About the Hong Kong Laureate Forum

Welcome to the September 2021 issue of the newsletter of the Hong Kong Laureate Forum!

The first chapter of the "Prelude to the Inaugural Forum" series (Prelude Events), SCIENCE EXPOSITION, was successfully held on 14-18 September at Xiqu Centre, West Kowloon Cultural District. We are honoured to have distinguished guests attended the opening ceremony to kick-off the event. On the first day of the Life Science and Medicine exhibition, research teams from local universities and science institutes explained their latest projects to and shared their experiences with participants at the exhibition. At the seminar held simultaneously with the exhibition, the outstanding presentations and sharing from four scientist speakers provided insight and knowledge to the audience which included students from secondary schools and universities as well as young scientists. We believe that the participants were inspired from the sharing. The exhibition on the other two scientific disciplines, Astronomy and Mathematical Sciences, will be held at the same venue on 13-16 October 2021. More exciting contents are awaiting you to explore!

The HKLF would like to thank all the research teams for providing such a sublime exhibition and the presentations. Also, we would like to express our gratitude to the guests attending the opening ceremony, who have been providing tremendous support for our preparation of this event as well as the inaugural Forum to be held in Nov 2022.

The second chapter of the series, also our 2021 flagship programme, MASTERMINDS, MASTERCLASSES, will be held on 16-18 November at The Hong Kong Federation of Youth Groups Headquarter. It includes seminars and dialogue sessions hosted by renowned and award-winning scientists around the globe. Prominent scientists who have already accepted our invitations include Prof Jean-Michel BISMUT, 2021 Shaw Laureate in Mathematical Sciences, Prof Pierre Louis LIONS, 1994 Fields Medalists and Prof Dennis Yuk Ming LO, winner of 2021 Breakthrough Prize in Life Sciences and 2021 Royal Medal. The HKLF would like to take this opportunity to congratulate Prof Dennis LO for being awarded the Royal Medal 2021 in biological sciences. Prof Lo is the first Chinese scientist ever to receive the Medal in the biological sciences category since the establishment of the award 200 years ago. Stay tuned to our website and social media for more information on the Prelude to the Inaugural Forum.

More scientific events are on the horizon! In addition to the Prelude Events organised by the HKLF, InnoCarnival 2021 organised by the Innovation and Technology Commission will be held on 23-31 October at Hong Kong Science Park. The HKLF will be one of the participating organisations among more than 30 exhibition and game booths. We are pleased to be collaborating with the Consulate General of France in Hong Kong and Macau in this event. A unique virtual reality (VR) experience coined "I Will Sleep When I’m Dead" produced by French artist, Ms Jeanne SUSPLUGAS, will be staged at our booth. In the VR experience, participants will dive into a headful of neurons and synapses, get lost in an infinite labyrinth and cross "thoughts" illustrated by drawings looking like pictograms. Besides the VR experience, more games and exciting prizes are awaiting participants at the HKLF booth! Visit InnoCarnival’s website to find out more and visit our booth at InnoCarnival 2021.

Hong Kong Meridian (II) - In Search of the Magic Stones

In the previous issue, we learned that to meet the needs of ocean navigation, the British invented the marine chronometer to help captains accurately ascertain the longitude of the ship to ensure safe navigation. In spite of the high accuracy of the marine chronometers, they needed to be calibrated regularly, and this came to depend on a time service provided by major ports.

How does the Observatory measure time?

The HKO shoulders this important responsibility in Hong Kong. At the time of its establishment in 1883, its main purpose was to determine "local time" through astronomical observations using a transit instrument. Simply put, the moment when the sun passes directly to the north or south of a location is local noon. This is the basic principle of the sundial, and the time measured is called "apparent solar time". However, apparent solar time is not uniform because the Earth's orbit is not circular and its revolution speed varies with its distance from the Sun. There is also an effect due to the tilt of the earth's rotation axis. Therefore, a more uniform time called mean solar time was introduced. For example, "Greenwich Mean Time" that we are quite familiar with is the mean solar time of the longitude of the Airy Transit Circle (the longitude of the "Prime Meridian" mentioned in the previous issue) at the Royal Observatory at Greenwich. Similarly, the time service provided by the HKO during its early years was based on the mean solar time of the longitude of the Observatory's transit instrument, i.e., what this article will focus on ─ the Hong Kong Meridian.


