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How Does Light Travel?
universetoday.com ^ | 19 May , 2016 by | Matt Williams

Posted on 05/19/2016 1:06:30 PM PDT by BenLurkin

Ever since Democritus... argued that all of existence was made up of tiny indivisible atoms, scientists have been speculating as to the true nature of light. Whereas scientists ventured back and forth between the notion that light was a particle or a wave until the modern, the 20th century led to breakthroughs that showed that it behaves as both.

These included the discovery of the electron, the development of quantum theory, and Einstein’s Theory of Relativity. However, there remains many fascinating and unanswered questions when it comes to light, many of which arise from its dual nature. For instance, how is it that light can be apparently without mass, but still behave as a particle? And how can it behave like a wave and pass through a vacuum, when all other waves require a medium to propagate?

...

By the late 19th century, James Clerk Maxwell proposed that light was an electromagnetic wave, and devised several equations (known as Maxwell’s equations) to describe how electric and magnetic fields are generated and altered by each other and by charges and currents. By conducting measurements of different types of radiation (magnetic fields, ultraviolet and infrared radiation), he was able to calculate the speed of light in a vacuum (represented as c).

In 1905, Albert Einstein published “On the Electrodynamics of Moving Bodies”, in which he advanced one of his most famous theories and overturned centuries of accepted notions and orthodoxies. In his paper, he postulated that the speed of light was the same in all inertial reference frames, regardless of the motion of the light source or the position of the observer.

(Excerpt) Read more at universetoday.com ...


TOPICS: Science
KEYWORDS: light; stringtheory
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To: I want the USA back

There are a few like that. When I talk to students about energy, I always start out by saying that I am happy to talk about energy, just don’t ask me what it is. Because I don’t know. Nobody does, other than in terms of abstractions, “the ability to do work”, a potential field, a property of matter, the conserved quantity associated with the temporal invariance of the Lagrangian density. But what is it, really, in its essence (and no dodging by invoking Special Relativity)?


61 posted on 05/19/2016 2:22:25 PM PDT by chimera
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To: r_barton
If you are traveling the speed of light in your car and turn on the headlights, do they light up anything? ;-)

Of course not, nor does your horn work........

62 posted on 05/19/2016 2:54:00 PM PDT by Hot Tabasco (#HillaryForPrison-2016)
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To: lafroste

Reflection. Yes, I agree. Only I think of it as a shadow. It is like we are waiting for the next eureka moment, which will change everything.


63 posted on 05/19/2016 2:54:18 PM PDT by T. P. Pole
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To: JusPasenThru

Actually if you look at the night sky, even in the darkest places on Earth, the furthest STARS you can see aren’t much more than 1500 light years away.

The furthest galaxy you can see without a scope may be M81 and it has to be REAL dark and you better have good eyesight.

Occasionally there will be a supernova in some close galaxy that you can see with a scope, that would be the furthest star you can see with a scope. There was one in M82 a few years ago that could easily be seen with a small scope.

The furthest galaxy you can see with a telescope is 3c273.

If I remember right its 2.3 Billion LY. You need a good scope to see it.


64 posted on 05/19/2016 3:01:09 PM PDT by Conan the Librarian (The Best in Life is to crush my enemies, see them driven before me, and the Dewey Decimal System)
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To: r_barton
r_barton said: "If you are traveling the speed of light in your car and turn on the headlights, do they light up anything? ;-)"

Basically, yes.

A real car, consisting of a certain amount of mass, would require an infinite amount of energy to attain that speed.

Slightly more realistically, let's assume that the car is traveling at 99 percent of the speed of light. Then imagine that a person at a distance in front of the car of one light year detects the light coming from the headlights.

Although the light would probably be very dim, the observer would measure the photons as having a speed of 300 million meters per second. He would also detect a pronounced blue-shift in the frequency of the light. Each photon would carry a great deal of energy; much more than would be measured by an observer moving with the car.

Finally, after 3.65 days of observing this unusual light, the observer would be run over by an extremely fast moving car.

65 posted on 05/19/2016 3:34:25 PM PDT by William Tell
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To: MHGinTN
“And how can it behave like a wave and pass through a vacuum, when all other waves require a medium to propagate?” Um, maybe the ‘vacuum’ is not empty.

You're onto something there. As some would say, just because you can't see it, doesn't mean it isn't there. The so-called "vacuum" appears empty to us because we can't detect anything in it. There is a bunch of dark matter in the Universe hiding from us. It fills the so-called "vacuum" with energy fields and light propagates through that medium. It also binds celestial bodies together with electro-magnetic energy. Someday scientists will be able to readily detect dark matter and how it exists within the "vacuum" of space.

