What was wrong with my marijuana question? This is a hugely important issue that no one talks about. Because of the War on Drug Users, the US imprisons more of it's population than any other country on earth. We waste insane amounts of money tracking down and imprisoning harmless people, people who could otherwise be contributing to the economy. As a pot smoker and a voter, why would my desire to keep my freedom encourage contempt from the elected?
Ok, you asked. The way you frame and phrase your questions and statements is irritatingly immature, manipulative, and narrowly concerned with your own self-interest. You implicitly assert that pot smokers are, as a group, harmless economic contributors. This is at least an inaccurate mischaracterization of a segment of society of which I have substantial anecdotal evidence to the contrary. Further, a very large majority of the populace would not be swayed to your position by this characterization, or even care to consider the argument. On the scale of problems facing our country today, your interest in not being punished for what has been agreed by society as a crime does not register as a serious attempt to improve our situation, nor should it have been chosen as a top 5 question on technology to probe the acumen of a presidential candidate. The bar should be a little higher. No pun intended.
In general, we should applaud those who "desire to keep freedoms", but let's not get hyperbolic.
So I suppose it's my fault for not checking this thread and modding these questions down, but come on. "Why can't I get a straight answer?" and an inflammatory question on marijuana? This is why the elected hold the masses in contempt. Then two questions about patents and IP, where one begs the question of a broken patent system (not that I disagree, but it's a lousy way to ask a question). Are these the best presidential questions dealing with science and technology we can come up with? I'd like to hear something about energy policy, science education, NSF funding, international collaborations for basic research, and so on.
This is essentially a giant spinnaker. The main disadvantage is that it is really only good for downwind propulsion, whereas a conventional sail can make some progress upwind at an angle.
Our models can't accomodate the behavior, so we look to filling in the gaps with a magical substance that can't be seen, felt, or otherwise observed.
I don't understand this at all. Our gravitational models predict the existence of this stuff. It can certainly be "seen" and "observed" by its gravitational interaction with neighboring luminous matter. In what way is it "magical"? It must be non-baryonic, which is interesting, but not really magical. Recent weak-lensing observations are fairly conclusive --- it doesn't only interact to speed up stars in the outskirts of galaxies and influence cluster dynamics, but we can directly see its effect when the light from distant galaxies passes through it. Check out the Bullet Cluster results from last year. The light is getting lensed by something not associated with the luminous matter.
It's no more Ptolemaic than positing that there's more mass in the Universe that we are not capable of seeing than that which we are - you have to either add mass to the observed universe or add corrections to the equations. And that's the rub, both are really outlandish ways of dealing with observations that don't match our theories. Both should be pursued until we can come up with some predictions that do fit data.
It's not so outlandish to posit "dark matter" as you imply. It is simply that Newton's Laws predict a certain distribution of matter that, apparently, is not luminous. It also must be non-baryonic, which is really interesting.
But MOND is on ever more shaky ground now, especially after the results from the Bullet Cluster last year. Now, one must posit a different MOND for galactic dynamics than that of cluster dynamics. And, most damning of all, the Bullet Cluster reveals that MONDers must not only adjust the strength of gravity on precisely these scales, but also its direction, since the weak lensing effect is not in the direction of the luminous matter.
They're probably quite similar. It's not so much to do with the instititution, but you'll find that basically all general astronomy courses for non-science majors are not too rigorous, especially if you've had some science training in your background. And just a slight note in my defense, the presentations are just the introductions to the subjects that we talk about in more depth on the board and in group exercises. The Eng. Physics courses that require calculus are the same level as the ones I used to teach at the local comprehensive university.
I'm a fledgling beamer user --- I'd be glad to help if I can. It's pretty neat software, especially since I can embed pgf graphics (I'm also trying to learn the pgf package as well). If you're interested, here's a link to my astronomy class presentations. This is the first semester I'm writing them, so they'll probably change as I modify them over the winter holidays. I'm trying to subscribe to the model that they are illustrative, use full sentences, and I spend quite a bit of time talking and writing on the board as they are shown. Anyway, I'd be happy to send you the LaTeX source for them if you'd like.
