What is Tallying? - Tallying and Tally Marks

Can you imagine a time when people did not use numbers?
The first people on earth lived by hunting wild animals and collecting wild fruit and nuts.
They had no need to count.
Numbers did not matter to them.
But then, about 11,000 years ago, herdsmen began to keep flocks of sheep and goats.
They had to be able to count so that they would know if any of their animals were missing.
The first calculations were made by counting in ones—'1 and 1 and 1,' and soon.

This method of counting is called tallying. 

One way herdsmen used to tally was to put a stone on a pile for each animal.
Other ways were to tie knots in a length of rope, cut notches in sticks, or make scratches on a rock. Each stone, knot, notch, or scratch represented one sheep or goat.

Voyager 1 and Voyager 2 - Voyage of discovery - Space Probes Information

On August 20, 1977, Voyager 2 was launched into space.
Two weeks later, Voyager 1 set off. 

The two Voyagers were types of unmanned spacecraft called space probes.
Their mission was to travel to the more distant planets of the solar system and send information about them back to earth.

No spacecraft had ever traveled so far into space before.
Voyagers 1 and 2 each carried 11 instruments. 

These included remote-controlled computers, television cameras, ray detectors, infrared and ultraviolet sensors, and a magnetometer.

These instruments recorded and sent back information about our solar system.

Technology has developed quickly since the Voyager probes were launched. That equipment is now out of date. A modern, desktop computer is more powerful than the Voyager computers. Scientists have updated the probes' computer programs and made repairs from earth by remote control.
In 1980, three years after its launch, Voyager 1 reached Titan, Saturn's largest moon.

The probe sent back information to earth. It found chemicals like those on earth. But Titan is too cold for these chemicals to develop into living things as they have done on earth.

The journey of Voyager 2

1. On August 20, 1977, Voyager 2 was launched from earth at a speed of just over 24,800 miles (40,000 kilometers) per hour. The idea was to use the gravity, or pull, of each planet it passed to catapult the space probe faster and faster through space, from one planet to the next.

2. On July 9 1979, Voyager 2 came closest to Jupiter and discovered it has three more moons. The planet’s gravitational pull increased the speed of Voyager 2 to around 30.700 miles (48.000 kilometers) per hour.

3. It was August 25, 1981, and Voyager 2 passed Saturn at a speed of 33,700 miles (54,400 kilometers) per hour. Then we learned that Saturn has nine more moons that it was known to have.

4. At Uranus, on January 24, 1986, Voyager 2 discovered 10 new moons. Its speed was now 36,700 miles (59,200 kilometers) per hour.

5. Mission completed! On August 25, 1989, Voyager 2 passed within 3,000 miles (4,800 kilometers) of Neptune's cloud top.

We learned that this planet is a hostile world.

No living thing could survive here.

Twelve years after it left Earth, Voyager 2 reached Neptune. It had traveled nearly 4.4 billion miles (7.1 billion kilometers) and arrived four minutes early!

Voyager 2 carries its own message—a record of voices and other sounds from earth— just in case there is life beyond our solar system.

Voyager 2 is expected to enter interstellar space within a few years of 2016. It is not headed toward any particular star, although in roughly 40,000 years it should pass 1.7 light-years (9.7 trillion miles) from the star Ross 248.

Voyager 2 is expected to keep transmitting weak radio messages until at least 2025, over 48 years after it was launched.

What is a Space Probe? - Information on Space Probes

Until now, human beings have traveled into space only as far as the moon, about 236,000 miles (380,000 kilometers) away.
But robot space crafts are sent very much farther.
These have visited the distant planets.
These robot space crafts are called space probes.

What is a Space Probe?

Space probes carry cameras and many kinds of instruments to study the planets they visit. They send information back to earth by radio.
Probes must be launched from the earth at a very great speed—more than 24,800 miles (40,000 kilometers) an hour.
Then they can escape from the earth's gravity.
Aiming the probe is very difficult, because the planet it must reach is always moving. The probe must be aimed so that it reaches a point in space almost at the same time as its target. It must do this after a journey of many millions of miles, lasting for years.

