DOCSLIB.ORG

The Analemma, Dials, and Digits: Some Unusual Combinations, Or Clocks of the Really Long Now Duncan Hall

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Analemma, Dials, and Digits: Some Unusual Combinations, Or Clocks of the Really Long Now Duncan Hall Wellington Astronomical Society May 2017 Volume 47 Issue 4 WWW.WAS.ORG.NZ, ISSN 01147706 - PRINT, ISSN 2230-5912 ONLINE The next WAS meeting will be held on Wednesday 3rd of May 2017 at 7:30 pm at Carter Observatory, Upland Rd, Kelburn, Wellington The analemma, dials, and digits: some unusual combinations, or Clocks of the Really Long Now Duncan Hall As part of his talk, Duncan will demonstrate: • The main aspects of the natural phenomena that power sundials • Various types of solar-powered timepieces, and • A digital clock with a display that uses shadows cast by a mini-gnomon Duncan Hall is a founding member of WAS. Having previously attended the Wellington RASNZ meetings, he signed up as a member of WAS when it was formed in 1974 (he thinks). At various times Duncan has been WAS President, Vice-President, Observatory Director, Council member, and ordinary mem- ber. He is currently a Trustee of the Gifford Observatory Trust. He was a co-Director of the Gifford Observatory in 1974 and 1975 while at Wellington College. Duncan’s had a long-term interest in solar-powered, low-powered, and no-powered timepieces. Inside this issue: Wellington Astronomical Society May 3 2017 Events WAS April Meeting Talks “Introducing the WAS Research Group” by Roland 4 Idaczyk and “Variable Stars” by Aline Homes WAS Observatory Re-establishment at 5 Tawa College NOAA's Joint Polar Satellite System (JPSS) to monitor Earth as never be- 6 fore Occultations for May 2017 7 May Night Sky Chart 15 The Night Sky in May 16 Page 2 VOLUME 47 ISSUE 4 2016 — 2017 SUBSCRIPTIONS DUE The new subscription year began in Adult/Waged: $ 50.00 Box 3181, Wellington 6140 September, so WAS looks forward to Student/Unwaged: $ 30.00 Direct Deposit or Internet Banking - receiving your subscription renewal. use Acc No: 03-0502-0508656-00, Family: $ 70.00 Renewal forms can be found on the please include reference so WAS knows website, but a summary follows: Payment methods: who is making the payment Subscription for Newsletter by Cheque - make out to Wellington As- Cash - please bring exact amount to Email 2016-2017 tronomical Society Inc, and mail to PO meeting It appears that quite a few members from last year have not yet renewed their subscriptions. If this is an oversight, can you please remedy it as soon as possible. WAS COUNCIL MEMBERS AND CONTACTS Council Members The following members were elected to Council at the Nov 2016 Website : Peter Woods AGM [email protected] President: Antony Gomez Council [email protected] / 021_253_4979 Andrew Fuller Vice President: Duncan Hall Edward Wilcock [email protected] Frank Andrews Secretary/Telescope custodian: Chris Monigatti Janine Bidmead [email protected] / 021_890_222 Murray Forbes Treasurer: John Homes Peter Woods Sarah Taylor Newsletter Editor: Gerard Coyle [email protected] Postal Address: Wellington Astronom- Membership Secretary: Janine Bidmead ical Society, PO Box 3181, Wellington [email protected] 6140, New Zealand WAS ON FACEBOOK Our Facebook page “Wellington Astro- Remember you will need to interact anyone to join by request. The public nomical Society” is now operational. occasionally with the page by liking or group is open for discussion or postings You can search for it on Facebook or commenting on postings, or indicating on astronomical news. The WAS Astro- click on this link https:// whether you are coming to an event. photography Group https:// www.facebook.com/ Otherwise Facebook will, after a time, www.facebook.com/ WellingtonAstronomicalSociety/. stop sending you new postings. So keep groups/1684738758511214/ is for those visiting the page as there are a number interested in astrophotography. It If you are a Facebook user, please use of Society events coming up in the next serves as a place to notify others of the page to receive up-to-date notifica- few months. astrophotography gatherings at short tions of our Society’s events and news. notice and to display images captured This is the easiest way to keep informed We also have Facebook group “WAS – by members. as to what is going on in the Society, as Wellington Astronomical Society” well as keeping up with astronomical https://www.facebook.com/ news. groups/96304353012/ which is open for Page 3 VOLUME 47 ISSUE 4 Wellington Astronomical Society May 2017 Events WAS May Meeting Our talk this month will; be given byu As part of his talk, Duncan will mini-gnomon Duncan Hall, and is titled “The ana- demonstrate: Date: Wednesday 3rd May lemma, dials, and digits: some unusual • The main aspects of the natural combinations, or Clocks of the Really Time: 7:30pm, phenomena that power sundials Long Now.” The analemma is the plot Venue: Space Place at Carter Obser- • Various types of solar-powered of how the sun’s position in the sky vatory changes throughout the year when timepieces, and viewed from the same point on the • A digital clock with a display earth’s surface. that uses shadows cast by a Space & Science Festival @Night Evening event focused on Astronomy A full programme is available at Time: 6:00 to 10:00pm, with the Wellington Astronomical S & S Festival Evening programme Venue: Onslow College, Burma Society, Bioluminescent Bug Art with Tickets are required for this event Road, Johnsonville Dr Siouxsie Wiles, Science Talks and S & S Festival Shop fun with Physics. Plus a chance to Date: Saturday 6th May (backup Sat- meet special guests from NASA! urday evening 13th May ) STEMM Discovery Day This annual event, which runs from Programmable robots called BeeBots, Date: Sunday 7th May 6th – 21st May, celebrates Science, build your own model Earth, and ex- Time: 11:00am to 3:00pm, Technology, Engineering, Mathematics perience a chemical reaction in your and Manufacturing. On the Discovery mouth. WAS will be participating with Venue: Pelorus Trust Sports House, Day, get hands-on with fun activities solar scopes to observe the Sun. See 93 Hutt Park Rd, Lower Hutt and fascinating science experiments. here for more details. Space & Science Festival @Day Daytime event focused on Flying Ma- observing the Sun with solar scopes. Time: 12:00 to 4:00pm, chines, Maths Craft, Engineering with A full programme is available at Venue: Onslow College, Burma Robots & Electronics, Coding, Science S & S Festival Day programme Road, Johnsonville Talks and fun with Physics, Chemistry Tickets are required for this event & Biological sciences. Plus chance to S & S Festival Shop meet special guests from NASA! WAS Date: Saturday 13th May is a part of this event and we will be Space & Science Festival - The Art of Night with Mark Gee Late night event focused on Astropho- Date: Saturday 20th May ton (weather dependent). tography with award winning local Time: 7:00pm, till late Astrophotographer Mark Gee. Regis- ter for event on Facebook here . Venue: Red Rocks Reserve, Welling- Page 4 VOLUME 47 ISSUE 4 WAS Astrophotography Group Location and updates will be posted on skies are cloudy we will meet indoors Date: Saturday 27th May the WAS Astrophotography Group and learn more about processing image Time: 7:00pm Facebook page closer to the time. data. For further details or cancella- tions contact Edward 021_08304802 Venue: See WAS Astrophotography We will aim for a darker location this or Chris 021_ 890222. Group Facebook page. time to try out our new skills. If the WAS Observing Evenings No official Society Observing Evening and near the Southern Cross, the night sky. this month due to our participation in spectacular globular cluster 47 Tu- Date: Every Friday in May (weather the Space & Science Festival., but do canae and the Tarantula Nebula in the permitting) come along on Fridays to the WAS Large Magellanic Cloud (LMC). Jupiter Tawa Observatory and see the many is visible while Saturn rises around Time: 7:00pm, wonderful objects, star clusters, galax- 8pm. Learn how to use the telescope Venue: Tawa College ies, dying stars and nebulae around and how to find these objects in the WAS April Meeting Talks“ Introducing the WAS Research Group” by Roland Idaczyk and “Variable Stars” by Aline Homes In a change to our usual format, we are support, mentoring from more star. As the size increases, the star had not one but two speakers at out experienced members and advice on grows brighter, as it decreases, the April meeting. suitable subjects to pursue. He also star grows dimmer. There are a wide drew attention to the fact that the variety of types, most well-known of First was Roland Idaczyk, who gave a group works with professional astro- such is the Cepheid Variables, whose brief overview of the WAS Research nomical organisations, and that