All the waves of the ocean
By Lionel Philippoz, Team Leader IPhO 2015 and Member of the Academic Committee IPhO 2016
A few days have passed since our olympic adventures on the Indian subcontinent have come to an end, and we gradually start again with our daily business in Switzerland. However, this doesn't prevent us of remembering our stay in Mumbai.
As usual, our concentration, resistance as well as diplomatic abilities were put to the test during the discussions of the examinations or their subsequent moderation, when the leaders need to defend the performances of their students against the local markers. Some rest periods were hopefully scheduled, letting us some time to visit the surroundings. This is why I decided to enjoy a peaceful afternoon between two sessions, walking along the coast and dreaming in front of the ocean offering turbulent motions to my eyes.
This vast animated surface immediately made me think of gravitational waves propagating in our space-time. At your interrogating stare, I imagine that most of you aren't familiar with the content of Einstein's general relativity from which those concepts are taken, and wonder how a simple image of a wild ocean can be related to such abstract topics about our universe. In order to help you get a glimpse of the situation, let me give you another analogy.
Imagine a tablecloth made of an elastic fabric. If nothing lies on its surface, the tablecloth simply remains flat. Understandable. But if one now puts a marble on it, it will push the tablecloth down, allowing a depression to form; the more massive the marble is, the more important the deformation will be. This is exactly what happens in general relativity: the presence of a mass or energy (our marble) curves and deforms the space-time (our tablecloth); the more massive the body is, the more important will be the curvature. Isn't it intuitive? And gravitational waves can as well be explained in a simple way: when one accelerates the marble (mass), the tablecloth (space-time) will start to vibrate and perturbations (gravitational waves) will propagate on its surface.
In reality, the amplitude of the generated waves is very weak, and if we hope to directly detect them one day, we need to consider larger systems for which the typical dimensions go beyond the common intuition. As for instance two neutron stars orbiting around one another (what one calls a binary system); the density of such a star doesn't relate to anything known on Earth. Try to imagine: compressing our Sun into a sphere with a radius of only 10 km would result in a neutron star! There are of course much denser systems, such as a neutron star orbiting around a black hole, or two black holes, or even more exotic sources, but that is another story...
The next time you will be facing a water surface, you will perhaps think of other waves than those moving in front of you...
Zurich, 17 July 2015
Tuk-tuk, honk-honk, wheeze-wheeze
By Marco Gerber, Manager Hospitality and Events IPhO 2016
I set off for India with a somewhat romanticized view of what I would find there, not knowing that the lasting impression left by a few documentaries and art-house films about rural or British Colonial India was a false one. I had imagined the streets of India to be teeming with people – and cows of course – as well as endless cars, motorcycles and, above all, cycle rickshaws. However, the present has caught up with the latter, human-powered modes of transport, and virtually all of them have been replaced by loud autorickshaws, otherwise known as tuk-tuks. And there were a lot fewer cows than I had expected, too.
There is no way of avoiding these motorized rickshaws in India, as thousands of them navigate through the often congested city streets. Being small enables them to force their way through standing and crawling lanes of traffic, even if this means having to make some somewhat death-defying maneuvers. And, by the way, they are not controlled by a steering wheel but by handlebars. However, the popularity enjoyed by tuk-tuks definitely has to do with the fact that they can transport their customers a lot more cheaply than traditional taxis. At least when their charming (male) drivers – you hardly see any women at the "wheel" – switch on their meters, which they often leave off when driving naive tourists around so as to increase their margins with "slightly" inflated prices. But people should really have caught on to this by now.
Although the three-wheeled contraptions might look funny, they can honk as loudly as bigger vehicles. Not that this makes any difference amid the constant honking in a traffic jam. The tuk-tuk's onomatopoeic name coincidentally comes from the typical noise made by its two-stroke diesel motor.
But it is these very motors and the absence of catalytic converters that are slowly bringing tuk-tuks in India into disrepute for ecological reasons. A Delhi court has forced tuk-tuk owners to switch to natural gas after the city's record of having the world's highest particulate pollution recently attracted negative press. Mumbai, in turn, banned the noise- and air-polluting vehicles completely from the southern-most part of the city, which is mainly of major importance for its financial and tourist industry.
It's kind of a pity. But who knows, perhaps tomorrow's engineers and physicists will come up with some innovative ideas and new, more environmentally friendly propulsion systems that will save the tuk-tuks from going the same way as the cycle rickshaws – i.e. being caught up by reality and disappearing altogether.
Mumbai, 13 July 2015
Laser light, the sun, extremum principles and nuclear reactors
By Daniel Oehry, Leader of the Liechtenstein delegation
The IPhO in Mumbai is the fifth Olympiad in which I've taken part as the leader of the Liechtenstein team. It's always really exciting when the experiments and theoretical tasks are presented. Partly because the way in which the tasks are presented and the discussion is led speaks volumes about the people involved and of course also because of the physics. We've now completed the tasks, so I can tell you a bit about them.
