Each month one of our favorite scientists, internationally known astronomer Steve O'Meara of Volcano, Hawaii, fields your questions about . . . well, about whatever! Here's a list of questions / answers (in no particular order) from past months. If they trigger any questions in you, send those thoughts pressing on your mind to Odyssey's Ask a Scientist.
QUESTION:
Why do we have to pick up our dog’s poop? Won’t it naturally go away? How long does this take? What harmful effects will a neighborhood have if people were not made to pick up their dog’s poop?
REPLY:
One prevalent reason people ask you to pick up your dog’s poop is because it usually falls on public or private property, and, though the poop will biodegrade naturally, it is a mess to clean off one’s shoes. This is especially aggravating if the person who stepped in the dog poop in his or her yard does not own a dog! The problem is magnified in more populated areas.You also you wouldn’t want children playing, say, in a playground, where dogs are allowed to continually deposit their goods. It’s just unsanitary. Dog poop, in fact, does generate disease-causing bacteria that can make people sick -- namely coliform bacteria such as E. coli, a bacterium that can cause disease.
Poop may contain tapeworms or roundworms, which can be transmitted to humans. Dogs also carry salmonella and giardia.
Dog poop left hanging around for days can lead to filthy flies. Polio, for instance, can be transmitted to a human by a fly who has landed on your food.
QUESTION:
We live where salt is used a lot on our streets to melt ice and snow. This salt is brought into our garage on the tires of the car etc., where it thaws and melts. Now it is starting to eat away and corrode our cement pad and the sides of the garage, making the concrete crumble. Is there a way to stop the effects the crumbling caused by the action of the salt?
REPLY:
While the best option would be for the county to stop using salt on the roads, there is a little something you can do to prevent salt from building up on your car and in your garage. The International Car Wash Association advises that you wash your car two to three times a month with soap and water and with a high-power spray. Doing so will help prevent your car from corroding over time. As for the concrete. The problem is again one of time and accumulation. If possible, have a spray hose ready by your garage and hose down the tires before you roll the car into the garage. Then, each morning, after you roll the car out, either hose down the garage or sweep and clean up up the salt residue with a broom.
QUESTION:
I live in Las Vegas and am interested in solar heating the swimming pool. However, black piping all over the roof is undesirable. Are there any passive ways to use the Sun? Would painting the bottom of the pool a dark color cause it to heat up more? Would black painted sheet metal hanging from floats capture the heat?Do you have any suggestions?
REPLY:
OK. The popular opinion is that black absorbs heat, and therefore, by painting the bottom of your pool black, you’ll heat up the water.
Hmmm. That’s a greatly debated question. Pool owners differ widely in their opinions. See: http://www.halfbakery.com/idea/Black-Bottom_20Pool
You might want to join the forum.
Unfortunately, the question of whether a black bottomed pool will heat up the water has much to do with the depth of the pool and how much Sun you receive each day. The problem with a black bottom pool as I see it is that sunlight has to filter through the water (so it gets colder at depth) before it reaches the bottom of the pool where...at first... the heat is absorbed! So you are at first drawing heat away from the water. After an excess of Sun, the bottom of the pool (given a shallow enough depth) will start to reradiate heat energy, which then has to be dispersed throughout the water to make it warm.
The contrary argument is that white (or a light color) bottomed pool reflects sunlight, which helps redistribute the heat energy into the water.
While I'm certain that an overload of daily sunlight would help warm a pool whose bottom is painted black, I do not know what the aesthetic benefit would be? One popular way to heat a pool is to simply use a heavy-duty polyethylene cover during the days when it is not in use, as well as at night. The cover helps to capture sunlight and retain heat. Some pool covers are cleverly designed with bubbles or mylar to enhance heat retention.
You may even consider looking into a *Turbo Liquid Solar Blanket,* which is advertised as follows:
"This intelligent fish automatically dispenses liquid solar blanket into the pool, cutting heating costs and keeping the pool warmer. Each Turbo features a high-tech microprocessor that pumps out precise amounts of liquid every hour for up to 60 days, based on pool size. This invisible liquid rises to the pool's surface, inhibiting the heat evaporation that can cool the pool. Works 24 hours a day, pumping solar liquid more effectively, over a longer period of time than the original solar fish. Up to 60% as effective as a conventional solar blanket, completely harmless to skin, pool surfaces, and water chemistry. One fish covers up to 800 sq. ft. of surface. Two fish last up to 4 months."
