Sorry, no. First, most physicists nowadays don't talk about mass increasing with speed. Mass in that sense is really just energy (divided by c^2). It's much more meaningful to talk about invariant mass (also called "rest mass", since it is unambiguously the mass the object has as measured in the frame of reference where it's at rest) in pretty much any context where mass, rather than energy, is relevant.
But, even ignoring that, your math is wrong. Using the interpretation that mass increases with speed, an object traveling at.5% of c will have a mass increase of about.00125%. An object traveling at 50% of c will have a mass increase of about 15.5%, and an object traveling at 95% of c will have a mass increase of 220% (so, it will be 3.2 times heavier than at rest).
Furthermore, it takes no energy expenditure at all to continue moving at a constant speed. You only need to expend energy to change your speed (or direction).
Not even close. Every time there is even the slightest hint of a signal that might be an indication of physics outside that which is already confirmed to be true (even when those hints don't even come close to sufficient statistical significance to believe) there will be a burst of several dozen new theory papers proposing models to explain the effect on the off chance that it might turn out to be true. The thing is, if you're a theorist, you want to be the first to come up with the ideas that end up getting confirmed; and, usually, to do that, you also end up proposing a whole bunch of ideas that turn out to be wrong.
The point is, most supposed anomalous measurements really do turn out to either be statistical fluctuations that go away as you collect more data, or systematic effects that turn out to be correctly explained in terms of properties of the experimental apparatus or mistakes in the data analysis.
The total cost of the LHC (which is shared among something like 25 countries) is about 2 years worth of US tax subsidies for oil companies.
Re:Who says that the Higgs has any mass at all
on
No Higgs Just Yet
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· Score: 1
While it's probably possible to create the Higgs at the Tevatron, it's not necessarily detectible. The problem is that, at certain mass ranges (like the most likely remaining one between 115 Gev and 145 GeV) the dominant Higgs decay signals have huge backgrounds to contend with; and, the Tevatron will simply not have enough data to say anything about possible excesses in that range.
Also, the fact that the proton/antiproton collisions at the Tevatron occur at 2 TeV does not actually mean that physics up to 2 TeV is accessible there. The problem is that protons are composite particles and physically interesting high energy processes are actually the result of collisions between the constituents of the (anti)protons (collectively, these constituents are termed "partons"). Since each (anti)proton has >3 partons (the actual number is indeterminate, but necessarily no smaller than 3), the parton involved in the collision will almost certainly have significantly less than the (anti)proton's total energy.
At the point when that whole range has been ruled out. Presently, there is still a window from about 115 GeV to 145 GeV that has not yet been excluded (and, for the most part, was not expected to be able to be excluded yet).
Re:Who says that the Higgs has any mass at all
on
No Higgs Just Yet
·
· Score: 1
The Standard Model of Particle Physics as a whole has about 20 parameters. All of them have been measured - some to significantly better precision than others - except for the mass of the Higgs. It is, quite literally, the only remaining free parameter in the model. Saying that it is a free parameter, however, is not the same as saying that any value of it works equally well. In particular, there is a technical problem with the Standard Model (violation of the unitarity bound on WW scattering, to be precise, which essentially implies that, at sufficiently high energies, a pair of W bosons will scatter with probability greater than 1) that is only solved if the Higgs mass is below about 1 TeV. In fact, even if the Standard Model is wrong, something has to fix this issue at an energy scale below 1 TeV. So, even if there is no Higgs in the standard sense, we expect to find something at energies that the LHC can access.
You've got it inside out, I'm afraid. The Standard Model would work just fine with no Higgs if no fundamental particles had any mass. (N.B. In such a situation, protons and neutrons would still be massive, as most of their mass is actually binding energy from the strong force.) The problem is that the mathematical structure of the theory is such that it makes certain nonsense predictions if any particles are given mass (like predicting certain processes to occur with probabilities greater than 100%). The Higgs circumvents this by allowing the masses of those particles that are massive (possibly other than neutrinos) to be a result of the interactions between the particles and the ground state of another field. This means that the behavior is different from that of a simple mass once you get near the the energy scale at which excited states of that extra field (the Higgs, that is) are accessible.
