How Escalators Work

Escalators are one of the largest, most expensive machines people use on a regular basis, but they're also one of the simplest.
At its most basic level, an escalator is just a simple variation on the conveyer belt. A pair of rotating chain loops pull a series of stairs in a cons­tant cycle, moving a lot of people a short distance at a good speed.
In this article, we'll look inside an escalator to find out exactly how these elements fit together. While it is exceedingly simple, the system that keeps all the steps moving in perfect synchrony is really quite brilliant. What's in a Name? Early escalators were known by a variety of names, including "travelling staircase," "inclined elevator" and "magic stairway." Around 1900, Charles Seeberger, who designed the forerunner of the modern escalator, came up with the name that finally stuck. His term "escalator" is a combination of "elevator" and "scala," the Latin word for steps.

Stepping out

The core of an escalator is a pair of chains, looped around two pairs of gears. An electric motor turns the drive gears at the top, which rotate th­e chain loops. A typical escalator uses a 100 horsepower motor to rotate the gears. The motor and chain system are housed inside the truss, a metal structure extending between two floors.
Instead of moving a flat surface, as in a conveyer belt, the chain loops move a series of steps. The coolest thing about an escalator is the way these steps move. As the chains move, the steps always stay level. At the top and bottom of the escalator, the steps collapse on each other, creating a flat platform. This makes it easier to get on and off the escalator. In the diagram below, you can see how the escalator does all of this.



The individual steps from an escalator

The tracks are spaced apart in such a way that each step will always remain level. At the top and bottom of the escalator, the tracks level off to a horizontal position, flattening the stairway. Each step has a series of grooves in it, so it will fit together with the steps behind it and in front of it during this flattening.

Step Speed Escalator speeds vary from about 90 feet per minute to 180 feet per minute (27 to 55 meters per minute). An escalator moving 145 feet (44 m) per minute can carry more than 10,000 people an hour -- many more people than a standard elevator.

­In addition to rotating the main chain loops, the electric motor in an escalator also moves the handrails. A handrail is simply a rubber conveyer belt that is looped around a series of wheels. This belt is precisely configured so that it moves at exactly the same speed as the steps, to give riders some stability.
The escalator system isn't nearly as good as an elevator at lifting people dozens of stories, but it is much better at moving people a short distance. This is because of the escalator's high loading rate. Once an elevator is filled up, you have to wait for it to reach its floor and return before anybody else can get on. On an escalator, as soon as you load one person on, there's space for another.
reference :: www()howthestufwrks()com

Question Mark ????????????????????????

In the English language, the question mark (?), also known as an interrogation point,interrogation mark, question point, query, or eroteme, is a punctuation mark that replaces the period at the end of an interrogative sentence. It can also be used mid-sentence to mark a merely interrogative phrase, where it functions similarly to a comma, such as in the single sentence "Where shall we go? and what shall we do?", but this usage is increasingly rare. The question mark is not used for indirect questions. The question mark character is also often used in place of missing or unknown data.

Lynne Truss attributes an early form of the question mark to Alcuin of York. Truss describes thepunctus 
 of the late 700s as "a lightning flash, striking from right to left", a mark looking like this. (The punctuation system of Aelius Donatus, current through the Early Middle Ages, used only simple dots at various heights.)

This early question mark was a decoration of one of these dots, with the "lightning flash" perhaps meant to denote intonation (or was it a tilde or titlo, named after the latin word titulus, as in “ ·~ ”, like those wavy and more or less slanted marks used in lots of medieval texts for denoting various things such as abbreviations, and that would become later various diacritics or ligatures or modified letters used in the Latin script?), and perhaps associated with early musical notation like neumes. Over the next three centuries this pitch-defining element (if it ever existed) seems to have been forgotten, so that the Alcuinesque stroke-over-dot sign (with the stroke sometimes slightly curved) is often seen indifferently at the end of clauses, whether they embody a question or not.

In the early thirteenth century, when the growth of communities of scholars (universities) in Paris and other major cities led to an expansion and streamlining of the book-production trade , punctuation was rationalised by assigning Alcuin's stroke-over-dot specifically to interrogatives; by this time the stroke was more sharply curved and can easily be recognised as the modern question-mark.

