Dr. SaMeH S. Ahmed

Associate Prof. of Environmental Engineering

Sun's apparent mot


Sun's apparent motion


The motions as described above are simplifications. Due to the movement of the Earth around the Earth-Moon barycenter, the apparent path of the Sun wobbles slightly, with a period of about one month; due to perturbations by the other planets of the Solar System, the Earth-Moon barycenter wobbles slightly around a mean position in a complex fashion. Theecliptic is actually the apparent path of the Sun throughout the course of a year. Also, the Earth does not actually orbit the Sun, but the Solar System barycenter, therefore an alternate definition of the ecliptic is the mean plane of the orbit of Earth-Moon barycenter around the Solar System barycenter.[1][2]

As the Earth takes one year to make a complete revolution around the Sun, the apparent position of the Sun also takes the same length of time to make a complete circuit of the ecliptic. With slightly more than 365 days in one year, the Sun moves a little less than 1° eastward[3] every day. This small difference in the Sun's position against the stars causes any particular spot on the Earth's surface to catch up with (and stand directly north or south of) the Sun about 4 minutes later each day than it would if the Earth did not orbit; our day is 24 hours long rather than the approximately 23 hour 56 minute sidereal day. Again, this is a simplification, based on a hypothetical Earth which revolves at uniform speed around the Sun. The actual speed with which the Earth orbits the Sun varies slightly during the year, so the speed with which the Sun seems to move along the ecliptic also varies. For example, the Sun is north of the celestial equator for about 185 days of each year, and south of it for about 180 days.[4] The variation of orbital speed accounts for part of the equation of time.[5]

[edit]
Relationship to the celestial equator

The plane of the Earth's orbit projected in all directions forms the reference plane known as the ecliptic. Here, it is shown projected outward (gray) to the celestial sphere, along with the Earth's equatorand polar axis (green). The plane of the ecliptic intersects the celestial sphere along a great circle(black), the same circle on which the Sun seems to move as the Earth orbits it. The intersections of the ecliptic and the equator on the celestial sphere are the vernal and autumnal equinoxes (red), where the Sun seems to cross the celestial equator.

As the rotational axis of the Earth is not perpendicular to its orbital plane, the Earth's equatorial plane is not coplanar with the ecliptic plane, but is inclined to it by an angle of about 23°.4, which is known as the obliquity of the ecliptic.[6] If the equator is projected outward to the celestial sphere, forming the celestial equator, it crosses the ecliptic at two points known as theequinoxes. The Sun, in its apparent motion along the ecliptic, crosses the celestial equator at these points, one from south to north, the other from north to south.[3] The crossing from south to north is known as the vernal equinox, also known as the first point of Aries and the ascending node of the ecliptic on the celestial equator.[7] The crossing from north to south is the autumnal equinox or descending node.

The orientation of the Earth's axis and equator are not fixed in space, but rotate about the poles of the ecliptic with a period of about 26,000 years, a process known as lunisolar precession, as it is due mostly to the gravitational effect of the Moon and Sun on theEarth's equatorial bulge. Likewise, the ecliptic itself is not fixed. The gravitational perturbations of the other bodies of the Solar System cause a much smaller motion of the plane of the Earth's orbit, and hence of the ecliptic, known as planetary precession. The combined action of these two motions is called general precession, and changes the position of the equinoxes by about 50 arc seconds (about 0°.014) per year.[8]

Once again, this is a simplification. Periodic motions of the Moon and apparent periodic motions of the Sun (actually of the Earth in its orbit) cause short-term small-amplitude periodic oscillations of the axis of the Earth, and hence the celestial equator, known asnutation.[9] This adds a periodic component to the position of the equinoxes; the positions of the celestial equator and (vernal) equinox with fully updated with precession and nutation are called the true equator and equinox; the positions without nutation are the mean equator and equinox.[10]

[edit]
Obliquity of the ecliptic

Obliquity of the ecliptic is a name used by astronomers for the inclination of Earth's equator to the ecliptic, or of Earth's rotation axis to a perpendicular to the ecliptic. Currently about 23°.4, it varies slightly due to motion of the plane of the Earth's orbit, and hence the ecliptic, with planetary precession.[11]

The angular value of the obliquity is found by observation of the motions of the Earth and planets over many years. Astronomers produce new fundamental ephemerides as the accuracy of observation improves and as the understanding of the dynamics increases, and from these ephemerides various astronomical values, including the obliquity, are derived.