This may be of no use, but if you're fluent in LaTeX, the pgf package is wonderful for procedural drawing. I use it with glee now for all my diagrams in the classes I teach.
Every time we turn on a new telescope we see something that shouldn't exist. First galaxies had too much rotational energy, so, after ignoring it as a non-issue for a couple of decades, we invented dark matter.
Ok, though I know a group of astrophysicists that would argue with the implication that their careers have been spent "ignoring" the implications of rotation curves.
Then we had this other problem that the universe's large-scale structure could not have possibly condensed into the super-clusters, so we invented another kind of dark matter, and needed ten times as much of it as the other stuff we couldn't find. I'm not following --- why is this stuff different? And the amount on large scales fits neatly with the 6-10x "normal" baryonic matter found in individual galaxies, as well as the amount derived from Big Bang Nucleosynthesis.
And then we started seeing fully formed galaxies at distances that meant they formed in a period of time that simply could not have possibly happened through gravity alone. So some more hand waving started, and everyone decided it was some other dark matter effect. That the extant dark matter helped the galaxies clump together is an expected outcome.
Ok, well you can pile up all the dark matter you want, but that's not going to make all the galaxies point in the same direction. And when we figure THAT out, I doubt there'll be any dark matter in there at all. MOND, STV, whatever, its time to stop with the warts and get on with the work.
So far, no one I'm aware of has implicated dark matter in this effect, if it's even real.
So, anyone want to put odds on dark matter going the way of the cublical atom in, say, ten years?
What's the relationship between the angular momentum of the Universe and the rotational velocity anomalies of outlying material in galaxies or intra-cluster excess mass? How would that account for the dark matter gravitational lensing results from last year? I'm not seeing why one has such an effect on the other.
I could *maybe* go along with your point if he were to be elected to office fully admitting his behavior. But when his policies and public persona are oriented completely opposite to his private behavior, I don't think you have much of a point.
Great. Only now do I learn that I'm in a field infested with conspiracy theories and beholden to public television. And just when I thought cosmology was getting *really* interesting. Whoever these guys are coming up with the current storyline, just tell them to keep it up --- it's fascinating work. I suppose I'll trudge on, whether I'm really just a marionette or not.
Sorry, the context was the post I was replying to, where the poster was imagining two objects headed for each other at a speed of 0.7c, each with respect to a rest frame. Certainly, the imprecision of the Galilean transformation depends upon the experimental sensitivity as well as the speed.
What really happens is that velocities don't add like that. They seem to for everyday objects, but relativistic effects become important at 0.7c. You should add them according to the Einstein formula:
v = (B+v')/(1 + Bv')
where B is the speed of one ship relative to an observer at rest (0.7c), and v' is the speed of the other ship in it's frame (0.7c). So the speed of one ship relative to the other is just v = 1.4/1.49 = 0.94c.
You can see that, for small speeds, the product in the denominator is small, so we have the usual addition.
In physics, we usually model the atoms in the solid pole as connected by stiff springs. The speed of communication of a force between one end and the other would depend on the stiffness of the springs (or, realistically, on the rigidity of the material the pole is made of). This is usually defined to be the speed of sound in the material, and it is typically much, much less than the speed of light.
Just because the opinion is popular doesn't make it right. It is certainly egotistic to assume that the project should not be funded just because it doesn't affect your life. It may well affect others. The implicit assumption is that your life and interests are complete and in the right; whereas I would argue that the cause is right, and something about you might be broken if you can't see the worthiness of it. One aspect of maturity is the ability to sacrifice for the benefit of others.
Either one. Members of a society should occasionally pay for things that are not in their self-interest. This, in my opinion, is surely in that category. It is so interesting that, also in my opinion, every member of the society should attempt to appreciate the science.
I'm not trying to be offensive, but that sounds like a remarkably egotistic statement. Should it be required to change your life in any way for you to care about it? Rather than something being wrong with the experiment in that it has no intersection with your interests, perhaps the problem is that your interests are too narrow to accommodate something that (I'd argue) is objectively interesting by any measure. Here is an opportunity for the average person to learn something about the fundamental nature of the Universe to understand the results.
