Dark Matter / Energy

The way science works is that you construct the simplest possible mathematically sound model of reality that fits all verifiable observations. The lambda-cold-dark-matter (LCDM) model of cosmic expansion is such a thing - it has more or less withstood the test of all observation since 1998.

The lambda stands for Einstein's cosmological constant and represents dark energy, which could be the energy of the vacuum, in accordance with quantum mechanics. A value of 70% of the total mass-energy of the cosmos is the best-fit value.

The CDM is thought to be exotic matter, e.g., unknown particles, making up about 25% of the total cosmic energy. Ordinary dark matter, like the Earth and all sorts of cosmic gas and dust make up about 4% of the total (so you can see dark matter when you look out the window - the dirt!) This leaves about 1% for visible (intensely radiating) matter.

Now, if one does not except the LCDM model, one must come up with an alternative that also fits all verifiable observations. So far, no one that I know of has succeeded. This does not mean that the model will not change - as soon as one verifiable observation fails to match it, it will change. That's the way science progresses.

If you can live with mild mathematics, the website Relativity 4 Engineers may be of use.

You said - as soon as one verifiable observation fails to match it, it will change. That's the way science progresses.

Thats my point!

I'm not questioning the math (I can follow it enough to see it adds up); I think you've hit the nail on the head. The theory does fail to match it. So they have reinvented phlogiston.

Doesn't it?

P.S. I don't disagree with the theory, I just think it's to easy!

PlbMak, you said: " The theory does fail to match it. So they have reinvented phlogiston."

I don't understand why you say this, because the LCDM model matches all the verified observations within their respective error bars. If the "lambda" of dark energy worries you, it has been in the theory from day one - Einstein put it in, then took it out, then cosmologists put it in again, but set it to zero, because no observation required a non-zero value.

Then, as observations got better (farther and more accurate), they had to give it a value again to match observations. I recall that after 1998, when the Hubble results for distant supernovae indicated an accelerating expansion, cosmologists were reluctant to accept that at first. As more evidence surfaced, they did not change the model; they just adjusted the value of lambda to fit the data.

It is true that there is no fundamental theory that gives the value of lambda, just as there is (I think) no fundamental theory giving Newton's gravitational constant G - it is determined by experiment. The same probably holds for many constants that we use in engineering!

Right, I think I'm getting there!

What you are effectively saying is that only the name has been changed, there hasn't been a magic bullet fired into the mix to get everything to match, and that Albert had worked out the need for this Dark Energy without the observational data?

I must say I'd much rather say 'Cosmological Constant' then dark matter any day.

P.S.

Einstein? - Respect.

"If you can live with mild mathematics, the website Relativity 4 Engineers may be of use." Now there's a bit of shameless self-promotion for you! No donut. :-) --Europium

Europium, seems rather like a bit of subtle self-promotion to me! :-)

BTW, CR4 policy allows this, as long as it is helpful to members and not 'blatant commercialization', for which there is a separate section. Moderators move posts there if required. Apparently the new Blog system allows a little more freedom as well.

On a different topic, my CR4 editor box is also playing up lately, with no toolbar at the top and kicking out white spaces. I now have to enter square brackets with a p inside to get a new paragraph.

"Why have respected scientists got away with an explanation that seems to require no tangible proof? In fact, from all the research of done, the only proof appears to be the fact that it supports the current theory."

This is an incorrect statement, and there is proof - but, I don't think you understand the process. All theories require tangible proof. But you have to have a hypothesis in order to find proof for a theory.

You start with a hypothesis. If it sounds promising, others adopt it and flesh out its scientific ramifications, seeking ways to test it. Then you test it by observation and experiment. Then you find proof:

http://news.bbc.co.uk/1/hi/sci/tech/5272226.stm

More proof will follow, or not, depending on the ultimate validity of the hypothesis. Without hypotheses, there is no guidance for experimentation and observation.

Science is a process.

bhankiii, I agree with you, bar one statement: "Then you test it by observation and experiment. Then you find proof:"

"Proof" in the English language has too strong a meaning - it is better to use "agree with hypothesis or theory" or something to that effect. No amount of observation ever "proof" a hypothesis. There may always come one verified observation that disagrees with the hypothesis and falsifies it!

I'm using the dictionary definition:

Proof - evidence sufficient to establish a thing as true, or to produce belief in its truth.

For example, when Sir Arthur Eddington's observations during the solar eclipse of 1919 "proved" Einstein's hypothesis. That was sufficient to move Einstein from the "crackpot" column into the "genius" column. Additional observations added more "proof", so that the thing was finally established as "true".

Proof has both quality and quantity associated with it. But yes, there is no "absolute" observational proof of anything.

Quote: "For example, when Sir Arthur Eddington's observations during the solar eclipse of 1919 "proved" Einstein's hypothesis."

Your example is not a very good one. The inherent errors of Sir Arthur Eddington's observations of 1919 were as great as the effect he was trying to measure!

I guess he was lucky, but I still do not buy it that observations "proof hypotheses". I agree that they strengthen the believe that a hypothesis is, as Stephen Hawking said about Einstein theory of relativity, "at least very close to the truth".

But then, we are arguing about semantics, and that is perhaps not very scientific!

LOL, well - repeat his experiment then, but the point is, there is observational evidence that supports the idea of the existence of dark matter. And that's why the OP should entertain it.

Aha - now we are in agreement! Observational evidence for DM there is, so the OP should entertain it. Proof? Definitely not yet.

Maybe it would be easier if we prefaced it with "We don't exactly know for sure but..." That way there wouldn't be confusion about the state of affairs. What we think we know now sometimes changes when later we know better. That's just the way it is. We guess until we know but even when the theory and observations match perfectly there is still a possibility of yet undiscovered observations that can change what we currently think of as knowledge into discarded erroneous beliefs that were based on our prior limited ability to observe. Unless our knowledge someday becomes complete, if that is even attainable, this will always be the way it goes so we might as well accept it for the way it is, until we know better.

Just as a point of interest, we make photon detectors for the scientific community & are aware of a couple of planned & ongoing experiments specifically aimed at detecting dark matter. In time these shuold be able to prove or modify the current dark matter theories.

I still do not understand. Maybe someone has got their maths wrong. I do not subscibe to these theoretical models about the universe, as they are only hypothetical anyway! Ever since man started to wonder about our universe and all things pertaining to it we have inveriably got it wrong, think pre coppernicus or gallilao. As we have not seen further than the known universe we might be in for a surprise, remember, Africa was once called the dark continent until we penetrated it.