Monday, May 28, 2012

Earth-Venus Conjunction Explanation

I've previously mentioned the upcoming transit of Venus, and said I'd write more about it, then completely forgot about it. So tonight I'd like to rectify that by writing a bit more about these amazing events. Looking back at my previous post I see two things that I specifically mentioned talking about: further details of how Earth's and Venus's orbits interact, and more about why transits of Venus are scientifically important.

As I wrote in my earlier post, transits of Venus happen at what appear to be – at first glance – rather strange intervals. Specifically, in the present era, transits happen in pairs 8 years apart, separated by intervals of either 105.5 or 121.5 years. The reason this happens has to do with the shape and orientation of the orbits of Earth and Venus. In the picture I put together below, the orbits of Earth and Venus are shown at the correct scale relative to the Sun and each other. Earth's orbit is green, and Venus's is blue. Venus and Earth themselves are too small to be seen at this scale. One point of terminology: the point when Venus passes Earth in its orbits is called its conjunction.

Although the angle between Earth and Venus's orbits is only 3.4°, you can see in the top half of the picture that most of the time Venus passes above or below the Sun at its conjunction (when it passes us in its orbit). The only time we can actually see it cross the face of the Sun is when both planets are close to what is called the line of nodes of their orbits. This is where their orbits cross as seen from edge on (as seen in the top half), and is denoted by the dashed red line in the lower half of the picture. The location of Venus's conjunction, however, is not fixed, but moves slowly backwards around the orbit over time. Whenever it happens within a narrow region around the line of nodes, a transit of Venus is seen.

Because of the arrangement of their orbits, 8 Earth years are almost exactly equal to 13 Venus years (with a difference of just 0.4 days). That is, each 8 years Earth and Venus are in almost exactly the same position relative to each other, just rotated slightly along their respective orbits. Thus, two transits of Venus can happen 8 years apart within the narrow region around the line of nodes, but the region is narrow enough that adjacent conjunctions result in Venus passing above or below the Sun as seen from Earth. Currently Earth reaches the line of nodes in June and December, so transits occur in pairs with one in December (such as the 2004 transit) and one in June (this one).

But why the 105.5 and 121.5 year intervals between transit pairs? That results from the fact that neither Earth's nor Venus's orbits are perfectly round (although Venus's orbit does have the lowest eccentricity of all the planets). Because of this fact, the rate that the Earth-Venus conjunction moves is not constant, and also has a different distance to move. This difference causes the difference in duration between pairs.

Hopefully the preceding explanation has helped you better understand what's going on. I'm going to defer the explanation of the scientific value of a transit for a later post as this one is getting pretty long and I need to get to bed. I also hope to show you the designs for the posters for the transit of Venus that I created, which have now been printed and are actually on sale for a limited time around the transit!

Tuesday, May 22, 2012

Music of the Spheres

After my last post featuring Portal 2 music played on rather unconventional instruments, I thought it would be fitting to feature this piece of wonderful Portal-inspired music using more conventional instruments. To clarify, this piece is a medley of 12 different tracks from Portal 2 (and one from the original Portal) re-imagined and scored for orchestra. It's pretty amazing. Check it out:

And unfortunately no, despite this post's name, the track “Music of the Spheres” is not actually part of the medley. Though it would certainly fit right in...

Friday, May 18, 2012

Now You're Thinking with Tesla Coils!

Seeing as how I posted some music on my birthday last year, I feel it would be only appropriate to do so again this year. And seeing how I talked about Portal and Portal 2 yesterday, it would be even more appropriate for me to show you this absolutely amazing video I just came across of one of the songs from Portal 2 played on Tesla coils. Yes, Tesla coils.

Just go watch it already.

This is simultaneously one of the coolest and most beautiful things I have ever been privileged to experience. I'm not ashamed to say that it's brining tears of joy to my eyes. Though to fully understand the significance of the song (“Cara Mia Addio”), you really need to have played Portal 2.

Finding this video was really a wonderful birthday present. Oh, almost forgot, I'm 23 today.

Thursday, May 17, 2012

Now You're Thinking with Portals.