You raise an excellent point. Fortunately, we astronomers have also thought of this. And the geologists before us.
We have very good computer models of stellar evolution that compute yields of basically all the elements in the periodic table from core-collapse supernovae, which is the type of explosion that would generate all the elements above iron. These have been checked against observed abundances and agree very well. In addition, we have another independent check in that we can compare the ages derived through radiometric means to those derived from globular cluster ages. These also agree well. And, to further make the case, it was noted in the article that about 6 different species of radioactive isotopes were observed, so it would be very unusual for *all 6* isotopes to have an anomalous abundance in just the right way as to make the ages all agree. I've worked with a number of people in this sub-field; for what it's worth, they really seem to know what they're doing.
I don't support modding religious people down merely because they disbelieve something, though I must say that, as a fellow Christian, it's distressing to see lots of non-specialists assume an air of superiority and bash a scientific field that they (in some cases even admit) they know basically nothing about. It's often charitable to assume that these scientists are, in most cases, very smart people who spend their whole professional lives engaged in the study of these phenomena. It is *highly* unlikely that any joe off the street is going to raise any intellectually serious issues that hadn't been thought of already. Scientists have the right authority to speak on behalf of their science. If you don't want to believe it, for whatever reason, that's up to you, though you might do well to *try* to understand why they say the things they do. It's fascinating stuff.
A necessary first step in determining what something is made of is to first determine where it is. Last year, when the distribution of dark matter in colliding clusters was found, it helped us understand how "collisionless" the stuff is and what it might be (and what it couldn't be) made of. So far, what we know for sure is that it interacts gravitationally with other matter. We've got to know where it is and how it's distributed to find out more. Does it have any effect on light passing through it other than gravitation? We'd need to know if it is or isn't in the way of a distant galaxy to find out.
Some sense at last. I just can't understand why rational people accept dark matter theories at face value, but claim to reject notions like 'ghosts' or 'god'.
Because there is evidence, lots of it, for its existence.
Hell, here's my theory: Dark Matter = God. He's everywhere, invisible, and keeps the universe together! See, explains everything really.
But, see, real astrophysicists are a bit more discerning. We've been able, through single galaxy dynamics, cluster dynamics, and gravitational lensing, to actually map out the distribution of this stuff. It's actually really interesting if you care to read the papers.
The interesting thing about the whole dark matter episode, is that it probably gives an insight as to how religions form. Someone has a wild idea, that someone else expands on, that someone else tries to validate, that someone else uses as doctrine, that someone else teaches, that someone else uses to explain a wild idea...scary really. Eventually you end up with so many layers of analysis and reference that everyone's forgotten that the *original* idea was bunk. It's like an upside down house of cards.
I'm glad that your idea of what science is really like is completely wrong. We're not all completely stupid. If we were, this field wouldn't be nearly as fascinating.
Slashdot Mirror
Not remotely.
Frankly, I'd like to hear something new about Fiscal Policy, Foreign Policy, Social Policy, and so on, as well as Science Policy.Me too, but the focus of the set of questions is supposed to be about science and technology.
Yep, that's exactly what I had in mind --- begging that particular question, the answer to which is assumed.
Ok, you asked. The way you frame and phrase your questions and statements is irritatingly immature, manipulative, and narrowly concerned with your own self-interest. You implicitly assert that pot smokers are, as a group, harmless economic contributors. This is at least an inaccurate mischaracterization of a segment of society of which I have substantial anecdotal evidence to the contrary. Further, a very large majority of the populace would not be swayed to your position by this characterization, or even care to consider the argument. On the scale of problems facing our country today, your interest in not being punished for what has been agreed by society as a crime does not register as a serious attempt to improve our situation, nor should it have been chosen as a top 5 question on technology to probe the acumen of a presidential candidate. The bar should be a little higher. No pun intended.
In general, we should applaud those who "desire to keep freedoms", but let's not get hyperbolic.
Just blowing off steam. Sheesh.
This is essentially a giant spinnaker. The main disadvantage is that it is really only good for downwind propulsion, whereas a conventional sail can make some progress upwind at an angle.
