Binghamton University - Ask a Scientist

How many people are on the earth? What is the limit?

Thu, 23 May 2013 00:00:00 -0400

When my grandfather was born in 1922, there were approximately 1.9 billion people in the world. Today, my grandfather is 91 years old, and the population of our planet is estimated at 7.07 billion by the United States Census Bureau. Ten thousand years ago, toward the end of the last ice age, humans numbered only several million. It is enlightening, though, to consider the growth of humanity in the scope of how long it has taken for the population to double in the past.

It has been estimated that the number of humans was 500 million in 1500. For reference, the United States currently has roughly 316 million residents. In 1804, 304 years later, the earth's population reached 1 billion, and took 123 additional years to reach 2 billion in 1927. From that point, it would take only 47 years for another doubling of the population to take place. That occurred in 1974 when we hit 4 billion people.

According to the United States Census Bureau, the 7 billionth person was born somewhere in the world on March 21, 2012. This is of course a symbolic date as there is no way to know exactly how many people are on the earth at any given time. We are, however, projected to reach the 8 billion mark sometime in the mid-2020s.

The relatively recent population explosion is due in part to the advancement of medicine and agricultural techniques. These resulted in a lower infact mortality rate, a higher average life expectancy, and the ability to increase crop yield with an exponentially increasing populace.

Many scientists believe that Earth has a maximum carrying capacity of between 9 and 10 billion people. To calculate this rough number, we have to consider not only the space available for humas to live, but more importantly, the ability of the earth to produce food to sustain such a population.

Farming in the 21st century requires fertilizers rich in nitrogen and phosphorus, as well as the dedication of millions of square miles of arable land. Crops and livestock also have an absolute requirement for clean, desalinated water. These are finite resources. In the United States, we have the privilege of going into a store and buying food, or turning on the tap and utilizing a seemingly endless supply of water. However, we trick ourselves into thinking that these resources are limitless Even today, over 780 million people lack access to clean drinking water. Of course, invention and innovation in the coming decades should allow humans to make better us of these precious resources, and could potentially increase the assessed carrying capacity of the earth by several billion people.

Why does baking soda mixed with vinegar fizz a lot?

Fri, 10 May 2013 00:00:00 -0400

A curious, but great question Alex! Although fun to watch, the fizz you observed when baking soda and vinegar are put together, actually has some cool science behind it! In the world of chemistry, baking soda is called sodium bicarbonate and vinegar is known as acetic acid. Vinegar has a sour taste because it is an acid; remember putting a lemon in your mouth?

Combining two chemical substances (like baking soda and vinegar) to produce a new chemical substance (like the fizz!) is called a chemical reaction.

Our reaction actually takes place in two steps: 1) The substances react to produce carbonic acid. 2) Carbonic acid is very unstable, so it decomposes into carbon dioxide, sodium acetate and water. The bubbles that you see in the fizz are just carbon dioxide molecules trying to escape the solution. Carbon dioxide is much heavier than air, so it flows out freely if the fizz overflows, creating a solution of sodium acetate and water.

Baking soda and vinegar are important items that are found in almost every kitchen. Some of those tasty cakes and croissants that we all enjoy are so fluffy, because of the fizz-like reaction that occurs during baking. When added to raw dough, baking soda in the dough will react with any acidic substance including chocolate, yogurt, buttermilk, sour cream, fruits, honey, etc., to produce carbon dioxide, just like we discussed earlier. The carbon dioxide tries to escape from the dough and ends up giving fluffiness to the baked product. Sodium acetate is formed only when the acid is vinegar, but other acids may have other by-products.

The best way to learn something is to do it yourself, so here is a fun activity for you to try under the supervision of an adult. All you will need is a balloon, an empty one-liter water bottle, some baking soda and vinegar. Add about 3-4 tablespoons of vinegar to the empty one-liter bottle, keeping the bottle upright. Next, place 1 tablespoon of baking soda into the balloon.

Now carefully stretch out the balloon over the bottle's mouth so that the baking soda from inside the balloon will fall into the vinegar. What do you see happening? Try and compare the result with using only half the amount of baking soda and vinegar.

"Do mermaids exist?"

Thu, 02 May 2013 00:00:00 -0400

When animals from two different species are combined, the result is called a hybrid. Although this is a rarity in nature, scientists have experimented combining animals from various species to create new hybrids. For example, a mule is a cross between a horse and a donkey, whereas a liger is a cross between a lion and a tiger.

