B71 #82: Coriolis effect

During our re-union gathering on December 28, 2008, the subject of Coriolis effect was raised and discussed. It leads to the following finding:

a) that the Earth's Coriolis effect (an effect of differential surface velocity) is theoretically true (see Part 1).

b) that the Earth's Coriolis effect is hard to demonstrate as it requires a large bath/pool 2 yards across, to drain through a pin-hole for 12-15 minutes before the effect can be seen (see Part 2).

c) that we can emulate the Coriolis effect by rotating a half globe on a platform (see Part 3).

I would await some interested parties to assemble an experimental unit.


///// Part 1: Explanation of Coriolis effect /////

Blog version:


Website version:
http://hk.youtube.com/watch?v=mcPs_OdQOYU






///// Part 2; The lack of good demonstration kit /////

Website discussing the difficulty of setting up an Ideal Sink experiment:
http://www.thenakedscientists.com/HTML/content/interviews/interview/470/

Can You Detect The Coriolis Effect in your Sink?
Dr Karl Kruszelnicki, University of Sydney, Australia

Chris - What we've been doing this evening is asking people all around the East of England to fill sinks and baths with water, pull out the plug and see which way the water swirls down the plug hole. We've got a mixture of results this evening, but is this experiment actually possible? Can we detect the spinning of the Earth using this approach?

Karl - You can get it to work. However, you're looking at a thing called the Coriolis force, which is actually angular momentum under a different name. The Coriolis force on the small bodies of water you're working on is roughly 10 million times smaller than the gravity force, so you really need to do the experiments delicately. Let's just back up a bit here. The thing about angular momentum is the same as when ice skaters go faster when they pull their hands into their body. They speed up because they bring more of their mass to the spin axis of the body. If you think about the Earth spinning, at the equator it's a long way from the spin axis, and at the poles it's right on the spin axis. If you get a storm brewing just above the equator, they spin and move away from the equator towards the poles. As they do so, they head towards the spin axis of the Earth. There's a bit of angular momentum that needs to be accounted for. If you do the equations, this leads to clockwise rotation of a hurricane in the southern hemisphere and anticlockwise rotation in the northern hemisphere. But here you're looking at something tens or hundreds of kilometres across. How can you hope to see that same effect in a tiny tub? The answer is that if you do the experiment very carefully, you should be able to see it. This has been done once or twice.

Chris - So it is possible?

Karl - Yes. In a fine journal called Nature in 1962, there was a paper by Shapiro who did the experiment at MIT. A few years later at the University of Sydney, also published in Nature, a paper by Trefethen in 1964 about the bath tub vortex in the Southern hemisphere. What you do is get a special bath tub, which is two yards across, six inches deep and has a tiny tiny central hole. You put a cork there so you can see which way the water's going. You let the water settle for a day or two so you lose all the residual spin from putting it in there and then you open the drain plug. The water begins to flow out very slowly and nothing very significant happens for about twelve to fifteen minutes. At around that stage, you can begin to see the cork take on a clockwise or anticlockwise rotation depending on your hemisphere. It happens slowly at first and then increases to one rotation every four seconds by the end. Shapiro wrote that when all the precautions prescribed were taken, the vortex was invariably in the anti clockwise direction. Soif you're a fair way away from the equator and you it carefully, you can see it. However if you just rush off the plane at Singapore which is one degree from the equator, and the surface of the Earth is about parallel to the spin axis, put some water in an oval bowl and pull the plug straight out, you're only going to see local effects.

Chris - So in other words, Michael Palin was fooled into thinking this was true at the equator.

Karl - Mate, there's an old Polish saying. If you've got a dog, don't bark. It's fairly obscure, but what it means is stick to your speciality. The number of areas of ignorance we have are huge. In this particular case in the TV series Pole to Pole, Michael Plain meets a man called Michael McCleary, who says that this line here on the ground is the equator. He has a little square tub which he's holding in his hands with floating matchsticks. He then walks off in one direction and spins as he turns around to face the tourists. That gives a spin to the water. He takes his finger off the bottom and you can see the matchsticks going round clockwise or anti clockwise as he's being told. Poor Mr Palin is being conned!

Chris - It just goes to show that even the great Michael Palin can be conned sometimes. Thanks very much for joining us Dr Karl and helping us to avoid throwing out the baby with the bath water and debunking the myth of the Coriolis effect and how it effects spin when water goes down the plug hole.

