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TIME & CALENDARS. Sidereal day vs. solar day  Sidereal day: a day with respect to the stars.  Solar day: a full rotation with respect to the sun. 

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Presentation on theme: "TIME & CALENDARS. Sidereal day vs. solar day  Sidereal day: a day with respect to the stars.  Solar day: a full rotation with respect to the sun. "— Presentation transcript:

1 TIME & CALENDARS

2 Sidereal day vs. solar day

3  Sidereal day: a day with respect to the stars.  Solar day: a full rotation with respect to the sun.  Difference is arising from ْ motion of Earth every day.  It will take ْ /day )1440 min/360 ْ (= = 3 min 56 s /day extra time  Since 1 day = 24 h x 60 min = 1440 min.

4 Time Zones

5 Midnight Sun  The midnight sun is a natural phenomenon occurring in summer months at latitudes north and nearby to the south of theArctic Circle, and south and nearby to the north of the Antarctic Circle where the sun remains visible at the local midnight. Given fair weather, the sun is visible for a continuous 24 hours, mostly north of the Arctic Circle and south of the Antarctic Circle. The number of days per year with potential midnight sun increases the farther poleward one goes.natural phenomenonlatitudesArctic CircleAntarctic Circlesun

6 Midnight Sun  Canada (Yukon, Northwest Territories, andNunavut), CanadaYukonNorthwest TerritoriesNunavut  United States of America (Alaska), United States of AmericaAlaska  Denmark(Greenland), DenmarkGreenland  Norway, Norway  Sweden, Sweden  Finland, Finland  Russia, Russia  Extremities of Iceland.Iceland

7 Leap years  One solar year is days  Leap year: A year in which a 366 day is added.  Julian Calendar: The calendar with normal years with 365 days, and leap years every 4 th year without exception.  Gregorian Calendar: The calendar in current use, with normal years with 365 days, and leap years every 4 th year, except for years that are divisible by 100 but not by 400 years.

8 Example  Classify the following years into normal or leap: 1990, 1992, 1900, 2000, 1800, 1600, 2010, 2100  Normal years: 1990, 1900, 1800, 2010, 2100  Leap years: 1992, 2000, 1600

9  Julius Caesar  Augustus Caesar  Gregorian Calendar started 1582 (1600 years after Julian calendar)  The error has grown to 10 days.  To bring calendar in synchrony with seasons, 10 days were eliminated from the year  The day after Oct. 4 was Oct. 15 th 1582

10  Adopted in UK 1752  Russia early 20 th century  a.m. = ante meridian  p.m. = post meridian  B.C. = before Christ  1 B. C. is it the year of his birth, or the next year?  A. D.  after death  A. D. = anno Domini (The year of the Lord).

11 Origin of Month names JanuaryJanus, the god of the doorway, a two faced god looking to the past and to the future Februaryfebruum, which means purification MarchThe god Mars AprilGoddess of love MayGreek goddess Maya JuneJunius, an old roman noble family JulyJulius Caesar AugustAugustus Caesar SeptemberSeventh month OctoberEighth month NovemberNinth month DecemberTenth month

12 Lunar Calendar  354 d 8h 48m  A Lunar year = 354 days or 355 days  A Lunar month = 29 days or 30 days

13 Lunar Monthes  مـــحـــرم : أحد الأشهر الحرم التي حرم القتال فيها.  صــفــر : قيل : أن ديار العرب كانت تصفر أي تخلو من أهلها للحرب.  ربيع الأول وربيع الآخر : سميا بهذا الاسم في فصل الربيع وظهور العشب.  جمادى الأولى والثانية : جميع الأشهر العربية مذكرة إلا جمادى الأولى والأخرى. وكان جمادى الأولى يسمى قبل الإسلام باسم جمادى خمسة، وسمي جمادى لوقوعه في الشتاء وقت التسمية حيث جمد الماء.  رجـــب : كان العرب في الجاهلية يعظمون هذا الشهر بترك القتال، ولا يستحلونه فيه. واسمه من رجب الشئ أي هابه وعظمه.  شــعــبــان : تشعبت القبائل في هذا الشهر للإغارة بعد قعودها عنها في رجب.  رمــضــان : وافق زمن الحر والرمض، والرمضاء هي شدة الحر.  شـــوال : قيل : ان الإبل كانت تشول بأذنابها أي ترفعها وقت التسمية طلبا للإخصاب وقيل : لتشويل ألبان الإبل، أي نقصانها وجفافها. وقيل : شوال الارتفاع درجة الحرارة وإدباره.  ذو الــقــعــدة : قيل : ان العرب كانوا يقعدون فيه عن الأسفار. وقيل : قعودهم عن القتال لأنه من الأشهر الحرم.  ذو الــحــجــة : هو شهر الحج.


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