SEEKING SCIENTIFIC KNOWLEDGE Scientists seek knowledge about the world around us To do this they make careful observations which lead to new theories Scientists design experiments to test their theories Depending on the evidence of the experiments good theories are kept and bad ones are discarded 4 Scientists in ancient times Early scientists often worked in many different areas of knowledge One of the first scientists the ancient Greek Aristotle 384 322 bce wrote about physics biology astronomy and psychology Today scientists usually specialize in one field of study Building knowledge Scientists make new discoveries by building on the work of the scientists that came before them In this way our scientific knowledge grows When asked to describe his own discoveries in 1675 the famous English physicist Isaac Newton paid respect to other scientists by saying If I have seen further it is only by standing on the shoulders of giants
The scientific method The scientific method is a process that scientists follow in order to increase their understanding of a problem The scientific method usually consists of these steps 1 Ask a question 2 Carry out research by gathering information and making observations 3 Make a hypothesis which is a guess about what the answer might be 4 Design an experiment to test your hypothesis making a prediction of what will happen 5 Analyze your results and present your conclusion Using this method scientists are able to collect evidence that supports their theories They can also use the scientific method to show that a theory is wrong Scientists in the Islamic world were among the first to use the scientific method more than 1,000 years ago In the 800s Persian chemist Jabir ibn Hayyan was one of the first scientists to carry out experiments in a laboratory 5 Teamwork Scientists often work together in large teams At the European Organization for Nuclear Research CERN thousands of scientists carry out experiments using the Large Hadron Collider This machine smashes together tiny subatomic particles at close to the speed of light This recreates conditions from near the beginning of the universe to test theories about the structure of space Read on to discover the challenges that scientists have overcome through the ages The answers to each project's questions are found on page 31
THE THEORY OF LIGHT Light is a form of energy called electromagnetic radiation which travels in the form of a wave The scientific study of light is called optics One of the first people to describe how light behaves was Arab astronomer and mathematician Ibn al-Haytham Ibn al-Haytham about 965 1040 bce Ibn al-Haytham worked in Cairo Egypt where he performed experiments using lenses and mirrors to show that light travels in straight lines He also described the way that light is refracted or bent as it passes from air into water 6 Bending light Light moves at different speeds depending on the substance it must pass through For example light passes more slowly through water than it does through air These differing speeds cause a beam of light to appear to bend as it passes from air into water This is called refraction Refraction makes an object underwater appear to be closer to the surface than it really is Seabirds learn to allow for refraction when they dive for fish Otherwise they would always miss their prey Apparent position Actual position
Splitting light Ibn al-Haytham discovered that white light is made up of all the colors of the rainbow A glass prism can separate the colors out by refraction Each color is made by light waves with a particular wavelength Wavelengths are measured in nanometers nm There are one billion nanometers in one meter 3 2 feet For instance red light has a wavelength of about 700 nm while blue light has a wavelength of about 450 nm Each wavelength is refracted by the prism at a slightly different angle which splits the light into its separate colors Retina Pupil Image on the eye Our eye captures light through a small hole at the front called the pupil It forms an upside-down image on the lining of tissue at the back of the eye called the retina Light entering the pupil is refracted by the curve of the eyeball turning the image upside-down Our brains turn the image rightside up 7 Prism project CAMERA OBSCURA A device called a camera obscura creates images much like those made by our eyes This one is simple to make You will need an empty cereal box and its empty inner bag tape a pin scissors and a source of light such as a light bulb 1 Cut out a large rectangle from the front of the box and tape the inner bag over the hole to make a screen 2 Use the pin to make a small hole in the side of the box that is opposite the screen 3 Hold the pinhole-side of your camera obscura close to a light bulb and see an image of the bulb appear on the screen Which way up is the image