December 2005




///// Part 3 Suggested demonstration kit /////

I would suggest to use a rotating platform to rotate a double-layer half globe on a cylindrical upright pillar, with the following set-up.

Set-up 1: Pin-ball experiment

1a) While the platform is rotating from west to east, shoot a pin-ball from the equator to the north pole along the zero meridian. We predict that it would deflect to the right. If there are three holes at the 45 degree latitude, namely one at the zeroth meridian, one on the right and one on the left, the pin ball would "fall" into the right hole.

1b) If a pin-ball is shot from the north pole along the zero meridian to the equator, it will "fall" into the left hole.

1c) If similar arrangement is mounted on the cylindrical part, both balls will "fall" into the zeroth meridian hole.

1d) If we reverse the rotation of the platform from east to west, in the half globe, the ball shot from the equator will fall into the left hole and the ball shot from the north pole will fall into the right hole (different from (a) and (b)). In the cylindrical column, all balls will fall into the zeroth meridian hole (same as in (c)).

Set up 2: Air suction

2a) In the inner globe of the double layer, punch four holes:
(i) a hole at the north pole,
(ii) a hole in the equator at the zeroth meridian,
(iii) a hole in the 45 degrees north latitude and the 45 degrees east longitude,
(iv) a hole in the 45 degrees north latitude and the 45 degrees west longitude.
2b) If we punch punch a hole in the outer globe of the double-layer at the position of zeroth meridian and 45 degrees north latitude, air will be centrifuged out of the globe while the globe rotates. We can put sensors around the hole for detecting air current.

2c) Instead of punching a hole in the outer globe, we shall punch a hole in the inner globe at the same position (zeroth meridian and 45 degrees north latitude), and use a pump to pump air out of the double-layer there. The sensors in (b) will detect the current flow, which according to Coriolis effect should be in counter-clockwise direction.

2d) If we install similar things on the cylindrical column as a control experiment, the air flow direction may not form a pattern.

2e) If we reverse the direction of the rotation, we would expect the air flow in (c) will be in clockwise direction. Again, the control experiment installed in the cylindrical column will not display a clear pattern.

Set up 3: Water flow

3a) Mount two water reservoirs at the equator (called them the left and right side of heart), linked with pipe to enable water flow in-between.

3b) Mount two water reservoir at the north pole (called them the left and right side of the cerebrum), again linked with pipe to enable water to flow in-between

3c) Use a rubber tube (right tube) to connect the water outlet at the right heart to the water inlet at the right celebrum.

3d) Use a rubber tube (left tube) to connect the water outlet at the left celebrum to the water inlet at the left hear.

3e) Use a pump to pump water from the right heart upwards. Water would flow upward along the right tube to the right celebrum, then to the left cerebrum, fall down along the left tube to the left heart and return to the right heart to complete the circulation.

3f) As the globe rotates from west to east, the right tube will bulge to the right, and the left tube will bulge to the left, leaving a hollow for the anti-clocwise cyclone to form, as predicted by the Coriolis effect.

3g) Suggest to clamp the rubber tubes in place, activate the pump to circulate the water, then rotate the globe. When condition stabilizes, release the clamp and observe how the rubber tubes will bend. For better effect, install sensors to detect the bending of the rubber tubes. One form of sensor is to use florescent water and transparent rubber tubes, so that we can observe the bending of the rubber tubes without having to stop the globe from rotating.

3h) If we change the direction of the rotation, we would expect that rubber tubes to bend towards each other instead of bulging out.

3i) The control experiment installed at the side of the cylinder would not display the bending effect.

3j) To demonstrate the effect side by side, we may install similar water inlet and outlets at the 180 degrees meridian with water pumped up along the left rubber tube and water returning downward along the right rubber tube. It is predicted that the opposite effect of (3f) and (3h) would be observed.

Set up 4: Further improvement

4a) It may be desirable to divide the the globe and the cylinder into 4 compartments, two for the water pipes, one for the pin-ball and one for air flow.

4b) It may also be desirable to change the half globe design to a pyramid design (with a square base) to house the 4 compartments.

4c) It may also be desirable to build two units, one rotating from west to east (to emulate the northern hemisphere), and the other rotating from east to west (to emulate the southern hemisphere). If successful, this will explain everything in one go.

