What was the Challenger disaster?

Seven astronauts were aboard Challenger flight STS-51L when it exploded during liftoff on January 28, 1986. Christa McAuliffe was a Concord, New Hampshire, high school social studies teacher. She and the other six crew members were killed when a solid-fuel booster rocket leak led to a massive fuel tank explosion during liftoff from its launch pad.

NASA’s next flight was Discovery, which was launched on September 28, 1988. After the Challenger disaster, NASA’s three remaining shuttles— Atlantis, Discovery, and Columbia—were rebuilt, each with more than 250 modifications improving safety and performance.

Interesting facts about Eye

1.    We should never put anything in or near our eyes, unless we have a reason to use eye drops. We would only do that if our doctor or parent told us to use them.
2.    If the lens in our eye doesn’t work quite right, we can get glasses to help us see. Glasses have lenses in them that work with our eye’s own lens to help us see better.
3.    Just behind the pupil is a lens. It is round and flat. It is thicker toward the middle.
4.    Over the front of our eye is a clear covering called the “conjunctiva.”
5.    Blinking helps to wash tears over our eyeballs. That keeps them clean and moist. Also, if something is about to hit our eye, we will blink automatically.
6.    Some people start to sneeze if they are exposed to sunlight or have a light shined into their eye.
7.    The highest recorded speed of a sneeze is 165 km per hour.
8.    Our eyes have many parts. The black part on the front of our eye is called the “pupil.” It is really a little hole that opens into the back part of our eyes.
9.    Our body has some natural protection for our eyes. Our eyelashes help to keep dirt out of our eyes. Our eyebrows are made to keep sweat from running into our eyes.
10.    The most common injury caused by cosmetics is to the eye by a mascara wand.
11.    It is impossible to sneeze with your eyes open.
12.    Around the pupil is a colored muscle called the “iris.” Our eyes may be BLUE, BROWN, GREEN, GRAY OR BLACK, because that is the color of the iris.
13.    Our eyes are very important to us, and we must protect them. We don’t want dirt, sand, splinters or even fingers to get in our eyes.
14.    The reason why your nose gets runny when you are crying is because the tears from the eyes drain into the nose.
15.    The space between your eyebrows is called the Glabella.

16.    The white part of our eye is called the “sclera.” At the front, the sclera becomes clear and is called the “cornea.”
17.    We don’t want our eyes to get scratched or poked. That could damage our sight!
18.    Babies’ eyes do not produce tears until the baby is approximately six to eight weeks old.
19.    Inside our eye, at the back, is a part called the “retina.” On the retina are cells called “rods” and “cones.” These rods and cones help us to see colors and light.
20.    Your eyes blinks over 10,000,000 times a year!
21.    The study of the iris of the eye is called iridology.
22.    The shark cornea has been used in eye surgery, since its cornea is similar to a human cornea.
23.    The number one cause of blindness in adults in the United States is diabetes.
24.    The eyeball of a human weighs approximately 28 grams.
25.    The eye of a human can distinguish 500 shades of the gray.
26.    The cornea is the only living tissue in the human body that does not contain any blood vessels.
27.    The conjunctiva is a membrane that covers the human eye.
28.    Sailors once thought that wearing a gold earring would improve their eyesight.
29.    Research has indicated that a tie that is on too tight cam increase the risk of glaucoma in men.
30.    People generally read 25% slower from a computer screen compared to paper.
31.    Men are able to read fine print better than women can.
32.    In the United States, approximately 25,000 eye injuries occur that result in the person becoming totally blind.
33.    All babies are colour blind when they are born.
34.    A human eyeball weighs an ounce.

Is it true that parts of Earth are always covered in ice?

About one-tenth of Earth’s surface is always under the cover of ice. And almost 90 percent of that ice is found in the continent of Antarctica. The remaining 10 percent is found on the mountains in the form of glaciers.

The ice sheet that covers Antarctica is almost one-and-a-half times the size of the United States.

What is a tsunami?

