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marino5856

Clocks - How Time Works - 1 views

  • 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."
    • marino5856
       
      There is 24 hours in a day because  they first divided 60 and that equals 12. So 12 plus 12 equals 24 so thats how they had 24 hours in a day.
  • 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:
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  • Why are there 24 hours in a day? No one really knows. However, the tradition goes back a long way. Take, for example, this quote from Encyclopedia Britannica:
  • Why are there 60 minutes in an hour and 60 seconds in a minute? Again, it is unclear. It is known, however, that Egyptians once used a calendar that had 12 30-day months, giving them 360 days. This is believed to be the reason why we now divide circles into 360 degrees. Dividing 360 by 6 gives you 60, and 60 is also a base number in the Babylonian math system.
    • marino5856
       
      The Egyptians had a calendar that has 12 months so that equals 360 day in total. Also science they new that there is 360 days in a year thats why a circle is 360 degrees. The Roman people invented that so that in the clock there is not 24 hours in a clock so there is 12 am and 12pm.
  • What do a.m. and p.m. mean? These abbreviations stand for ante meridiem, before midday, and post meridiem, after midday, and they are a Roman invention. According to Daniel Boorstin in his book The Discoverers, this simple division of the day into two parts was the Romans' first increment of time within a day:
marino5856

Why are there 24 hours in a day? › Ask an Expert (ABC Science) - 0 views

  • "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.
    • marino5856
       
      The 24 hours has been invented by the egyptians. They first divided it into 10 hours but then they divided it in 12 because of the twilight. So night time was divide in 12 hours because they wanted to see the stars in the night and also that there would be light in the day.
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  • The subdivision of hours and minutes into 60 comes from the ancient Babylonians who had a predilection for using numbers to the base 60. For example, III II (using slightly different strokes) meant three times 60 plus two or 182.
  • "We have retained from the Babylonians not only hours and minutes divided into 60, but also their division of a circle into 360 parts or degrees," says Lomb.
  • While each country has (in broad terms) historically had distinct measurements for distance, weights etc the method of splitting the day into 24 hours, one hour into 60 mins and one minute into 60 seconds seems to be the only one in use, and indeed to me the only one I know of. This non-metric measurement of time is far from ideal, but what other comparably accurate methods have been used historically?
marino5856

Why We Divide the Day Into Seconds, Minutes, and Hours - 0 views

  • The concept of needing to divide up the day seems second nature to even the smallest kid who asks, “is it snack time”.   The reality is, even though we’ve decided that there is a need to divide up time, the actual process and the way we go about it has been changing for millennia.  The cruel irony is that even though we know we need to measure time, there has never been a consensus on what time really is.
    • marino5856
       
      The day is divided into minutes, seconds, and hours because of snack time so it all depended in how many times would we eat. That is equal to 12 hours plus the night so another 12 hours. Thats why there are 24 hours in a day.
marino5856

Curious About Astronomy: Why is a day divided into 24 hours? - 0 views

  • December 2003 answer: It appears that the Egyptians were responsible for the 24 hour day. The Eqyptians were fond of counting in base twelve (instead of base 10 which is commonly used today). This is thought to be because they counted finger joints instead of fingers. Each of your fingers has three joints, so if you count by pointing to finger joints with your thumb you can count to twelve on each hand. This might seem arbitrary, but is actually just a strange as counting in base ten simply because we have ten digits.
    • marino5856
       
      The egyptians were the ones that were in charge of the 24 hours in a day because they had a system so they found  a counting base in twelve.
  • The Egyptians divided the clock into 12 hours of daytime and 12 hours of night-time (or alternatively 10 hours between sunrise and sunset, an hour for each twilight period and 12 hours of darkness). This is known because of various sundials from the period which have been found to be marked with hours. Interestingly this means that hours started out changing in length with the seasons (as the amount of daylight vs. darkness changes).
    • marino5856
       
      they divided the clock in 12 hours because 12 in the night and about 10 in the sunrise that it became 12hours so that it is equal.
    • marino5856
       