Here's the web site:
http://www.aqua-pool-warehouse.com/Catalogs/catSolarCovers/bv_liquidSolarFish.asp#fish
Now, here's how the pool at the 1996 Olympics Games in Atlanta, was kept warm:
"2,856 photovoltaic cells covering 40,000 square feet provided 340 kilowatts of electricity to power the lights in the swimming complex. The water in the swimming pool - one million gallons of it - was heated by a solar thermal heating system. Such systems work by aiming large, black metal solar collectors at the sun. Black and other dark colors absorb more sunlight than light colors. Solar energy makes the collectors very hot, much like the surface of a blacktop road on a bright, sunny day. Water pumped through the collectors is heated naturally and then can be pumped back into the pool. Temperature sensors automatically turn on pumps to use the solar-heated water when the pool becomes too cool. Solar thermal heaters for swimming pools typically reduce water heating costs by about 50 percent. Many big pools with solar heat also use natural gas heating as a backup for cloudy days when the sun isn't shining."
QUESTION:
Do you believe in dragons?
REPLY:
Well, of course I do! Does my reply shock you? . . . It shouldn't, because "There be dragons" here on Earth!
I'm talking about the Komodo Dragon on the island of Komodo and others in the Lesser Sunda Islands in Indonesia. The Komodo Dragon (Varanus komodoensis) is a type of monitor lizard. In fact, not only is it the largest of all the monitor lizards, but it is also the largest lizard in the world . . .period! Those living today have relatives dating back over 100 million years! They are carnivores and survive primarily on carrion. Like a crocodile, a Komodo Dragon can sprint for short distances, moving at speeds up to 10 miles an hour! The largest dragon on record measured about 11 feet in length. There are about 6,000 Komodo dragons known to be roaming the Earth. Alas -- Komodo Dragons don't have wings, so they can't fly.
QUESTION:
I have two questions:
1. How much lava (in km3) pours of of the Earth each year?
2. When were plate motions first measured?
REPLY:
Unfortunately, the answer to the first question is, "Unknown."
The problem is that each year an unknown number of volcanoes erupt, and each contributes a certain amount of lava (whether it be in the form of ash or molten rock) to the surface of the Earth over time. But that amount varies each year. The biggest unknown is what’s happening under the sea -- along volcanic rifts at the bottom of the ocean. Here is where most of the lava is pouring forth unseen! In fact about three quarters of all lava erupted on Earth takes place unseen beneath the ocean, mostly along the oceanic spreading centers, such as the Mid-Atlantic Ridge and the East Pacific Rise. About 2.4 cubic miles (10 cubic km) of new oceanic crust is added each year (not all of this magma is erupted by volcanoes). This is about 100 times the volume of lava erupted by Kilauea Volcano in Hawaii each year.
How much is that? Kilauea -- one of the world’s most monitored volcanoes -- has erupted about 0.13 cubic kilometers (170 million cubic yards) of lava yearly for more than 20 years.
QUESTION:
I’ve been trying to find some info on the net about people with exceptional eyesight. I saw an old Odyssey question where you mentioned 20/10 vision. I’m really interested to know if this is what you have? Also, I’ve heard that some birds of prey have magnified vision in the center of their visual field – do you think any people have this?
REPLY:
I used to have 20/10 vision, when I was young. My eyes have changed now that I'm a bit older. But one thing that hasn't changed is my ability at night to see very faint. Night vision is very different than day vision. We use different parts of our eyes. In the day, we rely on what's called cone cells, and they're at the center of vision. They give us our color perception and resolution. At night we use our rod cells, which are not so good at color but are incredible at perceiving faint light, especially along the periphery of the eye.
My eyesight at night is good because I have trained myself over the years to know how confident I should be about what I see. In fact, some people have said I am a "visual athlete." I think that's an appropriate portrayal.
As for what you say about magnified vision in the eyes of some birds of prey, well, that is very interesting. I am not aware of that aspect of their vision. But the ideas sounds right, especially for birds of prey that can see tiny critters from so high up.
QUESTION:
How do earth scientists use a high-speed camera. For instance lets say you wanted to study the movement of a glacier. How would you go about doing that?
REPLY:
Great question! And I certainly am qualified to answer that question since I and my Volcano Watch International team member Bob Benward have created high-speed movies of volcanoes erupting! For instance, In February 2003, Bob and I set up a 0.0003 lux CCD video camera to expand and support our visual coverage of the erupting Soufriere Hills volcano on Montserrat in the West Indies. The camera took frames every 8 seconds, which were relayed to a digital video data recorder; each frame was saved as a JPEG, which could be played back at 6 minutes per day for 12 days.
