 20 or so. Thus, virtually all adults have had their wisdom teeth removed, and virtually all dentists are quite prosperous.

For more information and activities, see:

Wikipedia articles on vestigiality and human vestigiality

Book: Evolution: How We and All Living Things Came to Be

DVD set of Walking with Cavemen/Walking with Prehistoric Beasts/Walking with Dinosaurs/Walking with Monsters

TalkOrigins website on Fossil hominids

Museum-quality fossils: 50 real fossils for $67 (click on Paleo-Sets at upper left)

Simple do-it-yourself paleontology activities

March 2012

Q: What part of the brain makes the electricity to zap the muscle? --Lucas, Grade 2, Framingham, MA

A: When you decide to move a muscle, anything from your eyelids to your toes, that thought comes from the motor cortex in your brain, a small strip that basically extends from your ears on up. The motor cortex on the left side of your brain controls all the muscles on the right side of your body, and the motor cortex on the right side of your brain controls all the muscles on the left side of your body. (If that seems like a stupid design, you can always become a mad scientist and wire up a brain however you want...) The conscious signals to your muscles from your motor cortex are forwarded through other unconscious parts of your brain, including the cerebellum in the lower back of your head, and an area in the lower part of the brain that dies off in people like Michael J. Fox who have Parkinson’s disease, resulting in difficulty controlling their muscles. The signals are transmitted from the brain through nerves, which generally go down through your spinal cord and then branch out to muscles in different parts of the body.

The cells in your brain and spinal cord send a signal from one cell to the next by spitting chemicals called neurotransmitters at each other. (Imagine if people communicated by spitting at each other!) Within a given cell, the signal is transmitted down the length of the cell by pumping electrically charged salt ions (basically table salt) from the inside of the cell to the outside or vice versa, producing a small electrical voltage and current. Eventually the signal gets down to the last nerve cell, which has to talk to muscle cells. The nerve cell spits a neurotransmitter called acetylcholine at the muscle cells. When the muscle cells detect the acetylcholine, they let in salt ions and calcium ions (as in calcium from milk), which produce another electrical voltage and current. The calcium ions make certain proteins inside the muscle contract like rubber bands, and away you go. Since turning on a muscle only makes it contract, muscles in your arms and legs and so forth are generally arranged in pairs—one muscle pulls one way when it is turned on, and the other muscle pulls back the other way when it is turned on. Hey, build your own creature, and you can make it work any way you want!

For more information and activities, see:

Schoolhouse Rock—”Telegraph Line” song on YouTube or at Amazon

Magic School Bus books: "Inside the Human Body" or "Explores the Senses"

Magic School Bus kit

Uncover the Human Body book

Human body model

Explore real muscles, nerves, and organs with a dissection kit

February 2012

Q: What do you think is better—PC or Apple? --Eloi, Grade 5, Candiac, Quebec

A: Our Mad Scientist in Residence finds 21st-century PCs, iMacs, iPads, iPhones, iPods, iClouds, and all other i-Gizmos far too confusing (see note). He feels much more at home with 19th-century electrical devices, especially ones that create giant sparks. If you would like to build anything from simple electric circuits to your own computer at home, here are some good resources:

Snap Circuits
Also available from and other dealers online.

130 in One Electronic Lab
Also available from and other dealers online.

American Science and Surplus electronics kits

Radio Shack Electronic Learning Lab

NOTE: MIT Lincoln Laboratory is not allowed to promote purchasing one brand instead of another, although we can recommend that you approach this question scientifically: gather your own data, ask people what they like about one brand & what they don't like about it, and ask why they chose their preferred brand. Ask people in different careers what kind of computer they use and why. Look online for websites that compare the two. After you gather these facts, you can create your own list of what you see as advantages and disadvantages for each brand, and decide for yourself.