      The egyptians divided the clock into 12 hours. 1,2,3,4,5,6,7,8,9,10,11,12 a.m and 1.2.3.4.5.6.7.8.9.10.11.12 p.m so that all the p.m could see the stars and the a.m the sunrise. Like there are 12 a.m and 12 p.m so 12 plus 12 equals24 thats why we have 24 hours in a day.
marino5856

Why is a minute divided into 60 seconds, an hour into 60 minutes, yet there are only 24... - 0 views

  • Thanks to documented evidence of the Egyptians' use of sundials, most historians credit them with being the first civilization to divide the day into smaller parts. The first sundials were simply stakes placed in the ground that indicated time by the length and direction of the resulting shadow. As early as 1500 B.C., the Egyptians had developed a more advanced sundial.
    • marino5856
       
      Thanks to the duodecimal system. The  egyptians used the system to make counting more easier. Also the number 12 is typically attributed.
  • A T-shaped bar placed in the ground, this instrument was calibrated to divide the interval between sunrise and sunset into 12 parts. This division reflected Egypt's use of the duodecimal system--the importance of the number 12 is typically attributed either to the fact that it equals the number of lunar cycles in a year or the number of finger joints on each hand (three in each of the four fingers, excluding the thumb), making it possible to count to 12 with the thumb.
  • The next-generation sundial likely formed the first representation of what we now call the hour. Although the hours within a given day were approximately equal, their lengths varied during the year, with summer hours being much longer than winter hours
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  • Egyptian astronomers also first observed a set of 36 stars that divided the circle of the heavens into equal parts. The passage of night could be marked by the appearance of 18 of these stars, three of which were assigned to each of the two twilight periods when the stars were difficult to view. The period of total darkness was marked by the remaining 12 stars, again resulting in 12 divisions of night (another nod to the duodecimal system).
    • marino5856
       
      Egyptians noticed that there was 36 stars in each part so they divided that into equal parts 12.
marino5856

Ever wonder why a day has 24 hours and a minute has 60 seconds - OMG Facts - The World'... - 0 views

  • 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!
    • marino5856
       
      The egyptians  divided the night into 12 hours. So know the people are used t have 24 hours in a day. Many people think it was born like that but it wasn't the egyptians divided the night into 12 hours and also the day into 12 hours. That is 24 hours in total of the day.
garzat5774

BrainPOP | Hair - 1 views

    • garzat5774
       
      All mammals have hair in there body because they need to keep themselves warm when it's cold, we are warm blooded as the rest of the mammals. all mammels have hair exept the water mammels like whales and dolphins but they keep warm there bodies by eatins a lot of amilals and get layers of fat that will keep them warm, but etherway they have at least a little bit of hair one point during there lives. 
    • garzat5774
       
      Hummans have hair in almost every part of our body, some places that don't include our lips, the palms of your hand and the souls of your feet. But our hair is different in each part of your body. One type of hair is the lauguno hair, wish is the hair babies are covered with.Another type of hair is the vellus hair wish is the hair moat of your body is covered with, those hair is the one in your legs and arms and mesures less than 1 inch,And the 3rd type is the terminal hair wish is longer than an inch and grows in the top of your head and other places.
    • garzat5774
       
      how doe your hair grow? first before you are born tiny foccils are formed inside your skin, foccils are like roots but for hair. you have a ton of focills you have 100,000 yust in your head alone. AT the bottom of each foccils you have thousands of cells with are dividing each second , as they divide and are craetedb the old ones are pushed out and out of you head this makes hair
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    • garzat5774
       
      each hair has 2 or 3 diffrent types of layers the outermost layer is called the cuticle wich protects the rest of the hair. the middle hair is called the cortex, and the center of the hair is caled meddul, you only have medulla in your terminal hair and if you are a natural blande you dont have any meddula at all.
Eugenio Ferrara