Throughout history, people have imagined creatures that are part human and part animal. Mermaids are just one of many mythological humanoids. The sphinx and centaurs are other well-known examples. The idea of a mermaid, a human and fish hybrid, has been around for quite some time. According to the National Oceanic and Atmospheric Administration (NOAA), mermaids first appeared cave paintings during the Stone Age, 30,000 years ago. Since then, there have been countless reports of mermaid sightings. Were these sighting simply cases of imaginations running wild?

The producers of the televisions series, "Mermaids: The Body Found" featured on Animal Planet, seem to think there could be some truth to the reports. The depths of the ocean are less explored that the surface of the moon and the new species are being discovered each year. The TV series explored a controversial evolutionary theory known as the Aquatic Ape Hypothesis coined by marine biologist, Alister Hardy in 1960.

This theory supports the possibility that mermaids could exist, stating that humans spent a period of time evolving in a wet environment. If this were true, there could have also been an evolutionary branch of primates that stayed in the aquatic environment and eventually evolved into mermaids. The Animal Planet series also referenced an incident that happened in 1997 when NOAA discovered something called the "Bloop." This was a loud sound coming from the depths of the oceans that experts concluded was likely made by some type of animal unlike any whale, dolphin or other aquatic animal on record. All of these facts support the idea that mermaids could exist.

Although the TV series draws on some scientifically sound information, much of the content is fictional. Even the scientists on the show are actors portraing NOAA officials. According to NOAA, since scientists have started exploring the depths of the oceans, they have not found any concrete evidence to support the existence of mermaids.

Is it possible that mermaids exist? Yes. Is it probable? No.

Many animals have more than one stomach and humans only have one. Why is this?

Fri, 26 Apr 2013 00:00:00 -0400

The animals that you are referring to are called ruminants. They don't actually have more than one stomach, but have one stomach with four chambers. Cows, camels, llamas, deer, sheep and goats are examples of ruminants.

As you may have guessed, ruminants are animals that eat only plants, or herbivores. Plants contain cellulose, which is difficult to digest. In fact, many animals (humans included) cannot digest cellulose. Creatures that are dependent on a plant-based diet therefore need special adaptations to be able to digest this material. The four-chambered stomach is one such adaptation.

The ruminant stomach is composed of the rumen, reticulum, omasum and abomasum. When food is first swallowed, it enters the rumen. The rumen contains microorganisms, which produce cellulase, an enzyme no mammal is able to produce by itself. Cellulase breaks cellulose down into fatty acids, which are absorbed in the stomach and used for energy. This process is most efficient when food is broken down very well, as by chewing. Chewing food more than once then sounds like a good idea. In fact, ruminants regurgitate their food and chew it again. We call this chewing cud, or ruminating. Cud comes from food stored in the rumen and reticulum. Once food is chewed thoroughly it passes into the omasum, where water and minerals are absorbed, and finally into the abomasum, which is the equivalent of our stomach.

Several years ago, I attended an open house at the Cornell veterinary school. There I met a very special cow with a hole in her side. The hole, called a fistula - is created by a veterinarian. It is a three-inch diameter opening into the rumen and can be closed with a plug. Sometimes cows do not have enough microorganisms in their rumens and become very ill because they cannot properly digest their food. If this happens, vets can replace the microorganisms in the sick cow's stomach with some from the fistulated cow. Apparently the cow does not even notice the fistula, and provides a very important service to cows that could otherwise die.

Why does your tongue stick to a metal pole in the winter?

Mon, 25 Mar 2013 00:00:00 -0400

The saliva that coats your tongue is mostly water. When two objects at different temperatures touch, the warmer object gets colder and the colder object gets warmer until they are the same temperature. If the temperature of a metal pole is far enough below the freezing point of water, (32 degrees Fahrenheit) the saliva on your tongue will freeze as will the water in the cells that coat the surface of your tongue. The water on your tongue's surface and the water inside the cells on your tongue will form a big ice crystal and this is why your tongue will stick to the pole.

The cell membranes that surround each cell on your tongue will have ice on both sides that form a single crystal. They don't have much choice but to go in the direction that the ice is pulled. A crystal is a regular arrangement of molecules that forms when something is cold enough to be a solid.