January 2012

Q: Can there be an earthquake large enough to knock us off our rotation/orbit and increase/decrease our calendar year? –Virgil, Grade 11, Casselberry FL

A: The earth moves in two important ways—it rotates or spins on its axis once every 24 hours, giving rise to days and nights depending on who is facing the sun at any given time, and it revolves or orbits around the sun once every year, giving rise to our standard 12-month calendar. In order to really change either of these motions, the earth would have to have something to push against, for example if it collided with another planet. Earthquakes, even the strongest ones you could imagine, are just the earth shaking itself, so they don’t really affect its overall motions. (Spinning ice skaters can change how fast they spin by sticking their arms out or pulling them in to essentially transfer the spin from the mass of their arms to the mass of their bodies. Even strong earthquakes only slightly alter the overall mass distribution of the earth, so they only affect the rotation period by microseconds per day.)

As an analogy, imagine that you are floating in a swimming pool. If you shake yourself around to simulate your own earthquake, you don’t really affect your overall motion in the pool. In order to have a real effect on your motion, you have to push against something else—the water by paddling, or the concrete surrounding the pool, or even another person in the pool. Isaac Newton was the first science nerd to point that out, so the universe passed three laws to that effect in his honor.
 However, the rotation of a planet on its axis can indeed be changed by interactions with other objects. Tidal forces of the moon’s gravity pulling on the earth have gradually slowed the earth’s rotation to its present value, just as friction between a spinning top and a table gradually slows the top. Relative to the other planets in our solar system, Uranus rotates on its side and Venus actually rotates very slowly backwards, so Uranus and Venus must have had some interesting interactions with other objects in the solar system sometime in the past.

Likewise, if planets interact with each other, their orbits around the sun can change. Triton appears to have been a small or dwarf planet orbiting the sun in the outer solar system, but it became trapped by Neptune’s gravity and now is a moon circling Neptune. Pluto and Eris, the largest known dwarf planets in the outer solar system, have strange oval-shaped orbits instead of circular orbits around the sun, presumably also due to interactions with Neptune. Finally, the best current explanation for the earth’s moon is that it was created by a collision between the earth and another planet soon after the solar system formed.

For more information, see:

JPL's website about exploration of the solar system

NASA's website about exploration of the solar system

Home Science Tools' Space and Astronomy page

And just for kicks: "Space: 1999" TV Series from 1975 on YouTube

December 2011

Q: How is radar important in technology? –Zoe, Grade 12, Los Angeles, CA

A: Radar is important because it performs many valuable functions that are difficult to do by other means. Radar is a special application of radio waves, which are very good at detecting objects (airplanes, missiles, satellites, ships) at a distance and determining their location and even tracking their course or trajectory. Radar can generally do this in a wide range of environmental conditions such as day or night, rain, clouds, or fog. Radars can do this detection and tracking at great ranges (thousands of miles). There is no other sensing-at a-distance technique (acoustic, optical) that has all these attributes, and thus, radars find many applications, both civilian and military. Radar works by sending out a pulse of radio energy through an antenna which provides a focused beam. The energy propagates outward and is reflected back to the radar by any object in the beam. The time delay between the transmitted pulse and the received reflected pulse gives an accurate measure of the range to the target, hence the name, RADAR, for Radio Detection and Ranging. Because radio waves generally travel in a straight line, a measure of angle can be achieved with pretty good accuracy, resulting in a three-dimensional positioning of a target. Radar can also directly measure a targets velocity toward the radar by using the so-called Doppler Effect (the classic example of Doppler Effect is the perceived changing pitch of a train whistle as it passes by an observer).

History of Radar: The basic idea of radar dates as far back as 1886 when Heinrich Hertz showed that radio waves will reflect off solid objects. Practical radars were developed at the start of World War II principally for the detection of enemy aircraft and ships. The United States and Britain were the lead in this intense effort, and the US main focus was at the Radiation Laboratory at MIT in Cambridge, Massachusetts. 4000 people in 4 years developed and prototyped about 100 radar systems. This group of dedicated scientists and engineers represented a shining example of the capability of a multi-national, multi-talented team working under extreme pressure on a challenging scientific quest. Within the Radiation Laboratory staff were 11 Nobel-Prize-winners-to-be; so this was an obvious collection of the best and finest scientists the Allies could assemble. Robert Buderi is his book “The Invention that Changed the World” attributes the winning of World War II to the mastery of radar rather than the development of the atomic bomb.