A couple of problems here. First, as with any other observation, we can only observe the invariance of c to a finite precision. It's always possible that relativity could fail in a way that would only lead to violations smaller than we can currently detect. And, CPT violation in only the neutrino sector could easily do this.
What really has no wiggle room is that CPT symmetry is a mathematical consequence of the spacetime symmetry that defines special relativity. If special relativity is correct, there cannot be any violations of CPT. Period. In other words, any violation of CPT requires a violation of relativity.
No. Gravity is completely irrelevant to particle physics experiments at the energy scale we can currently probe. Also, gravity alone couldn't create an effect distinguishing neutrinos from antineutrinos by mass, as gravity can't tell the difference between a particle and its antiparticle.
Neutrino scattering (or annihilation) processes are sufficiently rare that they couldn't possibly explain the size of the observed effect. Also, to annihilate an anti-neutrino to something with no electric charge, there already needs to be a neutrino present. Finally, the annihilation of neutrinos to photons is highly suppressed by the neutrino's lack of electric charge.
First, a picky point. SR says that the speed of light is the same in all inertial frames frames of reference. This is not true of rotating or accelerated frames.
Second, that statement is all that you need to work out the geometrical structure of spacetime. And, from the geometry, you can find that SR is equivalent to the statement that all physics is invariant under the symmetry inherent in the Lorentz transformations. From there, you can derive the possible mathematical representations of the symmetry - 1 scalar representations, 2 distinct spinor reps, a vector, and so on. In quantum field theory, any particle is an excited state of a field which carries one of these representations. A Lorentz invariant theory is one in which the fields are combined in only such ways that every interaction between the fields transforms as a scalar. This, however, is actually pretty much sufficient for the whole theory to be CPT invariant, as well, to the extent that to build a model with broken CPT, there actually must be terms that violate Lorentz symmetry.
Lorentz covariance means that a quantity changes in a way given by the appropriate Lorentz transformations under boosts or rotations. Lorentz invariance means that a quantity is unchanged under boosts or rotations. So, Lorentz invariance is a subset of Lorentz covariance which applies to frame-independent quantities like proper time, electric charge, or rest mass.
As for explaining these results, I think you'll find that a large majority of particle physicists (both theorists and experimentalists) will tell you that a 95% confidence level is actually very low. It means that a value (here something characterizing the difference between neutrinos and antineutrinos) differs from 0 by only twice the uncertainty in its value. In particle physics, its usually a bad idea to trust a result until there's enough data that deviation from 0 is at least five times the uncertainty in its value. (In fact, there have been cases where effects that had deviations from 0 of about 4.5 times their uncertainty that still turned out only to be statistical flukes.) But, those uncertainties tend to decrease in such a way that the uncertainty multiplied by the square root of the number of data points you're calculating the value from stays constant. So, this is rather slow to attain.
If, however, with a great deal more data, this effect still seems to be there, there are still some ways out. Essentially, you have to posit that somewhere between the production of the neutrino and its detection there's something unaccounted for which treats neutrinos and antineutrinos differently. Maybe there have been details overlooked about how propagating through matter (rather than antimatter) affects neutrinos (although this seems unlikely). There's also a paper I've run across recently which suggests that the standard treatment of neutrino oscillations misses a small dependence on the details of the physics by which the neutrinos are detected. (Personally, I'm waiting for people who know quite a bit more about quantum measurement and about neutrino oscillations to weigh in on this one.)
It's only once everything of this sort has been ruled out that we face the prospect of actual, honest-to-goodness CPT violation.
That's the p-value interpretation, I gave the confidence interval interpretation. Both are valid.
I would agree with this statement if you append your original statement to say "An experiment conducted this way would find more muon antineutrinos than muon neutrinos disappear 95% of the time, if our experimentally derived parameters are exactly correct." If no such assumption is made, you can't make any statement about how often an experiment would find a discrepancy. If, for example, there were no actual discrepancy, the experiment would only find one 5% of the time.
In other words, while the true value is stationary, both the experimentally derived value and the confidence interval are not.
