3D Dark Matter Map

[Royston]

In a word 'awesome'...please have a look at the BBC article (link below.)

 

According to one researcher' date=' the findings provide "beautiful [i']confirmation[/i]" of standard theories to explain how structures in the Universe evolved over billions of years.

 

While previous studies of dark matter relied on simulations, this one details its large-scale distribution in 3D.

 

Professor Carlos Frenk, from the University of Durham, UK, told BBC News: "The technique they used really is the future. In the next decade, I think most studies of the Universe's large-scale structure will be dark matter structure studies. In this sense, I think galaxies will be relegated to a secondary role."

 

He added: "For the first time, we can see what's really out there."

 

http://news.bbc.co.uk/2/hi/science/nature/6235751.stm

[alan2here]

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

 

So If I get a block of wood, and paint it a verry non-shiney black, so It dosn't emmit or reflect light, then blast it with some radio waves and gama rays and they get absorbed or travel straight though it. Then It's "Dark Matter"?

[BhavinB]

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

 

So If I get a block of wood, and paint it a verry non-shiney black, so It dosn't emmit or reflect light, then blast it with some radio waves and gama rays and they get absorbed or travel straight though it. Then It's "Dark Matter"?

 

No...all known matter interacts with light in some way. The concept of refractive index is an assertion of this (ie the light is slower inside the material than in a vacuum). Dark Matter supposedly does not interact with matter in this way and thus should have RI of 1 for all frequencies; the same as vacuum.

 

A block of wood painted black can't say the same thing...lol

[[Tycho?]]

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

 

So If I get a block of wood, and paint it a verry non-shiney black, so It dosn't emmit or reflect light, then blast it with some radio waves and gama rays and they get absorbed or travel straight though it. Then It's "Dark Matter"?

 

A block of wood would interact with the EM spectrum, at the very least it would be emitting heat. So no, it would not be dark matter.

[Heretic]

One day scientists are going to look back on this and laugh.

[Royston]

One day scientists are going to look back on this and laugh.

 

Eh ? Would you mind expanding on that statement please. It's very early stages, but AFAICS this is good progress and will be used for future cosmological modeling. Why this in particular, Heretic ?

[insane_alien]

No...all known matter interacts with light in some way.

 

That isn't true, there are several known subatomic particles that don't interact with photons. neutrinos don't.

[Heretic]

Eh ? Would you mind expanding on that statement please. It's very early stages, but AFAICS this is good progress and will be used for future cosmological modeling. Why this in particular, Heretic ?

 

Just dark matter. There must be a reason for the gravitational distortions we're observing but I don't believe dark matter is the reason. I hope that this study allows us to further probe into what the cause might be.

 

Whenever I hear dark matter I always think of a really really fat woman adjusting a scale to -300 lbs before she steps on it and then saying "SEE LOOK I ONLY WEIGH 110 POUNDS!"

 

The problem is with the equation not with our ability to detect matter. Though I do believe there is matter we are not detecting, the amount of supposed dark matter is far too high to be anything more then human error.

[Norman Albers]

It is reasonable to say a material is dark WRT electromagnetic energy of such and such a frequency range. The dark energy needed for cosmic accounting has presumably no interactions of any E&M sort. Dark mass is defined by its lack of interactions of the usual massive sort: strong (also weak?) interactions, or E&M. Both are observed only by their gravitational effects in the large.

[psynapse]

I have always thought that dark matter was matter that did not give off any black body radiation, as we know conventional mass above absolute zero gives off photons so it is not dark. Perhaps dark matter is either frozen in time or is at absolute zero?

[Maximus]

You know guys, what if dark matter just does not exist?

 

For instance, the big Bang as it is known (and if correct), would be an "explosion" of such force and magnitude that it would be utterly beyond our comprehension. Especially if you consider the ever increasing size of the observable universe as seen through ever more powerful telescopes. In other words, the Big Bang would have to be an utterly staggering event to be able to create the sheer vastness and richness of the Universe that we can now see.

 

So what I wonder is this - Surely an "explosion" such as this would have a profile like any other type of explosion - a trigger event, followed by an outward accelerating exansion, followed by a deceleration until all the energy released in the event had been spent, over a measurable period of time. Thus it is possible to both model the expolsion and graph it. (I realise that I am keeping this fairly simple to illustrate my point).