As 2015 is being celebrated as the Year of Light, the experimental section was about the diffraction of laser light. In one of the experiments, a laser beam was directed at a very small feather. Various parameters of the feather (wire thickness, angle of elevation, wire spacing) could be determined very precisely from the resulting diffraction pattern. The particularly interesting thing about this experiment is that a similar set-up – but using x-rays instead of a laser beam – enabled Rosalind Franklin to prove the double helix structure of DNS in 1953.
In my experience, the theoretical tasks are less clear and a great deal of mathematics was needed for the required calculations. I have to say, however, that I really liked the three Indian tasks.
The first task focused on the sun and its physics. Among other things, we had to do calculations about the temperature of the sun, both inside and outside. Additionally, there were sub-tasks that examined the question of "how" the sun shines and how we can actually know that, although we are 150 million kilometres away.
The second task involved the extremum principle in physics. This principle states that many processes run in such a way that a specific size becomes as small as possible. For example, light always takes the shortest possible route given the time it needs. This task involved physics from the 17th to the 20th century, and from mechanics to optics and quantum mechanics.
India is a country that relies on nuclear energy. The last task involved designing a nuclear reactor that is operated with fuel rods from naturally occurring uranium dioxide and heavy water as a moderator. We were able to calculate that this kind of reactor is around six meters in diameter and in height, and needs about 100 metric tons of fuel.
At the start, I mentioned that the way in which the tasks were presented also spoke volumes about the people who devised them. I found the Indian physicists very convincing in this respect. In our discussions, they showed that they were really ready to deal with critical feedback and to look for the best possible solution. You could tell that a lot of effort and expertise went into preparing the tasks.
Mumbai, 10 July 2015
Monsoon or benevolent Indra
By Andrea Schneider, General Manager, IPhO 2016
"July is the main monsoon season in the Mumbai region. So don't forget to pack waterproof shoes and a raincoat. We'll provide you with an umbrella," the organizers of the IPhO 2015 told us.
The monsoon is strongest in the Indian Ocean, where its name also comes from. Because of the high humidity they bring with them, monsoons have a significant effect on the natural environment and are of great economic and cultural importance.
Not surprisingly, few tourists can be found in India during the monsoon season. Initiatives like Romancing the Monsoon attempt to draw attention to the advantages of travelling in that season. "Travel to one a perfect getaway to savour the magic of rain," as the headline in one magazine put it. The article below read, "Monsoons in India are a rhapsody of bliss, beauty and relief from the scorching summer sun." Recommended regions include Goa, Kerala and even Maharashtra, in which Mumbai lies.
We therefore braced ourselves for the worst: day after day of incessant rain, flooded streets and improvised clothes lines to dry drenched clothes in our bathrooms.
The reality was very different. During the nine days of the conference, participants experienced no more than a handful of brief showers, none of which lasted more than a few minutes. Could it be that Indra took pity on the organizers?
Indra is an early Indian Vedic deity who, together with the fire god Agni and wind god Vayu, forms the Vedic holy trinity – loosely comparable to the three main deities of modern-day Hinduism: the creator Brahma, the sustainer Vishnu and Shiva, the renewer.
In the Vedic religion, Indra is presented as the supreme warrior god of the heavens, the god of thunderstorms and rain, fertility and creation. He is the god the Vedas worship and sing about most frequently. The weapon of this king of the gods is a lightning rod. Indra lives in a palace on the tip of Mount Meru, from where he rules over the warriors' paradise in the clouds, similar to the Norse Valhalla. Indra's parents are the Heavens and the Earth, which Indra divided from one another for all eternity immediately after his birth.
And so, in the name of the organizers and all participants, I would like to thank Indra for his benevolence. Unforgettable moments awaited us in a place called Maximum City. And because we didn't have to hold an umbrella we had our hands free to take pictures.
Want to know whether you stay drier if you run or walk through the rain? Minute Physics knows more.
Minute Physics - is it better to walk or to run in the rain?
Mumbai, 13 July 2015
(Picture: Andreas Schilling)
The physicist's beautiful clothes
By Andreas Schilling, President of the Academic Committee of the International Physics Olympiad (IPhO) 2016
I'm taking part in the Physics Olympiad for the first time, and only in the comfortable position of observer.
The participants are all future students, among them many potential doctoral students or professors of physics. The leaders and observers are also predominantly physicists.
As a professor, I often attend big conferences with physics researchers and so I was amazed (or maybe not) that the IPhO does indeed have a lot in common with these conferences.
They mainly take place in prominent hotels catering to an international audience, not uncommonly several flying hours away from Zurich.
The distinguishing feature of a physics conference (and I see for the IPhO too) is the attitude of physicists towards clothing. The more luxurious the venue (and the selected hotels in Mumbai are just that), the greater the difference between the physicists participating at the conference and the other guests who often cross paths in the spacious hotel and conference facilities.
