Physics Special Topics
Highlights of Physics Special Topics Vol.11
The 2012/2013 issue of the University of Leicester Journal of Physics Special Topics is now complete.
The 64 articles in volume 11 cover a huge spectrum of physics, dealing with subjects ranging from Relativistic Optics, through Hot Air in the House of Commons, all the way to Harvesting the Gas Giants.
It's always entertaining but, of course, the Journal also has a serious educational purpose, and all the papers that are published pass a stringent peer review process.
Below are the eight papers that the students selected as this years highlights...
Joshua Argyle, Riley Connors, Katie Dexter and Cameron Scoular, Phys. Spec. Top. 11.1, 2012.
Physicists shed new light on Star Wars. The famous 1970s motion picture Star Wars depicts the stars as stretched beams of light passing the view of the Millennium Falcon as it nears the speed of light. Four physicists from the University of Leicester, Riley Connors, Katie Dexter, Joshua Argyle, and Cameron Scoular, have shown that Han Solo and his companions would not see the stars elongated in this way, due to the laws of special relativity.
They have shown that the crew would actually see a central disc of bright light as a result of the Cosmic Microwave Background Radiation. This is the background radiation left behind from the big bang, the same static feedback you see on your television. On top of this, starlight actually takes the form of X-rays, and is not seen with the naked eye.
Riley Connors, 21, said “If the Millennium Falcon existed and really could travel that fast, sunglasses would certainly be advisable. On top of this, the ship would need something to protect the crew from harmful X-ray radiation. “
The group found after further investigation that these intense X-rays would push the ship back, causing it to slow down. The pressure felt by the ship would be comparable to that felt at the bottom of the Pacific Ocean. Calculations outlined in the second of two published papers on the issue have shown that Han would need to store extra amounts of energy on his ship to overcome this pressure and continue on his journeys.
The work the group of physicists carried out was based on travelling towards a star like our Sun. They suggest that when that if all the other stars in the night sky were included in the calculations, these effects may be amplified significantly.
Joshua Argyle, 22, added “The resultant effects we worked out were based on Einstein’s theory of Special Relativity, so while we may not be used to them, Han Solo and his crew should certainly understand its implications.”
Katie Dexter, 21, concluded “perhaps Disney should take the physical implications of such high speed travel into account in their forthcoming films.”
Hot Air in the House of Commons
Daniel Staab, Emily Jane Watkinson, Maria-Theresia Walach, Zach Rogerson and Phys. Spec. Top. 11.1, 2012.
Each week MPs spend hours debating over the fate of the country. Have you ever wondered whether these heated debates could be put to use?
Physics students at the University of Leicester recently showed that the power output of 650 arguing MPs is the same as about 1000 energy saving light bulbs or 200 old fashioned light bulbs.
A surprising amount of energy is produced during a fiery debate by the MPs’ vigorous breathing alone. The chamber’s historic construction does not capture the heat and so most of it is lost through the roof.
“Unfortunately, if the temperature in the chamber should stay at a pleasant 20 ˚C, you would have to turn the heating on as soon as the outside drops below 19.8 ˚C. So it isn’t much use with our weather!”, says Emily Jane Watkinson, a co-author of the paper.
Planning is in the works for general renovation of Westminster Palace. New insulation could make the MPs heat output more useful and reduce the energy bills of future Parliaments.
“We assumed the hot air output is the same for members of all parties and will stay the same in the future, regardless of who wins the next elections”, explains Daniel Staab, co-author.
Kate Houghton, Ashley Clark, Henry Simms and Jacek Kuzemczak, Phys. Spec. Top. 11.1, 2012.
Walking under the waves. A group of Physicists at the University of Leicester have calculated the possibility of using an upturned boat to walk underwater.
They found that the air in an upside down rowing boat, similar to the one used in Pirates of the Caribbean: The Curse of the Black Pearl, could provide enough oxygen for two people to survive for nearly three hours! This is more than enough time for the pirates to escape to their getaway boat. Kate Houghton, the lead author, said “when watching the film, we initially thought that the entire concept was unrealistic so we came up with a model to analyse the scenario. The results were definitely unexpected!”
