There is little that is cooler than robots on mars doing science. Human space agencies have been sending probes to the surface of various planets (and the Moon) for years now, with the full range of failure and success. But the last decade or so has seen space robots such as Mars Curiosity Rover sciencing the shit, as they say, out of the planet Mars.
Emily Lakdawala, of the Planetary Society, is a planetary geologist and science communicator who knows a lot about driving rovers. It turns out that this is all very complicated, and when science gets big, expensive, high stakes, and complicated, it isn’t uncommon to find a diminishing number of individuals with a sufficient handle on all its aspects that they can explain most things to most people most of the time.
Emily’s framework for science communication is not that different from my own. I’m a scientist who likes to talk to non scientists at a level or two above the press release, and that’s what Emily does on her blog.
So, for all these reasons, Mike Haubrich and I were very happy to have the opportunity to interview Emily on Ikonokast.
I find it interesting that some people are expressing difficulty in understanding what a gravitational wave is, as though everybody (who is not a physicist) has a perfectly good understanding of what any kind of wave is. We don’t need to go too deeply beneath the surface, as it were, to understand this well enough to be amazed at the discovery, but not well enough to get a job being a Gravitational Waveologist.
Imagine a perfectly flat pond. Imagine throwing a stone out into the middle of the pond. Now imagine ripples, tiny waves, spreading out from the point where the rock hit the pond.
Now imagine the smallest possible stone that could produce a visible wave on the water. It would be pretty small. The ripples would be pretty small.
Gravitational waves are just like that, but even smaller, so you can’t see them. Not that you would “see” them with your eyes, but rather, you can’t detect them, in any normal way.
They won’t make the moon wobble, or a bird fall out of the sky. You know about super sensitive satellites that orbit the earth detecting variations in gravity such as the decrease in the pull of a glacier on the nearby ocean when the glacier melts by way less than one percent, and that sort of thing. Gravitational waves are presumably passing through that satellite all the time, but it can’t detect them.
Since they had not been detected for a long time, it had not been 100% certain that they exist. However, evidence for their existence has been mounting, and they have, in a sense, been indirectly observed.
Gravitational waves were first postulated by Einstein as early as 100 years ago as part of his application of his General Theory of Relativity, though he later temporarily retracted the idea (but then put it back).
Russian scientists advanced ways of detecting them in the 1960s, and one scientist thought he had found them a bit later in time. Further methods were developed to try to see them. In 1974 one group detected the slowing down of a pulsar orbiting a neutron star in such a way that implicated “gravitational radiation,” and this work stood (and earned a Nobel Prize). That was probably the first actual “detection” of the waves, in a sense.
In the late 1970s, the LIGO project was started to build a gravitational wave detecting antenna. In 1996, the VIRGO project was started in Italy. The Germans had just built GTO600, and partnered with LIGO soon after.
Over the last five years, the LIGO wave detector was upgraded, and after a period of time being turned off, was started up again in September. And bingo, there was a gravitational wave. Detected. Probably.
Long ago, deep in space, two massive black holes—the ultrastrong gravitational fields left behind by gigantic stars that collapsed to infinitesimal points—slowly drew together. The stellar ghosts spiraled ever closer, until, about 1.3 billion years ago, they whirled about each other at half the speed of light and finally merged. The collision sent a shudder through the universe: ripples in the fabric of space and time called gravitational waves. Five months ago, they washed past Earth. And, for the first time, physicists detected the waves, fulfilling a 4-decade quest and opening new eyes on the heavens.
The discovery marks a triumph for the 1000 physicists with the Laser Interferometer Gravitational-Wave Observatory (LIGO), a pair of gigantic instruments in Hanford, Washington, and Livingston, Louisiana. Rumors of the detection had circulated for months. Today, at a press conference in Washington, D.C., the LIGO team made it official. “We did it!” says David Reitze, a physicist and LIGO executive director at the California Institute of Technology (Caltech) in Pasadena. “All the rumors swirling around out there got most of it right.”
The way you detect a gravitational wave is to place two objects some distance from a laser source. You hit both objects with the laser and measure the return time, which should be exactlyvthe same for each object. If either object moves, that might have been because of a gravitational wave.
Obviously objects are going to move. Temperature changes, vibrations in the earth, all those things, can cause the objects to vibrate or move in some way. So you figure all that out and make all those things impossible. Also, the objects have to be really far out in order to get a signal. In the case of LIGO, the objects are four kilometers out from the laser source.
Yes, there is a reason that LITO was first funded in 1979 and only now has a result!
