Spacecraft velocity discrepancies show there are still fundamental things we don’t know

Friday, February 29th, 2008

Ten years ago, scientists observed a discrepancy in the velocity of the space probe Pioneer 10. It was going slightly faster than anyone could explain. Every possible physical effect we can think of, including gravitational influence from all bodies in the solar system, the effect of solar wind, possible magnetic fields, possible outgassing of fuel vapors from the spacecraft itself, etc., have been taken into account and considered, and yet we still cannot explain Pioneer 10′s unexpected velocity. Even the known unknown (to borrow Rumsfeld’s terminology) of dark matter, if it exists, cannot explain this acceleration. And now, scientists have expanded the search for discrepancies to the rest of our spacecraft, and finding them in every single one.

Are you spooked? Because I am. A velocity discrepancy of 13 mm/sec for the NEAR spacecraft doesn’t sound like much, but compound that over the course of many years and NEAR’s predicted orbit and where it will actually be will diverge (luckily it has thrusters on it). But that’s not really the significant part of this. The precision of the test is 0.1 mm/sec, so we the discrepancy is significant, and because it’s happening to all of our spacecraft, we know it is repeatable. There is some fundamental aspect of this universe that we do not understand. It’s simultaneously spooky and exciting. With Newton’s theory of gravity, we thought we had the macro scale all figured out until we began finding discrepancies in our observations (particularly with the orbit of Mercury). Then with Einstein’s theory of relativity, we again thought we had everything all figured out.

Now there are more experimental discrepancies.

Sure, it’s possible, maybe even likely, that the discrepancies we observe in our spacecraft are caused by phenomena we already know about, but do not understand fully (such as larger variations in the solar wind than expected). The discrepancy’s effect, weakest along the ecliptic (the plane connecting the Sun’s equator and the orbits of the planets), and strongest for spacecraft in highly inclined orbits, gives us some intriguing clues. But what if we exhaust all of the “normal” possibilities? What if we get right down to it and end up having to revise relativity itself in order to explain these new findings? Maybe gravity doesn’t work exactly how we thought over large distances? The possibilities are frightening and amazing. I’m excited by the possibility of seeing the theory of gravity revised again in my lifetime.

And Happy Leap Day everyone. How fun to learn this news on the weirdest of days.

You’ve got the Devil in ya

Tuesday, February 12th, 2008

Does anyone else find it absurd that exorcism is making a comeback? Is there anything more useless? Humankind realized centuries ago that science and medicine could explain (and cure) more ailments than superstitious religious voodoo ever dreamed of. So why do we still have idiots practicing exorcism? And why do we still have idiots who go to get exorcised? That’s the problem with religion. Its emphasis on faith over reason and empiricism leads to ludicrous, lala-land thinking.

The most dangerous part of a resurgence of exorcism is all of the real treatment that sufferers won’t be getting because they’re wasting time narfing off with an exorcist. Is someone suffering from epilepsy, depression, or a mental illness? They don’t need medicine! What they need is to be told that the devil is inhabiting them, and for a “paltry” fee, he can be driven out! That’ll do the trick! And even better, think of all the children who will have the fear of God put into them when they’re told their body is inhabited by the beast himself! That won’t traumatize them in the least.

Exorcism is little different from Scientology in this regard. Maybe once Anonymous is done with Scientology, they can take on the sham of exorcism next? I’ll be cheering them on!

To your mind, tools are a literal part of the body

Wednesday, January 30th, 2008

A new study casts light on the (nearly) unique ability of higher order primates to use tools. It turns out it’s quite the elegant mental hack. So far as your mind is concerned, any tools you are using are literally part of your body. Scientists confirmed this by conducting an experiment on monkeys. They observed that the same group of neurons fired off in the same order when monkeys picked up a piece of food, no matter whether they used their hands, pliers, or reverse pliers that required opening the hands to close the pliers’ tip. The firing of the neurons thus had nothing to do with the movements of the fingers themselves when a tool was used, but rather, corresponded to the movement exhibited by the grasping end of the tool. It’s quite an amazing, revolutionary find, and as these things usually go, it makes perfect sense in hindsight.

