Monday, September 26, 2011

More Thoughts on the Possibility of Superluminosity

My last post on the possibility of neutrino superluminosity rather surprised me with the amount of feedback it got, considering I put it together on the spur of the moment and hadn't really had time to think about it too much. But it's a good kind of surprise, because it shows people are interested in physics, and that makes me happy. Because really, how can you not be interested in physics? It's so fascinating! But I digress...

Anyway, this post is just intended as a bit of an expansion on my previous post, with some things I've thought of or had introduced to me in discussion over the weekend. It's important to keep in mind the way the experiment was conducted: basically, the Large Hadron Collider at CERN produces bursts of neutrinos which are detected at the OPERA detector about 730 kilometers away. These neutrinos are produced in bursts when protons slammed at high speeds into a target create pions and muons that then in turn decay after a random time into neutrinos. It's these bursts that OPERA actually detects. The time between the emission of a burst and its detection is then divided into the distance between the LHC and the detector, and the answer comes out to be about 60 nanoseconds (that's 60 billionths of a second) shy of the time it would take light in a vacuum to travel the same distance. Let's analyze this setup a little closer...

1. Distance measurement. The distance between the points of emission and detection is not the kind of distance you go out and measure with a meter stick. As stated before, it's about 730 kilometers from one to the other, and that's as the crow flies. In reality, the straight distance between them is through the Earth's crust, so you have to take that into account, along with the fact that the Earth is not spherical, nor even smoothly deformed, but a complicated shape called a geoid. Finally, both the LHC and OPERA are quite a ways under the ground, so that needs to be kept track of, and the standard way to measure large distances -- using GPS -- doesn't work that far underground, so you have to measure from a point on the surface, and work your way down. Now, in 60 nanoseconds light travels almost exactly 18 meters, so the two would need to be about 18 meters closer than currently thought for this explanation to account for the discrepancy (at least, it would need to be that much is this is the only explanation; in reality it may be a combination of factors). On the one hand, when you're measuring a distance of 700 kilometers, it would be easy to miss 18 meters; on the other hand, the scientist appear to have done a lot of work measuring using some precise equipment, and claim to know their relative location much better than 18 meters. This is definitely something that could stand to be reviewed. Finally, as I mentioned before, the neutrinos are produced at random lengths along a tunnel at the LHC; while the scientists claim that it makes very little difference at what point in the tunnel the neutrinos are produced, I think a careful review of the math may be in order.

2. Time measurement. This is where it gets a bit hairy, in my opinion. Time is a notoriously tricky concept in relativity, especially coordinating time between two observers. Two events may be seen to happen simultaneously or sequentially, all depending on the relative motion between the observer and the events. Remember, the time difference we're talking about is tiny, only 60 nanoseconds. The scientists at OPERA claim to be have resolution down to 10 nanoseconds (plus or minus a few), but that's an awfully tiny number. There's another twist I've seen pointed out: GPS satellites use general relativity in order to be as accurate as possible, but if these neutrinos truly are moving faster than light, it indicates that there is something wrong with relativity as we know it, so how much can we actually trust the satellites?

The first two points were some of the ways I could see the measurements being off. These next points are various tests I thought of that would go a long way to determining what exactly is going on.

3. Measuring with light. One of the best tests I can think of would be send a light beam along the same path as the neutrinos and measure how long it takes. If your light beam ends up faster than it should be, it rules out that the neutrinos are traveling superluminally. It would indicate one of two things: either the measurements of either time or space are off, or there is some sort of strange spacial-temporal disturbance going on in the Earth's crust between CERN and OPERA (which I'll perhaps expand on in a later post, as this one is long enough already). Unfortunately, this test is out of the question because the path of the neutrinos is through solid rock, not vacuum.