QUESTION:
How is an alligator affected by the depleting of the ozone layer? Does this affect the color of their skin and when it does, does it change color?
REPLY:
Alligators are a specialty of mine. While it's true that the International Union for the Conservation of Nature -- which has set up the Declining Amphibians Population Task Force -- are trying to find reasons for mysterious population decreases in not only amphibians but in reptile, like alligators, they have no definitive answers. They are investigating, in part, the thinning ozone layer as a possible cause, but this, I believe, is way off mark!
The most possible, and probable cause is pesticides from nearby farms and perhaps acid rain.
For instance, consider the fate of the alligators of Lake Apopka, which is a few miles from Disney World in Central Florida. Alligators were once plentiful there, but in recent years, their numbers have dropped significantly -- to 10 percent of their 1980 numbers. According to the National Federation of Wildlife, the plight of Lake Apopka's alligators is an extraordinary case of what some scientists say is a widespread problem. University of Florida scientists attribute the decline to an accident at the Tower Chemical Company facility next to the lake's waters in 1980. The company spilled the pesticide kelthane (which contains DDT) and sulfuric acid. The lake also receives pesticide runoff from nearby citrus farms.
The idea that alligators, which have been around much longer than man -- some 200 million years -- are being greatly and suddenly affected solely by a trace depletion of ozone borders on pseudoscience. We know relatively very little about the ozone layer today, let alone how dense or anemic it was millions of years ago. Obviously, alligators have remained relatively unchanged and unchallenged over the millions of years -- until humans arrived on the scene with guns and toxic chemicals. If you want to find a reason for declining alligator populations or deformities, I believe you need not look to the skies. The fault is here, in the water, near toxic waste dumps and runoffs.
QUESTION:
I need information on where I can find pink snow.
REPLY:
Pink snow can appear on high mountaintops that are usually or perpetually covered in snow. The cause of the reddish coloration is a bloom of algal cells -- each about 30 micrometers in diameter. The blooms can be most dramatic during late spring and summer. The concentrations of these cells is so profuse that a teaspoon of melted snow in these regions can contain more than a million snow algae cells. The more compact the snow, the more intense the reddish color. Each spherical cell is approximately 30 micrometers in diameter, about four times the diameter of a human red blood cell.
These pink snow patches baffled explorers and naturalists for thousands of years -- including the philosopher Aristotle! At least 60 different species of snow algae have been identified in the western United States. By the way, the scientific surname of this cold-loving algae is nivalis -- it's from a Latin word that refers to snow.
QUESTION:
I need to know if you know what major diseases immigrants are tested for before they enter the U.S. (besides TB).
REPLY:
First, you’re right, before 1924, every legal immigrant was examined for infectious diseases upon arrival in the US and tested for tuberculosis. According to Dr. Madeleine Cosman, "That was powerful incentive for each newcomer to make heroic efforts to appear healthy." Alas, today, she says, legal immigrants must demonstrate that they are free of communicable diseases and drug addiction to qualify for lawful permanent residency Green Cards. Of course, the larger problem are the diseases brought into this country by unchecked illegal aliens. She also writes that "if we catch and detain a sick Illegal Alien, who after examination by physicians in a detention center proves to have a serious disease, we keep him! Foolish compassion makes us fear that his home country has neither adequate medical resources nor modern wonder drugs. So we release sick Illegal Aliens to the American streets, to infect others if their diseases are contagious, or we place them in our Medicaid program where we pay for their expensive treatments." You can read more at http://www.rense.com/general64/ill.htm.
Meanwhile, some countries, like Great Britain, are lobbying for a bill that would require immigrants wanting to live in that country to undergo tests for HIV, tuberculosis and hepatitis B.
QUESTION:
What came first the chicken or the egg?
REPLY:
The following is from "Chicken Facts:"
"According to National Geographic, scientists have settled the old dispute over which came first -- the chicken or the egg. They say that reptiles were laying eggs thousands of years before chickens appeared, and the first chicken came from an egg laid by a bird that was not quite a chicken. That seems to answer the question. The egg came first. Source: *Knowledge in a Nutshell*"
QUESTION:
How was the moon formed?
