Rey in Star Wars: The Last Jedi wielding an impossible to create (as far as we know) lightsaber © 2017 Lucasfilm Ltd.
A long time ago, in a galaxy far, far away the laws of physics and the rules of nature were torn up and thrown away in the pursuit of sci-fi fantasy. But that’s not to say all Star Wars science is out of this world, there are a few breakthroughs and scientific discoveries that have been inspired by the epic movie series. Celebrating the release of Star Wars: The Last Jedi, Professor Carsten Welsch, Head of Physics at the University of Liverpool and Head of Communication for the Cockcroft Institute explains how Star Wars has inspired concepts at the cutting edge of science.
In 1977’s A New Hope, the very first Star Wars movie, the Rebels Alliance used proton torpedoes to destroy the Death Star as their lasers couldn’t penetrate the space station’s shields. The nearest thing to this in the real world is our use of ‘proton torpedoes’ in cancer therapy.
Within the pan-European OMA (Optimization of Medical Accelerators) project we are using proton beams to target something that is hidden very deep inside the body and very difficult to target and destroy.
The most common form of radiotherapy uses X-rays. The main issue with this method is that for a deep-seated tumour, X-rays deliver a significant entrance and exit dose that damages healthy tissue. This is because the dose deposition follows an exponential decay and it is difficult to target the rays accurately.
An alternative is to use a proton beam. Protons are positively charged particles, created when a hydrogen atom loses its electron in an ‘atom smasher’ such as cyclotron – one of the earlier types of particle accelerator.
Protons are large particles that have the ability to penetrate tissue almost silently for a specific distance determined by their energy; they then deposit most of this energy at a specific location, so the target tumour is destroyed but the healthy tissue is spared. This remarkable phenomenon is called the ‘Bragg Peak’.
This is a rapidly growing method of treatment, in particular in the UK where several new proton beam facilities are currently being built. Proton beam therapy has demonstrated that it can offer superior results for specific cancer types.
We think much more can be achieved, particularly in the treatment of childhood cancers where the targets are smaller and there is potential for secondary cancers to emerge, and also for tumours in adults that are close to vital organs.
OMA Project - Optimization of Medical Accelerators (YouTube/Carsten Welsch)
A unique property of proton beams is that they can be extremely well controlled to follow the outline of the tumour. It is this precision that makes the technology well suited to cancers located in delicate places; indeed the UK’s first (and currently only) proton beam therapy centre at Clatterbridge treats eye cancers.
It is possible to control how deep the beam goes so it can be used to treat a tumour on the iris or at the back of the eye. Also, as protons scatter very little, the beam has sharp edges, which makes it possible to follow the outline of the tumour and protect the optic nerve. We can deliver a consistent dose by modulating the frequency of the beam.
The techniques needed to further improve control over the beam shape and quality and to monitor the dose without disrupting the beam are being developed within OMA , a Pan-European collaboration of universities, research institutes, clinical facilities and industry partners. This new network brings together physicists, engineers, biologists and clinicians to gain a better understanding of dose delivery and distribution, and its impact on both the patient body and the tumour region.
The race to improve the technology is intensifying as more proton beam therapy units are opening soon, including NHS units at Christie NHS Foundation Trust in Manchester (due to open in 2018) and University College London Hospital Services (expected in 2020).
These special proton torpedoes might not help against an approaching Death Star, but it does add another weapon to our arsenal in the battle against a cancer.
The lightsaber, weapon of choice for those strong with the Force, would not be possible according to the laws of physics, but there are many exciting applications on the horizon, such as laser knives controlled by robot arms for high-precision surgery and adaptive manufacturing using lasers for creating complex structures in metals.
The problem with lightsabers is that there is no way to make light emanate from a source and then stop after a metre – light will go on to infinity unless it hits something. Also, if it was a ‘light’ sabre, the two blades should penetrate one another when they clash. Potentially, a flexible cutting blade resembling a lightsaber could be created using plasma, ‘the fourth state of matter’. This hot gas of ionised particles could be constrained by an appropriately shaped three-dimensional electromagnetic field.
Although creating a lightsaber is not an objective, we are looking for ways to make accelerators smaller, more portable and cost-effective for wider application.
