Download Red Shift - Animated Science

The Big Bang Although people often believe that a god created the world, current scientific experts have come up with a theory for creation called the big bang which has scientific proof! This theory involves a great explosion where everything in the known universe was formed. All the energy and matter found today in the universe expanded from tiny point and formed the galaxies, stars, planets, asteroids, gases, dust and energy. Even today the universe is still expanding. In fact one example of how we can prove this is by looking at a phenomenon called red shift. It was discovered by accident that light emitted from stars in other galaxies seemed to be shifted more towards the red end of the spectrum than expected. i.e. when we expected violet light we actually got blue! We know by analysis that certain gases when stimulated give off certain colours. These light spectra can be used to identify stars. This is an example of a spectrum – VIBGYOR (ROYGBIV backwards) Red Shift The reason for this is because it is moving away from us as the universe is expanding! This is a scientific proof.
Mr Powell Wavelength The reason this shift occurs is because the wavelength of the light gets a little longer because of this movement. The reverse effect happens when ambulances sirens sound higher pitch when it is coming towards you. The sound waves are compressed by the motion, and the wavelength decreases. Remember that red light has a longer wavelength than blue. More On Spectra When light passes through a prism, it separates into the colours that make it up. White light changes to a swath of colours. This rainbow is called a spectrum. You can make spectra (the plural of spectrum) in many ways: with a prism, with drops of water (as in a real rainbow), or with gratings (like in the glasses you can get). Scientists build special instruments to separate light, usually with gratings. These instruments are called spectrographs. When astronomers pass the light of a star through a spectrograph, they get a spectrum of the star. The spectrum looks like a regular rainbow of colours—except that there are dark lines in it. Here is a spectrum of our sun:
Mr Powell What's going on? It turns out that each element absorbs light of a particular frequency or a particular colour. If that element is in the cool atmosphere of the star, those atoms will absorb the light at that colour and produce the line. Each element has a specific "signature" or a specific set of lines. Here are spectra for some elements common in the atmospheres of stars: In a star, these elements absorb light at their special frequencies. On the following image, you will see a star's spectrum. Your job is to identify all the elements you can detect in the star's atmosphere. Which elements are present? Answer ­ Hydrogen & Magnesium
Mr Powell Example Here are three spectral diagrams from a star. The first one is a reference diagram. The second two are shifted across to the red end of the spectrum. Hence, they are moving away from us. We can tell how fast they are moving by the shift. The middle band is actually shifted by a distance of 100Å (angstrom) or 100 x 10 ­10 m. (10nm). This translates to a speed of 24,000 km/hour or 15,000 mph. The bottom band is shifted by 760Å or (76nm) which translates to a speed of 136,000km/hour or 84,000 mph. So this shows that the lower stars are moving away from us and the further they are away the faster they travel.
Red Shift Mr Powell