Voyager space probes

It is an astonishing fact that most probes sent to the planets have reached their targets. In 1989, the American probe Voyager 2 flew past the planet Neptune almost exactly on time, after a 12-year journey. The planet was nearly 3.1 billion miles (5 billion kilometers) away from earth at the time. From this distance, the radio waves from Voyager took over four hours to reach the earth.
A Voyager probe photographed Saturn on its journey into the outer solar system. It used nuclear generators to make electricity.
Solar cells couldn’t be used because sunlight is too weak near Saturn.

Venera space probe

Most probes study a planet as they fly past it. But some actually land on the planet and report back from its surface.
A Russian probe, called Venera, was the first to land on a planet. It parachuted down to Venus in 1970. Since then, several Venera probes have sent back pictures of its surface.
Two American Viking probes landed on Mars in 1976. They sent back pictures and reported on the Martian weather. They also examined the soil for signs of life—but didn't find any!

What is the Function of the Kidneys and How do Kidneys Work?

The kidney filters body fluids within the nephron units and expels wastes via the ureter.

Kidney is one of a pair of organs located at the back of the abdomen, against the strong muscles next to the spine, and behind the intestines and other organs.
The adrenal glands lie on top of the kidneys.
Each kidney weighs about 5 ounces (140g) and is about 4 inches (10cm) long in the average adult.
Its inner structure, which is called the renal pelvis, collects urine as it is formed and passes it out of the kidney to the bladder via the ureter.
The renal pelvis also is connected to the artery and vein that carry blood to and from the kidney.

What is the function of the Kidneys?

The kidneys filter out water and also unwanted substances in the blood.
These substances are produced by the normal working of the body.
They are excreted by the kidneys in the form of urine.
The kidneys also keep the salts and water of the body in correct balance.

How do kidneys work?

The blood passes through each kidney under high pressure.
The blood is filtered by the glomeruli, special structures in the kidney containing clusters of capillaries that collect water, salts, and unwanted substances.
The filtrate passes along a fine tube, the nephron (of which there are approximately one million in each kidney), which reabsorbs any of the water, glucose, and salts that the body still re-quires and allows the rest to pass into the pelvis of the kidney as urine.

Albinism Definition - What is Albinism and What Causes Albinism?

Albinism is the lack of brown pigment - melanin, and a person with such property is called albino. The appearance of albinism can also be found in Africa.
Albinism may be partly inherited. Many people are not albinos, but passed the traits of albinism to their children.

What causes albinism?

The color of the skin, hair, eyes, etc.. in humans is the result of the interaction of various substances in the body.
One are the substances that form the basis of future color, and other are the enzymes that act on that basis.
If someone doesn’t has one of these two substances, or their relationship is disturbed, the result is albinism.
The name derives from the Latin word albus, meaning white.

Albinism symptoms

Albinos have pink eyes, because the red blood in the retina of the eye.
Albinos eyes are very sensitive to light. That's why they keep flashing and keep partially lowered eyelids.
Hair and body hair of Albinos are white.
Even the tissues in the body are white, such as brain and spinal cord.

Albinism exists not only in humans but also in animals of all species. 
It was also found in birds.
Albinos are probably white mice, rats and rabbits, which we all know. There are people who have seen albinos squirrel and even a giraffe albino!

What Are Human Bones Made of?

Strength of normal, healthy human bones is amazing. The bones must be strong, because they make the skeleton which holds the whole body.
Bones vary in shape and size depending on the type of animal to which they belong. Fish and small birds have small bones.

The elephant has bones that are difficult few hundred pounds!

