0
WHAT’S TIME?HOW CAN WE MESURE IT?   WHERE ARE WE?   WHEN ARE WE?
THE SOLAR SYSTEM  THE SUN  9 MAJOR PLANETS  PLANETARY MOONS  2000 MINOR PLANETS & ATEROIDS
KEPPLER LAWS:   1.   Each planet moves in an elliptical orbit with the Sun in        one foci
2.   The straight line joining the Sun and any planet     sweeps out equal areas in equal time intervals
3. K . SP² = d³
RELATIVE POSITION EARTH – SUN:  •   PERIHELION  Closest to the Sun  •   APHELION  Furtherst from the Sun
EARTH’S MOVEMENTS:   1.   ROTATION (West -> East)  DIURNAL CHANGES   2.    ANNUAL MOVEMENT (Orbit)  Due also to axis    ...
IMPORTANT FEATURES:• Earth axis tilted 66.5º to the plane of the ECLIPTIC.               ANGLE BETWEEN EQ AND ECLIPTIC = 2...
IMPORTANT FEATURES:     DECLINATION
Sun at:• Most SOUTHERLY point (Tropic of Capricorn): 22nd Dec                    N.H  WINTER SOLSTICE                    ...
Sun crosses the Equator:• From South to North: 21st of March                  N.H.  SPRING or VERNAL EQUINOX             ...
DEFINITION: The time interval that elapses between two      succesive transits of a heavenly body across the same      mer...
Any heavenly body could be used as a timekeeperSun not the perfect one because its apparent speed along                   ...
APPARENT SOLAR DAY:     Time interval that elapses between two successive     transits of the actual Sun across the same m...
The Sun’s real movement on the ecliptic per day is more than                360º. There are two reasons:  • The Earth is m...
THE MEAN SOLAR DAY Due to the fact of the Sun not moving equally on the skyevery day , and also to the fact of this variat...
THE MEAN SOLAR DAYDEFINITION: Time interval between two succesive transits of       the mean Sun across the same meridian....
EQUATION OF TIMEDEFINITION: Relation in terms of time between the Apparent       time and Mean time for a specific day. Va...
EQUATION OF TIME
SIDERAL YEAR: Time the Earth takes to complete a full orbit      arround the Sun measured against a distant star . 365d   ...
DEFINITION: Time according to the Mean Sun.      The angle, converted to time, from the observers      antimeridian westwa...
UNIVERSAL CO-ORDINATED TIME (UTC/GMT)     LMT at the Greenwich meridian (0ºE/W). Is the time     reference for aviation. T...
DIFFERENCE BETWEEN UTC AND GMT:        Co-ordinated Universtal Time (UTC) changes at aconstant rate and is regulated again...
UNIVERSAL CO-ORDINATED TIME (UTC/GMT):         Example 1: What’s the difference in LMT between London                 Heat...
UNIVERSAL CO-ORDINATED TIME (UTC):         Example 2: If the LMT in Goose Bay (060ºW) is 1200, what is                 the...
DEFINITION:      Earth is divided into 24 time zones, each of 15º of      longitude in width.      Each zone has 1h differ...
FEATURES:  • Each zone is designated by letters: zone 0 = Z,      zone -1 = A,…  • Eastern longitudes are numbered with ne...
DEFINITION:      Time stated for a determined area in accordance with      State’s frontiers of natural geographical borde...
DIFFERENCE BETWEEN STANDARD AND ZONE TIME
STANDARD TIME TABLES (Book):      LIST 1: Contains places where ST is normally fast on              UTC (East of Greenwich...
INTERNATIONAL DATE LINE:        Whenever taking into account LMT, and movingwestwards there will be a moment in which we w...
INTERNATIONAL DATE LINE:
INTERNATIONAL DATE LINE:
EXPLANATION:     Most countries adjust their local time (ST) according to            the season of the year. When this is ...
SUNRISE: Time moment of the day in which the upper limb of      the Sun is coincident with the observer’s visible      hor...
SUNSET: Time moment of the day in which the upper limb of      the Sun is coincident with the observer’s visible      hori...
DEPENDENT ON:   1.   DATE:        •   SUMMER  SR earlier and SS later        •   WINTER  SR later and SS earlier        ...
DEPENDENT ON:   2. LATITUDE:     Times for SR and SS change by several min each 3-     day period and this change is more ...
DEFINITION:       Period of the day before sunrise and after sunset inwhich there is still sifficient illumination for nor...
Period divided into 3 stages:       CIVIL TWILIGHT – Time period between the moment of the               Sun being 6º bell...
1. VARIATION OF TWILIGHT WITH LATITUDE:      LOW LATITUDES: At the Tropics the Sun rises and sets            at almost 90º...
1. VARIATION OF TWILIGHT WITH LATITUDE:       LOW LATITUDES
1. VARIATION OF TWILIGHT WITH LATITUDE:       HIGH LATITUDES
2. VARIATION OF TWILIGHT WITH DECLINATION:      Generally becomes larger when the Suns declination is      higher
2. VARIATION OF TWILIGHT WITH DECLINATION
9. Time
9. Time
9. Time
9. Time
9. Time
9. Time
9. Time
9. Time
9. Time
9. Time
9. Time
9. Time
9. Time
9. Time
9. Time
9. Time
9. Time
9. Time
9. Time
9. Time
9. Time
9. Time
9. Time
9. Time
9. Time
Upcoming SlideShare
Loading in...5
×

