Transit of Venus Teacher Training Secondary School Session - History and Science

教師培訓班 Teacher Training Workshop

時間 地點 活動

09:00 演講廳

登記,派發教材套,入場

09:00 – 09:10 簡介

09:10 – 10:30 講座一 (香港大學理學院科學導師 張師良先生)

1. 介紹金星凌日

2. 觀測金星凌日的歷史及其對科學的重要性

講座二

(可觀自然教育中心暨天文館 許浩強先生)

1. 觀測活動介紹

觀測太陽安全要點

觀測金星凌日的要點

基本記錄、繪圖及攝影

2. 製作

a. 針孔投影盒(連製作)

b. 太陽濾鏡眼鏡製作

c. 雙筒鏡濾鏡製作

分享

陳樹渠紀念中學 黃炳思老師

港島民生書院 梁達榮老師

聖母書院 梁振聲老師

10:30 – 10:40 小休

時間 地點 活動

10:40 – 11:50

(分5組)

月明泉

(下雨時，於黃麗松講堂)

分組實際觀測示範

A. 使用望遠鏡

a. 投影法

b. 目視觀測(使用濾鏡，包

括望遠鏡及雙筒望遠鏡)

B. 針孔投影盒

C. 太陽投影儀及太陽望遠鏡

D. 太陽漏斗/太陽槍及雙筒

望遠鏡投影

E. 攝影紀錄

11:50-12:00 演講廳

總結及問答

填問卷

培訓班目的： • 理解及體會金星凌日天象的重要

• 簡單介紹金星凌日背後的原理

• 學校能夠如何及怎樣舉辦活動

• 在技術層面如何觀測金星凌日

• 探討支援方案

5月21日日環食 香港可見 : 日出至 07:16 環食: 06:07 – 06:10

Two coming historical events

5月期間 日落時間可見金星

月球

金星

木星

Simulations by Stellarium

www.stellarium.org

Credit: Stairways to the Stars, Anthony Aveni

• Position of

Venus night

after night at

sunrise

• Symbols at 2

week intervals

The pre-dawn Venus

East

The rising Sun

Credit: Stairways to the Stars, Anthony Aveni

The Dresden Codex : a Maya picture book produced in northern Yucatan about the 11th century

http://www.famsi.org/mayawriting/codices/dresden.html

• Venus in a Maya sacred book. The five-page Venus Table on pages 46-50 of the Dresden Codex showing pictures of the Venus god flinging arrows and his events, dates, intervals, directions, and resulting omens.

• The Maya had a unique calendar system based on Venus

Credit: Tunç Tezel

Path of Venus relative to the Sun

from April 3rd through August 7th, 2004 (top right to bottom left)

The Sun

morning star

evening star

凌日階段 時間 太陽方向/方位角/仰角

Ⅰ 凌始外切 6時11分 東北偏東/068°/6°

Ⅱ 凌始內切 6時29分 東北偏東/069°/10°

凌甚 9時31分 西北偏西/081°/51°

Ⅲ 凌終內切 12時31分 西北偏西/278°/88°

Ⅳ 凌終外切 12時48分 西北偏西/274°/84°

日出 5時37分 東北偏東/065°/0°

2012年6月6日 金星凌日

不按比例

注意選擇適當的觀測地點

正確的合理期望

Transit of Venus happened since the invention of telescope

• 1631 December 7 • 1639 December 4

• 1761 June 6 • 1769 June 4

• 1874 December 9 • 1882 December 6

• 2004 June 8 • 2012 June 6

• 2117 December 11

Last chance in your life!