Now, here’s the part I don’t like. I don’t like the fact that the device was turned off and upgraded, then, very soon after being turned on, found a gravitational wave, and apparently hasn’t found another since then. I’m worried that this is similar to when CERN detected faster than light neutrinos. Everybody knew there were no faster than light neutrinos, but the instruments detected them anyway. Eventually, it was discovered that something was going on with the way the instruments were wired up that made the detector wrong.
“I think it’s very convincing. The reason they’ve waited months from the actual detection to report the event was so that they could check every possible source of artifact that might be something other than a real signal. So at this point, it’s well over 99% likely that the detection is real. Remember that the detection was made by both LIGO sites — Louisiana and Washington — and the delay between the two signals agrees with the light travel time. As to the “coincidence” — it depends on how rare or common these events are. Currently, no one has a good prediction for how often 2 black holes should collide and merge somewhere in the universe. If such events are very rare — e.g., one every 10 years or one every century — then it would indeed be a surprising coincidence. But if these events happen, say, once a year or more, then we’d expect to get a signal within a few months of starting a machine like this. The real test, then, will be whether other similar signals are detected over the next few years. I suspect they will be, and so it will turn out that these events are relatively common…”
Is there something wrong with the LIGO detector?
See the link to Science Magazine above for discussion of how hard the team worked to eliminate alternative explanations. Quite a bit, and quite convincing. But the gravity of this situation, this new discover, is so great that it may be good to retain a small amount of healthy skepticism.
By the way, don’t confuse “gravitational waves” with “gravity waves.” Going back to the pond, the ripples or waves on the water. Those are technically called gravity waves, as are some of the patterns we see in clouds. This is simply wave energy within a gravitational field. Gravitational waves are a totally different thing.
This month is the twentieth anniversary of the discovery of exoplanets, which are really just planets that are not in our solar system. (Frankly, I dislike the term exoplanet. It is so solarcentric.)
When you think about it, the discovery of planets outside our solar system (we need a word for that) is a special thing. On a graph of how expected and mundane a scientific discovery is vs. how exciting a scientific discovery is, these planets are distant outliers.
For years astronomers and cosmologists and others assumed that stars would generally have planets around them, or at least, this would often be the case. This is all part of the famous Drake Equation, best stated by Carl Sagan using the word “Billions” (with two b’s) over and over again. Like this.
OK, he didn’t really use “Billions” a bunch of times. But he might have.
Anyway, Nature.com has a nice set of infographics on the topic, one of which I’ve posted above. The rest are here.
Skylab came up in conversation the other day. And then I ran into Amy Shira Teitel’s video. So, naturally, a quick blog post.
Skylab was brought down, ultimately, by interaction with the upper reaches of the atmosphere, which was in turn made more likely by solar activity. But, both the nature and extent of solar activity of this type, and its effects on the atmosphere, were not understood when Skylab was being designed and deployed. Indeed, understanding this set of phenomena was a contribution made by Skylab science. Had Skylab been launched after, rather than before, this was better understood, it may have been put into higher orbit, or it may have been equipped with boosters (like the International Space Station is) to periodically raise the orbit.
Anyway, eventually, the orbiting research lab came down, and you may (or may not) remember all the press, the jokes, the anxiety, the fun…
Anyway, Amy has this piece on what NASA did and didn’t do about Skylab’s demise.
Short answer: Pluto has only two of the three necessary characteristics to be called a planet. Pluto has not cleared its neighborhood, or orbit. But, of course, there are additional details.
The simplest reason that Pluto is not a planet is that planet experts say so, and this is their job. But you may be looking for a more detailed explanation.
Let’s look at what defines a planet. This could be a very long and tedious discussion, because “planet” is an ancient concept used long before scientists knew very much about them. Also, frankly, in many areas of science the definition of a thing, perhaps counter-intuitively to non-scientists, is often pretty irrelevant to its study. Definitions that change over time that are never quite in line with the phenomenon being observed, etc. may seem like an impediment to science, but they often are not. The definition of a “gene” has changed dramatically as we’ve learned more about them, but this shifting description has not hampered genetic research. To some extent this may be the same with planets. A “planetologist” who studied Pluto back when it was still counted as a planet would not have to find a new job when our solar system went from 9 to 8.
The International Astronomical Union has settled on a set of definitions of solar system bodies, which includes planets, dwarf planets (which are mostly minor planets), small solar system bodies, trans-Neptunian objects which also might be called plutoids (those are also minor planets) and some small solar system bodies (including some comets) and satellites, and satellites are, of course, things that go around things that are not the Sun. Confused? Probably, but that is not a big problem because while these various identified flying objects have complex overlapping categorical status, one type of object does not. Planets are planets and they are not anything other than planets.