9. Time

668

Published on

Presentation given in class about the chapter of time.

Published in: Education, Technology, Business
0 Comments
1 Like
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total Views
668
On Slideshare
0
From Embeds
0
Number of Embeds
1
Actions
Shares
0
Downloads
34
Comments
0
Likes
1
Embeds 0
No embeds

No notes for slide

Transcript of "9. Time"

  1. 1. WHAT’S TIME?HOW CAN WE MESURE IT? WHERE ARE WE? WHEN ARE WE?
  2. 2. THE SOLAR SYSTEM THE SUN 9 MAJOR PLANETS PLANETARY MOONS 2000 MINOR PLANETS & ATEROIDS
  3. 3. KEPPLER LAWS: 1. Each planet moves in an elliptical orbit with the Sun in one foci
  4. 4. 2. The straight line joining the Sun and any planet sweeps out equal areas in equal time intervals
  5. 5. 3. K . SP² = d³
  6. 6. RELATIVE POSITION EARTH – SUN: • PERIHELION  Closest to the Sun • APHELION  Furtherst from the Sun
  7. 7. EARTH’S MOVEMENTS: 1. ROTATION (West -> East)  DIURNAL CHANGES 2. ANNUAL MOVEMENT (Orbit)  Due also to axis inclination in relation to the Sun’s ecliptic. SEASONAL CHANGES Elliptic movement arround Sun (one foci) IMPORTANT POSITIONS (N.H): SUMMER SOLSTICE  21st June WINTER SOLSTICE  22nd Dec VERNAL or SPRING EQUINOX  21st March AUTUMNAL EQUINOX  23rd Sep
  8. 8. IMPORTANT FEATURES:• Earth axis tilted 66.5º to the plane of the ECLIPTIC. ANGLE BETWEEN EQ AND ECLIPTIC = 23.5º Paralel of latitude directly underneath the Sun rays changes slowly SEASONAL CHANGES OVER THE YEAR (DECLINATION)
  9. 9. IMPORTANT FEATURES: DECLINATION
  10. 10. Sun at:• Most SOUTHERLY point (Tropic of Capricorn): 22nd Dec N.H  WINTER SOLSTICE S.H.  SUMMER SOLSTICE• Most NORTHERLY point (Tropic of Capricorn): 21st June N.H.  SUMMER SOLSTICE S.H.  WINTER SOLSTICE
  11. 11. Sun crosses the Equator:• From South to North: 21st of March N.H.  SPRING or VERNAL EQUINOX S.H.  AUTUMN EQUINOX• From North to South: 23rd of September N.H.  AUTUMN EQUINOX S.H.  SPRING or VERNAL EQUINOX
  12. 12. DEFINITION: The time interval that elapses between two succesive transits of a heavenly body across the same meridian Earth rotation ≈ Rotation of celestial sphere Heavenly bodies are continuosly crossing an observer’s meridian in an East – West direction
  13. 13. Any heavenly body could be used as a timekeeperSun not the perfect one because its apparent speed along the ecliptic varies SIDEREAL DAY: Measured against any star (Unable to relate it with light darkness periods) SOLAR DAY: Measured against the Sun
  14. 14. APPARENT SOLAR DAY: Time interval that elapses between two successive transits of the actual Sun across the same meridian APPARENT SOLAR TIME: Time based upon the Sun as it appears on the sky, taking as reference its transit from the observers antimeridian. Measured in refrence to the apparent Sun on a particular meridian.
  15. 15. The Sun’s real movement on the ecliptic per day is more than 360º. There are two reasons: • The Earth is moving on an ecliptic motion arround the Sun • The Earth’s speed is varying arround its orbit
  16. 16. THE MEAN SOLAR DAY Due to the fact of the Sun not moving equally on the skyevery day , and also to the fact of this variation not beingconstant, we can’t consider the Real Sun giving us a practicalunit of measurementTo overcome this dificulty  IMAGINARY BODY = MEAN SUN. Its assumed to move along the celestial equator (ecliptic) at a uniform speed, and to complete one revolution in nearly the mean time it takes to the true Sun tocomplete one revolution in the ecliptic
