Last week, we were fortunate to have Nikki Miller, a Masters student at Warwick University come to speak to us about her ongoing research on x-rays and exoplanets. We learned about the different ways that exoplanets, or extra-solar (outside our solar system) planets, are detected, and the problems that arise when detecting them: we are usually blind to them because the light from the host star is too bright to be able to see the planets it may have. There are however several methods including transits and photometry used to detect these exoplanets, and look for the planets which may be able to harbour life. We found out that, much to our surprise and awe, that planets can evaporate! Due to planets which are very close to the star being hit with high levels of ultraviolet radiation and X-rays, the atmospheres of the planet start to evaporate away. No need to say that this has a huge effect on the planets. However, as researches study the planets, there are many things that they cannot understand. By (indirectly) observing the planets, we can work out the rate at which they are loosing their mass. However, when we see the bigger picture, the said cluster of stars in which this planet resides in very old. So the question is why are the planets still there? By calculation they should have been completely evaporated many many thousands of years ago. There are several explanations for this: perhaps the planet was further away from the star in the past, or maybe the star is emitting more X-rays today than it did before. Needless to say, the talk was very much enjoyed by all who attended. Nikki Miller even told us about life as a university student, and her interest and proficiency in Astro-photography. Many thanks to all who attended the session.
0 Comments
Thank you to all of you who attended this Monday! I hope that all of you enjoyed it. First the question was posed: Do you think there is life outside Earth, somewhere in the universe? All the answers were yes! - there is life in the universe. The second question was: Do you think that we will find life in the universe? The answer to this question was a little shaky to say the least; no one was prepared to commit to us finding life in the universe. So what is needed for life? Here is what you said:
The Drake equation is a way of showing how likely it is that there is life in the universe which is actively trying to communicate with us. N - the number of communicating civilizations in our galaxy R* - The rate of star formation in our galaxy fp - the fraction of these stars which have planets ne- the number of these planets which have the potential to support life; which are earth like fl - the fraction of these earth-like planets which actually develop life fi - the fraction of this life which develops intelligence fc - the fraction of this intelligent life which develops communicative technology L - lifetime of such a civilization The first two terms of the equation are perhaps the ones most based on factual knowledge. We know that the rate of star formation in the galaxy is around 7 stars per year. There has been a lot of research about exoplanets recently, are we believe that almost all stars will have a planetary system of some sort. After that is when the things start moving into the realm of guesswork. We can move to each term guessing a number for each one, simply because we don't know enough about the universe. We only have one example of a solar system that we can scrutinize, and only one form of life: perhaps the greatest example of inaccurate extrapolation. There are however some terms which can create intrigue in a discussion: the fraction of life which develops intelligence. Would it be wrong to say that this is 100%? If life develops, surely it would evolve to intelligent beings? The terms after that is an interesting one too. We are currently searching for extraterrestrial life by sending radio waves into space. Our form of communicative technology is electromagnetic radiation. Based upon our knowledge of the universe, EM waves are a widespread phenomena; definitely not something we have created. Would it be a stretch to say that intelligent living being somewhere in the far reaches of the galaxy also uses radio waves? Probably not. But then again, who's to say that these aliens haven't developed something like telepathy? As for the lifetime of such as civilizations, how long will they actively broadcast for? A better question would be how longs are we going to broadcast for? 100 years? 1,000? 10,000? In short, we simply do not have enough knowledge to make a prediction which is anywhere near accurate. However, it is a great way to speculate about life in the universe. Put in you own number and see what result you get! (We got about 2500 communicating civilizations in our galaxy on Monday) Shubhangi Thank you very much to everyone who attended our student presentation on the world of Genetic Engineering and its future, co-presented by myself Evelyn Day and Jenny Marsh. Initially we covered a brief background into what genes are, where they are and what exactly they do in the body, and why in some cases this can be a problem, such as mutated genes that can cause disease and disability in people. We then explored many areas of the wide field of genetic engineering from some of the basic techniques of genome editing that are commonly used today; gene insertion into an organism via a virus or agrobacterium vector, all the way to DNA ‘cutting and pasting’ with specific DNA enzymes called DNA endonucleases and ligases. We also explored their roles in the research of genetics, for example with Knockout Mice as a valuable research resource into the more specific functions of different genes, and other more medicinal applications in different forms of corrective Gene Therapy, drawing on more specific examples such as a potential genetic treatment for Cystic Fibrosis.
