Wednesday, September 5, 2007

Why do some foods give me gas?

-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.



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!


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 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

Monday, August 27, 2007

What are Maraschino Cherries?

-Brian, from Chicago

Hi Brian!

Maraschino cherries are the bright red cherries found on top of ice cream sundaes. Its sweet taste and bright red color leads many people to believe that it is artificial or manufactured.


Since I like Maraschino cherries, I decided to look more into where this sweet topping comes from.

How it is made

Maraschino cherries are real cherries that are pickled (in brine, just like pickles). When ready, the cherries are transferred into a syrup of sugar containing a natural red dye. The cherries absorb the sugar and color, giving a sweet flavor and bright red color.

Different flavors and colors can be added to make the cherries appear and taste different. Maraschino cherries typically have almond extract in the syrup. It is also not uncommon to find cherries with a mint taste, which comes from adding peppermint oil to the syrup.

The cherries are then packed in a jar filled with the syrup, sealed, and shipped out, eventually finding their way to sundaes across the nation.


Maraschino cherries are obviously not grown on trees. It is processed with natural ingredients to give the final taste and color. While these cherries are not good for you, I am sure the soda or ice cream that it came on is worse.


Dr. Dave

Sunday, August 26, 2007

Why are Antibiotics Useless Against the Cold and Flu?

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 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

Tuesday, August 21, 2007

Hurricanes and Latent Heat

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

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

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

Tuesday, July 31, 2007

How Does a Microwave Oven Work?

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

Tuesday, July 10, 2007

A Jet Plane Made of Plastic and Fabric!

Boeing unveiled its new 787 Dreamliner on 7/8/07. At first glance, it looks like other airplanes, only sleeker. The Dreamliner is truly different, both inside and out.

The 787 is set apart from other passenger jets because it is built from composite materials. According to the Boeing website, the 787 is half composite, which is much more than any passenger jet ever made!

What are composites?

Composites are materials that are made of two or more things that have different physical properties. Bricks, made of mud and straw, are an example of composites used long ago by the ancient Egyptians.

Why are composites important?

Let us imagine what would happen if we built a home using only straw or only mud.

A home built of straw alone would probably blow away (remember the story of the Three Little Pigs?).

A home built from dried mud would not last very long because the bricks would eventually fall apart.

When both straw and mud are mixed together, they work together. Straw provides a matrix, or a support structure, that mud can hold on to so it does not fall apart. The mud makes the straw stronger by filling in the empty spaces around the straw fibers. Buildings made from composite bricks by the Egyptians were strong and lasted a very long time.

Although modern composites are much more advanced, they work by the same principle: two different materials mixed together to make a much stronger final product.

The composites used in the Dreamliner, called Carbon Fiber Reinforced Plastics (CFRP for short), are among the most advanced composites used today.

What is CFRP?

Carbon fiber is a long thin thread of a carbon polymer that is bundled together in small ropes. Each individual thread is very strong, and when it is bundled, it is even stronger!

I think of carbon fiber as the straw in the brick example above.

The carbon fiber ropes are then weaved together to make a fabric.

Here is what carbon fiber fabric looks like:

The fabric is then coated in a special plastic and molded into the desired shape. Depending on how the threads are weaved and the type of plastic used, CFRP of different strengths can be made.

CFRP is very strong and very lightweight; it has been used to make bike frames, boat hulls, race cars bodies, kayaks, laptop computer cases, musical instruments, plane parts, and skateboards!

Composites like CFRP have been use to manufacture passenger airplane parts for over a decade. Smaller private planes like the Diamond Star (the kind I fly) has a body that is made almost entirely of composites.

Here is a picture of a Diamond Star:

The 787 Dreamliner is the first large passenger jet to have its body made mostly of composites. This will help to keep the airplane’s weight low so it can carry more passengers and fuel, allowing it to fly very far.

Here is a picture of the piece of the 787 composite body.

