TLDR;
This video explores the electromagnetic spectrum, starting with visible light and venturing into invisible realms like ultraviolet, X-rays, gamma rays, infrared, microwaves, and radio waves. It explains how color is perceived, the science behind pigments, and how different creatures perceive light. The journey spans from art and nature to technology and the cosmos, revealing how each part of the spectrum is used in various applications, from medicine to astronomy.
- Visible light is only a tiny part of the whole electromagnetic spectrum.
- Color perception varies across species, with some seeing ultraviolet and others having more color sensors than humans.
- Invisible parts of the spectrum, like infrared and microwaves, have significant applications in technology and science.
Introduction to Color and Light [0:05]
The video begins by defining color as a function of light's wavelength, with longer wavelengths appearing redder and shorter wavelengths appearing bluer. It explains that the visible spectrum is a small part of a much larger electromagnetic spectrum, which includes invisible colors beyond red and blue. The video promises a journey through this spectrum, exploring science, art, nature, and technology.
The Science of Visible Light [1:59]
The understanding of vision evolved from the belief that eyes emitted light to Leonardo da Vinci's realization that light enters the eyes. Isaac Newton further unraveled the mystery of color by demonstrating that white light is composed of all colors, using prisms to split and recombine light. Newton initially identified five colors but later expanded it to seven to match the musical scale. The human eye perceives a wide range of colors using only three color sensors: red, green, and blue, similar to how cameras work.
Yellow: Pigments and Perception [5:46]
The video transitions to exploring the color yellow, abundant in nature through flowers and butterflies. These yellows are created by pigments, complex molecules that absorb certain colors of light and reflect others. The specific structure of pigment molecules determines the color of reflected light. An experiment with a marbled white butterfly demonstrates how changing pigment chemistry with ammonia can alter its color from white to yellow. The video also touches on the historical difficulty of creating bright yellow paints, highlighting Van Gogh's use of Chrome yellow and its instability.
Green: Chlorophyll and Structural Color [9:54]
Green, the color of nature, is primarily due to chlorophyll in plants, which absorbs light for photosynthesis and reflects green light as a byproduct. While green pigments are common in plants, they are rare in animals. The video uses the example of the turaco bird, which has a unique green pigment in its feathers. Some animals, like the swallowtail butterfly, create color through structural means, using microscopic ridges on their wing scales to reflect and intensify green light without any pigment.
Blue: Scattering and Pigments [12:39]
The blue color of the sky is explained through the phenomenon of light scattering, where shorter wavelengths like blue scatter more in the atmosphere. Similarly, some animals, like the damsel fly, use particles in their cells to scatter blue light. The video contrasts this with blue pigments, such as ultramarine, which was historically expensive and highly valued, often used in religious paintings to depict the Madonna.
Indigo: Dyes and Cosmetics [16:00]
Indigo is discussed as a color used historically as a cosmetic and dye. In ancient Europe, the Celts used Woad to paint their bodies, which also had antiseptic properties. A more intense dye comes from the indigo plant, which changes from dull yellow to blue upon exposure to oxygen. Indigo was commonly used to dye clothes, including jeans, until recently.
Ultraviolet: Beyond Violet [18:26]
The video explores ultraviolet (UV) light, discovered by Johann Ritter, who noticed its effect on silver chloride beyond the visible spectrum. While humans can't see UV light, insects and birds can. Flowers have UV patterns that guide insects to nectar, and kestrels use UV vision to locate rodent urine, indicating areas with more prey.
X-rays: Revealing the Invisible [23:16]
X-rays, discovered by Wilhelm Röntgen, are a form of light with very short wavelengths and high energy, allowing them to pass through solids. This property has revolutionized medicine, enabling the imaging of bones and internal structures. The video also showcases how photographer Nick Veasey uses X-rays to create art, revealing the hidden structures of everyday objects.
Gamma Rays: The Universe's Most Energetic Events [27:08]
Gamma rays are presented as the highest-energy form of light, revealing a different view of the night sky. Gamma-ray bursts, detected by satellites like NASA's Swift, are caused by the death of massive stars or the collision of neutron stars. These bursts release immense amounts of energy, marking one end of the spectrum.
Orange and Red: Signals and Status [29:41]
Moving back towards longer wavelengths, the video discusses orange and red. Orange is used as a warning signal in nature, such as in monarch butterflies, which are foul-tasting. Red is a strong signal, often indicating status or suitability as a mate in birds. Historically, red dyes were expensive, making red clothing a symbol of wealth and power.
Color Vision and the Coral Reef [33:04]
The video compares human color vision to that of other creatures, noting that many have more sensitive color vision. The coral reef is highlighted as a place where color is crucial for communication, with the mantis shrimp having 16 different color senses. In the deep ocean, where red light doesn't penetrate, many creatures appear red under artificial light but are black in their natural environment.
Infrared: Beyond Red [36:43]
Infrared light, discovered by William Herschel, is invisible to human eyes but can be sensed as heat. Ordinary cameras can be modified to see infrared, revealing that plants reflect infrared light strongly. Infrared cameras are used to monitor vegetation from space and to see heat signatures, such as those of animals in the dark.
Microwaves: From Kitchens to the Cosmos [42:34]
Microwaves, with wavelengths much longer than visible light, are used in microwave ovens and radar technology. The cosmic microwave background, a faint glow of microwaves in space, provides evidence for the Big Bang theory and the early structure of the universe. Radar, which uses microwaves, was developed during World War II and is used to detect objects.
Radio Waves: Exploring the Distant Universe [45:47]
Radio waves cover a vast range of the electromagnetic spectrum and are used in radio telescopes to detect natural radio waves from deep space. The Atacama Large Millimeter/submillimeter Array (ALMA) is presented as an advanced radio telescope that allows scientists to peer deeper into the universe. Quasars, distant galaxies with supermassive black holes, were first discovered through their radio emissions and emit radiation across the entire spectrum. The video concludes its journey at the edge of the universe, with the most distant objects we can see.