mem- period of variability is directly linked to Group. bers past contributions to research the range in brightness variation. The main purpose of the WAS Re- have been noted in their inclusion as In binary systems, the variation in search Group iis to provide a forum authors for peer-reviewed literature. brightness is not related specifically to for WAS members to share their en- Aline Homes then spoke about varia- the star itself, but to the way it inter- thusiasms for research. At the mo- ble stars, one of the WAS Research acts with any companions. Most stars ment, its main three areas of interest Group main interests. are actually part of a binary system, are occultations, variable stars and and it in some cases, the stars that exoplanets, but it is looking to expand Aline began by explaining variability in a make up the system interact with one into such areas as CCD spectrometry star is defined as significant and meas- another to affect the brightness.
Load more

Recommended publications
  • Equation of Time — Problem in Astronomy M
    This paper was awarded in the II International Competition (1993/94) "First Step to Nobel Prize in Physics" and published in the competition proceedings (Acta Phys. Pol. A 88 Supplement, S-49 (1995)). The paper is reproduced here due to kind agreement of the Editorial Board of "Acta Physica Polonica A". EQUATION OF TIME | PROBLEM IN ASTRONOMY M. Muller¨ Gymnasium M¨unchenstein, Grellingerstrasse 5, 4142 M¨unchenstein, Switzerland Abstract The apparent solar motion is not uniform and the length of a solar day is not constant throughout a year. The difference between apparent solar time and mean (regular) solar time is called the equation of time. Two well-known features of our solar system lie at the basis of the periodic irregularities in the solar motion. The angular velocity of the earth relative to the sun varies periodically in the course of a year. The plane of the orbit of the earth is inclined with respect to the equatorial plane. Therefore, the angular velocity of the relative motion has to be projected from the ecliptic onto the equatorial plane before incorporating it into the measurement of time. The math- ematical expression of the projection factor for ecliptic angular velocities yields an oscillating function with two periods per year. The difference between the extreme values of the equation of time is about half an hour. The response of the equation of time to a variation of its key parameters is analyzed. In order to visualize factors contributing to the equation of time a model has been constructed which accounts for the elliptical orbit of the earth, the periodically changing angular velocity, and the inclined axis of the earth.
    [Show full text]
  • Moon-Earth-Sun: the Oldest Three-Body Problem
    Moon-Earth-Sun: The oldest three-body problem Martin C. Gutzwiller IBM Research Center, Yorktown Heights, New York 10598 The daily motion of the Moon through the sky has many unusual features that a careful observer can discover without the help of instruments. The three different frequencies for the three degrees of freedom have been known very accurately for 3000 years, and the geometric explanation of the Greek astronomers was basically correct. Whereas Kepler’s laws are sufficient for describing the motion of the planets around the Sun, even the most obvious facts about the lunar motion cannot be understood without the gravitational attraction of both the Earth and the Sun. Newton discussed this problem at great length, and with mixed success; it was the only testing ground for his Universal Gravitation. This background for today’s many-body theory is discussed in some detail because all the guiding principles for our understanding can be traced to the earliest developments of astronomy. They are the oldest results of scientific inquiry, and they were the first ones to be confirmed by the great physicist-mathematicians of the 18th century. By a variety of methods, Laplace was able to claim complete agreement of celestial mechanics with the astronomical observations. Lagrange initiated a new trend wherein the mathematical problems of mechanics could all be solved by the same uniform process; canonical transformations eventually won the field. They were used for the first time on a large scale by Delaunay to find the ultimate solution of the lunar problem by perturbing the solution of the two-body Earth-Moon problem.