Radar Applications: Two prominent military uses of radar are for detecting and tracking aircraft or missiles that threaten a nation’s military or civilians. Civilians most often encounter radar in the evening television weather forecast, which can show moving clouds of precipitation which have been accurately mapped by "Doppler radar". MIT Lincoln Laboratory pioneered techniques that allow these Doppler radars to not only map clouds but also identify small-scale violent storm cells that could be a hazard to aircraft. As a citizen driving 40 mph in a 30 mph zone you may be introduced to police radar. These small but accurate radars use the Doppler Effect to measure your speed to an accuracy of one percent, so don’t argue with the officer about the accuracy of the radar! Many other radar applications make radar an important technology. One very useful capability is to produce high resolution, optical-quality maps of the ground and structures on the ground from a radar on an airplane or satellite. The high resolution enables one to discern damage to roads, bridges and other structures caused by floods, earthquakes or large fires. Such a mapping radar can fly over a disaster area and produce a ground map through heavy clouds or at night to give officials a broad-area, but high-resolution picture of ground damage. Today, the laser community is building laser radars called LIDAR and these radars can produce extremely high resolution 3D images of targets or the ground and structures on the ground.

For more information, see:

"Radar" on Wikipedia is a very good site. It covers many applications and includes interesting pictures of a wide variety of radars.

"The Invention that changed the World" by Robert Buderi is a good starting point on the development of radar and its impact in wartime.

The world-standard textbook on radar is "Introduction to Radar Systems" by Merrill Skolnik. Merrill put together the material for this book while on the staff of the MIT Lincoln Laboratory in the early 1960s.

November 2011

Q: What's the difference between DNA and RNA? –Peter, Grade 9, Roxbury, MA

A: From our parents, we inherit genes that tell all the cells in our bodies what to do--what color hair to make, how fast to grow, how to be a human instead of a pig, etc. These genes are made of deoxyribonucleic acid, or DNA for short. DNA is basically a very long chemical molecule that is made of much smaller pieces, and those smaller chemical pieces (or bases) are called A, C, G, and T for short. Just as you can string together the 26 letters of the alphabet to spell out words, sentences, and whole books, our DNA has the four chemical "letters" strung together in different sequences to spell out all the instructions for the cells in our bodies. Usually two DNA molecules, or two strands, are wrapped around each other to form a structure that looks like a spiral staircase.

Imagine that you are directing a crew of construction workers to build a house, and you only have one complete set of plans for the house. Instead of passing the one set of plans around to all the construction workers, you would photocopy just the part of the plans that each worker is supposed to build, and give the right photocopy to the right worker.

Our cells do the same thing. Our cells keep their DNA version of the complete instructions safe inside a central compartment, called the nucleus of the cell. Then our cells make copies just of specific genes or parts of the instructions, and send out these partial copies to other parts of the cell that need to use them to make proteins or do other things. Each partial copy is made of ribonucleic acid, or RNA.

RNA is very similar to DNA, but with a few differences. Each time DNA uses a T chemical letter, RNA uses a U chemical letter instead, but the other three letters (A, C, and G) are the same. Also, compared to DNA, RNA has one extra oxygen atom and one extra hydrogen atom attached to each letter; that may not sound like much, but that small difference makes RNA break down more quickly than DNA, sort of like cheap newsprint versus high-quality paper. Finally, RNA is generally found as one strand, not two strands wrapped around each other as in the case of DNA.

For more information, see:

Forensic Science experiments on p. 11 of Mini Science Kit instructions

DNA Science and Technology explanation from National Centre for Biotechnology Education

October 2011

Q: Can you use carbon dioxide to power an engine? Don’t plants use it as a fuel source? –Lauren, Grade 5, [no town given] MA

A: People and animals consume food, and from that food we get both the raw ingredients to build cells in our bodies and also the energy to power our bodies. Plants operate in a very different fashion, since they get their energy by absorbing sunlight. Plants do absorb carbon dioxide (CO2) gas from the air and use that (plus a smidgen of nutrients from the soil) to build new plant cells, but the energy to do all of that comes from the sunlight, not the carbon dioxide.

