I'd agree that you have to be careful using calculators for pedagogical purposes, but I think it's absurd to suggest we throw them out of schools entirely. What do you think the point of mathematical education is? If it's just mechanics -- ie, learning to be really quick at long division -- then sure, calculators aren't very helpful. But I'd argue that math, at least from the upper-high-school level on, is about a way of thinking, about being able to argue symbolically in a way that is precise and beautiful. You need a solid grounding in some mechanics to be able to do that -- to understand what's going on, to see the elegance of later things -- but the mechanics aren't really the point.
So let our students be mediocre at long division. I couldn't care less. (When I need to do a complicated long division problem, I reach for the calculator -- why waste my time doing otherwise?) As long as they have been exposed to the mechanics, and (more fundamentally) how those mechanics can be applied in math and in life, who cares?
There are obvious caveats to my comments above, and this is why I partially agree with you -- teachers do need to make sure that students receive enough grounding in simple technique that they're not dependent on calculators for everything; for trivial calculations, nothing beats pen and paper. I think one ultimate goal is for the students to be able to solve any problem in the manner that is most appropriate -- clearly sometimes that will be in their heads, and just as clearly, sometimes a calculator is the way to go. Coupled with this, as I said above, is the goal of teaching the students to think in a mathematical way. Calculators obviously aren't a catch-all for accomplishing both goals, but I see no reason why they can't help you along the way.
I don't really care to deal with evolution -- I'm an astronomer, not a biologist, and I'd prefer to stick with what I can easily defend.:-) The point is that the Big Bang theory (and yes, it is just a theory) makes certain observational predictions which turn out to be quite good -- no one, to my knowledge anyway, has come up with a theory that can succeed in duplicating so many observational facts on so many diverse scales, with anything like so few a number of parameters. To elaborate a little, consider a few of the major observations that any cosmological theory must deal with --
the Hubble expansion: when we look at distant galaxies, they are all moving away from us with a speed that is directly proportional to their distance.
the existence and features of the Cosmic Microwave Background: when you look in the microwave part of the spectrum, you see a dull glow in every direction; that glow has the spectrum of a perfect blackbody at 2.7 K. small anisotropies (deviations from the mean temperature) do exist, but these are actually required by the theory -- and in fact many of their characteristics (like the angular scale at which they occur) is beautifully predicted by inflation. see the recent BOOMERanG results (there's a/. post about them) for more.
the abundances of light elements: this is a bit complicated, but basically certain elements were formed (primarily or exclusively) during the very early stages of the Universe. The BB theory predicts certain abundance ratios for these elements (which do depend on the matter density of the Universe, for obvious reasons) which are well borne out by observation.
Taken together, these constitute an extremely strong theory. I could go on and on about this -- there are literally hundreds of distinct problems in which inflation has been shown to provide a prediction which is compatible with observations. Tomorrow, someone may find some linchpin observation that brings inflation crashing down -- any scientist accepts that as a possibility for any theory. But as confirmation of the theory grows, as more and more observations back it up, as it is more fully developed and refined and made beautiful, we start to have a lot of confidence that such a linchpin will never be found.
I'd also point out that you seem to paint a dichotomy (creation vs. BB) which does not necessarily have to exist. The existence of a set of natural laws which govern the Universe does not preclude the existence of a Creator -- though this is touching on philosophical issues too rich for a few pithy comments here. (True, literal 7-day creation is pretty much out of line with BB/inflation.)I know many scientists who are deeply religious -- but such religiosity is ultimately a matter of faith. Sure, that presents, err, issues for them: there are some obvious conflicts between a worldview which says the Universe began about 13 billion years ago and one which says 4,000; but the point is that if you are REALLY religious and also REALLY care about the world around you (meaning you are unwilling to simply turn a blind eye to the overwhelming amount of evidence in favor of, say, inflation), you MUST deal with those issues rather than simply ignore them; your faith is an awfully weak one if it can't stand to do so.
It's a little trickier than that.:-) The detection of this gas does not mean that there is sufficient baryonic matter to close the Universe -- lousy news stories to the contrary notwithstanding. What it does mean is that a large fraction of the baryons in the Universe today can be found in the gas between galaxies; this is not a new idea, but it's nice to see (weak) confirmation that it's true at low redshifts as well as high ones.
Remember that we already "know" (or have strong constraints) on the overall baryon density from Big Bang nucleosynthesis (from measurements of the ratios of certain light elements). That's how we can make a statement like "a big fraction of the baryons in the universe are in this gas."
It's thought that much of the baryons in the universe might be contained in a "hot shocked" component of the intergalactic medium -- that is, a lot of stuff is thought to be in the range of a million or so K. The interesting problem there is that you hit a sort of "dead zone" in that temperature range where the gas is quite hard to detect -- hotter (say 10 million K) and you can see some X-ray emission (which is what Chandra sees); cooler, and you can actually see visible absorption lines. (More technically: the optical depth at the center of an absorption line goes roughly as one over the square root of the temperature. So hot stuff is harder to observe.)
If you're really interested in this stuff, check out the paper "Where are the baryons?" by Cen and Ostriker -- sorry I can't give you a better reference, but hunt on astro-ph or the Harvard abstract service and you'll find it.
Caveat: I haven't actually read the BOOMERANG group's paper, so I probably shouldn't even comment. But what the hell.
The way many of these groups arrive at their estimate that the universe is "flat" is basically from such power spectrum measurements. Basically, the first peak of that spectrum (at an angular scale of about l=200) implies (to within reasonably small error bars) that we live in a flat universe. (More rigorously, it implies that Omega_k, an effective density term arising from the curvature, is equal to zero.)
The "power spectrum" does tell you lots of other things, true. But so does the mere fact that the CMB spectrum itself is Planckian -- it's possible to show that energy injection by unknown particle species at early times would alter the spectrum that we see today. It's also possible to constrain lots of other cosmological things, like the redshift at which reionization occurs, by observing the spectrum. This is getting more technical than is really appropriate, so I'll stop -- point is, though, that the result here (and from other similar papers) is actually pretty significant. Doesn't mean there aren't other significant papers to be written.:-)
This should be moderated up, unlike many other posts that have appeared on this subject. Maybe we should introduce a "blatantly wrong" moderation modifier.:-)
True, but it'd be damn hard to pinpoint a "birthday" apart from the time it actually went up.:-) The time you set the last bolt? The time the main mirror was polished for the last time? Who knows. In any case, HST was in planning for a number of years before the 1985 integration you mention.
BTW, people may not realize just how long the life cycle on this sort of project is... for instance, the first meeting regarding the *Next Generation* Space Telescope (ie, the successor to HST) was held in, I think, 1989. NGST won't go up for another, oh, seven to ten years.:-)
You raise some good points, but I'd strongly disagree with the contention that the "real brunt work" is done by other satellites -- in fact, HST has contributed more (IMHO) to astronomy than *any* other satellite, ever. The pretty pictures are great (and you might be surprised how much science can be gleaned from such pictures), but there's also a lot of awfully hard-core stuff going on behind them. With Hubble, we've refined our notions of what goes on in supernovae (via SN 1987a), we've studied the environments in which stars form (O'Dell, Bally, etc's work on the Orion nebula), and we've gotten some strong hints as to the structure of the Universe as well as its ultimate fate. (Think of the "Key Project"'s determinations of H_0, or the various supernovae groups' determinations that there may have to be a "cosmological constant.")