Obliquity of the ecliptic for 20,000 years, from Laskar (1986).[12] Note that the obliquity varies only from 24°.2 to 22°.5 during this time. The red point represents the year 2000.

Until 1983, the angular value of the obliquity for any date was calculated based on the work of Newcomb, who analyzed positions of the planets until about 1895:

ε = 23° 27′ 08″.26 − 46″.845 T − 0″.0059 T2 + 0″.00181 T3

where ε is the obliquity and T is tropical centuries from B1900.0 to the date in question.[13]

From 1984, the Jet Propulsion Laboratory's DE series of computer-generated ephemerides took over as the fundamental ephemeris of the Astronomical Almanac. Obliquity based on DE200, which analyzed observations from 1911 to 1979, was calculated:

ε = 23° 26′ 21″.45 − 46″.815 T − 0″.0006 T2 + 0″.00181 T3

where hereafter T is Julian centuries from J2000.0.[14]

JPL's fundamental ephemerides have been continually updated. For instance, the Astronomical Almanac for 2010 specifies:[15]

ε = 23° 26′ 21″.406 − 46″.836769 T − 0″.0001831 T2 + 0″.00200340 T3 − 0″.576×10−6 T4 − 4″.34×10−8 T5

These expressions for the obliquity are intended for high precision over a relatively short time span, perhaps ± several centuries.[16] J. Laskar computed an expression to order T10 good to 0″.04/1000 years over 10,000 years.[12]

All of these expressions are for the mean obliquity, that is, without the nutation of the equator included. The true or instantaneous obliquity includes the nutation.[17]


The best book

Prayer Times

Click here




Office hours


Sunday:     12-1

Monday:     12-1

Tuesday:     10-12

Wednesday: 10-11

You are welcome to contact me by at any time

You  may also contact me via WhatsApp group, ..

Ext. 2524

Civil Eng. Students

DON'T miss!


Love your department and be proud of your field of study

As we approaching the second midterm exams..  Get ready and remember our offices are open to answer you . do not hesitate to .contact me if you have difficulties


For CE 370 students : I do apologize for did not attend the extra lab session that proposed to be on Wednesday at 6 am.  Sorry

Good Luck


Announcements


My Dear Students

Please visit the  announcement box for the relevant course and make sure that you can download and upload easily, otherwise

.contact me  to sort it out

There will be an orientation session in the midell of this term to help you select your track in Civil and Environmental Engineering

Event

Special Issue

Electrical Power Resources: Coal versus Renewable Energy



  Published Online on January 2016


Mining Engineering


Mining engineering is an engineering discipline that involves practice, theory, science, technology, and the application of extracting and processing minerals from a naturally occurring environment. Mining engineering also includes processing minerals for additional value.

Environmental Engineering

Environmental engineers are the technical professionals who identify and design solutions for    environmental problems. Environmental engineers provide safe drinking water, treat and properly dispose of wastes, maintain air quality, control water pollution, and remediate sites contaminated due to spills or improper disposal of hazardous substances. They monitor the quality of the air, water, and land. And, they develop new and improved means to protect the environment.

Proverb

Actions speak louder than words

Tawasl

تواصل

College of Eng. MU

http://mu.edu.sa/ar


Univeristies

Universities I've worked in


Assuit University (Home University), Egypt


Imperial College, London, UK


Faculty of Engineering, Al-Mergeb University, Libya


King Saud University, KSA

,Majmaah University


Majmaah University has a very nice web page that provide  all information regarding deanships, colleges, activities,  campuses and many others. Search your request in
http://mu.edu.sa/en

