READING PASSAGE 2

You should spend about 20 minutes on Questions 14 - 26, which are based on Reading Passage 2 below. 

Black Holes

Black holes have been common topics in media and entertainment for some time. The actual name ‘Black Hole’ is misleading, as a hole implies an emptiness and a black hole is anything but empty space. A black hole is rather a great amount of matter packed into a very small area. For example, the amount of compressed matter in a black hole would be seen in a star ten times more massive than the Sun squeezed into a sphere approximately the diameter of New York City.

There are different types of black holes. A static black hole is one that is relatively simple to describe, as it does not rotate and it does not have a charge. A static black hole has three things of particular interest. The outer part is known as the photon sphere, so named as photons orbit the black hole here. Like all planets and stars, black holes have gravity, except much more than anything else. The photon sphere is the only place where light rays can have orbits around the black hole, though they are very unstable. The next point of interest is the event horizon. Like the photon sphere, this is just a mathematical distance based on gravity. Once something passes beyond the event horizon, it can never leave the black hole, as the gravitational pull is too strong. As even the light reflecting off an object will be drawn into a black hole, it is not possible to see something once it passes the event horizon. The centre of a black hole is the singularity and this where all the matter of a black hole from its origin lies, along with anything drawn in. The singularity is a difficult thing to describe. It is not a place, but more where the curvature of space time is infinite. It is not known what goes on there, but it is known that it depends on quantum mechanics.

Although the term was not coined until 1967 by Princeton physicist John Wheeler, the idea of an object in space so massive and dense that light cannot escape it has been around for centuries. Most famously, black holes were predicted by Einstein’s theory of general relativity, which showed that, when a massive star dies, it leaves behind a small and dense remnant core. If the core’s mass is more than about three times the mass of the Sun, Einstein’s equations showed that the force of gravity overwhelms all other forces and produces a black hole.

Scientists cannot directly observe black holes with telescopes that detect X-rays, light, or other forms of electromagnetic radiation. They can, however, infer the presence of black holes and study them by detecting their effect on other matter nearby. If a black hole passes through a cloud of interstellar matter, for example, it will draw matter inward in a process known as ‘accretion.’ A similar process can occur if a normal star passes close to a black hole. In this case, the black hole can tear the star apart, as it pulls it toward itself. As the attracted matter accelerates and heats up, it emits X-rays that radiate into space. Recent discoveries offer some evidence that black holes have a dramatic influence on things around them, emitting powerful gamma ray bursts, absorbing nearby stars, and both stimulating and hindering the growth of new stars.

There is a good, relatively recent example of detecting a black hole from events near it. An international team of astronomers has identified a candidate for the smallest-known black hole using data from NASA’s Rossi X-ray Timing Explorer (RXTE). The evidence comes from a specific type of X-ray pattern, nicknamed a ‘heartbeat,’ because of its resemblance to an electrocardiogram. The pattern until now has been recorded in only one other black hole system. The system in question combines a normal star with a black hole that may weigh less than three times the Sun’s mass. That is, of course, near the theoretical mass boundary where black holes become possible. Gas from the normal star streams toward the black hole and forms a disk around it. Friction within the disk heats the gas to millions of degrees, which is hot enough to emit X-rays. Variations in the intensity of the X-rays observed reflect processes taking place within the gas disk. Therefore it is by observing the gas disk that scientists can predict the presence of the black hole, rather than seeing it itself, which is, of course, impossible.

Although the basic formation process is understood, one perennial mystery in the science of black holes is that they appear to exist on two radically different size scales. At the one end, there are the countless black holes that are the remnants of massive stars. Peppered throughout the Universe, these ‘stellar mass’ black holes are generally 10 to 24 times as massive as the Sun. Astronomers spot them when other stars draw near enough for some of the matter surrounding them to be snared by the black hole’s gravity, churning out X-rays in the process. Most stellar black holes, however, lead isolated lives and are impossible to detect. Judging from the number of stars large enough to produce such black holes, however, scientists estimate that there are as many as ten million to a billion such black holes in the Milky Way alone. At the other end of the size spectrum are the giants known as ‘supermassive’ black holes, which are millions, if not billions, of times as massive as the Sun. Astronomers believe that supermassive black holes lie at the middle of virtually all large galaxies. Astronomers can detect them by watching for their effects on nearby stars and gas.

