my theory of... well, STUFF!

[nickdud]

take the big circle and slide it out to the right(make it bigger) the more we find about the universe, take the smaller circle and slide it left(make it smaller) as we build better microscopes, now tell me where the cone starts and ends...............

this is not one to discuss really, more a way to visualise an idea.....

just thought i would throw it out there for you all to dream of future ......stuff;)

[Qualia]

now tell me where the cone starts and ends...............

Nice idea and thank you. Maybe the cone's lines at the small end are subtly running parallel to each other, the more we discover the more there is to find out.

[nickdud]

my idea goes along the lines of... as we learn more, small stuff gets smaller.... but where does it end? and big stuff gets bigger/further away...... so, where do we fit in? we assume we are not ants, we think we are bigger in the universe but as microscopic cells go we know nothing about our relative size....

[DH88]

The furthest we can see out is the Cosmic Microwave Backgrond. This is radiation that is from a short time after the Big Bang.

There is a limit to how far we can see because space is expanding and (I'm lead to believe) it's expanding faster than the speed of light. Thus the light from the 'edge' of the universe will never reach us if its moving faster than light can travel, so the CMB previously mentioned is the edge of the 'observable universe' .... Nowhere near the 'egde?' Of the whole universe.

On the other hand the smallest thing we can see is with an Electron Microscope and I believe to be about 0.00000001 cm

[JulianO]

The furthest we can see presently is the CMB, but in the future we may be able to see further. There are two more events beyond the CMB but our detectors are not good enough to detect them. There is the neutrino surface of last scattering - a sort of CMB in neutrinos. If our neutrino detectors we're better this would allow us to look back to about 1 second after the big bang.

There is also a gravitational last scattering surface, which occurs even earlier, but our gravity telescopes are in even worse shape than our neutrino telescopes!

The smallest things we can see are currently in the LHC - which is sort of a big microscope. There we can look inside protons and detect structure which is the quarks. This is orders of magnitude smaller than the electron microscope can see.

A fun site to play with http://scaleofuniverse.com/

[goodricke1]

There is a limit to how far we can see because space is expanding and (I'm lead to believe) it's expanding faster than the speed of light. Thus the light from the 'edge' of the universe will never reach us if its moving faster than light can travel, so the CMB previously mentioned is the edge of the 'observable universe' .... Nowhere near the 'edge?' Of the whole universe.

So when we're told the BB happened 13.7bn years ago, does this refer to the 'observable' universe or the 'real' universe? If the vast majority of the universe is beyond our perception, how do we know that the fraction we do see provides sufficient data from which to derive precise calculations?

[jeremy1]

What about on the other side of of the cone ??? Is there incredibly small anti stuff going out to incredibly large anti stuff.

[nickdud]

the CMB is," we believe ", the big bang leftovers.... but what if its just stuff,floaty STUFF?

imagine stuff everywhere. then imagine as time goes on, the stuff looks bigger(you only have to look in your shed to see stuff expand... in your mind...)

now i fully understand our BIT of the universe(our known universe) is expanding cos we think we can measure it(in which case, how come andromeda is going to hit us in many billion years? shouldn't it get further away?????) but if we think what we can see is everything, then isnt our tiny anthill a pretty self centered universe?

if we can "measure" the universe and we know where it started, are we not in the center? or are we slightly to the lower left? in which case, how come we cant see the edge?

food for thought...... and imagination.... and thanks for reading;)

[nickdud]

So when we're told the BB happened 13.7bn years ago, does this refer to the 'observable' universe or the 'real' universe? If the vast majority of the universe is beyond our perception, how do we know that the fraction we do see provides sufficient data from which to derive precise calculations?

now you get where i'm coming from....

2 words... 'observable' & 'real'

[Planetesimal]

Space is expanding everywhere, but gravity wins on the scale of galaxies, so Andromeda and the Milky Way are drawn together (because of the curvature they impart on the space-time). Incidentally the word "galaxy" comes from the same source as "milky way", i.e. ga-lactic.