The composition of air inside the boat was considered and the changes were modelled on a breath by breath basis. The buoyancy of the boat was then considered. It was found that the pirates would not have been able to hold the boat down as the amount of air inside the boat would provide an upwards force far greater than they would be able to overcome.
Unfortunately, extremely heavy weights would be required to keep the upturned boat underwater. The physicists state that, providing the buoyancy of the air contained in the boat can be overcome, “there would be more than enough air available in the boat to allow two pirates to traverse a small bay, without needing to come up for air!”
This would allow the possibility of several new beach products for scuba diving training and snorkelling. If a specialised boat were designed to include oxygen tanks, the duration that could be spent underwater would be increased significantly.
Make a "Brake" For It!
Suzanne Thomas, Declan Roberts, David Starkey and James Nelms, Phys. Spec. Top. 11.1, 2012.
The use of a solar sail to capture solar radiation and convert it to work is a concept yet to be implemented on any space missions beyond simply powering a satellite. In their paper submitted November 21st, Thomas et al of the University of Leicester, investigated a novel use of this technology to transfer a satellite orbiting Mars from an initial circular orbit, to one which would see the satellite captured by the Martian atmosphere where it could then be brought safety to land.
In the paper entitled, 'Make a “Brake” for it!', the area required for a solar sail to cause the orbit of a 100kg satellite to decay to an altitude where the drag of the Mars atmosphere can bring it down, is found to be 0.55km2.
David Starkey co - author explained, “Such an area is roughly equivalent to 440 Olympic size swimming pools. It’s difficult to imagine how one could fold such a large area into the structure of the satellite and deploy it as required, a more practical option might be to use a smaller sail and complete the manoeuvre in multiple orbits.”
The solar sail has applications beyond braking. Altering the orientation of the sail with respect to the incident light (whether emitted directly from the sun or reflected from the surface of a planet) can cause the satellite to accelerate too. Use of sails to transfer between orbits is a promising method of reducing fuel requirements for future space missions.
The Penny's Dropped
Joshua Wynn, Peter Edwards and Liam Allen, Phys. Spec. Top. 11.1, 2012.
Don’t worry America!!! The penny has dropped… Slowly. Young scientists at the University of Leicester have investigated one of the most common myths relating to the famous American landmark, The Empire State Building. It is commonly suggested that dropping a penny from the 102nd floor of the largest building in New York could cause death to any passer by walking below who happens to get struck by it. If no one does get hit then it has also been proposed that the penny would be able wedge itself in the floor below due to its intense speed.
Using an advanced level gravity law and air resistance calculations, Leicester Physicists calculated what the real effect of the penny would be.
The highest floor easily accessible in the empire state building is the observatory deck on the 102nd floor. This stands at a height of 381m above the pavement. Because the building is so high we can assume the penny reaches its terminal velocity, this is when the effect of gravity on the penny balances with force pushing up of the air, at this point the speed of the penny stops increasing. Calculating this speed gives the energy the penny has on impact.
The results show that the penny has a Kinetic Energy of 0.24 Joules on impact which can be translated into a specific energy of 67.4 joules per kilogram. This is not enough to kill someone or even badly injure them. Comparing this result to other known specific kinetic energies the penny is less lethal than being hit by a paintball or even an ice hockey puck. Both of which could only cause death in very exceptional circumstances.
Josh Wynn, a student reading space science, suggested “Although actually dropping a Penny from the Empire State Building is extremely difficult due to its step like exterior, dropping something heavier could in fact cause terrible damage to passers-by below; because as seen in the calculation, the energy depends on the weight of the object.”
James Forster, Mark Bryan and Alex Stone, Phys. Spec. Top. 11.1, 2012.
Halo’s friendly fire. Students theorise on the effects of the Halo series “MAC” weapon in atmosphere.
A group of physics students at the University of Leicester were excited to get their hands on the latest game in the Halo series of video games- Halo 4. Not necessarily because they wanted to play it, but because it offered an extra chance to test their theory on the effects of firing one of the franchises most iconic weapons- the tautological MAC cannon, in the atmosphere.
In the series previous instalment- Halo: Reach, there is a scene in which the MAC (Magnetic Accelerator Cannon) is fired upon an enemy installation. The group’s paper sets out to determine what effect this would have had on the player’s aircraft, hovering a few kilometres away. Their calculations suggest that the pressure wave from the cannon’s impact would have knocked the aircraft out of the air. They found that the energy released by such an impact would have the same energy as a 59.7 kiloton nuclear bomb.