We then moved on to one of the more topical aspects of Genetic engineering today, CRISPR-Cas9, an only relatively recently discovered ancient immune mechanism present in almost all bacteria that allows them to fight and acquire immunity to viral infections. We spoke a little about CRISPR’s history and its recent discovery in 2012 by Jennifer Doudna and Emmanuelle Charpentier, and then on to what it means for genetic engineering. After a viral infection of a bacterium, the CRISPR immune response is designed to target a specific section of that infecting viral DNA that has been incorporated into the bacterial DNA, very quickly and very accurately. The Cas9 ‘cleaver’ protein in the Cas9-RNA complex ‘cuts out’ the offending viral DNA section, leaving a gap in the bacterial DNA (which the organism then closes with one of two response pathways). This gap is crucial for scientists as they are now able to stuff new DNA into it. The revolutionary aspect about CRISPR is the precision, accuracy and reliability to which it functions, traits which most other genome editing techniques fail to exhibit. Its targeting system is very easily reprogrammed to whatever we want, its speed and efficiency cuts the process time from weeks to days, and its simplicity makes it an available tool almost anywhere in the world. We went on to speak about the mixed implications that this has, such as creating artificial gene drives with this technology, and the topic that seems to be often buzzing around the media; ‘designer babies’, and the fact that CRISPR has such a high accessibility to a wide range of scientists of many different abilities and means, pretty much anywhere in the world. Finally, whilst still meditating on these thoughts we ended the presentation with questions on how these powerful tools will shape us, the human race, throughout the future, and what rules and regulations should we put in place to stop ourselves going too far? I hope you all enjoyed our talk! Written by Evelyn Day Mr. Robin Stafford Allen gave a fantastic talk on Nuclear Fusion and Energy. He told us why nuclear fusion could be very important in the future. The Earth's growing population as well as increasing wealth in developing counties means that the demand for energy is increasing. Mr. Allen showed us how renewable energy sources may not the answer as they are unreliable and relatively inefficient compared to burning fossil fuels, but also how fossil fuels are unsustainable for the future and contributing to global warming. So fusion might just be the answer. ITER - The World's Largest Fusion Experiment Mr. Allen went on to tell us the basics of what fusion is and how it can produce energy. In fusion, they use two heavy isotopes of hydrogen, Deuterium and Tritium to create Helium and a high energy neutron. In the process 0.4 of the mass of the nuclei is lost and released as energy. There is a lithium blanket that captures these energetic neutrons and fusion of the lithium and the proton occurs producing Helium, Tritium (which can be used in the main fusion reaction) and heat, this heat can be used to boil water, produce steam, drive a generator and produce energy. Reacting 1 gram of Deuterium and Tritium produces the same amount of energy as burning 10 million grams of coal or gas. Mr. Allen explained that if fusion is to occur the isotopes have to be heated and turn into a plasma, they are heated in three ways, Ohmic heating, Radio Frequency heating and Neutral beam heating. He said however if the plasma touches the walls of the reactor it would severely damage the machine, so to stop the plasma from doing this, a magnetic field is created to hold the charged particles away from the wall. Mr. Allen explained that to create this strong magnetic field they must use electromagnets, and for the field to be so strong a huge current has to run through the machine. But because of resistance, everything heats us very quickly so the machine can only be switched on for 15 seconds before it overheats and has to be turned back off and left to cool. This problem is in a reactor called JET in Oxford. Mr. Allen told us about a new reactor being built in France called ITER which uses superconductors so the machine can keep on running without heating up. However ITER has limited funding from governments and the high energy protons damage the materials that the machine is built from, but because high energy protons are only really produced in these fusion reactions there isn't a lot of research on resistant materials. Mr. Allen finished with telling us the many advantages to fusions, there are little or no environmental impacts, it doesn't produce only ‘long-lived’ radioactive waste and the resources needed are abundant in the Earths crust and water.
