True size(diameter) of the universe

[derekmcd]

<font color="orange">The Local Group is moving towards the Virgo cluster. We are not moving away from those. This galaxy is moving towards Andromeda. </font><br /><br />Steve... I did mention that, just not with specifics. <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

 

[xmo1]

13.7 billion years old, geometrically flat. Check my homepage (center bottom) and Astronomy page for links. <div class="Discussion_UserSignature"> <p>DenniSys.com</p> </div>

 

[toothferry]

<font color="yellow">"so the universe is 156x billion lightyears wide, x being the rate of expansion which is called Hubbles Constant." </font><br /><br />I don't understand how the universe could be more than about 15Billion light years in diameter given that it started from a bigbang roughly 15Billion years ago. How could they figure it would be any larger?

 

[josepph]

Well. the size of the universe.. by right, it's more accurate so say that it's.. 15 billion years old. However, if you want to really try to calculate the actual*BUT not accurate* size of the universe.. you'll need to use hubbles rate of expansion.. and look at the furthest point object in the sky we can see now. Then do some math. and get 156x billion light years. lol. I really think that our universe is much larger.. maybe it's infinite. The universe is weird =/

 

[toothferry]

LOL, I guess the bigbang has a shockwave faster than c

 

[heatherjk]

The universe is nearly Isotropic (e.g. evidence provided from the CMB, cosmic microwave background). This means that no matter what direction we look in, on the grand scale, it appears the same. Regardless of this, the dimensions of the universe are not actually calculated from our estimates of it's 'age'. This 'age' that is quoted is not actually the true age of the universe, it is the time that has elapsed since the big bang, before which, we can obtain no information. Although this point is often called the singularity, it is misleading. It is a singularity such that no information can be extracted, at this time the universe was actually infinite, containing infinte mass. Another note, the universe is not static, not sure if that's what you were claiming? Hopefully this helps <img src="/images/icons/smile.gif" />

 

[newtonian]

heatherjk - Actually, the universe has some surprising structure: voids, bubbles, walls, etc. We are on a sort of river in space heading for a great attractor(s) along with thousands of other galaxies.<br /><br />The true size of our universe is unknown - especially if one lends credence to inflation theories which have the universe expanding faster than light very soon after the big bang. <br /><br />Crucial to knowing this is determining the mass and density of our universe.<br /><br />The universe is very close to omega=1, the dividing line between eternal expansion and collapse.<br /><br />This is complicated by the apparent discovery of dark energy and acceleration of expansion.<br /><br />It is evident our universe has been fine tuned to allow for life in many ways - one of which is rate of expansion which allowed stars to form and life to exist.<br /><br />Omega=1 would give a specific size to our universe as it gives density, but one needs to know the starting matter and energy values - purely energy at first, btw. - too hot for matter at the creation.

 

[heatherjk]

Newtonian -I was talking on the grand scale in regards to isotropy. If you take that assumption away than all theory as we know it to date might as well be trashed. The cosmological principal assumes that the universe is isotropic and homogeneous on large scales. Otherwise, we could not use the Friedmann-Walker metric, from which cosmological theories have been developed, for example the Friedmann equations, from which the parameters Omega[lamda, m, nu, k ] are defined. Which Omega were you talking about by the way? The sum of all omegas? and at what time?

 

[newtonian]

heatherjk - Sorry, you lost me.<br /><br />I am not that deep into the equations.<br /><br />From Wikipedia: [formatting turned omega into &#937]<br /><br />In astronomy (cosmology) &#937; refers to the density of the universe, also called the density parameter.<br /><br />In more detail, also from wikipedia:<br /><br />"The Friedmann equations relate various cosmological parameters within the context of general relativity. They were derived by Alexander Friedmann in 1922 from the Einstein field equations under some assumptions of symmetry appropriate for a cosmological model. From his equations, the Friedmann-Lemaître-Robertson-Walker metric was derived for a fluid with a given density and pressure. The equations are:<br /><br /> <br /> <br />where &#961; and p are the density and pressure of the fluid, &#923; is the cosmological constant possibly caused by vacuum energy, G is the gravitational constant, k gives the shape of the universe, and a is the scale factor. The Hubble parameter H is the rate of expansion of the universe, a value that can change over time if other parts of the equation are time dependent (in particular the energy density, vacuum energy, and curvature). Evaluating the Hubble parameter at the present time yields the Hubble constant which is the proportionality constant of Hubble's Law. Applied to a fluid with a given equation of state, the Friedmann equations yield the time evolution and geometry of the universe as a function of the fluid density.<br /><br />Some cosmologists call the second of these two equations the acceleration equation and reserve the term Friedmann equation for only the first equation.<br /><br />[edit]<br />The density parameter<br />The first of the Friedmann equations defines a density parameter useful for comparing different cosmological models:<br /><br /> <br />This term originally was used as a means to determine the geometry of the field where &#961;c is the critical density for which the geometry is flat. Assuming a