I don't understand this at all. Our gravitational models predict the existence of this stuff. It can certainly be "seen" and "observed" by its gravitational interaction with neighboring luminous matter. In what way is it "magical"? It must be non-baryonic, which is interesting, but not really magical. Recent weak-lensing observations are fairly conclusive --- it doesn't only interact to speed up stars in the outskirts of galaxies and influence cluster dynamics, but we can directly see its effect when the light from distant galaxies passes through it. Check out the Bullet Cluster results from last year. The light is getting lensed by something not associated with the luminous matter.
It's not so outlandish to posit "dark matter" as you imply. It is simply that Newton's Laws predict a certain distribution of matter that, apparently, is not luminous. It also must be non-baryonic, which is really interesting.
But MOND is on ever more shaky ground now, especially after the results from the Bullet Cluster last year. Now, one must posit a different MOND for galactic dynamics than that of cluster dynamics. And, most damning of all, the Bullet Cluster reveals that MONDers must not only adjust the strength of gravity on precisely these scales, but also its direction, since the weak lensing effect is not in the direction of the luminous matter.
Newton's Law for gravity specifies it as a 1/r^2 force. *Any* 1/r^2 force will behave the same way.
Perhaps there's a more elegant way, but I use
\setbeamercolor{background canvas}{bg=black}
right before the /frame statement, and then use \color{white} inside the frame. You have to set the background back to white when you're done, though.
And you're right, I'm starting to design graphics to build incrementally. I love that aspect.
They're probably quite similar. It's not so much to do with the instititution, but you'll find that basically all general astronomy courses for non-science majors are not too rigorous, especially if you've had some science training in your background. And just a slight note in my defense, the presentations are just the introductions to the subjects that we talk about in more depth on the board and in group exercises. The Eng. Physics courses that require calculus are the same level as the ones I used to teach at the local comprehensive university.
Beamer Astro stuff
This may be of no use, but if you're fluent in LaTeX, the pgf package is wonderful for procedural drawing. I use it with glee now for all my diagrams in the classes I teach.
Ok, though I know a group of astrophysicists that would argue with the implication that their careers have been spent "ignoring" the implications of rotation curves.
Then we had this other problem that the universe's large-scale structure could not have possibly condensed into the super-clusters, so we invented another kind of dark matter, and needed ten times as much of it as the other stuff we couldn't find.
I'm not following --- why is this stuff different? And the amount on large scales fits neatly with the 6-10x "normal" baryonic matter found in individual galaxies, as well as the amount derived from Big Bang Nucleosynthesis.
And then we started seeing fully formed galaxies at distances that meant they formed in a period of time that simply could not have possibly happened through gravity alone. So some more hand waving started, and everyone decided it was some other dark matter effect.
That the extant dark matter helped the galaxies clump together is an expected outcome.
Ok, well you can pile up all the dark matter you want, but that's not going to make all the galaxies point in the same direction. And when we figure THAT out, I doubt there'll be any dark matter in there at all. MOND, STV, whatever, its time to stop with the warts and get on with the work.
So far, no one I'm aware of has implicated dark matter in this effect, if it's even real.
What's the relationship between the angular momentum of the Universe and the rotational velocity anomalies of outlying material in galaxies or intra-cluster excess mass? How would that account for the dark matter gravitational lensing results from last year? I'm not seeing why one has such an effect on the other.
I could *maybe* go along with your point if he were to be elected to office fully admitting his behavior. But when his policies and public persona are oriented completely opposite to his private behavior, I don't think you have much of a point.
Great. Only now do I learn that I'm in a field infested with conspiracy theories and beholden to public television. And just when I thought cosmology was getting *really* interesting. Whoever these guys are coming up with the current storyline, just tell them to keep it up --- it's fascinating work. I suppose I'll trudge on, whether I'm really just a marionette or not.
Sorry, the context was the post I was replying to, where the poster was imagining two objects headed for each other at a speed of 0.7c, each with respect to a rest frame. Certainly, the imprecision of the Galilean transformation depends upon the experimental sensitivity as well as the speed.