Imagine swinging a baseball bat. You aren’t concentrated on your hands; once they are grasping the bat you don’t give them a second thought. No, you are concentrated on the sweet spot on the bat. It becomes your fingers by proxy, and the motion of swinging a bat is really just about extending your “hands” to meet an incoming object. That’s why we are so good at hitting baseballs coming in at even 100 mph. It wouldn’t work at all if you had to concentrate on the complex kinematic interactions governing how movements of your hands are translated into movement of the end of the bat. Thankfully, evolution has provided us with such an elegant hack that makes it all work — and a hack that is undoubtedly responsible for modern civilization, as well.

When I read this article I immediately started thinking about videogames. There’s a break-in period when confronted with a novel controller or control method before its use becomes natural. Before that happens, you’re still consciously thinking about pressing every button, rather than focusing on the effects those actions will have within the game. For instance, I played Guitar Hero for the first time over the New Year’s holiday. At the beginning I was playing easy level songs with only a modicum of success. But as I grew more familiar with the controller, as it became an extension of my body, I got better with it, and by the end, I was tackling medium level difficulty songs. Give me a few more hours with it and I’d be on hard.

My most familiar controller format has to be the standard for PC first person shooters: W,A,S,D (or rarely E,S,D,F) for movement and the mouse for looking and aiming. I’ve been playing games using that for so long it has become second nature to me. I’m not even focusing on my fingers at all. When I’m moving around in Team Fortress 2 I frequently detect spies trying to backstab me simply because I run into them. There’s no lag time at all between trying to move backwards and realizing I’m running into something, then within a fraction of a second I’m spinning wildly in place and firing my weapon before I even see the enemy. And the virtual gun on-screen has become an extension of my hand. That’s the amazing part of all this that I wish the experiment had covered. Not only does the tool become a part of your body as far as the mind is concerned, the tool doesn’t even have to be real at all. It can be entirely virtual. And why shouldn’t it? The cognitive hack thankfully doesn’t discriminate, so it will continue serving us well for decades to come as virtual reality becomes an ever larger part of our life.

Shattering the inevitability myth of senescence

Sunday, January 20th, 2008

Ask yourself this: why do you think of senescence (the process of deterioration resulting in becoming elderly, and eventually, dying of it) as inevitable? I ask why, not if, because universally nearly everyone seems to have simply accepted it without question. Yes, it may be true that death due to old age has been inevitable for all of human history, but then again, until very recently, so was the possibility of death due to other sorts of diseases (polio, the bubonic plague, etc.). Yet science has continued marching on at an exponential pace, achieving breakthroughs so groundbreaking and revolutionary that we couldn’t even dream of them just decades prior. Thus, it is inevitable that the inevitability of old age itself will be overridden.

Old age is the number one cause of human death in western societies. It manifests itself in all sorts of different forms — heart disease, organ failure, weakening bones and muscles leading to increasingly prevalent and dangerous accidents, etc. We have been doing some research on the problem, and we have some intriguing leads on one of the possible causes of senescence (shortening telomeres after each cellular division) and some possible ideas on how to delay it (reduced calorie diets, probably mimmickable using drugs without the constant hunger). Yet we aren’t putting nearly the same effort into curing old age as we are into all sorts of lesser diseases that don’t kill anywhere near the same number of people. This point is made very elegantly in the form of a parable called The Fable of the Dragon-Tyrant; I highly recommend that you read it.

The only reason that we aren’t putting more effort towards curing old age is because all too many people think it is inevitable. They see it as part of being human, something to be accepted rather than overcome. Religion arguably exists to get people to accept that their time on Earth will come to an end, spinning all sorts of fairy tales in the process about infinite, perfect afterlives in heaven or reincarnation. But why look for consolation in myths when we can get rid of the reason for the creation of those myths in the first place? Death is bad; it kills people, and those who depart are sorely missed by the many who are still living. Don’t over think it; death is bad, thus solving the number one cause of death is good.