I guess my point is this: sure, there are areas Hubble will never be able to probe, questions it will never be able to answer, pictures it will never be able to take. And other satellites have been designed to probe those areas, answer those questions, take those pictures. But Hubble has done what it was *designed* to do, extremely well. We'll all be sorry when it's gone.;-)
It's an interesting question, but I think the answer has more to do with what kind of students they plan on attracting. Cheating is, IMHO, not a major concern at many good universities because the students are simply relied upon not to do it. At Rice, for instance, the overwhelming majority of my exams were take-home, and the few that weren't were seldom proctored in any way; the so-called "Honor Code" was a pretty big deal there, and I don't know many people who would've considered breaking it. (Ours was basically just a statement you wrote on each exam, "I have neither given nor received any aid on this exam.") And what's more, I really don't think this was because of the possible penalties if you were somehow proven to have cheated (which were pretty severe) -- more compelling than that, I think, was the knowledge that we had so many liberties with our exams/homeworks/whatever, and that breaking the Code endangered those liberties.
So I don't know. Within a certain number and class of students, I don't think cheating is a big enough concern to justify elaborate mechanisms to prevent it. To be fair, I am currently a graduate student at another, larger university (which shall remain nameless) -- and here, the custom is to monitor like a hawk whenever we give exams, require students to record their seat numbers, use multiple versions of exams, etc. This is a little disturbing to me, but the students seem to justify the approach -- I've caught more than one blatantly copying off another student, for instance. Where will this online university fall between these schemes? I dunno -- but I feel fairly certain that if you only impose mechanisms to detect/prevent cheating, without convincing students that it's really in their best interests not to cheat, someone will eventually figure out a way to circumvent those mechanisms.
I'd just like to point out that your bit about "$10,000 should be within your means if you are a high technology professional" is crap. "High-technology professional," whatever the hell that is, sure. Physicist -- no way in hell.:-) (I don't know any physicists who would be willing to wager $10k on anything, much less something like this. Notice that when Kip Thorne and Steven Hawking made their famous series of wagers, they were for things like a subscription to Playboy instead.)
And at the risk of getting involved in a flamewar not of my own design: I think defending your ideas by offering a ridiculous wager is not the best way to convince any members of the scientific community of the veracity of your claims. What fperez says is wrong? Fine, tell me how. Your assertion is intriguing, but a follow-up post saying, "my collaborators are so-and-so, we've submitted to PhysRev A, etc." would've been (IMHO) more reasonable than this.
Yeah, I think the article pretty much missed the point, which is that this is (apparently) the highest redshift that has been determined spectroscopically. (Is it, though? I don't know offhand, but I really thought there had been a couple z=6 determinations. Oh well.)
As you mention, the "most distant" things that have been observed (to my knowledge) are so-called "blue drop-out" galaxies. (You're probably aware of this, but: You take an image in several wavelength bands, and find some galaxy that is definitely present in the longer-wavelength ones but gone in the short-wavelength images. By figuring out the point where the galaxy disappears, you can in principle determine its redshift. Less precise -- and also much less time-consuming -- than spectroscopic redshifts, for obvious reasons.:-))
You can be a little more precise than just saying it's a relic of the Big Bang, though. The CMB is basically the remnant afterglow of the moment when the Universe became transparent to its own radiation -- before that, for various reasons, photons couldn't get very far. There's a lot more going on here than I really want to go into, but a couple important points: the CMB is a very important reason why we like the Big Bang theory. It has the spectrum of a perfect blackbody (to within one part in 10^5 or so) at 3 K (and yes, that apparent temp. is a result of the redshift); that fact alone imposes pretty fundamental limitations on what could've happened in the early stages of the Universe. (It turns out, for instance, that you can't have had energy injection by spooky other particles, because we would see a non-Planckian CMB.) Furthermore, one particular property of the CMB -- that it looks the same wherever we look (once you have accounted for the motion of our galaxy relative to it) -- is one reason we like inflation, which suggests that one very tiny region of the initial Universe underwent a period of unimaginably speedy expansion. (Again, this can get arbitrarily complicated. But the point is that in a simple uniform expansion, the stuff to our left and the stuff to our right would never have had the chance to equilibrate with each other; hence, they should look different. Inflation "solves" this by requiring that everything we see came from one very very tiny region in the initial Universe.)
It's a good bet that the portion of the American public that gets their political news primarily from online sources -- and more specifically, the portion that is actually likely to look at any candidate's website -- is not a completely representative cross-section of America. Does this affect, or can you imagine it affecting in the future, the messages you display on your website? Clearly the ideas you talk about on TV and the ideas you talk about on your site have to be basically the same, but do you make a conscious effort to tailor the way you convey those ideas to the population you're sampling via each medium? If not, can you imagine situations in which it might be greatly to your advantage to do so? Or severely detrimental?
I'm aware of Zubrin's book; a few of the statements he makes are wrong, though. Sorry.:-)
The tether approach has been thought about at great length and if we decide to go with a full-time centrifuge, that's certainly the way to do it. I wish I could direct you to a good page on why even this is not ready for prime time, but I can't. Briefly, I seem to recall that the problems with any large-scale centrifuge are that people just tend to be screwed up by the Coriolis effects -- I remember watching a great video of someone trying to throw a ball around in a centrifuge, and you'd be surprised how messed up they were. (To be fair: a lot of people think that you would eventually adjust to these effects.) Would that it were as easy as the scenes in 2001. The only thing a tether system saves you is the additional weight you would otherwise have to be propelling in order to get the centrifuge effect. (Ie, it's a lot easier to lift a couple pods and a tether than it is to lift a giant ring.) More promising, IMHO, are short-term personal centrifuges -- it's looking as though you don't need anything like 24-hour exposure to gravity to prevent most of the ill effects of microgravity.
As for the radiation: I actually don't recall Zubrin's argument here, so maybe I'm giving him less credit than he deserves. But the real killers in space are the massive particles down in that lower right hand side of the periodic table -- these are the ones I was referring to earlier when I said that we don't have particularly effective shielding. Also: background exposure levels are not that high, true, but as you talk about multiple-year missions, the chance of getting an anomalous exposure (ie, from a solar flare) becomes unacceptably high.
There are plenty of people who believe these risks are acceptable. After all, they argue, these guys are astronauts! They're used to risks. But I don't think we'll do it (aka, I don't think NASA or any other responsible agency will fund it) until we can deal with these things much better than we do now.
Your comments are well-phrased and well-reasoned; my only problem is with your "there is no technical reason..." bit. It's misleading to say this, but a lot of people seem to believe it -- it's true that we have the capability to build a ship to send someone to Mars; building a semi-permanent outpost there would be far trickier, but whatever. But we're actually quite a ways from being able to do any of those things safely. Here are a couple reasons why.
Radiation effects. The details are somewhat complicated, but the point is this: nasty things can hit you while you're in space. Shuttle astronauts don't have to worry about some of these, because the Earth's magnetic field shields them while they're in orbit. What is rough about this is that we don't have effective shielding for some of these things -- at least not shielding that is considered practical. And some things are actually more dangerous once you've slowed them down with shielding -- unmolested, they might just raise your chance of getting a tumor or something, but fiddling with them is in a sense playing with fire. Note that these risks were issues in the Moon launches -- but they were considered acceptable over the course of the few days of each mission; they are (IMHO) not acceptable when you're talking about a six month mission through interplanetary space.
Microgravity effects. This is another of those risk factors that you can consider acceptable or not. It's been shown that, to put it bluntly, bad shit starts to happen to you once you've been in a zero-g environment for a while. Bone degradation effects may be permanent, etc; for more info on this, check out the National Space Biomedical Research Institute. People have looked (very seriously) at creating artificial gravity for the sort expedition you're talking about, but the problems there are enormous, too.
