A piece of Mars: This 1018×1352 m (0.63×0.84 mi) dune-covered scene has split topography: the the bottom part is up on a plateau, and the upper part is in a broad valley. The dunes up on the plateau are smaller than the ones in the valley. Why? Probably because there was more mobile dune-building sediment in the valley to begin with: the dunes up high ran out of material and stopped growing, but the ones in the valley kept getting bigger. (HiRISE ESP_036795_1760, NASA/JPL/Univ. of Arizona)
Germs can make us sick, but we didn’t know about these puny pathogens prior to the end of the 19th century. Just the suggestion that a tiny bug could spread disease made eyes roll. Then came germ theory, sterilization, and antibiotics. It was a revolution in medicine. Now we’re on the cusp of another one. This time we may cure what ails us by replacing what ails us.
Bioengineers use advancements in stem cell therapy to grow red and white cells for human blood. Meanwhile, a breakthrough in 3D printing: scientists print blood vessels and say that human organs may be next.
Plus, implanting electronic grids to repair neural pathways. Future prosthetics wired to the brain may allow paralyzed limbs to move.
We begin with the story of the scientist who discovered the bacteria that caused tuberculosis, and the famous author who revealed that his cure for TB was a sham.Guests:
- Thomas Goetz – Author of The Remedy: Robert Koch, Arthur Conan Doyle, and the Quest to Cure Tuberculosis
- Jose Carmena – Neuroscientist and biomedical engineer at the University of California, Berkeley; co-director of the Berkeley-UCSF Center for Neural Engineering and Prostheses
- William Murphy -Bioengineer and co-director of the Stem Cell and Regenerative Medicine Center, University of Wisconsin, Madison
- Ali Khademhosseini – Bioengineer, Harvard Medical School, Brigham and Woman’s Hospital
A piece of Mars: Last December I blogged about a picture of a sand dune taken in early northern spring. This is the same dune, without frost, now that summer has come to the northern hemisphere and all the frost is gone. It’s quite a difference. Apparently the dunes are controlled by ice in the winter and by the wind in the summer. (HiRISE ESP_035997_2565, NASA/JPL/Univ. of Arizona)
The stars are out tonight. And they do more than just twinkle. These boiling balls of hot plasma can tell us something about other celestial phenomena. They betray the hiding places of black holes, for one. But they can also fool us. Find out why one of the most intriguing discoveries in astrobiology – that of the potentially habitable exoplanet Gliese 581g – may have been just a mirage.
Plus, the highest levels of ultraviolet light ever mentioned on Earth’s surface puzzles scientists: is it a fluke of nature, or something manmade?
And a physicist suggests that stars could be used by advanced aliens to send hailing signals deep into space.Guests:
- Paul Robertson – Postdoctoral fellow, Penn State Center for Exoplanets and Habitable Worlds
- Mike Joner – Research professor of astronomy at Brigham Young University
- Nathalie Cabrol – Planetary scientist, SETI Institute
- Anthony Zee – Theoretical physicist at the Kavli Institute for Theoretical Physics at the University of California, Santa Barbara
Here is another off the wall blog. You won’t find any physics in here…
Is GenY lost?
In a recent NYT article, Todd G. Buchholz and Victoria Buchholz, argue “sometime in the past 30 years, someone has hit the brakes and Americans—particularly young Americans—have become risk-aversive and sedentary.