66 posted on 05/19/2016 3:39:25 PM PDT by roadcat
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To: JBW1949
not even be a star anymore

It's the pictures that got small.

67 posted on 05/19/2016 3:40:03 PM PDT by MUDDOG
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To: Hot Tabasco

If you are traveling the speed of light in your car and turn on the headlights, do they light up anything? ;-)

Of course not, nor does your horn work........


Just when you get up to speen you find out everyboy ahead is slowing down to watch someboyd change a flat tire.


68 posted on 05/19/2016 3:50:10 PM PDT by Idaho_Cowboy (Nationalism is power hunger tempered by self-deception. - George Orwell.)
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To: Idaho_Cowboy

Sorry speed. I’d blame auto-correct, but it’s just an operator head-space error.


69 posted on 05/19/2016 3:51:18 PM PDT by Idaho_Cowboy (Nationalism is power hunger tempered by self-deception. - George Orwell.)
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To: The_Media_never_lie
"It travels swiftly."

Whereas heavy travels slowly...Thus we have a unified theory...

70 posted on 05/19/2016 3:55:16 PM PDT by SuperLuminal (Where is another agitator for republicanism like Sam Adams when we need him?)
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To: BenLurkin
How Does Light Travel?

Usually in a straight line.

71 posted on 05/19/2016 5:07:17 PM PDT by upchuck (I'm hanging here until my Free Republic 401K is fully vested.)
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To: The_Media_never_lie

“How does one travel light? Never figured that one out.”

One carryon, no checked baggage.


72 posted on 05/19/2016 8:23:28 PM PDT by Redcitizen
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To: NonLinear

That was just a great time to be a scientist. You could do cutting edge research with everyday things like lanterns and copper wire and corks and apples and kites and stuff.


73 posted on 05/19/2016 8:37:27 PM PDT by Yardstick
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To: BenLurkin
How does light travel?
Science Advances Magazine 29 April 2016 - There are many ways to spin a photon: Half-quantization of a total optical angular momentum
74 posted on 05/20/2016 12:29:48 AM PDT by Mr Radical
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To: Steely Tom

Nice explanation.


75 posted on 05/20/2016 1:01:57 AM PDT by jpsb (Never believe anything in politics until it has been officially denied. Otto von Bismark)
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To: r_barton
Your car can not travel at light speed. The faster you go the more massive you become, as you approach the speed of light your mass approaches infinity. So the only way to go at light speed is to have no mass. But another thing happens too. Besides gaining mass time also slows down. So let's say you are traveling along a c/2, half the speed of light. Your head lights would appear to you to be going at c because for you time was slower than for some one stationary. However the stationary observer would also see the head light light traveling at c. There is just no way to get around the universes speed limit, but it might be possible to take a short cut thru a worm hole.

Traveling at light speed is probably not a good idea anyway. Bumping your car into a clump of dust at light speed would release a huge amount of energy, similar to a small nuke.

76 posted on 05/20/2016 1:20:50 AM PDT by jpsb (Never believe anything in politics until it has been officially denied. Otto von Bismark)
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To: jpsb

Thanks.


77 posted on 05/20/2016 5:42:26 AM PDT by Steely Tom (Vote GOP: A Slower Handbasket)
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To: SuperLuminal; Redcitizen
“How does one travel light? Never figured that one out.”

Whereas heavy travels slowly...Thus we have a unified theory...

One carryon, no checked baggage.

Wish I could learn to travel light. I am spoiled by the fact that most of my travel is by car.

78 posted on 05/20/2016 6:04:25 AM PDT by The_Media_never_lie (Apparently, most people are fine with what Obama is doing, while he ignores our problems.)
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To: 6SJ7; AdmSmith; AFPhys; Arkinsaw; allmost; aristotleman; autumnraine; bajabaja; ...
Well, we know that it travels at least one mile per second slower than the speed of dark, because dark can't be see leaving the room when ya turn on the light. Thanks BenLurkin.

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79 posted on 05/21/2016 2:55:47 PM PDT by SunkenCiv (I'll tell you what's wrong with society -- no one drinks from the skulls of their enemies anymore.)
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To: William Tell

Good answer to the car question.


80 posted on 05/22/2016 6:32:03 AM PDT by samtheman (Trump For America.)
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