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Archive for the ‘How does it work?’ Category

How high do fireworks fly?

Posted by drdavescience on July 22, 2009

During a recent fireworks show, a friend had asked me if I knew how high the fireworks fly before it explodes. I didn’t know the answer but I began to wonder how I could figure it out.

fireworks

Judging the height of an object in the sky is not easy without a reference. Maybe if I knew the height of a nearby building or tree? With a height reference I could probably estimate the height of a firework with some accuracy.

Low clouds can be a helpful indicator of height. I can simply gauge the altitude of the firework relative to the cloud. The altitude of a cloud can be found on weather websites like www.wunderground.com.

But wait, what if there are no clouds or buildings nearby?

I gave this a thought and came up with a way to estimate the height using a grade-school trick and math.

Thunderstorms, the Speed of Light and the Speed of Sound

Lightening and thunder occur during a thunderstorm. Lightening is the discharge of electricity between clouds, from a cloud to the ground, or vice versa. Most people don’t see the actual lightening bolt, but they’ll often see a flash. Thunder is the sound a lightening bolt makes and is often heard after a flash is seen.

thunderstorm

In grade school, I learned to tell how far away a lightening strike is by counting the number of seconds between seeing a lightening flash and hearing the sound of thunder. Each second is about 1000 feet (1114 feet to be exact), so if I counted 5 seconds between lightening flash and hearing thunder, then the strike was about 5000 feet away (or about 1 mile).

This trick works because light travels incredibly fast when compared to sound.

What does this have to do with fireworks?

When watching the fireworks show with my friends, I could see the explosion before could hear it. So, just like I do for a thunderstorm, I began counting the number of seconds between the time I saw a firework explode and when I heard the explosion.

Most of fireworks I saw that night had a delay of 2 seconds or less. This corresponds to about 2000 feet. Keep in mind that this does not mean that the fireworks fly 2000 feet high. Take a look at the diagram below:

FireworkTriangle

(Please forgive the quality of the diagrams in this post as I made them while eating lunch at work.)

As you can see from the diagram, I drew a triangle to help me solve the height problem.

Notice that the 2000 feet I estimated using the timing trick corresponds to the distance from me to the fireworks. In geometry speak, this is called the hypotenuse, the longest side of the triangle. You can also see that the other two sides of the triangle corresponds the height and my distance to the launcher, which we don’t know. Now, let’s figure out the height using trigonometry.

Wait…trigonometry!?! That’s a scary word!

Actually, trigonometry is not a scary word once you know what it means. “Trigon” refers to a triangle and “ometry” refers to measuring. Are you afraid of measuring triangles? I didn’t think so.

Several thousand years ago, some clever people figured out how to solve problems like ours using triangles. Even to this day, triangles are used to solve problems in engineering, medicine, architecture and aviation.

How to solve our problem?

When dealing with a triangle, we can use some easy rules of trigonometry to figure out our problem. For instance, there are two useful right triangles (triangles with a 90° angle) that can make problem solving really easy. These two triangles are the 30°-60°-90° right triangle and the 45°-45°-90° right triangle shown below:

right-triangles

In these two types of triangles, the sides exist in a fixed ratio. Always! This means, if you know the length of one side, and an angle, you can figure out the length of the other sides by using the ratios.

Back to the fireworks problem

To figure out the height of the firework, I need to figure out how much I tilted my head to see the fireworks. This will help me figure out which triangle to use. Since this is an estimate, it’s okay to guess. I know I wasn’t craning my neck up or looking straight ahead. I’d guess that I was looking about 30° to 45° up.

Take a look at the diagram below:

Solved Right Triangles If I was looking about 30° up, I would use the 30°-60°-90° right triangle. Using the ratios, a hypotenuse of 2000 feet would correspond to a height of 1000 feet.

If I was looking about 45° up, I would use the 45°-45°-90° right triangle. Using the ratios, a hypotenuse of 2000 feet would correspond to a height of 1414 feet.

Therefore, using the thunderstorm timing trick and trigonometry, I would estimate that fireworks I saw that night flew up to about 1000 to 1500 feet.