My apologies for the lack of posts this lack week. I spent the majority of the week working, and when you're pulling 12-hour days it really leaves you with a distinct lack of inspiration and motivation for writing. It usually takes me a day or two to fully recover, by which point it's time to go to work again in a rather vicious cycle.

But you're not reading this to hear me make excuses, you're here for another of my random musings. Today I'd like to talk about an event that happened last week. This event was the release of the Perpetual Testing Initiative that added an in-game level editor to Portal 2, along with Steam Workshop incorporation so that maps made could be easily published and downloaded.

If most of the words in that last sentence mean nothing to you, let me take a moment and explain. I suppose I should begin by mentioning the fact that there is a company called Valve, which is responsible for creating some of the best computer games ever made, at the expense of being so perpetually late that it spawned the concept of “Valve time”. (This is mainly because, unlike most game companies, Valve is entirely employee-owned and thus can take the time necessary to make sure that what they do is done right without having to worry about investors or returns. Since they may very well be the most profitable company on a per-employee basis on the planet, it seems to be working for them.) Anyway, Valve also created a program called Steam that gives users the ability to conveniently organize, buy, and download games. A bit less than a year ago (October 13, 2011 to be precise), Valve introduced the Steam Workshop, which allows people to submit their own content for various games for easy downloading and installing by other people.

To explain the rest of that sentence in the second paragraph, I need to explain about Portal. (And I should mention there are some spoilers for Portal and Portal 2 ahead in the pictures, though I've tried to keep it to a minimum in the text.)

Portal is a game, released in 2007, that very quickly gained an enthusiastic following for its mind-bending gameplay mechanic and quirky, humorous writing. The central theme of the game is the eponymous portals. You, the player, have a portal gun (known in-game as the Aperture Science Handheld Portal Device) that allows you to create the two ends of what is essentially a wormhole, creating an opening that allows you to enter one portal and exit the other. The game then focuses on using portals to solve puzzles – separated into modular “test chambers” in the cryptically-named Aperture Science Computer-Aided Enrichment Center – that typically require some outside-the-box thinking to complete using various components such as buttons, boxes, and a few other devices that can be brought or sent through portals in order to satisfy certain requirements necessary to open the door and proceed to the next test chamber.

Looking into and back out of a pair of portals, to see behind you.

Portal was released to near-universal acclaim, with the innovative thinking required to play being cited as one of the chief joys. I'm sure that many physicists, like myself, were intrigued at the implications of being able to play around with the currently highly-theoretical concept of wormholes. The ability to conserve energy between portals meant you could jump from a height into one portal and come out the other at a high speed, potentially using this to “fling” yourself across barriers or gaps. It's always fun to watch people's first exposure to portals, and their “Aha!” moment when they finally grasp how they work.

See that robot up ahead there? That's you. Yes, you're looking into one portal and out the other and back in and...

One of the few complaints people brought up with Portal was that it was too short. Even an inexperienced player with no prior knowledge of portals could complete the game in a few hours, and it was mainly the stellar writing for the game's main antagonist, a computer in charge of the facility named GLaDOS, that saved it from being little more than a glorified demo.

See these? These are turrets, and despite their ridiculously adorable voices they will not hesitate to pump as much of their limitless ammo into you as possible. Easily incapacitated by knocking them over, however. Also have a surprising aptitude for music.

Fast forward to 2010, when Valve announces the upcoming release of a sequel, Portal 2, which elicited much rejoicing among lovers of the original game. Fast forward again to April 18, 2011 when Portal 2 came out to even more widespread acclaim, going so far as to gather several Game of the Year awards and earn perfect or nearly-perfect scores from dozens of reviewers. The gameplay was improved with a few annoying parts from Portal removed or modified, the addition of several new elements and characters (with similarly high-caliber writing), and I'd be remiss if I didn't mention the incredible music that fills and surrounds the game, adding to the incredible atmosphere throughout.