University of New Hampshire management professor Paul Harvey says, GenY has a “very inflated sense of self” that leads to “unrealistic expectations” and “chronic disappointment.” If you want more silly expressions from old farts, read this article:
As for me, I identify very strongly with GenX; the previous ‘loser’ generation. In fact, generation X invented ‘loser.’ (Beck’s amazing anthem and L on the forehead). My birthday lands on the cusp of Baby Boomer and GenX, but I’ve clearly crossed the line into GenX I don’t live for or at my work. I think money isn’t everything. I’m not divorced, live within my means, and as a protest against pop culture, I stopped watching TV many years ago (although I do sometimes watch DVD’s). I had a ‘No Future’ sign on my office door in grad school, and my teachers were worried about it. I told them that with Reagan in office the Doomsday clock (Google it) was only 3 minutes to midnight (1984). And the Boomers complained that GenX was lazy, lost without a future (Ha! He says with bitter sarcasm), GenX can’t compete and they’ll never succeed like we (Boomers) did,
Well the joke is on the Boomers right now; they gradually fade away while GenX is taking over! Our president and I were born only 121 days apart! (My close approach to George Clooney, that’s right girls, is a mere 211 days). Thats right! GenX rules the world. Whole Foods plays GenX music (70′s – 90′s rock) right there in the aisles. As a GenX, I am the demographic for marketers — cause we have all the disposable income! Ha ha! Everyone treats me with respect cause I got a few gray hairs. No one complains about GenX anymore! It turns out that we’re pretty hard working and motivated after all! Ha ha!
So my message to my younger friends is to ignore oldsters who beat up your generation. You’re day will come!
Incidentally, I have a theory. I believe this “lazyness” ritual has been happening since the dawn of humanity. Every generation, so far, has been successful. We’re still around, aren’t we?
I’m not saying that GenY is not lazy. They’re young! This is how young humans are. Remember, the most impt. thing in your life when you’re young (say <30) is to find a partner and make babies. This ain’t easy; it requires a lot of talking, learning, and thinking about love and sex. Young people are too busy fulfilling the demands of their evolutionary drive to reproduce which after all, is a lot more fulfilling than being employee of the month at Starbucks.
ENCORE Face it – humans are pattern-seeking animals. We identify eyes, nose and mouth where there are none. Martian rock takes on a visage and the silhouette of Elvis appears in our burrito. Discover the roots of our face-tracking tendency – pareidolia – and why it sometimes leads us astray.
Plus, why some brains can’t recognize faces at all … how computer programs exhibit their own pareidolia … and why it’s so difficult to replicate human vision in a machineGuests:
- Phil Plait – Astronomer, Skeptic, and author of Slate Magazine’s blog Bad Astronomy
- Josef Parvizi – Associate professor, Stanford University, and clinical neurologist and epilepsy specialist at Stanford Medical Center
- Nancy Kanwisher – Cognitive neuroscientist, at the McGovern Institute for Brain Research at MIT
- Greg Borenstein – Artist, creative technologist who teaches at New York University
- Pietro Perona – Professor of electrical engineering, computation and neural systems, California Institute of Technology
First released February 25, 2013.
A piece of Mars: Using dunes to interpret the winds can be a tricky business. Here’s one reason why: most of the dunes here go from the upper left to lower right. But the ones inside the funky oblong crater go from the upper right to the lower left. Why? One of two reasons. Either the rim of the crater rotates the winds that blow inside, or the rim blocks one wind but lets in another that is less effective at making dunes outside. (HiRISE ESP_036934_1915, NASA/JPL/Univ. of Arizona)
ENCORE Think back, way back. Beyond last week or last year … to what was happening on Earth 100,000 years ago. Or 100 million years ago. It’s hard to fathom such enormous stretches of time, yet to understand the evolution of the cosmos – and our place in it – your mind needs to grasp the deep meaning of eons. Discover techniques for thinking in units of billions of years, and how the events that unfold over such intervals have left their mark on you.
Plus: the slow-churning processes that turned four-footed creatures into the largest marine animals that ever graced the planet and using a new telescope to travel in time to the birth of the galaxies.Guests:
- Jim Rosenau – Artist, Berkeley, California
- Robert Hazen – Senior staff scientist at the Geophysical Laboratory at the Carnegie Institution of Washington, executive director of the Deep Carbon Observatory and the author of The Story of Earth: The First 4.5 Billion Years, from Stardust to Living Planet
- Neil Shubin – Biologist, associate dean of biological sciences at the University of Chicago, and the author of The Universe Within: Discovering the Common History of Rocks, Planets, and People
- Nicholas Pyenson – Curator of fossil marine mammals at the Smithsonian Institution’s National Museum of Natural History in Washington D.C.
