A robotic interstellar mission carrying some number of frozen early stage human embryos is another theoretical possibility. This method of space colonization requires, among other things, the development of an artificial uterus , the prior detection of a habitable terrestrial planet , and advances in the field of fully autonomous mobile robots and educational robots that would replace human parents. Interstellar space is not completely empty; it contains trillions of icy bodies ranging from small asteroids Oort cloud to possible rogue planets.
There may be ways to take advantage of these resources for a good part of an interstellar trip, slowly hopping from body to body or setting up waystations along the way. Physicists generally believe faster-than-light travel is impossible. Relativistic time dilation allows a traveler to experience time more slowly, the closer his speed is to the speed of light. Upon return, there would be a difference between the time elapsed on the astronaut's ship and the time elapsed on Earth.
For example, a spaceship could travel to a star 32 light-years away, initially accelerating at a constant 1. After a short visit, the astronaut could return to Earth the same way. After the full round-trip, the clocks on board the ship show that 40 years have passed, but according to those on Earth, the ship comes back 76 years after launch. From the viewpoint of the astronaut, onboard clocks seem to be running normally. The star ahead seems to be approaching at a speed of 0. The universe would appear contracted along the direction of travel to half the size it had when the ship was at rest; the distance between that star and the Sun would seem to be 16 light years as measured by the astronaut.
At higher speeds, the time on board will run even slower, so the astronaut could travel to the center of the Milky Way 30, light years from Earth and back in 40 years ship-time. But the speed according to Earth clocks will always be less than 1 light year per Earth year, so, when back home, the astronaut will find that more than 60 thousand years will have passed on Earth.
Regardless of how it is achieved, a propulsion system that could produce acceleration continuously from departure to arrival would be the fastest method of travel. A constant acceleration journey is one where the propulsion system accelerates the ship at a constant rate for the first half of the journey, and then decelerates for the second half, so that it arrives at the destination stationary relative to where it began. If this were performed with an acceleration similar to that experienced at the Earth's surface, it would have the added advantage of producing artificial "gravity" for the crew.
Supplying the energy required, however, would be prohibitively expensive with current technology. From the perspective of a planetary observer, the ship will appear to accelerate steadily at first, but then more gradually as it approaches the speed of light which it cannot exceed. It will undergo hyperbolic motion.
From the perspective of an onboard observer, the crew will feel a gravitational field opposite the engine's acceleration, and the universe ahead will appear to fall in that field, undergoing hyperbolic motion. As part of this, distances between objects in the direction of the ship's motion will gradually contract until the ship begins to decelerate, at which time an onboard observer's experience of the gravitational field will be reversed.
When the ship reaches its destination, if it were to exchange a message with its origin planet, it would find that less time had elapsed on board than had elapsed for the planetary observer, due to time dilation and length contraction. All rocket concepts are limited by the rocket equation , which sets the characteristic velocity available as a function of exhaust velocity and mass ratio, the ratio of initial M 0 , including fuel to final M 1 , fuel depleted mass. Very high specific power , the ratio of thrust to total vehicle mass, is required to reach interstellar targets within sub-century time-frames.
Thus, for interstellar rocket concepts of all technologies, a key engineering problem seldom explicitly discussed is limiting the heat transfer from the exhaust stream back into the vehicle. A type of electric propulsion, spacecraft such as Dawn use an ion engine. In an ion engine, electric power is used to create charged particles of the propellant, usually the gas xenon, and accelerate them to extremely high velocities. By contrast, ion engines have low force, but the top speed in principle is limited only by the electrical power available on the spacecraft and on the gas ions being accelerated.
Nuclear-electric or plasma engines, operating for long periods at low thrust and powered by fission reactors, have the potential to reach speeds much greater than chemically powered vehicles or nuclear-thermal rockets. Such vehicles probably have the potential to power solar system exploration with reasonable trip times within the current century. Because of their low-thrust propulsion, they would be limited to off-planet, deep-space operation. With fission, the energy output is approximately 0. For maximum velocity, the reaction mass should optimally consist of fission products, the "ash" of the primary energy source, so no extra reaction mass need be bookkept in the mass ratio.
Based on work in the late s to the early s, it has been technically possible to build spaceships with nuclear pulse propulsion engines, i. This propulsion system contains the prospect of very high specific impulse space travel's equivalent of fuel economy and high specific power. Project Orion team member Freeman Dyson proposed in an interstellar spacecraft using nuclear pulse propulsion that used pure deuterium fusion detonations with a very high fuel- burnup fraction.
In each case saving fuel for slowing down halves the maximum speed. The concept of using a magnetic sail to decelerate the spacecraft as it approaches its destination has been discussed as an alternative to using propellant, this would allow the ship to travel near the maximum theoretical velocity. The principle of external nuclear pulse propulsion to maximize survivable power has remained common among serious concepts for interstellar flight without external power beaming and for very high-performance interplanetary flight.
In the s the Nuclear Pulse Propulsion concept further was refined by Project Daedalus by use of externally triggered inertial confinement fusion , in this case producing fusion explosions via compressing fusion fuel pellets with high-powered electron beams. Since then, lasers , ion beams , neutral particle beams and hyper-kinetic projectiles have been suggested to produce nuclear pulses for propulsion purposes.
A current impediment to the development of any nuclear-explosion-powered spacecraft is the Partial Test Ban Treaty , which includes a prohibition on the detonation of any nuclear devices even non-weapon based in outer space. This treaty would, therefore, need to be renegotiated, although a project on the scale of an interstellar mission using currently foreseeable technology would probably require international cooperation on at least the scale of the International Space Station. Another issue to be considered, would be the g-forces imparted to a rapidly accelerated spacecraft, cargo, and passengers inside see Inertia negation.
In theory, a large number of stages could push a vehicle arbitrarily close to the speed of light. Because fusion yields about 0. However, the most easily achievable fusion reactions release a large fraction of their energy as high-energy neutrons, which are a significant source of energy loss. Thus, although these concepts seem to offer the best nearest-term prospects for travel to the nearest stars within a long human lifetime, they still involve massive technological and engineering difficulties, which may turn out to be intractable for decades or centuries.
Although these are still far short of the requirements for interstellar travel on human timescales, the study seems to represent a reasonable benchmark towards what may be approachable within several decades, which is not impossibly beyond the current state-of-the-art. Based on the concept's 2. An antimatter rocket would have a far higher energy density and specific impulse than any other proposed class of rocket.