4. Measuring the energy of a neutrino. This is one I'd really like to see, because instead of taking the estimated time of flight for the neutrino and dividing it into the distance to get the presumed speed, you could take the energy of a neutrino and from there directly calculate its speed. If that turns out to be a hair under the speed of light, as it most likely would, then you know for a fact that a) the neutrinos were not moving superluminally and b) that either your time or distance measurement is off. Sadly, I don't know if OPERA is capable of detecting the energy of a single neutrino -- in fact, I'm not sure it's currently possible at all. This test would certainly do a lot to eliminate the possibility of superluminosity, though.

5. Two-way measurements. This would also help a lot. One-way measurements of speed are difficult because of the relativistic effects I mentioned earlier. It's a lot more reliable to measure the speed of something going away and back, and simply dividing twice the distance by the time. Yet again, this test is impossible due to the way neutrinos interact with matter. To put it mildly, they don't. Hardly at all. In fact, billions of neutrinos from the Sun's core are passing effortlessly and unobtrusively through your body as you read this sentence, regardless of the time of day or night. You'd need a bar of lead over a light-year in length before you'd have a 50% chance of any one neutrino interacting with it. The only reason OPERA is able to detect the emitted neutrinos is because there are so many of them -- and it still probably misses more than 99%. For this reason, you can't fire a beam of neutrinos at a mirror and have them bounce back, like you can with light, making this yet another test that can't be performed. In its absence, simply firing a beam of neutrinos back along the same path would have to do, but even that can't be done, as there are only a few places on Earth capable of creating neutrino bursts, and they tend not to coincide with the locations of the detectors capable of detecting said bursts.

Any of the three tests proposed above would do quite a bit towards resolving what's really happening here, whether that be simple mis-measurement or a whole new era of physics. Of course, none of them are likely to be done anytime soon, although personally I think that measuring the energy of a neutrino would probably be the most likely and easiest. There is, however, one test that has, in a sense, already been done. When supernova SN1987a went off in the Large Magellanic Cloud in 1987, we detected a burst of neutrinos coming from it a few hours before the light became visible. While this might at first glance seems to support the superluminal neutrino theory, it is actually easily explained by our current theories of supernovae (when the core of a supernova collapses and initiates its destruction it releases a burst of neutrinos that have no trouble getting out through the outer layers of the star, while the energy and light from the explosion take a few hours to work their way to the surface). The neutrinos in the experiment, if they were traveling faster than the speed of light, were only going about 1 part in 40,000 faster. The LMC is about 160,000 light-years away, so if the neutrinos from that event exhibited the same behavior, they should have arrived 4 years before we saw the light from the supernova. This doesn't entirely disprove the superluminal velocity theory (there were only a few [two?] neutrino detectors working at the time, and it might not have been noticed), but it does seem to go against it. It would be amazingly useful to have another supernova go off somewhere visible within the Local Group so we could see if there were any detectable neutrino bursts from it that would fit with this, but this is, yet again, depressingly unlikely to happen in the near future (although it can't be ruled out! There's always hope...).

Of course, I don't want to end this post on such a depressing note. While none of these tests can be done at the moment, I wouldn't put it past some brilliant mind out there to think up some test that could be done, and which will help resolve the question (put a neutrino detector and mirror array out in space, then simultaneously fire a laster and a neutrino burst, maybe). Really, whatever happens will be interesting; either Einstein is proven correct yet again and relativity stands vindicated, or we enter the brave new world of post-Einsteinian physics, which I can only imagine would be just as exciting as the introduction of relativity and quantum mechanics. Speaking of QM, I haven't mentioned it at all in this post, but not because I haven't been thinking about it in relation to this experiment. But you'll have to wait for another post for that, I need to get some sleep now. A hui hou!

Most Massive Majestic Mountain

Saturday I went up to Mauna Kea to volunteer for a summit tour, and on the way up I just had to stop and take the following panorama due to the exceptional clarity in the Saddle region, which usually has clouds in it that would make such a view impossible.
This, ladies and gentlemen, is the most massive mountain on Earth, and second-most massive in the entire Solar System. It's also very nearly the tallest, beaten only by Mauna Kea and Olympus Mons on Mars. This... is Mauna Loa.

