BBC Focus Magazine

[scott fairbrass]

how old is the universe? I know the ''viewable'' universe is 13.6 billion but is there any theries saying the universe could be for e.g. 20 billion or 40 billion years old?

[M Paul Lloyd]

I suppose its a question of how old is the known universe? Rather than how old is the universe?

Because we only know, or at least presume to know, how old the universe is based upon our visisble horizon which gets pushed steadily further back the more distant and ancient our observations become.
Obviously this is limited to the earliest stars which didn't form until some time after the big bang so we have to presume a period of starless time existed before this.

So given that a star with half the mass of our Sun burns its fuel at a rate that will allow it to last for more than 20 billion years and based upon observations of ancient clusters of such stars it seems that they are between 11 and 18 billion years old. However you also have to consider if the universe contains more or less mass with the latter pushing the age still further back in time, possibly to 20 billion years or more?

This is one of the difficulties with the big bang based universe in that it is limited in its potential age but for myself I have long had problems reconciling big bang theory and suspect that as time goes by we will find that the universe is much older than thought possible and therefore no longer fits with the cosmolgical constant.

Sorry I can't be any clearer than that Scott.

[scott fairbrass]

that someing else i dont understand about the big band. how come it's only happend once and not since?

[M Paul Lloyd]

Well in simple terms we have only one (visible) universe and therefore it can be assumed that we only had one big bang.

[Doonhamer]

Science is very confident now that the Universe "exploded" from a single point precisely 13.72 billion years ago, regardless of what MPL in his tinfoil headgear says...

[scott fairbrass]

yes mr doonhammer but what ever direction we look we only see 13.2 billion years whitch can only meen two things 1 were right in the centre of the universe (highly unlikly) or light as been stretched so much we cant see anything older! Ion whitch case then there is probably older galaxies further out that we just cant see!

[M Paul Lloyd]

Yes Scott that is a very good point the universe could indeed extend way beyond the horizon of our visible universe, in just the same way as the horizon on Earth limits our view of the surface. However current thinking suggests otherwise.

I think we are at crossed purposes Doonhamer?
Yes I accept that I may very well be completley wrong to have any doubts about the big bang but even though it is now the accepted model for the universe I still reserve the right to hold with the notion that it may actually turn out to be wrong, which is I believe the proper scientific approach?

Perhaps I should expand on the above comments?
we could try estimating the age of the universe by measuring the Hubble constant (which is the current expansion rate of the universe) and use it to extrapolate back to the point of the big bang. However this relies heavily on the history of the expansion rate and overall density and composition of the universe as we observe it now, which may not be one and the same thing.
So if the universe is 'flat' and composed of more matter then the age of the universe is towards the lower end of any estimate.
On the other hand if the universe has very little matter and curved then it could be much older.
Or if the universe contains matter that conforms to the cosmological constant, then the universe can be even older still.

Measuring the Hubble constant has taxed the greatest minds for many years with the best estimates being from 65 to 80 km/sec/Megaparsec, where a Megaparsec is 1 megaParsec = 3.08568025 × 10 to the power of 22 metres. The best 'guess' being 72 km/sec/Megaparsec.
So based on this information it is possible to say that the universe is between 12 and 14 billion years old.

However If the universe was flat, and contained mostly ordinary or dark matter, then the age of the universe would be about 9 billion years, so age of the universe would be shorter than the age of oldest stars which obviously couldn't be right could it? So either the measurement of the Hubble constant is wrong or the Big Bang theory is incorrect or possibly we need to add a type of matter that conforms to the cosmological constant, but that sadly doesn't work either.

Of course if the lower estimates of globular cluster ages are right then all is well for the big bang even without a cosmological constant.

What helps underpin the expanding big bang unverse is the WMAP data and as long as the origin of large scale structures are right, well then the finer structure of the cosmological microwave background will have a bearing on the density, expansion and composition of the universe as we now observe it.
As it happens the WMAP data has shown these parameters to an accuracy of better than 3% of what is said to be the critical density and applying that level of precision allows an estimate for age of the universe at approximatley 13.7 give or take about 1%...........

The expansion age as given by the WMAP data is therefore greater than that of the oldest globular clusters, so the big bang comes out on top because if the expansion as measured by WMAP had shown the age of the universe to be less than the oldest globular clusters, well something pretty fundamental must be wrong.

So big bang wins............. for now. http://localhostr.com/files/d624ef/tinfoil.gif

[scott fairbrass]

just been listening to the edinbourgh science festival on bbc radio 5 live and this actually popped up and the scientist who sounded like richard dawkins (may have been him, only flicked over dureing adverts in the cricket) said that no1 knows the exact age of the uni and there is nothing to suggest that the uni could go on for ever!

[scott fairbrass]

oh and doonhamer science once told us that the atom was the smallest thing in the universe that the earth was flat and that the sun orbited around us! If no one had asked questions about them results then we wouldn' be were we are now in our knowledge of the universe around us!

[The Beige Avenger]

..... science once told us that the atom was the smallest thing in the universe that the earth was flat and that the sun orbited around us! ....

Science never told anyone any of those things. People did.

[Shadowwolf]

And often those people were working with the best available evidence at the time which is all they can do.

It may not be the whole story, there may be a radical alteration of how we view what came before, but until we have that evidence we go with what we can tell and leave the rest to idle speculation. The gaps and what may be, tend to be the domain of cranks who have found a safe place to hide their pet notions.

Scientists will ask questions, are always asking questions, it is how the discipline works. When atoms were confirmed they were the smallest known thing in the verse and right at that point there was someone wondering if there was something smaller inside them and would check this out when the tools became available. All discovery is provisional.

That said, there are some areas where the evidence for a certain event just keeps building and building such that the chances of it being completely incorrect are rather small and get smaller as we find further confirmations.