The Mariners' Museum | EXPLORATION through the AGES - 0 views

  • 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.
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  • What is known for certain is that Leif and the boy eventually found each other and the young man was recognized as his son.
  • Nevertheless, Leif left the island and got to Norway by the fall. King Olaf welcomed him to his court and asked if Leif had plans for a voyage to Greenland. The king had recently been converted to Christianity and wanted Leif to proclaim Christianity to the Norse settlers living in Greenland, including his parents. He returned to Greenland, and as the king wished, spread the message of Christianity. Leif’s mother, Thjodhild, quickly adopted the new religion, but his father, Eric, was reluctant to give up his pagan beliefs. Only when Thjodhild refused to live with
  • him as man and wife, did Eric the Red finally convert to Christianity.
  • Leif Eiriksson’s exploration and discovery of America was inspired by the accidental voyage of Bjarni Herjulfson.
  • As a skilled sailor and trader, Herjulfson had devoted himself to going on trading voyages from Iceland every other year
  • In 1002 BCE, Leif Eiriksson decided to explore the unknown lands discovered by Herjulfson while on the quest for his father.
  • Leif bought a ship from Bjarni and gathered a crew of thirty-five men.
  • Eric, his father, was approached about being the expedition leader. A fall from a horse prior to embarking convinced Eric that he would be unlucky on the voyage and that he was too old to set off on another adventure. Leif himself took command and the ship and crew departed.
  • The first country Leif encountered was the last one Herjulfson had seen. It was barren, with glacier-topped mountains and vast stretches of rock-covered ground
  • Initiating the practice of naming the lands he found after their geological and physical traits, he called this area Helluland, or “land of flat rocks.” (Labrador)
  • The second country Leif sailed to was level and wooded, with deep white beaches and a sloping shoreline. He called this place Markland (Newfoundland) or “forest land.” Leaving there, he sailed northeast. He found an island north of the mainland. He and his crew sailed the channel between the island and mainland and steered west. When they found land they went ashore, discovering a small river that flowed to the sea. They returned, took the ship up the river to a lake where they decided to build houses, and stayed through the winter.
  • The area had salmon in the river and lake; the winter was mild and almost frost-free, and the grass did not wither during the cold season.
  • The hours of daylight and nighttime were more equally divided than in either Iceland or Greenland
  • Leif divided his crew in half, determined to explore the area. Half would stay in camp while the other half went as a group to investigate the surroundings. The exploration crew was to go no further than the distance they could travel in order to return to camp by nightfall.
  • to explore the area. Half would stay in camp while the other half went as a group to investigate the surroundings. The exploration crew was to go no further than the distance they could travel in order to return to camp by nightfall.
marchand5892

How does the normal heart work? - 0 views

  • Your heart is a specialised muscle that pumps blood around your body. Blood carries oxygen and nourishment to all parts of your body and carries waste products to several organs, notably your lungs and kidneys to eliminate. Your heart is divided into two pumps which work together. Blood coming back from the organs and tissues of your body enters the right side of your heart which then pumps it to your lungs. Your lungs remove waste carbon dioxide from the blood and recharge it with oxygen. The oxygen-rich blood returning from your lungs enters the left side of your heart, which then pumps it to all parts of your body, including your heart muscle itself. This process ensures that there is always enough oxygen and nourishment for your body to work efficiently.
  • t is a specialised muscle that pumps blood around your body. Blood carries oxygen and nourishment to all parts of your body and carries waste products to seve
  • Your heart is a specialised muscle that pumps blood around your body. Blood carries oxygen and nourishment to all parts of your body and carries waste products to several organs, notably your lungs and kidneys to eliminate.
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    • marchand5892
       
      Everyone's heart is a special muscle, that "pumps around your body" and pumps blood out." The blood gets pushed and picks up the oxygen and the the blood travels through your body and drops the oxygen for the heart to circulate  
Nany Rocha