B71 #81: Terence Tao

Message from David Yau:

Again，余等同窗子裔又添榮顯，眾 Uncles & Aunties 與有榮焉，除對梁同學蕙蘭衷心道賀，懇請冼同學永生把此佳訊上 Blog，以公告天下！

美國最聰明青年科學家 華裔陶哲軒位居榜首

26/11/2008

美國《探索》（Discover）雜誌選出二十名四十歲以下美國最聰明的科學家（20 Best Brains Under 40），其中排首位的數學家和排第十位的電子生物工程師都是華裔科學精英。

排首位的 33 歲華裔數學家陶哲軒（Terence Tao）智商高達 220，在澳洲出生，他 8 歲參加美國高考學術評估測驗（SAT）數學科獲得 760 分的高分，只差 40 分就滿分（在美國，十七八歲的學生中只有 1% 能夠達到 750 分，而 8 歲的孩子裏面還沒有人超過 700 分），24 歲更成為加州大學洛杉磯分校史上最年輕的數學教授，前年獲得「菲爾茨獎」（Fields Medal），這是一項專為四十歲以下傑出科學家頒發的「數學界諾貝爾獎」。會說粵語但是不懂書寫中文的陶哲軒，在有關壓縮感知方面的研究，可以應用在磁力共振、天文以及數碼相機等成像技術上。

最聰明科學家排第十位的是 36 歲的楊長輝（Changhuei Yang），目前任職加州理工學院電子工程與生物工程師。目前主力研究製作廉價耐用、方便攜帶的「超小顯微鏡」，他希望將來可更多應用在發展中國家，方便醫生驗血和檢驗水質。

Source: http://discovermagazine.com/2008/dec/20-best-brains-under-40

Appendix

1. A complimentary quote:

"Terry is like Mozart -- except without Mozart's personality problems," said John Garnett, professor and former chair of mathematics in the UCLA College. "Mathematics just flows out of him." "Mathematicians with Terry's abilities appear only once in a generation," said Garnett. "He's probably the best mathematician in the world right now. Terry can unravel an enormously complicated mathematical problem and reduce it to something very simple. We're amazingly lucky to have him at UCLA."

2. A video spotlight on Terry Tao:

http://www.youtube.com/v/E6Qy5qkOjxk

*

B71 #80: Reunion trip to HKU

BSc 71
Reunion Activities on 2008.11.07 - visit to HKU and Reunion Dinner at the Graduate House

Report from Grace Ho:

I have enjoyed a great afternoon visiting various Science Departments in HKU and a good dinner at the Graduate House on November 7, 2008. The visits to the Eliot Hall and the Lily Pond have brought back a lot of sweet memories.

It was wonderful to meet over twenty classmates, some of them I have not met for decades, such as Cheung Foon Hung, as well as Wu Kam Chu who has returned from Canada and Leung Wing Hong from New Zealand for the special occasion.

For those who could not manage to join the reunion activities, I hope the photos allow you to have a taste of the happy atmosphere that we have shared.

Grace

Photo 1: The Eliot Hall



Photo 2: Briefing by Prof. A. Cheung












Photo 3: BSc 71 Reunion HKU visit participants



Photo 4: The Telescope












Photo 5: On the way to Eliot hall





Photo 6: Inside Eliot Hall 1




Photo 7: Inside Eliot Hall 2

















Photo 8: Outside Eliot Hall




Photo 9: What's left of the Lily Pond












Photo 10: By the Lily Pond




Photo 11 Girls by Dr Sun Yat-sen's Statue












Photo 12 Inside the Greenhouse



Photo 13: Talk in the Geological Museum












Photo 14: Visiting the Geological Museum




Photo 15: Reunion Dinner in Graduate House 1












Photo 16: Reunion Dinner in Graduate House 2




Photo 17: Reunion Dinner in Graduate House 3












Photo 18: Group photo in Graduate House












Names of classmates in Group Photo in Graduate House

From left to right:

Back row: Gilbert Wong, Anthony Wu, Kevin Ko, Leung Sze Chung, Lam Chiu Ying, David Yau, Wu Kam Chu, David Yam, Cheung Foon Hung, Philip Chow, Henry Leung, Raymond Choi, Wu Dick Kin, Leung Wing Kwong, Lam Hung Biu

Front Row: Edward Sin, Tse Tsun Him, Clara Chan, Grace Lee, So Man Wan, Lo Mun Ling, So Ting Kwong.