Lest I seem too pessimistic, let me say this: I think going to, say, Mars is a worthy goal. I haven't thought that much about establishing an outpost there (which has all sorts of other issues associated with it), but that would be pretty neat too.:-) BUT you are shooting yourself in the foot by telling people it's an easy problem -- eventually, they might believe you. I think all the issues I mentioned above will be solved. (There is promising research in short-duration centrifuges, and some less-promising but still cool work in tether-based large centrifuges. But all of these have a lot of testing to go through before they'll be ready to rock.) But it'll be a while, and people should know that.
Heh heh heh. There _is_ some subjectivity ("artistic interpretation") that goes on... but not with any intent to mislead, just in the attempt to give the best picture. What you get from Hubble is just a CCD readout -- that is, for each filter in which you take an image, you get (roughly speaking) a number of photons for each pixel. So the image, when you look at it, is greyscale, not spiffy reds and greens and blues.
To get a color picture, you basically pick a color to go along with each filter image -- these are pretty sensible (usually), but there's still a bit of leeway. Conventional choices might be, for instance, H-alpha (H transition, at 6563 A) as red , H-beta (4861) as blue, and maybe [OIII] 5007 as green. But depending on what you wanted to show, you might choose different color-wavelength correspondences.
Also, most of the images you see in PR releases and such have probably gone through additional processes to make them look nice -- ie gaussian smoothing filters, hand-removal of pesky lingering cosmic rays, subtle implantation of subliminal messages ("hubble good. nasa good."), whatever. It's all in good fun.
What do ya mean by "active observation"? I mean, there's not a whole hell of a lot we can _do_ to things that are a billion light years away. We're pretty much constrained to sit here and watch what comes our way.
There are a few other projects that will be around after Hubble (though some will go up before HST comes down) -- the Next Generation Space Telescope is the "biggest," I guess. (Other recent/upcoming telescopes, designed to look at different parts of the spectrum, include FUSE, XMM, Chandra/AXAF, etc.) One interesting bit is that there isn't currently a telescope in the works that will fully cover the HST's observation range -- that is, there are parts of the spectrum that are going to get the big 'ole shaft when HST comes down. But enough of this.
I really hope you're kidding. For my money, the Hubble is one of the best scientific investments we've _ever_ made -- it's absolutely unreal how much it has furthered astronomy and astrophysics in the years since it went up. The pretty pictures are great, sure -- they are beautiful, and beauty is I think something that any civilization discounts at its own peril. But there has also been a lot of pretty hard-core science from the Hubble -- witness the HST Key Project, which used the Hubble to observe remote Cepheids and calibrate the astronomical distance scale. Knowing the distance to all the objects in our Universe (and hence how old the light we're seeing is, how old our Universe is, etc.) is a pretty big deal, don't you think? The Hubble has also let us see, in far more detail than was possible before, the process of star formation itself -- think of the Eagle Nebula pictures, the so-called "pillars of creation." It's cool stuff.
Sorry if I'm ranting a bit here. My point is just this: if you want to rave about waste in our government, there are plenty of other places to look. Sure, the Hubble has had problems. Some of them have been stupid problems. But at maybe 6 billion dollars spent so far (the initial expenditure was quite a bit bigger than you quote, but I believe the shuttle flights cost less), it's been a bargain. And yes, I mean that seriously.:-)
First, realize what position the moon is in during _any_ full moon -- it's on the side of the Earth farthest from the Sun. (During a new moon, the moon is between the Earth and the Sun.) You don't get an eclipse every time there's a new (solar eclipse) or full (lunar eclipse) moon, because the moon's orbit is inclined a few degrees with respect to the ecliptic -- thus, things only line up a few times a year. During the lunar eclipse, the moon will fall completely in our shadow (the umbra) -- we'll block sunlight from striking directly on the moon. Sooooo, it would look like a solar eclipse from the moon -- the Sun would be occulted by a mysterious dark object (aka, the Earth) for a while. (Note that, more generally, an observer on the Moon would see a "new Earth" whenever we are seeing a full moon, and vice versa.)
A longer answer than you needed, really.:-) I don't know if anyone has ever been on the moon during an eclipse, but I doubt it for various reasons. Whatever.
"blood red" is sometimes an overstatement, but the phenomenon can still be pretty cool. the primary mechanism responsible for the coloring is actually (basically) the following: short wavelengths of light (aka, blue light) are scattered more effectively than long wavelengths (aka, red light). this, for instance, is why the sky is blue; it's why dust causes far more extinction in the visible regime than in the radio, etc. so sunlight hitting the earth has much of the blue component of the light scattered out. the point is that in an eclipse, the main reason the moon isn't totally dark is that some light from the _earth_ (rather than directly from the sun) illuminates it -- this light is mostly red (since the blue has been scattered out), so the moon appears red.
your bit about volcanic ash, though, is presumably partially correct -- within certain limits, presumably more dust means more scattering (and hence a stronger red color, since the red component isn't affected nearly as much).
I'm not sure how I feel about this petition. I think human exploration of Mars is a worthy goal -- this has been hashed out in other posts, so I won't go into that here. But I think it's naive to formulate a "petition" without a clear sense of why this is hard -- and no, it's not simply a matter of dumping more money into a Mars exploration program; there are real scientific issues to surmount before we can go safely. I've posted about this before, I think, but here goes.
Probably the biggest issue is shielding from radiation, etc. -- as many of you are probably aware, the Earth's magnetic field protects shuttle astronauts from lots of things; the only missions we've run which went outside that protective envelope were the Apollo ones, but those were relatively short (a few days). When you start talking about a 3-year mission to Mars, there becomes a very real chance that you'd get a solar flare, with unfortunate consequences for the astronauts. Shielding from these is, um, non-trivial. Also important are ionized heavy particles (stuff on the lower right-hand side of the periodic table) -- the interesting thing here is that, up to a fairly heavy amount of shielding, you actually just end up slowing down the bad guys, making them more dangerous to humans than they were before. (Left unmolested, they mostly pass through your body and probably knock off a few things on their way -- leaving you, for instance, with a higher chance of getting a tumor.)
Also important are physiological effects brought about by living in a micro-g environment. Most serious, perhaps, is the bone degradation that occurs over long periods of time, leaving bones more susceptible, for instance, to fracture. (This effect is bordering on okay for even the year-long missions we've had so far -- eg Mir -- but becomes an unacceptably big issue for longer exposures.) If you're interested in this stuff, check out the National Space Biomedical Research Institute.
The above issues have led people to look (seriously) at artificial-gravity environments (a la 2001). Doing these right turns out to be quite tricky -- it's not yet clear what values of spin rate, radius, duration, etc, are appropriate (and can be handled by your body). One big issue here is the Coriolis force, and the fact that your brain just doesn't expect it -- this becomes more of an issue in certain configurations. Another is that if you start talking about putting a really big spinning wheel in space (or something similar), you're getting into very heavy weight/size penalties for a given mission -- that is, clearly it's going to be harder to move a 1 km wheel to Mars. Having said all this, I should also say that it's not a dead field -- I think the problems will eventually be worked out; there are promising concept studies involving small-scale intermittent-use centrifuges, and others involving tether-based systems which expand once you get into space to provide the AG.
It's worth pointing out, finally, that some people have suggested that we can ignore some of the above physiological issues for a Mars trip -- so what if the astronauts come back with weak bones? They went to Mars! They expected risks. But the point is that subjecting astronauts to the risks mentioned above approaches the point of immorality.
