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A day consists of two 12-hour periods, for a total of 24 hours. An hour consists of 60 minutes. A minute consists of 60 seconds. Seconds are subdivided on a decimal system into things like "hundredths of a second" or "millionths of a second."

hat's a pretty bizarre way to divide a day up. We divide it in half, then divide the halves by twelfths, then divide the twelfths into sixtieths, then divide by 60 again, and then convert to a decimal system for the smallest increments. It's no wonder children have trouble learning how to tell time.

How long is a day? It's the amount of time it takes for the Earth to rotate one time on its axis. But how long does it take the Earth to rotate? That is where things become completely arbitrary. The world has decided to standardize on the following increments:

The second planet from the Sun is Venus. After the Moon, Venus is the most brilliant natural object in the nighttime sky. It is the closest planet to Earth, and it is also the most similar to Earth in size, mass, volume, and density. These similarities suggest that the two planets may have had similar histories. Scientists are thus intrigued by the question of why Venus and Earth are now so different.

"The origin of our time system of 24 hours in a day with each hour subdivided into 60 minutes and then 60 seconds is complex and interesting," says Dr Nick Lomb, consultant curator of astronomy, from the Sydney Observatory.

Our 24-hour day comes from the ancient Egyptians who divided day-time into 10 hours they measured with devices such as shadow clocks, and added a twilight hour at the beginning and another one at the end of the day-time, says Lomb.

"Night-time was divided in 12 hours, based on the observations of stars. The Egyptians had a system of 36 star groups called 'decans' — chosen so that on any night one decan rose 40 minutes after the previous one.

Hours after bedtime, do you find your little one wandering the hall looking dazed and confused? If you have a sleepwalking child, you're not alone. It can be unnerving to see, but sleepwalking is very common in kids and most sleepwalkers only do so occasionally and outgrow it by the teen years. Still, some simple steps can keep your young sleepwalker safe while traipsing about. Despite its name, sleepwalking (also called somnambulism) actually involves more than just walking. Sleepwalking behaviors can range from harmless (sitting up), to potentially dangerous (wandering outside), to just inappropriate (kids may even open a closet door and pee inside). No matter what kids do during sleepwalking episodes, though, it's unlikely that they'll remember ever having done it! As we sleep, our brains pass through five stages of sleep — stages 1, 2, 3, 4, and REM (rapid eye movement) sleep. Together, these stages make up a sleep cycle. One complete sleep cycle lasts about 90 to 100 minutes. So a person experiences about four or five sleep cycles during an average night's sleep. Sleepwalking most often occurs during the deeper sleep of stages 3 and 4. During these stages, it's more difficult to wake someone up, and when awakened, a person may feel groggy and disoriented for a few minutes. Kids tend to sleepwalk within an hour or two of falling asleep and may walk around for anywhere from a few seconds to 30 minutes.

in timekeeping

3,600 seconds, now defined in terms of radiation emitted from atoms of the element cesium under specified conditions. The hour was formerly defined as the 24th part of a mean solar day—i.e., of the average period of rotation of the Earth relative to the Sun. The hour of sidereal time, 1/24 of the Earth’s rotation period relative to the stars, was about 10 seconds shorter than the hour of mean solar time.

In even earlier systems of timekeeping, an hour was 1/12 of a period of daylight or darkness—hence, variable in length with seasonal changes in the length of day and night. The custom of dividing the cycle of day and night into 24 periods seems to have originated with the ancient Egyptians.

Egyptians (who used base 12) developed a sundial which looked like a T-shaped bar placed in the ground with would divide the time between sunrise and sunset into 12 parts. Because of the seasonal change in the length of time between sunrise and sunset, summer hours were longer than winter hours! Historians theorize that the importance of 12 is based on the number of finger joints on each hand (not counting the thumb) or the number of lunar cycles in a year. The division of the night into 12 parts was achieved by Egyptian astronomers who observed the appearance of 12 key stars in the night sky. Out of these divisions was born the concept of a 24-hour day. However, seasonal hour length was used for many centuries, and fixed hours became common only after the appearance of mechanical clocks in 14th century Europe!