To be a planet, you have to be in orbit around the Sun. This would rule out the Moon, which, if it was in orbit around the Sun instead of the Earth, could well be a planet.
To be a planet the object has to have sufficient mass to have been shaped by gravity to be (mostly) a globe. This depends on various things so at the low end of the mass spectrum there will be different masses and different sizes of things that don’t quite make it to globular status.
To be a planet the object has to have cleared its orbit. In other words, as an object orbits around the sun, it is likely to bump into other objects. Over a period of time, the object has finished bumping into everything it is likely to bump into, and thereafter has only a low probability of bumping into something. That does not rule out something bumping into the object, of course.
A globe shaped object that goes around the sun but that has not cleared its orbit is classified as a “dwarf planet.” This is of course historically contingent. In the early days of a solar system, perhaps there would be large star-circleing round things that have not yet cleared their orbit. This speaks to the strangeness of definitions alluded to above. The definition we use today to classify our solar system’s objects applies to a solar system developed to the extent ours is developed. The IAU nomenclature would probably need revisions if applied to all planetary-star systems in the Universe.
This scheme is not without its critics and there is indeed debate. Some of that debate is a bit nitpicky but still interesting. For example, Alan Stern, with NASA, notes that many planets have not really cleared their orbit, noting in relation to the Pluto controversy, “If Neptune had cleared its zone, Pluto wouldn’t be there.” Yes, apparently heavenly bodies have irony.
Anyway, as implied, Pluto is not classed as a planet because it has not cleared its orbit. Therefore it is a Dwarf Planet. Since it is far away (farther than Neptune) it also gets classed as a Trans-Neptunian Object. Furthermore, it is a Plutoid. That is simply a newer term applied to Trans-Neptuina dwarf planets.
The term Plutoid, then, refers to a dwarf planet, which for various reasons is apparently always specifically an ice dwarf, which is a trans-Neptunian body (orbiting most of the time beyond Neptune) that is sufficiently massive to be shaped like a globe. This term, plutoid, is officially adopted A plutoid or ice dwarf is a trans-Neptunian dwarf planet, i.e. a body orbiting beyond Neptune that is large enough to be rounded in shape. The term plutoid was adopted by the International Astronomical Union’s Committee on Small Bodies Nomenclature, but not by the working group on Planetary System Nomenclature. So you can use Plutoid or Dwarf Planet, or Ice Dwarf, depending on whom you wish to annoy.
Pluto, Eris, Haumea, and Makemake are the only known Plutoids. They are small enough and far enough away that more could be discovered.
Remember the last Olympics, during the parade, where instead of seeing the athletes march along grouped by country, we saw unidentifiable people who were all either taking selfies or grabbing videos of everything going on around them, but we couldn’t tell who they were because their cell phones were totally covering their faces? These days every time a thing happens and we see a pic or video of it, it seems, everybody else has got a cell phone in their face. I suppose that is how we manage to have pics or videos of everything that ever happens.
The above image is part of the plaque attached to two Pioneer Spacecrafts in order to show aliens, should they come across either of the space probes, what humans look like. But edited for accuracy.
Also note that these humans are not fully evolved because they have not yet learned to turn the cell phone sideways to get a better picture, especially when taking videos.
Suddenly and for the first time I saw Amanda as a little child wide eyed with both awe and fear, among other children some sitting on the floor, some in chairs, some standing behind desks, eyes trained on a TV monitor and their teacher as the sudden realization dawned on all of them that the Space Shuttle Challenger had been consumed in a fiery, deadly explosion.
The teacher on board seemed to have been incinerated before their very eyes. As the explosion developed, shooting out huge arms of smoke, and the voice-over began to acknowledge that something was wrong, NASA’s space program was suddenly transformed, in the eyes of the innocent little children of America almost all of whom were watching the event live, from a somewhat interesting science project to a place where teachers went to die. Seventeen percent of Americans saw it live, 80% learned of it within 60 minutes after it happened.
I had never really visualized Amanda as a little girl before, but a few years ago when this came up, on an earlier Anniversary of the Challenger explosion, this image formed as a lump in my throat.
I’m a few years older than Amanda, so my experience was a little different. I had just returned form the Congo. I had borrowed a car … a Laser, which is a sort of sports car … and driven downtown to a friend’s apartment over an Italian restaurant and tavern, and parked it on a snow bank out front. That’s normal for Upstate New York. By the time morning came, the car was more than a little stuck, so I called Triple-A to pull it out.
