# What is the literal speed of light?

Asked by ChaosCross (2340) February 12th, 2010

Certainly it is incredibly fast, but some literal numbers would be appreciated.

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3.0*10^8 meters/second, or more specifically, 299,792,458 meters/second. A meter is defined as 1/ 299,792,458 of the distanced traveled by light in one second.

holden (8442)

299 792 458 m / s thanks guys!

ChaosCross (2340)

In vacuum. Slower in other media.

Rarebear (25144)

Someone correct me if I’m wrong, but as I understand it, light has never been measured at the exact same speed twice. Some believe it’s actually speeding up.

@RealEyesRealizeRealLies I have never heard anything like that. It just moves at different speed depending on the medium.

pat (89)

@RealEyesRealizeRealLies Well many people believe many things. But the speed of light in a vacuum is a constant.

In terms of not measuring the exact speed each time, there is always a variance in experimental measurement, but it will statistically be the same.

Rarebear (25144)

“Speed of Light May Not Be Constant, Physicists Suggest”

http://www.sciencedaily.com/releases/1999/10/991005114024.htm

Ria777 (2677)

@Rarebear

Yes that’s what I’ve heard, that light speed is an averaged statistic.

@Ria777 I remember that talked about a decade ago. I’m not a physicist, but I am a physics geek. As far as I know, it’s never been confirmed.

Rarebear (25144)

@RealEyesRealizeRealLies Right, but it’s know to an extremely high degree of accuracy.

Rarebear (25144)

@Ria777

Funny that article says just the opposite of what I heard in a podcast, that light is traveling slower. The Universe accelerating was the very same premise used to determine it moving faster.

@RealEyesRealizeRealLies What podcast did you listen to? I’d like to hear it.

Rarebear (25144)

@Rarebear

Oh jeeze, I don’t know the exact one, but it was Terrence McKenna from the psychedelic salon. He’s got a bunch on there.

Look for one’s explaining his Time Wave Zero theory. He talks about light speed in those.

Terence McKenna (who I, believe it or not, largely respect) has said lots of whacked-out things. and he may just have speculated, anyway. he did do a lot of speculation.

Ria777 (2677)
Rarebear (25144)

@Ria777

Time Wave Zero is Math.

@RealEyesRealizeRealLies: using math, I could draw up plans for an invisible flying saucer. that doesn’t mean that I can actually build one.

Ria777 (2677)

@Ria777

It doesn’t limit your vision to pure speculation either.

@RealEyesRealizeRealLies: yes, you can prove true things with math. you can also “prove” wrong things with math. you can’t trust anything you use math to express any more than you can trust any statement made with words.

Ria777 (2677)

186,000 MPS.

DixieRock (183)

@Rarebear: if another part of the universe, way beyond anything we could see, had a different cosmological constant (which would make it neither cosmological or constant), could we tell?

likewise, could we tell that the speed of light couldn’t change in the future or change suddenly in the past? (as opposed to slowly, as the article I linked to speculated.) not rhetorical question. I would really like to know if you know.

Ria777 (2677)

I can see it not being a constant (doppler effect, refractive index, quantum gravity), but how is it not cosmological?

I take the cosmological part of “cosmological constant” to mean the whole of the cosmos, versus just part.

Ria777 (2677)

the speed of light is not absolute. it can be slowed down, and in some labs, light has even been stopped and frozen in place and then set in motion again.

its top speed is 186,000 miles per second, however through some materials, such as diamonds it can be as slow as 36 miles per hour.

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@Ria777 These are good questions, actually, and the answer is no, we don’t know. The speed of light could certainly have changed since the Big Bang. And if you believe the multiverse theories there could be another universe with different constants than our own.

Rarebear (25144)

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