I hope I haven't come across as being too pessimistic; I would like to see us go to Mars, and I think one day we will. But it'll be a while. And there are some very basic science issues (like "what is the effect of a 1km centrifuge on the human body") that need to be answered first -- signing this petition won't change that, and might even lead people to think this is a much simpler problem than it really is.
Sorry. But seriously, it's good stuff. The planet detection schemes are based on very basic physics which we understand very well. (As opposed to say, the Hubble constant you mention -- which is totally unrelated and is hard to measure for a lot of very good reasons.) I can't describe more than that without going into more physics than I really want to in a post -- check out Marcy's web page, I'm sure it has some relevant info.
(Um, one caveat: there are issues involving the inclination angle of the system, but those are systematic. This, incidentally, is why recent observations of an extrasolar planet transit were so cool.)
First off, I agree that we should try to reach them one day. But there are an awful lot of issues to deal with first -- I'm not gonna bite on the "FTL travel" issue, so let's talk about conventional propulsion schemes. No, scratch that. Let's talk about the issues specific to a manned flight. And let's make our problem easier -- a trip to Mars, for instance.
It is more or less correct to state that such a trip is within our technological grasp, human risk factors aside -- but the reasons we haven't done such a trip are more profound than simply budgetary or nuclear weapons treaty issues.
One interesting issue is that of radiation shielding -- as most of you are probably aware, the Earth's magnetic field shields people on, say, the Shuttle from lots of nasty critters. This wasn't the case for, say, the Apollo missions, but those were relatively short -- a few days; the odds that we would get a solar flare sometime during, say, a 3-year trip to Mars and back are pretty high. Shielding from highly-massive ionized particles (stuff in that lower right-hand of the periodic table) is also tricky -- the interesting thing is that up to a fairly large amount of shielding, you end up just "slowing them down" and making them more dangerous to humans than they were before. (If you don't shield, they by and large pass through and knock apart a few things in your body on the way -- giving you, for instance, a higher chance of getting a tumor.)
There are other severe physiological effects to consider, too. Probably the most serious is a degradation of bone material that occurs in a low-G environment -- this is acceptable, sort of, for even up to a year (cf the Mir missions), but a good chunk of the life sciences community would say the risk (of increased chance of fracture, permanent degradation, etc) is unacceptable when you're talking about a several-year mission. Soooo, people have looked (seriously) at artificial gravity schemes -- spinning people around to simulate gravity. These have problems too, though -- the Coriolis force makes your intuition wrong in many cases, plus putting a rotating ring in space (for instance) requires a pretty hefty penalty in terms of the amount of mass you're propelling. (I should mention that I think these problems will eventually be worked out -- tether schemes and small-scale intermittent-use centrifuges look promising. But it'll be a while.)
All of these are surmountable, probably. (And a substantial minority of people have said that the risk factors I mention above are acceptable for a Mars trip -- astronauts are risk-takers, the thinking goes.) My point is just that it's not as simple as it might seem. I haven't even touched on more basic physical principles that make accelerating anything (much less a manned spacecraft) up to some large fraction of the speed of light a very very difficult problem. But this post is more than long enough already.:-)
as forwarded by the AAS, embargoed until 11 am this morning. just in case you couldn't get enough from the article.:-) the last few paragraphs contain technical summaries of the planets' properties.
SANTA CRUZ, CA--The world's most prolific team of planet hunters has found six new planets orbiting nearby stars, bringing the total number of planets astronomers have detected outside the solar system to 28. The researchers also found evidence suggesting that two previously discovered planets have additional companions, said Steven Vogt, professor of astronomy and astrophysics at the University of California, Santa Cruz.
Vogt and his colleagues, Geoffrey Marcy of UC Berkeley, Paul Butler of the Department of Terrestrial Magnetism at the Carnegie Institution of Washington in Washington, D.C., and Kevin Apps of the University of Sussex, England, made the discoveries using the High Resolution Echelle Spectrograph (HIRES, designed and built by Vogt) on the Keck I Telescope in Hawaii. Their findings will be published in the Astrophysical Journal.
The researchers have been using the facilities at the W. M. Keck Observatory for the past three years to conduct a survey of 500 nearby sunlike stars in search of planets. The project is supported by the NASA Origins Program, which has provided both funding and telescope time, and by the National Science Foundation.
The six new planets increase by about 25 percent the number of known "extrasolar" planets, giving astronomers a substantial amount of additional information about planetary systems, Vogt said. One of the planets, HD 192263, was also recently detected by Nuno Santos and collaborators in Geneva, Switzerland, who reported it while Vogt and his colleagues were preparing their paper.
The new planets orbit stars that are similar in size, age, and brightness to the Sun and are at distances ranging from 65 to 192 light-years from Earth. The planets themselves range in mass from slightly smaller to several times larger than the planet Jupiter (0.8 to 6.5 times the mass of Jupiter). They are probably also similar to Jupiter in their compositions--basically giant balls of hydrogen and helium gas, Vogt said.
The presence of a planet around a star is indicated by a telltale wobble inthe motion of the star as a result of the gravitational force exerted by the orbiting planet. Vogt and his coworkers recently achieved independent confirmation of this method for detecting planets when they were able to predict and measure the dimming of a star as a planet passed in front of it.
The orbits of the new planets, like those of most of the extrasolar planets discovered so far, tend to be quite eccentric, tracing paths that are oval rather than circular. One of the planets, around a star called HD 222582, has the most wildly eccentric orbit yet known, carrying it from as close as 0.39 astronomical units (AU: the distance from Earth to the Sun) to as far as 2.31 AU from its parent star in the course of its 576-day orbit.
"It is beginning to look like neatly stacked, circular orbits such as we see in our own solar system are relatively rare," Vogt said.
Interestingly, five of the six planets are located within the so-called the motion of the star as a result of the gravitational force exerted by the orbiting planet. Vogt and his coworkers recently achieved independent confirmation of this method for detecting planets when they were able to predict and measure the dimming of a star as a planet passed in front of it.
The orbits of the new planets, like those of most of the extrasolar planets discovered so far, tend to be quite eccentric, tracing paths that are oval rather than circular. One of the planets, around a star called HD 222582, has the most wildly eccentric orbit yet known, carrying it from as close as 0.39 astronomical units (AU: the distance from Earth to the Sun) to as far as 2.31 AU from its parent star in the course of its 576-day orbit.
"It is beginning to look like neatly stacked, circular orbits such as we see in our own solar system are relatively rare," Vogt said.
Interestingly, five of the six planets are located within the so-called "habitable zones" of their stars. This is the region where temperatures would allow water to exist in liquid form. Most of the extrasolar planets the researchers have studied have turned out to be outside the habitable zone, either too close to their star or too far away, and therefore too hot or too cold, Vogt said.
"These planets are at just the right distance, with temperatures in one case around 108 degrees Fahrenheit--like a hot day in Sacramento," he said.
Planetary systems with Jupiter-sized planets in oval-shaped orbits are not expected to harbor Earthlike planets, Vogt added. In fact, if an Earthlike planet were put into such a system, it would be quickly ejected by the gravitational influence of the Jupiter-mass planet. Vogt noted, however, that if these Jupiter-sized planets are similar to those in our own solar system, they probably have numerous moons associated with them.
"For a planet in the habitable zone of its star, such moons offer the possibility of liquid water and the eventual emergence of life," he said.