For the universe to have a net baryon number requires CP to be a bad symmetry. CPT can still be conserved, provided that the violation in T compensates that in CP. But, if CPT is violated, so is Lorentz symmetry, which is the underpinning of special relativity. To this point, we've never seen any inconsistency between quantum physics and special relativity. It's only when you let spacetime itself be dynamic that there are mathematical problems. That is, the known inconsistency is between quantum physics and General Relativity. Special Relativity is one of the underpinning assumptions of all of our understanding of particle physics. Evidence that it is wrong would be a VERY BIG DEAL; but, would have very little to do with the problems of quantum gravity.
The correct statistical statement here would be that an experiment like this one would show a splitting between particle and anti-particle properties at least this large 5% of the time even if there were no difference at all.
Even if the data were strong enough to claim that they had definitely seen something not reasonably attributable to background events (which it isn't), these results would have very little bearing on the confirmation of SUSY. Even if the results were completely consistent with the expectations for neutralinos, there are dozens of other non-SUSY models which also predict dark matter; and, many of those have regions of parameter space that would be consistent with the very same dark matter detection results.
Giving neutrinos mass requires only the most trivial possible extension of the standard model. All that needs to be added are right-handed neutrinos, which would not interact under any of the forces in the standard model, but would allow neutrinos to interact with the Higgs field, which would let them get mass. Once there are masses, mixings come along for the ride naturally; and, the nature of those mixings depends on how strongly the various neutrinos couple to the Higgs field.
The reason people point to neutrino mass as a sign of new physics is that the picture I've painted above makes extremely light neutrinos look like a chance in a trillion accident. There are quite a few proposals for new physics that dynamically makes the masses very small. These are collectively usually referred to as "See-Saw" models. But, it's important to realize that they aren't actually necessary to get masses and mixings in the first place.
No. What is described here is simply the application of some mathematics that was discovered in studying string theory to some other, radically different problems. The piece of math (known as the AdS/CFT correspondence) basically tells you how to calculate interesting quantities in one type of theory (known as a conformal field theory) in terms of a totally different kind of theory (a general relativistic gravitational theory in an Anti deSitter space) and vice versa. This only gets attention because it happens to be the case that it is possible to do calculations in the dual theory in situations where we have no idea how to do the calculations in the theory we're actually interested in.
The point here is that this is really just a math trick that's letting people do calculations in situations where we previously were unable to do so. It has nothing to do with the question of the physical reality of string theory.
Check your numbers. If a 10^20 eV cosmic ray collides with a ~stationary proton in the atmosphere (proton mass is ~10^9 eV), the available energy in the collision is \sqrt{2mE} which will be about 4.5 x 10^14 eV. The top energy of the LHC is 1.4 x 10^13 eV. So, the cosmic ray collision still has 30 times as much energy available as the LHC collision.
Uh, what about this:
http://apod.nasa.gov/apod/image/0403/hudf_hst_big. jpg
The resolving power of a telescope is not the only measure of its utility. Hubble is in the unique position of being able to see extraordinarily faint objects, because it doesn't have to see through the glow of Earth's atmosphere. The only way to image objects as distant as those in the udf is to point a telescope at them for an extremely long time. However, on Earth's surface this long integrating time would lead much more quickly to a totally washed out image just due to the faint glow the entire sky acquires because of scattering in the atmosphere.
Now, correct me if I'm wrong; but, it was my understanding that the introduction of sterile neutrinos in no way requires additional families. The most natural thing would simply be to introduce right chiral neutrinos. All neutrinos are SU(3) and U(1)_Y singlets, and a right chiral neutrino would be an SU(2)_L singlet as well. Given that it wouldn't interact under the standard model gauge group, this (or, maybe more correctly, it's charge conjugate) would act as a sterile neutrino. I mean, isn't this basically what is done to induce the See-Saw mechanism for neutrino masses? Of course, that requires a right-handed neutrino with very large Majorana mass; but, the standard model families have room for three right-handed neutrinos and (I think) the See-Saw only requires one of them to be particularly heavy.
We already know that the Standard Model and GR are "broken" because we know of a major fundamental shortcoming of each. In the case of the standard model, the major dealbreaker is quite simply that it doesn't include any kind of description of gravity. Also, it has no way of accounting for the fact that neutrinos have mass. GR, on the other hand, we know to be broken because it isn't in any way quantum mechanical, which the universe is.