REPLY:
Despite earlier thinking, the Moon did not pop out of Earth’s oceans. The leading theory today is that about 4.5 billion years ago a Mars-sized body slammed into primordial Earth. The resulting debris cloud, which was comprised of particles from both the Earth and the impacting body, was captured by Earth's gravity and accumulated to form the Moon.
QUESTION:
Can chickens fly?REPLY:
Can chickens fly. Well, yes they can . . . for short distances. Kathy Rogers, a wildlife rehabilitator at Samuell Farm, in Dallas, Texas, calls chickens “spurt flyers,” meaning they will flap up to a low tree or fence post to roost for the night or when they feel in danger.
The “law,” however is that the bigger the bird the bigger the belly, and the less likely a chicken is to fly. The reason we don’t see chickens “flying the coop” (so to say) is because we breed them to be BIG -- so they can lay eggs or are “meaty” for consumption.
But Rogers says that even the fittest of chickens would never fly for any distance.
You might enjoy going to this web site: Chicken Facts:
http://www.vfr.net/~tbruce/facts.html. There you will learn, among many other things: * Fact - The longest distance flown by any chicken is 301 1/2 feet. (That’s as the crow flies).QUESTION:
My question is about the bald eagle. I have been watching a familiar bald eagle (in a zoo) who is getting to be about 25 or so years old. His beak appears to be getting paler - no longer a bright yellow, but a pale buttery color. Is this a sign of age?
REPLY:
You are absolutely right. The beak . . . and eyes . . . of an immature eagle are dark. As the Bald Eagle matures -- around the ages of four to five -- the bird begins to get its white tail and head, and the eyes and beak begin to turn yellow. Just as you observed!
QUESTION:
I live in the Northeast. In the Autumn, after all of the leaves fall from the trees and it snows, why don’t people suffocate because there are no leaves around producing oxygen through photosynthesis?
REPLY:
I’m sure you've heard of “Think Globally, Act Locally!” Well, think globally.
In one year, an average tree inhales 26 pounds of carbon dioxide and exhales enough oxygen to keep a family of four breathing for a year. And yes, there are lots of trees in New England, and they do produce a lot of oxygen when they photosynthesize. But New England is such a small place on the global scale.
In fact, did you know that it’s the rain forests -- places that stay green all year round -- that generate about 40 percent of the world’s oxygen? Not only that, but trees are not the only source of oxygen. For instance, bacteria and a few other organisms are photosynthetic.
Oxygen is also stored in Earth’s waters and soil, as well as in animal tissue and more! All of these sources can replenish oxygen in our atmosphere by simply changing states.
On a global scale, about a trillion kilograms of oxygen are produced by photosynthesis per day. The vast majority of this process happens in our oceans mostly by bacterium or a blue-green alga! We humans, on the other hand, convert about the same amount of oxygen to carbon dioxide.
QUESTION:
Why are glaciers called rivers of ice?REPLY:
First, some rivers, as you may know, originate from snowcapped mountains. As the snow warms, it melts. Gravity then forces the water down the mountain. The water takes the course of least resistance and flows in a constant rush down slope, usually in steep-sided valleys. These are glacial source-fed rivers.Actually, glaciers do not need slopes to flow. Like dense molten lava, the front of the glacier advances by the continuing accumulation of new material at their point of origin. That pile up causes pressure on the layers of material below. In the case of ice, the pressure heats the ice and forcing the lower layers to slowly creep forward like a viscous fluid. Over time the glacier extends down the mountain, following the curving valleys like a river. So a glacier is, in a sense an enormous, slowly advancing frozen river.
QUESTION:
What are some myths and legends for Mount Pinatubo?
REPLY:
Mount Pinatubo is a great volcano on Luzon Island in the Philippines. The region’s aboriginal people, the Ayta’s, or Aeta’s, see Mount Pinatubo as the dwelling place of Apo Namalyari, the One who creates, the One who makes the whole of creation grow and live. Pinatubo is, to them, a sacred mountain where the dead Aetas go. Today it is still the home of their spiritual heritage and the homeland of the spirits of their ancestors.
QUESTION:
In the formation of color in a blue painted object illuminated with white light, how does the formation mechanism differ from that causing the blue in blue sky?
REPLY:
The quick response to what I believe you are asking is that painted blue object is a product of color absorption. All objects contain atoms which are capable of absorbing one or more frequencies of light and reflecting all others. The color we ultimately see depends on what colors are absorbed and which mixture of colors are reflected to our eyes...