    [Show full text]
  • 1 the Equatorial Coordinate System
    General Astronomy (29:61) Fall 2013 Lecture 3 Notes , August 30, 2013 1 The Equatorial Coordinate System We can define a coordinate system fixed with respect to the stars. Just like we can specify the latitude and longitude of a place on Earth, we can specify the coordinates of a star relative to a coordinate system fixed with respect to the stars. Look at Figure 1.5 of the textbook for a definition of this coordinate system. The Equatorial Coordinate System is similar in concept to longitude and latitude. • Right Ascension ! longitude. The symbol for Right Ascension is α. The units of Right Ascension are hours, minutes, and seconds, just like time • Declination ! latitude. The symbol for Declination is δ. Declination = 0◦ cor- responds to the Celestial Equator, δ = 90◦ corresponds to the North Celestial Pole. Let's look at the Equatorial Coordinates of some objects you should have seen last night. • Arcturus: RA= 14h16m, Dec= +19◦110 (see Appendix A) • Vega: RA= 18h37m, Dec= +38◦470 (see Appendix A) • Venus: RA= 13h02m, Dec= −6◦370 • Saturn: RA= 14h21m, Dec= −11◦410 −! Hand out SC1 charts. Find these objects on them. Now find the constellation of Orion, and read off the Right Ascension and Decli- nation of the middle star in the belt. Next week in lab, you will have the chance to use the computer program Stellar- ium to display the sky and find coordinates of objects (stars, planets). 1.1 Further Remarks on the Equatorial Coordinate System The Equatorial Coordinate System is fundamentally established by the rotation axis of the Earth.
    [Show full text]
  • Sun-Synchronous Satellites
    Topic: Sun-synchronous Satellites Course: Remote Sensing and GIS (CC-11) M.A. Geography (Sem.-3) By Dr. Md. Nazim Professor, Department of Geography Patna College, Patna University Lecture-3 Concept: Orbits and their Types: Any object that moves around the Earth has an orbit. An orbit is the path that a satellite follows as it revolves round the Earth. The plane in which a satellite always moves is called the orbital plane and the time taken for completing one orbit is called orbital period. Orbit is defined by the following three factors: 1. Shape of the orbit, which can be either circular or elliptical depending upon the eccentricity that gives the shape of the orbit, 2. Altitude of the orbit which remains constant for a circular orbit but changes continuously for an elliptical orbit, and 3. Angle that an orbital plane makes with the equator. Depending upon the angle between the orbital plane and equator, orbits can be categorised into three types - equatorial, inclined and polar orbits. Different orbits serve different purposes. Each has its own advantages and disadvantages. There are several types of orbits: 1. Polar 2. Sunsynchronous and 3. Geosynchronous Field of View (FOV) is the total view angle of the camera, which defines the swath. When a satellite revolves around the Earth, the sensor observes a certain portion of the Earth’s surface. Swath or swath width is the area (strip of land of Earth surface) which a sensor observes during its orbital motion. Swaths vary from one sensor to another but are generally higher for space borne sensors (ranging between tens and hundreds of kilometers wide) in comparison to airborne sensors.
