You should rest easy! It's been confirmed directly using planes and atomic clocks:
http://en.wikipedia.org/wiki/Hafele%E2%80%93Keating_experiment
as well as in observed ratios in muon detections from cosmic rays and in the operation of particle colliders like the LHC and at Fermilab. Also, interestingly, it is what is ultimately responsible for magnetic fields. The fact that you can stick these things to your fridge is a consequence of time slowing down and space shortening for charges in motion. It's fascinating.
Because it's collision-less, there's no effective way for a cloud of mutually-attracting DM particles to lose energy other than gravitational radiation. Normal matter will collide and heat up (accretion disks), losing kinetic energy as well as potential, and coalesce into a smaller object. DM clouds, as I understand it, have a much larger timescale for collapse. They don't "clump" very fast.
Wow --- blast from the past. I remember playing with a friend of mine in 9th grade at a local pizza joint. We each got good enough to roll it (I think that was level > 255) and play all day on a quarter each. That was really the way to do it since we got a break after each of us died. What a rush that game was.
My 14-year-old has expressed a mild interest in programming, so I'm going to load up VPython for him to try. The language is easy to learn, and he can make things "happen" on the screen very simply. It's a first introduction to watching what happens in loops, conditional statements, and then graphics terms like textures, polygons, and lighting. Sounds like a perfect introductory mix. I would have loved such a thing when I was getting started.
Juliet said "it worked" and also "let's get a coffee sometime" because as she was dying she caught a glimpse of her "purgatory" meeting with Sawyer. It actually didn't have anything to do with the bomb.
From the last two physics and astrophysics conferences I've been to (last 2 years) it's been running around 80-90% Mac. I actually tried to keep a more or less random sampling from the sessions I went to and counted up to about 100 computers each time.
I'm having a hard time understanding the question. The universe expands at different speeds that depend on the distance from us. If you're asking about a collapse where all the objects are moving towards us at the exact same speed, and if that speed were the speed of light, then we wouldn't see them until they were right on top of us. But the physical model for that is difficult to imagine.
There are some factors you're apparently unaware of. The long-term trend over many decades is roughly 0.15C or so, but on the scale of a particular decade, roughly 4 main variables influence warming: CO2 excess, El Nino cycles, solar radiance, and aerosol cooling (volcanoes, say). Over the last 12 years we've had, in combination, a decrease in El Nino heating from a record 1998 (which is why many "skeptics" pick this year as a starting point) as well as a cooling cycle in solar radiation. They both operate on roughly the same timescale. Underneath that, the CO2 excess from humans contributes a fairly constant 0.2C per decade of warmth, which is why the last decade and a half have shown roughly flat temperature increases instead of the expected cooling. If you look at the temperature plots, you can see this "wiggle" happening on a regular basis. We'd then expect, over the next decade, to have rapidly increasing temperatures as all the warming factors are positive, then probably a flat profile after that. The long-term trend, as shown in the plots, is still rising.
Their fiendishly clever plan to get more money hopefully flew under the radar of the other standing-room-only particle physicists and cosmologists in attendance at the seminar where the results were announced.
You mean the cautious interpretation that it's only 77% or so likely to be a positive signal? What does it mean that such a forecast is never wrong? I think science feels more like religion when you decide that's how it works. Do you have an alternate suggestion for interpreting this dataset?
I'm honestly having trouble coming up with an example of how, say, some item in a math curriculum is "right" for one district and not another. I might be on your side if there were actual experts in the fields making decisions on school boards instead of, for example, policemen and dentists deciding what a biology curriculum should include. Substituting experts making decisions on a national scale is a pretty good idea.
Oh, boy. Either you willfully neglect or are not aware of the gravitational radiation emitted from binary pulsars that must propagate at the speed of light.
I suppose, then, that the electric interaction is also infinitely fast, since otherwise electrons would have left their orbits around protons long ago.
And do you suppose that these cosmically large electric fields would have no observational consequences on spectral lines emitted in their presence, or on actual ionized gas in HII regions? I don't understand why you're so enamored with the "36 orders of magnitude" stuff. It has consequences --- the effects of such powerful fields should be 36 orders of magnitude easier to detect than gravitational effects. Where are they?
What?? Do you disagree that gamma rays are produced in nuclear reactions, like radioactive decay and particle/antiparticle annihilations? And that these reactions have absolutely nothing to do with the motion of electrons in orbits or in plasmas?
You sound very certain regarding matters you don't seem to know much about.
Good lord. We are to imagine that now galaxies are not approximately electrically neutral. Where to start...
In present-day computer models, which bear no resemblance to reality,
They don't? Which ones? In what way?
To our knowledge, matter is the only way that gravity can be generated.
Well, matter *and* energy, which includes electric/magnetic fields. That which generates/interacts with the gravitational field is really how we *define* what is matter in the first place.