In addition to the discovery of six new planets, the researchers gathered new data on four previously known planets. Two of them, around the stars HD 217107 and HD 187123, showed long-term trends in their orbits indicating the presence of an additional companion. These companions, which may be planets or larger objects (e.g., brown dwarfs), appear to be orbiting their host stars in a long period, taking at least two to three years to complete an orbit, Vogt said. These findings are significant because previously only one other system of multiple planets, around the star Upsilon Andromedae, had been identified.
"It will take years of additional observations to work out the masses and orbits of these companions, but the evidence suggests there are a fair number of multiple planet systems out there," Vogt said.
Specific details about the new planets and their host stars are given below: HD 10697 is a G5IV star, slightly cooler and a bit larger than the Sun. It lies 106 light-years away in the constellation Pisces. Its planet has a minimum mass of 6.35 Jupiter masses and a 1,072-day orbit. The radius of this orbit is about 2.13 AU, but the orbit is somewhat eccentric, so the planet's distance from its star ranges from 1.87 AU to 2.39 AU. At its average orbital distance, it lies just at the outside edge of the habitable zone of its star, and is expected to have an equilibrium temperature (due to energy received from its parent star) of about 15 degrees F.
HD 37124 is a G4V star, slightly cooler than the Sun. It lies 108 light-years away in the constellation Taurus. Its planet has a minimum mass of 1.04 Jupiter masses and a 155.7-day orbit. This orbit is also quite eccentric. At its average orbital distance of 0.55 AU, it sits just within the inner edge of the habitable zone of its star, and is expected to have an equilibrium temperature of about 130 degrees F. This is the lowest metallicity star known to have a planet.
HD 134987 is a G5V star, 83 light-years away in the constellation Libra.Its planet orbits in a 260-day eccentric orbit. This planet has a minimum mass of 1.58 Jupiter masses. At its average orbital distance of 0.81 AU, its expected equilibrium temperature is a balmy 108 degrees F. It lies well within the habitable zone of its star.
HD 177830 is a K2IV star, about 1,000 degrees Kelvin cooler than the Sun, lying about 192 light-years away in the constellation Vulpecula. It harbors a 1.22 Jupiter mass planet in a 392-day, highly eccentric orbit. This orbit carries the planet from as close as 0.63 AU from its star to as far as 1.57 AU. At its mean orbital distance of 1.10 AU its expected temperature is about 192 degrees F. The planet is probably within the habitable zone of its star.
HD 192263 is a K2V star lying 65 light-years away in the constellation Aquila. A planet around this star was first reported by Nuno Santos, a Portuguese graduate student at the University of Geneva. Vogt's team has obtained essentially the same results as Santos: a 0.78 Jupiter mass planet orbiting in a 24.36-day orbit. This orbit has a radius of only 0.15 AU, with little or no eccentricity. It orbits well outside the habitable zone of its star.
HD 222582, a G3V star, is a near solar twin, 137 light-years away in the constellation Aquarius. Its planet orbits in a widly eccentric 576-day orbit, which carries the planet from 0.39 AU to 2.31 AU from the parent star in the course of its oval orbit. This is the most eccentric extrasolar planet orbit yet known. The planet's expected temperature is about -38 degrees F. Its mean orbital distance places it squarely in the habitable zone of its star.
Further information about the planet search is available on the Web at http://www.physics.sfsu.edu/~gmarcy/planetsearch/p lanetsearch.html. Information about the NASA Origins Program can be found at http://origins.jpl.nasa.gov/ and about NSF's astronomy program at http://www.nsf.gov/mps/ast/start.htm.
Yep, sure is. I can comment a little on this, though I should mention that I don't know much about attempts to tie string theory into this stuff.
One plausible way of thinking about the initial inflation comes about if (as this work and others have suggested) the Universe has a non-zero cosmological constant. The profound implication is then that vacuum has a non-zero energy -- people have tried to show that (look for "Cassimir effect" in your favorite search engine), and perhaps succeeded, but the measurements are a little iffy (at least to my knowledge). Anyway, point is that things like to go to their state of lowest energy -- so you can imagine a situation where the initial inflation was caused by a transition to a lower-energy state (our own). (And hey, if you want to keep your kids up late at night with some sci-babble, here's one for you: if we really have a non-zero cosmological constant, then you can argue that the universe could someday undergo a transition to another state -- which would pretty much suck for us.)
Err, I should clarify. The idea of "big bang as transition between energy states" is NOT dependent on the existence of a non-zero lambda. Some of the implications for what we should find, and for what might happen next, are. Okay, this is quickly surpassing my desire/ability to explain it succintly, so I'm going to quit. Hope that at least provided you "food for thought."
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So let our students be mediocre at long division. I couldn't care less. (When I need to do a complicated long division problem, I reach for the calculator -- why waste my time doing otherwise?) As long as they have been exposed to the mechanics, and (more fundamentally) how those mechanics can be applied in math and in life, who cares?
There are obvious caveats to my comments above, and this is why I partially agree with you -- teachers do need to make sure that students receive enough grounding in simple technique that they're not dependent on calculators for everything; for trivial calculations, nothing beats pen and paper. I think one ultimate goal is for the students to be able to solve any problem in the manner that is most appropriate -- clearly sometimes that will be in their heads, and just as clearly, sometimes a calculator is the way to go. Coupled with this, as I said above, is the goal of teaching the students to think in a mathematical way. Calculators obviously aren't a catch-all for accomplishing both goals, but I see no reason why they can't help you along the way.
- the Hubble expansion: when we look at distant galaxies, they are all moving away from us with a speed that is directly proportional to their distance.
- the existence and features of the Cosmic Microwave Background: when you look in the microwave part of the spectrum, you see a dull glow in every direction; that glow has the spectrum of a perfect blackbody at 2.7 K. small anisotropies (deviations from the mean temperature) do exist, but these are actually required by the theory -- and in fact many of their characteristics (like the angular scale at which they occur) is beautifully predicted by inflation. see the recent BOOMERanG results (there's a
/. post about them) for more. - the abundances of light elements: this is a bit complicated, but basically certain elements were formed (primarily or exclusively) during the very early stages of the Universe. The BB theory predicts certain abundance ratios for these elements (which do depend on the matter density of the Universe, for obvious reasons) which are well borne out by observation.
Taken together, these constitute an extremely strong theory. I could go on and on about this -- there are literally hundreds of distinct problems in which inflation has been shown to provide a prediction which is compatible with observations. Tomorrow, someone may find some linchpin observation that brings inflation crashing down -- any scientist accepts that as a possibility for any theory. But as confirmation of the theory grows, as more and more observations back it up, as it is more fully developed and refined and made beautiful, we start to have a lot of confidence that such a linchpin will never be found.I'd also point out that you seem to paint a dichotomy (creation vs. BB) which does not necessarily have to exist. The existence of a set of natural laws which govern the Universe does not preclude the existence of a Creator -- though this is touching on philosophical issues too rich for a few pithy comments here. (True, literal 7-day creation is pretty much out of line with BB/inflation.)I know many scientists who are deeply religious -- but such religiosity is ultimately a matter of faith. Sure, that presents, err, issues for them: there are some obvious conflicts between a worldview which says the Universe began about 13 billion years ago and one which says 4,000; but the point is that if you are REALLY religious and also REALLY care about the world around you (meaning you are unwilling to simply turn a blind eye to the overwhelming amount of evidence in favor of, say, inflation), you MUST deal with those issues rather than simply ignore them; your faith is an awfully weak one if it can't stand to do so.
Remember that we already "know" (or have strong constraints) on the overall baryon density from Big Bang nucleosynthesis (from measurements of the ratios of certain light elements). That's how we can make a statement like "a big fraction of the baryons in the universe are in this gas."