Keep in mind that approach is not perfect, that’s why it’s an estimate. An estimate gets us close to the exact answer. There were issues about timing between seeing and hearing the explosion, the angle the firework was launched, as well as effects of the wind.

Even if we had the exact data, we would still use trigonometry to solve the problem.

Enjoy!

Dr. Dave

Posted in How does it work?, Math, Physics, Problem Solving, Uncategorized | Leave a Comment »

Mutant Bacteria!

Posted by drdavescience on April 3, 2008

There has been a lot talk in the news about MRSA, which stands for Methicillin-Resistant Staphylococcus Aureus.

Scientists often call MRSA a “superbug” because it no longer can be killed by a certain kinds of antibiotics related to penicillin.

How is it that bacteria become “superbugs?”

Bacteria are tiny, one-celled organisms that come in many shapes and sizes. All bacteria use DNA as the blueprint of life and have tools (called enzymes) to copy itself when ample nutrients are present.

Before copies can be made, a bacterium has to duplicate its DNA. An enzyme called DNA Polymerase (the horseshoe shaped object shown in green in the picture above) accomplishes this task. This enzyme is found in bacteria, insects, plants, animals, and even humans!

When making copies of DNA, most DNA Polymerases can proofread the blueprint to check for errors. Human and plant Polymerases are very good at finding errors, but some bacterial Polymerases are not. If an error does occur in the blueprint, scientists call this a mutation.

Mutants!

When people hear the word “mutant” they think of X-men or the Teenage Mutant Ninja Turtles. Although this is science fiction, Hollywood has shown that there are good mutants and bad mutants. The same applies to bacteria.

For example, scientists have engineered good mutant bacteria that can make insulin, a hormone used by diabetics to control blood sugar levels.

An example of a bad mutant bacterium is MRSA, which we talked about above.

More About Mutations

The DNA blueprint holds the master plans for all the machinery required for a cell to function properly. If there is a mutation in the blueprint, there is a chance that a cell’s machinery of life will be altered, and it can result in one of three possible outcomes:

1. The altered machinery continues to function normally.

2. The altered machinery is faulty and can cause bacterial death.

3. The altered machinery is enhanced and it helps the bacteria survive harsh conditions.

Survival of the Fittest!

Harsh conditions could mean a variety of things to bacteria, from low nutrient levels to the presence of antibiotics.

We already know that antibiotics can kill bacteria, but what happens if a mutation helps the bacteria survive? Scientists call this resistance.

Bacterial resistance to antibiotics is a very scary thing. Diseases that were once curable are now becoming a challenge to control.

The world’s best scientists are working hard to discover new kinds of antibiotics. Hopefully there will be breakthroughs that will lead to new medicines that will control the spread of these lethal bacteria.

-Dr. Dave

Posted in Health, How does it work? | 2 Comments »

Indiana Jones and the Mystery of the Cracking Whip

Posted by drdavescience on March 3, 2008

Indiana Jones and the Raiders of the Lost Ark is my favorite movie. I was watching it (again), and a friend asked me why a whip makes that characteristic “crack” sound. As a reminder, below is a YouTube video montage of Indiana Jones’ favorite weapon.

Where does the sound come from?

When you move something through the air really fast, it typically makes a “whoosh” kind of sound. If you swing a bat very fast, you can hear this sound. This is just the air moving around the bat. Cars and planes also make their own “whoosh” kind of sound, but no “crack” sound.

The distinctive whip “crack” sound occurs when the tip of the whip is moving at supersonic speeds.

This means that the tip of the whip is breaking the sound barrier! Isn’t that cool!

A similar sound is made when a fighter jet breaks the sound barrier. Check out this You Tube video of a fighter jet breaking the sound barrier.

I mentioned that only the tip of the whip moves at supersonic speed. As Indiana swings and snaps the whip, all of the energy of motion moves down to the tip and causes it to changes directions rapidly. When done properly, it cracks.

-Dr. Dave

Posted in Check it out!, Fun Facts!, How does it work?, Physics | Leave a Comment »

Heavy Metal Glider

Posted by drdavescience on January 27, 2008

In mid-January, a British Airways 777 landing at London’s Heathrow Airport crash-landed short of the runway. When the jet was 600 feet above the ground (about 2 miles from the runway) the engines stopped responding – it effectively became a big glider.