However, because this matter has never been observed, it is called dark matter, a mysterious substance that does not show up in any of our instruments.
Except in those observations that would be able to detect anomalies in the gravitational field, like rotation curves of galaxies, gravitational lensing of distant sources, and the power spectrum of the CMB. It was the observations that led to the idea of matter that does not shine, pretty much like the theoretical prediction of the existence of Neptune (another kind of "dark matter"). Are not neutrinos *exactly* the kind of collisionless, weakly interacting particle that dark matter is theorized to be (except not massive enough)? Could neutrinos not have a more massive cousin? Why is this so impossible to accept?
There are theories that do take into account the electric force, which require neither dark energy or matter nor black holes in order to make sense of the torrent of data we get from space probes and telescopes.
And those theories are soundly refuted by the observational evidence. Not just observations of gravitational influence, but notions that the Sun does *not* shine via nuclear reactions is contradicted by observed neutrinos from the core.
It's not so much that current cosmologists and astrophysicists are crackpots, but that they are human. No one likes it, no matter what the field of study, if they are told that their life's work, a PhD thesis and whatever thick books with lots of equations in them they have written are simply wrong or at least grossly incomplete.
So what you imagine happens at conferences is that we astrophysicists *really* know the truth, but we're all shamed into cooperative silence because of our fear of being contradicted. You might be surprised that, in fact, the atmosphere at scientific gatherings (and in peer review in general) is quite the opposite. Physicists do know a thing or two about the physics of e/m fields and plasmas.
The *origin* and rough profile of the CMB was explained in the 1960s, but with such strong opinions on the subject then surely you're familiar with the discoveries in the last couple of decades of the details of the power spectrum of the CMB; the *anomalous* harmonics agree very well with the abundance of dark matter needed to cause gravitational lensing in clusters (Bullet Cluster) as well as the more familiar galactic rotation curves. These 3 independent predictions of the amount of dark matter agree very well, and are pretty strong evidence against any other proposed model. Right?
I don't understand your point. True, levels were much higher many millions of years ago. But that was not our ecosystem. Levels are higher now than at any other point since modern humans have been alive. And the most concerning factor is not just the level, but the *rate* of increase. We've had a fairly stable level (200-300 ppm) for the last million years or so. It is reasonable to be concerned about the effects on our climate if we suddenly jack it up by a factor of 2. Can humans *survive* higher levels? Sure. But our population patterns and activities would change drastically.
Slashdot Mirror
You should rest easy! It's been confirmed directly using planes and atomic clocks: http://en.wikipedia.org/wiki/Hafele%E2%80%93Keating_experiment as well as in observed ratios in muon detections from cosmic rays and in the operation of particle colliders like the LHC and at Fermilab. Also, interestingly, it is what is ultimately responsible for magnetic fields. The fact that you can stick these things to your fridge is a consequence of time slowing down and space shortening for charges in motion. It's fascinating.
Because it's collision-less, there's no effective way for a cloud of mutually-attracting DM particles to lose energy other than gravitational radiation. Normal matter will collide and heat up (accretion disks), losing kinetic energy as well as potential, and coalesce into a smaller object. DM clouds, as I understand it, have a much larger timescale for collapse. They don't "clump" very fast.
Wow --- blast from the past. I remember playing with a friend of mine in 9th grade at a local pizza joint. We each got good enough to roll it (I think that was level > 255) and play all day on a quarter each. That was really the way to do it since we got a break after each of us died. What a rush that game was.
My 14-year-old has expressed a mild interest in programming, so I'm going to load up VPython for him to try. The language is easy to learn, and he can make things "happen" on the screen very simply. It's a first introduction to watching what happens in loops, conditional statements, and then graphics terms like textures, polygons, and lighting. Sounds like a perfect introductory mix. I would have loved such a thing when I was getting started.
Juliet said "it worked" and also "let's get a coffee sometime" because as she was dying she caught a glimpse of her "purgatory" meeting with Sawyer. It actually didn't have anything to do with the bomb.
From the last two physics and astrophysics conferences I've been to (last 2 years) it's been running around 80-90% Mac. I actually tried to keep a more or less random sampling from the sessions I went to and counted up to about 100 computers each time.
I have to confess that I don't understand --- what will increase in response to CO2? What is the timescale?
Right, but that's 3% over equilibrium, and it's cumulative.
I'm having a hard time understanding the question. The universe expands at different speeds that depend on the distance from us. If you're asking about a collapse where all the objects are moving towards us at the exact same speed, and if that speed were the speed of light, then we wouldn't see them until they were right on top of us. But the physical model for that is difficult to imagine.
We'd know, because then objects that are 4 billion ly away would show a blue-shift.