- Alison Peck – Scientist, National Radio Astronomy Observatory in Charlottesville, Virginia
First released April 22, 2013.
A piece of Mars: Curiosity has been trolling around on Mars for one martian year, so I think it’s time I posted an update on where it is and what it’s seeing. Right now (late June 2014), the rover is rolling across meter-sized ripples, heading south toward Mt. Sharp. In the near future there will be even more impressive ripples, and then finally the terrain will start to grow more interesting. I will post more of these in the months to come. (HiRISE ESP_029034_1750, NASA/JPL/Univ. of Arizona)
ENCORE It’s hard to get lost these days. GPS pinpoints your location to within a few feet. Discover how our need to get from A to B holds clues about what makes us human, and what we lose now that every digital map puts us at the center.
Plus, stories of animal navigation: how a cat found her way home across Florida, and the magnetic navigation systems used by salmon and sea turtles.
Also, why you’ll soon be riding in driverless cars. And, how to map our universe.Guests:
- John Bradshaw – Director of the University of Bristol’s Anthrozoology Institute, author of Dog Sense: How the New Science of Dog Behavior Can Make You A Better Friend to Your Pet and, most recently, Cat Sense
- Kenneth Lohmann – Biologist at the University of North Carolina – Chapel Hill
- Simon Garfield – Author of On the Map: A Mind-Expanding Exploration of the Way the World Looks
- William “Red” Whittaker – Roboticist at Carnegie Mellon University
- James Trefil – Physicist at George Mason University, author of Space Atlas: Mapping the Universe and Beyond
First released March 18, 2013.
I’ve been thinking about how to make a powerful weapon based on a relatively weak light transmitter which can be tuned in frequency. This could be the basis of what, in Star Trek, they call photon torpedos. The physics principle behind this kind of weapon is called “dispersion.” We commonly talk about oil “dispersing” on the surface of water, or pollen dispersing in the wind, but in physics we use this word to mean something very special and also very interesting.
Try this thought experiment. Take everyone on Earth (7 billion) and have them all stand side by side on a long straight platform perpendicular to and orbiting Earth’s equator. Have everyone face in the direction of the orbital velocity, using a local coordinate system where all people are on the x-axis at z=0. Give each person a baseball, and have them throw their baseball directly forward (in the direction of increasing z coordinate) at the same time. The baseballs leave the hands of every person (z = 0) at exactly the same moment (t=0). We won’t worry about the x or y spatial coordinates, only how far the balls travel in the z direction as time goes on. For the moment, we shall not be concerned about the rebound of the platform due to the ejection of balls. Perhaps there is a small rocket which cancels the momentum of the expelled baseballs, keeping the platform on its original course.
Some balls are thrown faster than others, depending on each person’s ability. At t=0, all the balls are clumped together at z=0. Later at time t=t1, the fast balls have moved farther from the platform than slow balls. The balls are now spread out, or dispersed, along the z-axis. With increasing time, dispersion increases: the distance between the fastest ball and the slowest ball increases with time. Thanks to Kepler’s laws, each ball will return to its starting point after executing one orbit of the Earth, provided the balls don’t hit the Earth (too slow) or escape Earth’s gravity (too fast). If we register the time when the balls arrive, we will typically find a small number of fast balls (thrown by major league pitchers) will arrive first. This is followed by a large “hump” or high density of balls arriving later with time corresponding to the speed of an “average” thrower, since average humans are more numerous than those with special skills. Finally, a small number of balls come dribbling in at the end, thrown by unusually weak throwers such as small children. Plotting the number of balls returning versus the time it takes to circle the Earth, we will find a bell-shaped curve. This bell curve looks a little like the envelope of a “wave packet,” if you have heard of that expression in quantum mechanics.
Now turn the classical baseball experiment on its head. After the first experiment, the experimenter knows the time required for each person’s ball to make one orbit. Starting with the slowest thrower (longest orbital time), this person throws their ball first, which comes back to the platform after known time T. Then, we ask the second slowest thrower to throw next, at just the right moment so that the second ball arrives back at the platform at time T. Carrying on with the third slowest, who throws next at the appropriate moment, we continue through all 7 million people until we reach the fastest thrower, who waits until the very last moment such that her ball arrives back at the platform again at the time T.