Given that we know that our best models are not only broken, but irrevocably incompatible with each other, it would be very nice if we could actually see something (anything) which might give us clues as to what a more fundamental theory should look like.
In principle, the way to do this would be to look for the effects of quantum gravity. Unfortunately, this would either require us to have some pre-existing quantum gravitational system to study or to use particle accelerators to speed up fundamental particles to so high an energy that the effects of gravity are a comparable size to those of the standard model forces. The first case is pretty much impossible, as the only quantum gravitational systems we know of at all are black holes and the big bang singularity; and, frankly, I don't see anyone trying to get either of those into their lab. In the second case, the effects of quantum gravity shouldn't really become significant until the particle has an energy equal to that of the Planck mass (~10^19 GeV). For comparison, the LHC at CERN, when it turns on, will accelerate protons to and energy of about 7000 GeV. A direct probe of quantum gravity would require a single particle with about the same energy as 1 quadrillion LHC protons. Again, this isn't likely to happen any time soon.
Your argument would be reasonable if the concentration of "normal" matter were the same everywhere. It isn't. The disk of a spiral galaxy (such as the one we're in) has a concentration of ordinary matter orders of magnitude larger than intergalactic space. So, all that is required for the concentration of ordinary matter in our solar system to be far larger than that of dark matter is that the distribution of dark matter is much more uniform than that of ordinary matter. This is actually expected, both in terms of the observations that lead us to conclude that dark matter exists and in terms of the idea of particles which do not interact through either the electromagnetic or strong forces.
If you look into the literature, you'll find the idea that every galaxy is embedded in a much larger dark matter "halo." So, while there is a heck of a lot of dark matter, it's also taking up a much larger space than the ordinary matter.
The matter/antimatter asymmetry is still a subject of significant research. But, there are suggestions that, at high enough energies, the symmetry between them does not hold in the same way as it does at low energies. This would mean that processes in the early universe could have broken that symmetry (at least as we see it) while still being consistent with some larger symmetry.
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Sorry, no. First, most physicists nowadays don't talk about mass increasing with speed. Mass in that sense is really just energy (divided by c^2). It's much more meaningful to talk about invariant mass (also called "rest mass", since it is unambiguously the mass the object has as measured in the frame of reference where it's at rest) in pretty much any context where mass, rather than energy, is relevant. But, even ignoring that, your math is wrong. Using the interpretation that mass increases with speed, an object traveling at .5% of c will have a mass increase of about .00125%. An object traveling at 50% of c will have a mass increase of about 15.5%, and an object traveling at 95% of c will have a mass increase of 220% (so, it will be 3.2 times heavier than at rest).
Furthermore, it takes no energy expenditure at all to continue moving at a constant speed. You only need to expend energy to change your speed (or direction).
Not even close. Every time there is even the slightest hint of a signal that might be an indication of physics outside that which is already confirmed to be true (even when those hints don't even come close to sufficient statistical significance to believe) there will be a burst of several dozen new theory papers proposing models to explain the effect on the off chance that it might turn out to be true. The thing is, if you're a theorist, you want to be the first to come up with the ideas that end up getting confirmed; and, usually, to do that, you also end up proposing a whole bunch of ideas that turn out to be wrong. The point is, most supposed anomalous measurements really do turn out to either be statistical fluctuations that go away as you collect more data, or systematic effects that turn out to be correctly explained in terms of properties of the experimental apparatus or mistakes in the data analysis.
The total cost of the LHC (which is shared among something like 25 countries) is about 2 years worth of US tax subsidies for oil companies.
While it's probably possible to create the Higgs at the Tevatron, it's not necessarily detectible. The problem is that, at certain mass ranges (like the most likely remaining one between 115 Gev and 145 GeV) the dominant Higgs decay signals have huge backgrounds to contend with; and, the Tevatron will simply not have enough data to say anything about possible excesses in that range. Also, the fact that the proton/antiproton collisions at the Tevatron occur at 2 TeV does not actually mean that physics up to 2 TeV is accessible there. The problem is that protons are composite particles and physically interesting high energy processes are actually the result of collisions between the constituents of the (anti)protons (collectively, these constituents are termed "partons"). Since each (anti)proton has >3 partons (the actual number is indeterminate, but necessarily no smaller than 3), the parton involved in the collision will almost certainly have significantly less than the (anti)proton's total energy.