B71 #79: Reunion trip to Chiangmai

BSc71 Reunion Trip to Chiangmai in Thailand November 8-12, 2008


Report from Grace Ho:

Ten of us, under the leadership of Lam Chiu Ying made a trip to Chiang Mai 8-12/11/2008. We went bird-watching, star-gazing, sightseeing and hiking. We visited the Royal Project Botanical Gardens and sampled food cooked with vegetables grown and chicken or pork from pigs raised by the Royal Project. We visited villages with ethnic people and enjoyed a very interesting elephant show at the Maesa Elephant Camp.

Weather was excellent and the sceneries very beautiful. It was a fantastic trip with excellent company. I would like to thank Chiu Ying and Man Wan for their superb organization and help to make the trip such a great success!

Grace

Photo 1: Dinner in Chiangmai




Photo 2: Doi Pui











Photo 3: Doi Pui Summit



Photo 4: Lunch in Village












Photo 5: Royal Project Greenhouse 1



Photo 6: Royal Project Greenhouse 2











Photo 7: Royal Project Garden




Photo 8: Shopping in market












Photo 9: Chiu Ying Having Fun




Photo 10: Raymond getting ready

B71 #78: Dinner on December 28, 2008

To celebrate our 40th anniversary since entry to HKU, we have a part 2 dinner scheduled on December 28, 2008.

Lilian Kwan has kindly arranged her secretary to book the City University Shing Hin Restaurant (on the 9th Floor of City Top) for our gathering as well as for Lily Yeung's art exhibit.

Dinner starts at 8 pm. Lilian (9261-5601) will be there to await your arrival from 6:30 pm onwards.

Hope you can join.

Participation (family members are welcome)
* Lily Yeung + son, Edmund Lam
* Grace Leung + husband, Billy Tao
* Judy Chu
*
* Stephen Lam
* Chan Hing Chung
* Henry Leung
* Lam Chiu Ying
* So Man Wan
*
* Edward Sin
* Clara Chan
* David Yau
* Cheung Foon Hung
* Leung Wing Kwong
*
* Robert Lam
* David Yam Yee Kwan
* Lilian Kwan (left before dinner)
*


Here is a list of photo albums contributed by classmates

David Yau's album:
http://www.esnips.com/web/BScReunionDinner-20081228

Stephen Lam's album:
http://picasaweb.google.com/pendulam/281208DinnerPhotos?authkey=x5ZcEO3MY-k&feat=email

Lily Yeung's album:
http://picasaweb.google.com/lilyuetminglam/AGoldenMoment?authkey=CjoSEI04zY4#

Clara Chan's album:
http://picasaweb.google.com/lh/sredir?uname=cfungchan&target=PHOTO&id=5285244595679121538&aid=5285244103738736241&authkey=hA7GNVjK-HU&feat=email


Group Photo:



Standing Row (from left)
David Yau Man Tak
Chan Hing Chung
David Yam Yee Kwan
Henry Leung Wing Hong
Edward Sin Wing Sang
Robert Lam Hung Piu
Cheung Foon Hung
Leung Wing Kwong


Sitting Row (from left)
Lam Chiu Ying and So Man Wan
Grace Leung Wai Lan and Billy Tao
Lily Yeung Yuet Ming
Clara Chan Chiou Min
Judy Chu Wah Yuk and Stephen Lam Ka Tat

B71 #77: Photos of Re-union (from Clara Chan)

You are invited to view a photo from Clara's photo album:
BSc 71 - HKU Tour (相識四十載)

http://picasaweb.google.com/cfungchan/BSc71HKUTour?authkey=Imt73tE5Jag#5265933125581305090

Message from Clara:

I enclose some photos taken at today's tour around HKU. Can you tell the buildings?

I can assure you that there are lots and lots of buildings. There is so much concrete that the place bears little resemblance to the good old campus where we spent some of our best years.

B71 #76: Photos of Re-union on November 7, 2008

Photo taken with the telescope in the Physics Building

Photo of 3-Dimension slide show in the Earth Science Museum

B71 #75: Precious Photos (from Wu Dick Kin)

B71 #74: Precious Photos (from Grace Ho)