For the sake of argument, we use our rocket to steer the platform such that when the baseballs return after one orbit, they strike the platform from behind (but don’t hit any people). If just one baseball hits the platform, we don’t expect much of an impact. Even if 7 million baseballs arrive one by one, over a period of a year, each impact is small, so the people on the platform may feel a rumble but not even enough to make them fall down, since the impact of each ball is absorbed separately.
But in our second thought experiment, all of the 7 million balls strike the platform at exactly the same time. The instantaneous transfer of momentum is huge. Not only are people likely to fall down, but the platform itself may be distorted beyond its elastic limits and break in two, or into a thousand pieces. This might seem somewhat surprising, and it arises from the fact that the impact felt by the platform depends not only on the amount of momentum that is transferred from the balls, but also the time period over which momentum is transferred. Newton’s law of action and reaction explains this concisely:
Reactive Force on Platform = (change in momentum caused by balls) / (period of impact), or
F = dp / dt
where F = force, p = momentum, and t = time.
How does this discussion lead to a powerful weapon? Suppose we build a machine that can throw one baseball at a time at a certain speed, v. We can build a destructive weapon merely by preparing 7 billion copies of this machine and causing them to throw at exactly the same moment. Since all balls have the same speed, they arrive at their destination in a giant clump, obliterating the target. But this has two problems: 1) 7 billion are a lot of machines (expensive) and 2) the instantaneous power required to trigger all machines at the same time is extraordinary, and possibly so large that Earth technology cannot feasibly produce so much energy over such a short time.
So we build a different design with only one machine that is capable of throwing one ball after another with a small time delay dt, but each one having a different speed. The machine starts by throwing slow balls, and gradually increase the ball speed uniformly in proportion to (A n dt) where n refers to the nth ball thrown and A is a constant chosen depending on the distance to the target. With suitable choice of A, we ensure that every baseball arrives at the same moment, transferring large momentum in a small time and obliterating the target.
What have we gained? 1) Instead of building 7 billion machines, we built only one that is slightly more complicated (cheap). 2) Over any time period Adt, only the energy required to throw one ball is required. This is a dramatically smaller power level, which is extended over a long period of time. In total, about the same amount of energy is required for either of the above weapons, but the latter is astronomically cheaper and more energetically feasible.
Don’t get me wrong, I’m not a big fan of weapons. But I can’t help myself describing this particular use of physical “dispersion” since it is so fascinating.
This blog is already much too long, so we’ll very quickly skip to the quantum case, in which situation we make photon torpedos.
As described in an earlier blog, the space between stars (interstellar medium) is filled with an extremely thin gas, mostly hydrogen, with approximate 1% of hydrogen atoms being ionized into free electrons and protons, called plasma. When light travels through plasma, it picks up a tiny bit of the properties of matter: photons combine with electron motions into quasiparticles that look almost like photons but have a teeny tiny bit of rest mass. This rest mass depends only on the plasma density and not on the photon energy or frequency. Any particle with rest mass suffers dispersion. Even though all “pure” photons passing through vacuum travel with the same speed, c = speed of light, quasiparticle photons with rest mass can travel with any speed v, where (0 <= v < c), just like any other massive particle. This is what makes photon torpedos possible.
Set up a light generator, call it an idealized tunable laser that emits radiation into a region of the interstellar medium (ISM). Low frequency light, like radio waves, travel more slowly through the ISM because they carry less total energy, hence less kinetic energy as compared with their tiny rest mass. Optical light waves travel faster, since their kinetic energy >> rest mass. X-rays, and then gamma-rays travel even faster. As a reality check we note that astronomers can ignore the slow-down even in the optical frequency range since it is small. But the slow down is never zero, even for gamma rays.
