Shipping’s Black Cloud

Over summer Dr Edward Duca visited the beautiful Island of Gozo, meeting Prof. Ray Ellul and his team based in Xewkija and the Giordan Lighthouse. Gozo is a tourist hotspot because of its beautiful landscapes, churches, and natural beauty. These same reasons attracted Ellul to obtain baseline readings of air pollutants; human effects should be minimal. Their equipment told them a different story.

They’re very big, anything from 10,000 tonnes to 100,000 tonnes,’ atmospheric physicist Prof. Ray Ellul is telling me about the 30,000 large ships his team observed passing between Malta and Sicily over a year. This shipping superhighway sees one third of the world’s traffic pass by carrying goods from Asia to Europe and back.

M/T "XANTHIA" - Yard no. 108  by: AKER AUKRA AS - AKER YARDS

The problem could be massive. ‘A typical 50,000 tonner will have an engine equivalent to 85 MW,’ Malta’s two electricity plants churn out nearly 600 MW. You only need a few of these to rival the Islands’ power stations.

Ellul continues, ‘this is far far worse. We are right in the middle of it and with winds from the northwest we get the benefit of everything.’ Northwest winds blow 70% of the time over Malta and Gozo, which means that around two thirds of the time the pollutants streaming out of these ships are travelling over Malta. Even in Gozo, where traffic is less intense, air quality is being affected.

“Ships currently use heavy fuel oil with 3.5% sulfur; this needs to go down to at least 0.5%. The problem is that it doubles cost”

Malta is dependent on shipping. Malta’s Flag has the largest registered tonnage of ships in Europe; shipping brings in millions for Malta. We cannot afford to divert 30,000 ships to another sea. Yet Malta is part of the EU and our politicians could ‘go to Brussels with the data and say we need to ensure that shipping switches to cleaner fuels when passing through the Mediterranean.’ Politicians would also need to go to the Arab League to strike a deal with North Africa. Ships currently use heavy fuel oil with 3.5% sulfur; this needs to go down to at least 0.5%. The problem is that it doubles the costs. Malta’s battle at home and abroad won’t be easy, but the Baltic Sea has already taken these measures.

German Dreams

The research station in Gozo is a full-fledged Global Atmospheric Watch station with a team of five behind it. Now it can monitor a whole swathe of pollutants but its beginning was much more humble, built on the efforts of Ellul, who was drawn into studying the atmosphere in the 80s when he shifted his career from chemistry to physics.

In the early 90s the late rector, Rev. Prof. Peter Serracino Inglott, wanted the University to start building some form of research projects. ‘At that time, we knew absolutely nothing about what was wrong with Maltese air and Mediterranean pollution,’ explained Ellul. Building a fully fledged monitoring station seemed to be the key, so Ellul sent ‘handwritten letters with postage stamps’ to the Max Planck Institute in Mainz. Nobel prize winner Paul J. Crutzen wrote back inviting him to spend a year’s sabbatical in Germany, but their help didn’t stop there. ‘He helped us set-up the first measuring station, [to analyse the pollutants] ozone, then sulphur dioxide, then carbon monoxide. That’s the system we had in 1996 — […] 2 or 3 instruments.’

They lived off German generosity until 2008 when Malta started tapping into EU money. After some ERDF money and an Italy-Malta project on Etna called VAMOS SEGURO (see Etna, THINK issue 06, pg. 40), Ellul now manages a team of five. In homage to his early German supporters he has structured the research team around a Max Planck model — ‘one of the best systems in the World for science’.

Paradise Lost?

lloyds-register-logo

Getting data about ships is not easy. ‘It is very sensitive information and there is a lot of secrecy behind it,’ explains Ing. Francelle Azzopardi, a Ph.D. student in Ellul’s team. It is also very expensive. Lloyd’s is the World’s ship registry that tracks all ships, knowing their size, location, engine type, fuel used — basically a researcher’s dream. However, they charge tens of thousands. Ellul took the decision that they gather all the data themselves.

After 2004, all international ships above 300 gross tons need to have a tracking device. Automatically, these ships are traced around the world and anyone can have a peek on www.marinetraffic.com (just check the traffic around Malta). Every half hour the team’s administrator Miriam Azzopardi saves the data then integrates it into the Gozitan database. This answers the questions: where was this ship? which ship was it? how big is it? Easy.