Most jets fly at about 150 mph during the landing phase. In the scenario I described above, the pilots had less than 30 seconds identify the problem (the engines had stopped responding), have the cabin crew prepare the plane for an emergency and glide it towards the runway. The plane touched down short of the runway and sustained major damage, but the most important thing is that nobody was seriously injured. The landing had more to it than just luck, and the pilots and the crew did a great job,

Gliding and Training

Some people seem to think that when the airplane’s engines stop, the plane will drop out of the sky. It is not well known is that all airplanes are designed to glide. In fact, big jets are very efficient gliders; with a lot of altitude, a big jet can glide far. I’ll talk about a few examples later in this article.

Pilots are trained to handle all sorts of emergencies when they first learn how to fly. In fact, during my own private pilot training, my flight instructors taught me how to handle engine failures. This was the most nerve-wracking emergency to practice because I had one chance to land safely.

Notable Airliner-Gliders

In 2001 a Air Transat flight 236 was flying from Toronto, Canada to Lisbon, Portugal. Somewhere across the Atlantic, the engines failed due to fuel starvation (the pilots did not notice there was a slow fuel leak due to a faulty part). Starting at about 30,000 feet, the pilots managed to glide the airplane for about 20 minutes to a safe landing in the Azores. Impressive!

In 1982, a British Airways 747 flew into volcanic ash and all four engines failed. The plane was at 37,000 feet and it was able to glide down to about 13,000 feet (about 12 minutes) before the crew restarted 3 of the engines and landed safely.

The Glide Ratio

All airplanes come with a manual that is full of charts that help pilots predict an airplane’s performance during take-off, cruise, and landing. There is also a section that indicates the airplane’s glide ratio. A glide ratio indicates how many miles the airplane will glide over a given altitude loss. For example, the small plane I fly, a Diamond Star, has glide ratio of 1.4 miles per 1000 feet of altitude lost.

A 747 has a glide ratio of about 2.8 miles per 1000 feet of altitude lost at its best glide speed. This means that a 747 cruising at around 35,000 feet can glide almost 100 miles if it loses engine power!

Modern airplanes are very reliable. Several thousand aircraft are flying everyday without incident, which is a testament to the high standards of pilot training and maintenance.

Keep up the good work!

-Dr. Dave

Posted in How does it work?, In the News, Physics | Leave a Comment »

Heat Transfer in the Kitchen

Posted by drdavescience on December 26, 2007

Merry Christmas! I apologize for the lack of posts. Things are very hectic because I am finishing my Ph.D. and looking for jobs. Both tasks are very time consuming.

I would like to thank people who read my posts and send nice comments. I am glad to know that my ideas and explanations are having an impact in people’s understanding. Your kind notes inspire me to write more posts.

Happy 2008 to everyone!

-Dr. Dave

—–

In honor of Remy, the culinary genius from the recent Disney/Pixar movie Ratatouille, I will discuss the science behind cooking.

Cooking is one of my favorite forms of science because in the end, you can eat your experiment.

A great chef is both a scientist and an artist. They constantly experiment with different combinations of flavors and foods to create fantastic tasting meals. Do you remember the last time you had a really great pizza, or had a fantastic desert that knocked your socks off? What made it taste so good?

The science of heat

Cooking is the transfer of heat energy from some source to the food. In the kitchen there are three devices that are used to cook food: the stovetop, conventional oven, and microwave oven. Each of theses devices are designed around a different method of heat transfer.

The movement of heat is so important that there is a name for it: Thermodynamics. By understanding how heat moves, we can gain insight into our everyday world. It is responsible for the weather, car engines, your refrigerator, cooking, and a host of other things that you may not have even thought about.

Heat is transferred in three basic ways listed below:

Conduction is heat transfer through direct contact. When cooking on the stovetop, the heat from the flame or electric grill is applied directly to the frying pan. This means that only the flat surface of the pan is sufficiently hot enough to cook anything and we must flip and toss around the food to cook it properly.

It is important to note that most pans are made of metals, like copper, that conduct heat very efficiently and do not melt on the stovetop.

Convection is heat transfer through a fluid. The fluid can be liquid or gas and in the case of a convection oven, the fluid we care about is air.

