Common misconceptions about the big bang

[Mr Spinkles]

The big bang comes up a lot on this forum....for some, it has religious/spiritual/theological implications. It is important, therefore, to have some accurate knowledge on this topic.

There are a lot of common misconceptions about the big bang regarding what it is, and what it is not. Don't worry though...I had these very same misconceptions not too long ago, but my astronomy course set me straight.

For starters, the big bang is NOT...

1) ...'over'. It's still happening, right now. Space is expanding as we speak, causing the distances between galaxies to increase.

2) ...an 'explosion'. Explosions happen at certain places, and for only a brief moment. The big bang, on the other hand, did not happen at any particular place....it happened/is happening everywhere.

3) ...going to slow down, turn into a 'big crunch', and cause another big bang. This theory has been thrown out due to recent studies which show that the expansion of space is accelerating. The universe will never (as far as we can tell) collapse back in on itself.

Now, here's what the big bang IS:

1) The big bang is directly observable. We can see it happening, right now. In any direction we look, we can see galaxies receeding from us.

2) The big bang is everywhere. When the universe was young, the entire, infinite volume of space was filled with high density, high energy radiation. Today, the entire, infinite volume of the universe is filled with galaxies and galaxy clusters, and as space expands the distances between these clusters increases.

3) The big bang is difficult to imagine. In order to imagine an event in X dimensions, we have to exist in X + 1 dimensions. The only way we can really grasp the expansion of three-dimensional space is to use an analogy in only two dimensions (i.e. an expanding rubber band or balloon). Still, it is important to remember that these are only analogies....they are limited in how accurately they can represent reality.

Please feel free to ask any questions you may have. I'm not an expert, but I'll answer questions the best I can. Remember, a lot is not known right now....for example, we don't know exactly what caused the big bang. There are a number of theories, but nothing is certain...still, the basic answer for why we have something instead of nothing is because 'nothing' is unstable.

 

[No*s]

Hmmm, good post Spinks.

Here's a quick question, how do you verify the "infinite space" part? Do you mean boundryless?

I know they mucked around about "dark matter," but I haven't looked into that for a while. What's its current status in the BB model?

 

[robtex]

Spinks can you explain the red shift to us please?

 

[No*s]

Spinks can you explain the red shift to us please?

I second the motion!

My understanding is that it is caused by the expansion of space...but I know I'm probably wrong. I'm not a scientist.

 

[robtex]

I second the motion!

My understanding is that it is caused by the expansion of space...but I know I'm probably wrong. I'm not a scientist.

not a scientist but obviously a punster!! that was awsome...second the motion!! :biglaugh:

 

[No*s]

Aw, thanks .

 

[Mr Spinkles]

Here's a quick question, how do you verify the "infinite space" part? Do you mean boundryless?

You make a good point, No*s: there is a difference between 'boundless' and 'infinite'. We assume that space is boundless because it seems like common sense....after all, what would happen if you reached the 'edge'? Do you run into a wall? What's beyond the wall--no space? So it is assumed that space is boundless and therefore has no center or edge.

However, you're right--that doesn't necessarily mean that space is infinite. For example, if the geometry of space were curved enough, it could curve back in on itself....meaning that space would be finite (though it would still be boundless and have no edge or center).

But space is infininte, because the geometry of space is flat. The way in which we verify that the geometry of space is flat is well, kind of complicated. I wouldn't be able to explain it without referencing my astronomy textbook, and I let a friend have it for the semester. Just so we can understand how it would be possible to determine such a thing, here's an analogy: imagine a flat piece of paper. We know the paper is flat because if we draw larger and larger circles around us, the areas of the circles always equals pi r squared. However, if the paper is curved, we'll find that the areas of the circles do not exactly equal pi r squared.

 

[Mr Spinkles]

Spinks can you explain the red shift to us please?

My understanding is that it is caused by the expansion of space

No*s is exactly right. As space expands, photons traveling through space stretch into longer (or "redder") wavelengths.

 

[No*s]

You make a good point, No*s: there is a difference between 'boundless' and 'infinite'. We assume that space is boundless because it seems like common sense....after all, what would happen if you reached the 'edge'? Do you run into a wall? What's beyond the wall--no space? So it is assumed that space is boundless and therefore has no center or edge.

However, you're right--that doesn't necessarily mean that space is infinite. For example, if the geometry of space were curved enough, it could curve back in on itself....meaning that space would be finite (though it would still be boundless and have no edge or center).

But space is infininte, because the geometry of space is flat. The way in which we verify that the geometry of space is flat is well, kind of complicated. I wouldn't be able to explain it without referencing my astronomy textbook, and I let a friend have it for the semester. Just so we can understand how it would be possible to determine such a thing, here's an analogy: imagine a flat piece of paper. We know the paper is flat because if we draw larger and larger circles around us, the areas of the circles always equals pi r squared. However, if the paper is curved, we'll find that the areas of the circles do not exactly equal pi r squared.

That's too bad. I'd be curious as to how we determine that .

Do you have any references I could read on the matter. It definately sounds like a bit more than a forum can support.

Before we go on...how certain can we be of our measurements and knowledge here. After all, we know so very little about the subject, and I can honestly see either way being true from my very limited knowledge (I'm ignorant enough that both explanations look good )

 

[No*s]

No*s is exactly right. As space expands, photons traveling through space stretch into longer (or "redder") wavelengths.

Huh. I understood it better than I thought.

Thanks for the thread and answers on it Spinks. I'll have to think up some more questions (I assume the dark matter question is too much for the thread also).

 

[Mr Spinkles]

The following is a summary of one of the chapters in the textbook Astronomy: The Solar System and Beyond by Michael A. Seeds. It explains which observations support a flat, open universe.

