Transcript Chapter 16 - Department Of Computer Science

Phys141 Principles of Physical Science
Chapter 16
Place and Time
Instructor: Li Ma
Office: NBC 126
Phone: (713) 313-7028
Email: [email protected]
Webpage: http://itscience.tsu.edu/ma
Department of Computer Science & Physics
Texas Southern University, Houston
Nov. 15, 2004
Topics To Be Discussed
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Cartesian Coordinates
 Latitude and Longitude
 Time
 Skip §16.4 - §16.6
The Concept of Place and Time
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In physical science we observe and examine
events in our environment
Events occur at different places and at
different times, so they are separated in place
and time
Space and time are related – Albert Einstein
Place – location of an object
Time – reference to periodic changes
Cartesian Coordinates
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The location of an object in our environment
requires a reference system with one or more
dimensions
– 1-D: one number line, the Celsius temperature
scale
– 2-D: two number lines, perpendicular to each
other, the point of intersection is assigned as the
origin
Cartesian Coordinates (cont)
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The 2-D reference system is known as
Cartesian coordinate system or rectangular
coordinate system
x-axis: the horizontal line
y-axis: the vertical line
Every position or point in the plane is
assigned a pair of coordinates (x,y)
The x and y coordinates give the distances
from the y and x axes
Latitude and Longitude
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Any position on a rectangular plane can be
located using Cartesian coordinate system
 We can also determine the location of any
position on the spherical surface using two
reference circles
 They are analogous to the Cartesian
coordinate axes
 Latitude and longitude on the surface of the
Earth
Latitude and Longitude (cont)
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A coordinate system known as latitude and
longitude can be used to determine the
location of an object on the spherical surface
of the Earth
 Equator: an imaginary line circling the Earth
at the surface, halfway between the north and
south geographic poles
– The equator is a great circle
Latitude and Longitude (cont)
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Parallels: imaginary circles drawn around the
Earth parallel to the equator
– Parallels are not great circle
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Meridians: imaginary lines drawn along the
surface of the Earth running from the north
geographic pole, perpendicular to the
equator, to the south geographic pole
– A meridian is half of a great circle
Meridians
Parallels
Equator
Latitude and Longitude (cont)
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The latitude of a surface is defined as the
angular measurement in degree north or
south of the equator
– The latitude angular is measured from the center
of the Earth relative to the equator
– The latitude angular is measured along a meridian
– Parallels are lines of equal latitude
– Equator 0°, the North pole 90°N, the South pole
90°S
Latitude and Longitude (cont)
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The longitude is defined as the angular
measurement in degree east or west of the
reference meridian
– This reference meridian is called Greenwich, or
prime meridian
– 0° at Greenwich meridian (minimum value), 180°
east and west are the maximum values
– The pair of latitude and longitude can determine
the location on the Earth’s surface
Latitude and Longitude (cont)
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Parallels become smaller as the distance
from the equator becomes greater
 The meridians are half circles, portions of a
great circle
 Most maps are drawn with north at the top,
south at the bottom, east at the right, and
west at the left
Time
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The second is the standard unit of time
 For everyday purposes, the day is an
important unit of time
 The day has been defined in two basic ways:
– The solar day is the elapsed time between two
successive crossings of the same meridian by the
Sun
Time (cont)
– The sidereal day is the elapsed time between two
successive crossings of the same meridian by a
star other than the Sun
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Because the Sun is much closer to the Earth
than other stars, the solar day is longer than
the sidereal day by about 4 minutes
 The Earth rotates 365.25 times during a
revolution, revolves 0.985° in a day
Time (cont)
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Different local solar time is defined according
to the position of the Sun
 12 noon (local solar time) is the time when
the Sun is on this meridian
– Ante meridian (A.M.): the hours before noon
– Post meridian (P.M.): the hours after noon
Time Zone
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Standard time zones: this scheme
theoretically divides the surface of the Earth
into 24 time zones, each containing 15° of
longitude or 1 hour
– The first zone begins at the prime meridian
– All places within a zone have the same time,
which is the time of the central meridian of that
zone
Time Zone (cont)
– Traveling west into a different zone, you will “save
an hour” – need to move the hour hand of your
watch back 1 hour
– Traveling east into a different zone, you will “lose
an hour” – need to set the hour hand of your
watch ahead 1 hour
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International Date Line (IDL):
– was established at the 180° meridian
Time Zone (cont)
– When one crosses the IDL traveling west-ward,
the date is advanced to the next day
– When one crosses the IDL traveling east-ward,
one day is subtracted from the present date
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Practical problem regarding to time zones:
find the time and date in a distant city when
knowing your local standard time and date
Assignment
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Homework Assignment
– Review Questions (page 433 – 434):
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1,6,14,17,18,24,25,29,30
– Exercises (page 435):
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2,4
– It’s due Monday, 11/29/04
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Reading Assignment
– Chapter 17