If you find your tongue stuck to an icy pole, put your bare hands on the pole next to your tongue and wait for the heat from your body to warm the pole and hopefully melt the ice. If you just pull your tongue away from the pole, a piece of the surface of your tongue will likely stay stuck. (Ouch). If your tongue does remain in one piece, you will still feel a burn from the frostbite. If you lose a piece of tongue, don't worry, it will soon grow back.

If you have seen movie "Christmas Story," where the boys tried this on the playground, or the movie "Ice Age" where the squirrel-like animal has the same problem, you can learn from their mistakes. We all make mistakes. This one is easy to avoid.

Would getting too much calcium be a bad thing for your body?

Tue, 19 Mar 2013 00:00:00 -0400

Bryan, this is a complex question. The simple answer is that most likely you can’t get too much calcium if you are eating it from natural sources. The problem is that most Americans do not get enough calcium and that has many negative side effects.

Let’s take a look at what calcium does for your body in order to understand this. Calcium is needed to help the body maintain strong bones. It is also vital for communication between the brain and body parts as well as muscle movement. Calcium also aids in several other functions of the body; including the movement of blood vessels, hormones and enzymes.

Some of the best sources of calcium include dairy products like milk, yogurt, and cheese. Also, green vegetables like kale and broccoli have high amounts of calcium. Fortified cereals and canned fish with bones like sardines are also good sources.

Over time, not having enough calcium can lead to weak bones which ultimately results in osteoporosis and injury, like breaks and fractures. Certain groups in the population are more at risk for not getting enough calcium like adolescent girls, postmenopausal women, vegans, and people who are lactose intolerant. Additionally, age affects the rate at which calcium is absorbed; it decreases overtime so people over the age of seventy need more calcium. Lastly, vitamin D affects the rate at which calcium is absorbed; vitamin D is found in foods and from sunlight. In our area of the country many people have low levels of vitamin D, especially in the winter which makes us more at risk for not getting enough calcium.

If calcium is over-consumed naturally from your food the most common side effect is constipation. If too much calcium is taken in from supplements, mainly calcium bicarbonate, which is found in most supplements and is highly absorbable, the body will absorb more than it needs. Recent research has indicated that calcium supplements can lead to an increased risk of heart attacks, kidney stones, and overtime calcium buildup in organs, which could eventually lead to organ failure. The negative side effects happen when it is from an unnatural source rather than eating too much in your food.

What are stars made of?

Tue, 05 Mar 2013 00:00:00 -0500

I believe that everyone, at some point in their life, may ask themselves this same question.

The basic units of matter, that which we call elements, comprise everything we see around us. In the wake of the Big Bang, tiny particles were bound together to form the two simplest elements on the periodic table, hydrogen and helium. The first stars after the birth of the universe 13.7 billion years ago were formed from gas clouds containing these elements, collecting and condensing under their own gravity.

Stars are enormous reactors powered by a process called nuclear fusion – which occurs within their core. Under intense heat and pressure, small atoms are cooked into larger atoms. The result of this process, the forming of heavier elements from lighter elements, is the release of a massive amount of energy. It is the release of this energy that sustains the star, opposing the strong inward force of gravity.

We experience the products of nuclear fusion within our own star every day, in the form of heat and light. Generally speaking, a small star will only convert hydrogen into helium during its lifespan. A medium-sized star, such as the Earth’s Sun, will then convert helium into carbon and oxygen once its supply of hydrogen has been depleted. And, a massive star will continue to produce heavier elements late in life. The mass of our Sun is approximately 71% hydrogen, 27% helium. The remaining materials are heavier elements that were created in stars that existed long ago.

When a star’s supply of fuel has been depleted they collapse and then explode, scattering their contents far and wide. These clouds of elements eventually collect and condense, forming the next generation of solar systems.

Let’s not let the beauty of this topic escape us. In life, and in death, stars have produced all of the naturally occurring elements in existence that are heavier than hydrogen. The atoms that make up everything we have ever touched and every person we have ever known are traceable to those little specks of light we see in the nighttime sky.

So when you look skyward on a clear evening, don’t let the vastness make you feel small; your atoms have a direct connection to the stars!

To quote the famous astrophysicist Dr. Neil deGrasse Tyson, "We are part of this universe, we are in this universe, but perhaps more important than both of those facts, is that the universe is within us."

Why is there no oxygen on the moon?

Tue, 26 Feb 2013 00:00:00 -0500

First of all, I assume that what you meant by oxygen on the moon is oxygen in gaseous form above the ground. Let us first try to answer the question "why there is oxygen on the Earth?"

