expanding universe...

[brazilian_and_proud]

If the universe is expanding at the moment ,if it stops expanding would it stop and go back as fast as it is expanding??????

 

[doubletruncation]

It can happen that way, in simple models where the matter density of the universe is high enough to halt the expansion it would contract in a way that is symmetric to the expansion. It's analogous to throwing a ball up in the air (ignoring friction), it comes down with the same speed that you threw it up.<br /><br />In the presently favored model of the universe it won't stop expanding, but instead the expansion will accelerate and the universe will be ripped apart. There are many competing theories though in which the universe will eventually contract. <div class="Discussion_UserSignature"> </div>

 

[derekmcd]

The total time between cycles would be the same. An example would be to throw a ball straight up... from the time you release it until it reaches it's peak will be the same amount of time as it descends from the peak until you catch it again. I would imagine the Universe would have to show signs of slowing down first, which it is not. If it were, though, the contraction would likely begin very slowly and gain speed as the mass at the "center" increased. <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>

 

[derekmcd]

Ya beat me to it <img src="/images/icons/smile.gif" /> <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>

 

[doubletruncation]

You gotta be quick <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> </div>

 

[alokmohan]

Thats one thing we cant be certain.In case of contracting universe,we have theoritical concept only.In case of big bang we have direct or scope of observation.In all fairness there are rivals of big bang theory.QUASI STEADY STATE THEOERY IS VERY MUCH THERE.Here series of big bang thories are going on .Incidentally Indian scientist J.V.Narlikar is one of the proponents of QSS theory.

 

[alokmohan]

Contractin universe is theoritical concept only.We may not be so sure.

 

[enigma10]

The really important question is is the universe really expanding, or is it simply spreading out to fill it? An expanding universe would suggest it is expanding into a medium of some form not of the universe, right? <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> <em>"<font color="#333399">An organism at war with itself is a doomed organism." - Carl Sagan</font></em> </div>

 

[alokmohan]

In steady state theory you don face all these problems.But what about 3 degree kelvin?

 

[CalliArcale]

<blockquote><font class="small">In reply to:</font><hr /><p>An expanding universe would suggest it is expanding into a medium of some form not of the universe, right?<p><hr /></p></p></blockquote><br /><br />No, and this is the part that can give some folks (like me) headaches if we think about it too hard. <img src="/images/icons/wink.gif" /> It's not that the universe is expanding into a larger space. It's that space itself is expanding. According to the theory, there is nothing at all beyond the universe, not even space, yet the universe is getting bigger.<br /><br />I find it makes sense to me mostly after I've re-read Flatland. It helps get myself into the right frame of mind (so to speak). <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[brazilian_and_proud]

well those r sumtymes the headaches that lead to great discoveries<br /><br />“People complain about headaches. I tell them all the time, when you get out of bed, it's feet first!”

 

[search]

Latest science discoveries is showing that the Universe is most probably expanding forever until it rips apart. this the achievment of Wilkinson Microwave Anisotropy Probe (WMAP):<br /><br />http://science.hq.nasa.gov/universe/science/expanding.html<br /><br />Entropy and the Universe. Several theories clearly and simply explained:<br /> <br />http://www.chiark.greenend.org.uk/~sbleas/creative/entropy/

 

[brazilian_and_proud]

a big rip actually makes more sense then the crunch theory....but chances of us knowing is slim to none.<br /><br />understanding is a three-edged sword--KOSH

 

[search]

Maybe it will not be known soon but I believe it will be someday. Here is a (not very recent but meaningfull) note from one of those who are doing something about it:<br /><br />http://www.math.toronto.edu/joel/hawking/transcript.html

 

[newtonian]

Calli - Hi!<br /><br />Yes, space is expanding, perhaps faster than light. And there is also expansion on (in) the fabric of space (during time, hence space-time) - but that appears to have a speed limit: light speed (except for possibly tachyons or perhaps some forms of dark matter).<br /><br />However, are you assuming our universe is the only universe, and that the familiar 3 dimensions plus time are the only dimensions that exist?<br /><br />Consider the following model I have independently posted on based on this statement:<br /><br />(1 Kings 8:27) . . .“But will God truly dwell upon the earth? Look! The heavens, yes, the heaven of the heavens, themselves cannot contain you; . . .<br /><br />The model derived from this is that our universe (heaven) is but one of many universes (heavens) located within a much larger heaven of the heavens (much larger universe).<br /><br />In this regard you might want to look up statements (on SDC) by astronomer Loeb - I remember he theorized our universe may already be expanding into and interacting with another universe somewhere beyond our visibility horizon (aka light cone). <br /><br />In this regard, have you considered the possibility that the newly discovered acceleration of expansion may be due, at least in part, with interaction with another universe beyond our visibility horizon, by a sort of domino effect (since light cones near our visibility horizon may include both us and mass beyond our visiblity horizon?<br /><br />Or course, there could also be forms of dark energy involved - and again, watch out that you don't assume there must be only one form of dark energy or only one form of dark matter.<br /><br />Science is replete with examples of discovered complexity after assuming simplicity.