    [Show full text]
  • Positional Astronomy Coordinate Systems
    Positional Astronomy Observational Astronomy 2019 Part 2 Prof. S.C. Trager Coordinate systems We need to know where the astronomical objects we want to study are located in order to study them! We need a system (well, many systems!) to describe the positions of astronomical objects. The Celestial Sphere First we need the concept of the celestial sphere. It would be nice if we knew the distance to every object we’re interested in — but we don’t. And it’s actually unnecessary in order to observe them! The Celestial Sphere Instead, we assume that all astronomical sources are infinitely far away and live on the surface of a sphere at infinite distance. This is the celestial sphere. If we define a coordinate system on this sphere, we know where to point! Furthermore, stars (and galaxies) move with respect to each other. The motion normal to the line of sight — i.e., on the celestial sphere — is called proper motion (which we’ll return to shortly) Astronomical coordinate systems A bit of terminology: great circle: a circle on the surface of a sphere intercepting a plane that intersects the origin of the sphere i.e., any circle on the surface of a sphere that divides that sphere into two equal hemispheres Horizon coordinates A natural coordinate system for an Earth- bound observer is the “horizon” or “Alt-Az” coordinate system The great circle of the horizon projected on the celestial sphere is the equator of this system. Horizon coordinates Altitude (or elevation) is the angle from the horizon up to our object — the zenith, the point directly above the observer, is at +90º Horizon coordinates We need another coordinate: define a great circle perpendicular to the equator (horizon) passing through the zenith and, for convenience, due north This line of constant longitude is called a meridian Horizon coordinates The azimuth is the angle measured along the horizon from north towards east to the great circle that intercepts our object (star) and the zenith.
    [Show full text]
  • The Observational Analemma
    On times and shadows: the observational analemma Alejandro Gangui IAFE/Conicet and Universidad de Buenos Aires, Argentina Cecilia Lastra Instituto de Investigaciones CEFIEC, Universidad de Buenos Aires, Argentina Fernando Karaseur Instituto de Investigaciones CEFIEC, Universidad de Buenos Aires, Argentina The observation that the shadows of objects change during the course of the day and also for a fixed time during a year led curious minds to realize that the Sun could be used as a timekeeper. However, the daily motion of the Sun has some subtleties, for example, with regards to the precise time at which it crosses the meridian near noon. When the Sun is on the meridian, a clock is used to ascertain this time and a vertical stick determines the angle the Sun is above the horizon. These two measurements lead to the construction of a diagram (called an analemma) as an extremely useful resource for the teaching of astronomy. In this paper we report on the construction of this diagram from roughly weekly observations during more than a year. PACS: 01.40.-d, 01.40.ek, 95.10.-a Introduction Since early times, astronomers and makers of sundials have had the concept of a "mean Sun". They imagined a fictitious Sun that would always cross the celestial meridian (which is the arc joining both celestial poles through the observer's zenith) at intervals of exactly 24 hours. This may seem odd to many of us today, as we are all acquainted with the fact that one day -namely, the time it takes the Sun to cross the meridian twice- is in fact 24 hours and there is no need to invent any new Sun.
    [Show full text]
  • Orbital Mechanics Course Notes
    Orbital Mechanics Course Notes David J. Westpfahl Professor of Astrophysics, New Mexico Institute of Mining and Technology March 31, 2011 2 These are notes for a course in orbital mechanics catalogued as Aerospace Engineering 313 at New Mexico Tech and Aerospace Engineering 362 at New Mexico State University. This course uses the text “Fundamentals of Astrodynamics” by R.R. Bate, D. D. Muller, and J. E. White, published by Dover Publications, New York, copyright 1971. The notes do not follow the book exclusively. Additional material is included when I believe that it is needed for clarity, understanding, historical perspective, or personal whim. We will cover the material recommended by the authors for a one-semester course: all of Chapter 1, sections 2.1 to 2.7 and 2.13 to 2.15 of Chapter 2, all of Chapter 3, sections 4.1 to 4.5 of Chapter 4, and as much of Chapters 6, 7, and 8 as time allows. Purpose The purpose of this course is to provide an introduction to orbital me- chanics. Students who complete the course successfully will be prepared to participate in basic space mission planning. By basic mission planning I mean the planning done with closed-form calculations and a calculator. Stu- dents will have to master additional material on numerical orbit calculation before they will be able to participate in detailed mission planning. There is a lot of unfamiliar material to be mastered in this course. This is one field of human endeavor where engineering meets astronomy and ce- lestial mechanics, two fields not usually included in an engineering curricu- lum.