As for the sky, it is blue because air molecules effectively scatter blue wavelengths of light.
QUESTION:
What is sonoluminesence?
REPLY:
Sonoluminescence, also called a mysterious "star in a jar" is, essentially, a microscopic bubble suspended in a jar of water by acoustic waves. The force of the oscillating waves stretch and compress the bubble some 30,0000 times per second, generating temperatures hotter than the Sun's surface. A faint flash of light (the luminescence) accompanies each cycle, which lasts only 30 trillionths of a second.
QUESTION:
What is a mummy?
REPLY:
Most people believe mummies are bodies wrapped in bandages that lie buried in tombs beneath the ancient sands of Egypt. And while this is true for many mummies found in Egypt, not all mummies are wrapped in bandages.
Cutting to the quick, a mummy is is the deceased body of a person (or an animal) whose skin and flesh have been preserved after death. The preservation can be intentional or accidental. Many of the mummies of Egypt, for instance, have been deliberately embalmed to preserve the body's soft tissue. Other mummified bodies have been accidentally preserved (without being wrapped in bandages or embalmed) by extreme hot, cold, or airless environments.
Have you ever heard of Ötzi the Ice Man? He was found in 19991, high in a snowfield in the Alps. His body is estimated to be about 5,200 years old. His skin tissue was kept virtually intact by the extreme cold at altitude. Then there's Tollund Man -- a 2,100-year-old body found in a peat bog in Denmark. Some bodies have been found in cold, dry caves, whose conditions helped to slow the rate of tissue deterioration.
QUESTION:
What are some of the common characteristics we share with a beetle?
REPLY:
Well, off the top of my head, I'd have to say that the most important thing that they have with humans, and maybe the only thing, is that they use their five senses to survive!
QUESTION:
Who created the periodic table?
REPLY:
The first periodic table of elements was created by Dimitri Ivanovich Mendeleev (1834 -1907). It was his method of classifying the basic building blocks of matter. I say it was the “original” periodic table because in Mendeleev's day, only 60 of the more than 110 elements were known. In a chemistry book Menedleev published in 1905, he writes the following about the reason he created the table:
"I began to look about and write down the elements with their atomic weights and typical properties, analogous elements and like atomic weights on separate cards, and this soon convinced me that the properties of elements are in periodic dependence upon their atomic weights."
QUESTION:
Which scientist / inventor created "for every action there is an opposite and equal reaction"?
REPLY:
That's Sir Isaac Newton's Third Law of Motion: For every action there is an opposite and equal reaction. It explains, for example, why rockets fly! When hot gases push out from the bottom of the rocket, the rocket is hurtled skyward with a force equal and opposite to the force of the gas that's pushing earthward.
QUESTION:
How far away is the Moon?
REPLY:
That's a good question -- one that is not as simple as it sounds. The Moon's distance varies as it orbits the Earth. This is due to the fact that the Moon's orbit is not circular but elliptical. When the Moon is closest to the Earth it is at a point called perigee. When it is farthest from Earth it is called at a point called apogee. When the Moon reaches perigee, its distance is 363,300 kilometers (225,755 miles). When the Moon is at apogee it is 405,500 km (251,978 miles) distant. The Moon's average or mean distance from Earth is 384,400 km (238,866 miles).
QUESTION:
What are Saturn's rings made of?
REPLY:
Great question! About a century and a half ago, some Harvard astronomers believed the rings were fluid, but today we know they are comprised of tiny pieces of rock and ice that form a complex system of rings around the planet.
Saturn has three major rings -- Rings A, B, and C (from the outside in, respectively) and several minor ones. The Cassini spacecraft determined that the particles in the major rings range from a few centimeters in diameter to 10 meters in diameter, though there is no typical size. Besides, the particles are most likely colliding with one another. The A and B rings are very slightly reddish, which may be evidence of some organic materials mixed in as well.
In essence, the rings are like a shattered comet. The Cassini spacecraft also recently discovered large amounts of dark material, or “dirt,” within the gap (Called the Cassini Division) between Saturn's A and B rings. This dark matter appears remarkably similar to that found on one of Saturn's moons, Phoebe. NASA scientists say that these dark particles refuel the theory that Saturn's rings might be the remnants of an icy moon that has been ripped apart by tidal forces.
By the way, Cassini also detected large quantities of oxygen at the edge of the rings, which may have resulted from a collision of an icy body that occurred as recently as several months ago.
QUESTION:
What is dog feces and what causes the smelly gas?