A convection oven is a confined area that gets hot by flames or electric coils. The air inside is warmed to a desired temperature and, as a result, cooks the food from all directions. This method of heat transfer is responsible for pizzas, cakes, and other baked treats!

Keep in mind that convection ovens heat foods from the outside. The inside slowly heats up with time, and it is not uncommon to see food where the outside looks done, but the inside is uncooked. This is very important when preparing a Thanksgiving turkey, and there are special thermometers that measure the temperature of the food in the center of the turkey to show that it is properly cooked.

Radiation is the transfer of heat using electromagnetic radiation. A microwave oven uses very strong radio waves (a form of electromagnetic radiation), which are very weak and not hot. So how does it work?

Microwave ovens work by spinning water, fats, sugars and oils inside the food. This causes friction, which then heats the food and cooks it from the inside.

Please do not be confused by the word radiation or electromagnetic radiation. In science, these terms are very general and mean a lot of things. Radiation comes from many sources, some are beneficial and others are harmful. For example, solar radiation from the Sun is responsible for heating the Earth and the light we see is a form of electromagnetic radiation.

As you know, heat is very important in the cooking process. Now you have the basic knowledge of heat transfer.

Look at the world around you. Don’t be afraid to ask, “How does that work?” Be curious and seek help from people willing to help you (like me).

Let your curiosity guide you through this everyday world.

-Dr. Dave

Posted in Cooking, How does it work?, Physics | Leave a Comment »

How do NFL quarterbacks throw footballs far and accurately?

Posted by drdavescience on September 13, 2007

The NFL regular season is in full swing and hopefully your favorite team is showing their talent on the field. Are they Super Bowl bound? Only time will tell.

In football, one of the most exciting plays is the “Hail Mary” pass. This is when a quarterback throws the football really far (50 yards or more, that’s 45.72 meters for my metric readers) and somehow the receiver catches it.

Check out this YouTube example of Doug Flutie’s famous Hail Mary pass.

Is the “Hail Mary” muscle power or physics?

I still remember when I learned how to throw a football. At first, my throws were wobbly and the football did not travel very far. My dad showed me how to throw the ball in a spiral, and with a little practice I was throwing the ball much further.

Although I was throwing the ball with the same strength, I realized that spiraling helped the football fly better.

Naturally, I wondered “Why does spinning help a football fly better?”

Spin stabilization

By throwing a football with a spiral (no wobbles at all), the ball spins around an imaginary line that traces its path through the air (the axis of flight). This reminds me of a gyroscope.

What is a gyroscope?

A gyroscope is a wheel on an axle that spins really fast. The spinning allows it to resists external forces (like wind or sudden movements). The faster a gyroscope spins, the more stable it becomes. Take a look at these videos I found on YouTube.

Notice how this toy gyroscope stays standing while it spins, even when it is turned!

This is another cool video showing how gyroscopes resist external forces. The spinning wheel prevents it from falling over. Does this make sense?

The gyroscopes in these videos are spinning at about 200 times every second!

Did you know that gyroscopes are used in airplanes, spacecraft, and even the Hubble Space Telescope (shown below)?

In the Hubble Telescope, advanced gyroscopes are used to help determine what part of space it is pointed at. Remember, in the absence of gravity, there is no up or down!

Rockets and Artillery

When rockets were first used in combat in the 1200s, they had a tendency to veer off course. It was not until the middle 1800s when people realized that if they spun the rocket as it flew, it would fly more straight and true.

In fact this idea has also been applied to artillery. The barrel of the big guns on battleships had grooves inside them that would spin the shell when it was fired. This greatly improved accuracy of the shell as it was now less susceptible to the effects of the wind.

This is a picture of the USS Wisconsin. The guns on this ship shoot shells that are 16 inches wide!

Putting it all together – Spinning the Hail Mary

When a football spins as it travels through the air, it will fly a more stable path and be able to resist the effects of the wind. This makes the throw more accurate.

Also, the faster the ball spins, the more stable it is during its short flight from the quarterback to the receiver’s arms.

Now you know how NFL quarterbacks can throw a ball accurately!

While strength is important for providing the force behind the throw, physics plays a significant role in both distance and accuracy.