The Japanese word tsunami (pronounced soo-NAH-mee) means “harbor wave.” It is a huge volume of moving seawater—kind of like a giant wave—that can travel for thousands of miles across the sea and then approach the shoreline with the strength to destroy buildings, trees, wildlife, and people. Tsunamis can be triggered by an undersea earthquake, landslide, or volcanic eruption. The most frequent tsunami-maker is an undersea earthquake, which buckles the seafloor and displaces large volumes of seawater, creating a tsunami. This unique ocean event is not related to tides, although it is sometimes mistakenly called a tidal wave.

Posted on Categories Science

How old is Earth?

Scientists estimate that Earth—born out of a swirling cloud of gas and dust—is about 4.6 billion years old. They have reached this conclusion by studying Moon rocks and meteorites (rocks that have fallen from space to Earth) that they believe were formed at the same time as our planet.

How does a cellular phone work?

Cellular, or cell, phones first became available to consumers in the early 1980s, but the technology that made them small and truly portable evolved gradually over the next 10 years or so. By the beginning of the twenty-first century, millions and millions of people in countries all over the world were using cell phones on a daily basis. And it isn’t just adults who enjoy the benefits of completely mobile phone capabilities: in the United States alone, more than 20 percent of teenagers have a cell phone. That translates to at least one in five American teens. The cellular system divides each city into many small cells (a large city can have hundreds). Each cell has its own tower (which contains an antenna as well as transmitters and receivers that send and receive signals). Each tower can handle numerous callers at a given time, and their small size and weaker signal (compared to the radio antennae) means that their signals don’t interfere with those of nearby towers. When you call someone using a cellular phone, your phone is sending and receiving signals via radio waves, invisible bands of energy that work like light rays. In other words, your cell phone is a fancy, high-tech radio. After you dial a friend’s number, your phone must find the closest tower by searching for the strongest signal. Once that signal is located, your phone transmits certain information—like your cell phone number and serial number—that help your service provider make sure you are one of their customers.

Then the mobile telephone switching office (MTSO) finds an available channel where your conversation can take place. The MTSO then completes the connection (all of this happening in a few short seconds) and you are chatting with your friend, without wires or cords to hold you down. If you are sitting in the back seat of the car while talking, and your mom is driving you from one end of town to the other, your call will be switched automatically from one cell tower to the next without any pause in your conversation.

Which planet could melt metal?

Most people think that Mercury is the hottest planet because it is nearest to the Sun. However, Venus, the second nearest planet, is the hottest because it has an atmosphere. Its atmosphere is primarily composed of carbon dioxide, which acts like a greenhouse.

The solar heat enters Venus’s atmosphere, but it cannot leave, heating the planet’s surface to about 900 degrees Fahrenheit (482 degrees Celsius). This temperature is hot enough to melt several metals, including lead, tin, and zinc.

Is it true that at one time there was no oxygen?

Oxygen is necessary for all humans, animals, and plant life to survive. When Earth was first formed, its atmosphere had no oxygen—the colorless, odorless and tasteless gas that makes up about 20 percent of the air we breathe. It had only a deadly combination of hydrogen, methane, ammonia, and hydrogen cyanide.

The hydrogen escaped into space and ultraviolet radiation from the Sun broke down the mixture, leaving only nitrogen and carbon dioxide. Only when life began and photosynthesis (the conversion of light energy into chemical energy by living organisms) occurred did oxygen first appear—about 3.4 billion years ago.

What is the International Date Line?

Located at 0 degrees longitude, the prime meridian passes through Greenwich, England. Halfway around the world in the middle of the Pacific Ocean (180 degrees from Greenwich) is the International Date Line (IDL), where the date changes across the boundary of the time zone.

The entire world is on the same date only at the instant when it is noon in Greenwich, England, and midnight at the IDL. At all other times, there are different dates on each side of the IDL.

Why is Earth mostly crater-free compared to the pockmarked Moon?

Earth is more active, in terms of both geology and weather, which makes it hard for craters to remain. Even those craters scientists can see on the surface—which may be millions of years old—have been overgrown by vegetation, weathered by wind and rain, and changed by earthquakes and landslides. The Moon, meanwhile, is geologically quiet and has almost no weather, so its hundreds of thousands of craters are easy to see.

The craters are the result of both meteorites and volcanic activity. Interestingly, some of the oldest Earth rocks might be awaiting discovery on the Moon, having been blasted there billions of years ago by asteroid impacts that shook both worlds.