Math Is Fun Forum

Combination Quotes - I

1. A good head and a good heart are always a formidable combination. - Nelson Mandela

2. There are three principal means of acquiring knowledge... observation of nature, reflection, and experimentation. Observation collects facts; reflection combines them; experimentation verifies the result of that combination. - Denis Diderot

3. Software is a great combination between artistry and engineering. - Bill Gates

4. I believe myself to possess a most singular combination of qualities exactly fitted to make me pre-eminently a discoverer of the hidden realities of nature. - Ada Lovelace

5. God gave women intuition and femininity. Used properly, the combination easily jumbles the brain of any man I've ever met. - Farrah Fawcett

6. Mathematical reasoning may be regarded rather schematically as the exercise of a combination of two facilities, which we may call intuition and ingenuity. - Alan Turing

7. Tennis is a perfect combination of violent action taking place in an atmosphere of total tranquility. - Billie Jean King

8. The future of food security will depend on a combination of the ecological prudence of the past and the technological advances of today. - M. S. Swaminathan.

Time Zone

Gist

Time zones divide the world into 24 segments, each about 15 degrees of longitude wide, to standardize time, as the Earth rotates 15 degrees every hour. They create uniform local times, offset from Coordinated Universal Time (UTC), allowing for synchronized schedules despite different sunrises/sunsets, with political boundaries often adjusting ideal 15-degree lines for practicality and some regions using Daylight Saving Time (DST).

Time zones are primarily based on the Earth's rotation and its division into 24 longitudinal sections, with each representing one hour of the day. The prime meridian, located at Greenwich, England (Greenwich Mean Time or GMT), serves as the starting point for defining time zones.

Summary

A time zone is an area which observes a uniform standard time for legal, commercial, and social purposes. Time zones tend to follow the boundaries between countries and their subdivisions instead of strictly following longitude, because it is convenient for areas in frequent communication to keep the same time.

Each time zone is defined by a standard offset from Coordinated Universal Time (UTC). The offsets range from UTC−12:00 to UTC+14:00, and are usually a whole number of hours, but a few zones are offset by an additional 30 or 45 minutes, such as in India and Nepal. Some areas in a time zone may use a different offset for part of the year, typically one hour ahead during spring and summer, a practice known as daylight saving time (DST).

Details

Time zone is a zone on the terrestrial globe that is approximately 15° longitude wide and extends from pole to pole and within which a uniform clock time is used. Time zones are the functional basis of standard time and were introduced in the late 19th century as railways connected places that had differing local times.

Different time zones occur because of the way in which Earth spins. Earth rotates 360 degrees every 24 hours, and therefore different parts of the planet experience daylight and darkness at different times. To coordinate time with daylight, the globe is divided into 24 segments, each 15 degrees of longitude apart. The prime meridian in Greenwich, England, serves as the starting point for these divisions, creating a global framework for timekeeping.

While the theoretical model of time zones is straightforward, practical adjustments are often made to accommodate political, social, and economic factors. For instance, some regions have chosen to adopt time offsets of 30 or 45 minutes instead of the standard one-hour difference. These adjustments are made to better align with local solar time or to unify time within a country, as seen in places such as Newfoundland, Iran, and India.

Before the concept of time zones, each locality set its time based on the Sun’s position, leading to a chaotic array of local times. This system became impractical with the advent of rapid railway transportation in the late 19th century, which required a more uniform timekeeping system to avoid confusion in scheduling. The introduction of standard time zones was a solution to this problem, allowing regions to adopt a consistent time standard.

International Date Line is an imaginary line extending between the North Pole and the South Pole and arbitrarily demarcating each calendar day from the next. It corresponds along most of its length to the 180th meridian of longitude but deviates eastward through the Bering Strait to avoid dividing Siberia and then deviates westward to include the Aleutian Islands with Alaska. South of the Equator, another eastward deviation allows certain island groups to have the same day as New Zealand.

The International Date Line is a consequence of the worldwide use of timekeeping systems arranged so that local noon corresponds approximately to the time at which the sun crosses the local meridian of longitude. A traveler going completely around the world while carrying a clock that he advanced or set back by one hour whenever he entered a new time zone and a calendar that he advanced by one day whenever his clock indicated midnight would find on returning to his starting point that the date according to his own experience was different by one day from that kept by persons who had remained at the starting point. The International Date Line provides a standard means of making the needed readjustment: travelers moving eastward across the line set their calendars back one day, and those traveling westward set theirs a day ahead.

