Big Bang theory vs. the universe as we know it

In summary: The answer to this is usually “The Origin of The Universe”.If you understand what is being said, then you have a better conception about what is being said.What you are describing is known as the "steady-state" model of the universe, which was originally proposed in the 1940s as an alternative to the big bang theory. However, it has since been disproven by multiple lines of evidence, including the cosmic microwave background radiation. The big bang theory, on the other hand, has been supported by various observations and is currently the most widely accepted explanation for the origin of the universe.In summary, the conversation discusses the big bang theory and its implications for the creation and expansion of the universe. It addresses questions
  • #1
Low-Q
Gold Member
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I have a question you might have a good answer to.

I hear astronomers keep saying that the universe as we know it was created by a big bang. One single point that exploded.
If every known matter was flying off from the same point, how can it happen that there are stars, meteors, planets going in all different directions? Our galaxy is on collosion course on another galaxy, so these galaxies would appearently not have its origin from the same big bang. Do gravity really pull that hard between them? Or is our galaxy have its origin from a different big bang than the other galaxy?

I know about gravity, but that cannot be the only reason why these objects are not following a stright path away from the Big Bang. In the beginning there was only very small particles created, all with very little mass. How did they lump together into atoms and later small lumps of matter?

I know that the universe expands (At least what is found with delicate instruments), but with all the different directions these objects are going in the universe, the theory would not seem logical - not to me at least.

Vidar
 
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  • #2
Your mistake seems to be thinking that everything exploded from a single point. The current consensus is that the BB occurred everywhere.
 
  • #3
One single point that exploded.
That is not true. The explosion happened everywhere at the same time.
In addition, the big bang model does not include "the first moment" - it deals with the expansion and evolution of some initial, very hot and very dense universe.

how can it happen that there are stars, meteors, planets going in all different directions?
Quantum fluctuations lead to small asymmetries in the early universe, and gravity enhanced them. Those relative motions are small relative to the overall expansion and come from local gravitational and other forces.
Do gravity really pull that hard between them?
I would not call it "hard", but yes.

I know about gravity, but that cannot be the only reason why these objects are not following a stright path away from the Big Bang.
It is the main reason. Electromagnetism is there, too, and the weak and strong interaction are relevant for stars and other objects.
How did they lump together into atoms and later small lumps of matter?
Nuclei: Strong+weak force
Atoms, dust particles and so on: Electromagnetic force

If you look at the universe on a large scale, all those local movements are insignificant, and everything expands nearly uniformly.
 
  • #4
Thanks guys! Not that my survival depends on it, but I'm much wiser now - thanks :-)

Just one thing: How can the universe expand if the explosion was everywhere at the same time?

Vidar
 
  • #5
There is no problem. General Relativity is just not very intuitive.
 
  • #6
Low-Q said:
... How can the universe expand if the explosion was everywhere at the same time?

Vidar

I agree with what Mfb has been saying and want to amplify something. Are you comfortable with this idea? Namely that the universe can expand with the expansion happening everywhere at the same time. Just changing one word, in what you said.

That is, can you understand expansion as something that is experienced from within space (by distances between stuff increasing) without there being "space outside of space" for space to "expand into". I have to say that "explode" is an awful word to use, gives exactly the wrong idea of the start of expansion.

The basic assumption is there is NO SPACE OUTSIDE OF SPACE, because there is no evidence of that so it is an unnecessary complication. So when we talk about space expanding it is not in the sense of it expanding "into" some larger surrounding. The expansion we mean is that process experienced internally by distances increasing according to a definite pattern. (They currently increase about 1/140 of one percent every million years.)

In case you or anyone is curious, here is a chart that shows the past expansion history
http://ned.ipac.caltech.edu/level5/March03/Lineweaver/Figures/figure14.jpg
The heavy solid line corresponds to what we think is the case---with the model parameters set to fit observational data.
 
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  • #7
Low-Q said:
Thanks guys! Not that my survival depends on it, but I'm much wiser now - thanks :-)

Just one thing: How can the universe expand if the explosion was everywhere at the same time?

Vidar

There was no "explosion" like you are used to seeing. It was more like someone baking bread with radioactive super explosive-growth yeast. The dough went from a little ball the size of your fist to a big ball the size of your house in a millionth of a second. Except the ball may have been infinite in size both before and after. Keep in mind that the Big Bang Theory does NOT say that the universe came from a singularity, only that it was once very hot and very dense and expanded outward from there. Like baking.
 
  • #8
Low-Q Your conception of the Origin of The Universe was originally what was postulated about 50 years ago. In its original form “The Big Bang” was a finite point expansion, not a field manifestation. There were estimates of the size and the energy contend of this “point”. The conundrum was that no center could be found from which The Universe could have emerged. Of course there was always the problem of – if The Universe is expanding, what is it expanding into?

Do not let others suggest that The Origin of The Universe has been solved by postulating that the distance between points is somehow expanding - stretching. This trick is meant to resolve the need for something outside The Universe for it to expand into. As elegant as it is made to appear, there is no definitive explanation for what causes this stretching.

A good start to something better would be to define what “Space” is. At present our best is that “Space” is the distance between two points. The inference being that Space is created by necessity.
 
  • #9
Space doesn't expand. Everything just moves farther apart. You can play games with coordinates, but all you can measure is the distance between stuff like galaxies.

So, if you somehow glued every galaxy onto a grid, and you expanded the grid, then it would look like every galaxy was moving away from you, no matter which galaxy you stood on. But of course, the grid doesn't exist. Galaxies are just coasting apart via inertia, but also subject to attractive gravity and repulsive dark energy.

We don't really know what happened at the big bang, only some fractions of seconds later.
 

Related to Big Bang theory vs. the universe as we know it

1. What is the Big Bang theory?

The Big Bang theory is the prevailing scientific explanation for the origin and development of the universe. It proposes that the universe began as a singularity, an infinitely small and dense point, approximately 13.8 billion years ago. This singularity then expanded and cooled, eventually forming the vast expanse of space and time that we know today.

2. How does the Big Bang theory differ from the universe as we know it?

The Big Bang theory describes the early stages of the universe's development, while the universe as we know it refers to its current state. The Big Bang theory explains the expansion of the universe, the formation of galaxies and other structures, and the cosmic microwave background radiation. However, it does not provide explanations for all the observed phenomena in the universe, such as dark matter and dark energy.

3. Is the Big Bang theory widely accepted among scientists?

Yes, the Big Bang theory is widely accepted among scientists and is supported by a large body of evidence from various fields of study, including astronomy, physics, and cosmology. However, there are still ongoing debates and research about certain aspects of the theory, and it continues to be refined and modified over time.

4. Can the Big Bang theory be proven?

As with any scientific theory, the Big Bang theory cannot be definitively proven. However, it is supported by a significant amount of evidence and has successfully predicted and explained many observed phenomena in the universe. As new evidence is gathered, the theory may be further refined or even replaced by a more accurate explanation.

5. Are there alternative theories to the Big Bang theory?

Yes, there are alternative theories to the Big Bang, such as the Steady State theory and the Oscillating Universe theory. However, these theories have not gained as much support and evidence as the Big Bang theory and are not widely accepted in the scientific community. The Big Bang theory remains the most widely accepted and supported explanation for the origins and development of the universe.

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