I found this quite interesting:

http://www.physicsweb.org/articles/news/9/6/10/1

Basically, the standard model predicts a neutrino background along with the microwave background. It's something like 150 neutrinos per cubic centimeter.
How do alternate theories deal with that!?

__________________

Feynman
>~~~~<
Science is a way of trying not to fool yourself. The first principle is that you must not fool yourself, and you are the easiest person to fool.

Religion is a culture of faith; science is a culture of doubt.

Neutrinos seem to be something that we don't understand much about, at least in terms of experimentally verified understanding. What is the current state of the missing solar neutrinos? Is that still unanswered?

__________________
Time flies like an arrow.
Fruit flies like a banana.

Just out of curiosity, who made that prediction? Do you give me a source?

__________________
As above, so below

Neutrino change 'flavors.' There's your normal Electron Neutrino, the Muon Neutrino and the Tau Neutrino. We were looking for Electron Neutrinos and only saw 1/3 of the predicted ammount. Hmmm. 3 types of neutrinos... only 1/3...
Come to find out, neutrinos change 'flavors' on their way from the sun.

Any way, I still think it's neat that there's a neutrino background. 8)

__________________

Feynman
>~~~~<
Science is a way of trying not to fool yourself. The first principle is that you must not fool yourself, and you are the easiest person to fool.

Religion is a culture of faith; science is a culture of doubt.

__________________

Feynman
>~~~~<
Science is a way of trying not to fool yourself. The first principle is that you must not fool yourself, and you are the easiest person to fool.

Religion is a culture of faith; science is a culture of doubt.

With a picture:

Neutrino Evidence Confirms Big Bang Predictions

__________________
Everything I need to know I learned through Googling.

Detectors to detect all three types of neutrino found that the solar neutrinos are indeed changing flavor. Measurements gave the ratio of the different neutrino masses and a fair window around the actual masses. This was Big News, since it finally settled the issue of whether neutrinos have mass.

I have a question (if it's possible to explain on a layman level)

I keep hearing that neutrinos and cosmic background radiation are signs of the BB, and theories are made based the measurement and distribution of this "stuff". What I have a hard time understanding is that we are an expanding universe, and (at least for neutrinos) this stuff is particles. Wouldn't the neutrinos that existed from the BB be moving away from us as is the rest of the universe? (In my mind we would only be seeing neutrinos that originated from somewhere else, or have had their trajectory altered in some way) How can we tell the difference between the "Original" neutrinos and ones that may have been generated from some sort of cosmic event?

Any idea where we might find a little more information about exactly what they're doing? My understanding was that the cosmic neutrino background was at way too low an energy to be detected a this point (we can only detect relatively high energy neutrinos), and this

would seem to confirm that. So how exactly was that map put together?

I'll try to answer this. First, remember that the "moving away" is a general trend, and that particles all have their own individual motions, too. For either the microwave or neutrino background, you can think of the universe as a gas of photons or neutrinos that is steadily expanding, so there are always going to be some passing by at any given moment, they just get scarcer with time.*

As for recognizing the difference between, say, CMB photons and any other photons, we usually do that by looking at the spectrum. That is, photons from the CMB have a specific energy distribution, whereas photons from another source would have a distribution. It's a moderately complex analysis process, but it's definitely possible to look at the observed spectrum and recognize multiple sources, or subtract out certain sources to see what remains.


* If it helps, you might also think of the ones we see now as the ones that just happened to be emitted at the right spot and be moving with the right peculiar velocity to exactly compensate for the expansion of the universe between when they were emitted and now. It might seem a big coincidence that the starting position and velocity would be just right, but it's really just that there are so many particles with a range of all possible velocities, and they were emitted all throughout the universe, so all bets are covered.

First; Thanks for a quick concise explaination.

I think I understand, but a re-wording helps. Let me try, and tell me if I'm close.
This means we are determining the background ones by comparing the observed results with the expected deviation from random or known sources?

The photon explaination makes sense to me

The science paper appeared on astro-ph last year.

Neo, also remember that these photons/neutrinos are everywhere. 400,000,000 CMB Photons are passing through my eyes every second, from every concieveable direction.
I'm not sure about the neutrinos, but the photons come from the surface of last scattering, when atoms first formed. Before that time, the average energy of the universe was so high that electrons and neucli were whizzing around too fast to make atoms, so any photons created from the big bang (or any other process for that matter) would be glancing off of electrons, neucli, etc...
In other words, the universe was opaque because it was "on fire". After it cooled, electrons got 'captured' by the neucli, making atoms, and photons found a transparent universe.
It is neat to imagine that phase transition and think of the isolated pockets of atoms forming, spreading across the entire universe as it cooled.
Let there be light, indeed. 8)

[edited to remove confusion... for me... ]

__________________

Feynman
>~~~~<
Science is a way of trying not to fool yourself. The first principle is that you must not fool yourself, and you are the easiest person to fool.