Gender Focus | The History of Pink for Girls and Blue for Boys - 1 views

  • But did you know that pink hasn’t always been a colour for girls, or blue for boys? In Michael Kimmel’s outstanding Manhood in America: A Cultural History, he points out that clothing wasn’t colour-coded in America until the early twentieth century, before which little boys and girls were dressed pretty much identically. Even when people started pushing for more gender-specific children’s clothing, there was a huge debate over which colour to assign to which gender. It started out with boys wearing pink or red because the colours were seen to indicate strength, while girls wore blue because they were “flighty” like the sky. From a 1918 editorial called “Pink or Blue” cited by Kimmel:
    • Nany Rocha
       
      Michael Kimmel pointed out that color coding wasn't used in the vintage america.In fact little boys and little girls used to dress up the same way.But then people wanted to make little kids use specific colored clothes.It started with boys wearing pink or red stuff because the colors where supposed to symbolize strength,while girls used blue because it was soft and dainty (Delicate).
  • So basically the colours changed based on which colour was seen to denote the strength of boys and delicacy of girls, but the idea that those traits are inborn and inalienable did not. It’s not just clothes: walk through the girls’ section of any Toys R Us and you’ll see shelf after shelf of pink, pink, pink. While little girls enjoy some leeway to play with blue toys, many boys get mocked if they want to play with pink “girls’ toys” and sometimes their parents and relatives start panicking that they might even grow up to be (gasp) gay. The fact that parents worry about the sexuality of their kids at all is crazy enough in itself, but that’s for another time. Back to colour-coding.
  • If you think boys and girls just forget about coding gender based on colour once they hit puberty, you’d be wrong. Maricopa County Sheriff Joe Arpaio made headlines when he started forcing male inmates to wear pink underwear to humiliate them. He says it’s a deterrent to reoffending because inmates don’t want to come back and be forced to wear pink again. How screwed up is it that we’ve given a colour so much meaning in less than 100 years that it would make grown male criminals tremble just to think about wearing it?
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  • his is about more than policing convicts, it’s about policing the boundaries of masculinity and reinforcing homophobia. Kimmel states: “Homophobia is more than the irrational fear of homosexuals…[it] is the fear of other men – that other men will unmask us, emasculate us, reveal to us and the world that we do not measure up, are not real men.” The pink and blue shoe keychains might not seem like a big deal, and indeed most people don’t think twice about them. But imagine how much harder it could be for some trans and intersex people to negotiate a restroom ritual like this. Gender-neutral washrooms are a big step towards fixing this issue, but so is realizing that blue-pink colour coding is just the tip of the iceberg of things we use to arbitrarily divide “masculine” from “feminine”.
    • Nany Rocha
       
      Gender stereotypes are something that might not seem important,but actually it is a bit important because it kind of symbolizes what a girl or boy will or would use as clothes or other things.I really think that all this stereotypes are dum because it actually doesn't make sense.
marino5856

hour (unit of time) -- Encyclopedia Britannica - 0 views

  • 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.
    • marino5856
       
      It also has 24 hours the earth because in the system of the egyptians it said that it also has 24 hours because of the earth spinning.
  • 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.
garzat5774