What really happens is that velocities don't add like that. They seem to for everyday objects, but relativistic effects become important at 0.7c. You should add them according to the Einstein formula: v = (B+v')/(1 + Bv') where B is the speed of one ship relative to an observer at rest (0.7c), and v' is the speed of the other ship in it's frame (0.7c). So the speed of one ship relative to the other is just v = 1.4/1.49 = 0.94c. You can see that, for small speeds, the product in the denominator is small, so we have the usual addition.
In physics, we usually model the atoms in the solid pole as connected by stiff springs. The speed of communication of a force between one end and the other would depend on the stiffness of the springs (or, realistically, on the rigidity of the material the pole is made of). This is usually defined to be the speed of sound in the material, and it is typically much, much less than the speed of light.
Just because the opinion is popular doesn't make it right. It is certainly egotistic to assume that the project should not be funded just because it doesn't affect your life. It may well affect others. The implicit assumption is that your life and interests are complete and in the right; whereas I would argue that the cause is right, and something about you might be broken if you can't see the worthiness of it. One aspect of maturity is the ability to sacrifice for the benefit of others.
Either one. Members of a society should occasionally pay for things that are not in their self-interest. This, in my opinion, is surely in that category. It is so interesting that, also in my opinion, every member of the society should attempt to appreciate the science.
I'm not trying to be offensive, but that sounds like a remarkably egotistic statement. Should it be required to change your life in any way for you to care about it? Rather than something being wrong with the experiment in that it has no intersection with your interests, perhaps the problem is that your interests are too narrow to accommodate something that (I'd argue) is objectively interesting by any measure. Here is an opportunity for the average person to learn something about the fundamental nature of the Universe to understand the results.
We have very good computer models of stellar evolution that compute yields of basically all the elements in the periodic table from core-collapse supernovae, which is the type of explosion that would generate all the elements above iron. These have been checked against observed abundances and agree very well. In addition, we have another independent check in that we can compare the ages derived through radiometric means to those derived from globular cluster ages. These also agree well. And, to further make the case, it was noted in the article that about 6 different species of radioactive isotopes were observed, so it would be very unusual for *all 6* isotopes to have an anomalous abundance in just the right way as to make the ages all agree. I've worked with a number of people in this sub-field; for what it's worth, they really seem to know what they're doing.
I don't support modding religious people down merely because they disbelieve something, though I must say that, as a fellow Christian, it's distressing to see lots of non-specialists assume an air of superiority and bash a scientific field that they (in some cases even admit) they know basically nothing about. It's often charitable to assume that these scientists are, in most cases, very smart people who spend their whole professional lives engaged in the study of these phenomena. It is *highly* unlikely that any joe off the street is going to raise any intellectually serious issues that hadn't been thought of already. Scientists have the right authority to speak on behalf of their science. If you don't want to believe it, for whatever reason, that's up to you, though you might do well to *try* to understand why they say the things they do. It's fascinating stuff.
A necessary first step in determining what something is made of is to first determine where it is. Last year, when the distribution of dark matter in colliding clusters was found, it helped us understand how "collisionless" the stuff is and what it might be (and what it couldn't be) made of. So far, what we know for sure is that it interacts gravitationally with other matter. We've got to know where it is and how it's distributed to find out more. Does it have any effect on light passing through it other than gravitation? We'd need to know if it is or isn't in the way of a distant galaxy to find out.
Because there is evidence, lots of it, for its existence.
Hell, here's my theory: Dark Matter = God. He's everywhere, invisible, and keeps the universe together! See, explains everything really.
But, see, real astrophysicists are a bit more discerning. We've been able, through single galaxy dynamics, cluster dynamics, and gravitational lensing, to actually map out the distribution of this stuff. It's actually really interesting if you care to read the papers.
The interesting thing about the whole dark matter episode, is that it probably gives an insight as to how religions form. Someone has a wild idea, that someone else expands on, that someone else tries to validate, that someone else uses as doctrine, that someone else teaches, that someone else uses to explain a wild idea...scary really. Eventually you end up with so many layers of analysis and reference that everyone's forgotten that the *original* idea was bunk. It's like an upside down house of cards.
I'm glad that your idea of what science is really like is completely wrong. We're not all completely stupid. If we were, this field wouldn't be nearly as fascinating.