Religion is a culture of faith; science is a culture of doubt.

Thanks again;
Just for your info, I am a person who understands mostly by visualizing. (words fail me alot) So different explainations help. I also tend to try to see the big picture, then fill in the details as time goes by.
I just love science, but not the tchnobabble.

Exactly what I was looking for, thanks. They seem to be looking at the effect neutrino anisotropy would have on the CMB, and then extrapolating back from the observed CMB data. Fairly speculative, I suppose, but a creative technique for detecting something that would otherwise be unobservable.

The neutrinos are in essentially the same situation. At sufficiently high energy, neutrinos actually interacted sufficiently frequently with other matter (generally through transforming protons to neutrons or vice versa) that the universe was essentially opaque to neutrinos. Once the available energy was too low for that interaction, the neutrinos could travel freely.

Note that the energy in this case is much higher, and that the time of last scattering for neutrinos corresponds to the same time as original nucleosynthesis, minutes after the Big Bang. If we can someday detect those neutrinos directly, we'd have a direct view of a much earlier time than the cosmic microwave background gives us.

Is this a joke?

We know the sun kicks out something we choose to call neutrinos - we don't know for sure, because all neutrino detection is secondary -

So we should assume all off the galactic structure between here and hell boiling over will also be kicking out the same emissions. We do not know the depth of the universe - we have no indications from either the deep radio, X-ray, or visible light spectrum where, if anywhere - structure of the universe tails off.

Unlike CMB radiation, which can at least be modeled as having a power function, there is no way that I can see to separate neutrinos emitted from galactic structure from 'big bang' neutrinos. So neutrino ripples in the CMB? Its like going down to the public water works and trying to segregate the campus urine from the general population.

Pick a number.

Edited to add: Oh, I thought this was an ATM thread...I usually try to be slightly more diplomatic on the mainstream side 8-[

__________________
jwj

It's a big universe out there...is it really unwinding, really burning out?

As Grey pointed out, I think one needs to understand how these neutrinos are being detected (if indeed they really are) before one vilifies it.

By the same token, we shouldn't anoint the finding as being another brick in the BB wall either.

They are extrapolating these neutrinos from the CMB. It isn't a direct detection, but it's a prediction. I can't wait till we send up a scope of some kind to get us a 'picture' of the neutrino background. Then, if it matches the broad characteristics of the modeled neutrino background, tally one more for the standard model. 8)
No Jerry, it wasn't a joke. I was just seeing how the ATM side of things would deal with this when it gets found. Neutrinos at 2K? From stars? Nope. Try again.

__________________

Feynman
>~~~~<
Science is a way of trying not to fool yourself. The first principle is that you must not fool yourself, and you are the easiest person to fool.

Religion is a culture of faith; science is a culture of doubt.

Well, they behave like neutrinos are expected to behave, so it would seem reasonable to assume that they are in fact neutrinos. Unless you're proposing that they are instead some new unknown type of particle. If you have a problem with the detection method, I assume you also have problems with the rest of particle physics, and the things we choose to call protons, neutrons, and so forth. :wink:

Indeed, that would be a reasonable assumption.

We'd do it the same way that we differentiate between the x-ray photons emitted by hot gas, visible photons emitted by stars, and all the other kinds of photons we see. The energy of the particles in question (whether photons or neutrinos) is vastly different for different sources.

Now, that said, I'll reiterate that we cannot actually detect such low energy neutrinos at this point, and this paper isn't claiming that we can. Rather, since such a neutrino background is a prediction of a big bang, the authors made an effort to determine whether there might be an observable effect (specifically, in the microwave background that we can observe), and then look to see if it's there. It looks as though the results are at least consistent, though I'd agree with pghnative that this shouldn't be taken as a pillar of the big bang or anything, since there might be other possibilities consistent with the results, too. Still, I'm impressed at the ingenuity of the authors.

Simply test for that portion which has a much greater ratio of alcohol and amphetimines; which of course are coincidentally the progenators of such wild neutrino/BB speculations. :P

G^2

Cosmic Microwave Background results did NOT match prior predictions, which were quickly revised when the Boomarang data came in, just in time for WMAP. But that did not prevent the PIs from declaring another victory for the standard model, and it is not hard to find cheerleaders who will tell you the measurements perfectly matched the predictions all the time.

Something is wrong.

__________________
jwj

It's a big universe out there...is it really unwinding, really burning out?

Please people...post ATM arguments on the ATM forum...

__________________
"The facts gentlemen, and nothing but the facts, for careful eyes are narrowly watching." Isaac Asimov

I think we can all agree on that. :-?