If you throw an object straight up, it will rise until the acceleration stops it, momentarily, due to gravity, then return to the Earth. The acceleration is a measure of how fast an object gains speed. Notice that the object slows down on the way up as the direction of the motion and the constant acceleration are opposite to each other. On its way down, the object speeds up. Can you throw an object straight up so that it never returns to the Earth? The answer is yes. If you throw the object with enough initial upward speed, it will leave the Earth. The minimum speed you need to acheive this condition is called "escape velocity" (velocity needed to escape gravity). The escape velocity depends on gravity. Gravity or the gravitational force is a force of attraction that exists between any two masses. In other words, Earth's escape velocity depends on the mass and the radious of the moon. Since the moon is much smaller than the Earth, the moon's escape velocity is smaller than that of the Earth.

How does this have anything to do with oxygen in the atmosphere? Gases are made up of individual atoms or molecules that are freely moving in random directions with wide variety of speeds. The measure of the speed of oxygen molecules is given by so called "Root-Mean-Square (RMS) speed." This speed depends on the mass and the temperature of the molecule. On the Earth's surface, the RMS speed of oxygen molecules is smaller than the Earth's escape velocity, so oxygen molecules do not escape the Earth. On the other hand, the RMS speed of oxygen molecules is larger than the moon's escape velocity. Therefore, if oxygen molecules are on the moon's surface, they will leave the moon. Here are the numbers: the RMS speed of oxygen molecules at zero Celsius temperature is about 4.6 km/s. The escape velocities of the Earth and moon on its surfaces are about 11km/s and 2.4 km/s respectively. Notice that the moon's escape velocity is smaller than the RMS speed of oxygen.

In conclusion, the moon's low gravity prevents it from keeping hold of the oxygen molecules on the atmosphere above the surface.

Why is ice slippery?

Tue, 19 Feb 2013 00:00:00 -0500

When two objects rub against each other, the molecules at the surfaces interact. The nature of the interaction will determine how easily the two surfaces can slip by each other. The amount of slipperiness depends on the attraction between the molecules, and how they are arranged. You have to push to get any object to move across any surface. We call the force that it takes to get one surface moving over another the force of friction.

If the surfaces are very smooth, you won't have to push very hard to get them moving. If at least one of the surfaces is rough, like sandpaper, it will take much more effort. Overcoming the force of friction also produces heat. You can feel this if you rub your hands together quickly over and over again. I often do this to warm my hands during the winter.

Ice is made of water molecules, which are very small as molecules go. They are the smallest molecules that can form a solid at temperatures we find on Earth. This makes for a very smooth, and slippery, surfaces when water freezes to make ice. If you wear skates, the friction from the skate will cause enough heat to melt the surface of the ice, making it even more slippery. This reduces the force of friction you need to overcome to get things moving.

Why and how do people laugh and cry?

Mon, 11 Feb 2013 00:00:00 -0500

At the turn of the fifth century B.C.E., the ancient Greeks, as part of their annual Dionysian festivals, created the first tragic and comedic theatrical productions for the enjoyment of the Athenian citizenry. In these plays, the Greek actors portrayed two of the deepest themes of human life experience – or human drama – by donning the now-famous laughing and crying masks which have been emblematic of the theater ever since. But what are human laughter and tears? What can science tell us about them?

How do we laugh? Laughter is similar to coughing, hiccupping and the act of speaking, since all the sounds produced by these events are related to the manner in which air flows through the larynx. But they have differing functions, of course: a cough is an involuntary act that may, for example, dislodge an obstruction in our airway; a hiccup, also an involuntary act, may serve to allow pockets of trapped air within the stomach to escape; and the voluntary act of speech involves the manipulation of air flow through our vocal chords to create variations in the pitch of the released sound, thereby allowing us to communicate through language. Our speech, of course, depends on the sounds we produce – but the meaning of what we communicate requires more than animal noises and sounds!

The outward phenomenon of tearing, on the other hand, results when stimulation of the central nervous system sends neural signals through the cranial nerve to one of our tear glands that, once stimulated, results in the emission of salty water into our eyes. Some tears – called basal tears – seem to simply function to keep our eyes moist. Other tears are generated to wash away dust or other small irritants that get into our eyes – the eye’s “cough,” as it were. And some tears – psychological or emotional tears – are associated with our inward emotion of sadness.