Speculating that production and storage of antimatter should become feasible, two further issues need to be considered. Second, heat transfer from the exhaust to the vehicle seems likely to transfer enormous wasted energy into the ship e. Even assuming shielding was provided to protect the payload and passengers on a crewed vehicle , some of the energy would inevitably heat the vehicle, and may thereby prove a limiting factor if useful accelerations are to be achieved. Rockets deriving their power from external sources, such as a laser , could replace their internal energy source with an energy collector, potentially reducing the mass of the ship greatly and allowing much higher travel speeds.
Geoffrey A. Landis has proposed for an interstellar probe , with energy supplied by an external laser from a base station powering an Ion thruster. A problem with all traditional rocket propulsion methods is that the spacecraft would need to carry its fuel with it, thus making it very massive, in accordance with the rocket equation. Several concepts attempt to escape from this problem:  . In , Robert W. Bussard proposed the Bussard ramjet , a fusion rocket in which a huge scoop would collect the diffuse hydrogen in interstellar space, "burn" it on the fly using a proton—proton chain reaction , and expel it out of the back.
Later calculations with more accurate estimates suggest that the thrust generated would be less than the drag caused by any conceivable scoop design. The limitation is due to the fact that the reaction can only accelerate the propellant to 0. Thus the drag of catching interstellar dust and the thrust of accelerating that same dust to 0. A light sail or magnetic sail powered by a massive laser or particle accelerator in the home star system could potentially reach even greater speeds than rocket- or pulse propulsion methods, because it would not need to carry its own reaction mass and therefore would only need to accelerate the craft's payload.
Robert L. Forward proposed a means for decelerating an interstellar light sail in the destination star system without requiring a laser array to be present in that system. In this scheme, a smaller secondary sail is deployed to the rear of the spacecraft, whereas the large primary sail is detached from the craft to keep moving forward on its own. Light is reflected from the large primary sail to the secondary sail, which is used to decelerate the secondary sail and the spacecraft payload.
Landis of NASA 's Glen Research center also proposed a laser-powered, propulsion, sail ship that would host a diamond sail of a few nanometers thick powered with the use of solar energy. A magnetic sail could also decelerate at its destination without depending on carried fuel or a driving beam in the destination system, by interacting with the plasma found in the solar wind of the destination star and the interstellar medium. The following table lists some example concepts using beamed laser propulsion as proposed by the physicist Robert L. Forward : .
The following table is based on work by Heller, Hippke and Kervella.
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Achieving start-stop interstellar trip times of less than a human lifetime require mass-ratios of between 1, and 1,,, even for the nearer stars. This could be achieved by multi-staged vehicles on a vast scale. Scientists and authors have postulated a number of ways by which it might be possible to surpass the speed of light, but even the most serious-minded of these are highly speculative. It is also debatable whether faster-than-light travel is physically possible, in part because of causality concerns: travel faster than light may, under certain conditions, permit travel backwards in time within the context of special relativity.
In physics, the Alcubierre drive is based on an argument, within the framework of general relativity and without the introduction of wormholes , that it is possible to modify a spacetime in a way that allows a spaceship to travel with an arbitrarily large speed by a local expansion of spacetime behind the spaceship and an opposite contraction in front of it.
A theoretical idea for enabling interstellar travel is by propelling a starship by creating an artificial black hole and using a parabolic reflector to reflect its Hawking radiation. Although beyond current technological capabilities, a black hole starship offers some advantages compared to other possible methods.
Getting the black hole to act as a power source and engine also requires a way to convert the Hawking radiation into energy and thrust. One potential method involves placing the hole at the focal point of a parabolic reflector attached to the ship, creating forward thrust.
A slightly easier, but less efficient method would involve simply absorbing all the gamma radiation heading towards the fore of the ship to push it onwards, and let the rest shoot out the back. Wormholes are conjectural distortions in spacetime that theorists postulate could connect two arbitrary points in the universe, across an Einstein—Rosen Bridge. It is not known whether wormholes are possible in practice.
Although there are solutions to the Einstein equation of general relativity that allow for wormholes, all of the currently known solutions involve some assumption, for example the existence of negative mass , which may be unphysical. The Enzmann starship, as detailed by G. Harry Stine in the October issue of Analog , was a design for a future starship , based on the ideas of Robert Duncan-Enzmann. The spacecraft itself as proposed used a 12,, ton ball of frozen deuterium to power 12—24 thermonuclear pulse propulsion units.
Twice as long as the Empire State Building and assembled in-orbit, the spacecraft was part of a larger project preceded by interstellar probes and telescopic observation of target star systems. Project Hyperion, one of the projects of Icarus Interstellar. NASA has been researching interstellar travel since its formation, translating important foreign language papers and conducting early studies on applying fusion propulsion, in the s, and laser propulsion, in the s, to interstellar travel. Landis of NASA's Glenn Research Center states that a laser-powered interstellar sail ship could possibly be launched within 50 years, using new methods of space travel.
Rockets are too slow to send humans on interstellar missions. Instead, he envisions interstellar craft with extensive sails, propelled by laser light to about one-tenth the speed of light. It would take such a ship about 43 years to reach Alpha Centauri if it passed through the system without stopping. Slowing down to stop at Alpha Centauri could increase the trip to years,  whereas a journey without slowing down raises the issue of making sufficiently accurate and useful observations and measurements during a fly-by.
The Year Starship YSS is the name of the overall effort that will, over the next century, work toward achieving interstellar travel. The effort will also go by the moniker YSS. The Year Starship study is the name of a one-year project to assess the attributes of and lay the groundwork for an organization that can carry forward the Year Starship vision. At the meeting of YSS, he reported using a laser to try to warp spacetime by 1 part in 10 million with the aim of helping to make interstellar travel possible. A few organisations dedicated to interstellar propulsion research and advocacy for the case exist worldwide.
These are still in their infancy, but are already backed up by a membership of a wide variety of scientists, students and professionals. The energy requirements make interstellar travel very difficult. It has been reported that at the Joint Propulsion Conference, multiple experts opined that it was improbable that humans would ever explore beyond the Solar System.
Cassenti, an associate professor with the Department of Engineering and Science at Rensselaer Polytechnic Institute, stated that at least times the total energy output of the entire world [in a given year] would be required to send a probe to the nearest star. Astrophysicist Sten Odenwald stated that the basic problem is that through intensive studies of thousands of detected exoplanets, most of the closest destinations within 50 light years do not yield Earth-like planets in the star's habitable zones. Moreover, once the travelers arrive at their destination by any means , they will not be able to travel down to the surface of the target world and set up a colony unless the atmosphere is non-lethal.
The prospect of making such a journey, only to spend the rest of the colony's life inside a sealed habitat and venturing outside in a spacesuit, may eliminate many prospective targets from the list. Moving at a speed close to the speed of light and encountering even a tiny stationary object like a grain of sand will have fatal consequences. Explorative high-speed missions to Alpha Centauri , as planned for by the Breakthrough Starshot initiative , are projected to be realizable within the 21st century. These probes would not be for human benefit in the sense that one can not foresee whether there would be anybody around on earth interested in then back-transmitted science data.
An example would be the Genesis mission,  which aims to bring unicellular life, in the spirit of directed panspermia , to habitable but otherwise barren planets. Unmanned missions not for human benefit would hence be feasible. The discovery sets a new record for greatest number of habitable-zone planets found around a single star outside our solar system.
All of these seven planets could have liquid water — the key to life as we know it — under the right atmospheric conditions, but the chances are highest with the three in the habitable zone. From Wikipedia, the free encyclopedia. This box: view talk edit. Main article: Interstellar probe. Main article: Generation ship. Main article: Sleeper ship. Main article: Embryo colonization. Main article: Time dilation. See also: Space travel using constant acceleration.
Main article: Nuclear pulse propulsion. Main article: Antimatter rocket. This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Main article: Faster-than-light. Main article: Alcubierre drive. Main article: Black hole starship. Main article: Enzmann starship. Spaceflight portal. Retrieved Journal of the British Interplanetary Society. Bibcode : JBIS J Astrophysical Journal. Bibcode : ApJ Acta Astronautica. Bibcode : AcAau.. NIAC Symposium.
Archived from the original PDF on 8 May Bentham Science Publishers. Yahoo News. December 18, Archived from the original on 4 December Centauri Dreams. Retrieved 12 June Near-lightspeed nano spacecraft might be close. The Physics of the Impossible. Anchor Books. Retrieved 12 April Progress in Astronautics and Aeronautics. Immersive VR visualization and interaction with data is relevant for scientific evaluation and also in the fields of training and education. It also allows an active interaction with the representations, e. We can walk through brains 25 , 26 or molecules, and we can fly through galaxies.
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Immersion in the data could take place alone or in a shared environment, where we explore and evaluate with others. The data could be static, or we could be immersed in dynamic processes. The data should be viewable in multiscale form. Three-dimensional representation of real or modeled data is important for understanding data and for decision-making following this understanding, a relevant topic for a number of fields, especially at this time of exponentially growing datasets.
Even when most of the analysis tools are computer-run algorithms, human vision is highly sensitive to patterns, trends, and anomalies van Dam et al. There is a substantial difference between looking at 3D data representations on a screen and being immersed in the data, navigating through it, interacting with it with our own body, and exploring it from the outside and the inside.
It is logical to expect that when VR commercial systems are pervasive, there will be a trend for currently used 3D data representations on a flat screen to be visualized in immersive media. This, along with the body-tracking systems, will allow a more natural interaction with the data. It is also important to identify ways to maximally exploit the potential of this data immersion capability.
Specific examples of VR for data visualization include molecular visualization and chemical design. In this version, participants were immersed into protein—ligand complexes. The system was evaluated by groups with experience in medical chemistry and drug design, and the study was focused on the improvement of the user-interaction with the molecules based on gestures and not in the evaluation of improved performance of drug design or specific tasks.
Out of 14 users, all of them found the system potentially useful for drug design, and they enjoyed using it, while none experienced motion sickness. A more specific task in interaction with molecules was tested by Leinen et al. In this study, a task of manipulating nanometer-sized molecular compounds on surfaces was tested under usual scanning probe microscopy versus immersive visualization through an Oculus Rift HMD.
The hand-controlled manipulation for extracting a molecule from a surface was improved by the visual feedback provided by immersive VR visualization: preestablished 3D trajectories were followed with higher precision, and deviations from them were better controlled than in immersive than in non-immersive systems Leinen et al. Moving from the nanoscale to the microscale, a specific task consisting of the evaluation of the spatial distribution of glycogen granules in astrocytes glial cells, a type of brain cells was evaluated in an immersive environment in a Cave-like system Cali et al.
A set of procedures and software was developed to allow such immersive reconstruction. The distribution of glycogen granules initially appeared to have a random distribution, but they were discovered to be grouped into clusters of various sizes with particular spatial relationships to specific tissue features.
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The authors found the immersive evaluation of the 3D structure to be pivotal to identify such non-random distribution Cali et al. The use of an interactive VR room also allowed multiple users to share and discuss the evaluation of the cellular details. In this study there were, however, no comparisons between task performance across different display media. A comparison across three different media — 3D reconstructions rendered on 1 a monoscopic desktop display, 2 a stereoscopic visual display on a computer screen fishtank , and 3 a Cave-like system — was carried out by Prabhat et al.
In this study, confocal images of Drosophila data: the egg chamber, the brain, and the gut, were evaluated by subjects who had to describe or quantify specific features mostly related to spatial distribution or colocalization and geometrical relationships. A more immersive environment was preferred qualitatively by subjects, and task performance was also superior. Immersive VR is of great value for surgery training, an aspect that is developed in Section 2.
Visualization of the human body from an immersive perspective can provide medical students an unprecedented understanding of anatomy, being able to explore the organs from micro to macro scales. These projects are generating detailed multiscale and multidimensional information about the brain. Immersive VR will have a role in the visualization of these brain reconstructions or of the simulations built based on the experimental data.
The Blue Brain Project predecessor of the Human Brain Project has already generated a full digital reconstruction of a rat slice of somatosensory cortex with 31, neurons based on real neurons, and 37 million synapses Markram et al. This simulation generates patterns of neuronal activity that reproduce those generated in the brain and is amenable of immersive exploration into the structure and function of the brain. Considering now a larger spatial scale, astronomical visualization in immersive VR has also been explored, both for professional and educational purposes Schaaff et al.