Imagine how much better the world would be if people didn’t suffer from old age. Instead of growing old and eventually becoming useless, you would simply continue being yourself, extending your productive life for decades, if not centuries. You could forget those ever-present fears in modern society of becoming unable to do things you once enjoyed, and becoming a drag on your loved ones. Is this not a worthwhile goal?

The only possible objection anyone could have to this plan is a concern over overpopulation. But consider that many western societies are already below replacement rates; having people live longer might actually be the only thing that would keep them from collapsing. And once lifespans are measured in centuries rather than decades, birth rates will go down. If you have centuries of fertile adulthood ahead of you, what’s the rush in having kids now? And don’t go assuming that all the humans that there ever will be will all have to be crammed onto just this one planet. We are eventually going to spread to the stars and beyond, so being able to live productive lives stretching across many centuries will be exactly what we need.

The next time that someone tries to claim that senescence is inevitable, that it is part of the human condition and not something to be overcome, gently tell them that they are wrong. The more minds that we educate, the more consciousnesses that we raise, the closer we will become to curing the worst plague ever to afflict humanity. And the stakes are depressingly urgent: for each further year that we dally and do not focus our full attention on the problem, millions more people will unnecessarily die.

Mirror-making breakthrough!

Monday, January 14th, 2008

When last I regaled you with tales of my continuing telescope-making adventures, I had spent four hours working back from an oblate sphere to a paraboloid. Little did I know how much I accomplished in that session. This past Friday, I only had to do about ten minutes worth of polishing before another Foucault test revealed that I might be done! Yes, that’s right, after more than four months of working on this cursed piece of glass, it could be good to go! I say “could” because the Foucault test revealed a pretty marginal 1/3.7 wavefront error, but most of that error came from an anomalous reading on the last zone on the very edge. Taking that reading out, my mirror was a respectable 1/5 – 1/6 wavefront error. Next Friday we’ll definitely do some more testing to determine more accurately what the situation is.

But the ultimate test is how well the mirror performs under actual use. If you pop it in a tube and it resolves clear images of what you’re looking at, all of the Foucault readings in the world are meaningless — the mirror is done! An un-aluminized mirror (aka glass) reflects about 4% of the light hitting it, making it more than good enough for viewing brighter stars and the Moon. So, I’ll try out the mirror as it is now, and if I like what I see, I’ll get it aluminized. If not, I’ll go back to figuring. But to test out how good it is, I actually need a tube to put it in.

Thus, I’ve started construction of the rest of my telescope. I went to the hardware store and bought most of the simple items I need: 3/4″ plywood, paint, screws, springs, silicone, and other stuff. I also put in online orders for all of the specialty parts that can’t be obtained in a hardware store: the focuser, diagonal secondary mirror, curved-vane spider, and eyepieces. I’m still missing a few things here and there, like angled aluminum to hold the mirror in place and teflon for the Dobsonian mount, but I’ll get it all eventually.

So it’s finally starting to look like I will actually finish this project. I will admit, it’s taken a bit longer than I thought to get where I am now, but I’m happy nonetheless. Figuring the mirror is the only truly precision part of the endeavor. Everything else is just basic handyman-type construction work: cutting wood to shape, screwing and bolting it together, painting, etc. That won’t pose a problem. Thanks to my dad and shop class in high school, I’m pretty comfortable around the various power tools I’ll need to use to finish this project.

And, just to tease you, here’s a picture of my tube after a day of painting. The tube is 55″ long and 10″ in internal diameter. I’ve applied one coat of primer on the inside and two coats of primer and one coat of topcoat on the outside. Still to go, a couple coats of flat black on the inside and another coat of topcoat and two coats of glossy acrylic on the outside. But even with just the one coat of topcoat, you can see now neat it looks. I chose a very unique type of paint for the topcoat. I didn’t originally have steampunk in mind when making this scope, but it looks like that’s where I’ll end up!