Coordinated Universal Time (UTC) is the international basis of civil and scientific time, which was introduced on January 1, 1960. The unit of UTC is the atomic second, and UTC is widely broadcast by radio signals. These signals ultimately furnish the basis for the setting of all public and private clocks. Since January 1, 1972, UTC has been modified by adding “leap seconds” when necessary.

UTC serves to accommodate the timekeeping differences that arise between atomic time (which is derived from atomic clocks) and solar time (which is derived from astronomical measurements of Earth’s rotation on its axis relative to the Sun). UTC is thus kept within an exact number of seconds of International Atomic Time and is also kept within 0.9 second of the solar time denoted UT1. Because of the irregular slowing of Earth’s rate of rotation by tidal friction and other forces, there is now about one more (atomic clock-derived) second in a solar year than there are UT1 seconds. To remedy this discrepancy, UTC is kept within 0.9 second of UT1 by adding a leap second to UTC as needed; the last minute of December or June is made to contain 61 seconds. The slowing of Earth’s rotation varies irregularly, and so the number of leap seconds by which UTC must be retarded to keep it in epoch with UT1 cannot be predicted years in advance. Impending leap seconds for UTC are announced at least eight weeks in advance by the International Earth Rotation and Reference Systems Service at the Paris Observatory, however.

Universal Time (UT), the mean solar time of the Greenwich meridian (0° longitude). Universal Time replaced the designation Greenwich Mean Time in 1928; it is now used to denote the solar time (q.v. : quod vide : which see) when an accuracy of about one second suffices. In 1955 the International Astronomical Union defined several categories of Universal Time of successively increasing accuracy. UT0 represents the initial values of Universal Time obtained by optical observations of star transits at various astronomical observatories. These values differ slightly from each other because of the effects of polar motion (q.v.). UT1, which gives the precise angular coordinate of the Earth about its spin axis, is obtained by correcting UT0 for the effects of polar motion. Finally, an empirical correction to take account of annual changes in the Earth’s speed of rotation is added to UT1 to convert it into UT2. Coordinated Universal Time (q.v.), the international basis of civil and scientific time, is obtained from an atomic clock that is adjusted in epoch so as to remain close to UT1; in this way, the solar time that is indicated by Universal Time is kept in close coordination with atomic time.

Standard Time, the time of a region or country that is established by law or general usage as civil time.

The concept was adopted in the late 19th century in an attempt to end the confusion that was caused by each community’s use of its own solar time. Some such standard became increasingly necessary with the development of rapid railway transportation and the consequent confusion of schedules that used scores of different local times kept in separate communities. (Local time varies continuously with change in longitude.) The need for a standard time was felt most particularly in the United States and Canada, where long-distance railway routes passed through places that differed by several hours in local time. Sir Sandford Fleming, a Canadian railway planner and engineer, outlined a plan for worldwide standard time in the late 1870s. Following this initiative, in 1884 delegates from 27 countries met in Washington, D.C., and agreed on a system basically the same as that now in use.

The present system employs 24 standard meridians of longitude (lines running from the North Pole to the South Pole, at right angles to the Equator) 15° apart, starting with the prime meridian through Greenwich, England. These meridians are theoretically the centres of 24 Standard Time zones, although in practice the zones often are subdivided or altered in shape for the convenience of inhabitants; a notable example of such alteration is the eastward extension of the International Date Line around the Pacific island country of Kiribati. Time is the same throughout each zone and differs from the international basis of legal and scientific time, Coordinated Universal Time, by an integral number of hours; minutes and seconds are the same. In a few regions, however, the legal time kept is not that of one of the 24 Standard Time zones, because half-hour or quarter-hour differences are in effect there. In addition, Daylight Saving Time is a common system by which time is advanced one hour from Standard Time, typically to extend daylight hours during conventional waking time and in most cases for part of the year (usually in summer).

Additional Information

Data spotlights represent data and statistics from a specific period of time, and do not reflect ongoing data collection. As individual spotlights are static stories, they are not subject to the Bureau of Transportation Statistics (BTS) web standards and may not be updated after their publication date. Please contact BTS to request updated information.