If you're really interested in this stuff, check out the paper "Where are the baryons?" by Cen and Ostriker -- sorry I can't give you a better reference, but hunt on astro-ph or the Harvard abstract service and you'll find it.
The way many of these groups arrive at their estimate that the universe is "flat" is basically from such power spectrum measurements. Basically, the first peak of that spectrum (at an angular scale of about l=200) implies (to within reasonably small error bars) that we live in a flat universe. (More rigorously, it implies that Omega_k, an effective density term arising from the curvature, is equal to zero.)
The "power spectrum" does tell you lots of other things, true. But so does the mere fact that the CMB spectrum itself is Planckian -- it's possible to show that energy injection by unknown particle species at early times would alter the spectrum that we see today. It's also possible to constrain lots of other cosmological things, like the redshift at which reionization occurs, by observing the spectrum. This is getting more technical than is really appropriate, so I'll stop -- point is, though, that the result here (and from other similar papers) is actually pretty significant. Doesn't mean there aren't other significant papers to be written. :-)
This should be moderated up, unlike many other posts that have appeared on this subject. Maybe we should introduce a "blatantly wrong" moderation modifier. :-)
BTW, people may not realize just how long the life cycle on this sort of project is ... for instance, the first meeting regarding the *Next Generation* Space Telescope (ie, the successor to HST) was held in, I think, 1989. NGST won't go up for another, oh, seven to ten years. :-)
I guess my point is this: sure, there are areas Hubble will never be able to probe, questions it will never be able to answer, pictures it will never be able to take. And other satellites have been designed to probe those areas, answer those questions, take those pictures. But Hubble has done what it was *designed* to do, extremely well. We'll all be sorry when it's gone. ;-)
Just my 2 cents.
So I don't know. Within a certain number and class of students, I don't think cheating is a big enough concern to justify elaborate mechanisms to prevent it. To be fair, I am currently a graduate student at another, larger university (which shall remain nameless) -- and here, the custom is to monitor like a hawk whenever we give exams, require students to record their seat numbers, use multiple versions of exams, etc. This is a little disturbing to me, but the students seem to justify the approach -- I've caught more than one blatantly copying off another student, for instance. Where will this online university fall between these schemes? I dunno -- but I feel fairly certain that if you only impose mechanisms to detect/prevent cheating, without convincing students that it's really in their best interests not to cheat, someone will eventually figure out a way to circumvent those mechanisms.
I'd just like to point out that your bit about "$10,000 should be within your means if you are a high technology professional" is crap. "High-technology professional," whatever the hell that is, sure. Physicist -- no way in hell. :-) (I don't know any physicists who would be willing to wager $10k on anything, much less something like this. Notice that when Kip Thorne and Steven Hawking made their famous series of wagers, they were for things like a subscription to Playboy instead.)
And at the risk of getting involved in a flamewar not of my own design: I think defending your ideas by offering a ridiculous wager is not the best way to convince any members of the scientific community of the veracity of your claims. What fperez says is wrong? Fine, tell me how. Your assertion is intriguing, but a follow-up post saying, "my collaborators are so-and-so, we've submitted to PhysRev A, etc." would've been (IMHO) more reasonable than this.
No offense, I hope. :-)
As you mention, the "most distant" things that have been observed (to my knowledge) are so-called "blue drop-out" galaxies. (You're probably aware of this, but: You take an image in several wavelength bands, and find some galaxy that is definitely present in the longer-wavelength ones but gone in the short-wavelength images. By figuring out the point where the galaxy disappears, you can in principle determine its redshift. Less precise -- and also much less time-consuming -- than spectroscopic redshifts, for obvious reasons. :-))
You can be a little more precise than just saying it's a relic of the Big Bang, though. The CMB is basically the remnant afterglow of the moment when the Universe became transparent to its own radiation -- before that, for various reasons, photons couldn't get very far. There's a lot more going on here than I really want to go into, but a couple important points: the CMB is a very important reason why we like the Big Bang theory. It has the spectrum of a perfect blackbody (to within one part in 10^5 or so) at 3 K (and yes, that apparent temp. is a result of the redshift); that fact alone imposes pretty fundamental limitations on what could've happened in the early stages of the Universe. (It turns out, for instance, that you can't have had energy injection by spooky other particles, because we would see a non-Planckian CMB.) Furthermore, one particular property of the CMB -- that it looks the same wherever we look (once you have accounted for the motion of our galaxy relative to it) -- is one reason we like inflation, which suggests that one very tiny region of the initial Universe underwent a period of unimaginably speedy expansion. (Again, this can get arbitrarily complicated. But the point is that in a simple uniform expansion, the stuff to our left and the stuff to our right would never have had the chance to equilibrate with each other; hence, they should look different. Inflation "solves" this by requiring that everything we see came from one very very tiny region in the initial Universe.)
It's a good bet that the portion of the American public that gets their political news primarily from online sources -- and more specifically, the portion that is actually likely to look at any candidate's website -- is not a completely representative cross-section of America. Does this affect, or can you imagine it affecting in the future, the messages you display on your website? Clearly the ideas you talk about on TV and the ideas you talk about on your site have to be basically the same, but do you make a conscious effort to tailor the way you convey those ideas to the population you're sampling via each medium? If not, can you imagine situations in which it might be greatly to your advantage to do so? Or severely detrimental?
The tether approach has been thought about at great length and if we decide to go with a full-time centrifuge, that's certainly the way to do it. I wish I could direct you to a good page on why even this is not ready for prime time, but I can't. Briefly, I seem to recall that the problems with any large-scale centrifuge are that people just tend to be screwed up by the Coriolis effects -- I remember watching a great video of someone trying to throw a ball around in a centrifuge, and you'd be surprised how messed up they were. (To be fair: a lot of people think that you would eventually adjust to these effects.) Would that it were as easy as the scenes in 2001. The only thing a tether system saves you is the additional weight you would otherwise have to be propelling in order to get the centrifuge effect. (Ie, it's a lot easier to lift a couple pods and a tether than it is to lift a giant ring.) More promising, IMHO, are short-term personal centrifuges -- it's looking as though you don't need anything like 24-hour exposure to gravity to prevent most of the ill effects of microgravity.
As for the radiation: I actually don't recall Zubrin's argument here, so maybe I'm giving him less credit than he deserves. But the real killers in space are the massive particles down in that lower right hand side of the periodic table -- these are the ones I was referring to earlier when I said that we don't have particularly effective shielding. Also: background exposure levels are not that high, true, but as you talk about multiple-year missions, the chance of getting an anomalous exposure (ie, from a solar flare) becomes unacceptably high.
There are plenty of people who believe these risks are acceptable. After all, they argue, these guys are astronauts! They're used to risks. But I don't think we'll do it (aka, I don't think NASA or any other responsible agency will fund it) until we can deal with these things much better than we do now.
Lest I seem too pessimistic, let me say this: I think going to, say, Mars is a worthy goal. I haven't thought that much about establishing an outpost there (which has all sorts of other issues associated with it), but that would be pretty neat too. :-) BUT you are shooting yourself in the foot by telling people it's an easy problem -- eventually, they might believe you. I think all the issues I mentioned above will be solved. (There is promising research in short-duration centrifuges, and some less-promising but still cool work in tether-based large centrifuges. But all of these have a lot of testing to go through before they'll be ready to rock.) But it'll be a while, and people should know that.
To get a color picture, you basically pick a color to go along with each filter image -- these are pretty sensible (usually), but there's still a bit of leeway. Conventional choices might be, for instance, H-alpha (H transition, at 6563 A) as red , H-beta (4861) as blue, and maybe [OIII] 5007 as green. But depending on what you wanted to show, you might choose different color-wavelength correspondences.
