Category How does It works, How things work, How is it done, Curiosity

HOW DO COMMUNICATION SATELLITES WORK?

The layer of the Earth’s atmosphere called the ionosphere can reflect some radio waves back to Earth. This is used for sending messages over fairly short distances, but for messages to travel further across the Earth, the radio signals can be bounced off a satellite, orbiting almost 36,000km (22,000 miles) above the Earth’s surface. Several satellites, in different orbits, are required to give coverage over the whole globe, and different satellites are used to reflect signals for different media, such as telephone messages and television pictures.

A communications satellite is an artificial satellite that relays and amplifies radio telecommunications signals through a transponder. It basically creates a communication channel between a source transmitter and a receiver at different locations on earth. Communications satellites are used for television, telephone, radio, internet, and military applications. There are currently 2,134 communications satellites in the earth’s orbit and these comprise both private and government organizations. Several are in geostationary orbit 22,236 miles (35,785 km) above the equator, so that the satellite appears stationary at the same point in the sky. The orbital period of these satellites is the same as the rotation rate of the Earth, which in turn allows the satellite dish antennas of ground stations to be aimed permanently at that spot; they do not have to move along and track it. Since the high frequency radio waves used for telecommunications links travel by line of sight, they get obstructed by the curve of the earth. What these communications satellites do is they relay the signal around the curve of the earth thus making possible communication between widely removed geographical points. Communications satellites use a wide range of radio and microwave frequencies. To avoid signal interference, international organizations have regulations stating which frequency ranges (or bands) certain organizations are permitted to use. This allocation of bands reduces the chances of signal interference.

A group of satellites working together is called a satellite constellation. Two such constellations are supposed to offer satellite phone services (mainly to remote areas), are the Iridium and Global star systems. The Iridium system has 66 satellites. It is also possible today to provide discontinuous coverage using a low-earth-orbit satellite that can store data received while passing over one part of earth and transmitting it later while passing over another part. The CASCADE system being used by Canada’s CASSIOPE communications satellite is an apt example.

A satellite in orbit has to operate continuously over its entire life span. It needs internal power to be able to operate its electronic systems and communications payload. The main source of power is sunlight, which is harnessed by the satellite’s solar panels. A satellite also has batteries on board to provide power when the Sun is blocked by Earth. The batteries are recharged by the excess current generated by the solar panels when there is sunlight.

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HOW HAVE MODERN COMMUNICATIONS CHANGED OUR LIVES?

Modern communications have affected our lives in numerous ways. Being able to pass information down telephone wires or via satellites means that some people can work from anywhere in the world and still keep in constant touch with their offices. A surgeon in Arizona, via a satellite link, can assist a colleague in Beijing with a complicated operation. News can travel halfway around the world as quickly as it can reach the next town. Perhaps the biggest effect of communications has been to make us all feel that the world is a smaller place, and that we need to be concerned about its future and the futures of people thousands of miles away.

The Internet has turned our existence upside down. It has revolutionized communications, to the extent that it is now our preferred medium of everyday communication. In almost everything we do, we use the Internet. Ordering a pizza, buying a television, sharing a moment with friend, sending a picture over instant messaging. Before the Internet, if you wanted to keep up with the news, you had to walk down to the newsstand when it opened in the morning and buy a local edition reporting what had happened the previous day. But today a click or two is enough to read your local paper and any news source from anywhere in the world, updated up to the minute.

Technology has improved communication, especially in recent years. We’ll always have so much information readily available at our fingertips. Writing letters to relatives living hundreds of miles away is so old-school! Instead, you can talk to them through a video call or instant messaging. This change in communication has completely changed relationships all over the world.

Services like Facebook and Twitter have also become a big part of our everyday lives. These sites allow people to see a lot of information and photos at once and are enjoyable by design. When you upload a photo to the Internet, it doesn’t simply go away. It stays for a long time. This means you can use technology to store memories that are important to you, like family photos.

