Universal density?

[sunshaker]

Just a question.

I just seen Nobel awarded for neutrino oscillations.

http://www.nobelprize.org/nobel_prizes/physics/laureates/2015/press.html

Wondered how this effects the missing mass in universe(dark matter)

 

If a neutrino is now thought to have a mass of a billionth of the mass of a proton,

There are 100's trillions of neutrino's passing through us every second, 100 billion per square cm,

Even at these levels there must then be the mass of 100 protons passing through every square cm,

 

But the density of space is worked out at 1 hydrogen atom per cubic cm?

.

But if the weight for neutrino's is correct, every cubic cm of space would always have the mass of at least 100 protons at any one time, making neutrino's the dominate cause of mass in the vacuum of space?

 

Are the levels of "dark matter mass" now going to be reduced?

 

 

[swansont]

Just a question.

I just seen Nobel awarded for neutrino oscillations.

http://www.nobelprize.org/nobel_prizes/physics/laureates/2015/press.html

Wondered how this effects the missing mass in universe(dark matter)

 

If a neutrino is now thought to have a mass of a billionth of the mass of a proton,

There are 100's trillions of neutrino's passing through us every second, 100 billion per square cm,

Even at these levels there must then be the mass of 100 protons passing through every square cm,

 

But the density of space is worked out at 1 hydrogen atom per cubic cm?

.

But if the weight for neutrino's is correct, every cubic cm of space would always have the mass of at least 100 protons at any one time, making neutrino's the dominate cause of mass in the vacuum of space?

 

Are the levels of "dark matter mass" now going to be reduced?

 

That neutrino flux is [edit: NOT] primarily from the sun, and not the flux one would expect in interstellar space, so the comparison to 1 proton/ cm³ is bogus. You're making the wrong comparison. If we use your number of the flux, 10^14/cm^2-sec at 1 AU, the flux out at e.g. the edge of the solar system, using ~31.6AU for convenience, is reduced by a factor of 1000. Smaller as you move further out — at 1 LY (an additional factor of 2000 in distance; 63241.1 AU per LY), you are reduced an addition factor of 4000000. Your mass of 100 protons has become the mass of 1/40000000th of a proton, and at a distance that's closer than half the distance to the nearest neighboring star.

 

High energy neutrinos won't stick around a galaxy and have the rotational effects we attribute to dark matter — they're above escape velocity. Interstellar neutrinos wouldn't contribute to those effects.

[sunshaker]

 

That neutrino flux is primarily from the sun, and not the flux one would expect in interstellar space, so the comparison to 1 proton/ cm³ is bogus.

You are most likely right, just trying to fully understand your answer relating to "that neutrino flux" is primarily from the sun.

 

 

 

The Sun, the Universe, and the nuclear reactions inside a power plant are sources of neutrinos. Every second we encounter 7 times more neutrinos from the Sun or 300 more Big Bang neutrinos than from a reactor at a distance of 1 km. The neutrino flux is measured as the number of neutrinos that pass through a square centimeter each second.

 

Are you saying there are less neutrino's between galaxies per cm?

I cannot yet find neutrino flux between galaxies, but surely these new measurements of neutrino mass in and around galaxies would add up to quite an amount of mass?

Edited October 6, 2015 by sunshaker

[Strange]

Neutrinos were one of the first candidates for dark matter because they are numerous and, well, dark. Unfortunately, it was found that particles with the velocities of neutrinos (close to the speed of light) do not match what we observe.

 

http://curious.astro.cornell.edu/the-universe/108-the-universe/cosmology-and-the-big-bang/dark-matter/661-what-is-hot-dark-matter-theory-intermediate

[swansont]

You are most likely right, just trying to fully understand your answer relating to "that neutrino flux" is primarily from the sun.

 

 

According to your infographic I was mistaken about that. My point that the neutrinos from the sun contribute little to interstellar flux still stands, as does the point about interstellar neutrinos not being able to do what we attribute to dark matter.

[sunshaker]

Neutrinos were one of the first candidates for dark matter because they are numerous and, well, dark. Unfortunately, it was found that particles with the velocities of neutrinos (close to the speed of light) do not match what we observe.

 

http://curious.astro.cornell.edu/the-universe/108-the-universe/cosmology-and-the-big-bang/dark-matter/661-what-is-hot-dark-matter-theory-intermediate

To me it seems it is a speed problem,

 

 

 

Two theories to explain the composition of dark matter are Hot Dark Matter theory (HDM) and Cold Dark Matter theory (CDM). The main difference between the two theories is the speed of the candidate particles. As you may have guessed, HDM particles move quickly (and are thus "hot") while CDM particles move slowly. Neutrinos are the main HDM candidate for dark matter as they are very weakly interacting and exist in such large numbers in the universe.

I have wondered whether this could be down to a similar effect we see with strobes?