READING PASSAGE 3

You should spend about 20 minutes on Questions 27 - 40, which are based on Reading Passage 3 below. 

CCTV Surveillance

In recent years, a combination of perceptions and fears regarding increased street crime and advances in technology has seen an upsurge in the use of closed circuit television (CCTV) as a tool for tackling crime in public places. Many private companies and a number of local government authorities have initiated trials in the use of CCTV, and the technology is also being used in a number of ways in the public transport system.

Because CCTV is relatively new, it is still not clear how effective it is in deterring or reducing crime. Research evidence so far suggests that it is an effective strategy in situational crime prevention at a local level, but only as one of a range of crime prevention strategies. In addition, it appears from the research that CCTV is effective in addressing property crime and some types of assault and robbery. Of course, high-risk areas, for example jewellery shops, can greatly benefit from the visible deterrent of CCTV cameras.

Evidence also suggests that the benefits of CCTV surveillance fade after a period of time, and that displacement may occur, that is that the crime may simply move to other areas away from the CCTV surveillance, or there may be a shift to different sorts of crime that are less susceptible to CCTV surveillance. One important thing is that the reduction in crime that people believe CCTV brings can lead to enhanced perceptions of safety in a particular area, which makes communities happier and more satisfied with government actions.

In general, the issue of whether or not to consider implementing a CCTV scheme is likely to arise in response to a perception or awareness that there is a crime problem in a specific public place. This may be indicated by media coverage, by complaints to the council or other authorities or through police contact with the council. Once a council identifies that there is a problem, it needs to form a Community Safety Committee, which should study a broad range of crime prevention and community safety issues and evaluate various options for dealing with them.

Installing and trialling a CCTV scheme usually involves decisions about technical, financial and operational matters that may be beyond the expertise of a Community Safety Committee. Therefore, the establishment of a specialised CCTV Committee may be the appropriate way of ensuring sound management of the scheme. Alternatively, a program co-ordinator with experience in developing community safety initiatives could be appointed to manage the development of the CCTV program. Both of these should offer expert advice to the Community Safety Committee.

The Community Safety Committee must carry out a crime assessment of the area where problems have been identified. The analysis should be conducted in consultation with police, and, as appropriate, representatives of the local community. Once the crime assessment provides a clear picture of the nature of the criminal activities, a Crime Prevention Plan should be made. If the Committee believes that one of the strategies to address the problems identified in the crime assessment is the establishment of a CCTV program, it is essential that the Crime Prevention Plan outlines how this strategy is integrated with the broad plan objectives and why CCTV is considered appropriate.

There are various disadvantages and criticisms of CCTV. First is the perception that CCTV is an invasion of everyone’s privacy. It is argued that the steady expansion in the surveillance apparatus of the state and private sector has diminished the privacy of every individual, has lessened people’s trust in the state and poses a significant threat to personal privacy and individual freedom. Although in most countries there is nothing inherently unconstitutional in the use of surveillance by the state, there is netheless a danger that it may disturb some of the presumptions and relationships that underpin the relationship between the individual and the state. This is because mass surveillance promotes the view that everybody is untrustworthy. If governments gather data on people all the time, on the basis that they may do something wrong, this promotes a view that the citizens cannot be trusted.

There are also worries about the social effects of surveillance and the potential for discrimination. Cameras are installed so as to watch places and identified groups of people. Studies have shown that existing surveillance systems and databases with collected information may reflect biases that can exist in the social system, often based on factors such as race.

Another problem with CCTV is the cost of installation and maintenance. As an example, over the last 20 years in the UK, approximately 78 per cent of the Home Office crime prevention budget was spent on installing CCTV. Where previously this money might have been spent on street lighting and supporting neighbourhood crime prevention initiatives, it is now used to maintain and expand the network of police and local authority cameras.

Protecting the public is a duty of government. However, surveillance and the use of collected personal information may lead to a conflict between the interests of the citizen and the goals of the state, and it has the potential to undermine privacy and limit the freedom of the individual. It seems that CCTV does not significantly stop crime, although when a crime has occurred, CCTV is a vital element of the investigative process. Therefore, as CCTV on its own can do little to address long-term crime prevention, CCTV should only be considered as one part of an integrated crime prevention strategy and should be installed on a trial basis subject to rigorous evaluation as to its usefulness.