Written out a bit more formally, our bodies convert sugars or other carbohydrate foods [fuels containing carbon (C), oxygen (O), and hydrogen (H)] into carbon dioxide and water vapor that we breathe out, plus energy that we use:

Food carbohydrates (contain C, O, and H) > carbon dioxide (CO2) + water (H2O) + energy

Car engines and fossil fuel power plants basically do the same thing, but their carbohydrate fuel is oil instead of food:

Oil carbohydrates (contain C, O, and H) > carbon dioxide (CO2) + water (H2O) + energy

Plants do this same reaction backwards:

Carbon dioxide (CO2) + water (H2O) + energy (sunlight) > plant carbohydrates (contain C, O, and H)

Even though carbon dioxide gas doesn’t have chemical energy we can tap into, like any gas it can be kept under pressure, and pressure is a form of stored energy. Since carbon dioxide is in the gas we breathe out, in a sense you can make a carbon-dioxide-powered car by blowing up a balloon, attaching it to a toy car, and letting it go.

For more information, see:

Janice VanCleave, Plants: Mind-Boggling Experiments You Can Turn Into Science Fair Projects

"Plants" section of Home Science Tools website

Balloon-Powered Cosmic Jet Racer Kit

September 2011

Q: How close are we to achieving nuclear fusion in a sustainable environment? --Notter, Grade 9, Cambridge, MA.

A: All material is made of atoms. Each atom has positively charged protons and uncharged neutrons in the center or the nucleus, and negatively charged electrons running in circles around the nucleus. Chemical reactions (everything from making slime to exploding dynamite) involve rearranging the electrons in atoms, but nuclear reactions involve rearranging the protons and neutrons and release about a million times more energy than chemical reactions.

Nuclei really want to be medium-sized, and they are willing to pay you lots of energy to get there.  In nuclear fusion, two small nuclei (such as hydrogen nuclei) join or fuse together to form a larger nucleus (such as a helium nucleus), usually with one proton or neutron left over. A large amount of energy is released as the new nucleus and the leftover proton or neutron fly apart. The positive charges on protons make two nuclei repel (push against) each other. (The electrons are too far away to help.) Nuclei must be given lots of energy—equivalent to a temperature of millions of degrees—to make them bash together hard enough to overcome this repulsion and fuse. Material that hot is called a plasma, a glowing gas in which the electrons have so much energy that they no longer circle the nuclei, but wander freely and conduct electricity. Lower-energy plasmas are found inside fluorescent light tubes and decorative plasma globes (sold by Spencer’s in many malls). Scientists are trying to create fusion reactors that use hot plasma to produce fusion energy. To keep the hot plasma from touching material walls and cooling down or escaping, the plasma is trapped in a magnetic bottle or force field. To demonstrate how magnetic fields can herd charged particles, get your parents’ permission to bring magnets near the screen of an old cathode-ray-tube TV while it is on. (Warning: this may permanently damage the TV picture if you do it too long. You can also use iron filings from to see the effects of magnetic fields.) The TV picture is made by electrons hitting the screen, and magnets bend the paths of the electrons.

Unfortunately, after 60 years of working on the problem, scientists still have not been able to make a magnetic bottle that is good enough for a fusion reactor—the plasma always leaks out too quickly and scientists end up having to put more energy into creating hot plasma than they get out in fusion reactions. If you can figure out how to solve this problem, you could be the next Tony Stark. Of course, the sun is a natural fusion reactor, using its strong gravitational field to confine a hot plasma of hydrogen and slowly fuse that to form helium over the course of its 10-billion-year lifespan. However, we cannot create such strong gravitational fields on earth, and we tend to get impatient for our energy long before 10 billion years have elapsed.

For more information, see:

4 Do-It-Yourself Nuclear Engineering Experiments  When it is completed someday, the International Thermonuclear Experimental Reactor (ITER) will be the biggest and best magnetic bottle for fusion reactions, but it will still be far too expensive to use as a commercial electricity-producing reactor.   An alternate approach uses lasers to create a fusion plasma, but so far it is also much too expensive to use as a commercial electricity-producing reactor.

