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International light day scrolling presentation
- 1. “You don’t seelight until it shines on something” - Oliver Postgate, The Clangers, 1971
- 2. Artists like JohnGrimshaw (1836-1893) used the strange effects of light, clouds and atmosphere in his paintings.
- 3. The light wesee from the sun took 8 minutes 20 seconds to reach the Earth. So we see the Sun as it was 8 minutes 20 seconds ago. What were you doing 8 minutes 20 seconds ago? From: Wlpapers.com
- 4. The sun’s lightyou see now was made in the core of the Sun millions of years ago! It starts off as X-rays, which bump into the Sun’s atoms losing energy until they reach the surface. Image from “Science Picture/Corbis”
- 5. Darkness is oftenassociated with sadness or depression in books and plays: “Away from light steals home my heavy son, And private in his chamber pens himself, Shuts up his windows, locks fair daylight out, And makes himself an artificial night.” - Montague, Romeo’s father, in Act 1 Scene 1 of “Romeo and Juliet”, talking about Romeo, who is depressed.
- 6. Gamma rays, X-rays,ultraviolet waves, visible light, infrared, microwaves and radio waves are all the same thing, but with different amounts of energy. They are all waves made of tiny packets of energy called “photons”. Image from “Ask a Scientist”.
- 7. This is whatthe Crab Nebula looks like at different wavelengths. The Crab Nebula is the remains of a star that exploded nearly 1000 years ago. It was so bright, people in America and China saw it by daytime.
- 8. Radio waves Microwaves Infra-red waves Visible light Ultraviolet light X-rays Gamma rays Radio waves arethe weakest form of light, given off by the coldest objects in the Universe. The longest wavelengths need to be seen by lots of telescopes. Image from Wikipedia
- 9. Radio waves Microwaves Infra-red waves Visible light Ultraviolet light X-rays Gamma rays Hydrogen gas inspace gives off radio waves with a 23cm wavelength. This is how we find it on its own without stars. Mobile phones use similar wavelengths, but don’t use exactly 23cm so as to help astronomers. Image from Wikipedia
- 10. Radio waves Microwaves Infra-red waves Visible light Ultraviolet light X-rays Gamma rays DING!!!! Microwaves are thenext-lowest energy in the Universe. The remains of the Big Bang explosion have cooled down so much they’re now microwaves. We can see it as static on our TV. Image from Currys.
- 11. Radio waves Microwaves Infra-red waves Visible light Ultraviolet light X-rays Gamma rays DING!!!! Microwaves heat foodby making water molecules move. They act like magnetic fields which keep moving, and the water molecules move to try and keep up. Heat is moving atoms, so this movement heats your food.
- 12. Radio waves Microwaves Infra-red waves Visible light Ultraviolet light X-rays Gamma rays Everything alive glowsin infra-red waves. The nice feeling of sunlight or an electric fire on your skin is infra-red waves. They’re less energetic than light, but they make atoms and molecules move, which is what makes us feel heat. Image: e-waves.weebly.com
- 13. Radio waves Microwaves Infra-red waves Visible light Ultraviolet light X-rays Gamma rays Infra-red waves cango through dust in space, which helps us see stars hidden in dust clouds. This is how we can find out about star birth, which takes place inside dust clouds. Images: European Southern Observatory
- 14. Radio waves Microwaves Infra-red waves Visible light Ultraviolet light X-rays Gamma rays Visible light isonly a tiny part of the electromagnetic spectrum, but it can show a huge amount of fine detail, which is probably why our eyes use it, not other wavelengths. Images: Caleum Observatory and University of Chicago
- 15. Radio waves Microwaves Infra-red waves Visible light Ultraviolet light X-rays Gamma rays Visible light ismore energetic than infra-red. This is why things have to get really hot to start glowing. Red light is least energetic; violet light is most energetic. Image: Wikipedia.