That’s cool.

-Dr. Dave

Posted in How does it work?, Sports | 1 Comment »

Why do some foods give me gas?

Posted by drdavescience on September 5, 2007

-Anonymous, USA
———————

I am sure many people will giggle at this question, but it is an excellent example of everyday science!

Gas is a natural by-product of consuming food and digesting it. The body relieves the build-up of gas pressure by belching (burping) or flatulence (farting). People are embarrassed to admit they burp or fart and some even claim that they do not pass gas. If this were true, they would inflate like a balloon and suffer terrible abdominal pains. Ouch!

Belching (burp!)

Belching is the release of air that gets trapped as we chew and swallow our food. If you drink carbonated beverages like Coke and 7-Up, you will burp the carbon dioxide gas that makes the drink fizzy. Some people can burp on demand simply by swallowing air.

Flatulence

Our anonymous friend has noticed that certain foods make them flatulent. Perhaps you may have noticed that beans, cabbage, high fiber breads and cereals give you gas. In general, this holds true for many people.

Let us take a look at how our bodies make gas.

The digestion process

Digestion begins once we put food in our mouth. The process of chewing physically mashes food and mixes it with enzymes (more on enzymes later) that fragment complex sugars. Once the food reaches the stomach, it is tossed around in very strong acid, breaking apart proteins, sugars, and fats into more manageable pieces.

Afterwards, the processed food is passed into the small intestine, where the nutrients and water are absorbed and the waste is passed on. The cells lining the intestines use enzymes to crack apart complex sugars so they can be absorbed easily.

Our bacterial friends

Inside our intestines live bacteria called Escherichia Coli, or E. coli for short. Our bacterial buddies assists in food absorption, waste processing and vitamin K production (a chemical that helps your blood to clot when you get cut). These bacteria are also responsible for making gas in your digestive tract, and…farts.

Here is a picture of E. Coli taken by an electron microscope.

Before you blame E. coli for all you flatulent woes, we need to understand why it makes gas.

Here is where things get interesting!

Enzymes

As I mentioned in the Antibiotics discussion, bacterial cells and our cells have similar machinery of life. Some of these machines are called enzymes.

Enzymes are proteins that perform the chemical reactions of life. There are many kinds of enzymes, each having a very specific function. Some enzymes only work with DNA, some with sugars, others only send signals.

Sugars!

Sugars are complex chemicals that are made by most living things, from bacteria to plants to humans!

Sugars are the universal source of chemical energy that makes life possible.

There are many different kinds of sugars with names like sucrose (table sugar), lactose (milk sugar), glucose, and fructose.

Here is a picture of table sugar from my kitchen.

Did you know that different sugars have different levels of sweetness?

It’s true!

A group of scientist figured out how to measure the relative sweetness of various sugars.

For example, they determine that fructose is about two times sweeter than sucrose (table sugar). This means that if you are making a sweet drink then you can use less fructose than sucrose to sweeten it. This is why most drink manufacturers use high fructose corn syrup instead of sucrose!

“Right-handed” sugars and “left-handed” sugars!

Many sugars can be “right-handed” or “left- handed.” This means they are mirror images of each other. An example of a mirror image is our hands.

Putting it all together!

Most sugars in nature are made in the “right-handed” version only. The enzymes in our intestines can only react with “right handed” sugars.

E. coli that live in our intestines can digest both right and left-handed sugars.

Foods like beans, cabbage and high grain breads and cereals contain “left-handed” sugars that only the bacteria can process.

When bacteria digest sugars, they make gases like carbon dioxide and methane. This is flatulence!

Now you know why certain foods cause gas!

-Dr. Dave

Posted in Fun Facts!, Health, How does it work? | Leave a Comment »

Why are antibiotics useless against the cold and flu?

Posted by drdavescience on August 26, 2007

In 1928, Sir Alexander Fleming’s discovery of penicillin ushered in a medical revolution. For the first time, a drug was available to combat ancient scourges like the bubonic plague, leprosy, and tuberculosis, which were caused by bacteria.

Below is an illustration of a bacteria.

Although penicillin was very potent, it was limited in kinds of bacteria it could kill, and therefore, what diseases it could cure. Fortunately, scientists worked hard to develop the modern assortment of powerful antibiotics that we have today.

What are antibiotics?

Antibiotics are drugs that kill microorganisms. For something to be killed, it must first be alive.

Bacteria are alive because they have the basic machinery of life contained within a cell. This machinery allows microorganisms to make energy from sugar, read and copy DNA, make proteins, and reproduce.

Antibiotics work by destroying a bacteria’s machinery of life.

By destroying this machinery, bacteria will no longer be able to live.

Did you know that the machinery inside a microorganism is similar to machinery that is inside all of our cells? The antibiotics we take are chemicals that are specifically designed to destroy bacterial machinery and not our own! The next time you have to take an antibiotic, think about all the hard work put forth by biologist and chemists to make certain that you don’t get hurt when taking this medicine.

Viruses

Viruses are smaller than bacteria and come in many shapes and sizes. In general, viruses have a protein coat, called a capsid, which protects the genetic blueprint (either DNA or RNA) on the inside.

Below is a cutaway illustration of the influenza (flu) virus.

Viruses lack the machinery to make energy, read and copy DNA, make proteins, and reproduce. Therefore, viruses are not alive!

***Antibiotics cannot kill a virus because it does not have any machinery of life!***

If a virus is not alive, then how do we get sick?

Viruses are the cause of the common cold and flu (influenza). To make us sick, a virus needs to insert its genetic material inside our cells. Once the viral DNA or RNA is inside a cell, it will use our cell’s machinery to construct copies of the viruses. DNA and RNA are the universal blueprints of life so our cells are unable to distinguish the viral genetic information from our own.

The cell will keep making copies of the virus until it runs of resources while pushing out the newly made viruses. Sometimes the cell will die during this process.

The only way to destroy a virus is to take an antiviral drug or have our immune systems destroy it (a subject for later post).

Now you know why the cold and flu cannot be cure by antibiotics!

-Dr. Dave

Posted in Health, How does it work? | 1 Comment »

Hurricanes and Latent Heat

Posted by drdavescience on August 21, 2007

Whether we like it or not, it is hurricane season. These giant storms generate strong winds and heavy rains that are capable of extreme destruction.

This is a picture of Hurricane Dean from www.wunderground.com.

Do you know what fuels a hurricane?

Most hurricanes begin as small storms that form in the warm waters of the Atlantic Ocean, as far away as the western coast of Africa. These small storms grow in both size and intensity at an alarming pace when they are exposed to enough heat, moisture, and unstable air.

This track of all the named Atlantic storms in 2006. Storms get named only when it reaches the size of a Tropical Depression. Some storms grow, some lose strength. Take a look!

A hurricane cannot form on land because it needs an open body of warm water – like the Atlantic Ocean at the end of summer – for it to grow. Instead, dangerous thunderstorms and smaller spinning storms, like tornadoes, will form on land.

Heat from the sun helps to warm the ocean’s waters to provide energy to establish the best conditions to create a hurricane. The latent heat (see what this is below!) of water helps the feed a hurricane’s strength and intensity once it forms.

What is Latent Heat?

Things in our everyday lives are almost always either solid, liquid, or gas. These are the three phases of matter. Depending on how much the temperature changes, the phase can change. Water is an excellent example of something that we have seen in three phases:

Solid – Ice in the freezer
Liquid – Water from the tap
Gas – Steam above a boiling pot of water

When matter changes phases heat is either given off or absorbed. This is called latent heat.

Check out this illustration from http://www.physicalgeography.net.

Let’s take a closer look at latent heat so we can understand why it is so important.

According to the illustration, heat is absorbed when a solid changes into a liquid. Even more heat is absorbed when a liquid changes into a gas.

Let us imagine that we fill a pot with ice cubes. We know that ice will melt outside of the freezer. The ice is literally absorbing heat from the air! To turn a pot of water into a gas (steam), it has to be heated on a stove and boiled.

What happens when liquid changes into a solid or a gas changes into liquid?

We know that heat must be absorbed to melt ice or boil water. So if we want to make ice or condense steam, then this means that heat has to be given off or removed.

Making Ice
If you fill a cup with water and place it in the freezer, after a few hours it will turn into ice. How does this happen?