There are some factors you're apparently unaware of. The long-term trend over many decades is roughly 0.15C or so, but on the scale of a particular decade, roughly 4 main variables influence warming: CO2 excess, El Nino cycles, solar radiance, and aerosol cooling (volcanoes, say). Over the last 12 years we've had, in combination, a decrease in El Nino heating from a record 1998 (which is why many "skeptics" pick this year as a starting point) as well as a cooling cycle in solar radiation. They both operate on roughly the same timescale. Underneath that, the CO2 excess from humans contributes a fairly constant 0.2C per decade of warmth, which is why the last decade and a half have shown roughly flat temperature increases instead of the expected cooling. If you look at the temperature plots, you can see this "wiggle" happening on a regular basis. We'd then expect, over the next decade, to have rapidly increasing temperatures as all the warming factors are positive, then probably a flat profile after that. The long-term trend, as shown in the plots, is still rising.
Kewl. LOST props.
Bedunkedunked
Thanks --- I was terribly imprecise in my haste.
I think the chances of the above being at all *right* is the 3-sigma event they're looking for. :)
Their fiendishly clever plan to get more money hopefully flew under the radar of the other standing-room-only particle physicists and cosmologists in attendance at the seminar where the results were announced.
You mean the cautious interpretation that it's only 77% or so likely to be a positive signal? What does it mean that such a forecast is never wrong? I think science feels more like religion when you decide that's how it works. Do you have an alternate suggestion for interpreting this dataset?
I'm honestly having trouble coming up with an example of how, say, some item in a math curriculum is "right" for one district and not another. I might be on your side if there were actual experts in the fields making decisions on school boards instead of, for example, policemen and dentists deciding what a biology curriculum should include. Substituting experts making decisions on a national scale is a pretty good idea.
That's because causation generates correlation. :)
I suppose, then, that the electric interaction is also infinitely fast, since otherwise electrons would have left their orbits around protons long ago.
And do you suppose that these cosmically large electric fields would have no observational consequences on spectral lines emitted in their presence, or on actual ionized gas in HII regions? I don't understand why you're so enamored with the "36 orders of magnitude" stuff. It has consequences --- the effects of such powerful fields should be 36 orders of magnitude easier to detect than gravitational effects. Where are they?
You sound very certain regarding matters you don't seem to know much about.
In present-day computer models, which bear no resemblance to reality,
They don't? Which ones? In what way?
To our knowledge, matter is the only way that gravity can be generated.
Well, matter *and* energy, which includes electric/magnetic fields. That which generates/interacts with the gravitational field is really how we *define* what is matter in the first place.
However, because this matter has never been observed, it is called dark matter, a mysterious substance that does not show up in any of our instruments.
Except in those observations that would be able to detect anomalies in the gravitational field, like rotation curves of galaxies, gravitational lensing of distant sources, and the power spectrum of the CMB. It was the observations that led to the idea of matter that does not shine, pretty much like the theoretical prediction of the existence of Neptune (another kind of "dark matter"). Are not neutrinos *exactly* the kind of collisionless, weakly interacting particle that dark matter is theorized to be (except not massive enough)? Could neutrinos not have a more massive cousin? Why is this so impossible to accept?
There are theories that do take into account the electric force, which require neither dark energy or matter nor black holes in order to make sense of the torrent of data we get from space probes and telescopes.
And those theories are soundly refuted by the observational evidence. Not just observations of gravitational influence, but notions that the Sun does *not* shine via nuclear reactions is contradicted by observed neutrinos from the core.
It's not so much that current cosmologists and astrophysicists are crackpots, but that they are human. No one likes it, no matter what the field of study, if they are told that their life's work, a PhD thesis and whatever thick books with lots of equations in them they have written are simply wrong or at least grossly incomplete.
So what you imagine happens at conferences is that we astrophysicists *really* know the truth, but we're all shamed into cooperative silence because of our fear of being contradicted. You might be surprised that, in fact, the atmosphere at scientific gatherings (and in peer review in general) is quite the opposite. Physicists do know a thing or two about the physics of e/m fields and plasmas.
The *origin* and rough profile of the CMB was explained in the 1960s, but with such strong opinions on the subject then surely you're familiar with the discoveries in the last couple of decades of the details of the power spectrum of the CMB; the *anomalous* harmonics agree very well with the abundance of dark matter needed to cause gravitational lensing in clusters (Bullet Cluster) as well as the more familiar galactic rotation curves. These 3 independent predictions of the amount of dark matter agree very well, and are pretty strong evidence against any other proposed model. Right?
I don't understand your point. True, levels were much higher many millions of years ago. But that was not our ecosystem. Levels are higher now than at any other point since modern humans have been alive. And the most concerning factor is not just the level, but the *rate* of increase. We've had a fairly stable level (200-300 ppm) for the last million years or so. It is reasonable to be concerned about the effects on our climate if we suddenly jack it up by a factor of 2. Can humans *survive* higher levels? Sure. But our population patterns and activities would change drastically.