Now we perform exactly the same process with light that we did with baseballs. We begin by emitting low-energy (low frequency) radio waves. These waves can travel much less the speed of light since their total energy is not much larger than their quasiparticle rest-mass.** A little later, the laser is tuned to a higher frequency with corresponding higher speed for photon travel. Later, higher and higher frequency waves are emitted. We adjust the time of emission of the different frequencies such that they all arrive at the target at exactly the same time, packing an astounding punch. The result is in perfect analogy to the baseball experiment.
** In a typical region of the interstellar medium,
the quasiparticle photon rest mass is 4e-18 eV. Oops! Did I just quote the mass in units of energy? Shame on my lazy physics habits. That should say 7e-54 kg. Despite being a small number, it is easily measured in astronomical observations.
Using only a single laser transmitter and by transmitting different frequencies at specific times, we can use a single machine to simulate the “impact” of a large number of identical machines shooting the same frequency at the same time. Also, the amount of power emitted by the laser is relatively small but carries on for a relatively long period of time. By using “dispersion” to our advantage, we cause all of that energy to arrive at the target in a short moment, packing a giant whallop far beyond the capability of a single-burst from the laser at one frequency.
So that is one way to make a photon torpedo. Or you can use electrons instead, or neutral H or He atoms, or even baseballs. All these weapons are always based on the same principle of dispersion, which is a common feature of every object that has rest mass. Which is everything.
I hope this stimulates some entertaining thoughts about dispersion.
A piece of Mars: This crater (290 m or 950 ft across) is crawling with all sorts of ripples and dunes. The wind mainly blows from the top to the bottom of the frame, and it is responsible for the wonderful textures in the dark gray sand. It has also formed larger, cream-colored ripples. The creamy and dark gray sand have taken turns burying one another, like vines competing for sunlight. (HiRISE ESP_034084_1655 , NASA/JPL/Univ. of Arizona)
You are surrounded by products. Most of them, factory-made. Yet there was a time when building things by hand was commonplace, and if something stopped working, well, you jumped into the garage and fixed it, rather than tossing it into the circular file.
Participants at the Maker Faire are bringing back the age of tinkering, one soldering iron and circuit board at a time. Meet the 12-year old who built a robot to solve his Rubik’s Cube, and learn how to print shoes at home. Yes, “print.”
Plus, the woman who started Science Hack Day … the creation of a beard-slash-cosmic-ray detector … the history of the transistor … and new materials that come with nervous systems: get ready for self-healing concrete.
(Photo is a model of the first transistor built in 1947 at the Bell Telephone Labs in New Jersey that led to a Nobel Prize. Today’s computers contain many million transistors … but they’re a lot smaller than this one, which is about the size of a quarter. Credit: Seth Shostak.)Guests:
- Lucy Beard – Founder of Feetz
- Mark Miodownik – Materials scientist, director of the Institute of Making, University College, London, and author of Stuff Matters: Exploring the Marvelous Materials That Shape Our Man-Made World
- Steve Nelson – Team K.I.S.S. Robotics, maker of Beer2D2
- Dan Lankford – Managing director, Wavepoint Ventures
- Ariel Waldman – Founder, Spacehack.org, global instigator of Science Hack Day
- Saurabh Narain – 12 year-old participant in Maker Faire
You’ve probably heard the word “photon” before, as in “photon torpedoes” popularized in the original Star Trek. “Photons” are what physicists call “light” or electromagnetic radiation, when it displays it’s particle-like behavior.
Think of the light from the Sun. The Sun (~6000 K) and emits light over a large range of frequencies. In space, satellites measure x-ray emissions, on Earth our eyes are sensitive to optical radiation and a radio-telescope like SETI Institute’s ATA see’s the Sun as an extremely bright object — the Sun emits radio waves too. We don’t often think about radio waves or x-rays as being made of the same stuff as ordinary light, but that is all there is to it. And everything from x-rays to radio waves can be described as if it were made up of particle photons in the quantum theory of light.
Photons are very special particles. Elementary particles like electrons, protons, neutrons or composite quasi-particles like atoms, molecules, ball-bearings, planets, stars, etc. share one important feature; they have mass. Rest mass. That is, if you stop an electron and weigh it, you’ll discover it has a measurable mass.