 

[derekmcd]

<i>"The model derived from this is that our universe (heaven) is but one of many universes (heavens) located within a much larger heaven of the heavens (much larger universe). "</i><br /><br />It's turtles all the way down.<br /><br />Welcome back Newtonian <img src="/images/icons/smile.gif" /> <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>

 

[newtonian]

derekmcd - Thank you. MIssed you all!<br /><br />Turtles eh. What happenned to Atlas?

 

[derekmcd]

My point with the turtles is that if our universe is just one of many within a larger universe, then what of THAT universe... Is that the end it? Or, is THAT universe a part of something even bigger?<br /><br />When does it stop? <br /><br />Or, does it? <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>

 

[newtonian]

When does it stop? I don't know.<br /><br />We have entered beyond where scientific observation can determine the answer.<br /><br />Our Creator knows, though.<br /><br />NOte in the above verse that the heaven (singular) of the heavens (plural) is indeed singular.<br /><br />So, at least for our batch of universes, there apparently is only one larger containing universe.<br /><br />Note however, that God cannot be contained in that much larger universe. One would naturally ask: Why not?<br /><br />Before trying to scientifically speculate on that, note that the Bible does state that God resides in a heaven, likely still another universe, which his established place of dwelling.<br /><br />He created that universe so it could contain him and other energy based (=spirit) life forms. Beyond that I cannot go - I am not aware of any other Biblical clues on this.<br /><br />However, as to why the larger universe containing our and other universes cannot contain God - this may not simply mean God is larger is our 3-d plus time sense - or even larger than the 11 dimension string theory, etc.<br /><br />It may simply mean that God's form involves more dimensions than the heaven of the heavens can contain.<br />

 

[SpeedFreek]

The latest measurements indicate the universe will carry on expanding. There is evidence that the things we see furthest away from us are moving away from us the fastest. Let's think about this for a moment.<br /><br />We observe the farthest reaches of our visible universe moving away from us at colossal speeds. But the things we are observing there are the oldest things we can see. We see them how they were 13.5 billion years ago. There are various theories as to how far they have actually gone by now (known as the comoving distance).<br /><br />It is valid to think that there is more universe out there than we can see, due to the fact that we can only see things where the light from them has had time to reach us due to the age of the universe (It would be very strange if we just happened to be at the centre of a universe as old as it was big!).<br /><br />It has been postulated that any observer, anywhere in the entire universe <i> right now </i> would also see the universe stretching out in all directions 13.5 billion ly in every direction, like we do - even an observer based at the most distant objects we can see (which are <i> now </i> a lot further away from us than 13.5 billion ly). It is also postulated that any observer also sees things further away receding faster than things closer to them.<br /><br />Now here's my question. If we are looking further back in time when we look further in space and the furthest oldest stars are moving away the fastest and younger closer objects are moving away slower, doesn't this mean that the expansion is slowing down? What I mean is, if the earliest furthest stars in the universe we can see are seen to be accelerating compared to closer younger ones, this is actually seen backwards chronologically. Is the space in between objects closer to us (in time and space) is expanding at a slower rate than it was just after the earliest stars formed? <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[newtonian]

speedfreek - Good point - I am going to sleep on that one - hmmm, earlier faster expansion - reminds me of FTL inflation models.<br /><br />For now I will just say that the photons which are red shifted are shifted for the entire journey througb time and space, and, in fact, there is a lyman-alpha forest of spectral absorbtion lines which indicate progressive degrees of red shifting though time and space.<br /><br />There is an excellent Scientific American article I cited earlier on this forum - try a search under Lyman.<br /><br />I do not favor the balloon model which would be in harmony with what you are stating as there would then be no edge to our universe.<br /><br />I favor a flat model where there is an edge or outer limit for gravitationally bound, or at least influenced, matter<br /><br />That is not to say there are no stars which have achieved escape velocity from our universe - Jude 13 indicates there may be stars with no set course (probably beyond the gravity of our universe) that will be in darkness forever - hence also having escaped the light of our universe. [If the cited illustration has a literal application.]<br /><br />Either way, the balloon model or some flat model, the same effect that is observed would be predicted: closer points expanding, further points expanding out faster.<br /><br />Consider, please, this model:<br /><br />(Isaiah 40:22) . . .There is One who is dwelling above the circle of the earth, the dwellers in which are as grasshoppers, the One who is stretching out the heavens just as a fine gauze, . . .<br /><br />Consider our universe as a stretching our 3-d fine gauze - which is in harmony with observation complete with the expanding threads and filaments of our observable universe.<br /><br />In this model, closer points expand away from each other, and further points expand away faster.<br /><br />