“Within the game itself characters claim that using the weapon is a dangerous idea” claims Alex Stone, co-author of the paper. “However we believed that the true danger was never actually realised within the game. Cursory examination of the energetics alone makes this an obvious fact.”
Indeed the paper a pressure wave over 580 times atmospheric pressure would be formed purely by the projectile travelling through the air, to say nothing of the impact itself. The paper also discusses the use of the larger “Super-MAC”, suggesting that its use in atmosphere would be even more inadvisable as the effects of an impact on a planet would mimic the effects of the as yet unseen magnitude 10 earthquake.
“It’s apparent that the use of such weapons, while fine in vacuum, would be a terrible idea in the atmosphere. In the game the characters would die simply due to proximity to the effects of the pressure wave." concludes James Forster, another author.
Paul Cullis, Liam Davenport and Emile Durant, Phys. Spec. Top. 11.1, 2012.
Saddam’s supergun could have created a big impact on the Middle East. Physics students at the University of Leicester have investigated the performance of the Iraqi Supergun that was being constructed in the 1980’s. They found that the gun would have been capable of reaching over 1400km in range or over 1000km straight up. If built this could have made a major impact in the region. Two such devices were planned one facing towards Israel and one facing toward Iran. Although immobile, such devices could have posed a threat if combined with on board guidance system.
Emile Durant, one of the three students who worked on the project, said ‘This potentially could’ve sparked a new arms race in the middle east.’
Various factors were considered in the modelling of the flight of the projectile and the conclusion reached was that the gun would perform to Gerard Bull’s (the original designer) initial claims. Due to the very high velocity of the projectile hypersonic modelling was required.
The first paper looked at the gun firing vertically as a possible satellite launch or anti-satellite weapon, while it was found unlikely that it was capable of putting a non-boosted projectile into permanent orbit, it could have held at risk satellite operating at altitudes below 1000km.Liam Davenport said, "Anti-satellite capability has recently been demonstrated by most of the superpowers, it’s likely Saddam was trying to join this club."
The second paper used the same model to investigate the maximum range fired at 33 degrees. It was found the maximum range would be over 1400km which is 400km more than originally stated by Bull.
Michael Cullis said "Had the two guns been completed this could have threatened Israel and Iran and may have altered the dynamics in the middle east, especially if combined with the rocket boosted projectiles Bull had previously worked on."
Harvesting the Gas Giants
Elliott Shaw, Vlad Tudor and David Winkworth, Phys. Spec. Top. 11.1, 2012.
New source of fuel for long distance space exploration? A team of students at the University of Leicester may have found an exciting new possibility for powering space ships using hydrogen from gas giants in our solar system.
In their paper they show how a ship travelling at high speed through the planet’s atmosphere could collect Hydrogen in huge volumes. It is estimated that a typical ship could dip into the atmosphere of a gas giant and quickly gather enough of the highly combustible gas to escape the gravitational pull of the planet with enough left over to fuel further travel.
In their paper ‘Harvesting the Gas Giants’ the students Vlad Tudor, Elliott Shaw and David Winkworth considered the forces that such a space ship would have to overcome. They then calculated the energy that could be obtained from burning the harvested gas to show that certain planets in the solar system could be viable sources for fuel.
Traditionally space rockets carry all their fuel from Earth and this limits how much can be taken. If a high energy fuel could be gathered after launch, this could open up a new era of space exploration.
As Romanian astrophysicist Vlad explains; “The possibilities from harvesting gas giants are incredible; it is thought that these planets are literally spread all over the universe.
Upon combustion just one kg of hydrogen can produce over 140MJ of energy, equivalent to nearly 10kg of wood. Whilst hydrogen contains much less energy than typical rocket fuels, it is abundant throughout the universe which makes this an attractive idea.
There are still problems however. As Elliott explained “Hydrogen requires oxygen to combust. Considering the scarcity of oxygen outside of Earth, you would have to carry it with you from launch. There is currently no way to efficiently transport so much oxygen”.
It seems then that while this technology is not currently feasible, the principle of harvesting gas from giant planets could be a powerful source of fuel for future space ships.