The way you would distinguish an original neutrino from one created 8 minutes ago in the sun is that the old ones have vastly less energy. They've been traveling billions of years across space that's expanding and therefore reducing their energy. It's tough enough to detect solar neutrnos. The sun makes 2.4e+36 (2.4 million million million million million million) neutrinos every second, one per proton joining with an electron to become a neutron, of which a half billionth pass through Earth. That's 60 billion passing through every square centimeter of your body every second, and yet monster huge netrino detectors with hundreds of thousands of gallons of liquid only see twenty or so neutrinos or so a week.

We'll probably never ever see a low energy one from the beginning of creation because the lower the energy of the neutrino, the harder it is to see. We're pretty sure they exist, but we're also unable to come up with any experiment that can find them. So far. And probably we'll remain unable to do so in any forseeable technology.

__________________
http://members.elirion.net/~maddad
There are 10 kinds of people. Those who understand binary, and those who do not.

There are two misconceptions floating in this thread.

First, the BB was not in any sense an explosion-- it was an inflation, an increase in the average distance between particles, as new space was created.

Second, those first neutrinos did not escape-- there was no place to escape to. When the universe cooled to the point where protons and neutrons could exist, and such nucleosynthesis occurred as there was time enough to allow, there were three sources of neutrinos. The minor one was unstable isotopes undergoing beta decay (there weren't many heavy or unbalanced isotopes created.). The middling one was excited nucleons decaying by the emission of pions, pions decaying into muons, and muons decaying into electrons-- with neutrinos emitted at each step. The biggie was unattached neutrons, of which there were many, which decay into a proton, an electron, and an electron-type antineutrino. For every practical purpose, the mass that they were 'escaping' from was a black hole, the most ferocious one that ever existed, incorporating all the mass-energy of the universe in a very small space. At the event horizon of a black hole, by definition, the escape velocity is c. The best they could achieve would be orbit, even if they were emitted within a centimeter of the event horizon. The relict neutrinos we include in our theories today have slowed down (or as some say, cooled) as a result of collisions with each other, with the photons that eventually 'escaped' and later on with other massive particles.

There's no center to escape from. There never was. #-o

Best regards-- Steve

__________________
Ignoramus et ignorabamus.-- Reymond

Wir mussen wissen. Wir werden wissen.--Hilbert

Pick one.

I'm trying to understnd this idea.

Are the ancient neutrinos unique in signature due to their energy loss associated with the expansion?

If not, wouldn't the stars in the universe pollut the background with their enormous production? Supernova energy is released mainly in neutrinos, I believe, with about 100 neutrinos per photon. I would assume the CMB does not suffer from near this level of distortion.

So, can I make this another Big Bang Bullet, or not?

__________________
Lighten up! This is a stellar board!

One other question about the neutrino background is, I believe that the weight of a neutrino is currently known. Up until some time ago, many people believed they had no mass and hence could travel at the speed of light like photons, but now it's generally believe they do have a small mass (leading to the solution of the solar neutrino problem.) But what I'm wondering is, wouldn't the exact massmake a difference to the calculations? Or is the mass so small that it doesn't matter?

__________________
As above, so below

This was addressed earlier, but the neutrinos emitted by the Sun or by supernovae are much higher energy than the background neutrinos. Telling the difference is like being able to distinguish between gamma rays and radio waves (both are made of photons, right?).

But also remember that this particular experiment is extrapolating information about the neutrino background from its effect on the microwave background. So there wouldn't have been neutrinos from stars yet.

Not really, but I wouldn't exactly call this a pillar of the big bang, either. The results seem consistent with a neutrino background, but one could certainly come up with some other explanation.

First, we still don't know the exact values for the masses of the various neutrino types. We do have upper bounds, though. Even so, for the high energy neutrinos that we see from the Sun, the masses are low enough that they don't make a significant difference, since the total energy is much higher than the rest energy. It would probably make a difference for low energy neutrinos, but we cannot detect such neutrinos at this point. And since this paper is looking at the effects the neutrino background back around the time of last scattering for the microwave background, the neutrino background was higher energy then.

I should have read the prior posts more carefullly but once obfuscation set in, I started to bog-down (as usual).

My interpretation is.... the anisotropy of zillions of neutrinos, each with mass/energy, created additional, and detectable (and now observed), anisotropy in the CMB?

I understood this, but I had failed to see the energy difference which allows them to stand out in the crowd (if we could see such populations ).

I went ahead and added it to the "Big Bang Bullet" thread (of long ago), in case it gets resurrected. It's more of a stalagmite which might grow into a pillar.

__________________
Lighten up! This is a stellar board!

Exactly correct.

Yeah, I could buy that. To detect such low energy neutrinos directly, I can't think of anything other than just increasing the sheer volume of your detector (the probability of interaction is roughly proportional to the energy, so background neutrinos at a few eV are about a million times less likely to interact than solar neutrinos at a few MeV). We could try to expand AMANDA to include most of Antarctica. If that's not big enough, well, Europa is a big chunk of ice and water.