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  1. How can light (or electromagnetic radiation) travel through a vacuum when there is nothing there to act as a medium, and do so forever in all directions? For example the light coming from a star millions of light years away. Light is observed as traveling at velocity v=c, according to the second postulate of special relativity. But according to ...

    • Theory of Light in The 19th Century
    • Double-Slit Experiment
    • Electromagnetism and Special Relativity
    • Einstein and The Photon
    • Wave-Particle Duality

    During the Scientific Revolution, scientists began moving away from Aristotelian scientific theories that had been seen as accepted canon for centuries. This included rejecting Aristotle's theory of light, which viewed it as being a disturbance in the air (one of his four "elements" that composed matter), and embracing the more mechanistic view tha...

    By the early 19th century, scientists began to break with corpuscular theory. This was due in part to the fact that corpuscular theory failed to adequately explain the diffraction, interference and polarization of light, but was also because of various experiments that seemed to confirm the still-competing view that light behaved as a wave. The mos...

    Prior to the 19th and 20th centuries, the speed of light had already been determined. The first recorded measurements were performed by Danish astronomer Ole Rømer, who demonstrated in 1676 using light measurements from Jupiter's moon Io to show that light travels at a finite speed (rather than instantaneously). By the late 19th century, James Cler...

    In 1905, Einstein also helped to resolve a great deal of confusion surrounding the behavior of electromagnetic radiation when he proposed that electrons are emitted from atoms when they absorb energy from light. Known as the photoelectric effect, Einstein based his idea on Planck's earlier work with "black bodies" – materials that absorb electromag...

    Subsequent theories on the behavior of light would further refine this idea, which included French physicist Louis-Victor de Broglie calculating the wavelength at which light functioned. This was followed by Heisenberg's "uncertainty principle" (which stated that measuring the position of a photon accurately would disturb measurements of it momentu...

  2. There are at least two ways that we know light can travel through a vacuum. The first is by observation of the Sun and other stars. Astronauts have measured the pressure in outer space and found that there is a very good vacuum, much better in fact than that which we can easily make on earth. The second is through observations on earth.

  3. Light can travel through empty space. Unlike sound, which needs a medium (like air or water) to travel through, light can travel in the vacuum of space. Light travels in straight lines. Once light has been produced, it will keep travelling in a straight line until it hits something else. Shadows are evidence of light travelling in straight ...

  4. May 2, 2014 · Light may seem to be an exception, leading many to say that light is a wave that can travel through a vacuum with no medium. Light doesn't use EM fields as its medium; light IS an EM (electromagnetic) wave. Maxwell's equations tell us that a magnetic field changing in time causes an electric field to change in space, and an electric field ...

  5. Apr 24, 2017 · A Ray of Light. When an electromagnetic source generates light, the light travels outward as a series of concentric spheres spaced in accordance with the vibration of the source. Light always takes the shortest path between a source and destination. A line drawn from the source to the destination, perpendicular to the wave-fronts, is called a ray.

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  7. May 19, 2016 · Light actually “slows down” every time it has to travel through anything but a vacuum. Look up Cherenkov radiation to see what happens when light initially travels faster than it can through a ...

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