I'm getting a bit off-topic, because what I wanted to talk about was the recently-released Perpetual Testing Initiative for Portal 2 that came out last week. You see, the Portal games are puzzle game, which cause most of their joy by being novel – encountering a puzzle you've never seen before and trying to figure it out (which is pretty much what scientists like me love to do anyway, just with more math and less action). Now, while Portal 2 is much longer than Portal (a typical play-through for me takes about 10 hours, plus at least a couple more in the delightfully fun 2-player co-operative mode), there's still only so many times you can solve the same puzzle before it starts to lose its charm.

GLaDOS and the two robots (P-body and Atlas) that show up in the co-op mode.

The good folks over at Valve knew this, and thus released the tools they used for building maps for Portal 2 along with it. The only problem is that these were professional game design tools and thus quite Byzantine and unintuitive for the new user. I'm sure that a lot of people like myself took a look at them and never bothered to put the effort into overcoming the steep learning curve necessary to master them. It didn't help that the only way to play a new map was to manually place it in a certain folder and then open it from the console, since there was no way to do it in the main menu.

A character you meet in Portal 2, about whom I can't say too much for fear of spoiling it. This is one of my favorite moments in the game, though.

Now, Valve is also known for being great about releasing additional downloadable content for their games, and they have already released a completely new course for the co-op mode entirely free of charge. But while it would be nice if they could keep releasing new maps, realistically they have other things to do, and there's only so many maps their relatively small workforce can think up, create, and playtest.

A picture from the oh-so-fun co-op mode, as I attempt to get my partner up to my level through the use of special bouncy paint (the blue stuff).

This led to the absolutely brilliant idea of letting the players themselves create new maps, by coming up with a simplified in-game editor and integration with the Steam Workshop that allows new maps to be published and played with just a few clicks. This is the essence of the Perpetual Testing Initiative, and as of this writing, 8 days after its release, there are already over 82,000 entries into the Portal 2 Steam Workshop section. Yes, you read that correctly, that's eighty-two thousand.

A picture from the in-game level editor of my first published creation, “Turretopia”.
What's especially neat is that a few of those test chambers are mine! That's right, I have decided to embark on the vast forbidding sea that is designing a high-quality test chamber that is fun to play and (hopefully) gives the player that delicious “Eureka!” moment when the solution finally clicks into place. If there are any Portal 2 players reading this (and I do hope that I have convinced you to check it out) you can access my workshop files here. I'd like to keep releasing new test chambers and improving my test-designing capabilities, so constructive criticism is much appreciated.

(Random Trivia Fact of the Day: The title for this post comes from the tagline of one of the earliest trailers for Portal, where at the end you hear GLaDOS intone “Now you're thinking with portals!”.)

Thursday, May 10, 2012

Thor's Helmet

Continuing my chain of astronomical images, tonight I have an image of a beautiful nebula, NGC 2359, popularly known as Thor's Helmet after its shape.

NGC 2359, "Thor's Helmet", in Canis Major. North is to the left in this image.
NGC 2359 is about 15,000 light-years away, and around 30 light-years in size. It's a rather unusual kind of planetary nebula. Most planetary nebulae (as discussed before) come about from stars roughly the size of the Sun, gently wafting out the outer layers of their atmospheres as they reach the end of their lives. NGC 2359, in contrast, has a rare kind of star known as a Wolf-Rayet star at its center. Wolf-Rayet stars are extremely massive stars (at least 20 times more massive than the Sun) that are vigorously blowing their outer layers off under their own massive power generation (remember my talk about the Eddington Limit from the Eta Carinae picture?). Out Sun typically loses \(10^{-14}\) solar masses' worth of material each year; Wolf-Rayet stars typically lose \(10^{-5}\), a billion-fold increase.

The complex shape of NGC 2359 may be the result of interactions between the central star's stellar wind and a nearby molecular cloud, a region of greater-than-average gas and dust density. It's a rather faint nebula, so I'm glad I was able to get as much of it as I did (and it still required some pretty good histogram stretching to be this bright). The colors, though, are roughly correct, as I used wide-band filters instead of narrow-band ones.