If neutrino's continually pass through an area of space would they then cause a strobe effect?

 

The water droplets are falling at a 60th of second the light is flashing at 60th of second,

 

neutrino's moving at near speed of light, light pulses at light speed, illusion neutrino's are slowed down?

Edited October 6, 2015 by sunshaker

[swansont]

Another problem is that the comparison of a flux to a density is invalid. To get the density you have to divide by the speed, which will be close to c (3x10^10 cm/s). So that's about 100 neutrinos per cm^3. That's <30eV, and compared to almost 1 GeV for a proton. The mass contribution is small.

[sunshaker]

Another problem is that the comparison of a flux to a density is invalid. To get the density you have to divide by the speed, which will be close to c (3x10^10 cm/s). So that's about 100 neutrinos per cm^3. That's <30eV, and compared to almost 1 GeV for a proton. The mass contribution is small.

Why do you have to divide by speed, if we were able to freeze frame the universe at any moment there would always be 100 billion neutrino's in every square cm

(just not the same neutrino's).

[swansont]

Why do you have to divide by speed, if we were able to freeze frame the universe at any moment there would always be 100 billion neutrino's in every square cm

(just not the same neutrino's).

 

No, that's how many pass through in 1 second. If you have 100 x 10^12 passing through in 1 second, then 100 pass through in a picosecond. So even fewer if you "freeze" it.

 

You can get a large flux by having lots of particles moving slowly, such as with electric current, or the opposite case where the flux is large because you have a small number moving very fast.

 

You can think of this in 1D as well; let's say you have a particle passing a point once a second. If the stream of particles is moving 1 m/s that means the particles are a meter apart — 1 particle per meter. But if the particles are moving at 1000 km/s, then they are 1000 km apart - 1 particle per 1000 km. Both situation have the same "flux", but the linear density is a million times smaller for the faster moving particles. Same concept.

[Janus]

Why do you have to divide by speed, if we were able to freeze frame the universe at any moment there would always be 100 billion neutrino's in every square cm

(just not the same neutrino's).

Look at it this way: All the neutrinos that cross that a cm^2 cross-section in one sec include all the neutrinos that are at the cross-section at the beginning of the sec to those that cross it at the end of the second. The last ones start at a point some 3e10 centimeters way from the cross-section.

This means that if we freeze time at a given instant, to include all the neutrinos the would pass that 1 cm^2 in one second we have to look at the a volume 1cm X 1cm x3e^10cm in size. this is the volume you have to divide the number of neutrinos into to get the neutrino density.

 

This image may help

 

The green square is the area the neutrinos pass in one second and the yellow zone is the volume over which they are spread out in the instant at the beginning of the second.

Edited October 6, 2015 by Janus

[sunshaker]

Thanks for above answers, looks like I was mistaken about amount of neutrinos in any cm squared at any one time

I did find this article which also lowers the amount I thought,

 

 

We don’t know the mass of a neutrino exactly, but a decent rough estimate of it is 0.3 eV (or 5.35 x 10-37 kg). Scientists have indirect proof that neutrinos do have some mass, but as far as we can tell, they’re the lightest elementary particle in the universe. So there are lots of neutrinos in the universe, but they each don’t weigh very much. So that means in a cube of volume one Astronomical Unit on a side (where one AU is the distance from the sun to the earth, or about 93 million miles), there’s only about 600 tons worth of neutrinos! So the mass of neutrinos in empty space millions of miles across contains less mass than the typical apartment building.http://timeblimp.com/?page_id=1031

 

 

quick of thread topic question.

 

Average # of collisions with our body per lifetime = 5092

So, over the course of our lifetimes, about 5,000 neutrinos will wind up smacking into one of our atoms in our bodies. That’s about once a week!

I know the numbers are low, but i wonder about these "neutrino proton/neutron" collisions within our bodies, since neutrinos are now known to have mass,

What these collisions involve, what energy is produced/released?

Would they only damage atom they collide with, or would they effect cell/cells?

Could these neutrino collisions play any part in Cancers?

[Strange]

I know the numbers are low, but i wonder about these "neutrino proton/neutron" collisions within our bodies, since neutrinos are now known to have mass,

What these collisions involve, what energy is produced/released?

Would they only damage atom they collide with, or would they effect cell/cells?

Could these neutrino collisions play any part in Cancers?

 

Good question. There are many ways that a neutrino can interact with an atom. In some interactions (neutral current) it will just impart some momentum to the atom. I don't know if this could provide enough energy to break a chemical bond. (I doubt it but ...)

 

Other interactions can stimulate changes to the atom as a form of beta decay. This can release a positron, which will interact with an electron and release a gamma ray. This could cause some damage to cells.

 

However, the effect is insignificant compared to the radiation from other sources all around us. For example, about 5,000 atoms of potassium decay in your body every second (http://hps.org/publicinformation/ate/faqs/faqradbods.html).

