Expanding universe question

In summary, the evidence for an expanding universe includes redshift, the Hubble relationship, light element abundances, galaxy evolution, and the cosmic microwave background (CMB). The big bang theory, which states that the universe has been expanding for 13.7 billion years, is supported by these four pillars of evidence. Obler's paradox is often cited as evidence for a finite universe, but it is not considered one of the four pillars. Other ideas, such as a bouncing universe or a universe from nothing, are currently being explored by cosmologists but have not yet been tested or proven. There is a consensus among scientists that the universe began expanding 13.7 billion years ago, and anyone who disputes this is considered a crackpot
  • #1
jim77
11
4
Another question for you all. What evidence for an expanding universe is there besides redshift. I am a layman and to me it seems like it would be simpler to find another explanation for the spectral shift of light as it passes through millions of light years of space (say some kind of lensing effect caused by warps in space (not that I know what that means) or the gravitational effects of the bodies from which it emanates or passes) than to throw common sense out the window and assert a universe out of nothing, inflation (why doesn't the gravity of the newborn universe collapse it into itself, I thought nothing could move faster than light,etc.) and all the other suppositions that separate you geniuses from we mortals. One more question along the same lines. I love those astronomy documentaries but I was troubled when I heard one scientist say that the universe was 13 billion years old and any scientist who disagreed was a "crackpot". Was this was just an unfortunate remark or does it reflect the consensus in higher physics? thanks again.
sincerely
 
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  • #2
The big bang theory which states the universe has been expanding for 13.7 bio years (according to latest measurements) relies not just on red shift but on four independent pillars of evidence.
http://physics.weber.edu/palen/Phsx1040/Lectures/LBigbang.html
If you don't know what lensing or warps in sapce mean, or you don't understand inflation, I suggest reading some introdcutory astronomy texts as well as the FAQ here in cosmology forums.
A good text is this:
http://www.amazon.com/dp/142923153X/?tag=pfamazon01-20

There is a consensus that the universe beganb expanding 13.7 bio years ago this is supported by the lines of evidence I linked to above. Yes I would agree that anyone that disputes that is considered a crackpot. However there is certainly a widely held belief that this picture is not wrong, but is incomplete and there may be a pre big bang history. This is currently being explored by cosmologists but no model is agreed upon yet because they haven't been tested. There are many interesting, creative and exciting ideas , this inlcudes a universe from nothing, but also includes many other ideas such as our unvierse bouncing from a previous one that contracted. But until some test can be devised and carried out they will not be considered facts in the same way the expansion history of the unvierse is considered a fact.
 
  • #3
Phil, I've read about the four pillars previously and one interesting thing is that different people seems to quote a different set of four - always four, but not always the same four! This is the first time that I've sen Obler's paradox included. Do you normally consider it one of the four pillars?

Regards,

Noel.
 
  • #4
Lino said:
Phil, I've read about the four pillars previously and one interesting thing is that different people seems to quote a different set of four - always four, but not always the same four! This is the first time that I've sen Obler's paradox included. Do you normally consider it one of the four pillars?

Regards,

Noel.

Actually no, good point. The standard 4 should be: the Hubble relationship, the light element abundaces, galaxy evolution and the CMB (especially the fact that its a black body).
Olbert is usually carted out to show the universe can't be infinite in both time and space and static. So perhaps its come circumstantial evidence but I don't think its one of the four. in retropsect this is better:
http://en.wikipedia.org/wiki/Big_Bang#Observational_evidence
 
  • #5
I've also not typically seen Olber's paradox included (in fact, I'm familiar with the *three* pillars, further adding to the confusion!) I don't like including Olber's paradox because as is caveated in Phil's link, there's a way around it -- a finite universe. The website goes on to state that a finite universe, however, is unsavory because we would need to be at the center of it. But this is only true if the whole of the finite universe was taken equivalent to our observable universe, and I don't know why you'd force this constraint on yourself. One can evade Olber's paradox (without accepting the big bang) by postulating a universe larger than the observable universe but still finite.

I think the pillars are best reserved for observational evidence, which I think is their intent. I've always known these to be: Hubble expansion, big bang nucleosynthesis, and the CMB.
 
  • #6
Thanks Phil & Bapowell.

Regards,

Noel.
 
  • #7
well i do think galaxy evolution is an important pillar , when we look at distant galaxies they don't look the same as nearby galaxies , this is good evidence the observable unvierse is changing.
 