Before the establishment of time zones in 1883, there were more than 144 local times in North America. The resulting time differences between adjacent towns and cities were not critical when it took days to travel from place to place. With the proliferation of railroads, faster travel became possible across large geographies, and travelers could sometimes arrive at an earlier local time than they had departed. Due to this lack of time standardization, train scheduling proved difficult to coordinate, resulting in missed connections and collisions. As a result, the major railroad companies began to operate on a coordinated system of four time zones starting in 1883.

Because the development of standardized time was transportation-driven, the government coordination of time zones was handled by transportation agencies. In 1918, the federal organization in charge of railroad regulation — the Interstate Commerce Commission (ICC) — was given the power to address coordination concerns. That year, five time zones were officially adopted as the US entered World War I: the Eastern, Central, Mountain, Pacific, and Alaska zones, all of which are still in use today. However, the need for coordination among all transportation modes became increasingly important after World War II. When the Department of Transportation was created by Congress in 1966, it was assigned “the responsibility of regulating, fostering, and promoting widespread and uniform adoption and observance of standardized time” within each time zone.

Daylight Saving Time (DST) was enacted as a legal requirement by the Uniform Time Act of 1966. Motivated by transportation improvements, this act mandated standard time within the existing time zones and established a permanent system of uniform DST, including the dates and times for twice yearly transitions.  While State governments cannot independently change time zones or the length of DST, they can exempt themselves from DST, independent of DOT authority or permission. Nonetheless, DST is observed uniformly across the nation except in American Samoa, Guam, Northern Mariana Islands, Puerto Rico, the Virgin Islands, Hawaii, and most of Arizona.

Today, the Department of Transportation continues to oversee standard time due to its historical and contemporary importance in transportation and associated commercial activity. Time zone boundaries, established by law, can only be changed by the Secretary of Transportation upon a determination that the proposed adjustment serves the “convenience of commerce.” Per DOT policy, a petition requesting such a change must come from the highest political authorities in a State or locality. Several communities have requested changes to their time zone designation over the past two decades, the most recent being Mercer County, North Dakota in 2010, which chose to switch from Mountain to Central Time. Authorizing these changes and keeping track of the legally designated time zone for each area of the U.S. are key facets of the DOT’s oversight of uniform time observance, time zones, and DST.

In 2019, the Bureau of Transportation Statistics (BTS), in coordination with the Office of the General Counsel, created a digital geographic representation of the official written time zone delineations defined in the Code of Federal Regulations (CFR), Title 49, Subtitle A, Part 71 - Standard Time Zone Boundaries. Currently the United States and its territories have 9 time zone boundaries: Atlantic, Eastern, Central, Mountain, Pacific, Alaska, Hawaii–Aleutian, Samoa, and Chamorro.

The DOT Time Zone Boundary Geospatial layer is the verified digital representation of the current time zone delineations as written in the CFR, and is part of the National Transportation Atlas Database (NTAD). This layer provides the American public with detailed, reliable, and authoritative information on time-related authorities and time zone boundaries.

Sternum

Gist

The sternum, or breastbone, is a flat, vertical bone in the center of the chest that forms the front of the rib cage, protecting vital organs like the heart and lungs, and serving as an attachment point for ribs and muscles. It's divided into three parts—the manubrium, body, and xiphoid process—and is crucial for chest stability and breathing. 

The sternum is also commonly known as the breastbone, a flat bone in the center of the chest that connects the ribs and protects vital organs like the heart and lungs. Anatomically, it's divided into three parts: the manubrium, the body (or gladiolus), and the xiphoid process. 

Summary

The sternum (pl.: sternums or sterna) or breastbone is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, lungs, and major blood vessels from injury. Shaped roughly like a necktie, it is one of the largest and longest flat bones of the body. Its three regions are the manubrium, the body, and the xiphoid process.