Written by Nina Mulder-Qureshi Professor Paul Harrison came in to talk to us about particle physics. He began by telling us about the standard model of elementary particles and about quarks and gluons- including the composition of protons and neutrons, and how all quarks are point like (can't be measured) and bound. He then moved on to tell us about the 'Guiding Principles of Particle Physics':
He then moved on to talk about his work at CERN, as well as telling us briefly about the discovery of the Higgs boson particle, and what is made on particle colliders. Lastly, he talked about the questions still facing particle physicists today: Is the Higgs boson as expected? Why is the Higgs bosons mass stable? Is the dark matter of the universe really a new undiscovered particle? How to unify strong force with weak and electromagnetic? Why do elememtary particles take the masses they do? Written by Jess Astley
It was great to see many people attend our first event of the year, a student talk on Cosmology and its implications on humans.
The start of the discussion was about the different theories for the birth of the universe. Many people are already aware of the term 'Big Bang' and the accelerating universe and what this means, but not many know the three base theories: the Open universe, the Closed universe, and the Flat universe. These are the three terms which according to theory, model the fate of the universe. The Open universe is one that says that the universe will continue expanding for an infinite period of time; the Closed universe says that the universe will re-collapse into a 'Big Crunch', and the Flat universe is one which is on the brink of collapse but never actually does. As for the implications of this for humans - one can only imagine! What would be the most desirable outcome in your opinion? Of all the ideas connected to Cosmology, perhaps the most interesting, yet most misunderstood is the idea of Imaginary Time: an idea that time is not really what we time it is. (The word 'imaginary' here does not mean that this is not real. It is to do with the unfortunate naming of two sets of numbers as real numbers and imaginary numbers: regardless of their names, they are both very real.) Imaginary time is comparable to a directionless spatial dimension which is circular. What we live in, 'real' time is somewhat of an idea we have created ourselves. We constantly travel through this time dimension as we do in the three spacial dimensions, and in our relatively small scale, we have mistaken it to be linear. This connects well to Stephen Hawking's No Boundary model of the universe, which proposes a finite universe which is directionless, that is to say a universe in which the dimensions themselves are finite but directionless: the x, y z and (imaginary) time dimensions. An analogy given by Hawking himself in the Brief History of Time is to imagine this like the Earth. It is definitely finite, but doesn't really have a direction. The theme of Circularity is apparent in these theories, but circularity is one that we find everywhere: planets, stars, orbits, atoms, protons, quarks, string theory... even we as humans seem to subconsciously understand that time itself is circular not linear- just look at the shape of our clocks! This is just some of the evidence pointing towards a closed universe, showing that even though the accelerating universe is the current most widely accepted theory which there is a lot of proof for, the question of the history of the universe is still field in which new discoveries will undoubtably be made. I hope you all enjoyed learning about the universe on a grand scale. The next event, 9th October, will be about science on the smallest scales: Professor Paul Harrison of CERN will be speaking about Particle Physics. I hope to see many of you at what will be a a very interesting talk. Shubhangi Cassini: The Grand Finale It’s been a long journey for a small craft but, after 20 years and having travelled 7.9 billion kilometers, Cassini finally reached its end on the 15th of September: diving through Saturn’s rings to burn in its atmosphere and merge with the planet itself.