  • #8
Actually now I think of it,suppose you did have an infinite past and infnite space, the light from the infinite past can't go through the last scattering surface so wouldn't this be a way round Olbert's paradox?
 
  • #9
I think that the usual 4th pillar relates to the cosmic principle (generally isotrophic and homogenius) which, though not strictly observational, is extremely important.

(Phil, good point on Obler's paradox, I like it.)Regards,Noel.
 
  • #10
Lino said:
I think that the usual 4th pillar relates to the cosmic principle (generally isotrophic and homogenius) which, though not strictly observational, is extremely important.
Except that a static universe could be isotropic and homogeneous, no?
 
  • #11
bapowell said:
Except that a static universe could be isotropic and homogeneous, no?

Mmmm ... I suppose so! I've never really thought about it from that perspective.

When you say static, how "static" are you talking about? (Evolution but no BB so just the age is different, or existed forever but no change except for those associated with collisions, or something else?)

Regards,

Noel.
 
  • #12
I just mean that the observation of a homogeneous and isotropic universe does not in itself imply that the universe is expanding (or that there was a big bang).
 
  • #13
skydivephil said:
well i do think galaxy evolution is an important pillar , when we look at distant galaxies they don't look the same as nearby galaxies , this is good evidence the observable unvierse is changing.
This implies that galaxies are evolving and that the speed of light is finite, but does it necessary imply that the universe is expanding or itself evolving from an initial high density state?
 
  • #14
But isn't that the point about the pillars? If you take anyone in isolation, it does not imply that there was a big Bang / the universe is expanding, but when taken together, the weight of evidence strongly suggests / implies that there was a big Bang / the universe is expanding.

(My understanding is that: Hubble expansion observations can be caused in other ways, big bang nucleosynthesis has large potential "error bars" (my clumsy words - I'm not sure how to say it explains some but not all of the related element abundances), and the CMB ... I still reading about and trying to understand this so I'm open minded about it at the moment.)

Again, and only my understanding, taken as a sum total, it strongly suggests / implies that there was a big Bang / the universe is expanding.

Regards,

Noel.
 
  • #15
Lino said:
I think that the usual 4th pillar relates to the cosmic principle (generally isotrophic and homogenius) which, though not strictly observational, is extremely important.

Recently, there has been a lot of work on the observation status of this. See some of the entries in this arXiv search:

http://arxiv.org/find/gr-qc/1/au:+clarkson/0/1/0/all/0/1
 
  • #16
Thanks George. Appreciated.

Regards,

Noel.
 
  • #17
Lino said:
But isn't that the point about the pillars? If you take anyone in isolation, it does not imply that there was a big Bang / the universe is expanding, but when taken together, the weight of evidence strongly suggests / implies that there was a big Bang / the universe is expanding.
Maybe that's a fine interpretation. It's just that the observation of a homogeneous and isotropic universe has nothing to do with expansion. If you add it to the other three, it does not strengthen the argument for a big bang.
 
  • #18
skydivephil said:
The big bang theory which states the universe has been expanding for 13.7 bio years (according to latest measurements) relies not just on red shift but on four independent pillars of evidence.
http://physics.weber.edu/palen/Phsx1040/Lectures/LBigbang.html
If you don't know what lensing or warps in sapce mean, or you don't understand inflation, I suggest reading some introdcutory astronomy texts as well as the FAQ here in cosmology forums.
A good text is this:
http://www.amazon.com/dp/142923153X/?tag=pfamazon01-20

There is a consensus that the universe beganb expanding 13.7 bio years ago this is supported by the lines of evidence I linked to above. Yes I would agree that anyone that disputes that is considered a crackpot. However there is certainly a widely held belief that this picture is not wrong, but is incomplete and there may be a pre big bang history. This is currently being explored by cosmologists but no model is agreed upon yet because they haven't been tested. There are many interesting, creative and exciting ideas , this inlcudes a universe from nothing, but also includes many other ideas such as our unvierse bouncing from a previous one that contracted. But until some test can be devised and carried out they will not be considered facts in the same way the expansion history of the unvierse is considered a fact.

This is what I don't get. Brilliant scientists like Fred Hoyle and Halton Arp posit alternative theories and are labelled crackpots for their efforts. I can't understand the details (I have read a lot of introductory astronomy texts but without the the advanced math they read like a dungeon and dragons text on wizardry (just accept that this is so! Not criticising I just don't have the faculties to judge the merits of what I'm reading)) so I can only judge by my gut (Colbert will back me up on this) and these guys seem like honest scholars who look at the same evidence and come to different conclusions. You guys know better than me so I'll defer to you but is everything really so wrapped up?
sincerely
 
  • #19
bapowell said:
Maybe that's a fine interpretation. It's just that the observation of a homogeneous and isotropic universe has nothing to do with expansion. If you add it to the other three, it does not strengthen the argument for a big bang.

