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sikkemike
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Light doesn't have mass so what's stopping it from going infinitely fast ?
He's saying that c is part of the way the Universe works - but he is going into a bit of detail about the "how". That's where the interesting stuff is.sikkemike said:I don't really get what you're saying
xAxis said:Also didn't Poincare show that if space is homogenous, then there must exist maximum posible speed in nature, because otherwise the causality would be reversed?
Mordred said:Yeah its a little tricky of a term in regards of cosmology this is a cut and paste expaination from "Introduction to Cosmology " by Barbera Ryden.
On large scales, the universe is isotropic and homogeneous
What does it mean to state that the universe is isotropic and homogeneous?
Saying that the universe is isotropic means that there are no preferred directions
in the universe; it looks the same no matter which way you point your
telescope. Saying that the universe is homogeneous means that there are no
preferred locations in the universe; it looks the same no matter where you set
up your telescope. Note the very important qualifier: the universe is isotropic
and homogeneous on large scales. In this context, \large scales" means that
the universe is only isotropic and homogeneous on scales of roughly 100Mpc
or more.
The isotropy of the universe is not immediately obvious. In fact, on small
scales, the universe is blatantly anisotropic.
sikkemike said:I don't really get what you're saying
.nitsuj said:Ah I see,
I misunderstood homogeneous, always thought of it in the sense of mixtures; and was wondering what are the components that are thoroughly mixed sorry for such bad terminology.
In that text you generously posted, it reads as though it is strictly via comparison that space is called homogeneous.
chill_factor said:light can travel at arbitrarily large values in appropriate units. You can make the numbers as big as you want by changing units.
Technically anyone of those is determined by the other two isn't it? Anyway - doesn't that observation just change the question into why the permittivity and permiability are that way?Chronos said:The speed of light is determined by the permittivity and permeability of free space.
... and this changes the question to "why doesn't causality reverse?" It's the same question in different words.xAxis said:Also didn't Poincare show that if space is homogenous, then there must exist maximum posible speed in nature, because otherwise the causality would be reversed?
... I don't see how empirical science can answer this sort of "why" question in the spirit it appears to have been asked. It seems to be a philosophy question more than anything. The exact same question can be asked of any physical constant - or, indeed, all of them together. We see the values we do because we live here. If we lived in a different Universe then perhaps we'd see different values and wonder about them? But there may be limits on the sets of values that make sense - that produce Universes with physicists for example. That's a triple-whiskey discussion right-there!Drakkith said:I don't feel that any of the answers here are going to satisfy you, as they do not answer "why" in a fashion you would accept.
Drakkith said:How does this have any relevance to the thread?
I understood these terms predated field theory?Chronos said:Permittivity and permeability are a consequence of quantum field theory.
Possibly that the coulomb charge and magnetic field are fundamental to... nah, I'll not go there: sounds like a chicken-and-egg argument to me ... you win.They are also fundamental to things like coulomb charge and magnetic field strength.
Never used the word "just" I don't think.It is inaccurate to suggest they are just an alternative way to derive the speed of light.
sikkemike said:Light doesn't have mass so what's stopping it from going infinitely fast ?
But your "point" is wrong- and a bit silly. I was kind of hoping that your first post was a a joke.chill_factor said:i was trying to make a point that fast is relative, you can make things arbitrarily fast in terms of absolute values simply by changing units.
sikkemike said:Light doesn't have mass so what's stopping it from going infinitely fast ?
Astounding claim: how do you know?Photons do have a little mass.
Simon Bridge said:Astounding claim: how do you know?
Citation please - so we know what you are talking about.
Drmarshall said:You don't, until you find out about "radiation pressure"
In the red it is about one pound per Gigawatt
Drmarshall said:You don't, until you find out about "radiation pressure"
In the red it is about one pound per Gigawatt