Neutrinos got that mass!

[Reynard]

Just heard a report that they know neutrinos have mass, very, very tiny mass but enough that the numbers of neutrinos in the universe could have mass equivalent to all the stars in the universe. Did we discover that missing mass attributed to dark matter? Does this change ANYTHING in Traveller?

 

[wbnc]

Just heard a report that they know neutrinos have mass, very, very tiny mass but enough that the numbers of neutrinos in the universe could have mass equivalent to all the stars in the universe. Did we discover that missing mass attributed to dark matter? Does this change ANYTHING in Traveller?

Not really neutrinos pass though you're body every day without affect..they pass though miles of stone, with no effect. Now when performing certain ragged edge of physics behaviors it might come into play...but that's a question for a high energy physicist not a hack writer like me.

 

[tolcreator]

According to wiki, dark matter composes 84.5% of matter in the universe. So even if neutrinos equalled the mass of visible matter, that still leaves 69% of matter to account for.

 

[phavoc]

"dark" matter is still unproven. The Voyager probe discovered that atomic hydrogen outside of a solar system was far more prevalent than anyone suspected. All that undiscovered hydrogen has real mass, potentially enough to fill in the equations where dark matter got inserted.

I've never been a fan of the idea of dark matter because I don't think astrophysics has enough information to correctly measure the mass of the universe at this time. Not to say that they haven't mathematically proven things existed before they could confirm them, but this one seems like a particularly large leap in faith.

 

[Reynard]

We don't really know what is dark matter. It's more a placeholder for mass we can't account for. Mass bearing neutrinos seems to account for some if not all that hidden mass.

 

[phavoc]

Exactly. It was a concept made up because someone couldn't balance their equation. Personally I think there's more out there that we don't know and we've barely been able to scratch the surface on the mysteries of the universe.

Determining the mass of the universe will require a heck of a lot more investigations. I don't put too much stock in dark matter being part of the final answer.

 

[Reynard]

We NEED that dark matter for all those neat superpowers unexplainable by any other reason! That and quantum physics.

 

[dragoner]

I've never been a fan of the idea of dark matter because I don't think astrophysics has enough information to correctly measure the mass of the universe at this time. Not to say that they haven't mathematically proven things existed before they could confirm them, but this one seems like a particularly large leap in faith.

When you take into account observations such as "lensing" or visual distortion, it becomes more empirical.

 

[Ataraxzy]

"dark" matter is still unproven. The Voyager probe discovered that atomic hydrogen outside of a solar system was far more prevalent than anyone suspected. All that undiscovered hydrogen has real mass, potentially enough to fill in the equations where dark matter got inserted.

I've never been a fan of the idea of dark matter because I don't think astrophysics has enough information to correctly measure the mass of the universe at this time. Not to say that they haven't mathematically proven things existed before they could confirm them, but this one seems like a particularly large leap in faith.

There are two issues here:

1. Dark matter is quite real. Atomic hydrogen acts in certain ways that are very much detectable.

Dark matter is ONLY detectable by the gravity it makes. If you take a look at the Bullet Cluster and look at the gravitational lensing, you'll see a huge amount of mass disconnected from the galaxies that passed through each other, bending light behind it that doesn't interact with anything at all. Atomic hydrogen would heat up and do all sorts of fun things like ionize.

2. We can know the total amount of something without knowing the exact composition of that thing. For example, I may not be able to tell exactly how much of my beaker of water is composed of everyday bacteria, but I know the total amount of stuff in the beaker. If there's more bacteria than I was expecting, this does not mean that the total amount of stuff in the beaker has changed.

Similarly, we know the total amount of stuff from other means: the Cosmic Microwave Background, the Sloan Digital Sky Survey, cosmological studies of entire superclusters of galaxies and more. That there's more atomic hydrogen than we expected does not change that we already know the total quantity of matter in the universe, just that we might have the ratios a bit wrong in certain places, which is the whole point of studying this stuff in the first place.

 

[Anonymous]

Just heard a report that they know neutrinos have mass, very, very tiny mass but enough that the numbers of neutrinos in the universe could have mass equivalent to all the stars in the universe. Did we discover that missing mass attributed to dark matter? Does this change ANYTHING in Traveller?