At the point when that whole range has been ruled out. Presently, there is still a window from about 115 GeV to 145 GeV that has not yet been excluded (and, for the most part, was not expected to be able to be excluded yet).
The Standard Model of Particle Physics as a whole has about 20 parameters. All of them have been measured - some to significantly better precision than others - except for the mass of the Higgs. It is, quite literally, the only remaining free parameter in the model. Saying that it is a free parameter, however, is not the same as saying that any value of it works equally well. In particular, there is a technical problem with the Standard Model (violation of the unitarity bound on WW scattering, to be precise, which essentially implies that, at sufficiently high energies, a pair of W bosons will scatter with probability greater than 1) that is only solved if the Higgs mass is below about 1 TeV. In fact, even if the Standard Model is wrong, something has to fix this issue at an energy scale below 1 TeV. So, even if there is no Higgs in the standard sense, we expect to find something at energies that the LHC can access.
You've got it inside out, I'm afraid. The Standard Model would work just fine with no Higgs if no fundamental particles had any mass. (N.B. In such a situation, protons and neutrons would still be massive, as most of their mass is actually binding energy from the strong force.) The problem is that the mathematical structure of the theory is such that it makes certain nonsense predictions if any particles are given mass (like predicting certain processes to occur with probabilities greater than 100%). The Higgs circumvents this by allowing the masses of those particles that are massive (possibly other than neutrinos) to be a result of the interactions between the particles and the ground state of another field. This means that the behavior is different from that of a simple mass once you get near the the energy scale at which excited states of that extra field (the Higgs, that is) are accessible.
A couple of problems here. First, as with any other observation, we can only observe the invariance of c to a finite precision. It's always possible that relativity could fail in a way that would only lead to violations smaller than we can currently detect. And, CPT violation in only the neutrino sector could easily do this.
What really has no wiggle room is that CPT symmetry is a mathematical consequence of the spacetime symmetry that defines special relativity. If special relativity is correct, there cannot be any violations of CPT. Period. In other words, any violation of CPT requires a violation of relativity.
No. Gravity is completely irrelevant to particle physics experiments at the energy scale we can currently probe. Also, gravity alone couldn't create an effect distinguishing neutrinos from antineutrinos by mass, as gravity can't tell the difference between a particle and its antiparticle.
Neutrino scattering (or annihilation) processes are sufficiently rare that they couldn't possibly explain the size of the observed effect. Also, to annihilate an anti-neutrino to something with no electric charge, there already needs to be a neutrino present. Finally, the annihilation of neutrinos to photons is highly suppressed by the neutrino's lack of electric charge.
First, a picky point. SR says that the speed of light is the same in all inertial frames frames of reference. This is not true of rotating or accelerated frames.
Second, that statement is all that you need to work out the geometrical structure of spacetime. And, from the geometry, you can find that SR is equivalent to the statement that all physics is invariant under the symmetry inherent in the Lorentz transformations. From there, you can derive the possible mathematical representations of the symmetry - 1 scalar representations, 2 distinct spinor reps, a vector, and so on. In quantum field theory, any particle is an excited state of a field which carries one of these representations. A Lorentz invariant theory is one in which the fields are combined in only such ways that every interaction between the fields transforms as a scalar. This, however, is actually pretty much sufficient for the whole theory to be CPT invariant, as well, to the extent that to build a model with broken CPT, there actually must be terms that violate Lorentz symmetry.