This last part of the mission has brought us unprecedented insights about Saturn: the craft continued communicating data until its last moment of contact, relaying precious information about the composition of Saturn’s atmosphere, its magnetic field, ionosphere and rotation rate, measurements which have never been viable to collect before. However, this atmosphere is also Cassini’s killer, heating it up as it races through and, without a heat shield, Cassini has no protection against the rapid temperature increase, breaking up in a spectacular fireball over an alien world. This triumphant loss might seem both a tragic good bye and a waste of the millions of dollars invested in the craft, however it is far from such: The Grand Finale was part of a 7-year extension to Cassini’s mission which brought incredible discoveries, unlocking the door to our solar system as never before. However, Cassini’s fuel has run low and the hazard of operation control loss could risk Cassini crashing and contaminating Saturn’s moons, endangering the search for extra-terrestrial life through the introduction of terrestrial microbes. So, instead of losing Cassini to an eternal trek around the solar system, Cassini was to become a sacrifice in the name of discovery: and what an adventure it has been! Cassini began its journey in October 1997, with a spectacular launch of a Titan IVB/Centaur rocket from Cape Canaveral carrying Cassini and the Huygens probe. Taking a gravity assist past Venus accelerated the spacecraft towards the outer Solar system, visiting Earth, the asteroid belt, and Jupiter on a 5-year trek to Saturn’s system exploring moons like Enceladus, Titan, Mimas and of course the planet itself. At last, on the 31st October 2002, Cassini captured its first test image of Saturn still 285 million Km from the planet, the images that followed unravelled the secrets of the planet: giant storms, new moons, and of course the exploration of Titan. The Cassini mission, was in fact the Cassini-Huygens mission, due to the probe that took a piggyback along with it. On Christmas 2004 this probe detached from Cassini beginning a 3-week journey to Saturn’s moon Titan. Huygens descended through Titan’s thick, hazy atmosphere, making the first ever landing in the outer solar system. Although the probe lasted only 2 hours on the surface, it discovered a spectacular rocky world, with Earth like geology and meteorology. Whilst its partner fell into a deep sleep on Titan, Cassini continued streaming information from its orbit: capturing images of a Giant equatorial ridge on Iapetus, spotting lakes of discovering strange magnetic fields around Enceladus and particles of dust or ice coming from the moon itself promoting a closer look. Enceladus has had more than its share of the greatest discoveries by Cassini, images revealed a young terrain, free from craters, suggesting a tectonic activity, along with a warm fractured crust (‘tiger stripes’), ammonia traces and clouds of water vapour reaching into space. All evidencing an active world and liquid water existing on the icy moon. In February 2010, following the incredible successes of the journey so far, the Cassini-Huygens mission was given a 7 year extension (the Cassini Solstice Mission) to explore Saturn and its moons until 2017, allowing the observation of seasonal changes. Further discoveries followed: the first oxygen molecules from a foreign atmosphere were found around Rhea; a monster storm, stretching around the whole of Saturn’s circumference and eventually eating its own tail -the first time such an event has ever been seen-; further data evidencing saltwater reservoirs under Enceladus’ crust, with 101 geysers witnessed; the famous publicised ‘wave at Saturn’ image, where a small, blue, star-like Earth peeks out from the shelter of Saturn’s rings; high resolution images of Saturn’s spectacular hexagonal storm at its north pole. In 2015 Cassini began to say goodbye to many now familiar features of Saturn’s system as the craft made its final flyby of moons like cratered Hyperion, icy Dione and fractured Enceladus. There were still discoveries to be made though: Titan’s highest peak Mithrim Montes was identified; samples of interstellar dust were taken; large seas of pure methane were confirmed on Titan, possibly surrounded by wetlands; and indication of hydrogen on Enceladus suggesting potential chemical energy for life. At the end of November 2016 Cassini began a series of 22 inclined orbits carrying the craft ever closer to Saturn, whilst an image taken this April show our own lonely planet trapped between its arching rings. April 23rd, 2017 marked Cassini’s 127th and final flyby of Titan, soon to be followed by its first of 22 dives through a gap in Saturn’s rings, marking the beginning of the end: ‘The Grand Finale’. Halfway home Cassini observed seasonal changes in Saturn’s hexagonal storm and analysis particles closer to Saturn than any human sent mission has ever been before, analysing the origin and age of the rings we see today. Now diving at tens of thousands of miles per hour the spacecraft follows an elliptical pass. On September 11th Cassini passed 120 000km from Titan, whose gravity altered its trajectory just enough to ensure that Cassini’s next transit through Saturn would be its final flight. The spacecraft was hurtling to its death. At 1:47pm PDT on September the 14th Cassini powered up for its final plunge, and as the Earth rotated in its own orbit far away, pulling Saturn out of view from California’s antennas, the Australian station took over receiving Cassini’s signal. Descending into Saturn’s atmosphere at 3:30:50 am PDT on the 15th, the craft transmits precious, unique data whilst its thrusters fire at full capacity. Two minutes later signal is lost. Written by Lucy Hyde “With Cassini, we had a rare opportunity and we seized it” -Linda Spiker, Cassini Project scientist. Now a new school year has begun, it is time to relaunch Scientific Cafe. With the end of Cassini's mission, and therefore its destruction only a few days away, we say goodbye to this incredible spacecraft but hello to another year which is sure to be filled with new scientific discoveries and theories.