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August 2011

Q: How is math important in science and technology? -- Angel, Grade 10

A: Math is extremely important for science and technology. If we want to predict how much fuel will be required to send a rocket into orbit, how rising carbon dioxide levels will affect temperatures around the world, how much current will flow through an electric circuit we are designing, or how rapidly a person's body will consume a new medicine, we cannot simply use qualitative terms. ("Probably about that much." "A smidgen more." [Boom!] "Oops, maybe that was too much!") In order to predict such things, we have to use numbers, and we calculate the right numbers by using fundamental scientific laws and equations and then comparing with the results from experiments.

Math is much more than adding, subtracting, multiplying, and dividing. Just as you do word problems in math classes in school, it is important to be able to consider a real situation (say a rocket taking off), figure out which numbers from that real situation are important (for example, the mass of the rocket, the gravitational attraction of the earth, etc.), and then know how to use those numbers to calculate what you really want to know (in this example, how much fuel is required). Once you get past basic arithmetic, you also find that math is divided into different fields, which are useful for solving different types of problems. Algebra is good for figuring out how to write the right equations to calculate what you want to know. Geometry and trigonometry focus on different shapes and angles and such. Calculus and differential equations are especially important when certain factors keep changing, for example for calculating how long it will take a car to get someplace when the speed of the car keeps changing. And when a situation might lead to any of several possible outcomes (such as who will win a race), probability and statistics are useful for predicting the odds of each possible outcome and for analyzing the results afterward.

If you are considering a career in math, science, engineering, medicine, or computers, you should take honors-level algebra, geometry, trigonometry, and if possible calculus in high school. Those high school classes are vital for understanding the more advanced math and science classes that will come next in college.

For elementary and middle school math activities you can do at home, see:
Overholt & Kincheloe, Math Wise! (2nd ed.)
Muschla, Hands-On Math Projects with Real-Life Applications
Brunetto, MathART Projects and Activities
Janice VanCleave, Math for Every Kid
Janice VanCleave, Play and Find Out About Math
Janice VanCleave, Teaching the Fun of Math
Schoolhouse Rock! "Multiplication Rock" on YouTube or DVD

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July 2011

Q: How do nuclear reactors work? -- Charlton, Grade 7, Murfreesboro, TN

A: Large atoms such as uranium or plutonium really want to lose weight, and they do that by fissioning, or splitting, into two medium-sized atoms plus a couple of extra neutrons (one of the components of atoms), all of which fly apart with a lot of energy. If a loose neutron from one uranium fission event hits another uranium, it can make that uranium fission too. If enough uranium atoms are close together, you have a critical mass, such that each loose neutron triggers another fission, and you get a chain reaction.

To make your own chain reaction at home, cut one or two plastic drinking straws into many pieces about 3/4” long, each with flat ends so they will stand up. Put them all close together on a table and put a marble on top of each one. If you roll a marble into this setup, it should knock one or more marbles off their straws, and each of those marbles in turn will knock off one or more marbles. In your experiment, marbles on straws represent uranium nuclei before fission, and rolling marbles represent loose neutrons after fission. If enough uranium atoms (marbles on straws) are close together, you have a critical mass of them; each loose neutron (marble) triggers another fission, and you get a chain reaction—all the marbles fall down. In fission reactors, the trick is to control the chain reaction, so that it neither gets out of hand nor dies out. In power plants, heat from fission reactions boils water to make steam, and the steam blows through turbines and makes them spin. The spinning turbines turn electrical generators to make electricity.