Lorentz covariance means that a quantity changes in a way given by the appropriate Lorentz transformations under boosts or rotations. Lorentz invariance means that a quantity is unchanged under boosts or rotations. So, Lorentz invariance is a subset of Lorentz covariance which applies to frame-independent quantities like proper time, electric charge, or rest mass. As for explaining these results, I think you'll find that a large majority of particle physicists (both theorists and experimentalists) will tell you that a 95% confidence level is actually very low. It means that a value (here something characterizing the difference between neutrinos and antineutrinos) differs from 0 by only twice the uncertainty in its value. In particle physics, its usually a bad idea to trust a result until there's enough data that deviation from 0 is at least five times the uncertainty in its value. (In fact, there have been cases where effects that had deviations from 0 of about 4.5 times their uncertainty that still turned out only to be statistical flukes.) But, those uncertainties tend to decrease in such a way that the uncertainty multiplied by the square root of the number of data points you're calculating the value from stays constant. So, this is rather slow to attain. If, however, with a great deal more data, this effect still seems to be there, there are still some ways out. Essentially, you have to posit that somewhere between the production of the neutrino and its detection there's something unaccounted for which treats neutrinos and antineutrinos differently. Maybe there have been details overlooked about how propagating through matter (rather than antimatter) affects neutrinos (although this seems unlikely). There's also a paper I've run across recently which suggests that the standard treatment of neutrino oscillations misses a small dependence on the details of the physics by which the neutrinos are detected. (Personally, I'm waiting for people who know quite a bit more about quantum measurement and about neutrino oscillations to weigh in on this one.) It's only once everything of this sort has been ruled out that we face the prospect of actual, honest-to-goodness CPT violation.
The measured effect here is asymmetric between neutrinos and antineutrinos. So, X does not equal Y in a correct confidence interval interpretation.
That's the p-value interpretation, I gave the confidence interval interpretation. Both are valid.
I would agree with this statement if you append your original statement to say "An experiment conducted this way would find more muon antineutrinos than muon neutrinos disappear 95% of the time, if our experimentally derived parameters are exactly correct." If no such assumption is made, you can't make any statement about how often an experiment would find a discrepancy. If, for example, there were no actual discrepancy, the experiment would only find one 5% of the time. In other words, while the true value is stationary, both the experimentally derived value and the confidence interval are not.
For the universe to have a net baryon number requires CP to be a bad symmetry. CPT can still be conserved, provided that the violation in T compensates that in CP. But, if CPT is violated, so is Lorentz symmetry, which is the underpinning of special relativity. To this point, we've never seen any inconsistency between quantum physics and special relativity. It's only when you let spacetime itself be dynamic that there are mathematical problems. That is, the known inconsistency is between quantum physics and General Relativity. Special Relativity is one of the underpinning assumptions of all of our understanding of particle physics. Evidence that it is wrong would be a VERY BIG DEAL; but, would have very little to do with the problems of quantum gravity.
The correct statistical statement here would be that an experiment like this one would show a splitting between particle and anti-particle properties at least this large 5% of the time even if there were no difference at all.
Even if the data were strong enough to claim that they had definitely seen something not reasonably attributable to background events (which it isn't), these results would have very little bearing on the confirmation of SUSY. Even if the results were completely consistent with the expectations for neutralinos, there are dozens of other non-SUSY models which also predict dark matter; and, many of those have regions of parameter space that would be consistent with the very same dark matter detection results.
Last numbers I've hear say that that won't happen for the next 7 Gyr, not 5.
Giving neutrinos mass requires only the most trivial possible extension of the standard model. All that needs to be added are right-handed neutrinos, which would not interact under any of the forces in the standard model, but would allow neutrinos to interact with the Higgs field, which would let them get mass. Once there are masses, mixings come along for the ride naturally; and, the nature of those mixings depends on how strongly the various neutrinos couple to the Higgs field.
The reason people point to neutrino mass as a sign of new physics is that the picture I've painted above makes extremely light neutrinos look like a chance in a trillion accident. There are quite a few proposals for new physics that dynamically makes the masses very small. These are collectively usually referred to as "See-Saw" models. But, it's important to realize that they aren't actually necessary to get masses and mixings in the first place.
No. What is described here is simply the application of some mathematics that was discovered in studying string theory to some other, radically different problems. The piece of math (known as the AdS/CFT correspondence) basically tells you how to calculate interesting quantities in one type of theory (known as a conformal field theory) in terms of a totally different kind of theory (a general relativistic gravitational theory in an Anti deSitter space) and vice versa. This only gets attention because it happens to be the case that it is possible to do calculations in the dual theory in situations where we have no idea how to do the calculations in the theory we're actually interested in. The point here is that this is really just a math trick that's letting people do calculations in situations where we previously were unable to do so. It has nothing to do with the question of the physical reality of string theory.