This year we aim to invite many exciting external speakers, discuss several topical issues and of course, have talks by the students themselves. We will be meeting every two weeks starting after school on 25th September - we hope to see many of you attend our first student talk on Cosmology! This blog will be updated at least once per week, telling you about our talks, external speakers, the latest news on scientific discoveries, and anything else that we think will interest you. This year our team has five members: Jess Astley, Eleanor Griffin, Jenny Marsh, Lucy Hyde and me, Shubhangi Bhatt, and our supervising teacher will be Mrs. Sims. Come and join us in discovering science! See you soon! Café Scientifique were treated to a fun and informative talk from old girl Serena De Nahlik (KHSW 2004-2011), about her time at Oxford University studying Engineering and her career after getting her degree. She talked about her third and fourth year projects, the first of which was based on helping a team design a prosthetic limb which was controlled by muscle impulses. Her fourth-year project was co-culturing nerve and muscle cells on an electrospun scaffold, which is essentially figuring out how to make nerve and muscle cells grow in a natural way with the help of a specially made plastic scaffold. Serena also talked about her first job out of university, which was with Oxford Mestar working on building a bioreactor which grows cells for cell therapy. Finally, we learnt about her current work with Oxford University Innovation, helping academics at the university start businesses and get patents. It was lovely to hear about all the exciting, and unexpected opportunities an engineering and science degree affords, especially from an old girl.
Let me take you back to 8th November 1895, to the University of Wurzburg, Germany and in particular, Professor Wilhelm Roentgen’s laboratory. . Late into the evening, whist experimenting with a cathode ray tube, Roentgen observed barium platino-cyanide crystals fluorescing. And although he did not yet know it, Roentgen had begun the story of one of the most significant inventions to impact on man-kind – X rays.
So what was Roentgen observing that night? The cathode ray tube is quite simply an electron beam. If we look at a simple model of an atom, and an incoming electron, it is possible to see that when an electron collides with the atomic electron, it can cause the electron from inside the atom to move from an inner shell to an outer shell. Energy is needed for this process because the atomic electron moves away from the nucleus of the atom. This process is known as excitation. The electronic configuration in an excited atom is unstable because an electron that moves to an outer shell leaves a vacancy in the energy level that it moves from. When this vacancy is filled by an electron from an outer shell moving into it, the electron emits a photon. This process is known as de-excitation. The energy of the photon is equal to the energy lost by the electron and therefore the atom. However, an atom / electron in its excited state can de-excite directly or indirectly to the ground state, regardless of how the excitation took place. If we now look at an energy level diagram, for example of a mercury atom (pg 37), it is possible to see that whilst the electron has been excited to the 5.7eV (electron Volt) energy level, it can de-excite in two ways and therefore produce three different photons. The electron can de-excite from 5.7eV to the ground state directly by emitting a photon of 5.7eV or it can de-excite indirectly, it can de-excite from 5.7eV to 4.9eV by emitting a 0.8eV photon and then further de-excite to the ground state by emitting a second photon this time with energy of 4.9eV. When the de-excitation occurs, the material seems to glow with visible light, this process is known as fluorescence. And this is what Roetengen observed that evening. So how did barium platino-cyanide crystals fluorescing lead to the discovery of X-rays? Roentgen knew that the gas particles within the Cathode Ray tube would fluoresce with visible light. However, he covered the tube with black paper, which had been known to absorb the light, and so when the barium platino-cyanide crystals started fluorescing (these were on the other side of the room), he knew that a different form of light (which was invisible) had been emitted causing the crystals to excite using photons (this is a similar to principle to excitation by electrons, however, the photon must have energy exactly equal to the energy needed to move the electron to a different energy level), and then de-excite emitting visible light. This invisible light, had