how old is the universe?

[astropete]

i was just looking at the new pics from nasa showing galaxies from about 10 billion light years away and had a thought.

this is that thought........ we say the universe is 14-16 billion years old give or take a few years, now if the space telescope can "look" in a particular direction and see galaxies 10 billion light years away, surley if the scope did a 180% turn around the opposite must be true, then if so those galaxies are 10 billion light years away, but how? given the fact the universe is only 14-15 billion years old, how can we have a universe thats over 20 billion light years across? could my thinking be wrong?

any reason why i may be wrong please help.

[Matthew.Blake]

It expanded in more than one direction at once so 15 billion years in one direction, 15 billion in the other hence 30 billion light years across with us dead centre....

Since we are not dead centre, let's just say that in the initial stages it expanded at faster than the speed of light in some hyper inflation fudge.

[acey]

Not quite.

First, it doesn't actually make a lot of sense to say that a galaxy is 10 billion light years away - it probably isn't there any more.

It does make sense to say that the light has taken 10 billion years to reach us. But space has expanded a lot during those ten billion years. If we were to image that our own galaxy has been around for ten billion years, and we wanted to say where the other galaxy was 10 billion years ago, we'd find that the two of them were a lot closer together than they are now.

Confusing, eh?

Astronomers talk about redshift, since that's what they actually measure. Turning that redshift into a distance makes sense for nearby objects, not much sense for distant objects. But the press office wants a distance, not a redshift.

So the astronomers say something like "we're seeing this galaxy as it appeared 3 or 4 billion years after the Big Bang". And that maybe gets turned into "this galaxy is 10 billion light years away".

The size of the observable universe is not its age turned into light years and multiplied by two (27.4 billion light years). It's larger, because of cosmological expansion, by a factor derived from big-bang cosmology.

This Wikipedia article gives the present radius of our observable universe as 46.5 billion light years, ie diameter 93 billion light years.

Observable universe - Wikipedia, the free encyclopedia

[skye at night]

All I know is it started on a Tuesday!

Steve

[ollypenrice]

Yes, this is always a tricky one to explain neatly. Here's my attempt; at first glance you might think that something from which light set out 10 million years ago would be ten million light years away. But it isn't. The universe is expanding. Not only is the 'destination' of the light getting further away during the light's flight but the point from which it set off is receeding as well. Space is expanding not only in front of the photon but also BEHIND it. I think it is that idea that gets overlooked.

However, an earlier post talks of the universe as if it had a centre and an edge. It has neither. Our minds, firmly rooted in local circumstances, don't like this - but as the Big E said, 'Common sense is just the name given to that set of prejudices accumulated by age 18.' (Not guaranteed verbatim).

Olly

[vhbelvadi]

Hold on, I don't get it.

How would you connect the age of the universe and the distance between celestial bodies?

[Matthew.Blake]

Hold on, I don't get it.

How would you connect the age of the universe and the distance between celestial bodies?

d=vt

[vhbelvadi]

d=vt

Guess my brain had got rusted!

[themos]

It does make sense to say that the light has taken 10 billion years to reach us.

Except, and this will confuse everybody not yet confused, that it takes light precisely zero time to go anywhere (according to a clock carried by the photon).

Ultimately, simultaneity itself disappears for events that happen far apart. Which events do we have here? The emission of the light OVER THERE and its detection OVER HERE. These events are connected by a "light-like interval". You can get any time value and space value you like for this separation by just going to different reference frames. There's one reference frame that is most natural/convenient to use and that is the one where OVER HERE is the origin and always has been. I guess in that reference frame you can talk about light having taken so many billion years to get here in the sense that that's what a clock staying OVER HERE for all past times would read.

If I got this wrong, it would be very embarrassing :-)

[George Jones]

A preferred notion of simultaneity is picked out by symmetry, mathematical and physical. Physically, events are simultaneous if observers at these events measure (after subtracting off peculiar velocities) the same temperature for the cosmic microwave background radiation. This gives a three-dimensional spatial "now" for any value of cosmic time. Or the other way around.

So it is natural to talk about the time difference between two different (hyper)surfaces of simultaneity.

[themos]

Yes George, that's good, using the co-moving observer, I guess.

This may be helpful

Light Travel Time Distance

[AstroTiger]

The generally accepted age of the universe is 13.7 to 14 billion years old.