“Ship emission expert James Corbett calculates that worldwide around around 60,000 people die every year due to ship emissions”

co2-emission

If only! The problem is that the researchers also need to know fuel type, engine size, pollution reduction measures, and so on. Then they would know which ship is where, how many pollutants are being emitted, and how many are reaching Malta and Gozo. To get over this hurdle, they contacted Transport Malta (more than once) to ask for the information they needed. ‘About 50% of the ships passing there [by us or Suez are] Malta registered,’ explained Ellul. With this information in hand they could put two and two together. They could create a model for ship emissions close to the Islands and use the model to get the bigger picture.

Enter their final problem: how do you model it? Enter the Finns. Ing. Francelle Azzopardi travelled to the Finnish Meterological Institute. They had already modeled the Baltic Sea, now they wanted access to the Maltese data, in return the Maltese team wanted access to their model called STEAM.

STEAM is a very advanced model. It gathers all the ships’ properties like engine power, fuel type, and ship size. This is combined with its operating environment including speed, friction, wave action, and so on. STEAM then spits out where the team should be seeing the highest pollution indicators. Malta was surrounded.

Apart from the model, the team have seen a clear link between ships and pollution. At the Giordan lighthouse they can measure a whole host of pollutants sulphur dioxide, various nitrogen oxides, particulate matter, black and brown carbon levels, ozone, radioactivity levels, heavy metals, Persistent Organic Pollutants (POPs) and more. When the wind blows from the Northwest, they regularly show peaks of sulfur dioxide, nitrogen oxides, carbon dioxide, carbon monoxide, hydrocarbons which are all indicative of fossil fuel burning either from ships or Sicilian industry. They also picked up relatively high levels of heavy metals especially Vanadium, a heavy metal pollutant. Such metals are more common in heavy fuel oil used by ships.

shipping4

Alexander Smyth is the team’s research officer who spends three months in Paris every year analysing filters that capture pollutants from the atmosphere. Two different filter types are placed in the Giordan Lighthouse. One filter for particles smaller than 2.5 micrometers and another filter for particles around 2 to 10 microns. ‘With the 2.5 filter we can see anthropogenic emissions or ship emissions because they tend to be the smaller particles. The filters are exposed for three to four days, and then they need to be stored in the fridge. Afterwards, I take them to Paris and conduct an array of analyses,’ continued Alexander. The most worrying pollutant he saw was Vanadium.

Vanadium is a toxic metal. When inhaled, ‘it can penetrate to the alveoli of the lungs and cause cancer, a worst case scenario,’ outlined Alexander. It can also cause respiratory and developmental problems — none are good news. The only good news is that ‘they are in very small amounts’. Quantity is very important for toxicity, and they are seeing nanograms per cubic metre, a couple of orders of magnitude more are needed to cause serious problems. No huge alarm bells need to be raised, although Vanadium does stick around in bones and these effects still need more studies.

Vanadium seems to be coming from both Malta and shipping traffic. ‘The highest peaks of vanadium are from the south [of Malta, but the largest number of times I detected came] from the northwest, [from ships],’ said Smyth. ‘There is a larger influence from ships compared to local pollution at the Giordan lighthouse.’

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Vanadium is not the only pollutant that could be affecting the health of Maltese citizens. Smyth also saw lots of different Persistent Organic Pollutants (POPs). At low concentrations these compounds can affect immunity leading to more disease, at higher concentrations they can lead to cancer. The local researchers still need to figure out their effect on Malta’s health. Francelle Azzopardi also saw peaks of sulfur dioxide and nitrogen oxides. No surprise here as shipping is thought to cause up to a third of the World’s nitrogen oxides and a tenth of the sulfur dioxide pollution.

Inhaling high levels of sulfur dioxide leads to many problems. It is associated with respiratory disease, preterm births, and at very high levels, death. It can affect plants and other animals. Nitrogen oxides also cause respiratory disease, but can also cause headaches, reduce appetite, and worsen heart disease leading to death. These are pollutants that we want to keep as low as possible.

Ship emission expert James Corbett (University of Delaware) calculates that worldwide around 60,000 people die every year due to ship emissions. Most deaths come from the coastlines of Europe, East Asia, and South Asia. Shipping causes around 4% of climate change emissions. This is set to double by 2050. In major ports, shipping can be the main cause of air pollution on land.

Another unexpected pollutant was ozone, normally formed when oxygen reacts with light. Yet the Giordan lighthouse was not the first to start measuring this gas. It all started with the Jesuits, scholarly catholic monks.

