OT: Expanding universe question.

Maybe not the right place to ask. Or maybe exactly the right place to ask, since I think there are some here interested in this sort of thing? Anyway, be gentle with me :-) We're told that nothing can exceed the speed of light (maybe that's an oversimplification for idiots like me). We're also told that the universe is exanding (again, maybe that's an oversimplification etc.). Now, the universe is rather big, so it seems to me that two things on opposite sides of it could /easily/ be travelling away from each other faster than the speed of light. The only way I can resolve this is to imagine that actually it's space itself that's expanding, and if you had some sort of cosmic tape measure, then you wouldn't measure any movement at all. Is that 'really' what's happening? Is the universe not expanding in what I think is the conventional sense? Everything I can find to read about it just says it's expanding, and doesn't go beyond that.
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On 24/10/16 13:25, Dan S. MacAbre wrote:

No. Its all pictures in your head trying to make sense of sensory data, up to and including dials moving and digital data.
The greatest mistake that nearly everybody makes in this life, is to confuse pictures in their heads with what's really there.
Ok we cant relate to what's there without pictures in our heads., but the problem only arises when we regard those pictures are real in themselves, rather than a 'story about life, the universe and everything'.
Calling a bolt of lightning an electrical phenomena rather than a God's missile, may yield some interesting predictions about how it behaves, but it doesn't make it any more or less 'true'.
AIUI, which isn't a lot, the 'universe;' is 'expanding' but the bits 'furthest away' are very very near the speed of light, so the signals from them are so deeply red shifted they are probably in the audio spectrum.
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The Natural Philosopher wrote:

I used to watch 'Horizon' programs about this, until deciding they were all completely nebulous. Nice graphics and lots of filler. I watched some Brian Cox, until realising he'd gone all the way to Corsica or Sardinia just to tell us that everything is just 'moment in time', at which point I switched off. I tried reading Stephen Hawking, and it was pretty much the same. Weird 'facts' and no explanation. I got pdf files of Einstein's theories, and didn't get further than the 'Riemannian Manifolds' on page 1. I suspect it is completely beyond me, and I should just leave it at that :-)
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On 24/10/16 14:22, Dan S. MacAbre wrote:

That is why I try to insist that Korzybski's insight ("the map is not the territory") is perhaps the most condensed form of a metaphysical position that understands the notion that the world we deal with is a *mapping* of what's really there, not what *is* really there.
Our whole world view is in fačt a *theory* about what the world is.
And nearly all human conflict embodies some aspect of the fact that no two people have exactly the same pictures in their heads.
Science doesn't take us to the truth, but it does allow the worst and most useless ideas to be discarded and the ones that actually work, to be retained.
I've only met with one philosopher who seemed to really understand that and he's dead now. Hilary Putnam.
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On 24/10/2016 14:22, Dan S. MacAbre wrote:

+1.
I read "brief history of time" every few years, and still don't think I understand it.
Andy
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Actually, the problem is that we do not yet have all the data to know what we are doing.
Brian
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On Monday, October 24, 2016 at 2:00:41 PM UTC+1, The Natural Philosopher wrote:

Audio waves are not electromagnetic waves.
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On 24/10/16 14:26, Halmyre wrote:

They are when they come out of my guitar.
The 'audio spectrum' isn't the sound, it's the *frequency of sound*. Normally 20Hz-20hkHz..
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On Mon, 24 Oct 2016 06:26:13 -0700, Halmyre wrote:

He never claimed they were. It seems fairly obvious to me that he meant "in the audio spectrum of frequencies", as in, with a long enough wire antenna[1], you can feed such a VLF EM signal directly into an audio amplifier driving a speaker so enabling one to listen directly to the VLF radio waves without reliance on a detector stage. The detector stage, in this case, being the listener's own ears.
[1] A quarter wave ground plane antenna would only need to be about 37Km long in order to resonate at 2KHz and 15Km long for a 5KHz radio wave.
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On 24/10/2016 17:42, Johnny B Good wrote:

He is still completely wrong though. The 3K *microwave* background is so named for a reason. You cannot see back further than the surface of last scattering where the universe first becomes transparent at about a redshift Z ~= 1500 and a temperature of 3000K give or take.
https://www.scientificamerican.com/article/what-is-the-cosmic-microw/
Only neutrinos would allow us to see past the region where the universe becomes opaque to electromagnetic radiation. It is entirely possible that the extent of the universe is so great that there are photons in very distant regions that can never reach us because the space between us and the emitter is expanding faster than light can close the gap.
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On Tue, 25 Oct 2016 09:05:57 +0100, Martin Brown wrote:

I was merely pointing out that Halmyre's contribution was completely specious and totally beside the point. :-)
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On Tuesday, October 25, 2016 at 6:45:47 PM UTC+1, Johnny B Good wrote:

My apologies. I was addressing what appeared to be the poster's basic lack of scientific knowledge.
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On Monday, October 24, 2016 at 1:25:31 PM UTC+1, Dan S. MacAbre wrote:

It is expanding by stretching (like the surface of a balloon), and it is possible for objects to be receding faster than light, subject to various bits of hand-wavery about how you measure time and distance.
https://en.wikipedia.org/wiki/Faster-than-light#Universal_expansion
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Halmyre wrote:

Amazing. Thanks.
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On 10/24/2016 1:25 PM, Dan S. MacAbre wrote:

You just need to read up on Special Relativity and Inertial Frames.
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newshound wrote:

Okay :-) I've nearly finished Zamoyski's '1812', then I'll find out what an Inertial Frame is. TBH, I think I just don't have the maths.
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On 10/24/2016 2:32 PM, Dan S. MacAbre wrote:

The maths actually isn't that hard, you can probably find a good explanation on a university first year physics site. (It was A level in my day). See "closing speeds" in Halmyre's Wiki link. It's all about points of view!
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On 24/10/2016 14:57, newshound wrote:

The maths is a little tricky, for me it was first year university in applied maths. I'm surprised it was taught at A'level physics.
<https://en.wikipedia.org/wiki/Derivations_of_the_Lorentz_transformations>
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On 24/10/16 14:32, Dan S. MacAbre wrote:

MM. You sort of don't need it.
An inertial frame is simply 'how stuff is when left to itself'
i.e. not accelerated. Or freely falling in a gravitational field.
Relativity IIRC simply states that you cant exceed the speed of light in one inertial frame, but of course there are an infinite number of inertial frames, and things in one frame may seem to exceed the light speed when viewed from another.
But I am not an expert so don't call me out on that explanation.
What you have to understand that what relativity did was blow the idea of 'one space, absolute in dimension;' out of the water.
Rather we have space created by mass. with mass being a form of energy.
So mass/energy/space/time becomes a rather crappy way of looking at something, that we don't really understand.
Penrose gets easier to read when you realise the maths is just 'ways of describing stuff we don't understand' and try not to worry about whether what it seems to say in terms of what is 'really there' is apparent nonsense or not.
Personally I like to think of the world of our perceptions as something like an intersection of 'whatever is the case', with our consciousnesses.
The pictures so produced owe as much to our consciousness and its nature as they do to what is 'really there' whatever that means...
And that's why Gods appear and are anthropic. They are what we stick over the great mystery of the fact there not only is there a universe, but we seem to be aware of it, and of ourselves as beings who are aware of it. That is a very very strange fact.
And that goes back to the original post.
What is *really there* is not only unknown, but it is also in the limit unknowable.
Even if we were completely detached from it and could measure all of it to infinite decimal places, we still would be leaving out one enormous elephant in the room, ourselves. Or at least out conscious minds.
Our very understanding of the basic nature of the world is ultimately pretty much a Judaeo Christian one (I would include Islam, but its really not up there, philosophy wise) that is, we are able to be 'detached observers' of phenomena precisely because we understand the notion of 'pure spirit' or 'holy ghost' (consciousness) as distinct from 'the material world' of e.g. physics.
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On 24/10/2016 3:45 PM, The Natural Philosopher wrote:

Excellent picture.
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