Cosmic Diary by Gerry Harp
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.
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.
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.
This is part 3 and final installment in the Your Opinion Doesn’t Matter blog. Please read parts 1 and 2 for context.
In part 2 I divided spurious opinions regarding topics in SETI into 3 categories: science-free, Anti-scientific, and convicted statements of the “self evident.” Here we take up the last of these categories.
Convicted Opinions that are not so Self-Evident
Steven Hawking is the epitome of scientific hero. He overcame dramatic life challenges to become a peerless leader in the progress of general relativity theory of gravity and quantum mechanics. When it comes to theoretical gravitation, I’m not fit to tie his bootlaces. But he isn’t God. (I hear the jingling of sharpened spoons outside my window.) As far as I know! Speaking of intelligent life elsewhere, he said, “To my mathematical brain, the numbers alone make thinking about aliens perfectly rational.” I quote this only because it is convenient to me, ha ha! I’m about to say that Hawking isn’t the best source for information about ET.
Unlike many people, Hawking still has an imagination, “I imagine they [aliens] might exist in massive ships, … become nomads, looking to conquer and colonise whatever planets they can reach.” Whoa! Where did that come from? Possibly… from a science fiction movie? Proof that Steven Hawking is really a college undergraduate at heart. (jingle…) Ahem, that was just my little joke, Mr. Dr. Professor Hawking. Sir.
It is plausible that Hawking’s comment inspired this excellent book, penned by scientists** who really are expert*** in SETI issues. For the greater part, experts suggest that aliens are more likely to be altruistic — willing to help us out with no expectation of immediate reward — than predatory. For example, members of a predatory species that have conquered their planet will have only each other to prey upon. This is a state of unstable equilibrium. So they had better lose their predatory instincts fast, or annihilation is inevitable in the long run. Hence, the aliens are not likely to be purely predatory.
**By sheer coincidence, this book is edited by none other than Doug Vakoch, the director for interstellar message construction at the SETI Institute, with an office a few doors down from mine.
*** At least, as expert as anyone could be.
So, what do you think? It doesn’t matter! Whether aliens exist, or don’t, is a question that will someday be answered by science. Provided we don’t give up on the search for them.
This blog extends part 1 of a blog with the same title, and is followed by part 3.
Albeit imperfect, the radio search for extraterrestrial intelligence (SETI) tests a scientific question (hypothesis), “Did intelligent life get started anywhere else in the universe?” This a scientific question (not a matter of opinion), because it has a definitive answer (yes or no) that can be tested by observing nature (i.e. with our telescope). “Is there a God?” also has a definitive answer, but it is not scientific because we have no hope that observations of nature can answer this question. The God question falls into the realm of “opinion” (sound of jingling spoons) because it can be answered only by methods outside the scientific framework. (Crickets…, OK, that’s better!)
Malformed opinions about SETI topics can be broken down into 3 types : (1) science-free, (2) conflicting with science, and (3) strongly convicted statements of the “self evident” which aren’t, really.
Ignorance is bliss (science-free) Opinions
A very readable book (meaning that I could read it all the way through), “The Elusive Wow: Searching for Extraterrestrial Intelligence,” by Robert H. Gray discusses the “WoW!” signal, observed at Ohio State University in 1977. I am critical of “WoW!” because the signal did not even pass the candidate tests in the original experiment, so why should we believe it based on arguments made after the fact? A review on Amazon  speaks differently. It discredits Gray’s book with the argument that, signals from far away are very weak. Wow! That’s convincing. Especially compared with actual science showing that an Arecibo-like transmissions from nearby stars can be detected, right now, by us, if we look hard enough.
Anti-scientific Opinions (conflicting with science)
A certain blog  states that there are even (50-50) chances of finding intelligent life around the recently-discovered exoplanet Kepler 186-f. Remember, Kepler 186-f is a “goldilocks” planet orbiting a star 500 light-years from ours. 186-f is almost the same size as Earth, presumably a rocky planet and in a “hot” (that is, not hot) orbit around its star to keep the temperature just right (that is, possibly close to a temperature) where (microbial) life (as we know it) can flourish (that is, be not immediately destroyed). And then the life must be intelligent like us and be actively transmitting in our direction. 50-50 chance, huh?
In round numbers, all targeted SETI searches until now show that fewer than 1/1000 “likely” stars harbor planets that are intentionally beaming signals toward us.* We think 1/1000 is still a pretty big number compared to something like 100000000000 planets just in our galaxy. Even better, exoplanets discovered by the Kepler telescope and other probes show that most stars have planets, and somewhere around 1/5 of stars host “habitable” planets that are favorable for the evolution of life. Promising indeed. Even so, these probabilities don’t add up to a 50-50 chance of finding intelligence.
*Are you surprised that 50 years of SETI research can say no more than that? This actually shows how little effort (money) has been expended over the years to do SETI. Not for lack of scientific interest, but simply because scientists have to eat. Write your congressional representatives and urge them to support funding for SETI research.