Also, most of the images you see in PR releases and such have probably gone through additional processes to make them look nice -- ie gaussian smoothing filters, hand-removal of pesky lingering cosmic rays, subtle implantation of subliminal messages ("hubble good. nasa good."), whatever. It's all in good fun.
There are a few other projects that will be around after Hubble (though some will go up before HST comes down) -- the Next Generation Space Telescope is the "biggest," I guess. (Other recent/upcoming telescopes, designed to look at different parts of the spectrum, include FUSE, XMM, Chandra/AXAF, etc.) One interesting bit is that there isn't currently a telescope in the works that will fully cover the HST's observation range -- that is, there are parts of the spectrum that are going to get the big 'ole shaft when HST comes down. But enough of this.
Sorry if I'm ranting a bit here. My point is just this: if you want to rave about waste in our government, there are plenty of other places to look. Sure, the Hubble has had problems. Some of them have been stupid problems. But at maybe 6 billion dollars spent so far (the initial expenditure was quite a bit bigger than you quote, but I believe the shuttle flights cost less), it's been a bargain. And yes, I mean that seriously. :-)
A longer answer than you needed, really. :-) I don't know if anyone has ever been on the moon during an eclipse, but I doubt it for various reasons. Whatever.
your bit about volcanic ash, though, is presumably partially correct -- within certain limits, presumably more dust means more scattering (and hence a stronger red color, since the red component isn't affected nearly as much).
Probably the biggest issue is shielding from radiation, etc. -- as many of you are probably aware, the Earth's magnetic field protects shuttle astronauts from lots of things; the only missions we've run which went outside that protective envelope were the Apollo ones, but those were relatively short (a few days). When you start talking about a 3-year mission to Mars, there becomes a very real chance that you'd get a solar flare, with unfortunate consequences for the astronauts. Shielding from these is, um, non-trivial. Also important are ionized heavy particles (stuff on the lower right-hand side of the periodic table) -- the interesting thing here is that, up to a fairly heavy amount of shielding, you actually just end up slowing down the bad guys, making them more dangerous to humans than they were before. (Left unmolested, they mostly pass through your body and probably knock off a few things on their way -- leaving you, for instance, with a higher chance of getting a tumor.)
Also important are physiological effects brought about by living in a micro-g environment. Most serious, perhaps, is the bone degradation that occurs over long periods of time, leaving bones more susceptible, for instance, to fracture. (This effect is bordering on okay for even the year-long missions we've had so far -- eg Mir -- but becomes an unacceptably big issue for longer exposures.) If you're interested in this stuff, check out the National Space Biomedical Research Institute.
The above issues have led people to look (seriously) at artificial-gravity environments (a la 2001). Doing these right turns out to be quite tricky -- it's not yet clear what values of spin rate, radius, duration, etc, are appropriate (and can be handled by your body). One big issue here is the Coriolis force, and the fact that your brain just doesn't expect it -- this becomes more of an issue in certain configurations. Another is that if you start talking about putting a really big spinning wheel in space (or something similar), you're getting into very heavy weight/size penalties for a given mission -- that is, clearly it's going to be harder to move a 1 km wheel to Mars. Having said all this, I should also say that it's not a dead field -- I think the problems will eventually be worked out; there are promising concept studies involving small-scale intermittent-use centrifuges, and others involving tether-based systems which expand once you get into space to provide the AG.
It's worth pointing out, finally, that some people have suggested that we can ignore some of the above physiological issues for a Mars trip -- so what if the astronauts come back with weak bones? They went to Mars! They expected risks. But the point is that subjecting astronauts to the risks mentioned above approaches the point of immorality.
I hope I haven't come across as being too pessimistic; I would like to see us go to Mars, and I think one day we will. But it'll be a while. And there are some very basic science issues (like "what is the effect of a 1km centrifuge on the human body") that need to be answered first -- signing this petition won't change that, and might even lead people to think this is a much simpler problem than it really is.
Sorry. But seriously, it's good stuff. The planet detection schemes are based on very basic physics which we understand very well. (As opposed to say, the Hubble constant you mention -- which is totally unrelated and is hard to measure for a lot of very good reasons.) I can't describe more than that without going into more physics than I really want to in a post -- check out Marcy's web page, I'm sure it has some relevant info.
(Um, one caveat: there are issues involving the inclination angle of the system, but those are systematic. This, incidentally, is why recent observations of an extrasolar planet transit were so cool.)
It is more or less correct to state that such a trip is within our technological grasp, human risk factors aside -- but the reasons we haven't done such a trip are more profound than simply budgetary or nuclear weapons treaty issues.
One interesting issue is that of radiation shielding -- as most of you are probably aware, the Earth's magnetic field shields people on, say, the Shuttle from lots of nasty critters. This wasn't the case for, say, the Apollo missions, but those were relatively short -- a few days; the odds that we would get a solar flare sometime during, say, a 3-year trip to Mars and back are pretty high. Shielding from highly-massive ionized particles (stuff in that lower right-hand of the periodic table) is also tricky -- the interesting thing is that up to a fairly large amount of shielding, you end up just "slowing them down" and making them more dangerous to humans than they were before. (If you don't shield, they by and large pass through and knock apart a few things in your body on the way -- giving you, for instance, a higher chance of getting a tumor.)
There are other severe physiological effects to consider, too. Probably the most serious is a degradation of bone material that occurs in a low-G environment -- this is acceptable, sort of, for even up to a year (cf the Mir missions), but a good chunk of the life sciences community would say the risk (of increased chance of fracture, permanent degradation, etc) is unacceptable when you're talking about a several-year mission. Soooo, people have looked (seriously) at artificial gravity schemes -- spinning people around to simulate gravity. These have problems too, though -- the Coriolis force makes your intuition wrong in many cases, plus putting a rotating ring in space (for instance) requires a pretty hefty penalty in terms of the amount of mass you're propelling. (I should mention that I think these problems will eventually be worked out -- tether schemes and small-scale intermittent-use centrifuges look promising. But it'll be a while.)
All of these are surmountable, probably. (And a substantial minority of people have said that the risk factors I mention above are acceptable for a Mars trip -- astronauts are risk-takers, the thinking goes.) My point is just that it's not as simple as it might seem. I haven't even touched on more basic physical principles that make accelerating anything (much less a manned spacecraft) up to some large fraction of the speed of light a very very difficult problem. But this post is more than long enough already. :-)
SANTA CRUZ, CA--The world's most prolific team of planet hunters has found six new planets orbiting nearby stars, bringing the total number of planets astronomers have detected outside the solar system to 28. The researchers also found evidence suggesting that two previously discovered planets have additional companions, said Steven Vogt, professor of astronomy and astrophysics at the University of California, Santa Cruz.
Vogt and his colleagues, Geoffrey Marcy of UC Berkeley, Paul Butler of the Department of Terrestrial Magnetism at the Carnegie Institution of Washington in Washington, D.C., and Kevin Apps of the University of Sussex, England, made the discoveries using the High Resolution Echelle Spectrograph (HIRES, designed and built by Vogt) on the Keck I Telescope in Hawaii. Their findings will be published in the Astrophysical Journal.
The researchers have been using the facilities at the W. M. Keck Observatory for the past three years to conduct a survey of 500 nearby sunlike stars in search of planets. The project is supported by the NASA Origins Program, which has provided both funding and telescope time, and by the National Science Foundation.