Telescope tube, 3 coats paint

Week ∞ of amateur telescope making

Thursday, January 10th, 2008

Last Friday at the telescope making workshop I made positive progress (though I’ve said that many times before). At the end of the session before that, I was left with a raised hill in the center of my mirror following a series of short strokes to correct my rolled over edge. So during this past session I focused on fixing the raised hill and trying to get back to paraboloidal. I basically did the same W-shaped parabolizing stroke for hour hours, with intermittent Ronchi tests, and the result was very promising. Take a look:

Mirror comparison

The photograph on the left shows my mirror at the beginning of the session. The central hill should be immediately obvious. Also note that the rest of the mirror doesn’t have the appropriate paraboloidal curve. The middle photograph shows my mirror at the end of the session. Notice how the central hill has been worked out, and the curvature has gotten better. This definitely warrants a Foucault test to see how close it is to the ideal curve. The computer-generated image on the right is what a Ronchi test on my mirror should look like if it was an ideal paraboloid. The number of lines isn’t really relevant here; what you should be looking at is the shape of the lines. And the central photograph makes the mirror looks a little bit scratchy; it’s not. I just failed to completely wipe all of the water droplets off of mirror after washing it.

So, I made an enormous amount of progress in just this one session (when I first started figuring, that amount of progress took a month). I’m getting better at this. I just haven’t arrived at my destination yet. Tomorrow is another night at the workshop. Hopefully it goes well!

I want humanity to spread to the stars

Thursday, January 3rd, 2008

I consider myself a futurist. I enjoy looking at not just the big picture, but also the long picture. I ask questions like, “Where will humanity be in another millennium?” I admit the chances of living to see any of it are slim (but not none!), but it fascinates me nonetheless. Just like others may love studying ancient history, I love imagining the possibilities of the future. It’s hard to say whether this is because I’ve read a lot of science fiction, or that I read a lot of science fiction because I am predisposed towards thinking about the future. I suspect there may be a feedback mechanism at work. But either way, that’s what I care about.

So you can imagine my chagrin when humanity does something really shortsighted, like creating false propaganda to confuse the issue of global warming so that corporations can save money while the planet dies, polluting space for a very temporary military propaganda boost, or cutting funding to vital Earth-facing satellite missions. So few people really think about the long term consequences of their actions. And of the ones who do, many aren’t moral enough to care about the consequences that will only become a serious problem after they are no longer around anymore.

My biggest concern, in the long view, is if humanity will develop technologically to the point where we can begin colonizing space. There are all sorts of obstacles in the way: those who don’t understand the ultimate importance of spreading our kind across the stars; global warming, which could destroy us (or at least cause us to focus all of our effort inwards) before we truly make it into space; catastrophic warfare (admittedly less likely since the end of the Cold War, but a potential political destabilization of nuclear-armed Pakistan could cause problems); and, of course, worldwide disaster.

The problem with only living on Earth is that we are putting all of our eggs in one basket. Just looking at the archaeological record, we can identify all sorts of massive extinction events — asteroid impacts, runaway global cooling, supervolcanoes — that we simply wouldn’t be able to survive. Yes, we have put a few humans into space, but that is but the first step. It only really counts when humanity is able to survive the total loss of the Earth. I’m placing my bets on a Lunar colony as the first to allow this fall-back scenario, but who knows, maybe Mars, despite its increased distance, will ultimately prove more suitable for large scale human habitation.

And then once humanity has colonized other worlds in this solar system, we would spread out to the stars. The technology for that doesn’t yet exist, but there’s nothing that makes it impossible. A large enough ship using a nuclear pulse drive for propulsion could make it to nearby star systems without having to break the speed of light barrier (something we not only do not currently know how to do, but most scientists think is forever impossible). And from then on, humanity would simply leapfrog amongst the stars, with each new colony sending out its own colony ships as soon as it develops enough to be able to construct and fill them.

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And the mirror figuring goes ever onwards

Wednesday, January 2nd, 2008

It’s been over a month since I last wrote about my amateur telescope making project, so I figure I owe an update to anyone who’s following along with this unexpectedly long saga. I’ve still been going to the workshop every week, it’s just that I haven’t been making any measurable progress, so I haven’t had much to write about here. I’ve been stuck in “final” figuring for over two months now; the mirror is all ground and polished, it just isn’t in the correct paraboloidal shape yet.