How birds fly | Sciencelearn Hub - 0 views

  • Birds have many physical features, besides wings, that work together to enable them to fly. They need lightweight, streamlined, rigid structures for flight. The four forces of flight – weight, lift, drag and thrust – affect the flight of birds.
  • Flying birds have: lightweight, smooth feathers – this reduces the forces of weight and drag a beak, instead of heavy, bony jaws and teeth – this reduces the force of weight an enlarged breastbone called a sternum for flight muscle attachment – this helps with the force of thrust light bones – a bird’s bones are basically hollow with air sacs and thin, tiny cross pieces to make bones stronger – this reduces the force of weight a rigid skeleton to provide firm attachments for powerful flight muscles – this helps with the force of thrust a streamlined body – this helps reduce the force of drag wings – these enable the force of lift.
  • WingsThe shape of a bird’s wing is important for producing lift. The increased speed over a curved, larger wing area creates a longer path of air. This means the air is moving more quickly over the top surface of the wing, reducing air pressure on the top of the wing and creating lift. Also, the angle of the wing (tilted) deflects air downwards, causing a reaction force in the opposite direction and creating lift.Larger wings produce greater lift than smaller wings. So smaller-winged birds (and planes) need to fly faster to maintain the same lift as those with larger wings.Wing loading tells you how fast a bird or plane must fly to be able to maintain lift: wing loading = weight/wing area (kilograms per square metre).A smaller wing loading number means the bird/plane can fly more slowly while still maintaining lift and is more manoeuvrable.
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  • GlidingWhen a bird is gliding, it doesn’t have to do any work. The wings are held out to the side of the body and do not flap. As the wings move through the air, they are held at a slight angle, which deflects the air downwards and causes a reaction in the opposite direction, which is lift. But there is also drag (air resistance) on the bird’s body, so every now and then, the bird has to tilt forward and go into a slight dive so that it can maintain forward speed.
  • SoaringSoaring flight is a special kind of glide in which the bird flies in a rising air current (called a thermal). Because the air is rising, the bird can maintain its height relative to the ground. The albatross uses this type of soaring to support its multi-year voyages at sea.
  • FlappingBirds’ wings flap with an up-and-down motion. This propels them forward. The entire wingspan has to be at the right angle of attack, which means the wings have to twist (and do so automatically) with each downward stroke to keep aligned with the direction of travel.
  • Birds obtain thrust by using their strong muscles and flapping their wings. Some birds may use gravity (for example, jumping from a tree) to give them forward thrust for flight. Others may use a running take-off from the ground.
  • Different birds have different adaptive features to meet their flight needs: Some birds are small and can manipulate their wings and tail to manoeuvre easily, such as the fantail (pīwakawaka). The hawk, with its large wingspan, is capable of speed and soaring. Gannets and seabirds are streamlined to dive at high speeds into the ocean for fish. Godwits, although small, are equipped to fly long distances.
    • garzat5774
       
      birds have some chacteristics that help them fly, birds are light weighted they have light feathers insted of heavy ones that add more weight to their bodys, they also have a beak insted of jaws that also add weight to their boddys, thay have hollow bones in their body that means that the bone has nothing inside it
    • garzat5774
       
      birds get ready to fly by flapping their wings, some birds use "gravity" to take of some run and they jump just like an airplane and others jump from a tree and then start flapping their winds
marino5856

BrainPOP | Time Zones - 0 views

    • marino5856
       
      The earth is divided in 24 time zones. Time zones go north south pole  to north pole, they are meridians, They are 360 that are degrees. Thats why they are different times. They are the same minute but different hour to the west of it  and highest hour to the east. Smaller goes to west  and bigger to east. The earth rotates. Thats why the hour changes. Like the sun is up it has a different hour than when the moon is up. The earth soins 15 degrees per hour. The sun rises in L.A. at the same minute than N.Y. when it is getting dark.
marino5856

Earth's Rotation - 0 views

  • The earth rotates about an imaginary line that passes through the North and South Poles of the planet.  This line is called the axis of rotation.  Earth rotates about this axis once each day (approximately 24 hours).  Although you most likely already knew that fact, there is a slight complication most people are not aware of.
  • More specifically, our rotation period (the time elapsed for one rotation) with respect to the stars  is called a sidereal day.  A sidereal day is 24 sidereal hours, or 23 hours and 56 minutes on a normal clock.  Our clock time is based on the earth's rotation with respect to the sun from solar noon to solar noon.  This is a solar day, and it is divided into 24 hours.  Because Earth travels about 1 / 365 of the way around the sun during one day, there is a small difference between solar time and sidereal time.
    • marino5856
       
      The earth rotates with axis lines and  there is 24 lines thats why there are 24 hours in a day. The earth time is rotated into 24hours because the earth rotate 1/365 during one day.
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