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What makes light move, is it possible right now to find the source of what makes light move and stop it?
Question Date: 2017-11-01
Answer 1:

It is difficult to answer the "what?" or "why?" questions about nature, and science can most of the time answer the "how?" questions. Light moving is simply a consequence of nature, of natural processes. Our largest source of visible light on Earth is the sun. The sun is a massive fusion reaction, where extreme temperatures and pressures result in elemental hydrogen being converted to helium. This comes with an immense amount of energy, and some of that energy is released as light. It is difficult to say if anything is "making" light move.

Light moves through space and air as a wave and a particle, traveling and interacting with the environment. To stop light is an interesting concept, as it implies dissipating light energy of a given source at one instant. However, it is important to note the first law of thermodynamics, that there is always a conservation of energy. Energy is neither created or destroyed. To this end, if an object absorbs all the light from a source, such as a black asphalt road, that light energy is converted to heat because energy is conserved. To understand more of how light interacts with objects, search for physics lessons on absorption, reflection, and transmission.

Light is very interesting in that it behaves like both a wave and a particle, and this is known as the wave-particle duality. This is a fairly complex topic in quantum mechanics, as light can be mathematically explained in some cases by treating it as a particle, and other cases by treating it as a wave, but the actual behavior is difficult to comprehend. With this in mind, light travels through air at different speeds depending on what medium it is in, and anything that can interact with light, such as water vapor in the sky in clouds, will alter or attenuate propagation, creating dim skies on a cloudy day or pretty colors during a sunset. In this way, natural things such as clouds or man made things such as walls can stop light. Again, to understand more of how light interacts with objects, search for physics lessons on absorption, reflection, and transmission.

Answer 2:

According to the second postulate of special relativity, light is the fastest thing in the universe, and it travels at constant speed in vacuum. This is the nature of light. As long as light is produced, it will move.

We can always “stop” light by turning off its source. Consider stars. Stars produce light by nuclear fusion. When stars die, they no longer emit light. Of course, the light that already got emitted before the star's death will continue on moving until something else stops it---like encountering matter. When light hits an opaque material (like your body), light gets absorbed. This is why you make shadows---your body absorbs most of the light and stops it from reaching the ground. We can also stop light by trapping it by reflection. There is a phenomenon called“total internal reflection.” Put a water-proofed light source under a bath of water. If you point light directly up the surface of water, light will pass through the water. However, as you change the angle of the light source (making it more horizontal little by little) you should reach the critical angle where no light escapes the water. This is the same strategy they use when cutting diamonds to make them sparkle. They also use this strategy for fiber optic cables to make fast internet possible.

Answer 3:

Good question - this one had physicists puzzled for some time. Light has a duality as both particles and waves - it is the particle nature that allows light to move, since waves normally only pass through a medium. You see this as alternating electrical and magnetic fields, which is the wavelike nature of light (electric fields create magnetic fields when changing and vice-versa, so this is how the wavelike explanation works).

Answer 4:

It is actually almost impossible to stop light. Light is "made of" what we call "photons". Photon has no mass, and Einstein's special relativity says that any particle with zero mass must travel with the "speed of light", at least in vacuum.

Light usually slows down a little bit when it travels through a material, but it is extremely difficult to completely stop it. Recently this has been achieved to some extent by using very special techniques.

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