Speak of the devil

I was back at the Lick Observatory this evening, with another UCM field trip group.


Like last time, we all got to look through the 36 in Lick refractor (that's the Shane reflector above).


Unlike last time, Saturn was up. Can you guess what that means?

Railgun!

The Navy set a new record for the most powerful railgun shot, and brought my dream of cosmically powerful weaponry one step closer to reality.

From the story:

Thursday’s test produced a record 10.86 megajoules, which sent the 7-pound aluminum slug at Mach 7 (more than 5,000 mph) for 80 meters, a roughly 20-millisecond ride.

Before:


Check out the visible shock wave. That's what you get at almost 1.4 miles per second.

After:


According to the story, the shot trap was a steel box filled with 2.5 tons of sand, and after the projectile hit it, it was splayed open like a flower. I wish we had some pictures of that, instead of this stupid billboard getting blown to hell and gone. Ah well.

The long-promised, oft-delayed Lick refractor post

...is not here. I ended up saying everything I wanted to say when I put the photos up on my Flickr page. If you have no idea what the heck I'm talking about, see here and here and here. The upshot is that on Sept. 15 last fall I got to put my eyeball on the end of this 57-foot-long telescope, and saw some stuff that is still blowing my mind four months later.

The observatory is open to the public. If you get a chance, go.

Get your giant robot dinosaur on

Full disclosure up front: about two months ago, someone associated with Walking With Dinosaurs: The Live Experience got in touch with me to see if I'd be interested in blogging about the show. Tickets were mentioned.

I put him off for a LOOONG time. Mainly because the only two California shows are in late December and early January, and I thought I'd be unavailable for both. But it turns out I will be town the first week of January after all, so I'm accepting the tickets and blogging about the show.

Now that you know I'm a corporate shill, you can believe what follows or not. I'm gonna say it anyway. If you suspect contamination, feel free to compare this post with everything else I've ever said about pop-culture dinosaurs, big machines, and monster movies, and see if I'm writing true to form. To their credit, the folks at Insight Management have been tremendously patient and they haven't given me any pointers or restrictions on what to say, beyond asking that I direct folks to the official site for photos and videos. Fair nuff.

FIRST thing is that I've been meaning to blog about this anyway, because it looks awesome. Jarrod sent a link to one of the videos months ago. The animatronic dinosaurs are very smooth. I love robots. My affection for dinosaurs goes a few orders of magnitude beyond that. So I was already on board.

SECOND thing is that I am continually surprised at how unpopular dinosaur shows and movies are among paleontologists. At least recent ones. The consensus seems to be that Ray Harryhausen's work is beyond reproof (which is true, if a little patronizing given what follows), but bring up Jurassic Park or Walking With Dinosaurs or the new King Kong and it's carp carp carp carp. Some favorites:


"They're just exploiting dinosaurs to make money!"

Goodness gracious! Why, I never! Those horrible capitalists, making a killing by selling people what they'll pay for. I'm equally outraged by the science fiction workers (in any medium) who exploit my yen for creepy aliens, space battleships, and exploding planets. Which is to say, not outraged at all, and in fact quite in favor of it. I'm still a little put out about the general lack of exploding dinosaurs, which I've mentioned here twice before. What do I gotta do, write a paper about it? Oh, speaking of:

"But you're a scientist. You work hard. What if they take your work and use it to make a movie and you never see a penny?"

Yes, yes, I am put upon. But let me see if I can climb down off the Science Cross and take a stab at this one. The possibility that someone else will use my ideas without paying me is a side effect of the maxim that science should be free. Mine is. Don't get me wrong, I love consulting on media projects. Because the gig is basically answering questions about dinosaurs--something I like doing and usually do for free anyway--and the amount of money that media folks have to throw around is pretty sweet compared to what I make lecturing about photosynthesis. But better than the money is the ability to sleep the sleep of the innocent, knowing that I have given the fruits of my labor to all mankind. Sounds melodramatic, I know. But it's true. If someone uses that to make a better monster movie, that's gravy.

The granddaddy of all ex-paleo objections to pop culture dinosaurs, though, is that...

"That's so unrealistic! Why, just look at the external nostril! It must be at least two-thirds of the way back in the bony naris--it's nowhere near Witmer-compliant!"

Yes, it's true, pop culture dinosaurs always fall short of full scientific respectability. Always. If you can show me a counter-example, I can give you at least half a dozen reasons why it actually sucks. I can think of at least three reasons why this is so:

- Media folks are in the making money off dinosaurs business, not the making textbooks business. See above.