Although a freezer/refrigerator is cold, it is a heat pump: it absorbs heat from the things inside it (making it cold) and pumps the heat outside! Have you ever noticed how hot it gets behind a refrigerator?

This means that heat is given off when changing from a liquid to a solid.

Condensing Water Vapor
When a gas turns in to a liquid, heat is also given off. If you take a glass of ice water outside on a hot and humid day, water vapor from the air will touch the cool surface of your glass and immediately turn into liquid water. The heat given off by this phase change causes the ice in the glass to melt faster than if was sitting in warm air alone.

So what does this have to do with hurricanes?

As I mentioned before, hurricanes need heat, moisture, and unstable air to grow and become powerful.

At the end of summer, the water of the Atlantic Ocean reaches its highest temperature. This causes the ocean’s water to evaporate more than usual, putting more water vapor in the air. Eventually, the water vapor will cool and condense to form clouds. This means that heat is given off in the sky.

This occurs over huge area of the ocean, meaning that the sky is being heated more than usual. From the “How does a hot air balloon work” discussion, we know that hot air rises. To a weather scientist, too much hot air is a sign that the sky is unstable.

Did you know that an easy way to tell if the air is unstable is to look for tall puffy clouds in the sky? This is often a sign of bad weather!

When a storm system enters this heated area, it causes the storm to grow both outwards and up into the sky. The hotter the air gets, the stronger the storm becomes. If the heating continues, a small storm can grow into an extremely powerful hurricane many hundreds of miles wide!

To learn more about hurricanes, NASA has a great website on hurricanes with links to interesting videos and information.

NASA’s Hurricanes Main Page

This link has a short 8 minute video with cool animations that is very informative.

This link has an amazing video of Hurricane Katrina. Notice how the hurricane looks small at the beginning of the video before it hits Florida and then grows to a huge size over the warm waters of the Gulf of Mexico. I am amazed and scared by the power of nature!

-Dr. Dave

Posted in Check it out!, How does it work?, Weather | 4 Comments »

How does a microwave oven work?

Posted by drdavescience on July 31, 2007

Sorry about the delay in posting. There has been much to do in the scientific world of Dr. Dave. Plus the last Harry Potter book came out and, well, I had to read it.

In an earlier post about Pyroceram, I said I would explain how microwaves work. As promised, here it is!

Microwave ovens are a cool invention that makes cooking food really simple and fast. You can use a microwave oven to heat things in a matter minutes compared to the longer cooking times in a normal oven (called a convection oven).

So how does a convection oven work?

Convection ovens work by heating the air inside it using fire or electricity. When heated to the desired temperature, food is placed inside so it can cook.

Have you ever thought about how food cooks in an oven?

Let us imagine we are baking a cake.

After making the batter, it is poured into a pan, which is placed inside a preheated oven. The hot air surrounding the cake batter warms the outside first. Eventually, the insides will get hot. If you do not bake it long enough, the outside may look like it is ready, but the insides could still be batter!

Microwave ovens, unlike a convection oven, do not get hot. Instead, it uses microwaves (strong radio waves), which have the special ability to pass through things like ceramics, glass, and some plastics. More importantly, microwaves have the ability to make water, sugar, and fats inside your food spin and move.

So how does the food get hot?

Try this little experiment. If you rub together really fast, your hands will get warm because of friction.

Now imagine the water, sugar, and fats inside of your food rubbing against each other millions of times every second. Most food gets cooked in a microwave for one or two minutes. That’s 60 to 120 seconds, which means that the water, sugar, and fats in your food is causing a lot of friction, which makes heat that can cook your food.

If you think about it, microwaves ovens cook your food from the inside!

Now that’s cool.

-Dr. Dave

Posted in How does it work? | Leave a Comment »

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Archive for the ‘How does it work?’ Category

How high do fireworks fly?

Mutant Bacteria!

Indiana Jones and the Mystery of the Cracking Whip

Heavy Metal Glider

Heat Transfer in the Kitchen

How do NFL quarterbacks throw footballs far and accurately?

Why do some foods give me gas?

Why are antibiotics useless against the cold and flu?

Hurricanes and Latent Heat

How does a microwave oven work?