Every point on a parallel of latitude is the same distance from the equator, and thus the angle formed between the equator and the latitude line is constant. This is shown in Fig. Parallels of latitude are circles of different sizes see Fig. The largest parallel is at the equator, and the parallels decrease in size towards the poles.
The greater the distance from the equator, either north or south, the higher the latitude. Meridians of longitude are imaginary half-circles running from the North Pole to the South Pole. They are sometimes called lines of longitude. Unlike parallels of latitude that are different sizes, all lines of longitude are the same length. These divisions of the equatorial circle are used to label the meridians.
Meridians are numbered east and west from the prime meridian Fig. Places to the east of the prime meridian have east longitude.
The international date line determines where on earth the date changes. For example, at the same moment the time is am on July 1st in Bangladesh, the time is pm on June 30th in Mexico and midnight on June 30th in England see Fig.
Places located immediately to the right and left of the date line are 24 hours apart. Travelers who cross the dateline heading west lose a day, but travelers who cross the dateline going east gain a day. When traveling east across the dateline, it is actually possible to arrive at your destination earlier than when you left! For practical purposes, the international date line has been adjusted to allow certain land areas to remain together in the same day and time zones.
For example, the extreme eastern tip of Russia, which juts into the Bering Strait, was kept in the easternmost time zone, whereas the U. In another example, the country of Kiribati pronounced KIRR-i-bas drastically changed the date line in so that the entire country could be on the same day at the same time.
Before this, the western part of Kiribati, where the capital lies, would be 22 hours ahead of the eastern portion of the county. Lines of latitude and longitude form an imaginary global grid system, shown in Fig. Any point on the globe can be located exactly by specifying its latitude and longitude. This system is essential for ships at sea that cannot locate their positions using landmarks or coastal navigational aids such as buoys or channel markers.
This system is just as useful for people on land when hiking, driving, or surveying an environment. To locate a point on a globe exactly, degrees of latitude and longitude are further subdivided into minutes and seconds.
In latitude and longitude measurements, minutes and seconds do not refer to time. Instead, they refer to parts of an angle. But, like with time, there are 60 minutes in a degree just as there are 60 minutes in an hour.
Why is Polaris used for navigation in the Northern Hemisphere? What is the significance of Polaris the North Star? Why is Polaris widely used in navigation? Can you see the North Star in Australia? What does the North Star symbolize? What is the North Star Principle? How far off is Polaris? Is the North Star always true north? Does the North Star point to true north? How do you convert magnetic to true north? Does the iPhone compass point to true north?
Why is it important to understand if a map direction is based on true north or magnetic north? Why is it important to identify true north? How does the declination change as you move north? Why does a compass always point to the north direction? Why does a freely suspended magnet align itself in the north south direction?
What happen when the materials were placed near the magnet? Being so far away and only one of a myriad stars visible to the naked eye, the North Star isn't as easy to find as the sun. Furthermore, you can only see it at night, which isn't always convenient.
Its major limitation, however, is that it isn't visible from the southern hemisphere. For our purposes, we shall therefore assume that we're in the northern hemisphere. You can use a simple quadrant to measure latitude using either the sun or the North Star. Both methods are described below. Using a compass, mark out a line on the ground that runs north to south. Make sure that your quadrant is set up so that its aming beam is parallel to this north-south line.
Instead, watch the shadows formed by the nails on the ground as you tilt the aiming beam up and down. At first, the nails will cast two separate shadows, so move the end of the beam up or down so that these two shadows move closer together. When the shadows coincide, the beam is aimed exactly at the sun. Using the protractor, measure the smaller angle between the beam and the plumb line.
The angle to measure when using the sun or North Star. Don't be fooled by mountain ranges! Solar declination - the seasonal consequence of the 'tilted' Earth's annual movement around the sun. Although complex tables almanacs are used to obtain correction factors for any day of the year, you can accurately estimate the appropriate numbers for yourself.
For example, if calculating the value at the beginning of May, you would be half-way between the spring equinox when the sun is directly over the Equator and the summer solstice when the sun is directly above a point You would therefore need to add half of Use the sight line on the top of the aiming beam to align the beam with the North Star. This angle is your latitude. Even though we built a radio, we still needed some sort of timepiece, so we made a pendulum of a certain, known length which we knew would swing with a fixed frequency determined by this length.
To calculate your longitude, you therefore simply need to work out the time difference between noon at your location and noon at the Prime Meridian. It passes through Greenwich in southeast London, and is therefore sometimes referred to as the Greenwich Meridian.
An international conference held in Washington D. As the prime meridian, the north—south line at Greenwich is used as the reference point for all other meridians of longitude, which are numbered east or west of it. The lines all run from the North to the South Pole, at right angles to the Equator.
These meridians are the centres of 24 standard time zones. Time is the same throughout each zone. In practice, many of the zones have been subdivided or their shape altered for convenience. A Walk Through Time. The Constellations and their Stars. Barrow J. Extremely accessible. Burton et al.
Heinemann Educational Publishers Part of the Salters Advanced Chemistry course, which explores the frontiers of research and the applications of contemporary chemistry. For A level and other science courses aimed at 16 to year olds.
Fraser A. Northedge A. Packed with practical exercises and activities, all aimed at making studying more enjoyable and rewarding. Lots of hints and tips for those returning to study. Selinger B. Explores the world of chemistry that surrounds us in our daily lives, explained in terms that everyone can understand.
PS Chemistry for Science Teachers course materials , The Open University, A course designed for use by science teachers from a wide variety of backgrounds, with varying experience of teaching science.
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