Monks at work

A lot of time is needed to see changes in our atmosphere. Researchers need to gather data over years. To speed up the process, Ellul was hunting around Malta and Gozo for ancient meteorological data about the Islands’ past atmosphere.

He was tipped off that there were still some records at a seminary in Gozo. ‘We expected to find just meteorological data and instead we also found ozone data as well. It was a complete surprise and a stroke of very good luck. We were able to find out what happened to ozone levels in the Mediterranean over the last hundred years.’

Jesuit monks meticulously measured ozone levels from 1884 to 1900. They analysed them seeing that the concentration of ozone was a mere 8 to 12 parts per billion by volume, ppbv. Ellul compared these to a 10-year study he conducted from 1997 to 2006. ‘We measure around 50ppb on average throughout the year,’ which is nearly 5 times more over a mere 100 years.

The situation is quite bad for Malta. In the past, the minimum was in summer and the maximum in winter and spring. Now, this has reversed with spring and summer having the highest ozone levels because of the reactions between hydrocarbons and nitrogen oxides. These come from cars, industry, and ships.

Over the Eastern Mediterranean ozone levels have gradually decreased. Over Malta, in the Central Mediterranean, they remained the same. Ellul thinks this could be because of an anticyclone over the central Mediterranean bringing pollutants from Europe over Malta and Gozo. The levels of ozone in Malta and Gozo are the highest in Europe, and it could be mostly Europe’s fault. Our excessive traffic doesn’t help.

Ozone can be quite a mean pollutant. While stratospheric ozone blocks out harmful UV rays, low-level ozone can directly damage our health or react with other pollutants to create toxic smog. It’s been known to start harming humans at levels greater than 50 ppbv. It inflames airways causing difficulty breathing, coughing and great discomfort. Some research has linked it to heart attacks — a pollutant not to be taken lightly.

Over those 10 years Ellul and his team saw 20 episodes in summer where ozone levels exceeded 90 ppbv. Some were during the night, unlikely to be of local origin but due to transport phenomena in the central Mediterranean and shipping. Ellul does nod towards the possibility of air recirculation from Malta. The atmosphere is a complicated creature.

Plants also suffer from ozone. Above 40 ppbv yield from fields decreases. Gozo is definitely being affected; we could be producing more.

The devil is in the details

Ellul and his team have found a potentially big contributor to the Islands’ pollution. This would be over and above our obvious traffic problem. Yet Ellul admits that ‘there is no particular trend, it’s too short a time span. What it tells us is that what we think is a clean atmosphere is not really a clean atmosphere at all. The levels are significant.’ Azzopardi honestly says ‘I can [only] give you an idea of what is happening’.

The team needs to study the problem for longer. It needs some statistics. Clearly they see a link between ships passing by Malta and peaks in pollution levels, but the Islands need to know if shipping pollution levels beat industry, traffic, or Saharan dust. What is ships’ contribution to Malta’s health problems?

When the team knows the extent of pollution, they can see whether they go above European standards. Ozone already does, and likely to be due to pollution from the European continent. If they can extend it to a whole host of other pollutants that skyrocket above European standards due to ship traffic, then ‘our politicians,’ says Ellul, can go to Brussels to enforce new legislation. That could control Mediterranean shipping traffic to clean up our air. At least it would solve one significant problem that Malta cannot solve on its own.

The main problem is economic. A ship can be made greener by reducing its sulfur fuel content. Low sulfur fuels are double the price of the bunker fuel they currently use. New legislation would need enforcement, which is costly. Ships could also be upgraded, again at a price. Passing these laws is not going to be easy.

Ships have been a pollution black hole for a while. The fuels ships burn contains 3,000 times more sulfur than cars are allowed to burn. Quite unfair. Going back to Corbett’s figures estimating European deaths at 27,000, the current rise in shipping pollution could end up killing hundreds of thousands if not millions before new legislation is enforced. Now that would be truly unfair.

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Kelma Kelma

cassi-camilleri

With a massive following of 25,000 people, Kelma Kelma is the Facebook page that has taken Malta by storm. From a simple collection of linguistic curiosities borne from one man’s love of the Maltese language, it has developed to become an unconventional but highly effective teaching tool. This is the journey of Kelma Kelma from the man behind the computer screen, Dr Michael Spagnol.