 

Now my real point is this: Just suppose that the Big Bang was not over yet - that it is in fact still happening. The sheer size of the Big Bang could mean that its profile could extend over many millions or even perhaps billions of years, so we could be in a moment of time that is still on the "event curve" so to speak.

 

Depending on where we may be on the "event curve" we could be at a point in time where the final stages of the accelerating expansion are not quite over and so we see the Universe as being in a state of accelerating expansion.

 

In this scenario there is no need for dark matter or any other invisible, unmeasureable, theoretically unproven matter or forces.

 

Question: Does anyone know of any conclusive research that shows that the Big Bang event is actually finished? If so, please let me know as I would really like to get this off my mind.

 

Many thanks for listening.

 

Maximus

[Royston]

In this scenario there is no need for dark matter or any other invisible, unmeasureable, theoretically unproven matter or forces.

 

Question: Does anyone know of any conclusive research that shows that the Big Bang event is actually finished? If so, please let me know as I would really like to get this off my mind.

 

Many thanks for listening.

 

Maximus

 

Well, the big bang is just a name for the 'start' of the universe...and it was very different to how it is now. There are a number of scenarios of how the fundamental forces developed et.c but the big bang was prior to any of this, so I'd treat it as a beginning rather than a term that extends to how the universe is now.

[Maximus]

I now have two trains of thought based on your reply.

 

1. If the Big Bang was not an explosion in the real sense with no inflationary property, then I can understand your response, as indeed the atomic particles and forces would have developed after the event. And as part of that process, maybe even Dark Matter could be formed. But this does not seem probable to me, as the Universe is observed to be expanding.

 

2. Perhaps our concept of the Big Bang is too restricted in terms of its time-frame and therefore no so useful for us. When I again consider the logic behind my first posting, I still feel that we could be in the latter part of the inflationary acceleration caused by the Big Bang (if you extend the big Bang's time frame).

 

Would there be any basis for this line of thought or am I barking up the wrong tree?

 

Thanks again

 

Maximus

[Maximus]

Yes - I agree that the Big Bang is the start of the Universe so to speak. But if the Big Bang was an inflationary event, then that event would have momentum.

 

It is this momentum that I refer to in my original posting, this could be profiled and graphed. so I still wonder whether we need Dark Matter to explain why the Universe is undergoing an accelerating expansion (if I understand it correctly). This could simply be based on the original momentum of the Big Bang itself.

 

Call me simple - but it just seems such an obvious possibility to me! Though I cannot believe that scientist have not examined this before and dismissed it on the basis of some compelling evidence. (And hey - I'm NO scientist and have no real qualification in this arena.)

 

Thanks again

 

Maximus

[Norman Albers]

It seems that expansion was slowing at first, but then reversed itself. It's sort of like space itself has some inner balloon property that becomes important, in the balance, when observable densities thin out. I'm not finished studying cosmology to where I can talk specifics, because I solved my Reissner-Nordstrom problem and am trying to understand what seem like lovely results. It is teasing me: my inhomogeneous contribution in the electron field does produce specifically a 1/r term but only in the limit at the origin. The usual Schwarzschild "mass" term of the same order is still freely available as a constant of integration. This is sort of anticlimactic, but still all quite exciting.

[ecoli]

sometimes, I am completely amazed at how much we know and how we use instruments to find things out. Astro-physics has got to be one of mankind's greatest acheivements.

[Maximus]

Thanks Norman.

 

One question (coz I'm fick) - how do we know the expansin of the Universe slowed down and then started to accelerate again. (I think I got that right!)

 

Did it get a second wind?

 

Maximus

[Royston]

There's a period called the inflation period proposed by Alan Guth...negative energy pressure, and IIRC may be tied in with the advent of the strong nuclear force. I believe this happend around 10-36s after the big bang. I don't have my course book at hand, so that could be wrong. It's speculation, as are most of the early epochs of the universe...and incredibly complicated, but here's a link in case you're interested.

 

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

 

If there wasn't an accelerated inflation period, the horizon distance of the universe would be 10^50 times smaller...again IIRC, I'll come back to this when I have my books at hand, it's been a while since I've studied this area of physics.