Bone composition

All the bones are of similar composition.
Bone is hard, grey-white color and two-thirds of bone tissue are inorganic or mineral substances, especially lime phosphate.
This gives the bone its hardness, but at the same time makes them brittle.
The remaining third of the bone makes organic matter. It gives bone strength and resistance to fracture. The center of the bone is spongy and filled with bone marrow.
Some of bone marrow fat is stored in the second part and the core creates blood cells. In the bones there is a small amount of water, which, with the aging of the body, gradually disappears.
With less water in the bones, greater is the amount of minerals, causing bones to become brittle and break after slowly coming together.

Interesting Facts About Bones

• Humans have about 300 bones when born. Some of these, fuse together creating a single bone. When maturity is reached, humans have 206 bones in the body.
• The teeth are not counted as bones.
• The greatest bone in the body, “the femur”, is around 1/4 of the persons height. 
• The smallest bone in the body is the stapes (stirrup) located in the middle ear, with size around 1/10 of an inch (2.8 millimetres).
• The only bone which is full-grown at birth is the stapes bone, and is situated in the ear.
• Hand, fingers and wrist make the area of the body with most bones - 54.
• The bones of an adult person make approximately 14 % of the total body weight.
• The bones are made of approximately 75 % of water
• Human bones start to grow from birth, until mid 20's. 
• Broken bones re-grow and repair themselves. 
• The human skeletal system has six major functions: 1. production of blood cells, 2. support, 3. movement, 4. protection, 5. storage of ions and 6. endocrine regulation.
• The Bone marrow makes up 4% of a human body mass.

What is the Endocrine System?

Endocrine System is a network of ductless glands of internal secretion. The endocrine glands produce and/or store various hormones, which are secreted directly into the bloodstream.

The chief endocrine gland is the pituitary, situated beneath the brain and divided into two lobes.

The front (anterior) lobe produces a group of stimulating (tropic) hormones that are carried to other endocrine glands—the thyroid, adrenals and sex glands—to trigger hormone production.

Other anterior pituitary hormones exert their influence directly.

They include prolactin, which maintains milk production from the breasts, and growth hormone. The back (posterior) of the pituitary stores two hormones:

• ADH (vasopressin) - is carried to the kidneys to help control body water content;  
• Oxytocin - assists the contraction of the uterus during labor and encourages the flow of milk from the breasts after the birth of the baby.

 The pineal gland secretes melatonin. The function is uncertain in humans but may help regulate sexual development and menstruation.

Each of the adrenal glands, situated over the kidneys, is divided into an outer (cortex) and inner (medulla) region. The medulla makes the hormones adrenaline (epinephrine) and noradrenaline (norepinephrine), which help to prepare the body for "fight or flight" in response to danger. The hormones of the cortex include steroids involved in the metabolizing of sugars and proteins and in balancing body water content.

The thyroid gland lies below the voicebox or upper part of the windpipe. It secretes hormones that control the rate at which cells use nutrients. Attached to the back of the thyroid are the four small parathyroid glands whose hormones regulate the amounts of calcium and phosphate in the blood, an activity vital to bone building.

The amount of glucose in the blood is governed by cells in the pancreas, situated beside the duodenum.

The endocrine cells of the gland are clustered m small masses and make two hormones: glucagon, which raises blood glucose levels, and insulin, which decreases them.

The sex glands—ovaries in a female and testes in a male—produce hormones that control the production of mature sex cells and help to determine a person's total sexual development.

Do Polar Bears Hibernate in Winter? - hibernation for kids

Hibernating animals breathe much more slowly and their body temperature falls. 
They also need much less food. 
They build up a thick layer of fat during the warmer months and use it up very slowly during hibernation.

Unlike brown and black bears the polar bears do not overwinter in dens.

Only pregnant polar bears enter a den, give birth, and emerge three months later.

Most of the polar bears are active throughout the year, because they are able to reduce their metabolic rate when food is scarce and adjust it again when food is abundant.

The scientists call this walking hibernation.

Polar bears during the walking hibernation maintain normal body temperature, and they are able to save energy by reducing their metabolic rate and recycling proteins.