REPLY:
According to Medfriendly.com:
Dog feces are mostly made of water (about 75%). The rest is made of dead bacteria that help to digest the food, living bacteria, protein, undigested food residue (known as fiber), waste material from food, cellular linings, fats, salts, and substances released from the intestines (such as mucus) and the liver. Although feces are made up of about 75% water, this number varies from animal to animal, depending on how long the feces stay in the intestine. Since the intestines absorb water from the feces, diarrhea (poop that passes quickly through the intestines) will contain more water and retained feces (which stay in the intestines for a longer amount of time) will contain less.
The bacteria inside of the feces is what makes them smell so bad. (That's the gas). Specifically, the bacteria produce various compounds and gases that lead to the infamous smell of feces. It's hard to say what gases are being released because that depends on what you feed your dog. Generally speaking, feces will smell worse if your animal consumes food or liquids with many artificial flavors or chemicals in them. The bad smell of feces will usually be reduced by eating more natural foods that do not contain any artificial flavors or chemicals. Remember, however, that these are general guidelines. The only way to know for sure is to monitor the smell of feces depending on the types of foods in the diet and to see if the smell changes when certain foods are removed or added.
QUESTION:
Why do we not see galaxies and stars in the background when NASA shows an astronaut outside the Space Shuttle?
REPLY:
Great question. The answer is quite simple. It has to do with the limitations of a camera lens and the great dynamic range in contrast between the extremely bright astronaut or spacecraft and the extreme relative dimness of starlight. The camera takes very short exposures, which are not long enough to capture the star-filled sky. For instance, if you own a camera, take it outside, hold it up to the sky and take a 1/125-second exposure. When you get the film developed, you'll see only darkness -- not infinite starlight. As for galaxies -- there are only a couple bright enough to be seen with the naked eye. All the images you see from space -- like those taken with the HST-- that are filled with starlight and galaxies is a product of a large-aperture telescope, sensitive electronic cameras, and precise guiding via satellite links. All these images are taken looking away from any bright objects.
QUESTION:
What are odds that a black hole will suck up the Earth? And what will happen if a black hole really sucks up the Earth?
REPLY:
First, the odds that the Earth will be sucked into a black hole are essentially zero. Black holes are formed by stars much more massive than our Sun. When these very massive stars die, their interiors collapse into an infinite point, beyond which, we can only theorize what will happen.
When our Sun dies, it will become what is known as a planetary nebula. The outer shell of gas will expand about 10 miles per second away from a collapsed core called a white dwarf -- a star with the size of the Earth but so compressed that a tablespoonful of its matter would weigh 15 tons! The outer shell will swell to encompass our Solar System. After 5 billion years, that white dwarf will turn into a black and lifeless cinder. But don't worry. By then, us humans will have developed ways to travel to other suns and inhabit other planets. (I'll buy you a cup of coffee if we don't.)
If a black hole were to "suck up" the Earth, well, the Earth may emerge in another dimension, or in another region of curved space -- that's after it exists the hypothetical "white hole." Take a sheet of paper and curl it into a "C." Imagine a black hole occurs on the top of the C. Now imagine a tube connecting it to the bottom of the C -- that's where you could find your white hole.
QUESTION:
Why does a boat float higher in salt water? Please explain in first grade terminology.
REPLY:
Floating is a common term for what is known as "Buoyancy." So, to keep it simple I'm going to call buoyancy . . . floating. Rather than thinking of a boat in water as a heavy thing that can sink. Think of the water below pushing up on the boat. The reason something floats is because the water beneath it is pushing up on it. The larger the base of the boat the more water can push up on it and the better it can float. So think of floating as an upward force. Now, salt water is denser (heavier) than fresh water. So think of salt water as being stronger than fresh water, in that it can push up on an object harder or with more force. Think of a 90-pound person trying to bench press, say 50 pounds, as opposed to someone who is 150 pounds.
QUESTION:
How do I become an astronaut?
REPLY:
This answer comes straight from the horse's mouth...NASA! And it's a long answer.
****We will assume you mean a NASA astronaut, since it's probably impossible for a non-Russian to get into the cosmonaut corps (paying passengers are not professional cosmonauts), and the other nations have so few astronauts (and fly even fewer) that you're better off hoping to win a lottery. Becoming a shuttle pilot requires lots of fast-jet experience, which means a military flying career; forget that unless you want to do it anyway. So you want to become a shuttle "mission specialist