When last I blogged, I was having trouble getting my mirror paraboloidal. It was stuck somewhere halfway between spherical and paraboloidal. No good. We finally figured out that my pitch-lap was depressed in the middle, so we poured more pitch on top of it and essentially resculpted it to the correct shape. I also noticed that the lid of the plastic container I was storing my pitch-lap in was resting against the middle of my pitch-lap, pressing it downwards for the seven days between each workshop visit. After modifying the pitch-lap holder for height, I finally got my pitch-lap in just the perfect shape, and was able to go to work on my mirror.

So I got really close to the ideal paraboloid (about a 1/3 wavefront error). I had a 0.8 encircled Strehl ratio at one point (as determined by a Foucault test), which isn’t stellar, but it’s serviceable. But that wasn’t good enough for me. After spending so long on this mirror, I wouldn’t settle for mediocrity. So I pressed on, thinking it would only be another week of work to get my mirror into very good shape. Boy, was I wrong.

I ended up over-correcting my mirror past the ideal paraboloid. Even worse, I developed a rolled over edge, which was in hindsight inevitable, because I had a turned-down edge that was growing progressively worse with every week’s session. That’s just how it goes. All of the strokes I was using for parabolization tend to increase the severity of a turned-down edge. If I had finished quickly, the edge wouldn’t have been too much of a problem. But because of the defective lap I was using for so long, I was wearing down the edges for way too long before I had the center to the correct shape, and the edges ended up needing fixing.

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Celebrating Sol’s 4,568 millionth birthday

Wednesday, December 19th, 2007

I’m glad I held on to the very end of this year before proclaiming what the coolest news of 2007 was, because it’s just arrived, and I would have hated to prematurely give the crown to something else. Scientists at UC Davis have pinned down the age of the solar system to 4,568 million years, with a margin of error of about one million either way. This is by far the most precise estimate of the age of the solar system I’ve ever seen. In my astronomy classes (from 2003-2007) we were taught that the solar system was 4.5 billion years old. Now we have two more significant figures! I can’t really explain why, but knowing that figure with such precision is meaningful to me. I’ve already committed it to memory and I shan’t forget it. It’s easy to remember; each digit is monotonically increasing, with the first three being sequential (yeah, that’s how I handle larger numbers).

In the brief period of time between when I saw the headline and when I read the rest of the article, all sorts of thoughts raced through my mind. The most prominent was, “How did they do it?” My first guess was radioisotope dating of material from asteroids (as there’s no rock native to Earth that dates back that far). Uranium-238 has a really long half-life (4.468 billion years), so that was my guess as to what isotope they used to do the dating. The other possibility I came up with was that they used some form of advanced computer modeling of the dynamics of the solar system, but I would be really surprised if anyone could get such accuracy from a simulation.

Well, it turns out my first guess was correct. The scientists at UC Davis performed a radioisotope analysis on samples from asteroids that date back to the beginning of the solar system. My guess of uranium-238 was incorrect though; they actually used manganese-53, which decays to chromium-53 with a half-life of 3.74 million years. That’s a very short half-life relative to the age of the solar system, so the final amount of manganese-53 left in these asteroid samples is incredibly minuscule compared to what it once was. But thankfully, there was still enough left with which to measure to determine the age. As for the type of radioisotope analysis performed, they specifically used radioisochron dating, which compares relative quantities of the unstable isotope (manganese-53) with its resultant decay product (chromium-53) to determine age.

Of course, I was so excited about this news that I immediately told everyone about it, including all of my friends who happened to be online at the time, a friend who happened to call me, and my family. There were two common misconceptions that I’d like to address just in case anyone else who reads this joyous news happens to wonder about them.

How do we know it’s from the solar system? The vast, vast majority of the stuff in our solar system was all born here, and at the same time to boot. The chance of some substantive object being propelled with enough velocity to leave another star system and then get captured by ours is incredibly small. Pick anything at random in this solar system (Sol itself, the planets, moons, asteroids, comets, dust, etc.) and the odds are incredibly good that it’s from around here. But to deal with the off-chance that you end up with something not from around here, you perform the same test on a variety of different asteroids. The chance that they all happen to be from outside the solar system is negligible.