Photons in vacuum, lets call them “pure” photons, have no rest mass. If you stop a photon and weigh it… wait, you can’t stop a photon. Pure photons always move at the speed of light (duh!). If you subtract kinetic energy from a pure photon in an attempt to slow it down, it does not slow down, it just oscillates more slowly.
This is all very interesting, but how often do we come across “pure” photons in our universe? NEVER! Why? Because nowhere in the universe is there a perfect vacuum. Matter is dispersed everywhere. In the outermost reaches of space even in the vast gaps between galaxies, there is a tiny density of Hydrogen gas, possibly less than 1 atom per cubic centimeter. Even this much material is enough to disturb the properties of “pure” photons.
When a photon interacts with matter, two things happen : 1) it picks up “rest mass” and 2) it slows down. This happens because regular matter is made up of charged particles like electrons and protons (one each in a Hydrogen atom). When the electromagnetic wave passes an atom, it causes the lighter electrons to “jiggle” around the heavier protons, jiggling with the same frequency as the incident light wave. Momentarily, some of the photon energy is bound up in electron motion, but after a short time the electron releases the energy once more at the same frequency but with a small time lag. Matter imposes a “drag” on the photons, slowing them down. The same is true if light is passing through the space between stars, Earth’s atmosphere, a glass lens, a copper wire, and so forth.
How can photons, or light as we know it, travel slower than the speed of light? This sounds like a paradox. The answer is that photons passing through matter are no longer (pure) photons. The photons pick up a little bit of the material properties and the material picks up a little bit of the photon properties. Physicists say that the photons and oscillating electrons form a “quasiparticle” that travels nearly at the speed of light and carries a tiny bit of rest mass.
Now for the fun part. First of all, we’ve already discovered that everyday light really does not travel at the speed of light.
It is not possible to transmit light waves of arbitrarily low frequency. Suppose you go to a spot halfway between the Earth and Alpha-Centauri. You set up a large antenna and connect a radio transmitter that generates frequencies of, say, 0.001 Hz. That is one oscillation every 15 minutes, but never mind, there’s nothing to stop you from trying. What happens? Well, no waves are emitted. How can this be?
Because of the small amount of gas, especially ionized gas, between stars in our galaxy, the quasiparticle photon rest mass is equal to that of a pure photon with frequency >0.001 Hz. In a sense, you can try to generate waves with lower frequencies, but the surrounding space will “reject” these photons and they eventually re-enter the transmitter, cancelling out your attempted radiation. Photons with such low frequencies do not propagate. If you turn up your transmitter to oscillate just fast enough to exceed the rest-mass threshold of photons, then you will observe those photons travel very slowly, much slower than the speed of light in vacuum.
We can even imagine, within the boundaries of real physics, the concept of “slow glass,” invented by science fiction writer Bob Shaw in a story in Analog (1966) called “The light of other days.” In this story, a special kind of glass is invented such that optical photons take a long time, perhaps 10 years, to travel through a 1″ sheet of glass. Science fiction? Yes! But slow glass is possible.
Nothing, not even the light that provides us with sight every day, can travel as fast or faster than the speed of light in vacuum. But anything, including light, can be made to travel as slow as we like. This is the flip side of Einstein’s speed limit and allows for some weird possibilities. Perhaps we’ll explore more of these possibilities in a later blog.
A piece of Mars: Never mind the 4 m (13 ft) boulders that have fallen downslope, or the rippled sandy surfaces here. Look at those bright swirls in the ground. Those are the former interiors of sand dunes, which were trapped and incorporated into the bedrock (like dinosaur bones, but without so much rawr). The wind has been blowing sand around on Mars for a long, long time. (HiRISE ESP_036436_2645, NASA/JPL/Univ. of Arizona)
One day, coffee is good for you; the next, it’s not. And it seems that everything you eat is linked to cancer, according to research. But scientific studies are not always accurate. Insufficient data, biased measurements, or a faulty analysis can trip them up. And that’s why scientists are always skeptical.