With modern technology, we can live much healthier lives. Those who have fitness trackers can see how active they are. Seeing that can encourage us to be even more active. Some fitness trackers like the Apple Watch even gamify health with competitions and points!

New technology can help create cures and medicines. Someone who is sick in modern times is much more likely to be cured than someone in past times. Modern technology can automate just about anything, from turning on a light to ordering a pizza. With automation, we can do so much more in such a small amount of time. For example, you can use your voice to start the coffee maker while you’re still getting dressed.

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HOW MUCH HAS THE SPEED OF COMMUNICATION INCREASED?

Only a few hundred years ago, the fastest way that a piece of news could travel was to be carried by a person on horseback. Messages sent overseas could only travel as fast as the fastest sailing ship and were at the mercy of the wind and weather. The development of steam locomotives and steamships made it possible for information to move around the world more quickly, but it still had to travel physically from one place to another, as a letter. The breakthrough came with the invention of the electric telegraph and messages in Morse code. The message was sent down a wire in bursts of electric current. Today, images of written documents, sound recordings or television pictures can be flashed around the globe in less than a second by means of satellites and radio communications.

It seems like advancements in technology and changes in communication always go hand in hand. When science was working to introduce new tools to let distant people contact each other, the landlines replaced telegraph and subsequently, cell phones replaced landlines. When the Internet arrived, it not only brought revolution in the sales industry but also opened new doors of personal communication. When science was looking for more convenient ways to send messages, e-mails replaced postal emails and social media replaced text messages. So it would not be wrong to say that technology has been shaping the communication industry for over a hundred years.

Previously, there were not much mediums of communication and today we are completely overwhelmed with the disparate mediums, thanks to the ever-changing technology! From Facebook to Instagram and skype to Whatsapp, we now have the limitless database of communication tools that have brought us closer to the entire world. All these communication mediums have also impacted our lives in different ways. For example, it’s true that Smartphones have brought us closer to our friends and relatives living in distant places, but at the same time, they have also made our society somewhat impersonal. Although they have helped increasing workplace engagement and productivity, they have also given rise to certain security and privacy issues.  While some of these issues are relatively minor, but some may have profound effects on the lives of users.

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HAVE HUMAN BODIES CHANGED THROUGH THE CENTURIES?

Over millions of years, evolution is changing the way humans look. Over a shorter period, improved nutrition and medical discoveries have meant that people in some parts of the world today are generally bigger and stronger than their ancestors. But we are also losing some abilities that no longer seem useful. The smallest toe, for example, can no longer be moved independently by most people. As recently as Roman times, some people may have been able to “prick up their ears”, moving them slightly towards sounds as some animals can.

Humans are getting taller; they’re also fatter than ever and live longer than at any time in history. And all of these changes have occurred in the past 100 years, scientists say. So is evolution via natural selection at play here? Not in the sense of actual genetic changes, as one century is not enough time for such changes to occur, according to researchers.

Most of the transformations that occur within such a short time period “are simply the developmental responses of organisms to changed conditions,” such as differences in nutrition, food distribution, health care and hygiene practices, said Stephen Stearns, a professor of ecology and evolutionary biology at Yale University.

But the origin of these changes may be much deeper and more complex than that, said Stearns, pointing to a study finding that British soldiers have shot up in height in the past century. ”Evolution has shaped the developmental program that can respond flexibly to changes in the environment,” Stearns said. “So when you look at that change the British army recruits went through over about a 100-year period, that was shaped by the evolutionary past.”

And though it may seem that natural selection does not affect humans the way it did thousands of years ago, such evolutionary mechanisms still play a role in shaping humans as a species, Stearns said.

“A big take-home point of all current studies of human is that culture, particularly in the form of medicine, but also in the form of urbanization and technological support, clean air and clean water, is changing selection pressures on humans,” Stearns told Live Science.