Structure

The sternum is a narrow, flat bone, forming the middle portion of the front of the chest. The top of the sternum supports the clavicles (collarbones) and its edges join with the costal cartilages of the first two pairs of ribs. The inner surface of the sternum is also the attachment of the sternopericardial ligaments. Its top is also connected to the sternocleidomastoid muscle. The sternum consists of three main parts, listed from the top:

* Manubrium
* Body (gladiolus)
* Xiphoid process

In its natural position, the sternum is angled obliquely, downward and forward. It is slightly convex in front and concave behind; broad above, shaped like a "T", becoming narrowed at the point where the manubrium joins the body, after which it again widens a little to below the middle of the body, and then narrows to its lower extremity. It is usually longer in the male than in the female.

Details

Your sternum, or breastbone, is a flat, vertical bone at the center of your chest that protects your organs and muscles. It connects to other bones and muscles and forms part of your ribcage, which protects your heart and lungs. Many different conditions can cause sternum pain, but most aren’t serious.

Overview:

What is the sternum?

Your sternum is a flat, T-shaped bone at the center and front of your chest. Your sternum protects the organs and muscles inside your chest from injury. It also connects to other bones and muscles with cartilage. It forms part of your ribcage, which protects your heart and lungs. Another name for your sternum bone is your breastbone.

Function:

What is the function of the sternum in the ribcage?

Your sternum (breastbone) works with your ribcage to protect the organs within your chest. This includes your:

* Stomach.
* Esophagus.
* Lungs.
* Heart.
* Blood vessels.

Your breastbone also provides support — it connects to other parts of your skeletal system, including your clavicle (collarbone) and first six sets of ribs. Other muscles in your chest and upper belly (abdomen) connect to your sternum, as well.

Your sternum doesn’t help with movement in your chest or torso. But cartilage that connects your sternum to your ribs helps with minor motions that occur every time you take a breath.

Anatomy:

Where is the sternum?

The breastbone location is at the center and front of your chest. You can find it in your upper chest in front of your thymus. It connects to your clavicles, which run horizontally (from side to side) above it.

What organ is behind your sternum?

Your thymus gland is located behind your sternum (breastbone). This gland is part of your lymphatic system. It’s in charge of training special white blood cells called T-lymphocytes (T-cells).

What are the parts of the sternum?

Your sternum anatomy consists of three bony parts. These parts include:

* Manubrium: The manubrium of the sternum is the wide, handle-like top portion of the bone. This is where your collarbone and first set of ribs attach. The bottom edge of the manubrium borders the body of your sternum, which is where your second set of ribs attach.
* Body: The body of the sternum is in the center. It’s flat, narrow and the longest part of your sternum. Your third, fourth, fifth, sixth and seventh set of ribs attach to your sternum along the body.
* Xiphoid process: The xiphoid process is the lowest part of the sternum. This pointed end piece of your sternum is made of mostly cartilage. As you age, it begins to calcify and turn to bone.

What is the tip of the sternum?

The tip of the sternum is called the xiphoid process. It’s thinner and narrower than the rest of the sternum. Its shape can vary, but it usually forms into a small point at the bottom of the sternum.

What does the sternum look like?

Your sternum measures about 6 inches long from top to bottom. You could compare the shape of your sternum to an upside-down sword. This is because the wide part at the top resembles a handle. The body of the sternum is long and flat, like the blade of a sword. And the xiphoid process at the end of the sternum looks like the tip of a sword.

Conditions and Disorders:

What does it mean when your sternum hurts?

Many issues with your sternum and its surrounding bones and muscles can cause sternum pain. In addition, you may experience substernal pain — discomfort that occurs below or behind your sternum. This type of pain is usually due to gastrointestinal conditions. Some common causes of sternum or substernal pain include:

* Costochondritis.
* Pectus carinatum.
* Sternum (sternal) fracture.
* Sternoclavicular joint injury.
* Collarbone injury.
* Muscle strain.
* Hiatal hernia.
* Acid reflux.
* Pleurisy.
* Bronchitis.
* Pneumonia.

Costochondritis

Costochondritis is a condition that causes inflammation in the cartilage that attaches your ribs to your sternum. An infection, injury or arthritis can cause the condition. Costochondritis causes sharp, stabbing rib pain and tenderness. You usually feel it in your sternal area and the first three sets of ribs, but it can spread to your arms and shoulders. You may also notice warmth and tenderness in the area.

Pectus carinatum

Pectus carinatum is a condition that causes your sternum to stick out more than it should. Other names for the condition include pigeon chest and keel chest because of how it makes your chest appear. Most people with pectus carinatum don’t have symptoms. But, you may experience chest pain when in specific positions or participating in certain activities.