The six new planets increase by about 25 percent the number of known "extrasolar" planets, giving astronomers a substantial amount of additional information about planetary systems, Vogt said. One of the planets, HD 192263, was also recently detected by Nuno Santos and collaborators in Geneva, Switzerland, who reported it while Vogt and his colleagues were preparing their paper.
The new planets orbit stars that are similar in size, age, and brightness to the Sun and are at distances ranging from 65 to 192 light-years from Earth. The planets themselves range in mass from slightly smaller to several times larger than the planet Jupiter (0.8 to 6.5 times the mass of Jupiter). They are probably also similar to Jupiter in their compositions--basically giant balls of hydrogen and helium gas, Vogt said.
The presence of a planet around a star is indicated by a telltale wobble inthe motion of the star as a result of the gravitational force exerted by the orbiting planet. Vogt and his coworkers recently achieved independent confirmation of this method for detecting planets when they were able to predict and measure the dimming of a star as a planet passed in front of it.
The orbits of the new planets, like those of most of the extrasolar planets discovered so far, tend to be quite eccentric, tracing paths that are oval rather than circular. One of the planets, around a star called HD 222582, has the most wildly eccentric orbit yet known, carrying it from as close as 0.39 astronomical units (AU: the distance from Earth to the Sun) to as far as 2.31 AU from its parent star in the course of its 576-day orbit.
"It is beginning to look like neatly stacked, circular orbits such as we see in our own solar system are relatively rare," Vogt said.
Interestingly, five of the six planets are located within the so-called the motion of the star as a result of the gravitational force exerted by the orbiting planet. Vogt and his coworkers recently achieved independent confirmation of this method for detecting planets when they were able to predict and measure the dimming of a star as a planet passed in front of it.
The orbits of the new planets, like those of most of the extrasolar planets discovered so far, tend to be quite eccentric, tracing paths that are oval rather than circular. One of the planets, around a star called HD 222582, has the most wildly eccentric orbit yet known, carrying it from as close as 0.39 astronomical units (AU: the distance from Earth to the Sun) to as far as 2.31 AU from its parent star in the course of its 576-day orbit.
"It is beginning to look like neatly stacked, circular orbits such as we see in our own solar system are relatively rare," Vogt said.
Interestingly, five of the six planets are located within the so-called "habitable zones" of their stars. This is the region where temperatures would allow water to exist in liquid form. Most of the extrasolar planets the researchers have studied have turned out to be outside the habitable zone, either too close to their star or too far away, and therefore too hot or too cold, Vogt said.
"These planets are at just the right distance, with temperatures in one case around 108 degrees Fahrenheit--like a hot day in Sacramento," he said.
Planetary systems with Jupiter-sized planets in oval-shaped orbits are not expected to harbor Earthlike planets, Vogt added. In fact, if an Earthlike planet were put into such a system, it would be quickly ejected by the gravitational influence of the Jupiter-mass planet. Vogt noted, however, that if these Jupiter-sized planets are similar to those in our own solar system, they probably have numerous moons associated with them.
"For a planet in the habitable zone of its star, such moons offer the possibility of liquid water and the eventual emergence of life," he said.
In addition to the discovery of six new planets, the researchers gathered new data on four previously known planets. Two of them, around the stars HD 217107 and HD 187123, showed long-term trends in their orbits indicating the presence of an additional companion. These companions, which may be planets or larger objects (e.g., brown dwarfs), appear to be orbiting their host stars in a long period, taking at least two to three years to complete an orbit, Vogt said. These findings are significant because previously only one other system of multiple planets, around the star Upsilon Andromedae, had been identified.
"It will take years of additional observations to work out the masses and orbits of these companions, but the evidence suggests there are a fair number of multiple planet systems out there," Vogt said.
Specific details about the new planets and their host stars are given below: HD 10697 is a G5IV star, slightly cooler and a bit larger than the Sun. It lies 106 light-years away in the constellation Pisces. Its planet has a minimum mass of 6.35 Jupiter masses and a 1,072-day orbit. The radius of this orbit is about 2.13 AU, but the orbit is somewhat eccentric, so the planet's distance from its star ranges from 1.87 AU to 2.39 AU. At its average orbital distance, it lies just at the outside edge of the habitable zone of its star, and is expected to have an equilibrium temperature (due to energy received from its parent star) of about 15 degrees F.
HD 37124 is a G4V star, slightly cooler than the Sun. It lies 108 light-years away in the constellation Taurus. Its planet has a minimum mass of 1.04 Jupiter masses and a 155.7-day orbit. This orbit is also quite eccentric. At its average orbital distance of 0.55 AU, it sits just within the inner edge of the habitable zone of its star, and is expected to have an equilibrium temperature of about 130 degrees F. This is the lowest metallicity star known to have a planet.
HD 134987 is a G5V star, 83 light-years away in the constellation Libra.Its planet orbits in a 260-day eccentric orbit. This planet has a minimum mass of 1.58 Jupiter masses. At its average orbital distance of 0.81 AU, its expected equilibrium temperature is a balmy 108 degrees F. It lies well within the habitable zone of its star.
HD 177830 is a K2IV star, about 1,000 degrees Kelvin cooler than the Sun, lying about 192 light-years away in the constellation Vulpecula. It harbors a 1.22 Jupiter mass planet in a 392-day, highly eccentric orbit. This orbit carries the planet from as close as 0.63 AU from its star to as far as 1.57 AU. At its mean orbital distance of 1.10 AU its expected temperature is about 192 degrees F. The planet is probably within the habitable zone of its star.
HD 192263 is a K2V star lying 65 light-years away in the constellation Aquila. A planet around this star was first reported by Nuno Santos, a Portuguese graduate student at the University of Geneva. Vogt's team has obtained essentially the same results as Santos: a 0.78 Jupiter mass planet orbiting in a 24.36-day orbit. This orbit has a radius of only 0.15 AU, with little or no eccentricity. It orbits well outside the habitable zone of its star.
HD 222582, a G3V star, is a near solar twin, 137 light-years away in the constellation Aquarius. Its planet orbits in a widly eccentric 576-day orbit, which carries the planet from 0.39 AU to 2.31 AU from the parent star in the course of its oval orbit. This is the most eccentric extrasolar planet orbit yet known. The planet's expected temperature is about -38 degrees F. Its mean orbital distance places it squarely in the habitable zone of its star.
Further information about the planet search is available on the Web at http://www.physics.sfsu.edu/~gmarcy/planetsearch/p lanetsearch.html. Information about the NASA Origins Program can be found at http://origins.jpl.nasa.gov/ and about NSF's astronomy program at http://www.nsf.gov/mps/ast/start.htm.
One plausible way of thinking about the initial inflation comes about if (as this work and others have suggested) the Universe has a non-zero cosmological constant. The profound implication is then that vacuum has a non-zero energy -- people have tried to show that (look for "Cassimir effect" in your favorite search engine), and perhaps succeeded, but the measurements are a little iffy (at least to my knowledge). Anyway, point is that things like to go to their state of lowest energy -- so you can imagine a situation where the initial inflation was caused by a transition to a lower-energy state (our own). (And hey, if you want to keep your kids up late at night with some sci-babble, here's one for you: if we really have a non-zero cosmological constant, then you can argue that the universe could someday undergo a transition to another state -- which would pretty much suck for us.)
Err, I should clarify. The idea of "big bang as transition between energy states" is NOT dependent on the existence of a non-zero lambda. Some of the implications for what we should find, and for what might happen next, are. Okay, this is quickly surpassing my desire/ability to explain it succintly, so I'm going to quit. Hope that at least provided you "food for thought."