The symbol is also sometimes  thought to originate from the Latin quaestiō (that is, qvaestio), meaning "question", which was abbreviated during the Middle Ages to Qo. The uppercase Q was written above the lowercase o, and this mark was transformed into the modern symbol. However, evidence of the actual use of the Q-over-o notation in mediaeval manuscripts is lacking; if anything, mediaeval forms of the upper component seem to be evolving towards the q-shape rather than away from it.

many types of question marksssss

Times New Roman question mark	Question mark with drop shade	Red question mark	Opening/closing question marks
Inverted question mark	Question mark	Alternate inverted question mark	Alternate question mark

In Medicine

 A question mark is used in English medical notes to suggest a possible diagnosis. It facilitates the recording of a doctor’s impressions regarding a patient’s symptoms and signs. For example, for a patient presenting with left lower abdominal pain, a differential diagnosis might include ?Diverticulitis (read as 'Query Diverticulitis').

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NETWORKINGGG

In the World of Computers, Networking is the practice of linking two or more computing devices for the purpose of sharing data, networks are build up with a mix of computer hardware and computer software.

Networking can be categorized in several different forms. one approach defines the type of network according to the geographic area it spans . LOCAL AREA NETWORK (LAN) which typically reach across a single home where as  WIDE AREA NETWORK (WAN)  reach cities,states,or even across the world. the internet is world's largest WAN.

In networking their are two types of designs they are client-server and peer- to- peer. client server networks features centralized  server computers that store e-mails,web pages.files.or application. on a  peer-to-peer  networks supports same function . Client-server networks are much more common in business and peer-to-peer networks much more common in homes.A network topology represents its layout or structure from the point of view of data flow. In so-called bus networks, for example, all of the computers share and communicate across one common conduit, whereas in a star network, all data flows through one centralized device. Common types of network topologies include bus, star, ring and mesh.

In networking, the communication language used by computer devices is called the protocol. Yet another way to classify computer networks is by the set of protocols they support. Networks often implement multiple protocols to support specific applications. Popular protocols include TCP/IP, the most common protocol found on the Internet and in home networks.

Many of the same network protocols, like TCP/IP, work in both wired and wireless networks. Networks with Ethernet cables predominated in businesses, schools, and homes for several decades. Recently, however, wireless networking alternatives have emerged as the premier technology for building new computer networks. 

Wi-Fi is the most popular wireless communication protocol for local area networks. Private home and business networks, and public hotspots, use Wi-Fi to networks computers and other wireless devices to each other and the Internet. Bluetooth is another wireless protocol commonly used in cellular phones and computer peripherals for short range network communication.

The technologies used to connect to the Internet are different than those used for connecting devices on local area network. DSL, cable modem and fiber provide fixed broadband Internet service, while WiMax and LTE additionally support mobile connectivity. In geographic areas where these high-speed options are unavailable, subscribers are forced to use older cellular services, satellite or even dial-up Internet instead.

Now a days satellite internet is used widely

Satellite Internet is a form of high-speed Internet service. Satellite Internet services utilize telecommunications satellites in Earth orbit to provide Internet access to consumers.

Satellite Internet service covers areas where DSL and cable access is unavailable. Satellite offers less network bandwidth compared to DSL or cable, however. In addition, the long delays required to transmit data between the satellite and the ground stations tend to create high network latency, causing a sluggish performance experience in some cases. Network applications like VPN and online gaming may not function properly over satellite Internet connections due to these latency issues.

Older residential satellite Internet services supported only "one-way" downloads over the satellite link, requiring a telephone modem for uploading. All newer satellite services support full "two-way" satellite links.

Satellite Internet service does not necessary utilitize WiMax. WiMax technology supplies one method to deliver high-speed Internet service over wireless links, but satellite providers may implement their systems differently.

Most computer networks direct messages from source to destination devices using any of three techniques called routing, switching and bridging. Routers use certain network address information contained inside messages to send them ahead to their destination (sometimes indirectly via one or more additional routers). Switches use much of the same technology as routers but typically support local area networks only. Bridging allows messages to flow between two different types of physical networks.

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"2012" No sign of an end yet to the big freezee

Britain's big freeze showed no sign of easing tonight as heavy snow again brought swathes of the country to a standstill.

