The Standard Model

[Martin]

Sometimes it easy for me to forget that the Standard Model is a theory that still requires proof. So tell me my brothers and sisters of science –do I understand this debate correctly?


Although the Standard Model (SM) is widely accepted as being correct -there are a number of renowned scientists, philosophers and cosmologists that disagree with the model. This is mostly due to the fact that 90% of the universe is not observable and the SM has to create unknown matter and energy to explain it. However, this is not a total fabrication because its influence on observable matter can be seen?

The SM has beautiful computer simulations that accurately show/predict the formation of our universe. However, the non believer’s view point is that anyone can create a computer simulation to show anything they want. For example, if I say that I saw a pink elephant and someone creates an image of one on a computer -does that make it anymore believable that I saw a pink elephant? Also, to suggest a simulation that you see on a computer accurately resembles the universe then you are implying that the universe has to be governed by the same laws as a computer and most would agree that this simply is not possible. And likewise observational data can fit many different theories.

So to prove the SM correct one needs to find dark matter/energy and prove its existence. I think the concept of “dark energy” derives from the fact that observations show that our universe is expanding –thus an energy source is needed to explain it – I maybe wrong? So what is dark matter? If I understand it correctly, it must have mass and it cannot be made of atoms. It has to be everywhere yet invisible –at least to our eyes and all known technology.

What do all of you think of this: http://antwrp.gsfc.nasa.gov/apod/ap060824.html
Is it a smoking gun for dark matter?

My last question is this….What awaits the person(s) who finds and proves dark matter exists? What are the rewards, consequences and implications?

And to you Harry –would dark matter’s unquestionable discovery put you and others like yourself back on the BB wagon

[astro_uk]

Hi Martin good questions.

I'll have a go at answering them. One quick pedantic point is that the "standard model" is usually used in reference to the theories of particle physics, dont ask me why but the main theories of cosmology are usually called concordance cosmology.

The unknown components of the Universe do have observable effects on the Universe as you say. The most well established of these is Dark Matter, there are many lines of evidence that all point to its existence, importantly each of these lines of evidence is fairly independent and yet they all tend to arrive at consistent results for the amount, properties and distribution of dark matter. If you want to examine where the evidence for Dark Matter comes from, you can examine things such as the rotation curves of spiral galaxies, basically spiral galaxies rotate too quickly to be held together by the visible mass we see. Another piece of evidence is from surveys of gravitational arcs around large galaxy clusters, these arcs cannot be explained by the mass that we see as luminous matter (including the tenuous Xray gas). A related piece of evidence comes from the bullet cluster work described in the link.

Dark Energy is less certain, the evidence for DE comes from examining the brightness of distance supernovae, a certain type of SN have a fixed luminosity so therefore act as standard candles, but when people started measuring distant SN they appeared to be fainter than you would expect (i.e more distant than they should be) assuming a Universe that was constantly expanding or decellarating. So something must be speeding up the accelaration of the Universe. There are several get out clauses here not least being that distant SN may well be instrinsically fainter than SN seen today (perhaps because of a lower metallicity (amount of elements heavier than He)). However models that include DE tend to fit the observed U better.

An important point about the computer models is that they are not tweaked that much, there are few free parameters. The cosmological simulations generally only model the DM (they leave out the Baryons). This is for a simple reason, DM acts (and in theory should) only by gravity, so it is much easier to simulate a DM universe then one with Baryons where all sorts of extra physics (like gas cooling due to photoexcitation) occurs. The DM does not act through the electromagnetic, weak nuclear or strong nuclear forces (or if it does it does so incredibly weakly), so it is to all intents and purposes invisible except for the influence of its gravity.

Now its not unreasonable to simulate a Universe without baryons because we think that DM makes up 90% of the mass, so wherever the DM ends up the baryons should tend to end up too. As they only interact with each other through gravity. So simulations start at a BB or shortly after, with an expansion consistent with whats observed, and perhaps a DE term that accelarates the expansion, then after 13.6 Gyr in the computer you see what distribution the DM has. You find that it matches remarkably well what is seen by galaxy surveys.

The person that proves DM exists (or possibly the person that proves something else is responsible) will get a Nobel prize no question, but of course it wont be one person but hundreds.

Hope that clears up a bit, but im sure raises many more.

[Martin]

Thanks astro.

It sounds like there may be more detective work needed than astronomy if we are to find the elusive DM.

Why the assumption that hundreds would be responsible for identifying DM?

What would you say are some of the best theories of what it is?

If you had discovered the true identity of DM what process would you follow to release such valuable information as this?

[astro_uk]

The figure of a few hundreds comes from the size of collaborations involved in this kind of research. The search for DM particles is a particle physics one, done in labs deep underground, there are several collaborations underway around the world at present.

The best throries of what DM particles could be are generally extensions of the standard model of particle physics, they involve particles called neutralinos or WIMPS (weakly interact massive particles). In both cases they very rarely react by any method other than gravity so that it is fiendishly difficult to detect them.

If anyone discovers what DM is the result would have to be confirmed by several other experiments, ideally with the same set up and another experiment that used a totally different approach. The results would then be peer reviewed and published in a top Journal, most likely Nature. Then the publicity would be huge.

[Martin]

[astro_uk]

Sorry I have no messaging, not allowed on the network.

[Martin]

[craterchains]

The standard model of many so called sciences is more often broken than not, by those that had little to do with the propagation of the standard science to begin with.

Norval

[astro_uk]

Case studies please Norval? No more fallicious statments from you without evidence. Back up your claims.

