Visible light (1672)
Created by NASA.
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- what is the phenomena of aurora then?(8 votes)
- Aurora occurs when the sun sends off matter we call particles to the empty space. These particles are charged and contain energy, which means they contribute to electricity. These particles flying in space are called "solar wind". Sometimes the solar wind hits Earth. Earth has a protection shield of energy around it. This is called the "magnetic field" and forms an elongated sphere around the Earth called the "magnetosphere". The magnetic field wards off most of the solar wind. At high-latitude areas (polar areas), the magnetic field is less powerful, and cannot protect Earth from the solar wind. There the particles of the solar wind and coming from the magnetosphere may hit the particles of the air (Earth's atmosphere). When they hit, the atmosphere is heated and excited and the excess energy gets away, a phenomenon which we see as moving lights in the sky above 100 km altitude typically. An aurora can also occur following a solar event called a coronal mass ejection (CME), when the charged particles rip through the electromagnetic field because of their power.
Auroral phenomena have been observed on other planets than Earth that have a magnetic field, such as Jupiter, Saturn and more recently Mars. It is believed to be a widespread phenomenon in the Solar System and beyond.
Source: http://simple.wikipedia.org/wiki/Aurora(11 votes)
- Mars has a less dense atmosphere. If there are less particles in an atmosphere, how does that change the perceived spectrum of light reaching the surface?(4 votes)
- The same (white) light from the Sun that reaches the Earth, reaches Mars. If you were to split a beam of light on Mars with a prism, it would split into a rainbow, just like Isaac Newton observed on Earth centuries ago. When light passes through Earth's atmosphere blue light is scattered more than longer wavelengths of visible light, therefore we see our beautiful blue sky. On Mars, or the Moon, with very diffuse atmospheres, the particles would barely scatter any of the light waves, therefore the sky would appear dark and space-like.(5 votes)
- Can you please elaborate the dependence of color of sun on temperature?(2 votes)
- It is called black body radiation. It is the idea that all normal matter emits certain wavelengths of light depending on their temperature. The cooler an object is, the redder the wavelength is as that end of the spectrum is lower energy. Conversely, the hotter an object is, the bluer it gets. Keep in mind, the objects will radiate light across a variety of the spectrum, and not just visible light. This just explains where it's emitting the most light from and could easily tend toward infrared for cooler objects.(7 votes)
- why are there only three stars colour ? why not violent for hottest indigo or green(2 votes)
- It is kind of complicated and has to do with how our eyes perceive color. Stars are black body objects, which basically means they emit a range of light with the peak amount at a particular wavelength depending on their temperature. This peak can fall anywhere on the visible spectrum, or beyond it in either the infrared or ultraviolet direction. For cooler stars, it is in the redder direction and for hotter, bluer. While this means the majority of their light is in that range, they still emit a lot of light in the surrounding ranges. When the peak falls somewhere in the middle, our eyes are getting so much light, that our brains blend it all and interpret it as white light rather than green. Also, our eyes are very poor at distinguishing violet light, so the other light incoming will overpower the violet and just make it appear bluish-white.(5 votes)
- why is mars red(1 vote)
- Because it has tons of dust with Iron in it, and Iron is red.(2 votes)
- Does the sun burn yellow/orange because of the energy of the molecules it is burning off? If so, does the continuous burning of molecules result in the change of color of the sun? Was the sun originally blue, and is currently progressing through the visible light spectrum as it burns off its total energy, eventually ending in solar death?(2 votes)
- Do the light beams emitted and reflected by the space devices for measuring the topology of the planet, use different wavelengths for mapping the features of the ground?(1 vote)
- Why is the temperature in infra-red region warmer than that in visible region?