See also:
Hazel Richardson, How to Split the Atom (2001)
Joanna Cole, The Magic School Bus and the Electric Field Trip
Schoolhouse Rock, “Electricity” and “Energy” (on DVD and YouTube)

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June 2011

Q: How do tornadoes form? --Current event topic based on the tornado in Springfield, Massachusetts on June 2, 2011

A: Let's do an experiment to see how tornadoes work. You can make your own tornado with two plastic two-liter soda bottles, duct tape, and a metal washer (1 inch outer diameter, 3/8 inch inner diameter, available from Home Depot, Lowes, or other hardware stores). Peel the labels off the bottles and do this experiment in a large sink or bathtub. Fill one of the bottles about 2/3 full with water. Dry off the top of the bottle and invert the other bottle above it with the washer sandwiched between the mouths of the two bottles to create a small hole between the two bottles. Join the bottles firmly together in this configuration using plenty of duct tape. (It’s okay if it leaks a bit.) Turn the bottles upside down, so that the one with the water is on top, and gently swirl them. The swirling motion should start a tornado in the water that is flowing from the upper bottle to the lower one. Even if you stop moving the bottles, the tornado continues to swirl, since it very efficiently allows the water from the upper bottle to go down (around the edges) and the air from the lower bottle to go up (through the center) without letting them run into each other. To see how inefficient the process can be when the air and water do run into each other, repeat the experiment but without swirling the bottles to form a tornado.

Real tornadoes are similar. If heavier cool air coming from the north flows above lighter warm air coming from the south, the heavier cool air will want to go down, and the lighter warm air will want to go up. They can do that more efficiently if they begin a swirling motion. In most cases, this just leads to thunderstorms with winds blowing in various directions at different locations and altitudes, but occasionally the swirling motion becomes so severe that a tornado forms. The swirling wind in a tornado can blow at 100-200 miles per hour and can do a lot of damage if it reaches all the way to the ground.

For more information on tornadoes and other aspects of weather, and for activities you can do at home, see:

Weather projects kit
Joanna Cole, The Magic School Bus Inside a Hurricane
Schoolhouse Rock, The Weather Show, on YouTube
Schoolhouse Rock, The Weather Show, on
Mary Kay Clarkson, Weather Projects for Young Scientists
Janice VanCleave, Janice VanCleave's Weather: Mind-Boggling Experiments You Can Turn Into Science Fair Projects

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May 2011

Q: What is an ocean current? --Evan, Grade 1, Braintree, MA

A: Ocean currents are when the water moves from one area to another, just as wind is when air in one part of the atmosphere moves to another part. There are two major types of ocean currents:

1. Surface currents are the motions of the upper 1300 feet of water [that's the same as almost 33 buses end to end!] in response to the wind, rotation of the earth, gravity of the moon (tides), and other factors. Generally the surface currents in each ocean basin go in a circle, since the current is deflected when the water bumps into land.

2. Deep ocean currents are the motion of the water from 1300 feet deep to the bottom of the ocean. Water near the equator is heated by the sun, becoming less dense [which means thick, heavy, or filled with something] and rising, and water near the north and south poles is cooled, becoming more dense and sinking deeper. The warmer equatorial water then flows toward the poles, and the colder polar water flows beneath it toward the equator, forming a closed loop known as the ocean conveyor belt. Salt concentration also affects the ocean conveyor belt, since water with more salt is more dense and sinks, and water with less salt is less dense and rises.

For more information and activities you can do at home, see:

Joanna Cole, The Magic School Bus on the Ocean Floor
Experiment with currents due to temperature
Experiment with currents due to salt concentration
Websites on ocean currents for K-12 students:
- Ocean Currents
- Ocean Motion
- How Stuff Works
- The National Oceanic and Atmospheric Administration

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April 2011

Q: How many planets are in the solar system? --Benjamin, Grade 1, Littleton, MA

A: The solar system consists of our sun plus everything that orbits (goes around) it. Things going around the sun include planets like the Earth, moons that orbit some of those planets (just as our moon goes around the Earth), asteroids (giant space rocks), and comets (giant space snowballs). Planets are the largest objects that orbit the sun on their own and are not simply moons of some other object or planet. Currently there are eight officially recognized planets.  In order from the sun, they are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. The first four planets are made  of rock and metal, and the last four are giant balls of gas.