The name Mauna Loa means “long mountain” in Hawaiian, and it's not hard to see where the name comes from. This is, indeed, a long mountain. Mauna Loa is a shield volcano, and you can see just how gently it slopes up to its summit caldera (which isn't quite visible from the altitude this picture was taken at). Lava flows of varying ages and colors cover its flanks, while old growth forests of ʻōhiʻa lehua trees stand wherever they can establish themselves. All in all, it's one beautiful mountain.

Friday, September 23, 2011

On The Possibility of Superluminosity

The physics world is a-buzz this week due to a paper published by a group of scientists working at CERN that seems to show superluminal motion by neutrinos. To rephrase that for people who don't know what I'm talking about, the measurements made by a group of scientists seem to show some really tiny sub-atomic particle traveling faster than light. Which is to say, to be more concise, that Einstein would be wrong.

This is an intensely interesting time for physics, needless to say. According to the paper, neutrons produced at CERN in Geneva are detected at a detector called OPERA in Italy in such a manner that they seem to have made the trip in about 60 nanoseconds less than it would take light to make the same journey (light would be expected to make a trip the same length in about 2.43 milliseconds). Looked at one way, that's not very much, only about 1 part in 40,000 faster. But from another perspective, that amount is HUGE, because according to Relativity Theory, nothing that has mass (like neutrinos) should be able to travel faster than the speed of light in a vacuum, c. The constant c is an immensely important one in physics, equal to 299,792,458 meters per second, or about 186,000 miles per second (or 669,600,000 miles per hour). The whole “in a vacuum” part is very important, because particles with mass are known to move faster than the speed of light just about every day, but with a very important twist: it only happens in a medium such as air or water where the local speed of light is less than c. Nothing in nature has ever been observed to travel faster than c, more than 100 years since Einstein first advanced his revolutionary theories.

Until, possibly, now.

However, the safe money is still on the fact that this is a systematic error of some sort. I'm 99% confident that it will turn out to be something of the sort, and that there will be seen to have been no superluminal travel at all. Einstein's theories have been proven correct time and again for over a century now, and tie both into modern physics and back into classical electrodynamics with near-perfect fit. In fact, relativity makes it pretty difficult to accurately measure distances that are one-way only, because of the near-impossibility of establishing a consistent timeline; simply moving from one end of a measuring course to the other in order to clock how long it takes light to travel it causes your frame of reference to experience time dilation relative to an observer who is standing still. Ideally you'd measure the distance forward and back on the same track, but since there are only a few places in the world capable of producing neutrons like this, and the detectors to detect neutrinos don't correspond to them, that is unfortunately out of the question.

However. Having said that, there is still the fact that the other main support of modern physics, quantum mechanics, continues to not play nicely with relativity. And while I'm 99% sure this will turn out to be a measurement error of some sort, there's always that 1% chance that we are on the brink of a major revolution in physics. And I do mean major. This would overturn our conceptions of physics nearly as profoundly as did the introduction of relativity and quantum mechanics in the first place at the beginning of the last century. A whole lot of physics as we know it would have to either go out the window or be heavily modified. (The practical side of me notes that the job market for physicists might pick up dramatically if that were the case!) It's been several decades since the last really big, paradigm-changing discoveries in physics, and if history is any guide, we might be about due for a new one. The scientists who are reporting this are not some crack-pot theorists, and are as surprised at their findings as anyone. They've done some serious work at eliminating sources of uncertainty, and unless someone finds a pretty big flaw with their setup, it does look as if something is happening, whatever it may turn out to be.

