1.1 The Sun at visible wavelengths The Sun is seen as a blindingly bright, yellow object in the sky. The part of the Sun that you normally see is called the photosphere (meaning ‘sphere of light’); this is best thought of as the ‘surface’ of the Sun, although it is very different from the surface of a planet such as Earth. Its diameter is about 1.4 million kilometres, making the Sun's volume roughly one million times that of the Earth. The photosphere is not solid. Rather, it is a thin layer of hot gaseous mater
1 Observing the Sun
Never look directly at the Sun, either with the unaided eye or through spectacles, binoculars or a telescope. You risk permanently damaging your eyes if you do so.
Safety warning
Learning outcomes At the end of this unit you should: know about the electromagnetic spectrum and how it is used to infer properties of sources of radiation; know about the range of sizes, distances and motions of objects in the Universe and how they can be measured; know about the structure of, and the main processes operating in, the Sun; comprehend concepts lying well outside everyday experience, including those that involve very large and very smal
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5.3.4 Aye-ayes Perhaps with good reason, the aye-aye has been dubbed by some ‘the strangest of all primates’ and LoM provides some of the reasons [p. 243]. Little wonder that, as DA points out, the species was first classified as a rodent like them, it has powerful incisor teeth that grow continuously. 5.5.2 Indris and sifakas Both indris and sifakas are unusual amongst lemurs in that they are active largely by day. Leaves are their primary food. They have a specialised form of locomotion, best described as ‘vertical clinging and leaping’ and the leaps they can take, using their powerful legs, can be up to 10 m. DA describes the bounding movement of sifakas when they are compelled to come to ground. (If you go back to the previous video sequence that shows this strikingly white species – the so-called silky s 5.2 Madagascan diversity Watch the video sequence below, which focuses on just three lemur species – the ring-tailed (in a very brief sequence, leaping from one tree to another), the golden bamboo lemur, already mentioned, and the sifaka, plus the 4 Galagos, lorises and pottos Activity 6 is divided into several parts, on successive pages, and asks you to answer a number of questions. Look ahead to this activity now and highlight, or list, the different ‘process’ words, which tell you what you need to do with the content You should have found ‘describe’, ‘contrast’, ‘eva 8 What makes a successful omnivore? From what has been said already, there's good evidence that the key physical characteristic of the great majority of omnivores is a non-specialist dentition. What about other aspects of their biology? Question: Many omni 3 Is specialisation always advantageous? Specialisation generally implies the possession of adaptations that make animals particularly effective or efficient in one or more aspects of their lives. In many of the examples used in other units in this series, mammals are likely to possess adaptations related to the acquisition and/or processing of food. 10 Living in herds Wildebeest are only one of the species of plant predator that live in herds. Many others do too. Watch the the TV programme from 30.48–47.32 and read LoM p. 109. Identify and write down (a) a couple of advantages and 6.2.4 The speed and direction of the Earth's motion The first significant claim to have detected the motion of the Earth relative to the ‘frame of isotropic 3 K radiation’ came in 1977 from a group at Berkeley, California. They concluded that the Earth is moving at a speed of (390 ± 60) km s−1, in a direction towards the constellation Leo, relative to a frame in which the 3 K radiation is isotropic. Their conclusion resulted from observations of a variation of intensity with angle of the form predicted by Equation 14, which w 5.3 The redshift of the 3 K radiation The temperature, T, of the radiation is proportional to the most probable photon energy, E, which as we have said is proportional to f, and hence inversely proportional to the wavelength λ. Thus, According to Equation 1, we have for the redshift, z 3.3 Extending the distance scale Having reviewed some of the properties of galaxies, we are now in a position to return to the question of how we are to develop further our methods of measuring distance. The various steps taken in determining larger distances from known smaller ones are often called ‘rungs in the distance ladder’. The process of constructing a rung has been: Find a measurable quantity associated with a class of objects. Observe how the measura 3.2 Some general properties of galaxies Firstly, we note that galaxies tend to occur in clusters rather than singly. The mutual gravitational attraction of galaxies naturally tends to hold them on paths that remain close to each other. Typically a cluster contains tens or hundreds of galaxies. There are, however, large clusters with thousands of galaxies, and there are some solitary galaxies. Our own Galaxy is a member of a smallish cluster of about 36 galaxies called the Local Group (see Author(s): 3.1 First steps towards a distance scale As you will see from Table 2, when it comes to astronomy and cosmology, one is called on to deal with a wide range of distances. (Note that a light-year (ly) is the distance light travels in one year, i.e. 9.46 × 1015 m. The distances are also quoted in a very commonly used astronomical unit of distance: the megapar 5.1.4 Getting agreement with the no-monopole law Substituting Equation 7.23 into the no-monopole law gives immediate agreement because The no-monopole law is analogous to Gauss's law in empty space, and it leads to a similar conclusion: the magnetic wave must be transverse. This has already been established using Farada 5.1.2 Getting agreement with Gauss's law Substituting the assumed form of the electric field (Equation 7.20) into the empty-space version of Gauss's law (Equation 7.16) gives The first two partial derivatives are equal to zero because f does not depend on x or y. So we obtain 4.5 Endocrine disruptors Then he was a she… (Lou Reed, American rock singer) In 1996, a book called Our Stolen Future was published, bringing to public attention a debate that had been simmering among biologists for some time. Written by Theo Colborn and two colleagues at the World Wildlife Fund (WWF), this book presented the hypothesis that certain industrial chemicals, commonly found as environmental pol 1.4 Decimal places If you have less than one unit you should put a zero before the decimal point to make it easier for yourself and others to read the value (e.g. you should write 0.4 rather than just .4, as will be explained later in this unit). However, how many zeros should you put after the last whole number in the series? For instance, is 0.4 the same as 0.40? The short answer is that on one level, it is. However, by writing 0.40 we are saying that there are four tenths and zero hundredths, an
Activity 7
Question 11
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Activity 7