This actually isn't a new discovery and the paper was first published about 15 years ago (sometime around 2000). The nobel prize is often awarded for discoveries made quite a while ago.

The standard model says neutrinos have zero mass, but the neutrino's mass is so close to zero that it doesn't necessitate any change. It certainly hasn't caused any real problems in the 15 or so years since it was known.

 

[wbnc]

Just heard a report that they know neutrinos have mass, very, very tiny mass but enough that the numbers of neutrinos in the universe could have mass equivalent to all the stars in the universe. Did we discover that missing mass attributed to dark matter? Does this change ANYTHING in Traveller?

This actually isn't a new discovery and the paper was first published about 15 years ago (sometime around 2000). The nobel prize is often awarded for discoveries made quite a while ago.

The standard model says neutrinos have zero mass, but the neutrino's mass is so close to zero that it doesn't necessitate any change. It certainly hasn't caused any real problems in the 15 or so years since it was known.

More like the 15 billion years it has been known....well at least by the universe....we're a little slower on the uptake.

I' curious how they figured out the mass of a neutrino. they are hard enough to detect, much less make any sort of observations on.

 

[Anonymous]

I would be surprised if the mass or speed had been directly measured to a sufficent level of accuracy and precision. Instead it has been shown that neutrinos oscillate between different types as they move, which means they cannot be moving at light speed (at light speed they would not experience time in a manner that would allow them to oscillate), so they must have mass.

At least, that is my understanding of it. I'm unaware of the specific nature of the equipment used, so I couldn't tell you anything you can't learn from looking at neutrino detectors on wikipedia.

 

[phavoc]

"dark" matter is still unproven. The Voyager probe discovered that atomic hydrogen outside of a solar system was far more prevalent than anyone suspected. All that undiscovered hydrogen has real mass, potentially enough to fill in the equations where dark matter got inserted.

I've never been a fan of the idea of dark matter because I don't think astrophysics has enough information to correctly measure the mass of the universe at this time. Not to say that they haven't mathematically proven things existed before they could confirm them, but this one seems like a particularly large leap in faith.

There are two issues here:

1. Dark matter is quite real. Atomic hydrogen acts in certain ways that are very much detectable.

Dark matter is ONLY detectable by the gravity it makes. If you take a look at the Bullet Cluster and look at the gravitational lensing, you'll see a huge amount of mass disconnected from the galaxies that passed through each other, bending light behind it that doesn't interact with anything at all. Atomic hydrogen would heat up and do all sorts of fun things like ionize.

2. We can know the total amount of something without knowing the exact composition of that thing. For example, I may not be able to tell exactly how much of my beaker of water is composed of everyday bacteria, but I know the total amount of stuff in the beaker. If there's more bacteria than I was expecting, this does not mean that the total amount of stuff in the beaker has changed.

Similarly, we know the total amount of stuff from other means: the Cosmic Microwave Background, the Sloan Digital Sky Survey, cosmological studies of entire superclusters of galaxies and more. That there's more atomic hydrogen than we expected does not change that we already know the total quantity of matter in the universe, just that we might have the ratios a bit wrong in certain places, which is the whole point of studying this stuff in the first place.

One problem with that theory is the hydrogen found by Voyager. Up until Voyager officially escaped our solar system the hydrogen had never been detected, and never factored into any of the equations where dark matter came into being. We still can't detect it with our earth-bound instruments. And space is V-A-S-T. Even at the low amounts they found it adds up - just think of all the "empty" space between galaxies.

They've spent over a decade trying to prove dark matter exists and thus far every attempt has failed. The only "proof" that they have is theoretical. But like I said above, that's not to say it's totally wrong. Black holes were mathematically proven way before they were first observed. We know SOME things about them, but they are still a mystery. There are a number of mysteries still to be solved out there that science just scratches its head at because they can't be explained with our current understanding and knowledge of the universe.

Which is why I'm a bit skeptical about dark matter being the answer to the equation for the mass of the universe. We simply don't even know what we don't know about the workings of the universe, so it seems a bit odd for us to try and answer something where we don't even know where things end.

 

[Anonymous]

One problem with that theory is the hydrogen found by Voyager. Up until Voyager officially escaped our solar system the hydrogen had never been detected, and never factored into any of the equations where dark matter came into being. We still can't detect it with our earth-bound instruments. And space is V-A-S-T. Even at the low amounts they found it adds up - just think of all the "empty" space between galaxies.