The geometry of space-time explains the red shift as a stretching of the photons as they travel through expanding space-time. The universe could be open if its density is less than the critical density and closed if its density is more. If its density equals the critical density, it is flat. The dark matter in the universe is important because it contributes to the density and helps determine the overall curvature. Observations of the abundance of deuterium and lithium-7 tell us that baryonic matter can make up roughly 4 percent of the critical density. Cold dark matter appears to make up less than 30 percent. The inflationary theory of the universe solves the flatness problem and the horizon problem by proposing that the universe expanded dramatically when it was a tiny fraction of a second old. Inflation predicts that the universe is flat.

Observations of type Ia supernovae reveal that the expansion of the universe is accelerating because of the cosmological constant or because of quintessence. The dark energy of empty space makes up about 73 percent of the critical density and makes the universe flat.

Observation of structure in the universe--irregularities in the cosmic microwave background radiation and the clusters of galaxies--provide strong evidence that the universe is flat and accelerating. These irregularities appear to be subatomic quantum fluctuations in space-time magnified when inflation occurred. The observations show that the age of the universe is 13.7 billion years.

 

[Mr Spinkles]

I'll have to think up some more questions (I assume the dark matter question is too much for the thread also).

Actually we did our group project on dark matter. Ask away.

 

[No*s]

OK. Thanks Spinks.

Now...I know that "dark matter" and "dark energy" are types of energy/matter that we believe exists but cannot directly observe (like a black hole). How do we guess at how much there is?

I'm a student of Christianity (not a theologian or scholar...I hardly qualify), but I find this genuinely fascinating .

 

[Mr Spinkles]

I don't have time right now to answer you in full, unfortunately, so I'll give you a brief summary:
1) We measure the rotational velocities of galaxies
2) We can use Kepler's laws to calculate how much matter there must be to supply the gravity needed to cause those rotational velocities
3) We look at how much mass we predict to be in a galaxy and realize the visible parts of galaxies cannot possibly account for all that gravity! Therefore, there must be a lot of "dark matter" in the halo of galaxies.

Here's a good link: http://map.gsfc.nasa.gov/m_uni/uni_101matter.html

also: http://www.space.com/scienceastronomy/generalscience/dark_matter_000228.html

 

[No*s]

Thanks Spinks. I'll have a looksie.

 

[linwood]

Ok..here we are again spinlkles.


About this Big Bang thing.

How is this infinately dense particle that it all started with verified?

Has anything ever been witnessed to be infinately dense?

Is there no other possibility?

I still just don`t find the theory comprehensible let alone possible.

Could you cite a source for the idea that the universe is moving to quickly to ever regress upon itself again?
This is new to me.

 

[Pah]

No*s is exactly right. As space expands, photons traveling through space stretch into longer (or "redder") wavelengths.

A Doppler effect. Stars, if the could rush towards us, would show a "blue shift" from their natural light.

 

[Pah]

Could you cite a source for the idea that the universe is moving to quickly to ever regress upon itself again?
This is new to me.

Data from the WMAP (Wilkinson microwave anisotropy probe)

 

[linwood]

Thanks Pah, I`ll have a look.

But..perhaps the Big bang itself is the common misconception I`ve always thought it was.

I just found this in the other thread....

http://64.233.161.104/search?q=cache:3qX8o0DntYoJ:www.rense.com/general61/bbang.htm+Star+red+shift+galaxy&hl=en

There goes the redshift..

What do y`all make of it?

[size=+1]You'd never know it from official news releases, but the Big Bang is broken and can't be fixed.[/size] [size=+1]A concession speech may be unlikely in 2005, but the progressive decline of one of the twentieth century's most popular theories now seems inescapable. The Big Bang has lost its theoretical foundation, which was the Doppler interpretation of redshift (linking redshift to the stretching of light wavelengths as objects move away from us).[/size]

 

[Mr Spinkles]

How is this infinately dense particle that it all started with verified?

Because the theory predicts that as the universe expanded and cooled, when the entire universe was still filled with radiation, some of that radiation was finally able to escape, and a cosmic background radiation should be bombarding Earth at certain wavelengths with very high red shifts. In 1960-something, we detected precisely that.

Has anything ever been witnessed to be infinately dense?

I'm not sure what you mean here: is there a difference between "witnessing" something and "detecting" it? We can detect black holes, and they are believed to be infinitely dense.

Is there no other possibility?

There are lots of other possibilities....but given what we know, some possibilities seem more likely than others.

I still just don`t find the theory comprehensible let alone possible.

linwood.....you're starting to sound like a Creationist. Take a telescope, and look at the sky, my friend...the evidence is bombarding us as we speak.

Could you cite a source for the idea that the universe is moving to quickly to ever regress upon itself again?
This is new to me.

We learned of two recent, independent studies which both found that the rate of the expansion of the universe is increasing. In other words, the expansion is accelerating--not decelerating, as would be expected if there was ever to be a "Big Crunch". Here's an article on the studies: http://msnbc.msn.com/id/3077857/

A Doppler effect. Stars, if the could rush towards us, would show a "blue shift" from their natural light.

Actually pah, this is another common misconception (one that I also thought was true). The Doppler Effect is not what causes the red-shifts we observe in distant galaxies; rather, the red-shifts we observe in distant galaxies is caused by the expansion of space, which stretches photons of light as they travel. With the Doppler Effect, photons of light are lengthened (or shortened) as the result of a moving object. Galaxy clusters are not moving away from each other though....the space between them is expanding.

But..perhaps the Big bang itself is the common misconception I`ve always thought it was.

linwood....the expansion of space is a fact. The existence of cosmic background radiation is a fact. If you can explain either of these facts without the use of an ancient, high density and high energy universe, please enlighten us.