122 years

105 years

122 years

105 years

軌道周期: 金星 224日 地球 365日

Orbital configuration of Venus and Earth

Kepler’s laws of planetary motion

• Law of ellipses – the orbit of a planet about the

sun

is an ellipse with the sun at one focus

• Law of equal areas – a line joining a planet and the

sun

sweeps out equal areas in equal

intervals of time

• Law of harmonies – the square of a planet’s sidereal

period around the sun is directly

proportional to the cube of the length

of its orbit’s semi-major axis, a

a

Average distances of planets from the Sun (In AU)

Copernicus Kepler 20th Century

Mercury 0.3763 0.389 0.387

Venus 0.7193 0.724 0.723

Earth 1.0000 1.000 1.000

Mars 1.5198 1.523 1.524

Jupiter 5.2192 5.200 5.202

Saturn 9.1743 9.510 9.539

• 1AU is the Sun-Earth distance

• Relative distance between planets known to good accuracy even during Kepler’s time

• Absolute scale of the solar system (i.e., exactly how long is 1 AU?) remains unknown

• Ptolemy, Copernicus and Tycho, they all assumed 1AU = 1200 times the radius of the Earth

• Kepler guessed 1AU = 3500 times the radius of the Earth

• They lacked observational instruments and methods to test their guess

The early days

Method 1 – a smarter(?) guess

• Measure the apparent size of a planet with a telescope

• Assume a physical size of the planet

• Distance to the planet can be obtained from the ratio of physical size to the apparent angular size

It is practically accessible, but theoretically no better than pure guess

Method 2 – triangulation (parallax)

• If a planet is observed simultaneously by two observers separated by large distances, then the apparent position of the planet among the background stars would be slightly different.

• If we know the separation of the two observers, the distance to the planet can be calculated.

• Difficulties: measure of the separation, the longitude problem, small angle, synchronization of the clocks

It is prefect in theory, but difficult to execute 21

Sketch of the 1761 transit as seen by Nicholas Ypey.

1874 北京 - James Craig Watson

Parallax 視差

Angular size VS real size

1. Observing the different apparent paths of Venus across the face of the Sun seen from different widely spaced latitudes

2. Measuring the rate (angular velocity) at which Venus crosses the face of the Sun. The rate is the vector sum of the orbital angular velocity of Venus and the Earth and the angular velocity of the observing site due to the Earth’s daily rotation.

3. Comparing the absolute times of Venus’s contact with the Sun’s limb, seen from different places on Earth (Delisle’s method).

4. Comparing the total time for Venus to cross the Sun as seen from different latitudes, which depends on both the curvature of the Sun’s limb and the distance moved by the observer due to the Earth’s rotation (Halley’s method).

4 ways of calibrating AU using ToV

31

32

d1 = (d1 + d2) sin θ

A new size of the solar system

• From the transit of Venus on June 3, 1769, the AU was measured to 10% accuracy.

• The size of the solar system turned out to be 100 times larger than Ptolemy’s estimate.

• Once the absolute scale (AU) is fixed, then the size and distances to the planets can be determined.

• The physical size of the solar system is finally known.

Estimates of the size of Earth's orbit, A.D. 100 - 1769

Coming of Age in the Milky Way, Timothy Ferris 34

1 AU = 149,598,000 kilometers

講座系列

第一講：金星凌日的科學與歷史 日期：2012年5月13日(星期日) 講者：張師良先生（香港大學理學院科學導師）

時間：下午3時-4時30分 地點：香港太空館演講廳

第二講：金星凌日及日環食現象及觀測 日期：2012年5月20日(星期日) 講者：余惠俊先生（香港天文學會外務副會長）

第三講：金星 日期：2012年5月27日(星期日) 講者：張師良先生（香港大學理學院科學導師）

第四講：太陽系外的凌日現象 日期：2012年6月2日(星期六) 講者：李文愷博士（香港大學物理系副教授）

警告： 太陽觀測活動必須注意安全

不正確觀測太陽會導致永久失明

智能手機 計時 apps

6月6日觀測活動 • 尖沙咀星光大道 • 06:00 - 13:00

• 小型觀測站在網頁公佈

• 網上直播

www.facebook.com/transitofvenushk transitofvenus.hk hk.space.museum roadshow.science.hku.hk