 

So the neutrino flux is not something you need to worry about. Bananas and brazil nuts are much more dangerous.

[swansont]

Could these neutrino collisions play any part in Cancers?

 

Possibly; the interaction changes the nucleus so that it becomes a new element. If that happens in DNA then maybe there's potential for cancer. Or elsewhere in a cell, where you get some new chemical reaction. But 5,000 interactions over your life is tiny compared to disruptions from photons or (probably to a much lesser extent) electrons, protons and neutrons.

 

An average human dose over a lifetime is a reasonable fraction of a Sievert, which is a Joule of deposited energy per kg. If that's from 1 MeV photons in a 75 kg person, then it's more than 4 x 10^14 photons being absorbed. (possibly orders of magnitude more if this is lower energy x-rays). So photons are a billion times more of a risk.

[Janus]

Good question. There are many ways that a neutrino can interact with an atom. In some interactions (neutral current) it will just impart some momentum to the atom. I don't know if this could provide enough energy to break a chemical bond. (I doubt it but ...)

 

Other interactions can stimulate changes to the atom as a form of beta decay. This can release a positron, which will interact with an electron and release a gamma ray. This could cause some damage to cells.

 

However, the effect is insignificant compared to the radiation from other sources all around us. For example, about 5,000 atoms of potassium decay in your body every second (http://hps.org/publicinformation/ate/faqs/faqradbods.html).

 

So the neutrino flux is not something you need to worry about. Bananas and brazil nuts are much more dangerous.

And then there's Carbon-14, while there is not as much of it in the body, Carbon is one of the elements that makes up DNA, which is pretty much the worst place you want radioactive decay occurring. Just the carbon atom becoming a nitrogen atom alone is disruptive.

[sunshaker]

I was wondering if we could ever shield against neutrinos, some how using the weak force which seems the only force they interact with, Lead we would have to be billions of miles thick.

 

I wondered if neutrinos passed through a neutron star(or how far through) or whether they are deflected or decay somewhere within?

 

Next step "black holes" if neutrinos have mass, I would have thought they would perhaps form a "shell like structure" around a black hole.(unable to penetrate)

 

 

NASA X-ray Telescopes Find Black Hole May Be a Neutrino Factoryhttp://www.nasa.gov/centers/marshall/news/news/releases/2014/14-169.html

 

 

 

The team of researchers is still trying to develop a case for how Sagittarius A* might produce neutrinos. One idea is that it could happen when particles around the black hole are accelerated by a shock wave, like a sonic boom, that produces charged particles that decay to neutrinos.

Could it be possible that the black hole is not producing neutrinos, but that neutrinos build up has a "crust" around black hole, and after a while the black hole "pulses" ejecting this crust of neutrinos into space?

[Strange]

I was wondering if we could ever shield against neutrinos, some how using the weak force which seems the only force they interact with, Lead we would have to be billions of miles thick.

 

Why would you bother?

 

I wondered if neutrinos passed through a neutron star(or how far through) or whether they are deflected or decay somewhere within?

 

Interesting question. A quick skim of a paper that I could barely understand, seems to show that the neutrino mean free path is around a metre (depending on temperature, density and nature of the neutron star stuff, etc.) So they would be pretty effectively absorbed.

 

Next step "black holes" if neutrinos have mass, I would have thought they would perhaps form a "shell like structure" around a black hole.(unable to penetrate)

 

As with anything, with or without mass, they would fall into the black hole.

Edited October 8, 2015 by Strange

[Janus]

Interesting question. A quick skim of a paper that I could barely understand, seems to show that the neutrino mean free path is around a metre (depending on temperature, density and nature of the neutron star stuff, etc.) So they would be pretty effectively absorbed.

I think it's more likely that the neutron star would act like a scattering medium rather than an absorbing one.

[Strange]

I think it's more likely that the neutron star would act like a scattering medium rather than an absorbing one.

 

That is entirely possible - most of the paper was way over my head! And, thinking about it,it mentioned neutral current interactions, which I think means they wouldn't be absorbed.

 

If anyone wants to read more, searching for neutron star neutrino opacity will generate quite a lot of results.

[sunshaker]

 

Why would you bother?

 

Why not, Curiosity?, Because we know trillions of neutrinos pass through us and all life forms ever second, I would be curious how a shielded life form from neutrinos would evolve, and whether they evolved different to a non shielded life form.(whether these neutrino interactions made any difference.

 

 

Janus: I think it's more likely that the neutron star would act like a scattering medium rather than an absorbing one

could a black hole maybe also act has a scattering medium for neutrinos?

 

 

 

 

 

The team of researchers is still trying to develop a case for how Sagittarius A* might produce neutrinos. One idea is that it could happen when particles around the black hole are accelerated by a shock wave, like a sonic boom, that produces charged particles that decay to neutrinos.