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Maltish or Engtese

Stick to one language! Was the old maxim. Otherwise, you’ll risk confusing your kids and they will never learn to speak properly. Research by Prof. Helen Grech and her team shows that this is not true: bilinguals usually do better. Teaching your child two languages at a go might delay them initially but helps them in the long run.  Words by Dr Edward Duca.

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An Intelligent Pill

carlazzopardi
Doctors regularly need to use endoscopes to take a peek inside patients and see what is wrong. Their current tools are pretty uncomfortable. Biomedical engineer Ing. Carl Azzopardi writes about a new technology that would involve just swallowing a capsule.

Michael* lay anxiously in his bed, looking up at his hospital room ceiling. ‘Any minute now’, he thought, as he nervously awaited his parents and doctor to return. Michael had been suffering from abdominal pain and cramps for quite some time. The doctors could not figure it out through simple examinations. He could not take it any more. His parents had taken him to a gut specialist, a gastroenterologist, who after asking a few questions, had simply suggested an ‘endoscopy’ to examine what is wrong. Being new to this, Michael had immediately gone home to look it up. The search results did not thrill him.

The word ‘endoscope’ derives from the Greek words ‘endo’, inside, and ‘scope’, to view. Simply put, looking inside  our body using instruments called endoscopes. In 1804, Phillip Bozzini created the first such device. The Lichtleiter, or light conductor, used hollow tubes to reflect light from a candle (or sunlight) onto bodily openings — rudimentary.

Modern endoscopes are light years ahead. Constructed out of sleek, black polyurethane elastometers, they are made up of a flexible ‘tube’ with a camera at the tip. The tubes are flexible to let them wind through our internal piping, optical fibers shine light inside our bodies, and since the instrument is hollow it allows forceps or other instruments to work during the procedure. Two of the more common types of flexible endoscopes used nowadays are called gastroscopes and colonoscopes. These are used to examine your stomach and colon. As expected, they are inserted through your mouth or rectum.

Michael was not comforted by such advancements. He was not enticed by the idea of having a flexible tube passed through his mouth or colon. The door suddenly opened. Michael jerked his head towards the entrance to see his smiling parents enter. Accompanying them was his doctor holding a small capsule. As he handed it over to Michael, he explained what he was about to give him.

Enter capsule endoscopy. Invented in 2000 by an Israeli company, the procedure is simple. The patient just needs to swallow a small capsule. That is it. The patient can go home, the capsule does all the work automatically.

The capsule is equipped with a miniature camera, a battery, and some LEDs. It starts to travel through the patient’s gut. While on its journey it snaps around four to thirty-five images every second. Then it transmits these wirelessly to a receiver strapped around the patient’s waist. Eventually the patient passes out the capsule and on his or her next visit to the hospital, the doctor can download all the images saved on the receiver.

The capsule sounds like simplicity itself. No black tubes going down patients’ internal organs, no anxiety. Unfortunately, the capsule is not perfect.

“The patient just needs to swallow a small capsule. That is it. The patient can go home, the capsule does all the work automatically”

Autumn 2013 Magazine Master.inddFirst of all, capsule endoscopy cannot replace flexible endoscopes. The doctors can only use the capsules to diagnose a patient. They can see the pictures and figure out what is wrong, but the capsule has no forceps that allow samples to be taken for analysis in a lab. Flexible endoscopes can also have cauterising probes passed through their hollow channels, which can use heat to burn off dangerous growths. The capsule has no such means. The above features make gastroscopies and colonoscopies the ‘gold standard’ for examining the gut. One glaring limitation remains: flexible endoscopes cannot reach the small intestine, which lies squarely in the middle between the stomach and colon. Capsule endoscopy can examine this part of the digestive tract.

A second issue with capsules is that they cannot be driven around. Capsules have no motors. They tend to go along for the ride with your own bodily movements. The capsule could be pointing in the wrong direction and miss a cancerous growth. So, the next generation of capsules are equipped with two cameras. This minimises the problem but does not solve it completely.

The physical size of the pill makes these limitations hard to overcome. Engineers are finding it tricky to include mechanisms for sampling, treatment, or motion control. On the other hand, solutions to a third problem do exist. This difficulty relates to too much information. The capsule captures around 432,000 images over the 8 hours it snaps away. The doctor then needs to go through nearly all of these images to spot the problematic few. A daunting task that uses up a lot of time, increasing costs, and makes it easier to miss signs of disease.