- Paleontologists rarely agree about anything. I'm not just talking about stuff like BADD vs BAND, boredothermic vs apathetothermic, etc. I mean everything, from nostril position and pupil shape and size on out to muscle mass, fat deposits, etc. Or rather, we do have broad areas of agreement where the scientific questions are pretty much settled. But those areas are generally not the ones that are of much use if you're trying to reconstruct a living critter that looks and behaves convincingly. Like it or not, the whole life restoration business has a bit of a stigma amongst some Serious Paleontologists. Even if one could generate a static restoration that satisfied everyone, as soon as it moved an inch someone would start bitching.

As a case in point, there are aspects of the WWD sauropods with which I disagree violently. And the advisors who told 'em to do it that way are friends of mine, whom I like personally and whose work I respect. But (#1) respect and agree with are not the same. And (#2) only the paleontologist part of me disagrees violently. The guy-who-likes-dinosaurs side, which has an 18-year head start, thinks CGI sauropods rock and has literally spent hours watching them stomp around.

- I don't even agree with myself. The paleontologist part of me is a bit over a decade old, and I look back at some of the stuff that came out of my word processor back then and just shake my head. There is a line from an SVP abstract that I would erase from all human memory if I could. It's so appallingly dumb I'll probably end up blogging about it. But I've made peace with all that. Scott Aaronson has opined that if you're not occasionally wrong, your science is boring (not in that specific post, I just like that one and can't be bothered to find the real one). My ambition since I started has been to push (my particular tiny corner of) the edge of the envelope. Not for fame or glory. For curiosity. As soon as I get to the top of one hill, I want to see what the view from the next one looks like. And occasionally I've been wrong. That's life. More importantly, that's also science.

This is the tip of whole 'nother rant, about how science actually works and about the entirely overdone phobia among scientists of ever admitting that we've ever been mistaken about anything, which I'll have to expand on later.


But back to task. There is the practical matter, which is that a documentary or book that followed every one of my ideas to the letter would be outdated in a couple of years even to me. And there is the not-being-a-colossal-hypocrite matter, which is that if I can cut myself that amount of slack, I should be equally easy on other scientists (not easier--birds really are dinosaurs, etc.--just equally easy). If we're all ever 100% right, then science is over and we can get back to Resident Metal HaloStrike III with a clear conscience. Or commit suicide because we're bored to tears. And if I can forgive my fellow scientists for occasionally veering away from the Word According to Matt, I should multiply that forgiveness a couple of times to non-scientists who do stuff with dinosaurs. Who, in my admittedly limited experience, usually do want to get it right and are often baffled by the contradictory cacaphony coming out of the Academy--even as those of us on the inside recognize that conflict is vital to the success of the scientific process.

And--importantly--there is the guy-who-likes-dinosaurs matter, because he doesn't really care where the external nostrils are. Hell, he's nearly cried just daydreaming about live dinosaurs (and been man enough to admit it), so he'll probably wet himself when the life-size animatronic T-rex comes out and starts wrecking shop.


I'm still not done.

The ultimate reason why I am blissfully unruffled about the perceived scientific failures of the recent CGI dinofests is that I cut teeth on Saturday afternoon reruns and 50s-vintage dinosaur books. When I was 5 I knew all about Antrodemus and Trachodon, both of which stood bolt upright and dragged their tails, just like God and Neave Parker intended. (How many of you Gen Z weenies know what the hell I'm talking about [without any help from Google or Wikipedia]?) Where I came from, you couldn't get through a dinosaur movie without a fur-clad stud chucking a spear at a carnosaur while a bat-winged pterodactyl made off with the scantily-clad object of his affection. Three-fingered tyrannosaurs duking it out with giant apes, submarines fighting Brobdingnagian cephalopods, pissed-off brontosaurs eating guys out of trees, and cowboys lassoing dinosaurs in a lost valley--we had it all.

And I turned out all right.

So I'm pretty sure that the current generation of up-and-coming paleontologists will survive near-sighted tyrannosaurs and Diplodocus ovipositors. In fact, given that many of the current (and, okay, slightly older) generation freely admit that they became paleontologists because of the efforts of Ray Harryhausen, Neave Parker, et al., I'm willing to bet that CGI dinosaurs are one of the best things that ever happened to this science, even (maybe especially) when said dinosaurs stomped in from off-campus.


That goes for immense non-CG robot dinosaurs that roam around live on stage, too.

Anyway, to reiterate the main points of this essay, WWD Live looks pretty sweet, it's playing in San Jose on Dec. 26-30 and in Sacramento on Jan. 3-6 (other cities and dates are listed on the site), and barring cosmic accidents or someone giving me the axe for overly-genocidey blogging, I'll be there. And then back here to give my honest opinion.

