An attempt to answer JCE's big bang question.

BGH
BGH's picture
Posts: 2772
Joined: 2006-09-28
User is offlineOffline
An attempt to answer JCE's big bang question.

jce wrote:
BGH wrote:

deludedgod wrote:
PS I hate the term Big Bang. It wasn't big, probably the smallest fundamental existence of reality compressed into a space far smaller than human imagination can comprehend, and it definitely wasnt a bang. A bang requires sound, sound requires atoms, and the primordial universe had none of those things.

I am not really keen on the terminology either, it was actually used in a derogatory manner to ridicule the theory. Basically, I like when it is descibed as a rapid expansion of space and time in all directions. No "bang" was involved.

I have a favor to ask: Would you start a thread explaining "rapid expansion of space"? This has probably already been discussed and I am sorry that I do not understand it, but I want to. I had always heard "big bang" (not necessarily in a derogative way) and have a mental image of a major explosion and there is the solar system when the smoke clears. I know this is incorrect, but I also don't know much more about it. I realize this is asking a lot of your time and possibly deludedgod's, but I, for one, would really appreciate it.

 

I did a quick search and gather some basic ideas. I wanted to give you a visualization which may help you wrap your mind around it. This image is from the WMAP site:

 

 

Time Line of the Universe

The expansion of the universe over most of its history has been relatively gradual. The notion that a rapid period "inflation" preceded the Big Bang expansion was first put forth 25 years ago. The new WMAP observations favor specific inflation scenarios over other long held ideas.

 

From NASA:

Big Bang Cosmology


The Big Bang Model is a broadly accepted theory for the origin and evolution of our universe. It postulates that 12 to 14 billion years ago, the portion of the universe we can see today was only a few millimeters across. It has since expanded from this hot dense state into the vast and much cooler cosmos we currently inhabit. We can see remnants of this hot dense matter as the now very cold cosmic microwave background radiation which still pervades the universe and is visible to microwave detectors as a uniform glow across the entire sky.

 

And an actually pretty accurate easy to understand wiki article:

http://en.wikipedia.org/wiki/Big_Bang

 


BGH
BGH's picture
Posts: 2772
Joined: 2006-09-28
User is offlineOffline
Another little blurb from

Another little blurb from PBS's website regarding Stephen Hawking's Universe:

 

 

 

The explosive beginning of our universe, the Big Bang marks the earliest time we can probe with current physical theory. Theory has to guide our understanding of the first fraction of a second, since we can’t recreate the extremely high temperatures that existed during the earliest history of the universe in any earthly laboratory. What theory tells us is that from an initial state in which matter and radiation are both in an extremely hot and dense form, the universe expands and the matter cools. At that time, it is believed that all four of the fundamental forces of nature—gravity, electromagnetism, and the strong and weak nuclear forces—were unified.

The evolution of the earliest universe is not well understood because it is not clear exactly what laws were at work. However, it is known that by the end of the first second of time, the building blocks of matter had formed. By the end of the first three minutes, helium and other light nuclei (like deuterium) had formed but for a long time, temperatures remained too high for the formation of most atoms. At around one million years following the Big Bang, nuclei and electrons were at low enough temperatures to coalesce to form atoms. But the universe didn’t start to look like it does today until small perturbations in the matter distribution were able to condense to form the stars and galaxies we know today.


JCE
Bronze Member
JCE's picture
Posts: 1219
Joined: 2007-03-20
User is offlineOffline
Whoa!!!  Thank you, thank

Whoa!!!  Thank you, thank you, thank you!!  This is amazing!  I know you all think I am goofy and should already know this stuff, but I don't and I am very grateful that you took the time to post this for me.  As usual I have some questions.  I have printed the wikipedia article and I have started reading a basic physics book so I will have more questions in the future, but here are a few to start:

  1. So this is one theory among others, right?  Is this theory the one best supported by evidence?
  2. There is an edge to the universe?  This stuns me - I had always thought there was no end; that it was infinite.  
  3. What is the rate of expansion?  (This may be in the article and if it is, just tell me it is there and I will find it.)
Again, thanks!  You are awesome!