- 16. Radio waves Microwaves Infra-red waves Visible light Ultraviolet light X-rays Gamma rays If a rainbowcould keep going, you’d see ultraviolet light (“UV”) after violet. It’s a bit more energetic than visible light, so we see more energetic things in the Universe with it. This is the Andromeda galaxy in visible and ultraviolet light.
- 17. Radio waves Microwaves Infra-red waves Visible light Ultraviolet light X-rays Gamma rays Ultraviolet light isstrong enough to knock electrons off atoms. It does this to the atoms that make your skin - which is why sunbathing can give you skin cancer. Suncream works by reflecting the light away from your skin. We’ll teach you how to make it. Image from the Guardian.
- 18. Radio waves Microwaves Infra-red waves Visible light Ultraviolet light X-rays Gamma rays X-rays are givenoff by really REALLY hot stars, black holes, radioactive atoms, and other very energetic objects in the Universe. The Sun makes X-rays deep inside, but they “cool down” to ultraviolet, visible and infra-red light on their way to the surface. Image from the Chandra X-Ray Telescope.
- 19. Radio waves Microwaves Infra-red waves Visible light Ultraviolet light X-rays Gamma rays X-rays were discoveredjust before 1900 by a scientist called Wilhelm Roentgen who was studying radioactivity. He took a the first ever X-ray of his wife Anna’s hand. She was scared when she saw her bones. X-rays are so strong they go through human flesh. Image from the Children’s Hospital of Philadelphia.
- 20. Radio waves Microwaves Infra-red waves Visible light Ultraviolet light X-rays Gamma rays Gamma rays arethe most energetic radiation of all. When they were first discovered coming from space, people thought it was war. Image: phys.org
- 21. Radio waves Microwaves Infra-red waves Visible light Ultraviolet light X-rays Gamma rays Gamma rays aregiven off when heavy atoms fall apart (radioactivity). They can go through lead. Gamma ray bursts in space are very short and we don’t know for sure what causes them yet. Maybe black holes! Image: Wikipedia
- 22. Photo: Alice Sheppard(from Lewisham station) Crepescular rays are stripes of shadows cast by clouds and air with particulates lit up by the sun.
- 23. Birds and beescan see in ultraviolet light. Flowers look like targets to them! Photos: Andrew Davidhaz, Rochester Institute of Technology
- 24. Snakes have infra-redsensing membranes near their eyes. So they can’t “see” in infra-red, but they can sense, and they have bad eyesight. Perhaps this is what a mouse looks like to them …. Pictures: Quora; Encyclopedia Britannica
- 25. Painting: “Open Windowon a Garden” by Konstantin Samov, 1934. Notice how the artist uses light and shadows to make objects clearer and brighter.
- 26. Blue objects reflectblue light, red objects reflect red light. In late evening or early morning, try turning the lights off. Things will appear blue. Blue objects (a pair of jeans?) will look pale. Red objects (a KitKat wrapper?) will look dark. Image: design.tutsplus.com
- 27. Plants absorb redand blue light, but reflect green light. Scientists studying plants at “night” shine green light on them to see. The plants reflect that light and continue to behave as it it’s night. Image: hackerfarm.jp
- 28. Lightning creates lightbecause the electric current heats the air it passes through: it reaches 27,000°C, 6x hotter than the surface of the Sun! Image: Stephen Cheatley
- 29. A light yearis a unit of distance, not time. It’s the distance light travels in 1 year. It’s 5,878,625,373,184 miles! The nearest star to the Sun is called Proxima Centauri. It’s so small we can’t easily see it. It’s 4.3 light years away.
- 30. The constellations look flat,but the stars in them are at different distances away from us. If you were on Betelgeuse, you’d see the Earth as it was in the time of Shakespeare. Betelgeuse looks orange, because it’s a red giant. It will explode as a supernova one day. Maybe in your lifetime?
- 31. A meteor (“shootingstar”) gives off light because it moves so fast, it compresses the air in front of it, which heats up. It’s not because of friction! Photo: NASA/JPL
- 32. “Corfu: Light and Shadows”, paintingby John Singer Sargent, 1909.