Some objects in the solar system orbit the sun on their own and are smaller than other planets but larger than typical asteroids and comets. Scientists now call these "dwarf planets." Pluto, which spends most of its time further from the sun than Neptune, was listed as the ninth planet in science books for many years. However, because Pluto is only half as wide as Mercury, the next smallest planet (or less than one fifth as wide as Earth), Pluto was recently reclassified as a dwarf planet. Some scientists feel bad for Pluto and think it should still be classified as the ninth planet. If it is, that would make Eris the tenth planet. Eris, another dwarf planet that was not discovered until 2005, is actually a little larger than Pluto and spends most of its time even further from the sun than Pluto.

NASA spacecraft have already studied all eight major planets. New Horizons, a robotic spacecraft that was launched in 2006, will fly by Pluto in July 2015 and send back the first detailed pictures of Pluto. (Think about how old you will be then, and be sure to watch the news at that time!) No spacecraft are currently scheduled to visit Eris.

For more information and activities you can do at home, see:
Schoolhouse Rock! "Interplanet Janet" video (on DVD and YouTube)
Joanna Cole, The Magic School Bus: Lost in the Solar System
Carole Stott et al, Space: From Earth to the Edge of the Universe
NASA solar system webpage
New Horizons mission to Pluto
Astronomy activity kits
Orion telescopes—affordable and good quality

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March 2011

Q: Why does static electricity make my hair stand up? --Emma, Grade 7, Westford, MA

A: All matter (hair, people, books, water, air, leftover fruitcake, etc.) is made of tiny particles with positive or negative electric charges.  As the saying goes, opposites attract, so positive and negative electric charges are attracted to each other, whereas two positive charges repel each other, and two negative charges repel each other. Since positive and negative electric charges attract each other, they usually stay so close to each other that they neutralize each other in most matter, so we don’t even notice them in everyday life.

However, if two different materials are rubbed together and then separated, sometimes more of the negative electric charges stay with one material, leaving an excess of positive electric charges on the other material.  When an object has more of one type of electric charge than the other, this is called static electricity. "Static" means the excess electric charges are just hanging around on the object, as opposed to moving or current electricity, in which electric charges travel through wires in order to go someplace in an electrical circuit.

One good way to create static electricity is to run a comb or brush through your hair. The comb and hair are different materials, and the comb ends up with more negative electric charges, whereas your hair ends up with more positive electric charges. The positive charges in each strand of your hair can see all the positive charges in your other strands of hair, and those positive charges don't like each other—they want to repel or push each other away. Thus the electrically charged hairs on your head stretch out and try to get as far away from each other as possible, leaving you looking like a mad scientist. Eventually other negative charges wander along and neutralize the excess positive charges, and you lose the stylish hairdo. Humidity or water in the air is very good at helping excess electric charges find a new home, and humidity is lowest in the winter, so it is easiest to create static electricity in the winter.

There are many simple and safe experiments you can do with static electricity. Rubbing a comb through your hair is a great way to produce a static charge on the comb, or rubbing an inflated balloon on your hair or clothing is a good way to produce a charge on the balloon. Charge up a comb or balloon, bring it near your hair, and see if your hair moves in response. Cut up paper or thin plastic into very small pieces like confetti, and see if a charged comb or balloon can attract them from a short distance. Charge up a comb or balloon, bring it near a thin stream of water falling from a faucet, and see if the path of the water bends. Charge up a balloon and see if it sticks to a wall. Charge up two balloons and see if they attract or repel each other.

For more information, see:

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February 2011

Q: How does the power company make the power that comes to our house? --Ben, Grade 4, Westford, MA

A: Power is sent to our houses in the form of electricity, or electric charges moving through wires. That electricity can light up light bulbs in your house, or it can pass through an electric motor to make the shaft of the motor spin. Electric motors spin the fan in your air conditioner, the inside of your washing machine, and the disc in your DVD player. Inside each of those motors is an arrangement of wires and magnets, such that forcing electricity through the wires makes the magnets and the shaft of the motor spin.

The power company makes the electricity in the first place by simply using giant electric motors backwards. Instead of putting electricity into a motor and getting spinning motion out of the motor's shaft, the power company forcibly spins the motor's shaft, and that makes the wires and magnets inside the motor generate electricity as the output. When an electric motor is run backwards like this, it is called an electric generator. Some power plants use water flowing through rivers to make paddle wheels spin, and that spins generators to produce electricity. Other power plants use wind blowing through propellers to spin generators and produce electricity.

