Category Archives: Our universe

The Earth and the Moon: A Match Made in the Heavens

The Moon’s a pretty darn awesome thing to have.  Look at all it gives us.  A way to track the days, the majesty of the tides, crackpot prognostication in the daily newspaper … and eclipses!  How cool are eclipses?!  Life would be a lot more boring if it weren’t for the Moon.  The thing that’s not immediately recognizable, though, is that life might not be at all if it weren’t for the Moon.

The Earth’s moon seems to have formed in a similar fashion as the satellites belonging to the other planets in our solar system, but with a key difference.  Recent studies suggest that moons form when material within ring systems, like Saturn’s, coalesce to form the rocky companions.  It’s thought that ring systems of the outer planets were comprised of leftover material from the accretion of each protoplanetary disk, but the debris that encircled the Earth and condensed to create our Moon probably had a different source.  Namely Theia, the postulated, Mars-sized planetoid that smashed into the early Earth and launched a large chunk of it into orbit.

It might sound like a crazy idea, but there’s a decent amount of evidence for it.  There are still kinks to be worked out, like why the Moon’s oxygen isotopic ratios are almost identical to those of the Earth instead of a hodgepodge of ours and the impactor’s, but other similarities in composition actually bolster the hypothesis.  Then you’ve got all the lunar evidence of its impactful origin.  The crystal structure of many of the Moon’s minerals point to a molten beginning, which is hard to come by for a small body without the injection of large amounts of energy, e.g. being blasted off of somewhere else.  Zinc isotopes in particular seem to have been fractionated and volatilized, processes that don’t occur during run-of-the-mill geologic conditions.

And thank goodness it happened.  If the Earth had cooled without disturbance, most of the useful and precious (heavy) metals should have drifted down into the core.  The fact that we have significant amounts of iron, silver and gold so close to the surface is more evidence that something annihilated itself against Earth, leaving its core materials down below, allowing us to make things like cars, computer chips and keychains that make fart noises.  All of which would be useless if life hadn’t come together in the first place, which some think, amazingly, can also be attributed to the Moon.  Shorter, stronger tidal cycles 4 billion years ago may have provided the right changing environments to teach the first “protonucleic acids” how to replicate, leading to the formation of DNA and RNA, the building blocks of us all.

“I just wanted to say … thanks for being there, man.”  Image credit to universetoday.com

But the Moon didn’t stop exerting its beneficial influence there.  Once life got chugging along, the tides may have continued to force adaptations by hurling the fledgling organisms into unfamiliar territory.  Those strong early tides also squeezed and stretched the Earth itself, causing surface displacements up to a kilometer a day, kinetic energy that would slow the planet’s cooling and keep plate tectonics — and thus the carbon cycle — moving.  The Moon’s gravity also helped stabilize our axial tilt, which may have varied wildly without it.  An irregular wobble could have prevented the normal seasons we’re used to and hence made it difficult for complex organisms, that can’t adapt rapidly, to develop.

WHAT DOES THIS MEAN?

While it may not mystically control your personality, the Moon has gone a long way into making you who you are.  With all the mentions of it here, have you figured out why the tides were more frequent and stronger in the ancient past?  The Earth was rotating faster, only to be slowed gravitationally by that big hunk of cheese.  So you can also thank the Moon for a weekend that’s twice as long.  The tides were stronger because the Moon was actually closer to us back then.  Its orbit expands as time goes on.  We live at the exact right time for eclipses to occur!  Pretty darn awesome.

Much of the information here was taken from the very informative “How Earth and the Moon interact” from Astronomy Today.

If it’s not anitmatter, what is “dark matter?” Good question.

We’re clear that dark matter is not antimatter, right?  It can’t be, or it would constantly annihilate any “regular” matter that wandered by, and we’d be able to detect the effects of those mini-catastrophes.  Instead it just sits there, unseen, not interacting with light and barely ever touching the normal kinds of stuff we know.  Hard to figure a guy out with just the impression his ass leaves on a couch cushion.  More on that later.  Antimatter we understand, partly because its existence was predicted mathematically by the legendary Paul Dirac in 1928, before it was ever observed “in the wild,” an insight for which he won the Nobel Prize in Physics.   Once the numbers came up, we actively went looking for it, and physicist Carl D. Anderson acquired the confirmation 4 years after, separately also earning his field’s top honor.