Check your numbers. If a 10^20 eV cosmic ray collides with a ~stationary proton in the atmosphere (proton mass is ~10^9 eV), the available energy in the collision is \sqrt{2mE} which will be about 4.5 x 10^14 eV. The top energy of the LHC is 1.4 x 10^13 eV. So, the cosmic ray collision still has 30 times as much energy available as the LHC collision.
Uh, what about this: http://apod.nasa.gov/apod/image/0403/hudf_hst_big. jpg
The resolving power of a telescope is not the only measure of its utility. Hubble is in the unique position of being able to see extraordinarily faint objects, because it doesn't have to see through the glow of Earth's atmosphere. The only way to image objects as distant as those in the udf is to point a telescope at them for an extremely long time. However, on Earth's surface this long integrating time would lead much more quickly to a totally washed out image just due to the faint glow the entire sky acquires because of scattering in the atmosphere.
Now, correct me if I'm wrong; but, it was my understanding that the introduction of sterile neutrinos in no way requires additional families. The most natural thing would simply be to introduce right chiral neutrinos. All neutrinos are SU(3) and U(1)_Y singlets, and a right chiral neutrino would be an SU(2)_L singlet as well. Given that it wouldn't interact under the standard model gauge group, this (or, maybe more correctly, it's charge conjugate) would act as a sterile neutrino. I mean, isn't this basically what is done to induce the See-Saw mechanism for neutrino masses? Of course, that requires a right-handed neutrino with very large Majorana mass; but, the standard model families have room for three right-handed neutrinos and (I think) the See-Saw only requires one of them to be particularly heavy.
We already know that the Standard Model and GR are "broken" because we know of a major fundamental shortcoming of each. In the case of the standard model, the major dealbreaker is quite simply that it doesn't include any kind of description of gravity. Also, it has no way of accounting for the fact that neutrinos have mass. GR, on the other hand, we know to be broken because it isn't in any way quantum mechanical, which the universe is. Given that we know that our best models are not only broken, but irrevocably incompatible with each other, it would be very nice if we could actually see something (anything) which might give us clues as to what a more fundamental theory should look like. In principle, the way to do this would be to look for the effects of quantum gravity. Unfortunately, this would either require us to have some pre-existing quantum gravitational system to study or to use particle accelerators to speed up fundamental particles to so high an energy that the effects of gravity are a comparable size to those of the standard model forces. The first case is pretty much impossible, as the only quantum gravitational systems we know of at all are black holes and the big bang singularity; and, frankly, I don't see anyone trying to get either of those into their lab. In the second case, the effects of quantum gravity shouldn't really become significant until the particle has an energy equal to that of the Planck mass (~10^19 GeV). For comparison, the LHC at CERN, when it turns on, will accelerate protons to and energy of about 7000 GeV. A direct probe of quantum gravity would require a single particle with about the same energy as 1 quadrillion LHC protons. Again, this isn't likely to happen any time soon.
Your argument would be reasonable if the concentration of "normal" matter were the same everywhere. It isn't. The disk of a spiral galaxy (such as the one we're in) has a concentration of ordinary matter orders of magnitude larger than intergalactic space. So, all that is required for the concentration of ordinary matter in our solar system to be far larger than that of dark matter is that the distribution of dark matter is much more uniform than that of ordinary matter. This is actually expected, both in terms of the observations that lead us to conclude that dark matter exists and in terms of the idea of particles which do not interact through either the electromagnetic or strong forces. If you look into the literature, you'll find the idea that every galaxy is embedded in a much larger dark matter "halo." So, while there is a heck of a lot of dark matter, it's also taking up a much larger space than the ordinary matter. The matter/antimatter asymmetry is still a subject of significant research. But, there are suggestions that, at high enough energies, the symmetry between them does not hold in the same way as it does at low energies. This would mean that processes in the early universe could have broken that symmetry (at least as we see it) while still being consistent with some larger symmetry.