American Atheist
American Atheist's picture
Posts: 1331
Joined: 2006-09-03
User is offlineOffline
I learned some stuff, too.

I learned some stuff, too.


Cpt_pineapple
atheist
Cpt_pineapple's picture
Posts: 5487
Joined: 2007-04-12
User is offlineOffline
jce wrote: So this is one

jce wrote:
  1. So this is one theory among others, right?  Is this theory the one best supported by evidence?

 

There are many theories of the universe.

Quote:
 

2.There is an edge to the universe?  This stuns me - I had always thought there was no end; that it was infinite.  

It is expanding. Think of it as a balloon as I inflate the balloon any given two points are now farther apart.

Quote:

3.What is the rate of expansion?  (This may be in the article and if it is, just tell me it is there and I will find it.)

 

10^50 m/s IIRC. Yes that is faster than light, but this brings forth the possibilites of the Alcubierre warp drive machine, which will drag space so we appear to be travelling faster than light.  


BGH
BGH's picture
Posts: 2772
Joined: 2006-09-28
User is offlineOffline
jce wrote: So this is one

jce wrote:
  1. So this is one theory among others, right? Is this theory the one best supported by evidence?

Yes. The current consensus of cosmologists postulate this theory to be most supported by the evidence.

jce wrote:
  1. There is an edge to the universe? This stuns me - I had always thought there was no end; that it was infinite.

I think when we were in school they were teaching the universe was infinite, but they have since revised their theories and now believe the universe to be finite. Meaning there is an "edge" to the universe.

jce wrote:
  1. What is the rate of expansion? (This may be in the article and if it is, just tell me it is there and I will find it.)

It is covered in the article but I will paste it here so you don't have to search for it.

Hubble's law expansion

Main article: Hubble's law

Observations of distant galaxies and quasars show that these objects are redshifted—the light emitted from them has been shifted to longer wavelengths. This is seen by taking a frequency spectrum of the objects and then matching the spectroscopic pattern of emission lines or absorption lines corresponding to atoms of the chemical elements interacting with the light. From this analysis, a redshift can be measured. If this is interpreted as a Doppler shift we can calculate the recessional velocity. For some galaxies, it is possible to estimate distances via the cosmic distance ladder. When the recessional velocities are plotted against these distances, a linear relationship, known as Hubble's law, is observed:

v = H_0 D \,

where

v is the recessional velocity of the galaxy or other distant object
D is the distance to the object and
H0 is Hubble's constant, measured to be (70 +2.4/-3.2) km/s/Mpc by the WMAP probe.[22]

Hubble's law has two possible explanations, one of which—that we are at the center of an explosion of galaxies—is untenable given the Copernican principle. The other explanation is that the universe is uniformly expanding everywhere. This universal expansion was considered mathematically in the context of general relativity well before Hubble made his analysis and observations, and it remains the cornerstone of the Big Bang theory as developed by Friedmann, Lemaître, Robertson and Walker.

The theory requires the relation v = HD to hold at all times, where D is the proper distance, v = dD / dt, and v, H, and D all vary as the universe expands (hence we write H0 to denote the present-day Hubble "constant&quotEye-wink. For distances much smaller than the size of the observable universe, the Hubble redshift can be thought of as the Doppler shift corresponding to the recession velocity v. However, the redshift is not a true Doppler shift, but rather the result of the expansion of the universe between the time the light was emitted and the time that it was detected.

The relation between redshift and distance is more complicated than the simple relation for velocity, for it depends on past behavior of H and thus the detailed content (matter, dark energy etc.) of the model. Also, in practice, the proper distance between two objects at a given time is not measurable, and so the redshift-distance relation also depends on the operational definition of "distance" that is chosen. By coincidence, the redshift-luminosity distance relation for ΛCDM is reasonably linear to high redshift.


Cpt_pineapple
atheist
Cpt_pineapple's picture
Posts: 5487
Joined: 2007-04-12
User is offlineOffline
Oh, BTW my 10^50 m/s was for

Oh, BTW my 10^50 m/s was for empty space.