A smart solution lies in looking at image content. Not all images are useful. A large majority are snapshots of the stomach uselessly churning away, or else of the colon, far down from the site of interest. Doctors usually use capsule endoscopy to check out the small intestine. Medical imaging techniques come in handy at this point to distinguish between the different organs. Over the last year, the Centre for Biomedical Cybernetics (University of Malta) has carried out collaborative research with Cardiff University and Saint James Hospital to develop software which gives doctors just what they need.

Following some discussions between these clinicians and engineers they quickly realised that images of the stomach and large intestine were mostly useless for capsule endoscopes.

Identifying the boundaries of the small intestines and extracting just these images would simplify and speed up screening. The doctor would just look at these images, discarding the rest.

Engineers Carl Azzopardi, Kenneth Camilleri, and Yulia Hicks developed a computer algorithm that could first and foremost tell the difference between digestive organs. An algorithm is a bit of code that performs a specific task, like calculating employees’ paychecks. In this case, the custom program developed uses image-processing techniques to examine certain features of each image, such as colour and texture, and then uses these to determine which organ the capsule is in.

Take colours for instance. The stomach has a largely pinkish hue, the small intestine leans towards yellowish tones, while the colon (unsurprisingly perhaps) changes into a murky green. Such differences can be used to classify the different organs. Additionally, to quickly sort through thousands of images, the images need to be compacted. A specific histogram is used to amplify differences in colour and compress the information. These procedures make it easier and quicker for algorithm image processing.

Texture is another unique organ quality. The small intestine is covered with small finger-like projections called villi. The projections increase the surface area of the organ, improving nutrient absorption into the blood stream. These villi give a particular ‘velvet-like’ texture to the images, and this texture can be singled out using a technique called Local Binary Patterns. This works by comparing each pixel’s intensity to its neighbours’, to determine whether these are larger or smaller in value than its own. For each pixel, a final number is then worked out which gauges whether an edge is present or not (see image).

Classification is the last and most important step in the whole process. At this point the software needs to decide if an image is part of the stomach, small intestine, or large intestine. To help automatically identify images, the program is trained to link the factors described above with the different organ types by being shown a small subset of images. This data is known as the training set. Once trained, the software can then automatically classify new images from different patients on its own. The software developed by the biomedical engineers was tested first by classification based just on colours or texture, then testing both features together. Factoring both in gave the best results.

“The software is still at the research stage. That research needs to be turned into a software package for a hospital’s day-to-day examinations” 

Dr Yulia Hicks
Dr Yulia Hicks

Prof. Ing. Kenneth Camilleri
Prof. Ing. Kenneth Camilleri

After the images have been labeled, the algorithm can draw the boundaries between digestive organs. With the boundaries in place, the specialist can focus on the small intestine. At the press of a button countless hours and cash are saved.

 

The software is still at the research stage. That research needs to eventually be turned into a software package for a hospital’s day-to-day examinations. In the future, the algorithm could possibly be inserted directly onto the capsule. An intelligent capsule would be born creating a recording process capable of adapting to the needs of the doctor. It would show them just what they want to see.

Ideally the doctor would have it even easier with the software highlighting diseased areas automatically. The researchers at the University of Malta want to start automatically detecting abnormal conditions and pathologies within the digestive tract. For the specialist, it cannot get better than this.

The result? A shorter and more efficient screening process that could turn capsule endoscopy into an easily accessible and routine examination. Shorter specialist screening times would bring down costs in the private sector and lessen the burden on public health systems. Michael would not need to worry any longer; he’d just pop a pill.

* Michael is a fictitious character

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The author thanks Prof. Thomas Attard and Joe Garzia. The research work is funded by the Strategic Educational Pathways Scholarship (Malta). The scholarship is part-financed by the European Union — European Social Fund (ESF) under Operational Programme II — Cohesion Policy  2007–2013, ‘Empowering People for More Jobs and a Better Quality of Life’

Diabetes: from genes to blood

Alexandra Fiott
Alexandra Fiott

Type 2 diabetes mellitus is a disease that affects over 250 million people worldwide. Many in Malta suffer from the disease because of our high carbohydrate diet and lack of physical activity. Type 2 diabetes arises when levels of the sugar glucose remain very high in the blood. Testing normally involves frequent finger pricks to determine blood sugar levels, or otherwise a patient can take a sugary drink followed by regular urine/blood testing over 2 or more hours.