The first and last photos are off the WWD Live tyrannosaur, and were provided by the folks at Insight Management. The rest are screencaps from One Million Years B.C. (#2) and The Valley of Gwangi (3 and 4) borrowed from various places on the interwebs.

Merry Christmas to all, and to all a good night.

The vastly overdue Shane reflector post

Back around the dawn of time I blogged about my visit to the Lick Observatory, and concluded by saying that a post on the 3-meter Shane reflector was "up next". Here it is. In my defence, I am following in the footsteps of a master here.

There's more, by the way, but it's not done, and if I wait for it this will never get blogged. You've heard the saying, "The perfect is the enemy of the good"? In my world, the adequate is the enemy of the incomplete and horribly delayed.

On to the scope.

The Mirror

For a while, this telescope was the second-largest in the world, behind the 200-inch (5-meter) Hale reflector at Mt. Palomar. And in fact this telescope came into existence as a by-product of the Hale telescope. No one had ever made a 200 inch mirror before, so they practiced with a series of test blanks to make sure they could cast that much Pyrex at once. The largest test blank was 3 meters in diameter, and it turned out fine, so they proceeded with the 5-m beast. The 3 meter blank went into a warehouse. It had never been intended to become a working mirror, it was just a prototype. But some UC astronomers got in touch with the folks at Cal Tech, who sold it to UC for something like $50,000, which was basically giving it away.

Like the 5 meter Hale mirror, the 3 meter test blank has a honeycombed back surface to reduce the mass of the mirror. From the reverse it looks like a waffle, with big spaces going deep into the glass. So deep, in fact, that when the blank was ground into a mirror, it could not be figured into a sharp curve or the center of the mirror would have been too thin. Most big observatory telescopes are fatties with short focal ratios (at least at the Newtonian focus; more on this in a later post). The Shane reflector has such long lines because the curvature of the mirror is so shallow; light rays coming off the primary mirror do not converge as sharply as they would if the mirror formed a deeper bowl. And a long telescope needs a big dome, so the Shane dome is huge. In contrast, the Automated Planet Finder will be a 2.4 meter telescope and it is going in a dome with less than half the diameter of the Shane dome.



Celestial Motion and Telescope Mounts

There is another reason why the Shane dome is huge. It's because of the telescope's mount. The rotation of the Earth means that from a fixed observing spot, everything in the sky appears to rotate. The only exceptions are the celestial poles; the north celestial pole is marked by Polaris, the North Star. It is the point of light around which all the stars are seen to whirl in long-exposure photographs like the one shown here (image swiped from here).


This constant motion of celestial objects is a real pain in the butt if you want to look at something at high magnification for more than a few seconds. You need some way to keep the telescope pointed at the same spot in the sky even though the Earth is rotating underneath it.

The simplest kind of telescope mount is the alt-azimuth mount. Think of how cannons are mounted in turrets. You have to be able to slew the barrel from side to side and raise it up and down. That's an alt-az mount. The problem is that celestial objects describe complex paths through the sky. Think about the southernmost stars you can see. They rise in the south-southeast, describe a very shallow arc across the sky, and set in the south-southwest. To track one requires constant adjustments in both altitude and azimuth; in fact, not just constant adjustments, but constantly varying adjustments. A clock drive won't cut it.

Now we have computers that can calculate these constantly varying adjustments and control the motors needed to track celestial objects using an alt-az mount. So a short, fat telescope like the APF can have a simple alt-az mount and sit in a very small dome (comparatively). But this level of computer control is a comparatively recent development in the history of astronomy; it was not available when the Shane reflector was built.

The other type of common telescope mount is the equatorial mount. Like an alt-az mount, an equatorial mount has two axles. The first axle is aligned with the Earth's axis of rotation (for backyard astronomers, it points toward Polaris). Slewing the telescope around this axis moves it in the equivalent of longitude (called right ascension in astronomy). The second axis is at right angles to the first, and moves the telescope in the equivalent of latitude (called declination).

Any sufficiently distant object in the sky has fixed coordinates for right ascension and declination. These are the fixed stars, and it is not hard to see why the ancients thought they were attached to the inside of a giant hollow sphere. Once a telescope on an equatorial mount is lined up on its target, it needs no further adjustment in declination (or latitude), and it can be adjusted in right ascension (or longitude) at a fixed rate--the rate at which the Earth rotates.