Thanks Bapowel. Understood.

Regards,

Noel.
 
  • #20
jim77 said:
Brilliant scientists like Fred Hoyle and Halton Arp posit alternative theories and are labelled crackpots for their efforts.


Well, these scientists are dethroned after scientists who takes into the consideration of the possibility they're right or willing to test it have shown that they're wrong. However, let me say this to you. Scientists who tries to find alternatives ideas being labeled as crackpots is nothing new as shown in history and a lot of time, the mainstream scientists in history fails to take into consideration that questioning and looking for new ways to look at our universe helps us develops more of our understanding. There is nothing wrong with questioning at all and in fact, questioning does help advancement rather than sticking to the same ol ideas a lot of time. Honestly, I appreciate that you can appreciate scientists who tries to look into alternative ideas.
 
  • #21
jim77 said:
This is what I don't get. Brilliant scientists like Fred Hoyle and Halton Arp posit alternative theories and are labelled crackpots for their efforts. I can't understand the details (I have read a lot of introductory astronomy texts but without the the advanced math they read like a dungeon and dragons text on wizardry (just accept that this is so! Not criticising I just don't have the faculties to judge the merits of what I'm reading)) so I can only judge by my gut (Colbert will back me up on this) and these guys seem like honest scholars who look at the same evidence and come to different conclusions. You guys know better than me so I'll defer to you but is everything really so wrapped up?
sincerely
Hoyle was an honest scientist -- that's not the problem. The problem is that observations show his theory to be wrong. The discovery of the CMB in the 1964 essentially slammed the door on the steady state model. I'm not familiar enough with Arp to say much about him. However, it does happen sometimes that competent, honest scientists stubbornly stick to pet theories and rationalize away observational evidence that disagrees with them.

That said, current data overwhelming points to an (observable) universe with a finite age that is expanding from an earlier hot, dense phase. This is the big bang model.
 
  • #22
Arp attempted to hand wave away redshift as a distance indicators by cherry picking galaxies that appeared to be interacting, despite impossible discrepancies in their redshift. His examples of discordant redshift have been steadily eroded by better observations. His idea that quasars are ejected from mature galaxies has been relegated to the dust bin of failed theories.
 
  • #23
What is the universe expanding into? If I blow up a balloon, it will expand into the room and crash into the 4 walls, ceiling, and the floor. Thus, if the universe is a sphere, is it expanding into a sphere, or into some other geometric space/object that it will eventually crash into or hit?
Will this crash stop the expansion?

Or, is the universe creating space for itself to expand into where there was none before the BB?
If there was nothing before the BB, then where did the material or the matter of the BB come from? Some say, a previous universe collapsed into a size 1/10m cm. Others claim there are many universes; and ifcourse some say this is the 1st and only one ever.
 
  • #24
Gomar said:
What is the universe expanding into?
Nothing. Have a look at the FAQ -- I believe this issue is addressed.
 

1. What is the expanding universe theory?

The expanding universe theory is a scientific explanation for the observed phenomenon that the universe is constantly expanding. This theory suggests that the universe started as a singularity and has been expanding ever since, carrying galaxies and other matter with it.

2. How do we know that the universe is expanding?

Scientists have observed that the light from distant galaxies is redshifted, which means that the wavelengths of the light appear longer than they actually are. This is a result of the galaxies moving away from each other, indicating that the universe is constantly expanding.

3. What is driving the expansion of the universe?

The exact cause of the expansion of the universe is still a topic of debate among scientists. Some theories suggest that it is due to the force of dark energy, while others propose that it is a result of the Big Bang and the initial expansion of the singularity.

4. Will the universe continue to expand forever?

Based on current scientific understanding, it is believed that the expansion of the universe will continue indefinitely. However, the rate of expansion may change over time depending on the amount of dark energy present in the universe.

5. How does the expanding universe theory relate to the concept of the Big Bang?

The expanding universe theory is closely tied to the Big Bang theory. The Big Bang is believed to have been the initial event that started the expansion of the universe, and the ongoing expansion is seen as evidence supporting the Big Bang theory.

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