 

 

Strange:: As with anything, with or without mass, they would fall into the black hole.

maybe, but as with the quote from above

 

"particles around the black hole are accelerated by a shock wave", What are these particles?, Could they be neutrinos?

 

I cannot get out my head the "soil layers" we see on Earth that build up over time,

 

if neutrinos cannot penetrate a neutron star far past a meter what happens to neutrinos that fall into a black hole,

 

Yes they would perhaps fall into the black hole,

but being unable to penetrate "into" black hole, could maybe form a "dense neutrino crust" and this "crust" is what is accelerated by the shock wave "in above quote".

Perhaps at a tipping point(growth of black hole), this "crust" causes the shock wave from within black hole expelling this "neutrino crust", so black hole is not producing neutrinos,, only expelling "neutrino crust",

 

A CRAP SHEDDING IT'S SHELL.

[Strange]

And then there's Carbon-14, while there is not as much of it in the body, Carbon is one of the elements that makes up DNA, which is pretty much the worst place you want radioactive decay occurring. Just the carbon atom becoming a nitrogen atom alone is disruptive.

 

Good point. And timely: the Nobel Prize for chemistry was "for having mapped, at a molecular level, how cells repair damaged DNA and safeguard the genetic information".

Why not, Curiosity?,

 

Fair enough.

 

Because we know trillions of neutrinos pass through us and all life forms ever second, I would be curious how a shielded life form from neutrinos would evolve, and whether they evolved different to a non shielded life form.(whether these neutrino interactions made any difference.

 

You have already seen that it would make no difference.

 

could a black hole maybe also act has a scattering medium for neutrinos?

 

Any neutrinos hitting the black hole would be absorbed. Any passing by would be lensed like photons.

 

"particles around the black hole are accelerated by a shock wave", What are these particles?, Could they be neutrinos?

 

It will be mainly plasma (protons and electrons). Neutrinos wouldn't be affected by a shock wave (because they only interact via the weak force) but it might cause interactions that generate more neutrinos, I suppose.

 

if neutrinos cannot penetrate a neutron star far past a meter what happens to neutrinos that fall into a black hole,

 

They fall in and stay there.

 

[sunshaker]

 

 

You have already seen that it would make no difference.

 

When?, where?, nothing has every been shielded from neutrinos, so I cannot know for sure whether it would make a difference, until you do that experiment.

 

 

They fall in and stay there.

 

 

Yang Bai of the University of Wisconsin in Madison, who co-authored a study about these results published in Physical Review D. “We now have the first evidence that an astronomical source – the Milky Way’s supermassive black hole – may be producing these very energetic neutrinos.”http://www.nasa.gov/centers/marshall/news/news/releases/2014/14-169.html

but do they?

 

I am not arguing one way or another, just into neutrinos at the moment ,

[swansont]

When?, where?, nothing has every been shielded from neutrinos, so I cannot know for sure whether it would make a difference, until you do that experiment.

but do they?

 

But we know that the neutrinos represent only a small fraction of nuclear interactions happening in the body.

 

From a simpler point of view, we know that life as we know it would be drastically changed if we shielded ourselves from neutrinos, because there would be no sunlight. We would have to be on the other side of an enormous amount of shielding material.

[Strange]

When?, where?, nothing has every been shielded from neutrinos, so I cannot know for sure whether it would make a difference, until you do that experiment.

but do they?

 

I am not arguing one way or another, just into neutrinos at the moment ,

 

Your (unreferenced) quote said: "So, over the course of our lifetimes, about 5,000 neutrinos will wind up smacking into one of our atoms in our bodies."

 

That is 5,000 per LIFETIME.

 

However, the effect is insignificant compared to the radiation from other sources all around us. For example, about 5,000 atoms of potassium decay in your body every second (http://hps.org/publicinformation/ate/faqs/faqradbods.html).

 

That is 5,000 per SECOND. And that is just one source, your total radiation dose is many times higher than that.

 

 

but do they?

 

If they enter the black hole they will never come out.

The source you quote is about neutrinos being generated outside the black hole.

[sunshaker]

 

But we know that the neutrinos represent only a small fraction of nuclear interactions happening in the body.

 

From a simpler point of view, we know that life as we know it would be drastically changed if we shielded ourselves from neutrinos, because there would be no sunlight. We would have to be on the other side of an enormous amount of shielding material.

I am not just talking about nuclear interactions in body, but actions yet unknown , I did read that in the presence of matter neutrinos could oscillate more vigorously between muon and tau neutrinos,

 

We are matter, can we make neutrinos oscillate?

 

If we could make neutrinos oscillate, does that means we are interacting with neutrinos?

[Strange]

I am not just talking about nuclear interactions in body, but actions yet unknown ,

 

Then no on can say what those unknown actions are, what their effects might be, or even if they exist.