Alexandra Fiott (supervised by Prof. A. Felice) studied whether the absolute HbA1c levels (the haemoglobin fraction with sugar attached multiplied by the haemoglobin concentration) would provide a better method to describe the link between one’s genetics and diabetic condition. She attempted to reduce the frequency of the testing needed while using a relatively non-invasive test — the withdrawing of one tube of blood, while investigating the genetics of diabetes.

Haemoglobin (Hb) transports oxygen throughout the blood through red blood cells. The HbA1c forms when glucose binds to haemoglobin. This can be used as an indirect measure of average blood sugar concentrations. Measuring HbA1c levels is rapid, but unfortunately the results are influenced by factors that affect red blood cells. With around 5% of Maltese having red blood cell disorders, an alternative measurement would help reduce inaccurate results and unnecessary worry for patients. The absolute HbA1c was used for this study.

The genetics and blood profile of five different patient groups were determined using genetic and biochemical methods: adults with a normal blood profile, anaemics, beta-thalassaemics, pregnant women, and type 2 diabetics (on limited treatment). Statistical analysis did not reveal an improved link, but the absolute HbA1c did help distinguish between the different patient groups.

To improve the reliability of these results, a separate set of experiments was carried out to see whether a known Maltese variation in haemoglobin, with a prevalence of around 1.8% in the Maltese population, has an effect on the amount of sugar that binds to the haemoglobin. This variant was found not to influence the blood glucose levels and therefore the HbA1c.

Taken together these results showed that the absolute HbA1c does not improve the link between the genetics and blood profile of the patients. However, it could distinguish between different groups of patients.

 

This research was performed as part of an M.Sc. (Melit.) in Biomedical Sciences at the Faculty of Medicine and Surgery at the University of Malta.

Does Alcohol kill brain cells?

This myth is HUGE! Urban legend says that drinking kills cells, some even say: ‘three beers kill 10,000 brain cells.’ Thankfully, they are wrong.

In microbiology labs, a 70% alcohol 30% water mix is used to clean surfaces pretty efficiently. It seems our neurons are made of sturdier stuff.

Alcohol does affect brain cells. Everyone knows that and it isn’t pretty. Alcohol can damage dendrites, which are delicate neural extensions that usually convey signals to other neurons. Damaging them prevents information travelling from one neuron to another — a problem. Luckily, the damage isn’t permanent.

The Einstein Enigma

We experience gravity everyday, but how it works is one of the biggest questions in physics. Einstein’s theory of relativity means that we don’t understand over 90% of the Universe. A team at the University of Malta is trying to put that in order.

I do not know what I may appear to the world, but to myself I seem to have been only like a boy playing on the seashore’, said the famous Isaac Newton. Humanity has progressed in its search for answers by always searching for the next smooth pebble, the next pretty shell. In Malta, a small group of students is trying to understand gravity through the observation of stars and galaxies that light up the night sky.

Gravity has kept our feet on the ground since we started walking upright. Early theories by the Greek philosopher Aristotle (384–322 bc) were interesting but far from the truth. His Universe was built in concentric spheres with Earth at the centre, followed by water, air, fire, and enclosed by the heavens — a rock fell to the Earth because it wanted to go to its original sphere. Clearly, he was wrong.

Aristotle’s concepts were challenged during the Renaissance when the Italian Galileo Galilei (1564–1642 ad) infamously dropped different weights from the tower of Pisa. Contrary to the Greek theory which stated that the heavier an object is, the faster it falls, Galileo saw the objects all fall at the same rate. Theories need to match observations, otherwise they fail — an invaluable technique used time and again by any decent scientist including the Malta group of astrophysicists led by Dr Kris Zarb Adami.

“Space is a dynamic entity ‘moving forward in time, the two being bound by light itself”

The first person to suggest a good theory for why rocks fall was Isaac Newton (1643–1727 ad). As the story goes, watching an apple fall triggered Sir Isaac Newton to come up with his theory of bodies. He said that anything with mass had a force that attracted everything towards it — the bigger the mass, the bigger the force. Since the apple is smaller than the Earth, it falls towards it, and since the Earth is smaller than the Sun, the Earth goes around the Sun. Newton’s law was successfully used to predict the motion of planets and helped discover Neptune.