 

[derekmcd]

<i>"Now here's my question. If we are looking further back in time when we look further in space and the furthest oldest stars are moving away the fastest and younger closer objects are moving away slower, doesn't this mean that the expansion is slowing down? What I mean is, if the earliest furthest stars in the universe we can see are seen to be accelerating compared to closer younger ones, this is actually seen backwards chronologically. Is the space in between objects closer to us (in time and space) is expanding at a slower rate than it was just after the earliest stars formed?"</i><br /><br />I understand your logic, but try not to think of time in the chronological sense. Relate it to distance, instead. <br /><br />Current thought is the red shift (as Newtonian mentioned) of light is caused by the expansion of space as light travels from distant objects thus creating longer wavelengths (red shift). The greater distance light has been traveling, the more time there has been for space to expand. Thus more distant objects have a larger red shift.<br /><br />Enter Type 1a Supernovae and acceleration. These supernovae have a fairly consitent luminosity to them in that we can judge their distance based on their observed brightness. According to Hubble's Constant, we should also be able to use redshift to judge distance. By observing a distant supernova it was noticed that it was more faint than the redshift would indicate. The conclusion was then made that the universe (fabric of space) was expanding at a slower rate when the light originally left the event. <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>

 

[SpeedFreek]

Right, I see. So if the whole of space is expanding at the same rate, the light from closer objects will be stretched less than light from further objects. So further objects have more red shift, and thus are moving away "faster".<br /><br />If this process continues, what are the implications if objects get red shifted so much we cannot see them anymore? I'm trying to get a feel for the universe of the future here. Say we are 10 billion years in the future and the expansion carries on at the same rate.<br /><br />What would we see?<br /><br />Imagine the universe is 25 billion years old. We can see the light from objects within our visible universe i.e. 23.5 billion light years in all directions. Will we actually see more of the objects in the universe than we can see now? Or will we see the same objects as now, but just further away? <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[newtonian]

speedfreek - Well, remember the red shift does not eliminate photons. It can, however, be red shifted beyond visisible light - but these photons will still be observed by telescopes sensitive to these wavelengths of light.<br /><br />As to what we will see, we do not know if our universe is interacting with another universe beyond our current visibliity horizon.<br /><br />If such an interaction is occurring, we will see it in future billions of years. If we can construct a telescope to observe faster than light sources (e.g. dark energy may propagate faster than light - in that case a dark energy telescope would allow us to see well beyond our visible light cone aka visiblity horizon.<br /><br />Remember, also, that just like an expanding gauze may have some threads and filaments break and local sections recoil, our local section does have some such cases.<br /><br />To wit, many galaxies in the supercluster of which Milky Way is a part are blue shifter rather than red shifted. <br /><br />For example, we are due to merge will Andromeda galaxy, which is blue shifted in respects to Milky Way now, and this merger should make for very interesting astronomical observations, including new stellar nurseries.<br /><br />that is roughly 5-10 billion years from now. In future trillions of years we will see other mergers as we head for what is called the Great Atrractor.<br /><br />Currently we are on a sort of river in space along with many, many other galaxies heading for this attractor(s).<br /><br />

 

[search]

The question of how the universe will look like is as difficult to answer now as the one about how the universe was. Actually even more. The reason is that although an expanding universe is getting solid ground among scientists there is still some questions regarding the ammount of matter in the universe which, depending on the answer, can change the future completely.<br /><br />One analogy can be:<br />Cooking but blind folded. We know that we have three materials to cook (hydrogen, helium and another one which we do not know but we can feel its there-dark matter). Now when we mix them out of a pot we do not know the ammounts of the mixture so when you put the cake in the oven depending on what the mixture was it will be of different aspect.<br /><br />Here is an interesting site which gives a good visual description: <br />http://map.gsfc.nasa.gov/m_mm/mr_content.html<br /><br />I have to say that I have a some concerns regarding certain aspects of the dark matter theorisation but if the data of the scientists is correct (if they are not following some correct data using the wrong formultations or laws) then when (and if) dark matter is discovered we will get a more precise answer from both the past and the future.<br />