 

[heatherjk]

Newtonian- yeah I doubt Wikepedia to be the best source for this stuff, a bit outdated/subjective. They often use different notation. The Omega that you quote is indeed the density parameter, and is called Omga_M that which I was talking about before. <br /><br />Due to our present limitations, observations have only revealed Omega_M to be close to 1 with no great certainty. And in actuality it seems that, in looking at recent data, Omega_M might actually be slightly greater than 1. The problem with the argument that: Omega_M is 'close' to 1, and therefore is 1, and hence the universe is not accelerating, is: <br /><br />-If this were true, then Omega_k = 0 <br />-However, because we can only say that Omega_M is slightly larger than 1, or close to one, then we cannot say k is identically zero <br />-k tells us the geometry of the universe, open, closed and flat, the FLRW metric that all these equations come from, has this parameter in it<br />-k MUST be either 0, +ve or -ve, but we don't know how +ve or -ve it might/could be, chances are, that we could not conclude with any observables nowadays with enough certainty <br /><br />Also, to add to this, there are several models for which Omega_M ~ 1 throughout their evolution even though they are not spatially flat. The solution with Omega_M ~1, and closed universe, is not unique.<br /><br />Do you follow me? Sorry this stuff is really hard to explain without math...

 

[neutron_star69]

that too is incorrect, alot of string theorists believe that our universe lies on a membrane, and anything contained on another membrane is another universe. For example, the big bang theory, what if out universe collided with another universe. The energy from the collision would have to go somewhere so why not into our universe?

 

[alokmohan]

This a facinating reply.Can you give me link?

 

[kerazoe]

what would happen if they had a good enough ship to go to the edge or something of the universe(if possible) what would happen would their ship blow up or would there just be a loop and just go back? is the entire universe just a sphere like earth into a larger universe? lol a lot of questions basically my question is how could you ever leave the universe? is it possible.

 

[qso1]

Might be very very incorrect, even very very very incorrect LOL. But seriously, I did mention it was speculation on my part.<br /><br />Your going back to the traditional definition of Universe which I agree with. The model I suggested, that void I spoke of would be called the Universe if I were a cosmologist. But over the past twenty years or so, the definition has been modified, though not in the formal sense. The terms Multiverse, Omniverse have been used to describe the all encompassing aspect of what used to be called the Universe. Keeping in mind cosmologists talk of other Universes as well.<br /><br />There is no set definition I'm aware of now as to what constitutes a Universe. As for correctness, nobody really knows what the Universe is, how far it extends. The only difference between me and a cosmologist is that the cosmologists speculation is backed up with mathematics and a bit of observable evidence. I mention observable evidence loosly as cosmologists theorize a lot of ideas that simply cannot and probably never will be observed. They still refer to the unprovable aspects of the Universe as theoretical. And theories get updated from time to time.<br /><br />Maybe one day I'll again see a hard definition of what the Universe is thought to be. Or possibly someone can post it here and update me. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[dannyd]

mooware: If you haven't read it already you might enjoy Asimov's novella - "The Wall of Darkness." -d

 

[alokmohan]

Possiblly we have no option to define universe .That is the domain of cosmologists.Theoritically we may discuss multiverse.Till now it all imagination.White hole, warm hole are scientific thoughts,but in real terms they are matters of fiction.

 

[search]

Hubble noticed the galaxies were receding from us at a velocity proportional to their distance. The more distant the galaxy, the greater its redshift, and therefore the higher the velocity (Hubble's Law). Hubble's Law implies that the universe is uniformly expanding. What does that actually mean? For one thing, it means that no matter which galaxy we happen to be in, virtually all of the other galaxies are moving away from us (the exceptions are at the local level: gravitational attraction pulls neighboring galaxies, such as Andromeda and the Milky Way, closer together and some other mentioned above). In other words, it's not as though we here on earth are at the center of the universe and everything else is receding from us. The universe has no "edge" as such. We do however can see as far as 13,7 BLY which as some have suggested before a limitation of our own technology but maybe also a limitation of the size of the Universe itself. So back to the initial question "True size(diameter) of the universe"....?<br />

 

[search]

Just one more website with an interesting article<br /><br />http://news.bbc.co.uk/1/hi/sci/tech/3753115.stm