A star burning out
A star burning out

By the 20th century, holes in Newton’s ideas started to appear when scientists discovered that Mercury’s orbit differed slightly from Newtonian predictions. In 1915, along came Einstein (1879–1955 ad) who again revolutionised our understanding of gravity through the introduction of his theory of general relativity. Newton had considered time and our three-dimensional space to be independent. Einstein replaced this with the notion of spacetime, which combines space and time into one continuous surface. Space is a dynamic entity ‘moving forward’ in time, the two being bound by light itself.

Large objects like the Sun bend the fabric of spacetime (it is convenient to think of spacetime as a sheet of fabric with balls lying on top of it — bigger balls curve the fabric more). Smaller objects (such as the Earth) try to follow the shortest route around the Sun. The shortest way is curved and it is easy to see how this comes about.

How the mass of the earth bends spacetime and satellites go around the earth
How the mass of the earth bends spacetime and satellites orbit the earth

Consider the shortest route from the North Pole to the South Pole, you would naturally move down a curved longitude, which forms part of a circle round the Earth. This concept also explains why the Earth traces an orbit round the Sun. The orbit is the ‘best straight line’ that Earth can trace 

in the curved spacetime surrounding the Sun. As John Archibald Wheeler neatly summarises it: ‘Spacetime tells matter how to move, matter tells spacetime how to curve’.

Einstein’s biggest blunder

Einstein’s theory of general relativity describes how gravity works. Einstein wanted his equations to represent a static Universe that did not change with time. To this end, he introduced a factor called the cosmological constant that would bring the Universe to a halt. However, this idea was short-lived. Another great (though highly egotistical) physicist called Edwin Hubble discovered that the Universe was expanding; this was confirmed in the late nineties and led to a Nobel Prize in 2011. It not only means that all matter will eventually disperse throughout the Universe and future generations will see only a blank night sky, but also poses a problem in that the reason for this expansion is completely unknown and unpredicted from Einstein’s theory. And it is not a small factor at all, since this mysterious energy makes up 68% of the energy in the Universe. Nicknamed ‘dark energy’ because it is unseen, this is the biggest problem in modern astrophysics and cosmology.

“If a star’s light is being bent by a galaxy, from Earth it will appear that the star’s light has changed, when in reality it would not have changed at all”

 

Scientists either have to accept that dark energy is true, or that Einstein’s model has met its limits and physics needs a new way to model gravity, at least on the largest of scales. The Malta astrophysics group is trying to verify and find new models of gravity — these so-called alternative theories of gravity. The idea is to compare observations to the different gravitational theories, including Einstein’s, and see which works best.

Our focus is split two-ways: one is the effect that celestial bodies have on each other’s orbital motion and the other is the bending of light around heavenly bodies. For example, our sun bends spacetime, causing the planets to go round it in ellipses. The sun also wobbles around a very small orbit. Observations show that the orbiting objects go round a bit longer than we would expect. The extra amount is miniscule, so measurements are taken after many orbits as this magnifies the effect. We use this as a possible test to disqualify alternative theories and have already shown how an important alternative theory of gravity cannot be true.

This is how fundamental science works. If a model does not match observations it needs to be modified to arrive at something that does give all the predictions we require. The end result must be a complete theory by itself but the different components could find their birth in a wide variety of unconnected sources.

Computer simulation of dark matter

The Malta astrophysics group considered a theory called conformal Weyl gravity that is similar to general relativity in every respect except one. This theory behaves exactly like Einstein’s but imposes a further constraint — mainly that the gravitational field remains the same no matter how much it is stretched or squeezed. Simply put, as long as the mass remains the same, gravity does not change. This assumption solves many problems. It makes dark matter and dark energy unnecessary. Dark matter is needed to explain the motion of stars in galaxies. Like dark energy, it is called dark because it cannot be seen or analysed in any way. Making them irrelevant would fill a gaping hole of knowledge for astrophysics.

When the group tested the Weyl theory, it gave the same result as general relativity and a small additional term. That was not a problem, since effects of this term were so small that they could not be observed with today’s largest telescopes. The problem, as shown by the Maltese astrophysics group, is that the term grows larger with distance and contradicts observations at the largest galactic scales. This was an important nail in the coffin for the Weyl theory of gravity and Einstein’s theory still remains the best model.

Our next step is to test other alternative theories of gravity by analysing how objects orbit each other. In the same way we disproved conformal Weyl gravity, we hope that these tests will help astrophysicists to eventually come closer to a model that correctly explains the cosmos.