Mr SHUN Chi-ming, Former Director of the Hong Kong Observatory

Seeing the Inside World through Inverse Problems

What is an inverse problem?

In many problems in science and technology, we are able to collect measurements and are interested in inferring useful information about the system, say certain physical parameters that can cause the effect (the measurements). Such a problem is termed an inverse problem because it starts with the effects and then calculates the causes. It is the inverse of a forward problem, which starts with the causes and then calculates the effects. Inverse problems can tell us about parameters that we cannot observe directly. They have many applications in system identification, optics, radar, acoustics, communication theory, signal processing, medical imaging, geophysics, oceanography, astronomy, remote sensing, non-destructive testing, and many other fields. To be more concrete, in what follows, we will embark on the road to demystify a particular inverse problem: The X-ray computerised tomography.

The story of X-ray radiography

Our journey begins in 1895 when German physicist Wilhelm Rontgen was experimenting with Crookes tubes. He discovered that some invisible rays coming from the tube were able to pass through black cardboard that visible light could not. He referred to the radiation as "X" to indicate that it was an unknown type of radiation. He immediately realised their potential use in medical application when he made a picture of his wife's hand on a photographic plate. This was the first photograph of a human body part using X-rays. Rontgen received the first Nobel Prize in Physics for the discovery.

Nowadays X-rays radiographs (also called projection radiography, or conventional radiography) are routinely used to screen for pneumonia, bone fractures, cancer and vascular disease. It is also used in our fight against the COVID-19. The mechanism is that when the X-ray beam passes through the patient body, it is attenuated due to the scattering and absorption in the body. Therefore, one can infer valuable information about the body inside from their transmission, typically registered on a film-screen detector. In a naive way, we may think of a projection radiograph as a 2-D shadow cast by a semi-transparent 3-D body illuminated by X-rays.


Prof ZHANG Hai, Associate Professor, Department of Mathematics, The Hong Kong University of Science and Technology

Aerogel – An Air-Based Material and Its Exciting Properties

In 1931, an American chemical engineer, Dr Samuel Stephens KISTLER bet his colleague, Dr Charles LEARNED, that they could replace the liquid inside a jelly with gas without shrinking it. Dubbing this concept "aerogel", they managed to make the first aerogel with silica. Afterwards, other materials, such as alumina, cellulose, egg albumin, rubber and agar, were also used to produce aerogels. Do you know how aerogel is made? Let’s discover more about the science of aerogel and its wide range of applications, thanks to its density and thermal insulating properties.

How to Make Aerogel

In order to understand how aerogel is produced, we first need to understand the structure of jelly – yes, the chewy, sweet jelly that everyone loves. Imagine cooking jelly in your kitchen, there are three main ingredients you need: jelly powder, water and sugar. In this case, sugar can be taken out of the equation because it provides only the sweet taste. The resulting jelly, which is 95% water with a small amount of porous solid support, is defined as one of the hydrogel structures. To make aerogel, you want to replace the water in hydrogel with air.

Swapping water for air in hydrogel sounds simple, but it’s actually very complex. If you simply vaporise the liquid by heating the jelly, it shrinks as its solid network collapses due to capillary action caused by the attractive forces between the liquid molecules. Imagine when solvent molecules constantly vaporise from the gel, the intermolecular forces between the remaining liquid molecules keep pulling the molecules together to fill the vacancy produced in order to maintain the density of the gel. This also induces an inward stress on the delicate network of the gel, causing the network to collapse and shrink.


Student Editor, Science Focus
The Hong Kong University of Science and Technology