The reason why the universe has expanded further is at the time of big bang the universe was thought to have expanded 42 billion light years (4 times the speed of light)

The edge of the observable universe i would have thought would be around 14 billion light years since, light would not have had the time to travel further than this since the birth of the universe.

If however we are able to observe much beyond this, my argument then is that that is not part of "this" universe and that it had been around to transmit light before the big bang actually took place.

Yes, this is another of my theories. If we could see much further than that hubble picture was taken (the 8 hour exposure) then in my mind that would possibly prove either their is sense in my idea.

OR we are wrong about the age of the universe.

[Euan]

Since we are not dead centre, let's just say that in the initial stages it expanded at faster than the speed of light in some hyper inflation fudge.

I've got a real problem with the inflation idea, I don't like any "extreme" theory that is stuffed in there to explain the incomprehensible data. So nothing can travel faster than the speed of light, oh wait it can just because we want it too?

String theory is another one I struggle with as well, although I must admit that it will lead to other things that will no doubt be revolutionary.

[AstroTiger]

I've got a real problem with the inflation idea, I don't like any "extreme" theory that is stuffed in there to explain the incomprehensible data. So nothing can travel faster than the speed of light, oh wait it can just because we want it too?

String theory is another one I struggle with as well, although I must admit that it will lead to other things that will no doubt be revolutionary.

There are many like that i find hard to reason, the other is matter is energy and energy is matter.

A nice book which helps though to answer both that and your question, why can nothing travel faster than light is explained in Brian Cox's book, why does E=MC2 (i am reading this at the moment, its an ace read)

[Astro_Baby]

Euan I agree - and I'd go further. The fact that we cant explain many things without fudging it seems to suggest we dont actually have the right answers at all and/or some data has not been taken into account.

Its why I suspect we have no 'theory of everything' in the manner of a grand unification theory. Something been left out or more likley we dont understand something as well as we thought we did.

I call this 'The Platypus' effect. Just when you think everythings been nailed down, categorised, indexed something resembling a Platypus arives and messes it all up.

So theres a fudge but no one owns up to it and so shakey theory becomes established fact from Aristotle to Newton to Einstein - fudges abound

[AstroTiger]

Euan I agree - and I'd go further. The fact that we cant explain many things without fudging it seems to suggest we dont actually have the right answers at all and/or some data has not been taken into account.

Its why I suspect we have no 'theory of everything' in the manner of a grand unification theory. Something been left out or more likley we dont understand something as well as we thought we did.

I call this 'The Platypus' effect. Just when you think everythings been nailed down, categorised, indexed something resembling a Platypus arives and messes it all up.

So theres a fudge but no one owns up to it and so shakey theory becomes established fact from Aristotle to Newton to Einstein - fudges abound

This is pretty much how science is, these constants they introduce to get something to work.

If the maths explains it, it must be true, or run with it until something better comes along.

For some reason there needs to be a mathematical proof for a theory which balances for it to be true. I guess life is totally governed by maths.

[Matthew.Blake]

I guess life is totally governed by maths.

Maths is the only language sufficient to describe the Universe.

[Astro_Baby]

Which makes it a kind of 'belief' thing. It can only be explained by clever people in white lab coats using a language most of us cant even understand. I went off and did some reading on inflation and the short answer is the universe can expand faster than light because at the moment of inflation the laws of the univesre arent in fact operative.

If thats so then we would have to believe that the universes laws as we see them are porbably a special case rather like Newtons theories on gravity.

Sometimes I wonder of the big bang theory itself is flawed and maybe Hoyle was right and its a steady state - maybe our data is faulty, maybe we dont understand something and what we imagine is evidence of a big bang is merely an illusion.

A stady state universe would be nice I think. Certainly we'd not have to worry about flawed big bang theories - we could just say it is cos it is. Which is nice

Maths is the only language sufficient to describe the Universe.

Shome mishtake - surely only poetry can describe it. Civilisations are always judged in an aftertime on their art - not their science

[Euan]

Shome mishtake - surely only poetry can describe it. Civilisations are always judged in an aftertime on their art - not their science

Maybe in the past, but you have to admit that our Scientific advancements so far have far outweighed anything achieved culturally

I was at a Modern Art exhibition today, I'm just bitter since I would rather be on a tour of CERN

[AstroTiger]

At the moment i believe in two things

Optics have come on in leaps and bounds, meaning even larger telescopes can be built

Adaptive optics are in play

Meaning, we will soon see far further into the universe than ever before, and study much more in greater detail.

one of my personal challenges is to see if we can view objects more remotely than 14 billion light years away.