Still, such speculation is putting the metaphorical cart before the horse at this point. As I said, this will most likely be resolved in a fairly pedestrian fashion, with no major implications. Although there is one possible solution that I thought of that would explain the results while still adhering to relativity, one that will be instantly familiar to anyone who's ever played Valve Software's beautiful gem of a game Portal. And that solution is, well, a portal. General relativity does allow the existence of wormholes, which are essentially the eponymous devices from Portal. Basically, something goes in one hole and immediately comes out the other, no matter the distance between them. As an example, consider taking a strip of paper 10 centimeters long and putting two dots, A and B, at either end. Next, fold the strip of paper over on itself so that the dots touch. Now while in two dimensions the dots are still 10 centimeters apart, in three dimensions there is very little distance between them, and if you poked a hole through both dots you would essentially have the equivalent of a two-dimensional wormhole (it would actually function in three dimensions, though). Similarly, general relativity provides us with four-dimensional space-time, and it's not inconceivable that it could be ‘bent’ in an analogous fashion.

(By the way, if you have never had the immense pleasure of playing Portal, you should remedy that as soon as possible. I don't have time for a full review right now, but I firmly believe Portal is one of the most innovative computer games ever made. It's a thinking person's game, which is one reason I love is so much. Basically you get to move the two ends of a wormhole around, and use it to solve puzzles in a first-person view that it is nearly impossible to describe in a manner that gives it credit without spending a couple hundred words on it. Which I will do in a later post.)

The reason we don't see wormholes all around us is because they are unstable; they require some sort of negative energy density to hold them open, or they collapse on themselves and close off. No one has yet figured out how to have such a negative energy density, so they remain as yet theoretical entities. Considering that the neutrinos passed through over 700 kilometers of the Earth's crust on their journey, it's highly unlikely they encountered any regions of negative energy density either, but it's an interesting idea...

Actually, one test that would be very, very helpful to run would be to send photons along the same path the neutrinos take and see if they, too, show up 60 nanoseconds earlier than they're ‘supposed’ to, which would mean that it's not the neutrinos moving superluminally, but some sort of bent-space effect. Alas, such an option is unavailable to us because while neutrinos can move almost unhindered through the solid rock of the mantle, light can do no such thing, so that test is sadly out of the question right now.

Wednesday, September 21, 2011

Globular Cluster Photo Series (Part 12): M80

Today for your perusal I have an image of the globular cluster Messier 80. This is a very populous cluster with several hundred thousand stars and also one of the more densely populated ones, as all those stars are contained in a sphere only about 95 light-years across. Given M80's appreciable distance of about 32,600 light-years from us that translates to a somewhat smaller angular diameter of 10.0 arcminutes.
Messier 80 in Scorpius.
One curious incident in M80's history started around the time of the outbreak of the Civil War on May 21, 1860, when a nova (dubbed T Scorpii) was observed that briefly and spectacularly outshone the rest of the cluster (although it was still invisible to all but the most sensitive eyes with ideal dark sky conditions). Like all novae, this one was most likely the result of a white dwarf accreting mass from a larger binary companion star which eventually builds up to the point that it flash fuses extremely rapidly -- think an H-bomb with the mass of a small planet distributed across the surface of the star -- and blows away any gas that didn't fuse, leading to a massive brightening of the star. Novae in globular clusters are rather rare as a rule, with only a few others known. Interestingly, observations of M80 with the Hubble Space Telescope have only revealed two candidate binary systems for novae, a lot fewer than were expected based on models given the density of M80's core.

Tuesday, September 20, 2011

Globular Cluster Photo Series (Part 11): M5

Today for your consideration I have a picture of the globular cluster Messier 5 in Serpens Caput, the Head of the Snake. With a diameter of about 165 light-years this is one of the larger clusters of the Milky Way, and its gravitational pull dominates a humongous volume of over 34 and a half million cubic light-years!

Messier 5 in Serpens Caput.
M5's apparent diameter of 23.0 arcminutes is also on the larger end of the scale for Milky Way globulars. This is despite its great distance of about 24,500 light years from Earth. The number of stars it contains is unknown exactly; it is estimated to be above 100,000, and possibly as high as 500,000 which would put it above the more famous M13 in Hercules. 

Being as bright and large as it is, it is perhaps not too surprising that M5 was discovered by the astronomer Gottfried Kirch 62 years before Charles Messier would rediscover it 1764 and make it famous. It contains 105 variable stars, a very large number for a globular cluster. These are what help pin its distance down so exactly.