I made the call from the tavern, and while doing so I noticed that the Challenger launch was being shown on the TV. So I stood at the bar and watched the launch. And the explosion. When the tow truck came, I mentioned to the driver that the Challenger had just exploded. He thought for a moment and said, shaking his head slowly, “You’re not gonna get me on that thing. No sir!” I thought … yeah, that might be a tough sell from this point forward.
It is said that when NASA started the Shuttle program, they made an estimate of risk of death to those who would be on board. Given the number of flights and the number of deadly events and the number of those killed, they’re apparently right in the expected range. I’ve not been able to confirm that estimate.
In any event, it turns out that space travel is dangerous. We recently remembered the tragic death of three astronauts on the launch pad, during a test, which came to be known as Apollo 1. In a few days from now, we’ll have the anniversary of the deadly destruction of the Columbia shuttle during re-entry. (Phil Plait has a few thoughts about this, here.) Four cosmonauts died during space missions as well.
Story Corps has a video about Ronald McNair, one of the scientists on the Challenger:
Amy Shira Teitel has a summary of January’s historic events in space travel:
Why is it great? Well, speaking as a Gemini (not my horoscope sign, but the space program going when I first gained sentience) …
<li>First, it is big, fast, cool looking. It actually looks like a rocket that might have been designed a decade before they ever actually made any rockets. It is almost Deco.</li>
<li>Second, they got a guy from the 1960s -- with that slightly, nasal, black and white voice people spoke in back then -- to call the <del datetime="2014-12-06T02:10:27+00:00">race</del> <em>launch</em>. </li>
<li>Third, Orion is really good at taking selfies. </li>
<li>Fourth, it didn't take long. The whole thing was like literally tl;dr.</li>
Oh, and fifth: It worked! Didn’t blow up or anything!
Apparently, the rocket that shot this unit into space is small compared to the one they’ll be using in the future. (More info on the project here.)
Have you heard the comet singing? From the Rosetta Blog this press release:
Rosetta’s Plasma Consortium (RPC) has uncovered a mysterious ‘song’ that Comet 67P/Churyumov-Gerasimenko is singing into space. RPC principal investigator Karl-Heinz Glaßmeier, head of Space Physics and Space Sensorics at the Technische Universität Braunschweig, Germany, tells us more.
Artist’s impression of the ‘singing comet’ 67P/Churyumov-Gerasimenko. Credit: ESA/Rosetta/NavCam
RPC consists of five instruments on the Rosetta orbiter that provide a wide variety of complementary information about the plasma environment surrounding Comet 67P/C-G. (Reminder: Plasma is the fourth state of matter, an electrically conductive gas that can carry magnetic fields and electrical currents.)
The instruments are designed to study a number of phenomena, including: the interaction of 67P/C-G with the solar wind, a continuous stream of plasma emitted by the Sun; changes of activity on the comet; the structure and dynamics of the comet’s tenuous plasma ‘atmosphere’, known as the coma; and the physical properties of the cometary nucleus and surface.
But one observation has taken the RPC scientists somewhat by surprise. The comet seems to be emitting a ‘song’ in the form of oscillations in the magnetic field in the comet’s environment. It is being sung at 40-50 millihertz, far below human hearing, which typically picks up sound between 20 Hz and 20 kHz. To make the music audible to the human ear, the frequencies have been increased by a factor of about 10,000.
The music was heard clearly by the magnetometer experiment (RPC-Mag) for the first time in August, when Rosetta drew to within 100 km of 67P/C-G. The scientists think it must be produced in some way by the activity of the comet, as it releases neutral particles into space where they become electrically charged due to a process called ionisation. But the precise physical mechanism behind the oscillations remains a mystery.
“This is exciting because it is completely new to us. We did not expect this and we are still working to understand the physics of what is happening,” says Karl-Heinz.
RPC may also be able to help in tracking Philae’s descent to the surface of 67P/C-G on 12 November, in tandem with the lander’s on-board magnetometer, ROMAP .
The contributing institutions to these instruments are:
RPC: Institutet för rymdfysik (IRF), Uppsala, Sweden; Southwest Research Institute (SwRI), USA; Institut für Geophysik und Extraterrestrische Physik, Technische Universität Braunschweig, Germany; Laboratoire de physique et chimie de l’environnement et de l’espace (LPC2E), Université d’Orléans, France, and Imperial College London, United Kingdom.
RPC-Mag: Institut für Geophysik und Extraterrestrische Physik, Technische Universität Braunschweig, Germany; Imperial College London, United Kingdom; Space Research Institute Graz, Austria
And here is the song:
And here is the alternate hypothesis for what is making this sound: