Tunnelling under the Thames
The first tunnel ever to be built under a major river was the tunnel under London's River Thames
At the beginning of the 19th century, the port of London was the busiest in the world. Cargoes that had travelled thousands of miles and survived all the hazards of the sea were unloaded on the banks of the Thames, only for their owners to discover that the most frustrating portion of their journey lay ahead. Consignments intended for the southern parts of Britain had to be lifted onto horse carts, pulled through the docks and across London Bridge, built in the 12th century and as impractical as its early date implies. By 1820, London Bridge had become the centre of the world's largest traffic jam.
It was an intolerable situation, and it was clear that if private enterprise could build another crossing closer to the docks, there would be good money to be made in tolls paid by users. Another bridge was out of the question, as this would deny sailing ships access to the city centre and ambitious men turned their thoughts to tunnelling beneath the Thames instead. This was not such an obvious idea as it might appear. Although increasing demand for coal had meant a great many tunnels had been dug in mines in Britain, working methods remained primitive. Tunnels were dug by men with simple tools, by candlelight. However, in 1807, a group of businessmen set themselves up as the Thames Archway Company. Their ambition was to tunnel below the Thames, but there was little to guide them as there had been no previous attempt to do this. Their chief engineer was Richard Trevithick, designer of the world's first high-pressure steam engine. His men made progress at the beginning, but then things began to go disastrously wrong, with muddy soil pouring into the tunnel. Eventually, the Thames Archway Company had had enough. Its funds were exhausted, Trevithick was sick from exposure to the river water, and its efforts had proved only that a passage under the river exceeded the limits of contemporary mining technology.
At that time, the only machines used in mines were pumps. It took a man of genius to recognise that a different sort of machine was needed, a machine that could prevent the roof and walls of a tunnel from collapsing. This man was Marc Brunel, a Frenchman who had become one of the most prominent engineers in Britain. Not long after the failure of the Thames Archway Company, Brunel saw a rotten piece of wood lying on the riverbank. Examining the wood through a magnifying glass, he observed it was infested with something that looked like a worm. Brunel realised that as it tunnelled through the wood, it would push chewed wood into its mouth and digest it, then excrete a hard substance that lined the new tunnel. Brunel realised that the worm's digging technique could be adapted to produce a new way of tunnelling. His realisation led him to invent a device that has been used in one form or another in most major tunnels built since – the tunnelling shield. It consisted of a heavy iron frame that could be pushed forward a few inches at a time. The front of the frame was made up of a series of iron frames that could be folded back to allow miners to dig the ground ahead. Behind these frames was a wall consisting of a series of iron plates pressed against the tunnel face and supported on a set of horizontal wooden planks, that would prevent the face from collapsing. It was a complex and rather cumbersome machine and not easy to use, but it seemed that it would protect the miners from the worst of the river's water. Brunel's team carefully examined earth samples taken from beneath the riverbed, and subsequently decided to dig the tunnel close to the muddy river bottom, where he could expect to find clay. This would be a more solid and safe substance to dig through than the sand that was found deeper down.
Brunel began work on his tunnel in 1825, but the problems of such an operation soon became apparent. Although the shield itself worked well, water began to drip into the tunnel. This was more of an annoyance than a danger while the pump was working, but this machine proved unreliable and sometimes failed altogether. When the pump broke down, work had to stop as the tunnel quickly flooded. There were occasions when the miners had to abandon their tools and flee for their lives. Even when Brunel's men were able to work, they had to run the constant risk of the pumps failing. They also complained of frequent headaches and dizziness, caused by the poor air quality. The air underground was dirty and stale, contaminated due to the lack of an adequate ventilation system. There were lighting problems too. Illuminating the tunnels by candlelight was a constant challenge. Lamps give off only a very weak glow, and there were a number of accidents because the miners could not see what they were doing. Lastly, a number of Brunel's miners walked off the job because they could not tolerate the excessive temperatures that developed in the cramped conditions underground.
Despite all these setbacks, the tunnel finally emerged on the opposite river bank on August 12, 1841. Brunel's triumph, however, was only partial. The small payment per person made by the thousands of visitors who flocked to see the marvel hardly paid even a penny per foot of the tunnel's construction costs. Brunel had gone bankrupt long before the project was completed, and the government loan he had required to complete the project had to be paid back with interest. As a result, there was not enough funding to make it accessible to horse-drawn vehicles, as intended. Instead, the passageways were filled with souvenir sellers and entertainers. In the end, the tunnel was closed two years later, used at night, before it was finally closed entirely and fell into dereliction for decades.
It was only when the underground railway came to London in the 1880s that the Thames Tunnel found and achieved a measure of real usefulness. It was bought in 1869 by the East London Railway, who found it to be in such excellent condition that it was immediately pressed into service as a route for passenger trains heading east. The tunnel became, and remains, part of the London Underground network.
What kind of structure will make living in space comfortable for us?
A In the future, says Brent Sherwood, there will be a different kind of holiday. Imagine a hotel with a view that's constantly changing, where there are 18 sunrises a day, where food floats into your mouth. Sherwood trained as an architect and aerospace engineer. He is convinced it's only a matter of time before space becomes a desirable destination, and we're living on the Moon, and then, Mars. There's only one drawback. 'Nobody knows how to cook in space,' he says. 'No one would pay $1 million a night for a space hotel and put up with microwave meals.' Until now, says Sherwood, space habitats have been about the basics. But as more people stay in space for increasingly long periods, their physical environment is becoming more important.
B Experts like to contrast the first space station, Skylab, with the current International Space Station (ISS). Skylab was a generous habitat in comparison to the ISS because it was recycled out of a tank formerly used for storing fuel on an obsolete rocket. Designer Raymond Loewy put in a tiny window, which became a popular feature with the astronauts. When engineers designed the ISS, one of the things they had to consider was greater comfort, and this resulted in a number of design innovations, particularly when it came to the highly unusual beds the astronauts use – always a big problem in a zero-gravity environment. One ongoing issue is the transportation of essential cargo into space. It is extremely expensive to send essential deliveries to their destination by spacecraft – for example, it would cost $500,000 to send a single brick by spacecraft to the Moon.
C Consequently, the challenge has been to develop lightweight materials and kits. For this reason, attention is shifting towards inflatable structures, allowing entire habitats to be folded and packed on board. Aerospace company Bigelow won a contract with the National Aeronautics and Space Administration (NASA) to install the first inflatable on the ISS. It looks like a flimsy tinfoil balloon, but the Bigelow Expandable Activity Module is constructed using one of the most advanced fabrics ever developed by scientists. It has a layer of 'liquid crystal polyarylate superfibre', which makes it immensely tough and can survive the impact of small meteoroids.
Inflatables have improved greatly since the 1960s, when NASA commissioned tire company Goodyear to design an enormous galactic inner tube – a giant version of what you would find inside a normal bicycle tire – for astronauts to live in. This assignment was never completed, and the 9m-wide rubber doughnut never went into space. However, the idea stimulated the imagination of architect Guillermo Trotti, who copied aspects of it in 1974 when he designed an inflatable habitat for the Moon that could house 200 people.
D Trotti went on to co-found the Sasakawa International Center for Space Architecture, which offers a space architecture master's program. Trotti explains that every year, one aim of the program is to inspire young students to work on projects that will "push established NASA scientists to dream further, with creative and inspirational visions for future spaceships and buildings on the Moon, Mars, and beyond. 'If you look at the history of the industry, what we do in space is a mirror for our contemporary values on Earth,' says architect Neil Leach. Just like our earthly priorities, environmental sustainability is now top of the space agenda. The Apollo program was part of the rivalry between the old USSR and the USA; the ISS was a defining moment of international collaboration, and now we're seeing private entrepreneurs leading the way."
E Scientists at NASA have begun to consider the possibility of using things such as moon dust and meteoroids for building. "The Moon's surface is an open mine of potential resources," says space architect Madhu Thangavelu. "It is full of accessible minerals and compounds that could be used to produce metals, bricks, and glass." Thangavelu has worked to develop a method of Moon-based 3D printing, using moon dust, concrete, and sulfur. The technique they use would create structures that have high, rounded ceilings and walls of many layers, resembling the Gothic designs that emerged in European architecture from around the 12th century. Another leading architectural company has been developing a technique for 3D printing for the European Space Agency, based on building up a moon dust shell over a network of round domes.
F Getting to Mars is likely to cost $100 billion, spread over several decades. "Mars is the new world," says Robert Zubrin, engineer and president of the Mars Society. He imagines a world of greenhouses initially transported from Earth, "opening up the planet to both human habitation and agriculture." It is a plan the Mars Society illustrates with images of people in spacesuits watering crops and holding hands among radiant red rocks. Although this may seem somewhat far-fetched and optimistic, at least for the foreseeable future, it is certain that deep-space exploration will be the biggest challenge for international architects, Trotti says. "The key question is how to build an environment in which you can live for three years in a confined space, with the same people, in peace. Virtual reality could be an answer, allowing people to escape mentally, reduce anxiety, visit their hometown, or study remotely."
The effectiveness of an online course
As access to the internet has continued to grow, web-based learning has continued to expand. With approximately half of the households in the United States (or 150 million people) connected to the Internet, an estimated 2 million students are taking post-secondary courses that are fully delivered online. Millions of other students at all educational levels (primary, secondary, post-secondary) participate in online courses. However, the effectiveness of online courses, particularly in relation to individual student needs, perceptions, and student outcomes, is sometimes questioned.
Common elements for learning in a typical classroom environment are the social and communicative interactions between student and teacher, and student and student. The ability to ask a question, to share an opinion with a fellow student, or to disagree with the point of view in a reading assignment are all fundamental learning activities. However, effective web-based learning requires adjustments on the part of students and teachers for successful interactions to occur, for example. Many online courses provide students and faculty, and students and students with the ability to interact with each other via an electronic bulletin or discussion board.
While most studies show a link between interaction and satisfaction in web-based courses, some observers have cautioned that this is not always the case. Ruberg, Taylor and Moore, for example, observe that in order to interact successfully, students must adjust to the nonlinear nature of web-based learning. In linear, focusing on a single discussion thread. Web-based learning sessions on an electronic bulletin board can have multiple threads with several discussions and interactions progressing simultaneously. Students respond to a teacher but also to other students, depending on the interest and points of view.
Sproull and Kiesler caution about discussions based on misinformation, that continue because an instructor cannot necessarily immediately correct or clarify a comment. As a result, students need to have the experience and knowledge base to sift through the discussion for misinformation. In online learning, the amount of student interaction and the number of comments can easily lead to what is described as information overload. Furthermore, comments in online discussions tend to be lengthier than in face-to-face situations. With more information from many sources, students need to be more attentive to both the who and what of a discussion. Herbert Simon, an economist, cautions that, 'a wealth of information creates a poverty of attention.'
In examinations of interaction, the concept of 'presence', or a sense of being in a place and belonging to a group, has received attention. It is generally assumed that when a student is physically present in a face-to-face course, he or she has a sense of belonging to the class or group enrolled in the course and this sense of belonging is greater than that experienced on an online course. He or she listens to and may choose to raise a hand to comment, answer or ask a question. Furthermore, this same student may develop a relationship with other students in the class and discuss topics related to the class during a break. However, this is an assumption and not always true. For reasons, some students can also feel alienated in a face-to-face class and not feel part of a group.
The idea of presence has been redefined in relation to an online course. The simplest definition of presence for an online course refers to a student's sense of being registered and belonging in a course, and the ability to interact with other students and an instructor even though physical contact is not available. However, as this concept is studied, the definition is expanding and being refined to include telepresence, cognitive presence, social presence, teaching presence, and other forms of presence. The term 'community' is related to presence, and refers to a group of individuals who belong to a social unit, such as students in a class. In an online course, however, terms such as communities of inquiry, communities of learners, and knowledge-building communities have evolved.
As the definition of presence has expanded and evolved, a distinction has been made between interaction and presence, emphasizing that they are not the same. Interaction may indicate presence but it is also possible for a student to interact by posting a message on an electronic bulletin board, while not necessarily feeling that he or she is part of a group or a class.
A study conducted by Professor Anthony Picciano used questionnaires to determine students' attitudes in relation to their interactions and sense of purpose in online courses. An attempt was made to go beyond student perceptions to include performance and to perceptions of social presence, as well as actual participation in class activities. In addition, data was collected on performance measures that related specifically to course objectives. While much of the research, including this study, supports the strong relationship between students' perception of interaction and perceived learning, the results of the study indicated that the relationship of actual measures of interaction and performance is mixed.
The success of many online courses is dependent upon the nature of student-to-student and student-to-faculty interaction. However, how interaction affects learning outcomes and what the relationships between the two are, is in need of further study.