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WHAT IS THE DIFFERENCE BETWEEN VEINS AND ARTERIES?

Veins are blood vessels that carry blood to the heart, while arteries carry it from the heart. The heart acts as a pump, pushing blood to every part of the body. Adults have between five and six litres (between nine and ten pints) of blood. As well as containing red cells to carry oxygen to the body’s organs, blood also plays an important part in fighting infection. White blood cells attack and digest harmful bacteria, while platelets in the blood form clots so that wounds can heal and no further infection can enter the body.

Arteries and veins both carry blood around the body, and they each have three main layers of tissue (a ring of endothelial tissue at the centre of the blood vessel surrounded by a layer of muscle and elastic fibres, which is surrounded by a layer of connective tissue). However, there are several differences between them:

  1. Arteries carry blood from the heart to the rest of the body, whereas veins carry blood from the rest of the body back to the heart.
  2. Almost all arteries carry oxygenated blood and almost all veins carry deoxygenated blood. The only exceptions are the pulmonary artery, which carries deoxygenated blood from the heart to the lungs, and the pulmonary vein, which carries oxygenated blood from the lungs to the heart.
  3. Arteries have a thick elastic muscle layer, whereas the muscle layer for veins is much thinner. This is because the heart pumps blood into the arteries at high pressures, so the walls of the arteries must be able to cope with the changes in pressure during a heartbeat. Veins carry blood at much lower pressures so do not need such a thick wall.
  4. Arteries have a much narrower lumen (the hole at the centre that the blood flows through) than veins. This helps keep higher blood pressures in the arteries, which is needed to keep blood flowing quickly to body tissues.
  5. Veins have valves and arteries do not. In arteries, blood flows in the right direction because of the heart pumping it forwards at high pressures. The lower blood pressure in veins means that valves are needed to stop blood flowing backwards (for example, in veins in the legs, blood needs to flow upwards against the pull of gravity).

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HOW MUCH FOOD DO WE NEED?

Food is the fuel that our bodies need for movement. But we also need some fuel simply to maintain all the parts of our bodies. Individual cells are being renewed all the time. And even if we do not move the outside of our bodies at all, there are many parts inside that are constantly in motion. How much food we need depends on our size, age, gender and level of activity.

Nutrition is how food affects the health of the body. Food is essential—it provides vital nutrients for survival, and helps the body function and stay healthy. Food is comprised of macronutrients including protein, carbohydrate and fat that not only offer calories to fuel the body and give it energy but play specific roles in maintaining health. Food also supplies micronutrients (vitamins and minerals) and phytochemicals that don’t provide calories but serve a variety of critical functions to ensure the body operates optimally.

Protein: Found in beef, pork, chicken, game and wild meats, fish and seafood, eggs, soybeans and other legumes included in traditional Central America cuisine, protein provides the body with amino acids. Amino acids are the building blocks of proteins which are needed for growth, development, and repair and maintenance of body tissues. Protein provides structure to muscle and bone, repairs tissues when damaged and helps immune cells fight inflammation and infection.

Carbohydrates: The main role of a carbohydrate is to provide energy and fuel the body the same way gasoline fuels a car. Foods such as corn, chayote, beans, plantains, rice, tortilla, potatoes and other root vegetables such as yucca, bread and fruit deliver sugars or starches that provide carbohydrates for energy.

Energy allows the body to do daily activities as simple as walking and talking and as complex as running and moving heavy objects. Fuel is needed for growth, which makes sufficient fuel especially important for growing children and pregnant women. Even at rest, the body needs calories to perform vital functions such as maintaining body temperature, keeping the heart beating and digesting food.

Fat: Dietary fat, which is found in oils, coconut, nuts, milk, cheese, meat, poultry and fish, provides structure to cells and cushions membranes to help prevent damage. Oils and fats are also essential for absorbing fat-soluble vitamins including vitamin A, a nutrient important for healthy eyes and lungs.

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