Hospitals cancelled operations, the Army was drafted in to rescue motorists and emergency moves to ease the gritting crisis were demanded as a further 1.5ft (47cm) of snow fell in some parts.

Crucial transport networks went into meltdown during heavy flurries across the south while hundreds of thousands of children enjoyed an extension to their     holidays after school closures                                    

With millions unable to get into work on a day estimated to have cost businesses £690 million, forecasters warned the misery will continue into next week.

After striking Scotland and the north of England, the heavy snowfall moved south to the home counties and London - where it was set to continue falling over night

Clare Allen, a forecaster with MeteoGroup, the weather division of the Press Association, said parts of Kent could be worst hit tonight.

She added: "In terms of the overall cold snap, there is no sign of it coming to an end - it goes on as long as we can read into next week."


The lowest temperatures overnight were -13C (9F) in Aboyne, Aberdeenshire, and -10.3C (14F) in Marham, Norfolk. Parts of the northern Highlands recorded 47cm (18.5in), MeteoGroup said.
Emergency measures to alleviate the gritting crisis, allowing Britain's biggest salt mine to supply the country day and night, were put forward by councillors. They said they would look favourably on suspending planning restrictions limiting lorry movements to and from Winsford's salt mine in Cheshire.

FLIGHTS

One of the busiest airports in the country - Gatwick in West Sussex - remained shut for much of the day with more than 240 flights cancelled.

Hundreds were stranded at Stansted after snow forced airport officials to shut the runway. Scores queued for information and passengers wanting to speak to staff at a Ryanair desk were told told to expect a two to three-hour wait. Officials at the airport in Essex said more than 20 flights were cancelled and more than 20 incoming planes diverted. They advised travellers to contact airlines for information about re-booking and compensation. Stansted said the runway had been closed for around two hours from 9am

Budget airline easyJet had to axe more than 250 flights and other carriers were hit by the closure of a number of airports.

Cardiff Airport re-opened and departing flights were operating with delays. Flights to Aberdeen, Anglesey and Amsterdam were cancelled.

The UK's biggest airport - Heathrow in west London - remained open but services there were subject to delays and cancellations.

Cardiff airport will remain closed until at least 3pm. There were delays and cancellations at Manchester, Aberdeen and Leeds Bradford airports.

ROADS

Dyfed Powys Police were appealing to motorists who abandoned their cars yesterday to collect them today. Abandoned cars have become a problem for other drivers in some areas by causing an obstruction. Roads around the village of Keeston, near Haverfordwest, Pembrokeshire, are a particular problem, police said.

An elderly man died after his car went out of control on an icy road, according to police. The pensioner was driving a blue Morris Minor which left the road at the junction of Common Lane and Warsash Road in Titchfield, Hampshire. A police spokesman said: "The driver was found slumped at the wheel. No other vehicles were involved and the driver was pronounced dead at the scene."


Police working with Armed Forces and fire service personnel used military trucks and Land Rovers to access motorists who were caught in a 10-mile jam on the A3(M) trunk road at Waterlooville, Hampshire. Many of those stuck were evacuated to rescue centres while others remained in their vehicles overnight. The Highways Agency warned drivers to avoid the A3 and the A3(M) in Hampshire and Surrey.
Elsewhere, the M27 motorway was passable this morning but traffic was very slow, while many minor roads were hazardous with police advising motorists to stay at home unless absolutely necessary.

On the Isle of Wight, 40 motorists were evacuated to a rest centre at the Riverside Centre in Newport after being found taking cover in a bus shelter by police.

Devon and Cornwall Police warned drivers to make only essential journeys.

NATIONAL RAIL

There were no services between Glasgow and Edinburgh on CrossCountry services, while buses replaced trains between Inverness and Perth in Scotland.

There were no services operating between Sheffield and Leeds on East Midlands Trains, while trees on the line disrupted South West Trains' services between Portsmouth Harbour and Guildford.

First TransPennine Express was unable to run any trains between Carlisle and Edinburgh.

South West Trains - whose routes pass through worst-hit Surrey, Hampshire and Dorset - was running a restricted service today. Southeastern also ran reduced services, although passengers with standard tickets were accepted on the high-speed service without paying the normal supplement.

Chiltern Railways also said it was running an amended timetable, while Virgin Trains warned that trains on all routes via Carlisle were being delayed because of broken down trains caused by the poor weather.



First Great Western, which operates trains between South Wales and London Paddington, was running a severely reduced service. The company was unable to run services between Newton Abbot and Paignton in Devon, while there were delays to its trains between Bristol and Newport/Cardiff and between Exeter St Davids and Plymouth.
National Express East Anglia reported delays to services through Colchester in Essex, while there was a reduced service on the Stansted Express.

The Association of Train Operating Companies said that, by 12.30pm, 61 per cent of trains had run on time, 34 per cent had arrived late and 5 per cent had been cancelled.

It added that train companies were putting extra staff on standby to help deal with the weather conditions and provide information to passengers.

Platforms and approaches to stations were being gritted and customers being kept informed, where possible, by email and text and websites.

Passengers can call a new telephone number - 08453 017 641 - for information.

LONDON

London Overground services between London and Watford Junction in Hertfordshire were suspended.

Tube trains were running today, but with some delays. The Northern line was suspended between High Barnet and Archway, while the Piccadilly line was suspended between Acton Town and Rayners Lane. Some buses had to take diversions.

A Transport for London (TfL) spokesman said: "TfL has well prepared cold weather plans which were put in place across our network again last night, working closely with our partners in the London boroughs.

"Tube, bus and all other TfL services are operating well this morning."Our fleet of 38 gritters have been operating across the TfL road network working to keep the roads and pavements clear and de-icing trains have been running across the Tube, London Overground, Docklands Light Railway and Tramlink networks overnight.

"We will continue to closely monitor weather forecasts and encourage everyone to allow more time for your journey and to check before you travel."

SCHOOLS

North Somerset Council has already announced that all schools within the authority will be closed tomorrow.

At least 320 of Hertfordshire's 520 schools were closed. Hampshire County Council said at least 410 schools out of a total of 536 were shut.

Buckinghamshire County Council said that 176 schools were shut, and Oxfordshire County Council reported the closure of 164 of its schools.

There were also closures in West Berkshire, East and West Sussex, Milton Keynes, Slough, Surrey, Bracknell Forest and Windsor and Maidenhead.

More than 70 schools were shut in Kent, and there were dozens of closures in Brighton.

In Harrow, north London, 58 schools were closed and its 130 Special Needs Transport routes for schoolchildren and vulnerable adults were cancelled.

Other boroughs in the capital fared better, with only a handful of closures in Southwark, Westminster and Camden.

The South West saw several schools closed, including all those in Bath and North East Somerset.

So far 330 schools in Gloucestershire, 143 in Wiltshire, about 200 in Somerset and some 80 in Bristol have shut up shop.

School transport in Swindon and South Gloucestershire was cancelled and the University of the West of England in Bristol was shut.

In Devon and Cornwall, around 450 schools were closed today after reported snowfalls of almost 4in (10cm).

More than 100 schools were closed in Nottinghamshire this morning, including every special school in the county.

In Derbyshire more than 100 schools were shut, nearly 90 in Northamptonshire and around 45 in Bedfordshire.

In Birmingham more than 100 schools were closed after six inches of snow fell in some parts of the city.

Pupils at 39 schools in Coventry were given the day off, with dozens of schools and colleges in Shropshire, Herefordshire and Worcestershire also closing for the day.

In North Wales, more than 430 schools were shut across six councils, with Wrexham Council alone closing 184.

More than 40 schools were closed in Essex today, while education authority officials said a handful of schools were closed in parts of East Anglia because of heating problems.

In the North West, Salford City Council shut all its schools, children's centres and nurseries.

Across Greater Manchester, tens of thousands more pupils got another day off - with local parks becoming playgrounds for hordes of youngsters on sledges.

More than 100 schools in Manchester were closed, with Warrington shutting all its schools.

In Bury, 77 schools were closed, in Wigan 76 schools and colleges were shut, in Salford all of its 102 schools were closed, in Bolton 93 were shut, in Oldham 99, in Tameside, to the east of Manchester, 99 schools were closed, in Stockport around 100 and in Rochdale 68.

Other local authorities reporting school closures included Cumbria and St Helens, and around half the schools in Liverpool were shut.

Elsewhere on Merseyside, 115 schools across Wirral were shut, almost 60 in Knowsley and a similar number in Sefton.

More than 90 schools covered by Cheshire East, Cheshire West and Chester councils gave pupils the day off.

Further afield, around 340 schools were closed across Lancashire.

Hundreds of schools in Yorkshire decided not to open today, including more than 50 in Leeds and more than 100 in South Yorkshire.

More than 300 schools in the North East were closed because of the weather.

In County Durham, 88 schools were shut, while around 90 closed in Tyne and Wear and 152 in Northumberland.

The icy conditions meant several schools were closed in Scotland.

Scottish Borders, Midlothian, East Lothian and Aberdeenshire councils said none of their schools were open for pupils today.

Nine schools in the Western Isles were shut, and in Dumfries and Galloway only a handful of the area's 120 schools were open.

In Aberdeen, 12 schools were closed or partially closed, 41 schools and nurseries were shut in Fife and 21 schools had to close in Edinburgh.

AND ALSO...

* A gritter overturned on an icy road leaving the driver shaken and bruised, a council said today. The gritter was travelling at 20mph when it overturned, Ceredigion County Council said. A crane was used to move the lorry after the accident on the B4343 between Lampeter and Llanddewi Brefi in Ceredigion, Mid Wales. The driver has since returned to work and another lorry has been sent out to take the place of the overturned gritter, which will require major repairs.

* In Knighton, Powys, Mid Wales, a police helicopter delivered food and medical supplies to a family who have been stranded for more than two weeks. A spokesman for Dyfed-Powys Police said the family had difficulty getting out because they were in a very rural location but they were also reluctant to leave their horses uncared for. He added that a member of the family was in need of medication, which was being taken in the helicopter.

* South East Coast Ambulance Service (SECAmb) said it was treating the severe weather conditions as a major incident and warned it would have problems reaching those with minor injuries. Director of operations Sue Harris said: "We are prioritising life-threatening calls above all others, and due to the adverse conditions it is unlikely that we will reach patients with minor injuries and symptoms in worst-hit areas. If you need medical advice please contact NHS Direct on 0845 4647."

* National Grid, which issued only its second ever gas balancing alert (GBA) on Monday after a 30 per cent surge in seasonal demand, said the warning would not be repeated today. GBAs are a way of warning customers on "interruptible contracts" to ease off on the fuel as well as encouraging suppliers to bring in more gas.

* Coastguard rescue teams helped ambulance crews to reach casualties during the heavy snow. Three teams from Hill Head, Lymington and Southampton provided support with 4x4 vehicles to help people whom the other emergency services could not reach.

* Grit stocks in England were generally holding up to demand, according to the Highways Agency. But in north London, Harrow Council said only 650 tonnes of salt remained - enough for four days at the heaviest rate of spreading, or more than a fortnight at a lighter rate. Grit supplies have nearly run out in West Berkshire, one of the most heavily affected areas, with only enough left to cover the main roads one more time. Motorists were urged only to travel if it was absolutely necessary.

refrence : www()independent()co()uk

How the Mayan Calendar Works ?

Most people around the globe look at some form of a calendar every single day. Business executives check to see when their meetings are scheduled. The busy mom confirms soccer practices and piano lessons. College students ensure that their papers are turned in on time and they have plenty of time to study for their history exams. For the people of ancient Maya, calendars were just as important to daily life as they are to people today. In this article, we'll look at how the Mayan calendar came to be and the meaning behind each type of calendar the Mayans created. First, let's get a little background on the Mayans.

The Mayans originated in a region called Mesoamerica, or Middle America. This region lies in betweenMexico and South America and was home to many other cultures, including the Aztec, Olmec, Teotihuacan and Toltec. The Mayans lived in what are today's Guatemala, Belize, Honduras, El Salvador and Southern Mexico (Yucatan, Campeche, Quintana Roo Tabasco and Chiapas).

Mayan history is broken into three periods:

• Formative or Pre-classic - 2000 B.C. until A.D. 300
• Classic - A.D. 300 until A.D. 900
• Post-classic - A.D. 900 until the Spanish Inquisition in the 1400s

The Mayans weren't the first ever to use a calendar -- there were ancient calendars in use throughout civilizations worldwide -- but they did create four different calendars. Depending on their needs, the Mayans used different calendars to record each event, either alone, or in some combination of two calendars.Mesoamericans began writing during the mid-Pre-classic period. The Mayans were the first to keep any sort of historical record, and the beginnings of the calendar were born. The Mayans used stelae, or stone monuments, to carve their civil events, calendars and astronomy knowledge. They also recorded their religious beliefs and mythology on pottery.

The Tzolk'in Calendar

The Tzolk'in calendar was the first one used by the Mayans. Most calendars used throughout Mesoamerica consisted of 260 days. The Tzolk'in, or Sacred Round, calendar followed suit. One theory for its length is that 260 days is the length of pregnancy, and the calendar was based on that [source: Maya Mystery School]. Another states that it was the length of time to cultivate corn. It's more likely that it was based on numbers.

Numbers had great significance in the Mayan culture. For example, the number 20 signifies the number of digits a person has -- 10 fingers and 10 toes. The number 13 refers to the major joints in the human body where it's believed disease and illness enter and attack -- one neck, two shoulders, two elbows, two wrists, two hips, two knees and two ankles [source: Garcia]. The number 13 also represented the levels of heaven where sacred lords ruled the Earth [source: Tzolk'in Calendar].

It's these numbers, 20 and 13, that are used to make up the Tzolk'in calendar. In the Gregorian calendar, we have seven days of the week and, depending on the month, anywhere from 28 to 31 days. The Tzolk'in calendar is made up of 20 day names and 13 numbers. The days are numbered one through 13, and the names are also given in sequence.

Tzolk'in Calendar Day Names
1. Imix'	2. Ik'	3. Ak'b'al	4. K'an
5. Chikchan	6. Kimi	7. Manik'	8. Lamat
9. Muluk	10. Ok	11. Chuwen	12. Eb'
13. B'en	14. Ix	15. Men	16. Kib'
17. Kab'an	18. Etz'nab'	19. Kawak	20. Ajaw

The beginning of the Tzolk'in calendar begins with the first day name, Imix', and the number one. The days continue in sequence until all 13 numbers are used. Then, the numbers begin again with one, but the day names continue with the 14^th day. Once you reach 13 B'en, you will continue on with 1 Ix, 2 Men, 3 Kib', and so forth until you reach 7 Ajaw. At this point, the day names begin again, but the numbers continue: 8 Imix', 9 Ik', 10 Ak'b'al, and so on.

Think of two gears that interlock together. One has the 20 day names and the corresponding hieroglyphics. The other, smaller one has the numbers one through 13. If you lock those gears together at the number one and the day name Imix', then rotate them until you reach one and Imix' again, you'll have 260 unique days, making up the Tzolk'in calendar.

It's easy to see the significance the Mayans put in the Tzolk'in calendar. For example, they believed that the date of your birth determines the characteristics you'll show in your personality -- much like some people believe your astrological sign does today.

The Mayans also used the calendar to determine the crop schedule: It takes one 260-day cycle to prepare the land to plant corn, and one 260-day cycle to grow and harvest the corn.

Holy men used the calendar to determine when certain events would take place throughout the year. At the beginning of each uinal (period of 20 days), a shaman would count forward to determine when religious and ceremonial events would occur. Then he set the dates that would be the most prosperous or lucky for the community.

While these were some of the uses of the Tzolk'in calendar, it couldn't be used for everything. For example, it didn't measure a solar year, the time it takes for the sun to make a complete cycle. Because of this, the Mayans needed a more accurate calendar to measure what we know as a full year.

The Haab Calendar and the Calendar Round

Mayan calendar carved in stone.

The Haab calendar is very similar to the Gregorian calendar that we use today. It's based on the cycle of thesun, and was used for agricultural, economic and accounting activities. Much like the Tzolk'in calendar, it's also comprised of uinals, and each day has its own hieroglyph and number. However, instead of using 13 uinals for 260 days, the Haab calendar has 18 uinals, giving it 360 days.

Astronomers noticed that 360 days wasn't enough time for the sun to make it through a full solar cycle. They argued that the calendar should follow the cycle as closely as it could in order to be as accurate as possible. However, Mayan mathematicians didn't see it that way. They wanted to keep things simple, in increments of 20, just like their math system. The astronomers and mathematicians finally agreed on the 18 uinals, with five "nameless days" called the wayeb [source: The Maya Calendar].

The wayeb, or uayeb, is considered one "month" of five days, and it's thought to be a very dangerous time. The Mayans believed the gods rested during this time, leaving the Earth unprotected. The Mayans performed ceremonies and rituals during the wayeb in hopes that the gods would return once again [source: The Mayan Calendar Portal].

While this calendar was longer than the Tzolk'in, the Mayans wanted to create a calendar that would record even more time. For this reason, the Tzolk'in and Haab calendars were combined to form the Calendar Round.

In the Calendar Round, the 260 days of the Tzolk'in calendar are paired with the 360 days and five nameless days of the Haab calendar. The two calendars are matched the same way the Tzolk'in day names and numbers are (think back to the illustration of the gears on the second page). This gives the Calendar Round 18,890 unique days, a time period of around 52 years.

Neither the Tzolk'in nor the Haab calendars measured more than one year. The Mayans wanted to record history, and decided to create a calendar that would give them a longer span than a year. At the time, the Calendar Round was the longest calendar in Mesoamerica. Historians of the time, however, wanted to record Mayan history for generations to come in the future. They wanted a calendar that would take them through hundreds, even thousands, of years (what we would describe as centuries and millennia). Enter the Long Count calendar.

The Long Count Calendar

Unfortunately, the Long Count calendar isn't as simple as combining two calendars together to get new dates. It' s a little more complicated and abstract. In order to understand the Long Count, you first need to become familiar with a few terms:

• One day - kin
• 20 days - uinal
• 360 days - tun
• 7,200 days - katun
• 144,000 days - baktun

The span of the Long Count calendar is called the Great Cycle, and lasts approximately 5,125.36 years [source: Jenkins]. To find the Lon g Count date that corresponds with any Gregorian date, you'll need to count the days from the beginning of the last Great Cycle. But determining when the last cycle began and matching that up to a Gregorian date is quite a feat. English anthropologist Sir Eric Thompson set out to determine the date, and he looked to the Spanish Inquisition for help.

The Mayan pyramid in Chichen Itza was a physical calendar. Each side has a staircase with 91 steps and a platform, for a total of 365 steps. The dates inscribed into the pyramids all were written in the Long Count format.

What transpired was known as the Thompson Correlation. Events that occurred during the Inquisition were recorded on both the Mayan Long Count calendar and the Gregorian calendar. Scholars then gathered dates that matched on both calendars and compared them to the Dresden Codex, one of four Mayan documents that survived the Inquisition. This codex confirmed the date long thought by Thompson to be the beginning of the current Great Cycle -- August 13, 3114 B.C. [source: Mayan Long Count].

Now that we have the beginning date of the Great Cycle, let's put the Long Count into practice. We'll take a date that's familiar to many Americans -- July 20, 1969, the day Apollo 11 landed on the moon. In the Long Count calendar, this date is written as 12.17.15.17.0 . You'll notice there are five number places in the date. Reading from left to right, the first place signifies the number of baktuns since the beginning of the Great Cycle. In this case, there have been 12 baktuns, or 1,728,000 days (144,000 x 12) since August 13, 3114. The second place relates to the number of katuns that have taken place. Then it continues on to the right with the number of tuns, uinals and kins

Mayan Numbers and Math

Mayan mathematical system-1-20

Along with their advances to the calendar -- like the Tzolk'in, the Haab, and the Long Count -- theMayans also created their own math system. They used a series of dots and bars to signify numbers. One dot equaled one unit while one bar equaled five units. A shell symbol signified zero.

In a system similar to the one we use now, the Mayans used place values to designate large numbers. However, the similarities end there.

Their place values are vertical, where ours are horizontal. For instance, we write the number 27 horizontally -- the number 2, then the number 7 to the right of it. The Mayans, however, would write 27 vertical ly -- their symbol for 7 (a line with 2 dots over it) would be on the bottom, and the symbol for 20 (a dot on the line above) would be directly over it. The same applies for other numbers, like 29.

reference :: science()howstuffworks()com