We came at dark matter differently, as instead of predicting it, the stuff took us by surprise.  Our conception of dark matter began largely as an ad hoc placeholder for a funny observation of the outermost edges of galaxies.  According to traditional orbital mechanics, stars way out there should move much slower than the ones closer in, as there isn’t as much mass acting on them.  While that’s true, those speeds didn’t trail off nearly as sharply as calculated, a puzzling discovery made by Dutch astronomer Jan Oort, the namesake of the “Oort Cloud” of comets that envelop our solar system, in 1932 (see image below).  Fritz Zwicky made a more precise observation a year later when analyzing the rotation curve for the Coma cluster of galaxies, and determined there should be more than 100 times more mass in the farthest regions than was visible.  Zwicky decided there had to be unseen (unseeable?) matter out there gravitationally pulling those stars along.  That’s a pretty big assumption.  Could something else be at play?

Rotationcurve_3from asterisk.apod.com

In 1983, Israeli physicist Mordehai Milgrom wondered if maybe the calculated mass discrepancies exist because we don’t understand how Newton’s law of universal gravitation operates at great distances, so that it’s the equation that’s wrong, and there really is no need for “invisible matter.”  It wouldn’t be the first time Newton came under fire from advancing physics.  Does relativity ring a bell?   Since Milgrom proposed his Modified Newtonian Dynamics, though, dark matter has scored a significant win with the phenomenon of gravitational lensing.  If dark matter is massive enough to change the speeds of distant stars, than it should be able to bend light, as well.  The smearing of the galaxies in the below image is due to the bending of light as it passes through the Abell 1689 galaxy cluster, as observed with the Hubble Telescope.  Thing is, without dark matter,  there just isn’t enough mass to account for all that distortion.  There must be something we don’t see.  Observations of the cosmic microwave background radiation seem to further necessitate the presence of the mysterious material.

Grav. lensfrom wikipedia

So while we can now be pretty sure that dark matter is a real thing, we’re still unable to get much of a handle on it.  Most of it seems to be where we first noticed its effects, in enormous “halos” surrounding galaxies.  Recent research suggests however that it could be strung throughout all of space, and earthbound experiments are counting on picking out a few particles to further examine its nature.  The Cryogenic Dark Matter Search (CDMS) of the University of California at Berkeley made waves last month when they announced three possible dark matter signatures detected in 2007 and 2008.  The CDMS utilizes silicon and germanium crystals cooled to near absolute zero, and operates under the idea that on the rare occasion that a bit of dark matter does interact with regular matter, the displacement it causes in the crystal can be measured.  The whole apparatus is buried deep underground to minimize false positive detections.  Similar experiments using water have been used to detect neutrinos, as does the new COUPP-60 dark matter experiment.

WHAT DOES THIS MEAN?

Figuring out what dark matter is proves to be a lot more difficult than showing that it is.  In addition to terrestrial detectors, the Alpha Magnetic Spectrometer on the International Space Station got some attention in early April when project scientists revealed they may have evidence that dark matter is mostly made of theoretical particles called neutralinos.  How did they make that determination?  With antimatter!  The new measurements show more positrons in cosmic rays than anticipated, which some speculate are produced from the collision of dark matter in deep space.  I guess the two things have hidden connections after all.

CSI Milky Way: Cosmic Ray Shooters Finally Identified

We are under constant attack and we cannot escape our assailant.  No matter where we hide, each of us is riddled with 30 hyper-speed bullets every second.  You can’t run, either.  We’d probably be dead by the time we got to the neighbor’s.  Don’t bother trying to call for help; the perpetrator also targets our communication satellites.  We’ve known of this unprovoked assault for ages, but only recently have we conclusively proved just who’s out to get us.

The electricity and ionization in the atmosphere was the first clue that something was up.  There was something very energetic disrupting our atoms.  Henri Becquerel’s 1896 discovery of radioactivity seemed to make this an open and shut case, as decay of heavy isotopes within the Earth took the blame.  International intrigue cast doubt on the culprit’s identity in 1909, when German physicist Theodor Wulf took an elctrometer to the top of the Eiffel Tower and found the levels of radiation there were actually greater than at the ground surface.  No one on the beat believed him.  The case grew cold.