If what your saying is right I dont see how the modern world can work, if according to you we dont understand most science we must have a tough time making electronic devices, manipulating genes in dna and synthesising chemical compunds. I'm guessing apart from your computer you live and amish like existence then.

[l3p3r]

thanks again, astro_uk!
its great to read about the observable evidence to support these ideas!

[craterchains]

Sorry I have no messaging, not allowed on the network.

What a sham, give us a break with the BS will yah?
No other computers? No other access points? uh huh, sure. 8)

Norval

[astro_uk]

I do have access to other machines at home, but I generally have other more pressing comittments outside of work.

As has been pointed out though I can use the messaging on the site, which I wasnt aware of, I will be making use of this in future.

Oh and how about ..... you've guessed it....

PROVIDING SOME EVIDENCE!!!!

[craterchains]

, , , the transistor was made to work by a technician when the negative was accidentaly hooked up to the emiter side.

, , , thus by mistake we also learned that electricity flows from - to +, an exact oposite of what all the previous text books said.

Norval

[cosmo_uk]

who cares, can we not just get back to insulting your crackpot theories about a war causing all the craters in the universe. It makes me giggle

[astro_uk]

Just curious Norval, but could you link to somewhere that describes the incident your talking about, it sounds quite plausible except that presumably the valves that had been used prior to the invention of transistors would surely have not worked either.

I really dont know much about electronics though, so I'm happy to be corrected by the more knowledgeable out there.

[craterchains]

try the 1950's electronics and science magazines, I probably read it in them as a boy.

Norval

[BMAONE23]

Here is some good information about the history of the Vacuum tube
http://www.du.edu/~etuttle/electron/elect27.htm#Theory

[astro_uk]

In 1899, J. J. Thomson showed that the current was due to a stream of negatively-charged particles, electrons, that could be guided by electric and magnetic fields.

I'm still not sure, but I think this does imply people knew what was going on with electricity before the invention of the transistor. Somebody with more knowledge out there must know if this story is factual.

[AlmightyDave]

try the 1950's electronics and science magazines, I probably read it in them as a boy.

Norval

You are, again, mistaken. Lorentz published his work on the electron-collision theory of electrical conduction in 1904.

[craterchains]

try the 1950's electronics and science magazines, I probably read it in them as a boy.

Norval

You are, again, mistaken. Lorentz published his work on the electron-collision theory of electrical conduction in 1904.

How nice, how am I mistaken? Many were trying to solve those mysteries back then, some did and got canned for their ideas, which proved true later on. History has been over, and re, writen so often.

Norval

[craterchains]

BMA

That link sure brought back some memories.
Thanks

Norval

[AlmightyDave]

How nice, how am I mistaken?

You said this:

, , , the transistor was made to work by a technician when the negative was accidentaly hooked up to the emiter side.

, , , thus by mistake we also learned that electricity flows from - to +, an exact oposite of what all the previous text books said.

I replied with

You are, again, mistaken. Lorentz published his work on the electron-collision theory of electrical conduction in 1904.

You seem to have serious issues in remembering what was said between one post and the next so I'll spell it all out for you here, in one post so you can't forget what is happening half way through.

Researchers at Bell labs worked on the transistor in the late 1940's through 1950's. Lorentz published the equations that govern how electrons flow in conductors in 1904. Lorentz's model quickly became accepted by the world because it worked. The scientists (highly trained I might add) working on the transistor were well aware that electricity is carried by electrons, indeed without the fundamentals of solid state physics initiated by Lorentz's work they could not possibly have made a transistor

With that in mind, the following two sentences in your previous post are in error:

, , , the transistor was made to work by a technician when the negative was accidentaly hooked up to the emiter side.

and

, , , thus by mistake we also learned that electricity flows from - to +, an exact oposite of what all the previous text books said.

I think that about covers it.

[dcmcp]

thus by mistake we also learned that electricity flows from - to +, an exact oposite of what all the previous text books said

This is true only in materials that conduct electricity with electrons or negatively charged ions - such as metals and n-type semiconductors. In materials that conduct electricity with a postively charged carrier (ions or "holes") - such as P-type semiconductors, electricity flows from + to -.

The charge (positive or negative) of the carrier of electric current can be determined using the Hall Effect

The Hall effect refers to the potential difference (Hall voltage) on opposite sides of a thin sheet of conducting or semiconducting material in the form of a 'Hall bar' (or a van der Pauw element) through which an electric current is flowing, created by a magnetic field applied perpendicular to the Hall element. Edwin Hall discovered this effect in 1879.

It seems we knew about the "direction" of electricity in more than one material around about 1879. This was a long time before the advent of the transistor...

You are confusing the direciton of conventional current (the quantity used for scientific and engineering calculations) with the the direction of travel of the charge carrier. These are not the same thing.

+ + + + +

For the record

Edwin Herbert Hall (November 7, 1855 - November 20, 1938) was an American physicist who discovered the "Hall effect". Hall conducted thermoelectric research at Harvard and where he also wrote numerous physics textbooks and laboratory manuals.

See http://en.wikipedia.org/wiki/Edwin_Hall
This Hall fellow seems like a pretty highly trained individual to me.

+ + + + +

The standard model of many so called sciences is more often broken than not, by those that had little to do with the propagation of the standard science to begin with.

Evidence please.

[craterchains]

, , , oh well, guess I am getting too old for this stuff.

Norval

[astro_uk]

Ah the memories of Condensed Matter Physics, its all coming back now, moving "holes", n type, p type.

I remember now why I didnt like it much.