If anyone wants to place a bet, we have insider information on Kepler 186-f, thanks to first author Elisa Quintana, a scientist at the SETI Institute. In the few weeks between submission of the paper and announcement of the discovery of 186-f, the SETI Institute pointed its telescope ATA at Kepler 186-f as much as possible (>8 hours / day) looking for technology-generated signals between 1-9 GHz. Sadly, our observations did not discover any evidence for artificial signals from that direction. So far.
This blog is continued in part 3.
Ha ha! The title should garner angry crowds bearing sharpened spoons*, chanting before my office window in Mountain View.
*Because spoons are the only tools their caretakers will allow.
Even the link is funny! An apparently reputable journal recently published results of interviews with 116 college undergraduates describing their scientific “opinions” about SETI (search for extraterrestrial intelligence). We leave aside the societal relevance of opinions from 18-23 year olds who’ve never worked a day in their life! (Uh oh, I hear jingling spoons again.) Ha ha, just kidding, all you large, young, and physically intimidating people attending their first years of college! The crucial results:
(a) 82.1% think it is important to have a space agency.
(b) 71.4% think the military should have the main role in the event of contact with an alien civilisation.
(c) 80% believe if we find aliens more advanced than us they will try to conquer us.
(d) 78% believe there is a chance we’ve been visited by aliens in the past.
From (d) we infer that most undergraduates received their foundational science education from science fiction movies. This helps explain the rest. I’m most worried about question (b). Should the military be the first of “diplomats” that aliens meet? The army has a hammer, called war. What better way to start a war than by throwing spitballs at aliens?
Actual posted comments to the article:
” When the Old Ones, who dwell among the stars return, they will put us in our place.”
“It would destroy religion and the oil industry.”
” The Vatican is at this very moment expecting to meet an alien to save the world. This will be the seed of Satan!”
The point I’m making is that SETI is a branch of science. The opposite of “science,” for want of a better word, might be called “belief.” (jingle, jingle…) Example: Recently at the ATA (visitor hours 9am-3pm M-F), a courageous young man told me straight to my face, “I don’t believe in aliens.” What was I to do? I said, “Well, it’s not a religion.” (jingle, jingle…) Ah! Not to disparage religion or any other system of beliefs. To avoid the imminent mobs, I’ll re-label what I called “beliefs” as, “convicted opinions that cannot be tested by observations of nature,” or opinions for short.
Whether or not aliens exist is not a matter of anyone’s opinion. It is a scientific question that can and should be answered with science.
For more see parts 2 and 3 on this blog topic.
Ya know? I’m really turned off by posts like this:
I should not give this guy any air, but he is an example of folks who make decisions about the value of the SETI research coming from a point of ignorance. A very readable book by Robert H. Gray discusses the observation of the “WoW!” signal, observed at Ohio State University in 1977. I see this work panned by “Tom:”
Tom discredits the book with the argument that signals from far away (alpha-centauri) will be weak. (Add your favorite sarcastic exclamation here.) There is plenty of solid physical evidence that an Arecibo-like transmission from Alpha Centauri can be detected with current Earth technology. While alpha centauri is not a particularly good location for life (as we know it), and the WoW! signal was probably an experimental glitch, I’m annoyed by criticisms that are not scientifically founded.
This blog is really about Kepler-186-f, a recently discovered proto-Earth planet that made the cover of Science on 18-April-2014. First author Elisa Quintana is a SETI Institute principle investigator. Thanks to this “inside track,” we at the Allen Telescope Array (ATA) had a 3-week head start doing SETI on 186-f before any other observatory, looking for signs of extraterrestrial technology. In case you haven’t heard, the ATA is a radio interferometer telescope designed especially for the search for extraterrestrial intelligence (SETI) in the terrestrial microwave window (TMW, 1-10 GHz) and running 12 hours every day, looking for signs of interstellar communications. The ATA is especially suited for SETI searches since it has an instantaneous coverage from 1-9 GHz, and we’re not afraid to use it! Most SETI searches look only in lower frequencies (1-3 GHz). The ATA leads the field in recognizing that the entire TMW is fair game for interstellar communications.
In the 3 weeks leading up to announcement of 186-f, the ATA covered 1-9 GHz looking for technological signals 2-3 times, with a sensitivity of ~100 Jy in 1 Hz (that is, a very good sensitivity). Looking back more than just once is important at frequencies >4 GHz, because SETI signals may experience fading (an AM radio term, and familiar to anyone who’s tried to pick up AM radio from Chicago) on the way to Earth. Multiple observations increase the likelihood that our telescope will detect the signal.
Simply put, if about 500 years ago, 186-f were transmitting a tuning-fork like radio beacon, then we would have seen it. Provided their transmitter were at least 8x as powerful as the most powerful transmitter on Earth, the Arecibo planetary radar. Considering that ET probably has better technology than humans do (since they are older than us), this is far from impossible.
Kepler 186-f is just the first of uncountable planets that could harbor life “as we know it.” Extrapolations of Kepler results suggest that Earth-like planets are abundant. Still, life as we know continues to be evasive. As Fermi put it, “Where are they?”