A piece of Mars: This scene (3.9×2.5 km or 2.4×1.6 mi) shows a surface carved by two different winds: one blowing from the right and one blowing from the bottom right. They’ve formed overlapping sets of streamlined rocks called yardangs. Can you tell which set of yardangs was formed first? It’s a little more complicated than it may first appear. (HiRISE ESP_037156_1800 NASA/JPL/Univ. of Arizona)
ENCORE We’ve all hit the snooze button when the alarm goes off, but why do we crave sleep in the first place? We explore the evolutionary origins of sleep … the study of narcolepsy in dogs … and could novel drugs and technologies cut down on our need for those zzzzs.
Plus, ditch your dream journal: a brain scanner may let you record – and play back – your dreams.
And, branch out with the latest development in artificial light: bioluminescent trees. How gene tinkering may make your houseplants both grow and glow.Guests:
- Emmanuel Mignot – Professor of psychiatry and behavioral sciences, and director of the Stanford Center for Sleep Sciences and Medicine, Stanford University
- Kyle Taylor – Molecular biologist at Glowing Plant
- Jerry Siegel – Neuroscientist and professor of psychiatry, the University of California, Los Angeles
- Jack Gallant – Professor of psychology and neuroscience, University of California, Berkeley
First released May 27, 2013.
A piece of Mars: The two shadowed hills in the upper part of this frame (497×373 m or 1631×1224 ft across) rest on a flat plain covered in large ripples. On the plain the ripples are aligned north-south, formed perpendicular to a wind blowing from the east (right). But those hills block the wind and turn it, so that the ripples between the hills change direction. This is how windblown landforms can be used as wind vanes in remote places (like on Mars). (HiRISE ESP_037188_1835, NASA/JPL/Univ. of Arizona)
You think your life is fast-paced, but have you ever seen a bacterium swim across your countertop? You’d be surprised how fast they can move.
Find out why modeling the swirl of hurricanes takes a roomful of mathematicians and supercomputers, and how galaxies can move away from us faster than the speed of light.
Also, what happens when we try to stop the dance of atoms, cooling things down to the rock bottom temperature known as absolute zero.
And why your watch doesn’t keep the same time when you’re in a jet as when you’re at the airport. It’s all due to the fact that motion is relative, says Al Einstein.Guests:
- William Phillips – Nobel Prize-winning physicist at Joint Quantum Institute, a partnership between the National Institute of Standards and Technology and the University of Maryland.
- Bob Berman – Astronomy writer and author of Zoom: How Everything Moves: From Atoms and Galaxies to Blizzards and Bees
- Michael Smith – Meteorologist, senior vice president of AccuWeather Enterprise Solutions, and author of Warnings: The True Story of How Science Tamed the Weather
A piece of Mars: Dunes outside the crater are straight but the ones inside the crater look like a spiderweb. Why? This image shows just how much the topography of a crater wall can affect the wind, which produces a much more complex set of dunes inside than out on the plains. (HiRISE ESP_037195_1625 NASA/JPL/Univ. of Arizona)
ENCORE Maybe goodbye isn’t forever. Get ready to mingle with mammoths and gaze upon a ground sloth. Scientists want to give some animals a round-trip ticket back from oblivion. Learn how we might go from scraps of extinct DNA to creating live previously-extinct animals, and the man who claims it’s his mission to repopulate the skies with passenger pigeons.
But even if we have the tools to bring vanished animals back, should we?
Plus, the extinction of our own species: are we engineering the end of humans via our technology?Guests:
- Beth Shapiro – Associate professor of ecology and evolutionary biology, University of California, Santa Cruz
- Ben Novak – Biologist, Revive and Restore project at the Long Now Foundation, visiting biologist at the University of California, Santa Cruz
- Hank Greely – Lawyer working in bioethics, director of the Stanford Center for Law and the Biosciences at Stanford University
- Melanie Challenger – Poet, writer, author of On Extinction: How We Became Estranged from Nature
- Nick Bostrom – Director of the Future of Humanity Institute, Oxford University
First released April 29, 2013.
These two papers by J.T. Wright’s group were posted today on astro-ph
The Ĝ Infrared Search for Extraterrestrial Civilizations with Large Energy Supplies. I. Background and Justification
J. T. Wright, B. Mullan, S. Sigurðsson, M. S. Povich
The Ĝ Infrared Search for Extraterrestrial Civilizations with Large Energy Supplies. II. Framework, Strategy, and First Result
J. T. Wright, R. Griffith, S. Sigurðsson, M. S. Povich, B. Mullan
Based on the analysis of WISE and Spitzer data, the authors concluded that “Kardashev Type III civilizations (a civilization that extracts fusion energy, information, and raw-materials from multiple solar systems) are very rare in the local universe”.
I remind you that we had a SETI hangout on this topic with this group, including as well Jill Tarter and Freeman Dyson in September 2013.
I look forward to reading about the search for Kardashev Type II civilizations from the same set of data.
A piece of Mars: What on Mars is this (the scene is 600×450 m, or 0.37×0.28 mi)? It can be hard to tell. The lines are ridges of windblown dunes or ripples, the dark gray stuff is active sand blowing between the dunes, and the underlying bedrock is pale tan. But if your eyes can’t make sense of it all, just sit back and enjoy the pretty patterns of Mars. (HiRISE ESP_037161_1785, NASA/JPL/Univ. of Arizona)
Who’s watching you? Could be anyone, really. Social media sites, webcams, CCTV cameras and smartphones have made keeping tabs on you as easy as tapping “refresh” on a tablet. And who knows what your cell phone records are telling the NSA?
Surveillance technology has privacy on the run, as we navigate between big data benefits and Big Brother intrusion.
Find out why wearing Google Glass could make everything you see the property of its creator, and which Orwellian technologies are with us today. But just how worried should we be? A cyber security expert weighs in.
Also, the benefits of an eye in the sky. A startup company claims that their suite of microsatellites will help protect Earth’s fragile environment.
And Gary catches a cat burglar!Guests:
- Robert Gehl – Professor in the Department of Communication, University of Utah. His article, “A Mind Meld with the Surveillance State” appeared in an online issue of The Week.
- Hal Rappaport – Technology consultant for businesses, author of the paranormal thriller Hath No Fury: The Lesson of Three Book One. His article, “7 Sinister Technologies from Orwell’s 1984", appeared on the SyFy Channel’s online magazine.
- Susan Landau – Professor of cyber security policy at Worcester Polytechnic Institute, author of Surveillance or Security?: The Risks Posed by New Wiretapping Technologies and Privacy on the Line: The Politics of Wiretapping and Encryption.
- William Marshall – Physicist, Planet Labs
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.