How do we know it’s from the beginning of the solar system? This is a very valid question to ask, at least of materials found on Earth. Earth is a very lively place, with all sorts of geological and chemical processes going on that continually break down older rocks. There isn’t anything on Earth that has been left untouched since the formation of the solar system (if I remember correctly, the oldest rock we’ve found dates back to a paltry 3.8 billion years). So that’s why you need to look at asteroids. Asteroids are too small to have tectonic activity capable of metamorphosing rocks, and out in space, they certainly aren’t hot enough to cause the other kind of metamorphic activity that would change the structure of the rock. So they’re unchanged since the formation of the solar system simply because there’s no mechanism that could change them.

And keep in mind, everything in the solar system formed at the same time in a very rapid process (hey, less than a million years is definitely rapid compared to 4.568 billion years). So all you have to do is test a variety of different asteroids and note that the oldest of the resultant ages all tend to cluster around one number. We wouldn’t expect to find any chunk of asteroid older than the age of the solar system, and indeed, we haven’t. You know it’s good science when the experimental results are repeatable, and these are definitely repeatable.

So look for scientists to continually narrow down the age of the solar system even further in the coming decades as they get more data and more accurate test equipment, but never again will we experience a jump from imprecise estimate to quantified value — with margin of error! — in this number so meaningful to us, the age of the solar system. Remember this day.

Slow and steady wins the telescope-making race

Saturday, November 24th, 2007

A Ronchi test on my mirror as of 2007-11-16
The amateur telescope making (ATM) workshop wasn’t open yesterday on account of Thanksgiving, but I still haven’t written up a progress report yet on last week’s workshop, so I’ll go ahead and do that now. But first, allow me to talk about the others in the workshop, because there are some fascinating people there without whose help I would not be able to go on.

The workshop has been getting really busy lately. Guy, the guy who runs the workshop, says this always happens around autumn. I believe it. Last week I counted a record sixteen people at the workshop (it had been as low as four a month prior). Many people there are just starting on their projects, while others are returning from long absences to finish theirs up. A father is making a 8″ scope with his young son. A young man in the Armed Forces is making an 8″ scope, and last week his high school aged (?) friend joined him, making his own 6″ scope. There are also several older people making scopes, one of whom is quickly catching up with me.

Then there are the veterans, the people who’ve done it all before, multiple times, and just show up to hang out with friends or make steady progress on their projects in the company of others. One man has at least ten different mirrors and lenses under various stages of construction. He’s also built a mirror-matic at home that he uses for rapidly hogging out and polishing mirrors (it can be done faster than a human with a lot less effort).

Another man, an electrical engineer, is currently working on the automatic grinder in the workshop, which was built and then donated by a previous person at the workshop who gave up on their mirror. The automatic grinder needs a lot of work, but it is salvageable. He also likes singing and playing piano, and he’ll occasionally entertain the rest of us by playing on the piano in the workshop (it doubles as a music instruction room; the piano sits right next to the vaccum chamber).

And then there’s Bill, who seems to find a sense of zen in telescope-making. He polishes really slowly, trying to create the perfect mirror with no imperfections at all. But he doesn’t even keep the end products of his work. He donates them to Guy, who either sells them to raise funds for the workshop or uses them in telescopes for a weekend program he teaches at for inner-city DC youth. Guy recently built three brightly-colored telescopes that he uses to get the kids interested in science. As far as I know, the mirrors were all donated by Bill. Bill has been trading blanks with Guy to build more mirrors out of, and he’s also taken on a few mirror projects abandoned by people who stopped showing up at the workshop long ago, leaving their projects unfinished.

So that’s the story of who shows up to the workshop. It’s a really great group of people, with a nice mixture of ages. Everyone is there because they want to be, not because they have to be. It’s thus a much different atmosphere than, say, school or work.

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