The frequency of visible light is greater than that of infra-red rays. So, the energy of infra red rays will be lesser (E=hv :-Plank's relation) and hence the temperature too.(1 vote)
- the perceived temperature is hotter for IR light than visible light because in the atmosphere IR light is more concentrated than Visible light is. In fact this is why it feels hotter in sunlight than in ambient light(1 vote)
- How would you know that the blue sun wasn't just REALLY REALLY close and that the red one was is just really far away? (the doppler shift in color) why and how is it assumed that the color of the suns is to do with temperature. What am I missing? Thanks.(1 vote)
- So, as particles are bigger, it can scatter light of more wavelength right? Do, if the particles are so huge, can they scatter white light? Perhaps, is it causing mist/fog to be whitish?(1 vote)
All electromagnetic radiation is light. Visible light is the only part of the spectrum you can see. For all your life, your eyes have relied on this one narrow band of EM radiation to gather information about your world. Though our Sun's visible light appears white, it is really the combined light of the individual rainbow colors with wavelengths ranging from violet at 380 nanometers to red at 700 nanometers. Before Isaac Newton's famed experiment in 1665, people thought that a prism somehow colored the Sun's white light as it bent and spread a sunbeam. Newton disproved this idea by using two prisms. To show that white light is made up of the bands of colored light, Newton used a second prism to show that the bands of colored light combine to make white light again. Visible light contains important scientific clues that reveal hidden properties of objects throughout the Universe. Minute gaps in energy at specific visible wavelengths can identify the physical condition and composition of stellar and interstellar matter. Human eyes aren't nearly sensitive enough to detect these faint peaks, but scientific instruments can. Scientists can learn the composition of an atmosphere by considering how atmospheric particles scatter visible light. Earth's atmosphere, for example, generally looks blue because it contains particles of nitrogen and oxygen which are just the right size to scatter energy with the wavelength of blue light. When the Sun is low in the sky, however, light travels through more of the atmosphere and more blue light is scattered out of the beam of sunlight before it reaches your eyes. Only the longer red and yellow wavelengths are able to pass through, often creating breathtaking sunsets. When scientists look at the sky, they don't just see blue, they see clues about the chemical composition of our atmosphere. However, visible light reveals more than just composition. As objects grow hotter, they radiate energy with a shorter wavelength, changing color before our eyes. Watch a flame shift from yellow to blue as it is adjusted to burn hotter. In the same way, the color of stellar objects tell scientists much about their temperature. Our Sun produces more yellow light than any other color because of its surface temperature. If the Sun's surface were cooler, say 3,000 degrees celcius, it would look reddish, like the stars Antares and Betelgeuse. If the Sun were hotter, say 12,000 degrees celcius, it would look blue like the star Rigel. Like all parts of the electromagnetic spectrum, visible light data can also help scientists study changes on Earth such as assessing damage from a volcanic eruption. This NASA EO-1 image combines both visible and infrared data to distinguish between snow and volcanic ash and to see vegetation more clearly. Since 1972, images from NASA's Landsat satellite have combined visible and infrared data to allow scientists to study changes in cities, neighborhoods, forests, and farms over time. Visible light images taken by NASA's Mars landers have shown us what it would look like to stand on another planet. They have expanded our minds, our imagination, and our understanding. NASA instruments can do more than passively sense radiation, they can also actively send out electromagnetic waves to map topography. The Mars Orbiting Laser Altimeter sends a laser pulse to the surface of the planet and sensors measure the amount of time it takes for this laser signal to return. The elapsed time allows the calculation of the distance from the satellite to the surface. As the spacecraft flies above hills, valleys, craters, and other surface features, the return time varies and provides a topographic map of the planet's surface. Back in Earth orbit, NASA's ICESat mission uses the same technique to collect data about the elevation of the polar ice sheets to help monitor changes in the amount of water stored as ice on our planet. Laser altimeters can also make unique measurements of the heights of clouds, the top of the vegetation canopy of forests, and can 'see' the distribution of aerosols from sources such as dust storms and forest fires. Finally, visible light helps us to explore the far reaches of the universe that humans could not hope to reach physically. Using visible light, the Hubble Space telescope has created countless images that spark our imagination, inflame our curiosity, and increase our understanding of the Universe.