Victor Hess, though, was unsatisfied.  He wanted to go higher.  in 1912 Hess used a hot air balloon to take three enhanced versions of Wulf’s electometers to a height of 17,000 feet, where they measured an ionization rate four times what you’d expect at sea level.  Wulf had been right.  The barrage was coming from beyond, not from within.  The Sun became the next suspect, but Hess was able to rule it out by performing the same experiment during a near-total solar eclipse, with the moon blocking much of the Sun’s radiation.  The tricky detective work earned him the Nobel prize in 1936, but it ultimately left us with more questions than answers.  What was causing the ionization, and who was behind it?

Robert Millikan had already worked his way up the ranks when he picked up the assignment in the 1920′s.  Coining the term “cosmic rays,” Millikan believed gamma rays were the offender’s ammunition of choice.  But the ballistics didn’t check out.  In 1927 J. Clay dared to question the respected veteran by pointing out that cosmic rays were more intense at higher latitudes, swept there by the Earth’s magnetic field.  They couldn’t be light waves like gamma radiation; they had to be charged particles.  Experiments in the ’30′s, spurred by Bruno Rossi’s insights, showed that cosmic ray intensity was also greater from the west, indicating the particles were positively charged.  The weapon had been found.  High-speed protons.  But what could accelerate the tiny projectiles to such velocities, as high as 95% the speed of light?

cosmic rayImage from (where else?) cosmicray.com

Fingering the perp continued to prove difficult.  The line-up over the decades included magnetic variable stars, nebulae, active galactic nuclei and more, but no single scofflaw could be picked out. Supernovae became the prime suspects, as the expanding envelopes from their explosions could possibly provide the power needed to boost the protons’ speed to deadly levels.  Charged particles get deflected by other matter as they rocket through space, however, making the locations of the shooters hard to pin down.  The forensics were hand-cuffed.  Technology had to advance to uncover the well-hidden tracks.

Beginning in 2008, Stanford University’s Stefan Funk and his team set up a four year stakeout with the Large Array Telescope of NASA’s Fermi Gamma-ray Space Telescope.  They focused their attention on two supernova remnants in the Milky Way.  As it turned out, gamma rays were the key after all. While the trajectories of the proton bullets themselves may be too tricky to track, their gamma ray by-products zip right through, unaltered.  In February of 2013 the group announced that the observed energies matched the predictions.  They had a positive ID.

WHAT DOES THIS MEAN?

Pop the corks and call the D.A. After a century of hard-nosed investigation, we’ve got our man.  It was a circuitous route to the truth that in a way brought us back to where we started.  It goes to show that when you start tugging on a tangled thread, you never know where it’ll lead.  Gut instincts and gumshoe hunches only get you so far if you don’t have the observations and technology to back them up, though.  Even seemingly intractable cases can be solved given enough progress of time and technique.

I do hope the judge goes easy on the sentence, though.  Despite their cosmic ray malfeasance, supernovae have a history of community service.  It’s thought that elements heavier than lead can only be produced in stellar explosions, meaning many of our most precious minerals wouldn’t be here without them.  Some even speculate that a supernova may have triggered the collapse of the dust cloud that formed the entire solar system to begin with.  What a crazy, mixed up universe we live in, where a progenitor can turn on its own creation.  I’m getting too old for this shit.

Invisible Chaos Engines: How a Black Hole Could Wreck Your Day

The legends said they loom silently in the darkest depths of outer space.  Growing.  Accreting.  Devouring.  Grandpappy Einstein would spin mathematical yarns about collapsed stars so dense not even light could break free from their inescapable grasp, but he never really believed the stories were true.  “Now don’t fret,” he’d conclude, bouncing the cosmological community on his knee.  “The material within would have to reach orbital velocities equal to the speed of light, and we all know that can’t happen.  Black holes aren’t real.”

He was wrong.  Dead wrong.  Now we estimate there must be around 100 million of the ebon annihilators in our galaxy alone.  And the biggest, baddest mofo of them all lies right in the center, snacking on asteroids while we all helplessly circle it.  But that’s 26,000 light years away.  And the closest stellar-size black hole isn’t any nearer than 1,500 light years.  They can’t possibly hurt us way out here, right?  Wrong again, chump!  Even if you don’t get close enough to be torn apart like a piece of spaghetti by the black hole’s gravity gradient, the monsters can still find ways to reach out and wreck your shit!