Sternum (sternal) fracture

A sternal fracture occurs when you break your sternum bone, most often due to blunt force trauma. Sternum fractures commonly occur due to auto accidents. They also happen because of sports injuries and falls. There are two types of sternum fractures:

* Direct: When a direct blow to the front of your chest wall causes a break further back in your chest.
* Indirect: When your sternum is injured in such a way that a break occurs closer to the front of your chest.

Sternoclavicular joint injury

Your sternoclavicular joint is the area in your body where your clavicle connects to your sternum. Although rare, you can sometimes develop problems in this joint area due to infections, injuries or arthritis. You’ll experience pain and discomfort if you have an injury there.

Collarbone injury

Your collarbone (clavicle) connects to the top corners of your sternum. Since the two are closely connected, if you injure your collarbone, you’ll feel pain and discomfort in your sternum, as well. You can injure your collarbone through accidents, sports injuries and falls.

Muscle strain

A muscle strain, or a pulled muscle, can occur when you injure a tendon or muscle. Many tendons and muscles are connected to your sternum. Therefore, injuries to a muscle or tendon can also affect your sternum. Muscle strains occur due to overuse, playing sports and coughing too hard.

Hiatal hernia

A hiatal hernia happens when the top of your stomach moves past your diaphragm and into your chest. This affects the area behind your chest and can cause substernal pain (the area behind your sternum). Hiatal hernias are the most common type of hernia.

Acid reflux

Acid reflux occurs when stomach acid causes irritation and inflammation that wears away the lining of your esophagus. This can cause substernal pain. The condition most often affects people with gastroesophageal reflux disease (GERD).

Pleurisy

Pleurisy is a condition that causes inflammation in your pleurae — the sheets of tissue between your ribcage and lungs. Some autoimmune diseases, lung conditions, and bacterial or viral infections can cause pleurisy. This can also cause substernal pain.

Bronchitis

Bronchitis is a condition that causes inflammation in the primary airways leading to your lungs — your trachea (windpipe) and bronchi — causing substernal pain. This inflammation causes your lungs to fill with mucus, leaving you with a nagging cough that can last for weeks.

Pneumonia

Pneumonia is a condition that causes inflammation in the air sacs (alveoli) in your lungs. After the alveoli inflame, they fill with fluid, which can cause sharp chest pains. You may feel this pain behind your sternum.

Additional Information

Sternum, in the anatomy of tetrapods (four-limbed vertebrates), is an elongated bone in the centre of the chest that articulates with and provides support for the clavicles (collarbones) of the shoulder girdle and for the ribs. Its origin in evolution is unclear. A sternum appears in certain salamanders; it is present in most other tetrapods but lacking in legless lizards, snakes, and turtles (in which the shell provides needed support). In birds an enlarged keel develops, to which flight muscles are attached; the sternum of the bat is also keeled as an adaptation for flight.

In mammals the sternum is divided into three parts, from anterior to posterior: (1) the manubrium, which articulates with the clavicles and first ribs; (2) the mesosternum, often divided into a series of segments, the sternebrae, to which the remaining true ribs are attached; and (3) the posterior segment, called the xiphisternum. In humans the sternum is elongated and flat; it may be felt from the base of the neck to the pit of the abdomen. The manubrium is roughly trapezoidal, with depressions where the clavicles and the first pair of ribs join. The mesosternum, or body, consists of four sternebrae that fuse during childhood or early adulthood. The mesosternum is narrow and long, with articular facets for ribs along its sides. The xiphisternum is reduced to a small, usually cartilaginous xiphoid (“sword-shaped”) process. The sternum ossifies from several centres. The xiphoid process may ossify and fuse to the body in middle age; the joint between manubrium and mesosternum remains open until old age.

Q: What is brown, hairy, and wears sunglasses?
A: A coconut on vacation.
* * *
Q: What do you call a fruit that goes into space?
A: A coco-naut.
* * *
Q: Where do intergalactic coconuts grab a drink?
A: At the "Milky Way".
* * *
Q: What do you call people who like to drink hot chocolate all year long?
A: Cocoa-Nuts.
* * *
Q: What did one coconut say to the other?
A: Got milk?
* * *