Bending light

Gravitational Lensing is perhaps the most sensitive test of gravity on cosmological scales. To understand how it works, consider a lit candle and a wine glass. Imagine holding the wine glass and peering at the candle through the glass’ base. The flame will be distorted and changes shape. Now picture you are with a friend who stands a couple feet by your side. The flame will appear normal to them since they are seeing it from a different perspective and the light does not pass through the glass. Two people with a different point of view see different flame shapes. The wine glass’ base distorts the flame because it acts like a lens changing the direction light travels. Obviously in the Universe there are no wine glasses between the stars and the Earth but objects with huge masses like our sun or galaxies can act like a lens and bend the direction of light by the sheer force of gravity.

The wine glass effect: gravitational lensing is explained using the base of a wine glass and a black dot
The wine glass effect: gravitational lensing is explained using the base of a wine glass and a black dot

When there is no mass to affect it, light travels in straight lines, but insert a massive object and hey presto, the light deflects around it as if it were going through a curved glass lens. The area in which an object feels the gravitational pull of the Earth is called the Earth’s gravitational field. Each object in the Universe has a gravitational field and can therefore pull other objects towards it — like the Earth’s effect on the Moon, which keeps it in orbit.

Anything that enters an object’s gravitational field will feel a gravitational pull towards the center of the object. Imagine a ray of light traveling from a point to another with nothing in between. In this case the ray will travel in a straight line. Nevertheless, if the ray meets with an object along its way to the Earth, the object will pull the ray towards it as a consequence of the object’s gravity. Even though the ray of light will try to keep moving in a straight line, the gravity of the object is so strong that it bends the ray’s path. If a star’s light is being bent by a galaxy, from Earth it will appear that its light has changed, when in reality it would not have changed at all. This effect is called Gravitational Lensing and is currently one of the best tests for alternative theories of gravity, since one can measure the deflection of light and check whether it agrees with the theoretical predictions.

Gravitational lensing is clearly visible on Galaxy Cluster RCS2, as viewed using the Hubble Space Telescope

Extreme situations like the bending of light by galaxies cause problems for Einstein’s theory. When summing up the masses of the galaxies, we obtain the mass of the objects that are visible in the cluster. Comparing the predicted light deflection with the observed one, astronomers consistently find that the light is bent ‘more’ than is expected. The way to solve this issue is obvious. Introduce a completely invisible mass that increases the amount of bending until the predictions fit the observation: enter dark matter!

The idea of dark matter emerged a while ago. In 1933, Swiss astronomer Fritz Zwicky suggested it when studying how a galaxy rotation changes as one goes further away from the galaxy’s center. Zwicky observed that the speed or velocities predicted by Einstein’s theory should tear the galaxy apart. In reality, something must be keeping it whole. The idea of an invisible substance called dark matter was born.

Dark matter keeps the Universe together by opposing dark energy that pushes the Universe apart. Dark energy is related to the cosmological constant, previously discarded as Einstein’s biggest blunder, now reintroduced in astrophysicists’ equations to explain the accelerated expansion of the Universe.

The problem with dark matter is that it has never been seen. There is only indirect proof of its possible existence. Deandra Cutajar’s work focused on testing theories where no dark matter is needed. If true, this would put a small spanner into Einstein’s equations.

She tested two theories. They passed the first tests, but they have to pass many more to unseat Einstein’s general Relativity. Going back to the Swiss astronomer Zwicky, the two theories could explain why galaxies are not ripped apart by the speed with which they spin. Dark matter could be dead.

In another test, both theories failed to explain the extra gravitational effect observed in lensing. One theory failed miserably, while the other yielded less accurate results than Einstein’s general relativity. Dark matter is reborn; on the other hand, it cannot remain dark. It needs to be found and studied.

No theory of gravity has yet been found to beat Einstein’s equations. The explanation of how gravity works according to Einstein is better than Newton’s. A curved spacetime clearly explains why light is bent. Einstein’s theory of gravity still holds water and apart from the cosmological constant (his biggest blunder), he was right on most things. When his stunning prediction of how light can bend was observed, he replied, ‘I knew the theory was correct. Did you doubt it?’

What the future holds for any theory of gravity is uncertain, but what is definitely true is that the astrophysics group in Malta cannot accept the fact that we don’t understand 95% of the universe.

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Gravitational lensing

More gravitational lensing

Gravitational lensing of distant star-forming galaxies (schematic) from ESO Observatory on Vimeo.

 

See dark matter