not been discovered before and was capable of passing through heavy black paper. As Roentgen continued his experiments, he discovered that these rays (now known as X rays), passed through most solid substances and would cast a shadow on photographic film. This application of the production of pictures of X rays was quickly interwoven within medicine. Another potential application of X rays came in 1912 from Max von Laue, whose worked related to X ray diffraction and crystallography. Research was already being carried out into the interference between radiation with large wavelengths (practically visible light) on a crystalline model based on resonaters (during this period of research the discussion of wave-particle duality was happening). Laue realised that using much shorter electromagnetic rays (which X rays had been theorised to be due to Barkla’s discovery that X rays could be polarised but not made to diffract, and calculated by Laue’s colleague), some kind of diffraction or interference would take place if X rays were sent through a medium (which crystals could be used as). Laue demonstrated this by allowing X rays into a lead box containing a crystal (he initially tested the principle with copper sulfate crystals) with sensitive photographic film behind and to the sides. When the film was developed there was a large central point from the incident X rays, but there was also many smaller points in a regular pattern. These could only be due to the diffraction of the incident beam by the atoms within the crystals and the interference of many beams. By using a crystal as a diffraction grating, laue had proved that X rays were not particles but waves of light with very small wavelengths. However, there was one major issue with Laue’s work. Laue had recorded his work photographically, with bright spots showing points where many X-rays were in phase together. However, there were a large number of points where these spots appeared to be “missing” i.e. diffracted beams of X-rays were expected in these direction, but didn’t occur. Laue suggested that this was because X-rays only contained certain wavelengths which would therefore account for the missing diffracted beams. However, William Lawrence Bragg was not convinced by this explanation. Bragg thought that x-rays must be made up of a continuous spectrum of all possible wavelengths similar to visible light. If this was true, then the missing directions of diffraction would not be because of the wavelength of X-rays, but due to some property of the crystal being examined. Bragg therefore examined each plane of atoms in a crystal as a reflecting surface. The X-rays hit each plane of atoms in turn, reflecting first off the surface layer, then the one below it and so on. If the X-rays reflected off al the surfaces were in phase, with their peaks and troughs all aligned, then a very strong signal could be measured from the reflection. Over the following years, Bragg developed his equation which allowed him to explain the crystal structure of Zincblende crystals (the photograph that Laue had initially taken). Since this point, X ray diffraction has developed rapidly, to the extent that Rosalind Franklin could photograph the structure of DNA in 1952, which then led to the discovery of the double helix structure of DNA. This has paved the way for scientific research, and has allowed genetic modification to develop. However, it is not only X ray diffraction that has developed over the last 100 years. X-rays are now classified into two types; hard and soft. Soft X-rays are found in the electromagnetic spectrum between Gamma Rays and UV light, with a wavelength of about 10 nanometres to about 100picometres and with very high frequencies (around 3x1016Hz to 1018Hz). Hard X rays, on the other hand, have a higher frequency (around 1018Hz up to 1020 Hz) and therefore occupy the same region of the Electromagnetic spectrum as gamma-rays. So, what is the difference? There is only one, and it links to the way that they are produced. Hard X-rays are produced by accelerating electrons, whereas gamma-rays are produced by the decay of atomic nuclei. Hard X-rays are now most often produced in syncotrons, for example at the Diamond light source. The uses of X-rays have also increased, from purely being used as an opportunity to image bones within the human body when they were first discovered, theey are now used to identify flaws or cracks in structural components, airport security and fishery, to name just a few, clearly showing the wide ranging significance of Roentgen’s discovery on mankind. |
AuthorOur blogs are written by the girls that attend this society. Archives
June 2020
Categories |