Astronomers tell story set a LONG time ago in a galaxy far, FAR away The Hubble telescope has detected starlight that comes from a galaxy 13.2 billion light-years away, scientists reported today. The galaxy is believed to be the most distant object that humans have ever seen, says the paper in the journal Nature. In the big image at left, the many galaxies of a massive cluster called MACS J1149 …
"The Hubble telescope has detected starlight that comes from a galaxy 13.2 billion light-years away... the light shows the galaxy as it was 13.2 billion years ago, when the galaxy itself was about 200 million years old and the universe was only 500 million years old, 3.6% of its current 13.7 billion years, and emerging from a cosmic dark age"
At 13:34 'Bored_Stupid' said, "just makes me go 'Woooaaaaahhhh' at times. Getting your head round a gazillion transistors on a chip is peanuts compared to this stuff.!"
This might make your head spin a bit more... Don't think that this galaxy is, as we type, 13.2 billion light years distant. It's probably much closer to 42-45-ish billion light years away right now! (The current distance to the most distant object we can see is about 46 billion light-years). The Universe has a 'diameter' of about 92 billion light years (think 'expansion'), not the commonly held misconception that it's diameter is 2 * age i.e. ~26 billion light years :)
It might have been useful if the article author had delved a little deeper into this as the article's opening sentence could be read as to imply imply that the galaxy in question is currently 13.2 billion light years distant, when it isn't. That's just the age of the light we are seeing. The galaxy has since receded much further from us.
It might have been useful if the article author had delved a little deeper into this as the article's opening sentence could be read as to imply imply that the galaxy in question is currently 13.2 billion light years distant, when it isn't. That's just the age of the light we are seeing. The galaxy has since receded much further from us.
In truth Bored_Stupid knows much of this, but then you get into questions of speculation, assumption, theory etc - all of which may be right or may be wrong.
And once the uncertainty comes in, once it just becomes theory, then it ceases to blow my mind.
So at the risk of sounding stupid, I have always wondered about this:
Can a visible object Star, Galaxy, Cluster et-al. say for example our Galaxy here, be visible at its calculated 13.3 Billion Light Years and again some where beyond that point.
No perhaps not here on Earth per-say, but if I were somewhere between here and this Galaxy could that even be possible?
'The current distance to the most distant object we can see is about 46 billion light-years. The Universe has a 'diameter' of about 92 billion light years.'
So you are telling me the universe has expanded (or is expanding) at greater than the speed of light? If the universe is ~13 billion years old, surely it can't be more than 26 billion light years in diameter?
And we are RIGHT IN THE MIDDLE?
It's actually only the 'observable' universe which is currently about 93 billion light years across, the rest of it we can't see as the light coming from objects further away (than 13.7 billion light years some 13.7 billion years ago) hasn't had time to reach us yet. So yes the universe at very large distances is expanding (moving away from us) faster than light relative to us, we will never get to see most of it. The image of this far distant galaxy will eventually fade away (become more redshifted) never to be seen from here again.
It is doubtful that 'we' are in the centre of the universe (contrary to many religious credos) but it is remotely possible. So yes, space is mind boggling big, probably even bigger!
"It is doubtful that 'we' are in the centre of the universe (contrary to many religious credos) but it is remotely possible. So yes, space is mind boggling big, probably even bigger!"
As I understood it, we *are* in the centre, but so is everything else, only because to have a centre, you need to define an edge.
Easiest way to consider it is to think of yourself on the surface of the earth - are you in the middle of its surface? Is anyone?
> So you are telling me the universe has expanded (or is expanding) at greater than the speed of light?
That's what "inflation" is about. Inflation "expands all of space quickly" so that objects initially "nearby" are ripped away, past their respective "cosmological horizons" - they become invisible to each other (note that this is what is seen on a slow scale right now as all the far galaxies start dropping away over our cosmological horizon, becoming exceedingly redshifted and more and more invisible)
Once "inflation" has gone away (by some Mechanism of Mystery), the "cosmological horizon" of each object slowly expands, and objects become visible to each other again at some time after inflation stop time. This mechanism ensures that:
- The universe is initially "small", objects are in contact with each other during a brief time, leading to a good mixing, thus universally valid laws of nature and isotropic cosmic background later on.
- The universe gets large quickly, thus avoiding premature recollapse and making spacetime flat at large scales
This all fits the observations well, though whether it fits what actually transpired is anyone's guess.
Now, if anyone can explain why expansion is valid on cosmological scales only and does not stretch "thightly bound systems" as the galaxy, that would be nice.
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The universe is infinitely big, therefore everybody is right in the middle of the universe, that's the funny thing about infinity. Anybody Anything living on that galaxy 13.2 billion light years away can also see 13.2 light years in all directions.
Consider this about infinity, the set integer numbers is infinite, but logic would say that the set of even integer numbers is only half the size of the set of integer numbers, yet the set of even integer numbers is also infinite. A clearly defined subset of infinity is also infinity. Pass this on to your friends, ideally at 10:30 on Saturday night in the pub for best effect.
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I have no degree in physics so please be kind.
Before expansion kicked in, everything in the universe was relatively close together. Presumably this means everything in the universe was affected by the gravity of everything else in the universe to a much greater degree. How is it then that the force behind expansion ever overcame gravity?
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"That's actually extremely straightforward. The expansion is a feature of the metric..."
That is an excellent post, and explains the limitations of universal expansion very well. What makes your post exemplary, however, is the simple layman's explanation that follows the more technical one. I've found that experts on a topic rarely have the ability to explain their topic of expertise in terms non-experts can understand. It is this ability, to explain a complex topic in an easily-understood manner, that is the rare and precious skill of the true teacher. Be proud that you have this skill.
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<<<<That's actually extremely straightforward. The expansion is a feature of the metric on cosmological scales, which we're taking to be Robertson-Walker - that is, expanding sheets of flat (or spherical, or hyperboloidal) 3-space. >>>>
I take that to mean that the space-time grid stretches less within galaxies because their internal gravitational attraction between "stars" resists the stretching ?
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"So you are telling me the universe has expanded (or is expanding) at greater than the speed of light? If the universe is ~13 billion years old, surely it can't be more than 26 billion light years in diameter?"
This oldish article might help here. [Warning. PDF!]
"And we are RIGHT IN THE MIDDLE?"
Possible, but unlikely. We are however right in the middle of our own observable universe :)
And we are RIGHT IN THE MIDDLE?
Unlikely. That's just an effect of isotropy. If everything is receding at an equal pace from everything else then every place seems to be the centre of the universe. No doubt many other planets have astronomers that are still struggling with heliocentricity, so I wouldn't feel too bad about the mistake you made :)
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A highly magnified candidate for a young galaxy seen when the Universe was 500 Myrs old
"...the gravity of foreground objects warps and magnifies the light from background objects"
How do you magnify light? Images can be magnified by deflecting light. Light can be amplified, diffused or concentrated, but magnified? Surely "magnified means "made bigger", which could only be accomplished by adding more photons from somewhere (thus effectively meaning the same as "amplified"). Or have I missed something?
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