Hear one academic say that more than half of all published results are wrong, but that science still remains the best tool we have for learning about nature.
Also, a cosmologist points to reasons why science can never give us all the answers.
And why the heck are scientists so keen to put a damper on spontaneous combustion?
Studies discussed in this episode:
Chocolate and red wine aren’t good for you after all
The Moon is younger than we thought
- John Ioannidis – Professor of medicine, health research and policy, and statistics, and co-director of the Meta-Research Innovation Center at Stanford University. His paper, “Why Most Published Research Findings are False,” was published in PLoS Medicine.
- Marcelo Gleiser – Physicist and astronomer at Dartmouth College, author of The Island of Knowledge: The Limits of Science and the Search for Meaning
- Joe Schwarcz – – Professor of chemistry and Director of the Office for Science and Society, McGill University, Montreal and author of Is That a Fact?: Frauds, Quacks, and the Real Science of Everyday Life
A piece of Mars: Which way did the wind blow here? You can tell by looking at the dune and its ripples. The slip face (the avalanching slope of the dune) faces downwind, so the strongest wind here mainly blows toward the upper left. But that’s not the whole story, because, like on Earth, martian winds are always shifting. Recent avalanching and some ripples on the slip face show that the most recent wind blew toward the top of the frame. The dune is 267×110 m (876×361 ft). (HiRISE ESP_036393_2650, NASA/JPL/Univ. of Arizona)
Communiqué de presse de l’Institut SETI et de CASCA
Monday, June 09 2014 – 12:15pm, PDT
Mountain View, CA -
Cette année a été intense pour les chasseurs d’exoplanètes, ces planètes autour d’autres étoiles. Une équipe d’astronomes de l’Institut SETI et du centre de recherche de la NASA Ames a découvert 715 nouvelles exoplanètes enfouies dans les données du télescope spatial Kepler. Ces nouveaux mondes qui tournent autour de 305 étoiles différentes, constituent des systèmes planétaires multiples, similaires a notre système solaire, lui-même constitué de huit planètes. L’annonce de cette découverte a été suivie par une nouvelle encore plus importante dans le monde de l’astronomie : la même équipe a annoncé la découverte de Kepler 186f, une planète de la même taille que la Terre qui tourne autour de son étoile dans la zone dite habitable. Cette decouverte constitue une étape essentielle vers la détermination de l’existence de planètes de type Terre dans la Voie Lactée.
Jason Rowe, astronome au SETI Institute, est à l’origine de cette étude. D’après lui, « ces résultats indiquent non seulement que les planètes de la taille de la Terre sont très répandues, mais également que les systèmes multiples peuvent contenir des mondes habitables ». Il souligne néanmoins que « la plupart de ces planètes tournent autour de leur étoile à une distance bien plus courte que la distance entre la planète Mercure et notre soleil. Nous commençons à peine à trouver des systèmes vraiment similaires à notre système solaire. »
Ce déluge de nouvelles exoplanètes s’est intensifié grâce à l’utilisation d’une nouvelle technique d’analyse appelée « vérification par multiplicité ». Les chercheurs ont pu vérifier l’existence de centaines de nouveaux systèmes planétaires à la fois, sans pour cela devoir analyser chaque système un par un. Basée sur une étude probabiliste, elle a permis de confirmer l’existence de ces systèmes autour des 150 000 étoiles observées par Kepler. L’analyse de cet échantillon a ainsi conduit les astronomes à cataloguer 715 nouvelles exoplanètes, portant le nombre total d’exoplanètes découvertes à ce jour à plus de 1 700.
« Ce travail nous a aussi permis d’en savoir plus sur ces systèmes. Ils sont remarquablement compacts et les orbites de ces planètes sont planes et circulaires, tout comme notre système solaire, » note Jason Rowe.