This is untrue. It had long been known hydrogen existed in deep space. There are several scientific papers on this, for example: Varsavsky - The detection of molecular hydrogen in space (1965). Note the date. You can find the text of the paper with a quick Google search and the introduction lists other related papers.

In addition, we know the location of where dark matter must lie.

Exactly. It was a concept made up because someone couldn't balance their equation. Personally I think there's more out there that we don't know and we've barely been able to scratch the surface on the mysteries of the universe. Determining the mass of the universe will require a heck of a lot more investigations. I don't put too much stock in dark matter being part of the final answer.

All that means is whatever new stuff we discover will be called "dark matter".

The problem is the name "dark matter" makes people uneasy. If one had just said "There is an unknown type of matter out there, which we are calling Unknown Matter" there wouldn't be a problem. People can accept there can be types of matter we have not yet discovered. Now, replace the world "unknown" with "dark" and suddently people are getting worked up.

The other problem is that any replacement for the theory of gravity must remain consistent with current observations, and so far no-one has been able to get a "modified gravity" theory to work, which means additional matter is both the best explanation we can currently offer, and also the most likely answer to the problem given that we understand the effect of gravity to a very high degree of precision.

 

[phavoc]

One problem with that theory is the hydrogen found by Voyager. Up until Voyager officially escaped our solar system the hydrogen had never been detected, and never factored into any of the equations where dark matter came into being. We still can't detect it with our earth-bound instruments. And space is V-A-S-T. Even at the low amounts they found it adds up - just think of all the "empty" space between galaxies.

This is untrue. It had long been known hydrogen existed in deep space. There are several scientific papers on this, for example: Varsavsky - The detection of molecular hydrogen in space (1965). Note the date. You can find the text of the paper with a quick Google search and the introduction lists other related papers.

In addition, we know the location of where dark matter must lie.

Exactly. It was a concept made up because someone couldn't balance their equation. Personally I think there's more out there that we don't know and we've barely been able to scratch the surface on the mysteries of the universe. Determining the mass of the universe will require a heck of a lot more investigations. I don't put too much stock in dark matter being part of the final answer.

All that means is whatever new stuff we discover will be called "dark matter".

The problem is the name "dark matter" makes people uneasy. If one had just said "There is an unknown type of matter out there, which we are calling Unknown Matter" there wouldn't be a problem. People can accept there can be types of matter we have not yet discovered. Now, replace the world "unknown" with "dark" and suddently people are getting worked up.

The other problem is that any replacement for the theory of gravity must remain consistent with current observations, and so far no-one has been able to get a "modified gravity" theory to work, which means additional matter is both the best explanation we can currently offer, and also the most likely answer to the problem given that we understand the effect of gravity to a very high degree of precision.

You are right about the interstellar hydrogen. I should have said it was encountered at a much higher level than was originally theorized. But we still can't measure it with earthbound instrumentation, and we so far only have a single data point.

And I agree, there will probably always be some "dark matter" created to complete a theoretical equation.

 

[An Fhuiseog]

And I agree, there will probably always be some "dark matter" created to complete a theoretical equation.

Dark Matter isn't as such created to "complete an equation". Rather there already is a complete equation, the General Relativistic Field Equations. The problem is that it only predicts the correct rotational speed of galaxies if one assumes a large amount of undetected matter.

So either there is undetected (i.e. "dark") matter or General Relativity is wrong. Given the amount of evidence for General Relativity, the conservative thing to do is to assume Relativity is correct and there is some undetected matter. Observational constraints then imply that most of this matter is probably not conventional matter.

Observations of the bullet cluster have given additional weight to the idea of undetected matter, General Relativity being incorrect seems like a less likely possibility than it did even five years ago.

 

[phavoc]

Dark Matter isn't as such created to "complete an equation". Rather there already is a complete equation, the General Relativistic Field Equations. The problem is that it only predicts the correct rotational speed of galaxies if one assumes a large amount of undetected matter.

So either there is undetected (i.e. "dark") matter or General Relativity is wrong. Given the amount of evidence for General Relativity, the conservative thing to do is to assume Relativity is correct and there is some undetected matter. Observational constraints then imply that most of this matter is probably not conventional matter.