    [Show full text]
  • The Analemma
    The Solar System Division B: Colorado Regional Exam Participants: _________________________ and ________________________________ The Analemma Photo Credit: Dennis di Cicco By this point in your life, you have most likely noticed the Sun slowly and continuously changing its position in the sky throughout the year. The very unusual photo of the Sun was created by exposing a single piece of film a total of forty-five times throughout the course of a year. This “Figure 8” shape, referred to as an analemma, was traditionally included on older globes of the world, positioned directly between latitude +23.5and –23.5. This pattern is a result of the tilt of the ecliptic to the equator and the Earth’s elliptical orbit about the Sun. The course of the Sun during a period of one full year has been plotted onto the grid in Figure 1. The actual dates represented by the dots appear in Table I found on page 3. The vertical, indexed line represents the meridian, an imaginary line stretching from pole to pole crossing directly above the observer’s head. The Earth actually changes speed as it orbits the Sun, whereas clock time remains constant. The values appearing on the horizontal, indexed line at the center reflect the number of minutes the sun is either ahead or lagging behind the time indicated on one’s watch or clock. Unlike the analemma appearing in Figure 1, analemma nearly always include the dates. The Sun’s declination may be estimated for any given day of the year using the analemma as a miniature almanac.
    [Show full text]
  • Solar Analemmaanalemma Bitbit Ofof Administrationadministration ….…
    SolarSolar AnalemmaAnalemma BitBit ofof AdministrationAdministration ….…. •• DiscussionDiscussion SectionsSections – Come directly to the planetarium this week!! •• HomeworkHomework – Can be turned in as late as 4:00 pm Friday at 6515 Sterling •• MathieuMathieu OfficeOffice HoursHours thisthis weekweek – M 1:30 - 3:30, T 3-5, W 11-12 •• ReadingReading – Begin Bless, Chaps. 3-4; BNSV 56-70 •• HonorsHonors StudentsStudents -- turnturn inin schedulesschedules afterafter lecturelecture ConcepTestConcepTest!! If you see a full moon, than A) the moon is above the Earth’s shadow B) the moon is below the Earth’s shadow C) the moon is either above or below the Earth’s shadow D) the moon is about to enter the Earth’s shadow TimingTiming ofof EclipsesEclipses EclipseEclipse TracksTracks BackBack toto SolarSolar Motion,Motion, andand TheThe SeasonsSeasons March 23o December June September Not to scale! On the scale the orbit is drawn Earth would be too small to see, and the Sun would be a tiny dot AltitudeAltitude OfOf SunSun SeasonsSeasons -- SpaceSpace--BasedBased ViewView March June June December September Not to scale! On the scale the orbit is drawn Earth would be too small to see, and the Sun would be a tiny dot ConcepTestConcepTest!! In June the Sun is seen low in the sky at noon from A) Fairbanks B) the Equator C) Santiago D) Since the Earth spins once a day, the Sun is seen at the same height in the sky at noon from everywhere on the Earth SeasonsSeasons -- EarthEarth--BasedBased ViewView Celestial Summer Sun Equator Spring, Fall Sun Winter
    [Show full text]
  • Cataloguing of Objects on High and Intermediate Altitude Orbits
    Cataloguing of Objects on High and Intermediate Altitude Orbits Inauguraldissertation der Philosophisch-naturwissenschaftlichen Fakult¨at der Universit¨atBern vorgelegt von Johannes Herzog von Deutschland Leiter der Arbeit: Prof. Dr. T. Schildknecht Astronomisches Institut der Universit¨atBern Cataloguing of Objects on High and Intermediate Altitude Orbits Inauguraldissertation der Philosophisch-Naturwissenschaftlichen Fakult¨at der Universit¨atBern vorgelegt von Johannes Herzog von Deutschland Leiter der Arbeit: Prof. Dr. T. Schildknecht Astronomisches Institut der Universit¨atBern Von der Philosophisch-Naturwissenschaftlichen Fakult¨atangenommen. Der Dekan: Bern, den 18.11.2013 Prof. Dr. S. Decurtins Contents List of Figures V List of Tables VII List of Abbreviations and Acronyms IX Motivation 1 1 Introduction 5 1.1 Protected Regions and Object Classification . .5 1.1.1 Overview on Objects in geostationary and geosynchronous Orbits . .6 1.1.2 Overview on GNSS Objects . .9 1.2 The Telescope ZimSMART . 