  17. 17. THE MEAN SOLAR DAYDEFINITION: Time interval between two succesive transits of the mean Sun across the same meridian. CIVIL DAY 360º of longitude = 24 Mean solar hours 15º of longitude = 1 Mean solar hour NOTE: Difference between Apparent and Mean days is nearly a minute
  18. 18. EQUATION OF TIMEDEFINITION: Relation in terms of time between the Apparent time and Mean time for a specific day. Varies throughout the year and its due to the eccentricy* of the Earth’s elliptical orbit arround the Sun EQUATION OF TIME = APPARENT TIME – MEAN TIMEECCENTRICITY = Relationship between the major and minor axes of anellipse. Meassures how simmilar an ellipse and a circumference are
  19. 19. EQUATION OF TIME
  20. 20. SIDERAL YEAR: Time the Earth takes to complete a full orbit arround the Sun measured against a distant star . 365d 5h 48min 45 sec. For ease, 365days and 6hoursCALENDAR YEAR: Taken as 365days. Kept in accordance with the calendar year by adding 1 day to the year each 4 years (Leap year)
  21. 21. DEFINITION: Time according to the Mean Sun. The angle, converted to time, from the observers antimeridian westwards to the Mean Sun Diff Long (A-B)  Diff of LMT (A-B) NOTE: A 24h period implies a 360º rotation and, because of this, 15º rotation (CHLong) is a 1h change in time  Conversion Arc to time Chart
  22. 22. UNIVERSAL CO-ORDINATED TIME (UTC/GMT) LMT at the Greenwich meridian (0ºE/W). Is the time reference for aviation. TIME CONVERSION CALCULUS BETWEEN ANY LMT AND UTC Where a meridian is: • East of Greenwich  Time is LATER Long WEST, UTC BEST • West of Greenwich  Time is EARLIER Long EAST, UTC LEAST
  23. 23. DIFFERENCE BETWEEN UTC AND GMT: Co-ordinated Universtal Time (UTC) changes at aconstant rate and is regulated agains the INTERNATIONALATOMIC TIME (IAT), which is derived from atomic clocks.UTC is regularly corrected to match GMT (LMT at theGreenwich Meridian), but those corrections are very small. For practical purposes, UTC equals GMT
  24. 24. UNIVERSAL CO-ORDINATED TIME (UTC/GMT): Example 1: What’s the difference in LMT between London Heathrow (51º 28’N 000º27’W) and Kennedy Intl (New York) (40º38’N 073º46’W)1. CHLong = 73º46’ – 000º27’ = 73º 19’2. Knowing that 15º change in longitude equal 1h change in time: 73º19’ = 73.316º  73.316º · (1h/15º) = 4.887h = 4h 53min
  25. 25. UNIVERSAL CO-ORDINATED TIME (UTC): Example 2: If the LMT in Goose Bay (060ºW) is 1200, what is the UTC?1. CHLong = 060ºw – 000ºE/W = 60º2. 60º · (1h/15º) = 4.0h3. As Goose Bay is West (Longitude west UTC best) we have to add this difference in LMT to the time of Goose Bay to find the UTC 1200 + 4 = 1600
  26. 26. DEFINITION: Earth is divided into 24 time zones, each of 15º of longitude in width. Each zone has 1h difference to the one right next to it and uses the LMT of its central meridian as time reference.
  27. 27. FEATURES: • Each zone is designated by letters: zone 0 = Z, zone -1 = A,… • Eastern longitudes are numbered with negative zone numbers • Western longitudes are numbered with positive zone numbers • Mathematically UTC = Zone Time + Zone number
  28. 28. DEFINITION: Time stated for a determined area in accordance with State’s frontiers of natural geographical borders. Sometimes listed as LOCAL TIME (LT) Countries like USA, Canada or Australia have such a large east-west extent that need to use multiple time belts, each of them having its own Standard Time
  29. 29. DIFFERENCE BETWEEN STANDARD AND ZONE TIME
  30. 30. STANDARD TIME TABLES (Book): LIST 1: Contains places where ST is normally fast on UTC (East of Greenwich Meridian) LIST 2:Contains places where ST is normally UTC/GMT LIST 3: Contains places where ST is normally slow on UTC (West of Greenwich Meridian)
  31. 31. INTERNATIONAL DATE LINE: Whenever taking into account LMT, and movingwestwards there will be a moment in which we will get to theGreenwich anti-meridian. There its supposed to be a -12hLMT. If we do the same eastwards, will get to the samepoint, but with a supposed time of +12h. Whenever we cross the 180ºE/W meridian we willbe, then, changing day, and depending on which direction weare crossing it to, we will have to change date foreward orbackwards
  32. 32. INTERNATIONAL DATE LINE:
  33. 33. INTERNATIONAL DATE LINE:
  34. 34. EXPLANATION: Most countries adjust their local time (ST) according to the season of the year. When this is done, local time is advanced one hour in the spring, and the Daylight Saving Time (Also called Summer Time) is in efecct. In autumn the clocks are set back to ST again  Energy saving Countries following this rule will be specifyied on the ST Lists by and asterisk *
  35. 35. SUNRISE: Time moment of the day in which the upper limb of the Sun is coincident with the observer’s visible horizon, and the Sun’s tendency is to climb up on the sky. Centre of the Sun in 0.8º bellow the horizon but due to refraction the Sun’s visible before those 0.8º
  36. 36. SUNSET: Time moment of the day in which the upper limb of the Sun is coincident with the observer’s visible horizon, and the Sun’s tendency is to fall bellow the horizon. Centre of the Sun in 0.8º bellow the horizon
  37. 37. DEPENDENT ON: 1. DATE: • SUMMER  SR earlier and SS later • WINTER  SR later and SS earlier Times for SR & SS change slightly from one year to another
  38. 38. DEPENDENT ON: 2. LATITUDE: Times for SR and SS change by several min each 3- day period and this change is more pronounced the higher the atitude. For one particular latitude, all places, regardless of longitude, will have the same LMT for SR and SS
  39. 39. DEFINITION: Period of the day before sunrise and after sunset inwhich there is still sifficient illumination for normal daylightoperations to continue.
  40. 40. Period divided into 3 stages: CIVIL TWILIGHT – Time period between the moment of the Sun being 6º bellow horizon until SR. Or betwee SS and 6º bellow horizon. SETS LIMIT FOR DAY-FLYING NAUTICAL TWILIGHT - Time period betwee the 12º-bellow- horizon position of the Sun until the Civil twilight begins ASTRONOMICAL TWILIGHT – Time period between the moment in which the Sun is 18º bellow horizon to the moment the Nautical twilight begins
  41. 41. 1. VARIATION OF TWILIGHT WITH LATITUDE: LOW LATITUDES: At the Tropics the Sun rises and sets at almost 90º to the horizon. The period is quite short because the way traveled is the shortest possible HIGH LATITUDES: The angle of the Sun approaching the horizon is tilted, the path followed until those 6º bellow horizon will, then, be longer and so will be the time taken. Lasts more at high latitudes
  42. 42. 1. VARIATION OF TWILIGHT WITH LATITUDE: LOW LATITUDES
  43. 43. 1. VARIATION OF TWILIGHT WITH LATITUDE: HIGH LATITUDES
  44. 44. 2. VARIATION OF TWILIGHT WITH DECLINATION: Generally becomes larger when the Suns declination is higher
  45. 45. 2. VARIATION OF TWILIGHT WITH DECLINATION
  1. A particular slide catching your eye?

    Clipping is a handy way to collect important slides you want to go back to later.

×