For example, accelerator scientists in the international EuPRAXIA project are designing the world’s first high-energy plasma-based accelerator with industry beam quality, which will be stronger and more compact than current accelerators.
In physics, plasma is an electrically conducting medium with positively and negatively charged particles. It can be created from a gas by applying high energy. Nearly all visible matter in the Universe is in a plasma state (for example the Sun is a plasma star.)
EuPRAXIA will direct a laser through a plasma medium, creating a wave and forcing the electrons within the plasma to create a strong electric field. Oscillating between the transverse field of an electromagnetic wave and the longitudinal field of a plasma wave accelerates the electrons, creating a high-quality beam.
Plasma accelerators can sustain an electric field up to 10,000 times greater than conventional radiofrequency (RF) accelerators in a much shorter distance.
This new accelerator will propel electrons to the speed of light over much shorter distances and open opportunities for entirely new applications: imaging ultra-fast phenomena including the movement of biomolecules such as proteins unfolding, or the testing of innovative materials … but not for building lightsabers!
The light and dark side of the Force in Star Wars is an ideal opportunity to talk about matter and antimatter interactions, which we are exploring in the brand-new research network AVA (Accelerators Validating Antimatter physics).
Antimatter has long been the stuff of science fiction: in Star Trek for example the ‘warp drive’ uses the explosive reaction between matter and antimatter to propel the Starship Enterprise through space without fuel.
Initially antimatter sounds like a fantastic energy source, as when the particles hit matter they annihilate each other instantly, releasing their combined mass into 100 per cent energy. The problem is that there is hardly any antimatter available in the Universe. In fact, if you had the opportunity to annihilate in one go all the antimatter ever produced in the history of mankind, it wouldn’t release enough energy to boil a pot of tea!
Although not a good source of energy, antimatter does have its applications; for example, it is routinely used in hospitals for patient imaging. In positron emission tomography (PET) an electron and a positron (the anti-particle of the electron) are used to detect a radioactive nuclide in the body of the patient. This in turn tells clinicians about metabolic processes and is used as a diagnosis for certain brain diseases and cancers.
The real excitement of antimatter research is that it has the potential to rewrite our assumptions about nature and properties of space and time.
According to current scientific theories, every type of matter in the Universe created after the Big Bang should have been accompanied by equal amounts of antimatter (particles with the opposite charge), but this isn’t so. Scientists believe there may be subtle differences between the two types of matter that has allowed matter to wipe out antimatter and for the Universe to develop. We also have very limited understanding when it comes to the interaction of antimatter with the gravitational force - there has never been a detailed measurement of this phenomenon.
However, antimatter is difficult to investigate because when an antiparticle and a particle meet they annihilate each other, so a special trapping device is needed. We have been able to store antimatter inside vacuum vessels by using electromagnetic fields, but until now this has only been possible for a limited number of antiparticles and for a limited amount of time. In addition, so far these particles did not have the required beam characteristics – they should be very cold for precision measurements.
Now a new facility at CERN called ELENA (Extra Low ENergy Antiproton ring) is to provide high-quality cooled beams of antiprotons at much lower energies than what had previously been achieved. This facility will allow us to investigate some of the great unsolved problems in physics and AVA (Accelerators Validating Antimatter physics), a research network led by scientists at the University of Liverpool/Cockcroft Institute, will help provide the tools to do this.
For example an important element of ELENA is the electron cooler, which is required to make a very cold beam. Once they have been cooled, the particles can be injected into an ion trap where they will be almost at rest; this allows very precise measurements into their properties to be carried out. New cooling mechanisms are one of the research areas being studied within AVA.
All the industry partners involved in the AVA project are developing sensor technologies or advanced detector technologies. The challenge with antimatter in general is that there are a small number of tiny particles. They also cover an enormous range of energies.
Once our industrial partners have demonstrated that their technology is able to measure particles as exotic and challenging as antiprotons, these advances will find their way into other applications. For example, some of these detector technologies are expected to help increase the resolution and completeness of medical imaging.
There might be a discovery at ELENA that has similarly bold implications as the Higgs Boson; it may not be a new particle but instead may provide a much better understanding about some of the most fundamental processes in nature altogether. Who knows, maybe even midi-chlorians…?