11 1.2.1 Mounts . 11 1.2.2 Optical Tube Assemblies . 12 1.2.3 Camera . 13 1.2.4 Analysis of the Performance of the third Set-up of ZimSMART . 13 1.2.5 Observations and Data Format . 14 1.2.6 Limiting Magnitude of ZimSMART and observable Object Sizes . 15 1.2.7 Observable Object Sizes . 16 1.3 Uncertainties of Orbits . 17 1.3.1 Measurement Techniques . 17 1.3.1.1 Optical Observations . 17 1.3.1.2 Satellite Laser Ranging (SLR) . 18 1.3.1.3 RADAR Measurements . 18 1.3.1.4 Position Measurements with the Global Navigation Satellite System (GNSS) 18 1.3.1.5 Microwave Position Measurements . 18 1.3.1.6 Two Line Element Set Analysis .
    [Show full text]
  • P10293v4.0 Lab 3 Text
    Physics 10293 Lab #3: Learning Starry Night, Part 2 Introduction In this lab, we'll learn how to use the Starry Night software to explore the sky, and at the same time, you’ll get a preview of many of the topics that will be covered in lecture and lab this semester. Starry Night has a large number of features and options, and we will learn about some of the most useful ones for our purposes. Continue with Skyguide Once you start the program, if the left sidebar is not already open to the SkyGuide, just type “Skyguide” into the search box in the upper right corner and follow the instructions. We will continue walking through the tutorial to learn more about the features of Starry Night and to learn more about naked eye astronomy that we are covering in lecture. Proceed to the Student Exercises entitled “Unit A: Earth, Moon and Sun,” which are buttons on the main sky guide pane. Answer the associated questions for these exercises on your worksheet for exercises A8 through A13. Unit A: Earth, Moon and Sun In “A8 part 1: Earth’s orbit” Q1. The Earth is closer to the Sun on June 21 and further from the Sun on December 21: True / False Q2. What is the approximate percentage change in the Earth-Sun distance between June 21 and December 21? _____________ percent Q3. Which of the given statements is correct in Question 3 of this section? ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ !17 In “A8 part 2: Earth’s rotation axis” Q4. Which of the given statements is correct in Question 4 for June 21? ________________________________________________________________ ________________________________________________________________ Q5.
    [Show full text]
  • The Analemmatic Sundial What Is This Thing
    The Analemmatic Sundial What is this thing called time really? Time is a very complex concept! Today, we are going to explore the concept of time using the Analemmatic Sundial. The analemma is this skinny figure 8 and is related to the sun’s path across the sky. We will have more to say on the analemma shortly. But let’s pretend that we have no cellphones, no computers, no watches or clocks, no modern timekeeping devices of any kind. How then would we tell the time? Well, first, we would probably divide time in daytime for being awake, working, eating etc. when the sun is in the sky and it is light. Then, we would assign nighttime for sleeping and resting when the sun is not in the sky and it is dark. We would simply divide the day into 12 hours and the night into 12 hours. That would easy, except that the day is longer in the summer and short in the winter while nights are shorter in the summer and longer in the winter. That unbalanced, unequal hours concept is exactly how many agrarian cultures lived for centuries. It really didn’t matter how long the day was as long as you used it effectively! But society changes and becomes more complex and urban. If the king grants you a audience at 10 o’clock, how do you know when 10 o’clock is? Are you even on the same time as the king is keeping? In a more complex society, we had to have a standard system of hours and timekeeping.
    [Show full text]