The CMB is the photons from the end of the first phase of the big bang; it's not really "stuff" so much as a baseline temperature that we can measure, the leftover heat from the early universe.

As the universe is effectively infinite, there is nowhere that is the true centre.

The real universe is 13.7 bn yrs old - however the diameter of the observable universe is about 93 bn light years.

[Planetesimal]

The reason we know the universe is expanding, is that the further away from us an object is in space, the more it is "red shifted". This effect is proportional to distance wherever you look. This means that we know everywhere in space is expanding, so you can extrapolate all of space-time back to a single point called a singularity. By the way the point of the red shift is that the wavelength of light is stretched longer, because the space it has travelled through has stretched it. "Red" shift is an analogy to the fact that longer wavelengths of visible light tend towards the red and infra-red end of the spectrum.

So, the whole universe is that former singularity, i.e. every quark in every photon in your body started its life in that singularity. The big bang happened everywhere. That's why we can't say there is a centre of the universe.

[goodricke1]

The real universe is 13.7 bn yrs old - however the diameter of the observable universe is about 93 bn light years.

So the diameter of the unobservable universe is ... well, we don't know. If it is now expanding beyond the speed of light, from what point do we extrapolate backwards in order to determine its age? Maybe the magic 13.7bn figure only applies to the visible universe...

[Planetesimal]

The visible universe is about 90 bn ly in diameter. The reason it is so much bigger than the 13.7 bn year age is that it is expanding faster than the speed of light, otherwise it would just be a linear relationship and the visible universe would also be 13.7 bn ly diameter. We know the age because we can work it out from the redshift / expansion rate. It is well understood and agreed now.

[goodricke1]

The visible universe is about 90 bn ly in diameter. The reason it is so much bigger than the 13.7 bn year age is that it is expanding faster than the speed of light

No - if the visible universe was expanding faster than the speed of light it would not be visible. But thanks for the effort anyway.

[foundaplanet]

No - if the visible universe was expanding faster than the speed of light it would not be visible. But thanks for the effort anyway.

Why is that then? Does it take its light with it?

[Planetesimal]

The light is visible because its frequency is stretched to longer wavelengths by the expanded space it has travelled through.

[Planetesimal]

That is to say, although the universe is about 13.7 billion years old, due to the expansion of space humans are observing objects that were originally much closer but are now considerably farther away. The observable universe in any given direction is c. 45 bn light years.

[goodricke1]

Yes, and the expansion proceeds at less than light speed until we reach the edge of the observable universe.

[Planetesimal]

There's a difference between what scientists mean when they say "observable" universe and "visible" universe. The observable sphere is theoretical, and doesn't depend on whether technology can detect radiation from an object in this region. It just indicates that it is possible in principle for light or other signals from the object to reach an observer on Earth. In reality, we can only see light from as far back as the "recombination epoch", which was when particles were first able to emit photons that were not immediately re-absorbed by other particles. Prior to that time, the universe was filled with a plasma that was opaque to photons.

The radius of the visible universe is 45.7 bn light years, while the radius of the observable universe is 46.6 bn light years.

The explanation for all of this is called "comoving distance". Which means that we can only see things that are up to 13 bn years old (as the universe is not much older than this), but the actual distance to get to them now is much further, because space has been expanding for 13.7 bn years. So, if we're looking at something that is 13 bn years old, calculations show that it must be over 45 bn light years away, now.

[goodricke1]

The rate of expansion would appear to be accelerating however, which poses a difficulty in making those calculations because of uncertainty in the expansion rates at various epochs in the past.

[Planetesimal]

I agree, the calculations are difficult, which is why there is some uncertainty in the age of the universe. It is currently estimated at 13.75 bn years +/- 110 million years old. There are certainly assumptions in the models used to derive this esimate (these uncertainties are more about the inclusion of relativistic particles and less about the expansion rate though), and I wouldn't be surprised if it turns out the real error is +/- 1bn years, but we'll have to wait and see what the next generation of space telescopes can show us. I can't wait for the James Webb to get up there (if it ever gets built!).