There is a small company called Scaled Composites that has been using composite materials to makeinteresting planes for a long time. Scaled Composites was responsible for designing and making the Voyager, Global Flyer, and (my favorite) White Knight and Space Ship One.

This a picture of White Knight carrying Space Ship One.

From skateboards to the 787 Dreamliner, composites have found multiple uses in our daily lives. All of this is made possible by science.

Dr. Dave

Sunday, July 8, 2007

How Do Hot Air Balloons Fly?

To explain how hot air balloons fly, ask yourself the following questions:
  1. Is your home is warmer upstairs than it is downstairs?
  2. Have you ever noticed that the hot air from smoke stacks always goes up into the sky?
This occurs because warm air rises and cold air descends.

Now, if that warm air could be captured and kept warm, then we'd have a hot air balloon!

Here's a picture of a hot air balloon:
How is it flown?
Hot air balloon pilots control their altitude changing the temperature of the air inside the balloon.

Use the following illustration as a guide to a hot air balloon:
To gain altitude, pilots use burners to warm the air inside of the envelope (the balloon).

To reduce altitude, pilots open vents at the top of the balloon to slowly release the warm air.

The direction of flight is controlled by the wind.

This YouTube video has a good information on hot air balloons:

You can read more about hot air balloons here.

Pretty cool!

Dr. Dave

Monday, July 2, 2007

From the Space Program to your Kitchen!

You may have a high-tech piece of cookware sitting in your kitchen!

In the 1950s, scientists developed a glass-ceramic material called
Pyroceram©. It probably looks very familiar to you. This material is heat resistant, durable, and invisible to radar!

This stuff was once used by the military and space program. My favorite use? Missile nose cones!

Pyroceram © was later used in kitchens because someone realized that it would make great cookware. It has changed names over the years, but Corning is the company that continues to use this technology – unbeknownst to moms everywhere!

I think the coolest part is that it is invisible to radar. This feature makes it perfectly suited for use in a microwave oven.

Microwaves and radar are related. Because Pyroceram is invisible to radar, this means that it is also invisible to microwaves. 

I think it’s really cool that dinner could be served in something that evades radar like the B-2 stealth bomber!
That's what I call everyday science. Pretty cool!

Dr. Dave

Sunday, July 1, 2007

How Does Sunscreen Work?

The sun is a gigantic atom-smashing machine that makes heat and light. It is the reason why you can enjoy a day at the beach or a dip in the pool, especially on a hot summer day.

The sun also emits harmful UV rays that are responsible for sunburns; too much exposure can cause skin cancer.

What’s Inside?
Sunscreen contains chemicals that reflect or absorb harmful UV rays. When applied to the skin, the thin layer of sunscreen does not allow UV rays to touch your skin.
Sunscreen has to be reapplied every few hours because swimming and sweating washes it off. Did you know that UV rays also damage the chemicals in sunscreen? It’s true! Sunscreen works because the chemicals are being sacrificed to save the skin!

Why do some lifeguards look like they are wearing white paint on their nose?

That white stuff is zinc oxide; another common chemical is titanium dioxide. Both of these chemicals reflect UV rays.

Other kinds of chemicals absorb UV rays. These have funny names like oxybenzone and avobenzone. There’s a long list of chemicals found in different sunscreens.

Did you know that these chemicals are also found in lip balm, lotions, and make-up?

If you feel adventurous, read the ingredient label on the back of a box. I know that there are many funny chemical names, but look for the ones you know!

How do you know the strength of the sunscreen? The standard is called Sun Protection Factor, or SPF.

Sunscreen with a higher SPF rating means that it has more chemicals in it that absorb or reflect UV rays.

Dr. Dave’s Tips
  • Wear sunscreen if you are going to be outside for a long time.
  • Reapply sunscreen after swimming.
  • Wear a hat and sunglasses to protect your eyes!
That’s all for now!

Dr. Dave