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How Does Light Travel Through Space?



Every point of light you see in the sky is an entire world sending out energy in the form of light. Your ability to perceive this light even across such vast distances says a lot about not just the nature of light, but how powerful the sources of that light really are. Here’s what it takes for light to travel through space.



1. Photons may be particles, but light travels as a wave.
The double-slit experiment is a famous one for good reason: it demonstrated that light can behave both as individual particles and as a wave. When light travels through space, it propagates as a wave, but in a different way than other types of waves. Sound waves, for example, need a medium to interact with, and since there’s not enough densely packed matter in space for sound to travel on, soundwaves don’t carry through a vacuum. Light waves, on the other hand, don’t need anything to travel through, so they can move quite easily through space.

2. There’s nothing for the light to interact with, so it travels on and on.
Since the light doesn’t need a medium to travel with, it isn’t hindered in any way and will keep on going. It won’t dissipate, and it will continue to expand out forever.



3. Stars send out light in every direction.
If light doesn’t dissipate, why do some stars appear dimmer? This has to do with the amount of light we receive from the source. The light from a distant star is being sent out in all directions in a spherical configuration, and it will fill the entire space afforded to it. This means that for a star that’s very distant, only a tiny sliver of the light being sent out actually reaches our eyes. The light itself hasn’t dimmed on the way; the amount we receive has reduced.
 
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Nice.

Many like to refer to light packets, where photons travel in great numbers, even when diminished by distance by the inverse square law.

But some of those photons do become absorbed or scattered. The dark regions in your nice galaxy image are very likely due to photons that were absorbed or scattered by a cloud of gas and dust. This dimming effect, along with specific bands of scattering, provide astronomers with very useful information of these nebulae.
 

Lucille

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Dec 9, 2019
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Every point of light you see in the sky is an entire world sending out energy in the form of light. Your ability to perceive this light even across such vast distances says a lot about not just the nature of light, but how powerful the sources of that light really are. Here’s what it takes for light to travel through space.



1. Photons may be particles, but light travels as a wave.
The double-slit experiment is a famous one for good reason: it demonstrated that light can behave both as individual particles and as a wave. When light travels through space, it propagates as a wave, but in a different way than other types of waves. Sound waves, for example, need a medium to interact with, and since there’s not enough densely packed matter in space for sound to travel on, soundwaves don’t carry through a vacuum. Light waves, on the other hand, don’t need anything to travel through, so they can move quite easily through space.

2. There’s nothing for the light to interact with, so it travels on and on.
Since the light doesn’t need a medium to travel with, it isn’t hindered in any way and will keep on going. It won’t dissipate, and it will continue to expand out forever.



3. Stars send out light in every direction.
If light doesn’t dissipate, why do some stars appear dimmer? This has to do with the amount of light we receive from the source. The light from a distant star is being sent out in all directions in a spherical configuration, and it will fill the entire space afforded to it. This means that for a star that’s very distant, only a tiny sliver of the light being sent out actually reaches our eyes. The light itself hasn’t dimmed on the way; the amount we receive has reduced.
Yes, think of a prism.
 

Jzz

May 10, 2021
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Sara Rayne, This is a thought provoking article, albeit a little misinformed. “Every point of light you see in the sky is an entire world sending out energy in the form of light.”

This is an interesting enhancement on Huygens’s original statement which states that:

“Every point on a wavefront is a source of wavelets that spread out in the forward direction at the same speed as the wave itself. The new wavefront is a line tangent to all of the wavelets.”

This principle works for all wave types, not just light waves. Another over simplification appears to be your statement that: “Light waves, on the other hand, don’t need anything to travel through, so they can move quite easily through space.”

Even Einstein admitted that light needed electric and magnetic fields to travel through. My question is, “Why bring up this topic of fields at all?” Look at Dark matter. Have a real good look, examine it closely. What you will find is that Dark matter has exactly the same properties that the aether was once said to have. It exists everywhere, 85% of the mass of the Universe is made up of dark matter with the remaining 10% made up of cold objects such as clouds of hydrogen or dwarf brown stars and so on, solid matter such as our Galaxy and solar system account for just 5% of all matter in the Universe. Dark matter was discovered much before relativity came on the scene. The point is that with so much dark matter in the Universe, light should not be able to propagate at all. It should be blocked out in every direction. Instead, light travels through dark matter without apparently experiencing any interaction at all. This property of Dark matter is the reason that we know anything at all of the Universe we live in. Further, Dark Matter has all the characteristics of a true field and not an oscillation of two fields, the electric and the magnetic. If Dark Matter is made up of electric di-poles it would fulfil all of the properties of an electromagnetic field and still be a physical manifestation as required by the classical definition of a field, occupying every point in space. If you want to learn more about how light propagates, you cannot do better than to read my paper on the “Electromagnetic Universe” a link to which is provided below.
 
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Numbered mile marker-like light fronts, developing flexible accordion-like corridors, are space-time travelers traveling as two way streets (+/-) of time throughout space. Externally, they travel into the future (+) (into futures (+)). Internally, they travel into the past (-) (into pasts (-)). The net is the constants of 'c' ((+/-) 186,000mps) and 't = 0'. Any other space-time traveler (t = 0) exists in the observable past (-) of his destinations upon departures, bound to travel an observable future (+) to arrivals everywhere situate 'Now' (t = 0). He travels futures (+) to arrivals (always equal distant ('1/2') in horizon between ultimate horizons). He always observes his departure point to travel pasts (-) (recoiling, rebounding, in time past (-)) in order to arrive in all light-time pasts (-) relative to him -- always pointing toward the collapsed horizon of ultimate origin -- behind him in space-time.

The traveler traveled ahead ascending into a future (+) and toward radius physic '1/2'. At once, the traveler traveled behind him descending toward and into a past (-): a past pointing ultimately in descent toward the collapsed horizon of infinity and a superposition dimension of origin. Upon all arrivals he looks out to the surrounding universe and finds himself (t = 0) observably centered (t = 0) (radius, physic, '1/2') between negative time (-) horizons, exactly the same horizon, and observably surrounded by pasts (-) to unobserved and unobservable futures (+), to Now (t = 0) (radius, physic, '1/2'). To the Universe (U) and universe (u), he never leaves center. To them he will always exist at departure point, a. k. a. beginning (Hawking's "Grand Central Station" with its centrally located special "clock" (t = 0)).

The Traveler traveled the numbered mile marker-like light fronts, the flexible accordion-like time corridors, as a space-time traveler traveling two-way streets (+/-) of time through space.
 
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Aug 14, 2020
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Numbered mile marker-like light fronts. "Flexible accordion-like light-time corridors," "two-way streets (+/-) of time through space." Time tunnels through space. Wormholes. 4-dimensional tractable warp (tractable bubbles of....) space-time. We can actually move, go in motion, travel, whether just a little, or titanically big time. All the same if and when internally self-powered (self-accelerative) in and through universe (which itself appears the prime example, prime show, of hyper space-time plane . . . down plane to a physic, or physics, of "self-acceleration" (and/or "inertialessness")). Driving the environment versus being driven by environment (such as particles being closed systematically controlled by and externally driven by the forces of the LHC) makes all the difference.
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It's a multifaceted, multi-dimensional, Multiverse Universe.
 
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