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How much cant we see?


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i suspect that the universe is absolutley imense with so much that remains, to us, unseen.

this question, just like the universe, is also imense to the fact that none of us can never really answer it only ponder on it and wonder.

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I'd tend to agree with Chris - from what I've seen on documentaries, we only see a tiny fraction of what is out there - first of all, the visible spectrum is only a minute fraction of the electromagnetic spectrum. There's the issue of dark matter, and distant objects only visible with the most powerful telescopes. If I think about it too hard my brain begins to hurt:)

Although I'm a church member I'm not really that religious but one of our church members did say - "God only lets you see what he wants you to see" - read in to that what you will:)

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I listened to a radio 4 comedy show a while ago and on it was Marcus Chown.

He said we roughly know about 1% of all there is to know in the Universe. But hey that's not all that bad, as at least we *think* we know what we don't know.

But I suppose for observing the galaxy/universe we have no idea what we're missing out on stuck down here.

Edited by johnrt
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Isn't the universe always expanding aswell? So there's a strong chance that, even if we make the huge leaps in technology and space exploration necessary to go much further than our solar system, we will never know 100% of what the universe contains.

Speaking of that, I've always thought, hypothetically if there was a rocket built that could travel faster than the rate the universe was expanding, when it reached the edge, what then? I've always imagined there would be a comic moment like in that Truman Show film where Jim Carey's boat just bounces off the wall.

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Is the Universe expanding? It may be dense enough for the expansion to reverse when gravity overcomes the inertia from the Big Bang. Assuming of course you believe in the Big Bang theory. There are a growing number who consider the Big Bang as an inappropriate part of the GUT to explain a growing number of observable phenomena.

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Is the Universe expanding? It may be dense enough for the expansion to reverse when gravity overcomes the inertia from the Big Bang. Assuming of course you believe in the Big Bang theory. There are a growing number who consider the Big Bang as an inappropriate part of the GUT to explain a growing number of observable phenomena.

You mean the number of big bang doubters has grown from 0.00001 percent of professionals to 0.000015? icon7.gif Of course, they might be right but the BB theory arises out of observation even more than theory.

The universe may indeed go into big crunch mode but the observational evidence points the other way - and suggests that we are going into a runaway expansion from which there will be no return. We need to remember that documentary makers are fixated on the scenario which begins, 'Until now scientists have slavishly believed in the (insert whatever, BB in this case) but tonight on Forefront Of The Future we present startling new evidence form a largely ignored genius, Professor Diggsbury Squitt, who shows overwhelmingly that science has been WRONG! What follows is some threadbare hypothesis at least thirty years old and crushed out of existence by a ton of mainstream evidence. Which is why reading books is better than watching telly, really.

The observable universe is defined as ending at that distance from Earth at which the expansion of the universe exceeds the speed of light.

As amateurs using visual instruments we need to avoid the plane of the Milky Way, hence the spring galaxy season in which the MW is lying down for us making the zenith more transparent. In a 4 inch scope galaxies at much more than 60 million LY are getting faint but the diehards could hunt down a quasar at way more than that. Just don't expect to be noting down any interesting surface mottling!!!

On the other hand, the contents of the MW ae rather nice, are they not??

Olly

Edited by ollypenrice
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Some interesting info there Olly, thanks. I agree about telly programmes, they clearly want to sensationalize any possible departure from the mainstream. However I get the impression that you have made an assumption that my comments are entirely derived from TV based research which is incorrect.

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Some interesting info there Olly, thanks. I agree about telly programmes, they clearly want to sensationalize any possible departure from the mainstream. However I get the impression that you have made an assumption that my comments are entirely derived from TV based research which is incorrect.

Forgive me, no, I was not referring specifially to your post though it rather did read that way. Sorry.

Olly

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Depends on what is mant by whate we can see.

Us lot sat in various locations with 3-16inch scopes, Nice big radio dish, something like Hubble/Chandra/Herschel/Spitzer.

The hubble deep sky and ulltra deep sky revealed a lot, mainly that even empty bits weren't empty.:)

The new generation can "see" further. Think that the oldest galaxy seen is actually not that long:confused: after the big bang and is a puzzle (something like 600 million yrs comes to mind) and it is not expected that any structure would have formed in the short time.

Looking much further is a problem, as early on the material was too hot/dense/something for light to escape it. This cooled and light was able to "escape" (wasn't absorbed almost immediatly) so the universe became transparent, then matter condensed into into the galaxies etc we expect.

This early time in effect it acts as a barrier. We can only (possibly) see this end of it, we cannot see through to the front.

As to how far in the future we will see partially depends on expansion and the Hubble const. If distance is sufficent then at a given point (R=c/Ho) objects will be receeding from us at faster then light:icon_scratch:;):p. The Hubble radius. Equally the Hubble constant isn't constant and in the short ime we have been around we don't know enough to know how it will vary.

Still the universe operates on a time scale different to mankind. We have worked out that the universe is expanding/dynamic on red/blue shift but I bet Andromeda looked much the same 10,000 years ago.

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Not sure whether you saw it when it was posted on the BBC science pages about a week ago - but the PLANCK telescope data has now been released. Basically it seems most of what we could see is shrouded in dust & gas from our own galaxy which also rises quite high from the galactic plane.

Nice picture, but no useful scientific data can be drawn from it (yet)

PLANCK telescope:

BBC News - Planck telescope reveals ancient cosmic light

Edited by Uranium235
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What we see or what we dont't see arises a question in itself. What we see with our own eyes or with all the instruments we've invented?

Either way, i'm sure we only see a small fraction of what's out there.Most of the information is absorbed in the way, is blocked by other powerful sources inbetween or is not reeived because we simply didn't invented the means to detect and interpret the information/radiation.

If by see you mean to see with our eyes... than you are reducing substancially the universe that we can perceive, just because our eyes are only sensitive to a very small fraction of the radiation spectrum.

Edited by Rui
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Going back to the original question about gas clouds, nebulae etc; Olly Penrice is pointing everyone in the right direction. Our view in the plane of our own galaxy is compromised by the density of stuff we are trying to look through. So in those directions a lot is blocked. But out of the plane of our Galaxy there is a lot less to block the view. So say 30-40 degrees is the thickness of the galaxy, we have pretty unobstructed views over about 3/4 of the available sky. Hence we can easily see galaxies - lots of them.

Of course these galaxies have their own dust and gas clouds, so we can't see into them very well, even if we had the resolution, but we can see that they are there. The Hubble Ultra Deep Field shows a vast collection of galaxies, just by looking hard at a fairly blank bit of sky. Hubble only has better seeing, less light pollution and colder cameras than us - any gas or dust is equally a problem for Hubble.

So we can't see dark matter, we can't easily 'see' radiation far outside the visible (at least as amateurs), and we can't see beyond the light horizon of the universe. All interesting and exciting topics. But as to how much of the universe is blocked to us by gas, dust and stars - it is not so much I think.

old_eyes

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Extra-galactic sources lose about 10 per cent of their light to intervening dust etc.

In the plane of our Milky Way, we can only see to a distance of up to about 3000 light years, because of absoprtion.

(Source: Fundamentals of Cosmology, by James Rich)

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