Compare this to the alt-az system, in which even the fixed stars have constantly varying coordinates in both axes, and keeping a 'scope on target requires adjusting its movement around both axes at constantly varying rates. The alt-az system does have one major advantage over the equatorial system, which is that it can be mechanically much simpler (assuming you have the computer power to keep it tracking); basically the telescope is on a simple turret or cannon-style mount.

If you need a better way to visualize this, most planetarium programs will project alt-az and equatorial grids on the sky (including Stellarium, which is free and a cinch to use). Speed up the time lapse and see what happens. The alt-az grid stays fixed and the stars move across it. The equatorial grid moves with the stars; the gridlines themselves rise and set as the whole grid rotates around Polaris (from our fixed viewpoint).

The Mount

The Shane reflector was one of the last big observatory telescopes to be completed before computer-controlled alt-az mounts became practical. Consequently, it is on one huge-ass equatorial mount. A giant metal fork holds the telescope; the whole assembly weighs 145 tons. The handle of the fork is the polar axis, aligned on the north celestial pole. The tines of the fork hold the telescope in the declination axis bearings. The whole thing is so well balanced that the right ascension drive motor, which turns the whole 145-ton rig, is a 1/25 horsepower electric motor that can sit in the palm of your hand.


A Word on Aperture

There is a saying in astronomy: Aperture Rules. Department store telescopes are often sold on (wildly inflated) claims about magnification, and when people see a telescope often the first thing they want to know is what magnification it yields. The answer for any telescope is, "Whatever you want, depending on what eyepiece (or optical instrument) is fitted." You can point a little department store scope at Jupiter and crank the magnification up to 1000x if you like, but beyond about 30-50 power the image will be too dim, too shaky, or just impossible to bring into focus because of poor optics.

Fact is, you can see a LOT at very low magnification. A pair of 7x35 binoculars only magnifies at 7x, but it will show you the Galilean moons of Jupiter, the Andromeda galaxy, the Orion Nebula, the Double Cluster in Perseus, and literally hundreds or thousands of other celestial objects. Binoculars often beat very small telescopes because they don't try to overmagnify; instead, they are built to optimize another variable: aperture.

When your eyes are fully dark-adapted, your pupils are about 7mm (+-1mm) in diameter. Now, I'm sure you've seen a zillion cut-away views of what eyes look like inside, so you know that your lens is bigger than your pupil and your retina is larger still. When you are looking at stuff up close, converging light rays can fit through your pupil and diverge on the other side to strike your much larger retina. But when you look at something far off, the light rays coming from it are parallel with each other and perpendicular to your pupil, so the size of the pupil aperture puts a very firm limit on how much light your eye can gather. The amount of light gathered is proportional to the area of the aperture; for a pupil with a diameter of 7mm, the aperture area is (pi)(r)^2 or just over 38 square mm.

The optical train of a binocular or telescope is effectively a funnel for light, gathering it over a large area and condensing it to pass through your relatively small pupils. Back to the 7x35 binoculars. Each primary lens is 35mm in diameter--five times the size of your pupil in linear dimensions, and 25 times larger in area (961.5 square mm). So you can gather 25 times as much light with binoculars as you can with the naked eye. A pair of 7x50s will be even better, with the aperture of each lens being just over seven times that of your eye in linear dimensions, and 49 times larger in area (1962.5 square mm). So although they are only 43% larger than the 7x35s in linear terms, the 7x50s actually gather just over twice as much light.

A good beginner's telescope (i.e., not a department store cheapie) will offer three to six inches (76-152 mm) of aperture. A three inch scope gathers 118 times as much light as one of your eyes. A six inch scope gathers 471 times as much as your eye, and four times as much as the three inch scope. Objects that are nearly invisible to the naked eye and dim blurs through binoculars can look awful purty when viewed through a six inch scope.


Now it is easy to see why the history of observatory telescopes has been one long quest for more aperture. At 3 meters in diameter, the Shane reflector has a mirror area of just over 7 million square mm, or 186,000 times the area of one of your dark-adapted pupils. The twin Keck telescopes on Mauna Kea (shown above) have mirrors 10.2 meters in diameter. Each telescope has a mirror area of 326 square meters, or 326 million square mm--almost 50 times more light-gathering area than the Shane reflector, and almost ten million times the light gathering power of the naked human eye.

---------------------------

What's "up next"? There is an unfinished section on the different foci of the Shane reflector, and all of this is just buildup to blogging about the Lick refractor, the one I put my eyeball next to back in September. All of this is subject to whatever delays come in because of teaching, doing enough writing to mollify my coauthors, feeding the monkey over at SV-POW, unanticipated manias, my general unreliability, and the erratic changes in topic and post rate that I deliberately cultivate here at ADV. Still...

Stay tuned, true believers.