One interesting thing I noticed about this cluster in comparison to the last cluster I showcased, M56, is the relative dearth of foreground stars in this frame. That's because seeing M56 requires looking through the disk of the Milky Way, while M5 is found by looking outside of it. It really does make quite a big difference!

Saturday, September 17, 2011

Yet Another Supernova!

This summer has been really good to supernova aficionados in the northern hemisphere, with two supernovae visible in low-power telescopes going off fairly close to each other within two months. You can see my picture of SN2011dh in Messier 51 in an earlier post in June and further down in this one, because today I have a picture of the more recent SN2011fe which showed up in Messier 101 on August 24th (though the picture is from September 2nd).
SN2011fe in Messier 101, the Pinwheel Galaxy.
Compare the above picture with this one I took of M51 and SN2011dh back in June:
SN2011dh in Messier 51, the Whirlpool Galaxy.
These pictures are fairly similar in terms of exposure time, both using several stacked exposures of 5 minutes each for the three color filters, although the second one used 5 minutes for the luminance filter while the first used only 1:40. And yet even with those slight differences, you can still see that the Whirlpool Galaxy is much more concentrated and easier to see than the Pinwheel, which has actually been stretched a bit to differentiate it from the background.

It would appear from a comparison of the pictures that SN2011fe is a bit brighter than SN2011dh. This may have something to do with the fact that the Pinwheel Galaxy is a little closer to us (21 million light-years instead of 24), but the imprecision in our knowledge of the distance to the Whirlpool Galaxy (plus or minus 3 million light years) means they could actually be at very similar distances to us. It's likely that SN2011fe is intrinsically more luminous than SN2011dh, and that has to do with the fact that they are two distinctly different types of supernovae.

SN2011dh was a type IIa supernova, which means it's the last dying gasp from a star several times the sun's mass. In contrast, SN2011 was a type Ia supernova, which means it came from a white dwarf in a binary system, with a mass known almost exactly: about 1.4 times the mass of the sun. The reason for the vast difference in energy output is because in a type IIa typically only a small percentage of the star's mass is ejected as debris, perhaps a few solar masses' worth. The remaining material is left behind as a neutron star, or, in some cases, a black hole. In contrast, a white dwarf undergoing a type Ia supernova explodes, completely, utterly, and finally. There is no stellar remnant left behind after one of these goes off. The uniformity in their masses before explosion make supernovae Ia valuable as standard candles in the universe for estimating distances to far away objects, and the fact that we now have one to study right in our backyard, as it were, is a great opportunity for astronomers.

Tuesday, September 13, 2011

Plenty o’ Python Packages

I feel like I've been talking about Python a lot recently, but I just can't help it. When you find such a useful tool it's only natural to want to tell other people about it. And yesterday I discovered a wonderful resource for anyone interested in Python: the Unofficial Windows Binaries for Python Extension Packages.

There are a few reasons I found this collection of dozens of Python packages significant. First, currently most ‘official’ Python packages tend to be for 32-bit versions of Windows. I have a 64-bit machine, however, and it's bugged me in the past that there weren't versions capable of taking full advantage of the improvements offered by the extra power of 2. The author of this site basically created 64-bit packages of his own for nigh-on a hundred different Python packages, usually for several different versions. Which brings me to my second point.

The Python 3.x line came out a few years ago, and for various reasons having to do with certain inefficient and old aspects of the language was made incompatible with previous versions. What this meant is that new versions of old Python packages had to be reworked, which can often take a long time. There are a few key Python packages that I've wanted to get for quite some time but which were not available for the 3.x line yet. I didn't want to be shackled into using an older version (which would, eventually, die out), so I held off on getting them. Anyway, the point is, many of the packages on this site have versions for the 3.x line that I didn't previously know about, despite checking the official sites every few months. I went on a bit of an installation frenzy Monday night as a result, and I'm itching to try out some of the new features of the packages I have now. Since several of the packages I got are bindings for various graphic-related tasks, you may get to see some of my experiments sometime in the future.