- 33. The aurora iscaused by energetic particles from the solar wind striking particles from the Earth’s atmosphere. The energy is released as green, red or purple light. Image: Tommy Richardson.
- 34. The aurora alsoappears on Jupiter and Saturn. Magnetic fields direct the energetic particles from the solar wind towards the poles. That’s why the aurora appears there.
- 35. The surrealist artistRene Magritte used light and dark to confuse. Is it night or day in this picture?
- 36. Deep sea creaturesuse light to communicate with each other and find food. Producing your own light is called bioluminescence. Bioluminescence has evolved about 40 times independently! Image: National Oceanic and Atmospheric Administration (NOAA)
- 37. Photo by JohnTyler Female glow worms use bioluminescence to find a mate. Light pollution makes it harder for male glow worms to find the female glow worms. You can often see glow worms in the country, waiting for mates on grass or branches.
- 38. “We can easilyforgive a child who is afraid of the dark; the real tragedy of life is when men are afraid of the light”. This means it’s OK to be scared when you are young, but it isn’t good to be scared to learn new things as you grow up. Light is associated with knowledge. This quote is often attributed to Plato, but there is no record of him saying or writing that. Nobody really knows who said it first. Plato statue from Wikipedia
- 39. If you shonea light beam with a torch you could never catch up with the light. Light is the fastest thing in the universe. Nothing can catch up with it. Image: Wikipedia volunteer “Lumenbuddha”
- 40. Dark can bea good thing. It helps us sleep, and nocturnal (night-time) animals rely on it. And we can’t see stars without the dark! “Earth Hour” and the “Campaign for Dark Skies” encourage people to switch off their light or use less invasive lighting so we and many animals can be healthier. Image: “Visit Coll” (Coll is an island west of Scotland).
- 41. Shadows on theMoon are really dark because there’s no air on the Moon. Air diffuses light, meaning it sends it in lots of different directions. That’s why shadows are so faint on a cloudy day. You can tell there is no air on the moon because the edges aren’t blurry, like the horizon on Earth.Picture: Apollo archives.
- 42. Retroreflectors reflect lightback to its source so will reflect at a lot of angles. You will see some at the demonstration tables. Cats’ eyes are natural retroreflectors. This helps cats see at night. Bicycles are also equipped with retroreflectors. They catch light from nearby car headlights, even if the car isn’t right behind the bicycle. All images: Wikipedia entry on retroreflectors.
- 43. Picture: NASA Apolloarchives. There are retroreflectors on the Moon. From Earth we shine lights on the moon. The light bounces off the retroreflectors. We time how long it takes to get back. This tells us how far away the Moon is. This is how we know the Moon moves away from the Earth at 4cm/year.
- 44. In a solareclipse the Moon goes in front of the Sun (from our point of view). This way we see the sun’s light shining on its atmosphere. It’s usually too bright to see this. Image: M. Druckmüller.
- 45. Ultraviolet light Suncream worksbecause it contains tiny, shiny particles (e.g. zinc oxide) which “scatter” the ultraviolet light, sending it in lots of directions away from the skin. Suncream may also contain nanoparticles (tiny particles, often of carbon) which absorb the ultraviolet light.
- 46. Humans have 3types of cones - to see red, green and blue. Mantis shrimp have 16 types of cones for different colours! They can see linear and circular polarisation, which is special shapes of light waves. Sunglasses use polarisation to filter out some sunlight. Image: Nina Meinzer
- 47. Although sharks arevery likely colour blind, they can sense (other) electromagnetic fields over long distances. This helps them find wounded prey animals. Image: Wikipedia Commons
- 48. This presentation wasmade for the International Day of Light event at UCL, 15th May 2018 By: Alice Sheppard, UCL Extreme Citizen Science and “Doing It Together Science” With: Nina Meinzer, Nature Communications
Editor's Notes
- #37 I haven’t explained the causes of bioluminescence here as they seem VERY complicated. Kids tend not to learn about enzymes until they’re in GCSEs. I can add another slide going into this ….