You recognise the physicists immediately from the sandals, training or hiking shoes, the colourful mixture of garments with the sole purpose of covering the body and regulating the skin temperature to a bearable degree.
And striking contrasts often crop up to the other guests, who stay in such places for relaxation or business. For them, clothing has the function of being elegant and well-groomed, with a style either consistent with an elevated lifestyle or success in business.
These attributes do not appear in any physical formulae and so are probably foreign to most physicists. The encounter of these two cultures can be amusing; here the baggy look, if you’ll allow me the expression, and there bespoke elegance.
In a nutshell: the IPhO confirmed to me that here there really are young talented people on the right track to become "real physicists" and to cultivate the tradition of our dress philosophy.
Mumbai, 11th July 2015
Ode to the air-conditioning system
By Simon Birrer, Co-Chairman IPhO 2016
The IPhO statutes stipulate that the prepared theoretical and experimental tasks are endorsed by the International Board. The International Board comprises 180 Leaders from about 90 countries who gather in a room to listen to the introductions and discussions on the prepared tasks, either confirming their correctness or raising any questions or making improvement suggestions which are then discussed in the plenary. Once endorsed, the examination tasks are translated into 50 languages, corresponding to the participants' respective national languages. This phase of examination endorsement and translation is of great importance and serves as the basis for the written assignment for the participating pupils.
In order that no errors occur in the assessment and translation of the examinations, temperature regulation in the congress facilities is of key importance, as it is well known that people soon lose mental performance and concentration at temperatures above 25° Celsius.
Let's work it out: In total, over 200 leaders and observers sit in the same room. Each person generates around 200 Watts of power. Thinking and brain performance make up a high proportion. This means that the combined heat output of all attendees is around 40,000 Watts. So an air-conditioning system needs at least this output to keep the temperature constant.
If the air-conditioning system were to go down, how quickly would the room heat up?
Here we need some more information about the room. The room is sufficiently large (approx. 50 x 30 metres) with a high ceiling (approx. 5 metres). The mass of the air is around 1 kg/m^3, which equates to roughly 100,000 kg of air mass in this room. The specific heat of the air, i.e. the amount of energy to heat 1 kg air mass by one degree Celsius, is around 1,000 joules.
This means that the room would heat up by one degree in just a few minutes, merely through the presence of the those present. And working without cooling would no longer be possible within an hour.
So we were very pleased that there was a reliably operating air conditioning, even though the leaders in the front third complained of cool temperatures and those in the back third of high temperatures.
Opening the windows to cool the room wouldn't help - the outside temperatures in the monsoon season here in Mumbai are currently around 30° - day and night - with high humidity.
Mumbai, 7th July 2015
Buoyed by the Burj Khalifa en route to the IPhO in Mumbai
By Thomas Uehlinger, Head of the Academic Committee IPhO 2016
It's now getting serious – I am on my way to the International Physics Olympiad, which will be held this year in Mumbai. As members of the Organization Committee and Academic Committee at next year's Olympiad in Zurich, this is our last opportunity to gain valuable first-hand experience of how the event is organized in other countries.
While travelling to Mumbai, I spent two days in Dubai, which is a city of contrasts. On the one hand there are the souks hidden away in narrow streets, symbolizing an age-old tradition of trade, while on the other you have the world of finance, shopping and entertainment, which has been created in the desert in a remarkably short space of time.
As a physicist, I was particularly fascinated by the Burj Khalifa skyscraper. At a height of 828 meters, it is the tallest man-made structure in the world, while its unladen weight of 500,000 tonnes is equally impressive.
The amount of force acting on the building foundation is quite incredible. This consists of a 3.7 meter-thick plate of reinforced concrete, which is anchored in the ground with 192 columns, each over 50 meters long. However, the gravitational force was not the greatest challenge faced by the building's planners. Far more difficult to deal with are the wind loads, which vary dynamically and can cause the building to oscillate: in strong winds, the uppermost levels of the tower can sway back and forth by up to two meters. If the timing of the oscillation coincides with the so-called resonant frequency of the structure, it can have serious consequences, i.e. a resonance disaster. Such a disaster led to the collapse of the Tacoma Narrows bridge in the USA in 1940.
So what can building designers do to tackle this problem? In the case of the Burj Khalifa, an irregular design was chosen, as can be seen clearly in the picture. This prevents the building from having a single resonant frequency, as well as a wider excitation spectrum, thereby drastically reducing its susceptibility to any potentially fatal oscillation-based effects. At the same time, the irregular design minimizes its susceptibility to oscillation by suppressing regularly occurring air vortexes.
For Taipei 101, the second highest skyscraper in the world, a different strategy was chosen, whereby a 'tuned mass damper' was fitted. In the case of Taipei 101, this is a 730-ton steel sphere that hangs between the 88th and 92nd floors in the building's interior. The sphere acts as a pendulum, absorbing the oscillations and reducing the skyscraper's movement by around 40%. This is particularly important due to the very high likelihood of earthquakes in Taipei.
Mumbai, 6th July 2015