Is the big bang an accurate name for the beggining of the universe?

[Struders]

I've been pondering again!

The big bang... what was it? what I'm getting at is, was the universe started in a single point or did it come to be in all places at the same time?

The reason I ask this question is because in my mind if all the "stuff" in the universe was in the same point in space, or even near to being in the same place why didn't it collapse in on its self as a blackhole?

My understanding of blackholes are that they are very heavy things that collapse on their own gravity, and that no amount of energy can escape the event horizon once it has passed.

[brianb]

was the universe started in a single point or did it come to be in all places at the same time?

Both - at any rate in the four dimensional space-time that defines the modern universe at scales larger than the Planck length.

why didn't it collapse in on its self as a blackhole?

An excellent question ... I think you need to look for the answer in at least some of the "hidden" dimensions demanded by string theory ... when you find it you may well be able to answer the inflation paradox too.

[stolenfeather]

I don't believe that "Big Bang" is the right terminology for it either. If I fully understand it, the universe simply started to expand and no explosion was involved,

Isabelle

[Doc]

Think of it as "The big Expansion"

[stolenfeather]

Yeah,. I agree with Mick here, The BIB EXPANSION it is!

Isabelle

[MarySkater]

The term "Big Bang" was coined by Fred Hoyle who didn't believe in it anyway. So the name was meant in a derogatory way, not as an accurate description.

Mary

[stolenfeather]

That's interesting Mary. I didn't know that!

Isabelle

[brianb]

The term "Big Bang" was coined by Fred Hoyle who didn't believe in it anyway. So the name was meant in a derogatory way, not as an accurate description.

I'm not at all sure Fred would have intended it to be derogatory. "Steady state" isn't an exact description of the way that Fred thought the universe worked, anyway.

"Bang" doesn't make sense without sound, and ears to hear it.

[themos]

Forget about the "big bang" as a concept. What the model says is that there is an "exchange rate" between space and time and looking at remote galaxies shows that this exchange rate varies along the time coordinate, making past space displacements worth more than current ones. So, a light year today doesn't even get you to the nearest star but a light year at some moment in the past could get you to the nearest galaxy.

[ollypenrice]

I think Hoyle's coining of the phrase was slightly satirical if not derogatory in an unkind way. I believe he used it first on a BBC radio programme he presented.

Olly

[brianb]

I think Hoyle's coining of the phrase was slightly satirical

Yes ... but there is a halfway house between what for the sake of simplicity I'm going to call the Big Bang and Steady State models: lots of "little bangs" occurring at such a rate as to keep the average density of the universe near constant as expansion continues. We now know that this model isn't viable but the knowledge was not available when Hoyle coined the phrase. How? Well there would be a whole spectrum of "black body" cosmic background radiations, not just the one: nevertheless the "many little bangs" model has proved just as accurate as Hoyle's vision of steady state, where matter comes into being everywhere, at a rate just high enough to balance the expansion.

The major issue with the "big bang" is indeed the name rather than the model. However common language is completely lacking in the words to describe an event happening simultaneously everywhere, or expansion without boundaries. Only mathematics works as a description. So long as you treat the phrase "big bang" as a shortcut for an idea, and get out of your head those fancy computer graphics which clearly show an event occuriing at one point and expansion into the initially blank corners of the screen, it works just fine.

[themos]

However common language is completely lacking in the words to describe an event happening simultaneously everywhere, or expansion without boundaries.

No, it is not lacking. We are all comfortable with "inflation", it erodes the value of money everywhere, simultaneously.

[ollypenrice]

No, it is not lacking. We are all comfortable with "inflation", it erodes the value of money everywhere, simultaneously.

... very good analogy since there is no centre or geographical spread of contagion! But don't cosmologists usually just mean Alan Guth's bit when they talk of inflation?

Olly

[martin_h]

What annoys me is that when presented on TV they talk about an expansion then go on to show a huge fireball explosion!

[AlexB]

The reason I ask this question is because in my mind if all the "stuff" in the universe was in the same point in space, or even near to being in the same place why didn't it collapse in on its self as a blackhole?

Because the suppositions about the 'big bang' start of the universe as we know it event, matter didn't exist, there was just a random burst of energy which expanded very very quickly, faster than the speed of light.

Matter came some time after the big bang, but due to the speed of expansion, none of that matter could actually accelerate toward (or fall toward depending on your viewpoint) each other.

As I understand it, there has been some break-even along the timeline where matter could start moving toward itself versus the expansion of the universe.

The other side of this is that almost half of the matter in the universe at that time was anti-matter. So anything that attracted to other matter was most likely going to hit upon anti-matter and be converted back into pure energy again. We're the left overs apparently.

They do say that there was an imbalance in matter vs anti-matter numbers, which is why we exist today, however, I feel that perhaps all of the left over matter still has matching anti-matter, it's just that they haven't collided (yet/won't ever?)