The very birth of a black hole could ironically kill many of us.  The little-understood phenomenon of gamma ray bursts (GRB) are thought to result from the implosion of a rapidly rotating, high mass star, which leads to the creation of neutron stars or black holes.  Gamma rays are the most energetic of all electromagnetic radiation, even more potent than X-rays, and the giant blasts emitted by black hole-birthing supernovae are the brightest events in the universe.  If a star within 10,000 light years of us went pop, a directed GRB could fry off up to a quarter of the Earth’s ozone layer, leaving us underprotected from harmful solar emissions, causing extinctions and radiation sickness.

black_hole_spin-580x326image courtesy of NASA

The supermassive black hole at the center of our galaxy formed long ago, so it’ll have to take a different tact if it wants to strike at us.  Maybe it’ll just start chucking stars our way.  As of 2012, 16 so-called “hypervelocity stars” had been identified in the Milky Way, zooming through at 2 million miles per hour, and six as big as our sun have been newly discovered.  The solar speed demons are presumed to have been slingshotted away from Sagittarius A* when the block hole greedily gobbled their companion stars.  Needless to say, if one of those nuclear-powered projectiles was flung in our direction, the immediate effects would impact more than just the atmosphere.

And if that doesn’t work, hell, maybe it’ll just come for us itself!  NASA announced last year they had identified what seemed to be a supermassive black hole being ejected at high speed from its host galaxy.  Astronomers suggest that when the galaxy collided with another, the two black holes at their respective centers also merged, creating titanic gravitational waves that kicked the new super-entity out of the neighborhood.  A body bearing down on us with a mass millions of times that of the Sun is… literally unimaginable.

WHAT DOES THIS MEAN?

Fortunately, we don’t have to spend a lot of time imagining these things.  While they could and perhaps should make for great science fiction fodder, the likelihood of any of the aforementioned disasters occurring is essentially nil.  A gamma ray burst, emanating only from two opposing ends of a supernova, would have to be pointed directly at us to have a devastating effect, and a GRB close enough to cause significant damage is only thought to happen every 5 million years or so.  Warren Brown of the Harvard-Smithsonian Center for Astrophysics thinks that there lurks only one hypervelocity star for every 100 million ordinary ones.  The Milky Way’s supermassive black hole shouldn’t be able to go mobile until we collide with the oncoming Andromeda galaxy in 4 billion years.  Black holes do have tantalizingly destructive consequences, but they’re unlikely to bother us in the near term.

That goes for the theorized “micro black holes,” too.  Some predictions expect that tiny versions of the beasts may have existed shortly after the Big Bang, and more far-out ponderings wondered if they could also be created by the Large Hadron Collider in Switzerland.  It hasn’t happened, as far as we know, and even if it did, the microscopic miscreants would evaporate before they could do any damage.  It may be fantastic to think about, but on the list of potential cosmic catastrophes, black hole destruction should fall far behind things like asteroid impact, which could be more easily avoided if predicted ahead of time.

The solar system hates Russia: Chelyabinsk, Tunguska and UFOs

Remember the “other factors” pointed to by Rare Earth hypothesis proponents I mentioned in the previous post?  Things that may be necessary for the evolution of complex life that aren’t intrinsically accounted for in the Drake Equation?  One of those is the presence of a significantly large, so-called “gas giant,” like Jupiter, in the same system as a habitable planet.  The idea is that such a sturdy stalwart acts to gravitationally Hoover up enough of the biggest asteroids loitering around the neighborhood so as to allow the critters on an inner planet enough time to figure out things like civilization, technology and e-mail before they shoot cosmic craps and some big space rock slips in and ruins it for everyone.

Fat fucking lot of good it did for the residents of Chelyabinsk, Russia on Friday, February 15th.

But hey, we’ve seen our burly protector in action, through the 1994 impacts of Shoemaker-Levy 9 cometary fragments.  So we know it does its job, as least sometimes, as the largest piece of Shoemaker shrapnel was on the order of 100 times the size of the little guy that injured over 1,000 and did more than $33 million in damage last week.  Imagine a fleet of those jerks showing up on our doorstep.  Thanks for having our back, Jupes.

Our watchful big brother can’t catch ‘em all, however, and some of the smaller stuff sneaks on through.  On average we can expect an interloper the size of the Chelyabinsk object every 30-60 years.  This most recent assaulter was the largest since the then mysterious 1908 blast at Tunguska, in the Siberian region of (would you believe it?) Russia.  The solar system is obviously trying to strike at our population’s strategic vodka reserves.

WHAT DOES THIS MEAN?