Monday, September 12, 2011

FluxClassify.py

This weekend I wrote my very first program with a graphical user interface (GUI, often pronounced "goo-ey"). It's a program to help me classify the thousands of spectra we have for our research project. After several months of effort, Dr. Takamiya finally decided that we couldn't rely on the computer to make determinations about the presence or absence of a particular spectral line because it produced too many false positives. It's  one of those jobs that are just better handled by a human eye and brain.

Anyway, since we have around 30,000 spectra to classify, I decided that I really needed a program that would allow me to work in more than one dimension at once, so I got to work learning wxPython and produced FluxClassify over the weekend. The version you see below is version 0.2, the first version with all the features needed to produce workable results.
FluxClassify version 0.2.
As you can see it's a fairly simple program, despite being over 1,200 lines long. Most of those lines are extremely repetitive ones dealing with the hundreds of checkboxes on this thing, so I actually wrote some other code to write that part for me. I think I only actually wrote maybe 100-150 lines of the code by hand. Each of the numbered checkboxes represents one of the 225 spectra in a cube file. The ones along the top check or uncheck an entire column, while the one labeled "Check All" does exactly what it says.

WxPython is basically a program that works with an existing Python installation (only versions 2.4-2.8 as of this writing, sadly) to provide wrappers for the wxWidgets library that provides a native look and feel for programs written in it no matter what platform they're implemented on. It's pretty cool, since it automatically includes such Windows 7 features as automatically expanding to fill half the screen when I drag the program to one side of my desktop.

...And looking at my screenshot here I just realized that I have both columns and rows labeled as columns. Time for version 0.2.01! A hui hou!

Wednesday, September 7, 2011

Globular Cluster Photo Series (Part 10): M56


Last Friday while I was up at the Vis the weather was nice enough for me to be able to take the following picture for my globular cluster collection:

Messier 56 in Lyra.
This is Messier 56, a fairly average globular cluster located 32,900 light years away from us in the direction of the constellation Lyra. It is about 84 light years across, comparable to many of the other clusters I've photographed, and because of its distance it covers a fairly small 8.8 arcminutes on the sky (a little less than a third the size of the full moon).

There isn't that much interesting about this cluster, according to the sources I looked at. There are about a dozen variable stars known in it, a decent number but nowhere near the 112 found in Messier 15. The most interesting piece of information I found about it is that it is approaching us at the high velocity of about 145 km/sec. Other than that, not much to say about it, yet another celestial jewel in the collection.

Sunday, September 4, 2011

Atmospheric Aquiline

Today I have a rather stunning image (if I say so myself) that I apparently took back in October 2009. I say that because I don't remember reducing the data, and yet I discovered it today sitting in a folder about 90% of the way to being finished. So I finished it, and it turned out to be quite a beauty.
Messier 16, the famous Eagle Nebula in Sagittarius.
This is the famous Eagle Nebula, entry #16 in Charles Messier's famous list of not-comets. It is a place of stellar birth, where clouds of gas and dust are contracting into new stars. The faint red glow you see throughout the region comes from hydrogen excited by the many young, hot, massive stars in the area which are emitting copious quantities of ultraviolet light. The red light is called hydrogen-alpha by astronomers and has a wavelength of 656.28 nanometers. It comes about when the electron of a previously excited hydrogen atom jumps down from the third shell of orbitals surrounding the nucleus to the second, releasing a photon of red light in the process.

The Eagle Nebula achieved stardom (ha!) mainly after 1995 when an iconic picture of it was taken with the Hubble space telescope that focused on the dark dust lanes seen near the center. These became known as the Pillars of Creation, and are believed to be locations where stars are actively being born.

If you're wondering why it's called the Eagle Nebula, as with most such names it works better if you're looking at it through a moderately-sized telescope. You can kind of see it in deeper images that reveal more of the outlying details, as well.