If we can do that. We prove one of two things

a) We are wrong about when the universe was born

We have proven an endless universe.

I somehow believe the outcome will be B

And that is without any mathematical reasoning, just my own visualisation :-)

[Matthew.Blake]

Shome mishtake - surely only poetry can describe it. Civilisations are always judged in an aftertime on their art - not their science

Yeah, those ancient Greeks, no one remembers them for or judges them based on their science at all. The Romans too, no one gives a hoot about their road building or underfloor heating.

Anyway, who are we to judge the past? I'm sure our culture will seem as primitive in 2000 years as many people say of other ancient cultures now.

[Jim M]

Except, and this will confuse everybody not yet confused, that it takes light precisely zero time to go anywhere (according to a clock carried by the photon).

Ultimately, simultaneity itself disappears for events that happen far apart. Which events do we have here? The emission of the light OVER THERE and its detection OVER HERE. These events are connected by a "light-like interval". You can get any time value and space value you like for this separation by just going to different reference frames. There's one reference frame that is most natural/convenient to use and that is the one where OVER HERE is the origin and always has been. I guess in that reference frame you can talk about light having taken so many billion years to get here in the sense that that's what a clock staying OVER HERE for all past times would read.

If I got this wrong, it would be very embarrassing :-)

Einstein believed that nothing moved. He believed in a 4D space-time block that was frozen in which all possible instances throughout time, instances of the past the present and the future all had equal status - rather like the B hypothesis of time.

<<Einstein wrote a letter to Besso's family, saying that although Besso had preceded him in death it was of no consequence, "...for us physicists believe the separation between past, present, and future is only an illusion, although a convincing one.">>

[Jim M]

Maths is the only language sufficient to describe the Universe.

Mathematics is a tool, it doesn't describe the universe. Mathematics is the relation between descriptors. If something has property A we could find that property A changes when ( occurs and that the relation between A and B is described by mathematics. A and B are the principle qualities - physics deals with these, then mathematics is employed by the physicists to complete *our* notion of what occurs. Physics describes the universe. Mathematics is the language of physics. Anyone agree?

[Darth Takahashi]

I agree with a lot of comments here and also strongly disagree with a lot of comments here. So I'll cut straight to the point.

What we have is just one possible model of the universe that may be almost correct or completely inaccurate, only time will tell. To many people want to find one absolute truth and that may not be possible let alone practical. Science and for that matter maths are not infallible and here I do point my finger at maths. Yes you can make many beautiful mathematically consistent theories about the universe ;

1. String theory

2. M Branes

3. N Dimensional universes etc...

All of them have one fundamental flaw, they are not testable since they have set the limit for strings and extra dimension at or below 10e-33. Below the Plank length.

If a theory produces no testable results or new information / predictions then we should cast it out... "Occam Razor" applies here all to well.

I accept the speed of light as the speed limit for now since we know no better but I would dispute any and all so called simultaneous events.

So we have the age of the universe currently pegged at 14 Billion years give or take a few Billion but it will change as our knowledge grows!

Neil.

[Jim M]

I agree with a lot of comments here and also strongly disagree with a lot of comments here. So I'll cut straight to the point.

What we have is just one possible model of the universe that may be almost correct or completely inaccurate, only time will tell. To many people want to find one absolute truth and that may not be possible let alone practical. Science and for that matter maths are not infallible and here I do point my finger at maths. Yes you can make many beautiful mathematically consistent theories about the universe ;

1. String theory

2. M Branes

3. N Dimensional universes etc...

All of them have one fundamental flaw, they are not testable since they have set the limit for strings and extra dimension at or below 10e-33. Below the Plank length.

If a theory produces no testable results or new information / predictions then we should cast it out... "Occam Razor" applies here all to well.

I accept the speed of light as the speed limit for now since we know no better but I would dispute any and all so called simultaneous events.

So we have the age of the universe currently pegged at 14 Billion years give or take a few Billion but it will change as our knowledge grows!

Neil.

String Theory Experiment

Supersymmetry to the rescue?

A read recently that the LHC is not powerful enough for the above.