Observations of the bullet cluster have given additional weight to the idea of undetected matter, General Relativity being incorrect seems like a less likely possibility than it did even five years ago.

I know that dark matter, as a theory, came about somewhere in the 30's by Oort. I think his work was tossed to an extent because he had some things wrong, but he's the first to be credited with the theory. And I know that since then a number of other theories have come and gone and nobody has yet been able to do much with it as far as proving it's existence (I think we are up to, what three kinds of dark matter - cold, warm and hot?).

I had to go look up the Bullet Cluster example as evidence of it. But the data seems still inconclusive since that is cited as the "best" proof of it's existence. Astronomy and history are enjoyable subjects, but I check my non-existent higher math skillz at the door of the physics room. So I can offer layman's opinions, but I can't debate the math aspect of it.

At this point I think we've still got a lot to learn about the universe. And there's nothing to say that Einstein didn't miss something in his modeling that we've yet to find/discover. In the aviation field there are some set mathematical models that have been around about 100 years and everyone used the same ones over and over in aircraft design. And they worked. But a few years ago it was discovered that one of the core equations was incorrect. Obviously not enough to effect aerospace engineering because planes flew, and flew well, with the equation even though it was in error. The error was slight enough to not effect things or be detected for quite some time. The mysteries of the universe are more complicated than aerodynamics, and also because of history of other failed/incorrect theories, I think that the jury is still out on the existence of dark matter. Maybe it does exist. But at this point I think we don't know enough to really say one way or the other. I do understand that you need something to balance the equations, especially when you are operating in the total theoretical field. For whatever reason this particular theory has always smacked of human hubris to me though.

 

[Anonymous]

Hubris is a relative term.

1) Isn't it equally arrogant to assume that just because we have no direct detection of dark matter then general relativity must be wrong? Like humans have a right to instantly know stuff with just 10 years of research? We haven't had the ability to build the detectors for more than a few years.

2) Isn't the bullet cluster (and other sources) an indirect detection of dark matter? We have yet to detect gravity waves (our equipment is not yet sensitive enough) but isn't the fact that things fall to the ground an indirect detection of gravity? Why is one different from the other? We've had a theory of gravity since Isaac Newton in the 1600s and we have still not detected one single gravity wave and we don't know if gravitons even exist after 500 years! All we have is indirect evidence, and measurements of the movement of objects that agree with the mathematical predictions of the theory. So why do you believe in gravity? What if the force that pulls things down to Earth is pixie dust?

 

[phavoc]

Hubris is a relative term.

1) Isn't it equally arrogant to assume that just because we have no direct detection of dark matter then general relativity must be wrong? Like humans have a right to instantly know stuff with just 10 years of research? We haven't had the ability to build the detectors for more than a few years.

2) Isn't the bullet cluster (and other sources) an indirect detection of dark matter? We have yet to detect gravity waves (our equipment is not yet sensitive enough) but isn't the fact that things fall to the ground an indirect detection of gravity? Why is one different from the other? We've had a theory of gravity since Isaac Newton in the 1600s and we have still not detected one single gravity wave and we don't know if gravitons even exist after 500 years! All we have is indirect evidence, and measurements of the movement of objects that agree with the mathematical predictions of the theory. So why do you believe in gravity? What if the force that pulls things down to Earth is pixie dust?

It would be equally hubris to assume that general relativity can't be wrong.

We are still learning about matter and what causes the attraction between it. Greeks postulated atoms but it was a long time to prove it. Atoms where once the definitive building block of matter till we discovered electrons and neutrons and protons. And then they were the building blocks. Stop me if you've heard about how this story ends.

It does seem a bit of hubris to me to say we can estimate the mass of the universe when we are still discovering it, not to mention we've never left our planet except for a quick trip next door for some rocks. We have so much more to learn and discover. We have cataloged many things we don't know how to explain (quasar anyone) and seem to defy the laws of physics as we understand and know them. Science is great and we've proven things that were theoretical for centuries. And we've proven theories that were believed to be true to be untrue. Knowledge marches on and we are the better for it. But we should understand we don't know everything quite yet.

 

[Anonymous]

Neaatly avoiding the question of why you believe in gravity?