Whenever we don't have a good understanding of a subject, say, of people or countries, then we tend to make assumptions about them. Stereotype is nothing but those assumptions that have become common knowledge. Whenever you make judgments about people without knowing them, you are stereotyping them. Stereotyping makes people generalize things. More often, they are all false assumptions. Though there are both positive and negative stereotypes, a majority of them are offensive. People generally stereotype out of bias against a particular group of people or religion. Stereotyping becomes a way of conveying their dislike. Of course, stereotyping stems from a commonly held view of a particular group or race. This view may arise from an incident or false assumption, and then maybe used to color the entire community with the same brush. There are various types of stereotypes. However, the most common ones are racial stereotypes and gender stereotypes. Race, nationality, gender and sexual orientation are the main factors of stereotyping. Stereotyping must be avoided at all costs, as it leads to treating groups as a single entity. Given below are examples of stereotypes that people commonly use.

Examples Of Stereotypes Negative Stereotypes All blond women are dumb. All red heads are sluts. Christians are homophobic. They are blinded by God and will recruit you if you go near them. All politicians are philanders and think only of personal gain and benefit. If I wear Goth clothing I'm a part of a rock band, depressed, or do drugs. Girls are only concerned about physical appearance. Guys are messy and unclean. Men who spend too much time on the computer or read are geeks. Men who are not into sports are termed as gay. All librarians are women who are old, wear glasses, tie a high bun, and have a perpetual frown on their face. Girls are not good at sports. All teenagers are rebels. All children don't enjoy healthy food. Only anorexic women can become models. Women who smoke and drink do not have morals. Men who like pink are effeminate.

Positive Stereotypes All Blacks are great basketball players. All Asians are geniuses. All Indians are deeply spiritual. All Latinos dance well. All Whites are successful. Asians have high IQs. They are smarter than most in Math and Science. These people are more likely to succeed in school. African Americans can dance. All Canadians are exceptionally polite. French are romantic. All Asians know kung fu. All African American men are well endowed. Italians are good lovers

Marco Polo was a Venetian, but where he was actually born is not known with complete certainty. He was born in either the city of Venice or the city of Korcula, Croatia. In Polo’s day, the city was called Curzola, Venetian Dalmatia. Regardless of where he was born though, Marco was raised in Venice, and was Venetian by culture. Marco came from a family of explorers and traders, but it was his name that has become so famous because he took the time to write about all of his adventures.

His father, Nicolo, and his uncle, Maffio, moved around Eastern Europe searching for a place to safely do business trading Eastern goods to the West. Eventually, in 1264, Nicolo and Maffio were sent by Ilkhan Hulagu of Bukhara (one of the minor Khans of the Mongolian Empire) on a mission to visit his brother Kublai, the Great Khan. After traveling for two years, they finally reached Khanbaliq (modern-day Beijing). The Polos were sent back from the Khan with a Mongolian ambassador, Koeketei. The Khan wanted them to carry a message to the Pope, asking for a team of Westerners to come and teach Western culture and Christianity to those under his rule. They were unable to immediately fulfill this request because there was a three-year gap, from 1268 to 1271, during which there was no Pope to whom to carry this message. After Pope Gregory X was selected in 1271, the Polos left on their second journey.

(about 80 times per second

At the heart of the solar system is our sun. The four planets nearest it are rocky, terrestrial worlds — Mercury, Venus, Earth and Mars. After that are four gas giants — Jupiter, Saturn, Uranus and Neptune. Between the orbits of Mars and Jupiter lies the asteroid belt, which includes the dwarf planet Ceres. Beyond the orbit of Neptune one finds the disk-shaped Kuiper belt, in which dwarf planet Pluto resides, and far beyond that is the giant, spherical Oort Cloud and the teardrop-shaped heliopause. See the structure of the solar system (infographic).

d. He had brothers, Thorvald and Thorstein, and a half-sister, Freydis. In the year 999 BCE, Ericsson sailed to Norway to visit King Olaf Trygvson. On his way the ship was blown off course and he landed on one of the Hebrides islands. Continuing poor weather made it impossible for him to leave so he spent the summer on the island.

. She gave birth to his son and as his departure date drew near, she asked that he take her with him. He refused, citing her family connections. Thorgunna had a reputation for being able to predict the future, and vowed that even though Leif was leaving them, one day she and their son would journey to find him and the experience would not be a good one.

, while other sources claim that when the boy was old enough to travel, he found Leif.