Something to get your brains working :)

[Sam Baker]

Was just wondering to myself.....the creation of galaxies within our universe is expected to be after the big bang some 13 or 14 billion years ago. What would happen if we randomly found a galaxy which is 15 or 20 billion light years away? Would that possibly through science off track and make us rethink what happened or would there be a thought that maybe the big bang was something which set off a new set of galaxies? And perhaps leave us thinking that the evolution of the universe as we know it may have had several steps or even several millions or billions just like the evolution of life? Please enlighten me someone as this is really bugging me

Sam

Sent from my GT-I9505 using Tapatalk

[Qualia]

Don't quote me on this Sam but I think scientist have discovered galaxies further out than 13,000 or 14,000 million light years. The reason this is possible is that although the age of the universe is reckoned to be some 13,700 million years old, the universe itself is thought to have been a smaller place. By taking this feature into account, scientist can say that the light we receive from distant galaxy x has red-shifted by a factor of p (the growth of the universe), so the galaxy is now further out. I think by this method scientists have detected galaxies as far out as some 30,000 million years.

I think another way of putting this is to imagine the universe like a deflated balloon and to mark this balloon with two points, one referring to our galaxy and another point indicating galaxy x. We can say here that the light from galaxy x takes, say, 5,000 million years to arrive to us. Then we begin to pump the balloon with air (the universe explanding). At some point in our expansion, we can say galaxy x is now 30,000 million light years away from us but because the universe was once a smaller place, we were once closer to that galaxy, so the light we actually receive now was beamed out from galaxy x only, say, 10,000 million years ago. As the universe expands we co-move from each other so that after 13,700 million years (the age of the universe) we are now in fact 30,000 million light years away, although the light we receive now is obviously a lot less than that.

I hope what I have written here is accurate and I hope it makes some kind of sense?

[JulianO]

If you mean that we find a galaxy, or even a star, older than the universe is thought to be, then yes, that would cause a lot of head scratching. It would invalidate the concensus model of the big bang, and we'd have to think again.

The current model of the big bang doesn't allow for anything older than 13.8 billion years to exist.

[Zakalwe]

Youre confusing light years (a measure of distance) with years (a measure of time). Objects can exist more than 13Bn light years away as spacetime is expanding all of the time.

[Zakalwe]

the furthest object detected so far is 13.37 giga lightyears away. The problem with decting objects much further away is that the object's light will be red-shifted by a huge amount

[JulianO]

The red shifting isn't a problem, we have the spectrum pretty well covered. The problem is the small number of photons that make it to Earth and the ability to differentiate the distant bright object from a closer but dimmer object given a very noisy signal.

[Zakalwe]

If the Jamea Webb space telescope evwr gets off the ground then we'll have a real opportunity to spot far more distant objects.

[JulianO]

Indeed - the JWST is optimised for seeing in IR making it ideal for redshifted objects (as well as peaking through dust clouds). 

Mind you it has to 

a) be finished

get launched successfully

c) unfold and sort itself out at over a million kilometres away

quite a big ask!

[Zakalwe]

Yes. And they seem to be having all sorts of issues with building it and financing it.

(and apologies for the spelling in previous posts.....am on the mobile and I suffer from dyslexic fingers).....

[Sam Baker]

So the gyst is we have locate entities in the universe which go much further back than the big bang?

Sent from my GT-I9505 using Tapatalk

[JulianO]

No - so far nothing has been found that is older than the big bang, though some things are close.

There are things that are further away than 13.8 billion light years, but that's because the universe is expanding.

[Sam Baker]

How would you be able to see them as it would take such an amount of time for the light to reach us right? So if the big bang was 13.8 billion years ago and an object was more than 13.8 billion light years away we couldn't possibly see it as the light will still be travelling to earth from the moment of creation?

Sent from my GT-I9505 using Tapatalk

[Qualia]

So the gyst is we have locate entities in the universe which go much further back than the big bang?

No, the distances in the universe (measured in the time light travels in a year) are now be very, very large because the universe is expanding, but the age of the universe remains a constant - at the moment.

[acey]

If the age of the universe is 13.8 billion years then the horizon distance is more than 13.8 billion light years, i.e. we can see things more than 13.8 billion light years away. Counter-intuitive, I know, but a consequence of cosmological expansion. The edge of the observable universe is believed to be 46-47 billion light years away. See the wiki page for fuller explanation.

http://en.wikipedia.org/wiki/Observable_universe#The_universe_versus_the_observable_universe

[Sam Baker]

I see so I guess as we can see something which maybe from 13.8 billion light years and 13.8 billion years ago. That object would be at a much further distance by now and we won't be able to see it there until the time comes?

Sent from my GT-I9505 using Tapatalk

[Sam Baker]

With a chamce of not being able to see some of the farthest places due to rapid universal expansion?

Sent from my GT-I9505 using Tapatalk

[Zakalwe]

I see so I guess as we can see something which maybe from 13.8 billion light years and 13.8 billion years ago. That object would be at a much further distance by now and we won't be able to see it there until the time comes?

Sent from my GT-I9505 using Tapatalk

Again, you are confusing light-years (a measure of distance) with years (a measure of time).

http://www.nature.com/news/light-from-farthest-galaxy-yet-discovered-breaks-through-cosmic-fog-1.14017

z8_GND_5296 lies over 30 billion light years from us.

At some point we will not be able to see any further back in time, as the early universe was filled with just hydrogen (with a smattering of helium). Further back from that and atoms didn't exist yet.

[JulianO]

You can see something that is nearly 13.8 billion years old, thats the light from the last scattering, or the cosmic microwave background. That's as far back in time as you can see. Before that time (about 400,000 years after the big bang) light didn't travel far as everything was ionised and light kept getting absorbed. So that's as far back in time as you can see (with light at least).

The first galaxies were formed a few million years after the BB, so they're 13.6 billion years old say, and are 13.6 billion light years away in distance if the universe was stationary.  But it's not, its expanding. So light set off 13.6 billion years ago to come to us, but in the meantime the universe has expanded, and they are now further away because of that. 

Its like talking to someone in a car going from Edinburgh to London, except the only way you can talk is for them to write a note and have it carried by a motorcycle.

They write a message

"Hi, I'm in Oxford", and give it to the motorcyclist, who sets off to you in London. An hour or so later it arrives, and you read it. Are they in Oxford? Well no - they were when they sent the note, but by the time you got it they're probably nearer Birmingham. 

The further they get to Edinburgh, the bigger the error in where they say they are and where they are, as it takes so much longer for the motorcyclist to deliver the message.

[Zakalwe]

You can see something that is nearly 13.8 billion years old, thats the light from the last scattering, or the cosmic microwave background. That's as far back in time as you can see. Before that time (about 400,000 years after the big bang) light didn't travel far as everything was ionised and light kept getting absorbed. So that's as far back in time as you can see (with light at least).

The first galaxies were formed a few million years after the BB, so they're 13.6 billion years old say, and are 13.6 billion light years away in distance if the universe was stationary.  But it's not, its expanding. So light set off 13.6 billion years ago to come to us, but in the meantime the universe has expanded, and they are now further away because of that. 

Its like talking to someone in a car going from Edinburgh to London, except the only way you can talk is for them to write a note and have it carried by a motorcycle.

They write a message

"Hi, I'm in Oxford", and give it to the motorcyclist, who sets off to you in London. An hour or so later it arrives, and you read it. Are they in Oxford? Well no - they were when they sent the note, but by the time you got it they're probably nearer Birmingham. 

The further they get to Edinburgh, the bigger the error in where they say they are and where they are, as it takes so much longer for the motorcyclist to deliver the message.

Great explanation.

To continue the analogy, assume the cars is moving at a steady 70MPH (apologies for the use of archaic measurement!) away from Edinburgh in a straight line. After 1 hour you would expect (and rightly so) that the car would be 70 miles from Edinburgh. Now lets assume that the ground is somehow expanding. After 1  hour, the car travelling at a steady 70MPH, is now 90 miles away. How could it possibly be 90 miles away when it was only travelling at 70MPH?

[Sam Baker]

Fantastic explanation Julian. I feel completely satisfied and understand now thank you so much

Kind regards

Sam

Sent from my GT-I9505 using Tapatalk

[Macavity]

Great stuff! The Wikipedia Article [in this instance] (Ta, Acey!) said much to me.

Thanks J.O. too. Certainly no shame in asking trivial (quite difficult!) questions?

There is too much "number proseleytising" in TV Science? [Just my opinion]

Quite interesting to ponder stuff. The Science can be... *unclear*, at least.