However, most power plants use some other energy source to heat water until it becomes steam, and then they let the steam blow through propellers or turbines to spin generators and produce electricity. In nuclear power plants, fission reactions in uranium fuel produce the heat to power this process.  In fossil fuel power plants, the necessary heat comes from burning oil, coal, or natural gas.

Solar panels or photovoltaic cells use a completely different approach to produce electricity. They are made out of the same special electrical materials as computer chips, and they absorb energy from sunlight and convert that directly to electricity. There is no heat or spinning involved in solar panels. Unfortunately, solar panels are currently fairly expensive and inefficient (they only convert a small fraction of sunlight to electricity, and lose the rest), so they are not widely used to generate electricity. Hopefully they will be cheaper and more efficient in the future.

If you would like to use an electric motor to generate electricity, you can connect the two wires from a small 1.5-6 volt motor (available from Radio Shack,, Scientificsonline, Hometrainingtools, and other sources) to a voltmeter (available from Radio Shack, Home Depot, Lowes, Walmart, etc.). Spin the shaft of the motor as fast as you can, and see how much electricity you can produce.

For more information and ideas, see:
Schoolhouse Rock! "Electricity" video on YouTube (also on DVD)
How to Build a Motor
Hand-crank motor
6-in-1 Mini Solar Kit

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Questions and Answers by Subject



Q: What types of genes are most prevalent in cancerous tissues? On the other hand, what types of genes should be prevalent in normal cell tissues that aren't in cancerous tissues? --Julia, Grade 9, Westford, MA. June 2012

Q: Is it true that vestigial structures were used by our early ancestors and not by us today? --Amore, Grade 9, Cambridge, MA. April 2012

Q: What part of the brain makes the electricity to zap the muscle? --Lucas, Grade 2, Framingham, MA. March 2012

Q: What's the difference between DNA and RNA? –Peter, Grade 9, Roxbury, MA. November 2011

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Q: Can you see yourself in a projected hologram of a mirror?  --Kurtis, Grade 12, Lansing, KS. May 2012

Q: How do wingtip devices (winglets) improve the flight performance on an airplane?? --Aaron, Grade 8, (no town given) Georgia

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Q: How do nuclear reactors work? -- Charlton, Grade 7, Murfreesboro, TN. July 2011

Q: Can you use carbon dioxide to power an engine? Don’t plants use it as a fuel source? –Lauren, Grade 5, [no town given] MA. October 2011

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Q: How is math important in science and technology? -- Angel, Grade 10, [no town given] August 2011

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Q:  What are the strange, charm, top, and bottom quarks for? --Graham, Grade 4, Concord, MA

Q: How close are we to achieving nuclear fusion in a sustainable environment? --Notter, Grade 9, Cambridge, MA. September 2011

Q: Can you see yourself in a projected hologram of a mirror?  --Kurtis, Grade 12, Lansing, KS. May 2012

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Earth Science _______________________________________

Q: Can there be an earthquake large enough to knock us off our rotation/orbit and increase/decrease our calendar year? –Virgil, Grade 11, Casselberry, FL. January 2012

Q: How do tornadoes form? --Current event topic based on the tornado in Springfield, Massachusetts on June 2, 2011

Q: What is an ocean current? --Evan, Grade 1, Braintree, MA. May 2011

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Miscellaneous ______________________________________

Q: What do you think is better—PC or Apple? --Eloi, Grade 5, Candiac, Quebec. February 2012

Q: How is radar important in technology? –Zoe, Grade 12, Los Angeles, CA. December 2011

Q: How many planets are in the solar system? --Benjamin, Grade 1, Littleton, MA. April 2011

Q: Why does static electricity make my hair stand up? --Emma, Grade 7, Westford, MA. March 2011

Q: How does the power company make the power that comes to our house? --Ben, Grade 4, Westford, MA. February 2011


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