I'm not an expert though, this is just what I've read/watched/listened to.

[themos]

But don't cosmologists usually just mean Alan Guth's bit when they talk of inflation?

They do and it was quite a bad choice of label. In popularising the subject, we can talk of "runaway inflation" to describe Guth's scenario.

[brianb]

They do say that there was an imbalance in matter vs anti-matter numbers, which is why we exist today, however, I feel that perhaps all of the left over matter still has matching anti-matter, it's just that they haven't collided (yet/won't ever?)

Well, the stuff isn't anywhere around here (not even down the back of the sofa ) if it was there'd be "fireworks" in the sky at even intergalactic densities!

It's perfectly true that there is no thoroughly accepted theory that explains the imbalance of matter vs. antimatter but it is also true that, if the universe began as a quantum fluctuation, the fluctuation would have had a sign and that could express itself as an imbalance in the matter / antimatter ratio. It's also hard to explain why supermassive black holes appear to have been formed in the immediate aftermath of Big Bang but not less massive ones ... according to accepted theory, the universe ought to be well populated with black holes of all sorts of masses, the very lightest would have decayed by now but the asteroidal mass ones would still exist & we ought to see them evaporating away as very short lived flashes of energy (slowish rise, very rapid fall) but apparently no such events are observed. There don't seem to be any magnetic monopoles around either (fortunately) ... Guthrie's inflation theory is elegant in many ways, and does help explain the "missing" monopoles, but doesn't really help with the other anomolies.

Fact of the matter is, we don't know everything, yet.

[Struders]

Okay so the model of the universe that is now in my head is;

The big bang is a bit of a inaccurate description, but a sufficient pointer to the "moment" when the universe rapidly expanded at every point along dimensions "x/y/z/time"(<- thinking aloud is that spacetime?) (thinking aloud again, it expanded because it was hot? and the only way to cool would be to expand?)

(note I have spent the last 40mins writing and rewriting the above paragraph!!)

[themos]

It's better to think backwards (as we are more confident about physical theories in a universe that is like it is now than the very beginning) and consider the "exchange rate" between space and time as changing. That can be visualised as the "rate of time passing" changing or space "contracting" as you go back in time. Maybe this is of no help at all...

[AlexB]

Well, the stuff isn't anywhere around here (not even down the back of the sofa ) if it was there'd be "fireworks" in the sky at even intergalactic densities!

Unfortunately I don't know the ins and outs of anti-matter and it's physical properties to say enough on this. Things like:

- Does it have gravitational attraction to normal matter

- If it does not attract and in fact repels is this what causes Dark Energy? (Probably not though.)

- Can it be detected like normal matter

- If not, could it be possible that our current detection techniques are not strong enough to detect it in the universe

- If we can't detect it easily, is this what Dark Matter actually is? (I'm pretty sure not as apparently it surrounds our galaxy)

I think it's highly conceivable that there could be vast aMatter clouds in pockets of intergalactic space which just managed to escape all the other matter. Certainly more likely at the fringes of the universe I would have thought. I'm just guessing mind.

[themos]

Yes, it gravitates like normal matter.

No, "dark energy" requires radically different behaviour.

It can be detected like normal matter.

"Dark Matter" needs to be electrically neutral (otherwise it would emit light and it wouldn't be dark anymore). It could be its own anti-matter or not.

There could be a lot of anti-dark-matter but not a lot of anti-bright-matter because we would see the flashes of light that anti-bright-matter would emit when it came across some bright-matter.

[AlexB]

Thanks themos, just been reading the wiki page on it...

Antimatter may exist in relatively large amounts in far away galaxies due to cosmic inflation in the primordial time of the universe. Antimatter galaxies, if they exist, will have the same chemistry and spectrometry as normal matter galaxies and their astronomical objects would be observationally identical, making them difficult to distinguish.[10] NASA is trying to determine if such galaxies exist by looking for X-ray and gamma-ray signatures of annihilation events in colliding superclusters.[11]

[AlexB]

I'm just thinking about this some more, when an electron changes energy level it gives off a Photon, when a positron changes state, does it give off an Anti-photon?

[brianb]

when an electron changes energy level it gives off a Photon, when a positron changes state, does it give off an Anti-photon?

Yes but a photon - having no charge & no spin - is its own anti-particle.

[AlexB]

Yes but a photon - having no charge & no spin - is its own anti-particle.

Has anyone ever measured this I wonder? I was doing a little bit of digging around and there's no mention (in my quick search) of Photon release of a positron state change.

I think maybe the assumption is 'energy' is 'energy' but then... we have 'dark energy.' I suppose if positron has been composed of normal energy that stands to reason.

I wonder if dark energy is basically... anti-energy and thus dark matter may be the matter constructed from anti-energy (and thus true anti-matter as opposed to -ve polarised matter (or +ve depending upon viewpoint.)

I'm itching to take up physics again, can you tell. lol