Also visit

My Academic Pages

https://www.researchgate.net/profile/Sameh_Ahemd

and give me


Think


How many red balls we need to make balance 

Sports

Egypt vs Tunisia (Handball final)  30/1/2016


Currency Converter


Click here

Translate


Click here

Course 2016/17-1


  1. Computer Applications in Surveying  CE 473
  2. Surveying 1 CE 370
  3. Photogrammetry CE 474
  4. Surveying II  CE 371
  5. Design I  (round 4) CE 498




The Rules of Life

Rule #7

Latest

Member of the Editorial Board: " Journal of Water Resources and Ocean Sciences"  2013

https://www.researchgate.net/profile/Sameh_Ahmed5/?ev=hdr_xprf

Participating in The Third International Conference on Water, Energy and Environment,(ICWEE) 2015 - American University of Sharjah, UAE 24-26 March 2015 with a Paper and Poster

New article

Recovery of Titania from Waste-Sludge of Majmaah Water Treatment Plant

"Production of Titania Nano-particles from Wast-

Sludge

Coming soon



Results of M2 CE311

Student Conference



Participation  in the 6Th Student Conference

With a paper and oral presentation

From the Senior Design Project CE499 -35

See inside, the paper, and presentation

CE 370 Course

Surveying  I -  CE 370 - 2016-2017-1




Power point


Sheets


Lecture notes


Second Midterm Exam



Results


Model Answer
Inside, please follow:

Student Performance Records

CE 371 Course

Surveying II - CE 371 - 2016-2017-1




Lectures





First midterm exam


Lab


Results

See Inside

Student Performance Records

CE473 Course

Computer Applications in Surveying

CE 473



Lecturers


Power point


Sheets


Exams + Quizzes


Results




CE 474 Course

2015-2016-2 - Photogrammetry  CE474




Available 0-1-2-3-4 Power point

Available

Quizzes 2 and 3 with model Answer

Quizzes
Available Chapter 1,2,3,4,5 Lecture notes

Report 1  Cameras Report

Y

60 marks Exams

See Inside

Student Performance Records


CE 360 Course

Environmental Engineering 1



CE 360: Environmental Engineering 1

37-2

Y PP0-1-2-3,4 Power point
Y 1,2,3,4,5 Chapters

Water quality Poster + Climate Change Reports
will be announced (Quiz #2 will be using D2L- Online Quizzes

Y

Quizzez 2,3 and 4 with model answer and results Exams and results

GE 306 Course

Engineering Report Writing


GE 306: Engineering Report Writing

CE 499 Course

Senior Design 2 - CE 499

Meeting on 14-4-2015

Second Best paper from Senior Design Projects in 2015

Paper title:

Evaluation of Groundwater Quality Parameters using Multivariate Statistics- a case Study of Majmaah, KSA

Students:

Abdullah A. Alzeer

Husam K. Almubark

Maijd M. Almotairi

CE 360-Summer Course

Environmental Engineering I


Welcome to CE360 second Term 2015-2016 

Engineering Practice

 Engineering Practice GE 307

What is your opinion

Contact me

Mobile: 00966598311652

[email protected]

Civil and Environmental Engineering Department
College of Engineering, Majmaah University
Majmaah, P.O. 66, 11952, KSA

Thank you

Your frequent visit to my website has helped  a lot to get the 2nd place in the university competition in the  year 1434-2013... Thanks very mush and please keep following my work

زيارتكم المتكررة لموقعي ساهمت في حصولي على المركز الثاني لاحسن المواقع الشخصية بجامعة المجمعة ...لكم جميعا خالص شكري وتقديري

CE 212 - Summer Course

Properties and Strength of Materials 1

CE 212

Y from PP0 to PP 6 + PDF Power points
Y Midterm #2 + Model Answer + results Exams
Y lab 3 Labs

Solution of Quiz 4 + Results HW


CE 311- Summer Course

Soil Mechanics and Foundation Engineering

CE 311

M2+ model Answer + PP 1-9 = PDF 1-9 all are available

Sheets 2 + 4 with model Answers

Results of M2



إحصائية الموقع

عدد الصفحات: 1412

البحوث والمحاضرات: 1541

الزيارات: 51837