Le 17 avril, l’équipe de Kepler annonça la découverte de Kepler 186f, la première planète de taille similaire à la Terre se trouvant dans la zone habitable de son étoile, là où la température en surface pourrait permettre à l’eau d’exister à l’état liquide. Cette découverte marque une étape importante dans la détermination de la fréquence de planètes similaires à la Terre dans notre galaxie.
D’après David Black, président et PDG de l’institut SETI, « la découverte de ces nouveaux mondes potentiellement habitables dans notre galaxie suggère que l’existence d’une vie extraterrestre, quelque part dans le cosmos, est probable. »
La mission Kepler a cessé d’enregistrer des données en début d’année en raison d’une anomalie rencontrée avec deux de ses roues à réaction qui sont essentielles pour orienter le télescope de manière très précise. Le 20 mai, la NASA a néanmoins annoncé qu’une seconde mission, appelée K2, était sur le point de commencer. Le satellite Kepler a été reconfiguré afin d’utiliser la pression des photons solaires pour compenser la roue manquante et affiner son pointage, lui permettant ainsi d’observer un champ du ciel différent.
« Nous ne pouvons plus maintenir les observations de Kepler dans le champ prévu initialement » annonce Doug Caldwell, scientifique en charge de l’instrument Kepler au SETI Institute, « mais le télescope spatial a été construit par une équipe pleine de ressources et dont l’ingéniosité a permis à Kepler d’avoir une seconde vie. Le satellite cherchera dorénavant des exoplanètes dans une gamme d’environnement très variée, notamment dans des régions de formation stellaire. Nous allons très certainement en apprendre beaucoup sur la formation et l’évolution de notre propre système solaire. »
« Plus nous explorons notre galaxie et plus nous découvrons de mondes parmi les étoiles qui nous rappellent le nôtre » conclut J. Rowe.
Au sujet de l’institut SETI :
L’Institut SETI est une organisation de recherche multi-disciplinaire non lucrative, fondée dans le but d’explorer, comprendre et expliquer l’origine, de la vie dans l’univers, ainsi que sa nature et sa prévalence. Les chercheurs de l’institut rassemblent des expertises dans des domaines aussi variés que l’astrophysique, les sciences planétaires ou la biologie, les sciences sociales ou les sciences informatiques, ou encore le traitement du signal. Par l’étude du passé et du présent, les chercheurs peuvent ainsi entrevoir des bribes du futur. Nous sommes passionnés de découvertes, mais également du partage des connaissances, en tant qu’ambassadeurs scientifiques auprès du public, de la presse et du gouvernement. L’Institut SETI est un partenaire privilégié des agences gouvernementales, institutions académiques et plusieurs compagnies dans le monde entier.
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If you move with the times, you might stick around long enough to pass on your genes. And that is adaptation and evolution, in a nutshell.
But humans are changing their environment faster than their genes can keep pace. This has led to a slew of diseases – from backache to diabetes – according to one evolutionary biologist. And our technology may not get us out of the climate mess we’ve created. So just how good are we at adapting to the world around us?
Find out as you also discover why you should run barefoot … the history of rising tides … why one dedicated environmentalist has thrown in the towel … and an answer to the mystery of why Hawaiian crickets suddenly stopped chirping.Guests:
- Daniel Lieberman – Professor of human evolutionary biology at Harvard University, author of The Story of the Human Body: Evolution, Health, and Disease
- Brian Fagan – Emeritus professor of anthropology, University of California, Santa Barbara, author of The Attacking Ocean: The Past, Present, and Future of Rising Sea Levels
- Paul Kingsnorth – Environmental journalist and author of Real England: The Battle Against the Bland and The Wake. The profile of his retreat from environmentalism appeared in the “New York Times Magazine”.
- Marlene Zuk – Evolutionary biologist, University of Minnesota
A piece of Mars: Over time, windblown sand can wear down a surface. This isn’t so common on Earth, where water, ice, and life are more likely to change the landscape, but it’s typical of many places on Mars. Here, we see one moment in time, where neverending sand (blowing from bottom right to top left) creates a pattern on the surface and scours a hole around a resistant rock. (ESP_035558_1830, NASA/JPL/Univ. of Arizona)