These authors represented high-resolution simulations of re-ionization of an Isolated Milky Way-M31 Galaxy Pair, with various different representations. It is interesting for education that information can be added to the immersive displays. There is an exciting perspective in the scientific and data visualization area that will open new doors to our understanding. It will be important to evaluate the extent to which immersion and interaction with data results in a more thorough, intuitive, and profound understanding of structures and processes. But in any event, once this route is open, visualization of 3D models on a flat screen will feel like watching Star Wars on a small black and white TV see Presentation S1 in Supplementary Material.
VR and the detailed human body scans that now exist make this possible of course in virtual reality. McGhee et al. The area of application of VR in education is vast. For recent reviews, see Abulrub et al. There are several reasons why VR is an excellent tool for education. First, it can change the abstract into the tangible. This could be especially powerful in the teaching of mathematics.
For example, Hwang and Hu suggest that the use of a collaborative virtual environment has advantages for students learning geometrical concepts compared to traditional paper and pencil learning. However, it is not completely clear which type of VR system was used, although it appears to be of the desktop variety.
Kaufmann et al. They provide anecdotal evidence for the effectiveness of the method. Quantitative analysis of the results found no advantage to any system. A detailed qualitative analysis, however, suggested that the passive VR condition tended to foster a reflective process among the children, and great enjoyment in interacting with the robot, associated with better understanding.
One example of this is surgical training see Section 2. Indeed, a European consensus program for endoscopic surgery VR training has been designed and agreed van Dongen et al. For an example in engineering learning see Ewert et al. The third advantage is that it can substitute methods that are desirable but practically infeasible even if possible in reality. For example, if a class needs to learn about Niagara Falls 1 week, the Grand Canyon the next, and Stonehenge 35 the week after, it is infeasible for the class to visit all of those places. Yet, virtual visits are entirely possible, and such environments have been under construction Lin et al.
It has certainly been suggested that immersive VR will change the nature of field trips, 36 and although there have been plenty of inventive demonstrations 37 , 38 , 39 it seems that as yet there have been no studies of the effectiveness of this, although perhaps it is so obviously advantageous that formal studies may be unnecessary. The fourth advantage of VR in education involves breaking the bounds of reality as part of exploration. For example, changing how activities such as juggling would be if there was a small change in gravity, or how it would be to ride on a light beam, a universe where the speed of light were different.
These ideas were envisaged and implemented for VR by Dede et al. In this article, we have emphasized that the real power of VR is that it enables approaches that go beyond reality in a very fundamental way — more than just exploring strange physics. An example of this in the field of education was provided by Bailenson et al.
In a collaborative virtual environment, it is possible to arrange the virtual classroom so that every student is at the center of attention of the teacher, and where the teacher has feedback about which students are not receiving enough eye gaze contact. Additionally, virtual colearners who could be either model students or distracting students can influence learning, and the results overall showed that these techniques do improve educational outcomes. Overall, for the reasons we have given, and no doubt others, VR is an extremely promising tool for the enhancement of learning, education, and training.
We have not mentioned other possibilities such as music or dance, or various dexterous skills, but for these areas VR has clearly great potential. Within the area of VR for training, surgical training has been a thoroughly investigated field Alaraj et al. The use of simulations in surgical planning, training, and teaching is highly necessary. To give an illustrative example of why VR is necessary for surgery: interventional cardiology has currently no other satisfactory training strategy than learning on patients Gallagher et al.
It seems that acquiring such training on a virtual human body would be a better option. In the training of medical students and in particular of surgeons, there is a relevant potential role for VR as a tool to learn anatomy through virtual 3D models. Even though there are studies trying to evaluate how useful VR can be to improve the learning of anatomy Nicholson et al.
Most of the 3D models used so far are for screen displays. Still, even the visualization of non-immersive 3D body models to study anatomy yields good results for learning, and therefore this is an area that should expand in the future, integrating fully immersive systems and different forms of manipulation and interaction of the trainees with the body models.
However, the revolution has not happened yet, although the field is now ready for this possibility. Surgical training in VR requires a combination of haptic devices and visual displays. Haptic devices transmit forces consisting of both the forces exerted by the surgeon and a simulation of the forces and resistances of the various body tissues. A critical question is whether the skills acquired in a virtual training are successfully transferred to the real world of surgery. Seymour et al. These results are likely to improve with a more immersive system.
To illustrate the value given to surgical training in VR, an FDA panel voted in August to make VR simulation of carotid stent placement an important component of training. The most common uses so far of VR for surgical training have been those of laparoscopic procedures Seymour et al. In general terms, a large number of studies — out of which only a few seminal ones are cited here — coincide in finding positive results of VR training.
Most of the systems mentioned above concentrate on the local surgical procedure, e. The response of the surgical team to these situations will be critical for the well-being of the patient, and immersive VR should be an optimal frame for such training. VR can embed the specific surgical procedure, for example, the placement of the carotid stent, into various contexts and under a number of emergency situations. In this way, during training, not only the contents but also the skills and the experience of being in a surgery room for many years can be transmitted to the trainees, which can include not only surgeons but all the sanitary personnel, each in their specialized roles.
There is a huge explosion of research in the effectiveness of VR-based training for surgery including meta-analyses and reviews Al-Kadi et al. This is likely to be a field that expands considerably. Here, we broadly address issues relating to physical training and improvement through sports and exercise, an area of growing interest to professional sports. Of course this is now possible 40 and is certain to be readily available in the near future.
For example, a version has been implemented using two powerwall displays plus tracking for each player Li et al. However, the opponent need not be a remote player in a shared VR but may be a virtual character. Immersive VR, at least with hand tracking if not full body tracking, has ideal characteristics for playing table tennis or other competitive sports, with the possible advantage of not having to spend time traveling to the gym.
There are several areas where VR can provide useful advantage for sport activities. First, for leisure and entertainment reasons — such as the table tennis example above. Second, for learning, training, and rehearsal. To the extent that VR supports natural sensorimotor contingencies at high enough precision, it could be used for these purposes.
However, here it would be important to carry out rigorous studies to check in case small differences between the VR version and the real version might lead to poor skills transfer, or incorrect learning. For example, learning to spin or slam in table tennis requires very fine motor control depending on vision, proprioception, vestibular feedback, tactile feedback, force feedback, even the movement of air, and the sound of the ball hitting the table and the bat.
Hence, to build a virtual table tennis that is useful for skill acquisition or improvement must take into account all of these factors, or the critical ones if these are known. On the other hand, virtual table tennis could be thought of as a game in its own right and nothing much to do with the real thing. In this case, virtual table tennis would fall under the first category — entertainment and leisure.
Additionally, as we will see in Section 6. Similarly, even without being able to reproduce all the fine detail necessary for the transfer of training skills to reality, VR may be useful in team sports to plan overall strategy and tactics. A third utility of VR in sports is for rehabilitation following injury. We will briefly consider some of these areas. In a comprehensive review of VR for training in ball sports Miles et al. The review points out several inevitable hurdles that must be overcome.
For example, in training for field games such as American Football or soccer, the area of play is huge compared to the effective space in which someone in a VR system can typically move. A play on a field may involve running 25 m, whereas the effective area of tracking is say 2 m around a spot where the participant in VR must stand. Clearly, using a Wand to navigate or even a treadmill may miss critical aspects of the play see also Section 2.
The paper reports many such pitfalls that need to be overcome and points out that studies have been inconclusive and therefore, there is the need for more research. Craig reviews how VR might be used to understand perception and action in sport. She argues that VR offers some clear advantages for this and gives a number of examples where it has been successful, as well as pointing out problems. However, she wonders why if it is successful it has not been widely used in training up to now, but where there is reliance on alternatives such as video.
She points out that one problem has been cost, though this is likely to be ameliorated in the near term. A second problem is to effectively and differentially meet the needs of players and coaches, pointing out how VR action replays could be seen from many different viewpoints, including those of the player and of the coach so that different relevant learning would be possible. Another advantage of VR would be to train players to notice deceptive movements in opponents, by directing attention to specific moves or body parts that signal such intentions. However, she points out as mentioned above how it is critical to provide appropriate cues to avoid mislearning.
Ruffaldi et al. Rauter et al. This was a Cave-like system enhanced with auditory and haptic capabilities, an earlier version described in von Zitzewitz et al. Their study, carried out with eight participants, compared skill acquisition between conventional training on water, with training in the simulator. Examining the differences between the two they concluded that both with respect to questionnaire and biomechanical responses that the methods were similar enough for the simulator to be used as a complementary training tool, since there was sufficient and appropriate transfer of training using this method.
Wellner et al. The novelty was that they added a virtual audience to test the idea that the presence of an audience would encourage the rowers in a competitive situation. They did not find a notable outcome in this regard, only the relatively high degree of presence felt by the participants. On similar lines, Wellner et al. In spite of null results, it is important to note how VR affords the possibility to experiment with such factors that would be possible, but logistically very difficult to do in reality.
Another example of this use of VR that is logistically very difficult to do otherwise is for spectators to attend sports matches when they cannot physically attend e. Instead, they can view them, as if they were there — and have the excitement of seeing the game life-sized, first hand, and among a crowd of enthusiasts. Kalivarapu et al. They concluded that the Cave and HMD experiences gave the participants greater opportunity to interact i. Participants nevertheless experienced a greater degree of realism in the Cave, perhaps not surprising because of its greater resolution and several orders of magnitude greater cost.
On the whole, the HMD and Cave produced similar results across a number of aspects of presence. There have been many other applications of VR in sports — impossible to cover all of them here — for example, a baseball simulator, 46 for handball goalkeeping Bideau et al. It is well known that aerobic exercise is extremely good for us, especially as we age.
A meta study of research relating to older adults carried out by Colcombe and Kramer showed that there is a clear benefit for certain cognitive functions. A more recent survey by Sommer and Kahn again showed the benefits of exercise for cognition for a variety of conditions. Yu et al. However, repetitive exercise with aerobic benefits can be boring; indeed, Hagberg et al. Virtual reality opens up the possibility of radically altering how we engage in exercise. Instead of just being on a stepping machine watching a simple 2D representation of a terrain, we can be walking up an incline on the Great Wall of China, or walking up the steps in a huge auditorium where we are excitedly going to watch a sports game, or even walking up steps to a fantasy castle in a science fiction scenario.
Instead of just riding an exercise bike, we can be cycling through the landscape of Mars. Moreover, other motivational factors can be introduced such as virtual competitors as we saw in the rowing example above. Anderson-Hanley et al. Finkelstein and Suma used a three-walled stereoscopic display and upper body tracking of participants who had to dodge virtual planets flying toward them. They found that the method produces increased heart rate i. Mestre et al. They found that the addition of music was beneficial both psychologically for motivation and pleasure and behaviorally.
They were interested in testing among other things whether such cycling would improve executive function. They found that cognitive function was improved among the cybercyclers, and that it was likely that it would help to prevent cognitive decline compared to traditional exercise. Overall, while there has been significant work in this area, a systematic review carried out by Bleakley et al. It is one thing to be cycling or walking on a treadmill or exercise steps while looking at a screen, since this is anyway the case with most exercise machines even though the display may be very simplistic.
Since the exerciser is not actually moving through space, looking at a screen should be harmless. However, it is not obvious that the same activities could be safely or successfully carried while people are wearing an HMD, which not only obscures their vision of the real world but may also lead to a degree of nausea — which is all the more likely to occur while moving through virtual space.
Shaw et al. First, to overcome the problem of possible sickness; second, to have reliable tracking of the body; third to deal with health and safety aspects; fourth the choice of player visual perspective; and fifth, the problem of latency. They described a system that was designed to overcome these problems, that used an Oculus DK2 HMD, and which was evaluated in an experimental study Shaw et al.
They compared three setups: a standard exercise bike with no feedback, the exercise bike with an external display, and the bike with the HMD. The fundamental findings were that on several measures calories burned, distance traveled the two feedback systems outperformed the bike only condition but did not differ from each other.
The two systems with feedback were also evaluated as more enjoyable than the bike only, and the HMD was more enjoyable and was associated with greater motivation than the external display system. Only 4 out of 26 reported some minor symptoms of simulator sickness. As the authors pointed out, the study was limited, since the participants were almost all males, and with limited age range, and it is not known how well these results would generalize.
Bolton et al. There are several other applications without associated papers such as RiftRun 53 where participants run on the spot to virtually run through an environment. Whether these are successful or not will obviously depend on consumer uptake. Finally, as in other applications, we emphasize that VR allows us to go beyond what is possible in reality. Even cycling through Mars is just cycling. It is physically possible, if highly unlikely to be realized. Perhaps though there are fundamentally new paradigms that can really exploit the power of VR — the virtual unreality that we mentioned in the opening of this article.
One approach is to use VR to implicitly motivate people toward greater exercise rather than as a means to carry out the exercise itself. Participants at various points were required to carry out physical exercises or not. While they did not carry out these exercises the body of their virtual doppelganger became fatter, and while they did the exercises the virtual body became thinner.
The dependent variable was the amount of voluntary exercise that participants carried out in a final phase of the experiment during which there was also positive and negative reinforcement. It was found that the greatest exercise was carried out by the group that had the positive and negative reinforcement. In order to check that it was the facial likeness that accounted for this result, a second experiment introduced another condition, which was that the face of the virtual body was that of someone else. Here, the result only occurred for the condition of the virtual doppelganger.
The setup was that they saw their doppelganger exercising on a treadmill, or a virtual character that did not look like themselves exercising, or a condition where their doppelganger was not doing any exercise but just standing around. The results suggested that those who saw their virtual look-alike exercising did carry out significantly more exercise in the real world in a period after the experiment than the other two conditions.
A second approach might be to use VR to provide a surrogate for exercising, rather than providing a motivation to exercise physically in reality. Kokkinara et al. Participants who were seated wearing an HMD and unmoving except for their head saw from 1PP their virtual body standing and carrying out walking movements across a field. They saw this when they looked down directly toward their legs that would be walking, and also in a shadow. In another condition they saw the body from a 3PP. After experiencing this virtual walking for a while they approached a hill, and the body walked up the hill.
In the embodied 1PP condition participants had a high level of body ownership and agency over the walking, compared with the 3PP condition. More importantly, for this discussion, while walking up the hill participants had stronger skin conductance responses more sweat and greater mean heart rate in the embodied condition, compared to a period before the hill climbing, which did not occur for those in the 3PP.
There were 28 participants each of whom experienced both conditions there was another factor, but it is not relevant to this discussion. Although there are caveats for both of these studies, the important aspect for our present purpose is that they illustrate how VR might be used to break out of the boundaries of physical reality and achieve useful results through quite novel paradigms. Of course it must always be better to carry out actual physical exercise rather than relying on your virtual body to do it for you. Yet sometimes, for example, on a long flight, virtual exercise might be the only possibility.
There are many areas of social interaction between people where it is important to have good scientific understanding. What factors are involved in aggression of one group against another, or in various forms of discrimination? Which factors might be varied in order to decrease conflict, improve social harmony? It is problematic to carry out experimental studies in this area for reasons discussed below. However, immersive VR provides a powerful tool for the simulation of social scenarios, and due to its presence-inducing properties can be effectively used for laboratory-based controlled studies.
Similarly, away from the domain of experiments, there are many aspects of our cultural heritage that people cannot experience — how an ancient site might have looked in its day, the experience of being in a Roman amphitheater as it might have been at the time, and so on. Again, VR offers the possibility of direct experience of such historical and cultural sites and events.
In this section, we consider some examples of the application of VR in these fields, starting first with social psychology. Loomis et al. Here, the potential benefits are enormous. First, studies that are impossible in reality for practical or ethical reasons are possible in VR. Second, VR allows exact repetition of experimental conditions across all trials of an experiment. Moreover, virtual human characters programed to perform actions in a social scenario can do so multiple times.
This is not possible with confederates or actors, who can become tired and also have to be paid. Although it is costly to produce a VR scenario, once it is done, it can be used over and over again. Also, the scenarios can be arbitrary rather than restricted to laboratory settings.
Rovira et al. The first refers to the possibility of valid experimental designs including issues such as repeatability across different trials and conditions, the precision at which outcomes can be measured, and so on. The second refers to generalizability. For example, in a study of the causes of violence, VR can place people in a situation of violence, which cannot be done in a real-life setting.
This means that there is the possibility of generalization of results out of the laboratory to what may occur in reality. In particular, VR can be used to study extreme situations that are ethically and practically impossible in reality. This relies on presence — PI and Psi — leading to behavior in VR that is sufficiently similar to what would be expected in real-life behaviors under the approximately the same conditions. In the sections below, we briefly review examples of research in this area. How do you feel when a stranger approaches you and stands very close?
Proxemics is the study of interpersonal distances between people, discussed in depth by Hall He defined intimate, personal, social, and public distances that people maintain toward each other and these distances may be culturally dependent. An interesting question is the extent to which these findings also occur in VR.
If a virtual human character approaches and stands close to you, in principle this is irrelevant since nothing real is happening — there is no one there. Even if the character represents a physically remote actual person who is in the same shared virtual environment as you, they are not really in the same space as you, and therefore not close. We briefly consider proxemics behavior in VR because it is a straightforward but fundamental social behavior, and finding that the predictions of proxemics theory hold true for VR is a foundation for showing that VR could be useful for the study of social interaction.
There has not been a great deal of work on this topic that has exploited VR. Bailenson et al. This work was continued in Bailenson et al. Participants also moved away when virtual characters approached them. Readers might be wondering — so what? This is obvious. It has to be remembered though that these are virtual characters, no real social interaction is taking place at all. Further studies have shown that proxemics behavior tends to operate in virtual environments Guye-Vuilleme et al. McCall et al. Subsequently, participants engaged in a shooting game with those virtual characters.
It was found that there was a positive correlation between the distance maintained from the characters in the first phase and the degree of aggression exhibited toward them in the second phase but only for the condition where both virtual characters were Black. Llobera et al.
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This was to test the finding of McBride et al. It was found that there was a greater skin conductance response as a function of the closeness to which the characters approached participants and the number of characters simultaneously approaching. However, it was found that there was no difference in these responses when cylinders were used instead of characters. It was suggested that skin conductance cannot differentiate between the arousal caused by characters breaking social distance norms and the arousal caused by fear of collision with a large object the cylinder moving close to the participants.
Kastanis and Slater showed how a reinforcement learning RL agent controlling the movements of a virtual character could essentially learn proxemics behavior in order to realize the goal of moving the participant to a specific location in the virtual environment. Participants in an immersive VR saw a male humanoid virtual character standing at a distance and facing them.
Every so often the character would walk varying distances toward the participant, walk away from the participant, or wave for the participant to move closer to him. The long run aim was to get the participant to move far back to this target, unknown to the participant herself. The RL eventually learned that if its character went very close to the participant, then the participant would step backwards. Moreover, if the character was far away then it sacrificed short-term reward by simply waiving toward the participant to come closer to itself, because then its moving forwards action would be effective in moving the participant backwards.
Hence, the RL relied on presence the participant moving back when approached too close — from the prediction of proxemics theory and learned how to exploit this proxemics behavior to achieve its task. For all participants, the RL learned to get the participant back to the target within a short time. This method could not have worked unless proxemics occurred in the VR.
Having shown that this is the case we move on to more complex social interaction. For example, we saw earlier how simply placing White people in a Black body in a situation known to be associated with race discrimination led to an increase in implicit racial bias Groom et al. On the other hand, virtual body representation has been shown to be effective with respect to racial bias, where White people embodied in a Black-skinned body show a reduction in implicit racial bias Peck et al.
More generally, the method of virtual embodiment has also been used to give adults the experience of being a child Banakou et al. Some of the work in the area of body representation applied to implicit bias is reviewed in Slater and Sanchez-Vives and Maister et al. Although not in the context of discrimination there is some evidence from the work of Ahn et al. They immersed people with normal vision into an HMD-delivered VR where they experienced certain types of color blindness.
It illustrates how VR might be used to put people experientially in situations and how this may influence their behavior compared with only imaginal techniques. Stanley Milgram carried out a number of experiments in the s designed to address the question of how events such as the Holocaust could have occurred Milgram, He was interested in finding explanations of how ordinary people can be persuaded to carry out horrific acts.
The type of experiments that he conducted involved experimental subjects giving apparently lethal electric shocks to strangers. These are a very famous experiments that are as topical today as in the s, and barely a week goes by when there is not some mention of it in news media, 57 or further research relating to it is reported. Typically, the experimental subject, normally recruited from the local town near Yale University rather than from among psychology students, were invited to the laboratory where he or she met another person, also supposedly recruited in the same way.
The other person was in fact a confederate of the experimenter, an actor hired for the purpose, this being unknown to the subject. The experimenter invited the subject and the actor to draw lots to determine their respective roles in the experiment. It turned out that the subject was to play the role of Teacher, and the actor the role of Learner, but the outcome of this draw was fixed in advance. Then both the Teacher subject and Learner actor were taken to another room, where the Learner had electrodes placed on his body connected to an electric shock machine. It was explained that the idea was to examine how punishment might aid in learning.
The Learner was to learn some word-pair associations, and whenever he gave a wrong answer he was to be shocked. The Learner was left in the room, and the experimenter took the Teacher back into the main laboratory, closing the door to that room. He explained to the Teacher that he had to read out cues for the word-pair tests and whenever the Learner gave the wrong answer the Teacher should increase the voltage on a dial and administer an electric shock at that voltage.
During the course of the experiment, a tape was played giving the responses of the Learner. With the low voltage shocks there was no response. He shouted that he wanted to be let out of the experiment, and finally with the strongest shocks he became completely silent. Participants generally found that the experience was extremely stressful, and even if they continued through to lethal voltages they were clearly very upset.
Prior to the experiment, Milgram had asked a number of psychologists about how many people would go all the way and administer even lethal voltages to the Learner. The view was that only a tiny minority of people, those with psychopathic tendencies, would do so. The results stunned the world since it apparently showed that ordinary people could be led to administer severe pain to another at the behest of an authority figure.
There is a wealth of data and analysis and a description of many different versions of this experiment in Milgram , but the basic conclusion was that people will tend to obey authority figures. Here, ordinary people were being asked to carry out actions in a lab in a prestigious institution Yale University and in the cause of science. They tended to obey even if they found that doing so was extremely uncomfortable. Although this is not the place for discussion of this interpretation, interested readers can find alternative explanations for the results in, for example, Burger ; Miller ; Haslam and Reicher ; and Reicher et al.
Participants in these experiments were deceived — they were led to believe that the Learner was really just another subject, a stranger, and that he was really receiving the electric shocks. The problem was not so much the stress, but that fact that participants were not informed about what might happen, were not aware that they may be faced with an extremely stressful situation, and were ordered to continue participating even after they had clearly expressed the desire to stop.
These and other issues led to strong criticism from within the academic community that eventually led to a change in ethical standards — informed consent, the right to withdraw from an experiment at any moment without giving reasons, and care for the participants including debriefing. See also a discussion of these issues as they relate to VR in Madary and Metzinger Hence, these experiments on obedience, no matter how useful, cannot be carried out today for research purposes, no matter how valuable they might seem to be scientifically. Yet, the questions addressed are fundamental since it appears that humans may be too ready to obey the authority of others even to the extent of committing horrific acts.
In , a virtual reprise of one version of the Milgram experiments was carried out Slater et al. The approval was given because participants were warned in advance about possible stress, could leave the experiment whenever they wanted, and of course they knew for sure that no one in reality was being harmed because in this experiment the Learner was a poorly rendered virtual female character displayed in a Cave-like VR setting.
They saw the virtual Learner on the other side of a virtual partition, projected in stereo on the front wall of the Cave. Just as in the original experiment, after a while she began to complain and demanded to be let out of the experiment, and eventually seemed to faint. However, if participants expressed a wish to stop, no argument against this was given, and they stopped immediately. Even though carried out in VR, many of the same results as the original were obtained, though at a lower level of intensity of stress.
All those who communicated by text gave all of the shocks. However, 6 of the 23 who saw and heard the Learner withdrew from the experiment before giving all shocks. In the paper, it was argued that the gap between reality and VR makes these types of experiments possible. Presence PI and Psi leads to participants tending to respond to virtual stimuli as if they were real. But, on the other hand, they know that it is not real, which can also dampen down their responses. In VR, we see that they responded similarly, though not with the very strong and visible stress that many of the original participants displayed.
Using VR, we can study these types of events, and how people respond to them, and construct predictive theory that may help us understand how people might respond in reality. The predictions can then be tested against what happens in naturally occurring events and the theory examined for its viability. This type of approach can also be used to gather real-time data about brain activity of people when faced with such a situation Cheetham et al.
You are in a bar or other public place and suddenly a violent argument breaks out between two other people there. It seems to be about something trivial. One man is clearly the perpetrator, and the victim is trying to calm down the situation, but his every attempt at conciliation is used by the perpetrator as a cue for greater belligerence.
Eventually the perpetrator starts to physically assault the victim. What do you do? Suppose you are alone there? Suppose there are other people? Perhaps the victim shares some social identity with you, such as being a member of the same club or same ethnic group different to that of the aggressor.
How do you respond? Do you try to intervene to stop the argument? Or walk away? How is your response influenced by these factors such as number of other bystanders or shared social identity with the victim or aggressor? This area of research was initiated in the late s provoked by a specific incident when apparently 38 bystanders observed a woman being murdered and did nothing to help.
However, other researchers have also suggested the importance of social identity as a factor, the perceived relationships between the people involved, for example, see Reicher et al. There is a meta-analysis and review of the field by Fischer et al. As pointed out by Rovira et al. This is very similar to the situation of the Obedience studies discussed above. Instead, researchers have to study surrogates such as the responses of people to someone falling Latane and Rodin, or responses to an injured person laying on the ground Levine et al. However, these are not violent emergencies so that it may not be valid to extrapolate results from such scenarios to what might happen in actual violent emergencies.
In VR it is possible to set up simulated situations, where we know from presence research that people are likely to react realistically to the events portrayed. King et al. A possible problem though with using video games is that they do not mobilize the body — there are no natural sensorimotor contingencies so that PI becomes something at best imaginal. In some applications this may not be important. Garcia et al. Hence, it might be the case that video games are mainly aids to imagination and that results obtained from video games might be the same as those from imagination.
Indeed, a result from Stenico and Greitemeyer suggests that this might be the case. This is not to say that such results are invalid but that by themselves they are not convincing enough, and some experimental evidence is needed that does place participants into the midst of a violent emergency so that various factors influencing their responses can be investigated. But, as we have said this cannot be done both for practical and above all ethical reasons. The method to foster social identity with a virtual human character was through the use of soccer club affiliation.
They were in a virtual bar where they had an initial conversation with a life-sized male virtual character V. After a while of this conversation another character P — also wearing a generic soccer shirt but not Arsenal — butted in and started to attack V especially because of his support of Arsenal. This attack increased in ferocity until after about 2 min it became a physically violent attack.
It was found in accordance with social identity theory that those in the group where V was an enthusiastic Arsenal supporter intervened much more than those in the other group. There was a second factor, which was whether or not V occasionally looked toward the participant during the confrontation, but this had no effect. However, there was a positive correlation between the number of interventions and the extent to which participants believed that V was looking toward them for help — but only in the ingroup condition.
Since it is impossible to compare these results with any study in real life, of course their validity in the sense of how much they would generalize to real-life behavior cannot be known. However, experiments such as these generate data and concomitant theory, which can be compared in a predictive manner with what happens in real-life events. In fact, there is no other way to do this other than the use of actors — which as mentioned earlier can run into ethical and practical problems.
Moreover, the knowledge gained from such experiments can be used also in the policy field, for example, providing advice to victims on how to maximize the chance that other people might intervene to help them, or of use to the emergency or security services on how to defuse such a situation. Its diverse manifestations — from our cherished historic monuments and museums to traditional practices and contemporary art forms — enrich our everyday lives in countless ways. Heritage constitutes a source of identity and cohesion for communities disrupted by bewildering change and economic instability.
The preservation of the cultural heritage of a society is considered as a fundamental human right, and there is a Hague Convention on the protection of cultural property in the event of armed conflict. The ideal way to preserve cultural heritage is physical protection, preservation, and restoration of the sites.
The first and obvious application of VR in this field is to allow people all over the world to virtually visit such sites and interactively explore them. This is no different from virtual travel or tourism, except for the nature of the sight visited. This is also possible through museums that have VR installations. The second is digitization of sites for future generations, and especially those that are in danger of destruction either through factors such as environment change or conflict.
The third type of application is to show how these sites might have looked fully restored in the past and under different conditions such as lighting conditions. For example, it is quite different to see the interior of a building or a cave with electric lighting than under the original conditions that the inhabitants of that time would have seen them — by candlelight or fire.
The fourth is to see how sites, both cultural heritage and non-cultural heritage sites might look in the future, under different conditions such as under different global warming scenarios. This is a massive field and mainly concerned with digitization, computer vision, reconstruction, and computer graphics techniques. Here, we give a few examples of some of the virtual constructions that have been done and that potentially could be experienced immersively in VR. An example of one type of application is described by Gaitatzes et al. Apart possibly from the last issue, each of these problems is largely overcome with the advent of low-cost, high-quality HMDs with built-in head tracking.
Of course it is still true that an interdisciplinary team is required to create the environments, although see Wojciechowski et al. In particular, digital acquisition and rendering of cultural heritage sites requires a huge amount of data to be processed. An example of how this was handled for the site of the Monastery of Santa Maria de Ripoll in Catalonia, Spain, is presented in Besora et al. The David statue 72 required 2 billion polygons for its representation, and the software is available as freeware from Stanford.
Sometimes a digital reconstruction is the only way to view a site. The ancient Egyptian temple of Kalabsha was physically moved in its location to preserve it from rising flood waters. Sundstedt et al. Gutierrez et al. Happa et al. Many examples of virtual cultural heritage in the past have been implemented for desktop or projection systems — though of course they could always be displayed immersively in HMDs. However, this raises other issues such as appropriate tracking, interfaces, and so on. A joystick for navigation, for example, is not always appropriate for an HMD especially bearing in mind that movement without body action can sometimes be a cause of simulator sickness.
Also a screen display has the advantage that typically it can be much higher resolution than what is possible in an HMD, where all the detailed lighting and detail rendering might not even be perceivable. Webel et al. They point out how traditional systems, such as tracking, requiring the wearing of devices, and expensive Caves are not always suitable for busy environments such as museums.
However, low—cost, camera-based tracking systems do not require physical contact with visitors, and the use of the Oculus Rift HMD in their application allowed visitors to look around the virtual environment simply by turning their head rather than learning a joystick type of navigation method. In other words, these systems provide a natural means of interaction. The natural camera control just by turning the head, like one would do in the real world, lets users control this aspect without even thinking about it.
The combination with natural interaction inputs with the Kinect or the Leap Motion enables the user to directly interact with the virtual world. Kateros et al.
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