Monday, May 7, 2012

Globular Cluster Photo Series (Part 18): M53

Today's picture (I'm slowly getting through the ones I have lying around) is the globular cluster Messier 53. M53 is a bit large as far as physical size goes, measuring about 220 light-years across, which gives it a visual diameter of 13.0 arcminutes at its estimated distance of a whopping 58,000 light-years from us. M53 is genuinely far out there, as it is also about 60,000 light-years from the galactic center, almost twice as far away from it as we are.

Messier 53 in Coma Berenices.

Like Messier 64 that I showcased yesterday, M53 is located in the constellation Coma Berenices, or Berenice's Hair, a small, faint constellation near Leo. According to legend, Queen Berenice II of Egypt had long, golden hair that she was quite proud of, and which she promised to sacrifice to Aphrodite if her husband King Ptolemy III Euergetes returned safely from his military expedition against the Seleucids. When he did so, she cut her hair and donated it to the temple, only for it to turn up missing the next morning. Thinking quickly, the court astronomer, a guy by the name of Conon of Samos, told the furious royal pair that the gods had apotheosized Berenice's hair into a constellation, indicating a misty patch of stars that have ever after borne that name. Interestingly, Ptolemy (the 2nd-century astronomer, not the king) did not include it in his definitive list of 48 recognized constellations, considering it part of Leo, though he did refer to is as “the lock [of hair]”. (He considered it to be the tuft of hair at the end of Leo's tail, which does make sense given its place in the sky.)

M53 contains a total of 47 RR Lyrae variable stars, a not inconsiderable number. Its stars also happen to be even lower in elements heavier than hydrogen and helium than most other globular clusters, which are already much lower than stars like the Sun. And other than that, I'm afraid there really isn't much more of interest to write about it tonight. A hui hou!

Sunday, May 6, 2012

Black-Eyed Galaxy

I haven't traditionally done a lot of galaxy images in the past, but today I have a picture of a slightly mysterious galaxy with a rather evocative name. Messier 64 is also known as “The Black Eye Galaxy” or “The Sleeping Beauty Galaxy”, and it's a really neat celestial sight. It is a spiral galaxy located in the constellation Coma Berenices (Berenice's Hair, named after the legend of Queen Berenice II of Egypt, her missing sacrificial hair, and a quick-thinking court astronomer. But you can read that story for yourself at the link up there).

Messier 64, the Black Eye Galaxy, in Coma Berenices.

M64 gets its name the Black Eye Galaxy from its appearance in a small telescope. This is mainly due to the massive clouds of dust circulating through it, especially the prominent band silhouetted in front of the bright galactic nucleus, which I've seen myself through a moderate-size telescope. If it weren't for the dust clouds in the outer regions of the galaxy blocking most of the light, M64 would be a lot brighter.

Surprisingly, given its large apparent size, the distance to M64 is not very well known. The best figures I could find suggested a distance of 17-19 million light-years, but there are estimates ranging from 12 to 40 million. Given its redshift and applying the Hubble Law would give a rough distance of about 16 million; however, M64 sits on the outskirts of the humongous Virgo Galaxy Cluster, which gives it an unknown extra component to its radial velocity that makes the Hubble Law only very roughly approximate. Since even 40 million light-years is essentially just down the block in the cosmic neighborhood, it's rather surprising that the distance isn't known more accurately, as the Cepheid variable stars used as standard candles for determining distance in nearby galaxies ought to be visible. One possible reason the distance isn't known better is that to date no supernovae have been observed in M64. One of those would definitely help pin down the distance.

M64 is about 80,000-90,000 light-years across, similar in size to (about 10% smaller) than our own Milky Way Galaxy (about 100,000 light-years across). One extremely interesting feature of this galaxy, however, is that the innermost 6,000 light-year-across region seems to be rotating in the opposite direction to the rest of the galaxy. This is quite unusual, and may hint at a possible galactic merger sometime in the galaxy's past. At the border, the differently spinning clouds of gas may be colliding with each other, possible spurring a wave of star formation. This certainly isn't your run-of-the-mill spiral galaxy. (Though to be fair, pretty much every spiral galaxy is unique in some way.)