Asteroid early detection is no joke.  Fortunately, NASA estimates that they’ve locked down the orbits of more than 90% of the near Earth objects large enough to wipe us out (those at least a kilometer in diameter), and none of them should come calling anytime soon.  The outlook is less rosy when considering debris with diameters in the 100 meter range, as we’ve only got a handle on about 30% of those.  To compare, Friday’s visitor was probably less than 20 meters in size.  There are hopes that new projects like ATLAS will aid in increasing our detection limits, but even that won’t spot rocks as small as the Chelyabinsk body.  Maybe it’s time to spend more than $3 million a year on such things?

Additionally, perhaps this will finally shut up the Tunguska conspiracy nuts.  Some people will try to find a mystery anywhere, and plenty claim something stranger must have happened then because no large meteorite fragments were found.  Forgetting the fact that no one bothered to look for 13 years.  And ignoring the discovery of the predicted silicate and magnetite spheres in the surrounding soil and tree resin.  Or the anomalously high amounts of iridium, an element that’s rare on Earth but more abundant in asteroids.  The first fragments of the Chelyabinsk object have been identified, but it’s probably easier to know where to look when you can see the damn hole in the ice.

The ubiquitous video footage of the meteor’s approach, thanks in part to Russia’s obsession with dash cams, has nothing but bad implications for the “UFO phenomenon,” to boot.  If interstellar snoops are constantly dropping by, why aren’t they repeatedly filmed from a myriad of different angles, as in the montage above?  And don’t tell me they know enough to avoid the former Soviet republic; I’ve seen sighting reports from less than 2 months ago.  Hell, the meteorite that struck a parked car in Peekskill, New York in 1992 was filmed by *16 different people,* in a time prior to our now inescapable cell phone preoccupation.  If aliens were around as much as the proponents claim, they’d have a weekly dedicated segment on TMZ.

Kepler informs Drake: Plugging Real Numbers into the Equation

The question, “Are we alone in the universe?” penetrates to our very cores. When we look up at the night sky, is there anyone gazing back? Or are we set adrift in the cosmic ocean all by our lonesomes? If there are others beyond our sight, wondering the same thing, how many are there? Are they close enough to hold a conversation, or would the interstellar service provider drop the call? Can we ever know the answers to these humbling and vexing questions?

In 1961, astronomer Frank Drake aimed to reduce the uncertainty by putting numbers on the important planetary parameters. In preparation for a meeting commissioned by the National Academy of Sciences, a gathering that would set the stage for the now-famous radio wave investigation, the Search for Extraterrestrial Intelligence (SETI), Drake jotted down a list of things you’d need to know in order to determine how many potential pen pals we could expect in our galactic neighborhood. The eponymous Drake Equation was defined thusly:

Drake equation ,

where “N” is the number of alien civilizations within communication range (AKA “the thing we wanna know”) and the other factors are as follows:

R* = the average rate of star formation per year in our galaxy
fp= the fraction of those stars that have planets
ne = the average number of planets that can potentially support life per star that has planets
fl = the fraction of the above that actually go on to develop life at some point
fi = the fraction of the above that actually go on to develop intelligent life
fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
L = the length of time for which such civilizations release detectable signals into space

Again… this was in 1961. Four years before the best evidence of the Big Bang was stumbled upon, eight years prior to men walking on the moon, and more than a decade preceding the first conclusive identification of a black hole. Where was Frank Drake getting estimates for these values? Why did he assume that technologically advanced civilizations eventually die out? What if they colonized other planets; how would that affect the numbers? The lack of precision and utter guesswork inherent in this formulation did not go unmentioned, leading some, such as “xkcd” cartoonist Randall Monroe to proffer cheekier versions.

Drakexkcd

Drake’s equation may have taken form solely as a way to kick off discussion, but ya just can’t help but try to fill it out, can ya? With their limited knowledge, Drake and his colleagues plugged in numbers and chugged out a range of values between 1,000 and 100,000,000 communicating civilizations in our galaxy. So yeah, lots of uncertainty still, especially when the numbers you’re picking are plucked out of pure speculation to begin with. But what happens when you apply 50 additional years of astronomical knowledge? Can modern discoveries help refine Drake’s bullshit equation?

The original (conservative, they thought) estimate for R*, the average rate of star formation in the Milky Way, was put at about 1 per year. Using some tricky techniques of the INTEGRAL gamma-ray observation satellite in 2006, NASA and the European Space Agency were able to jack that number up to 7. Later studies with the Spitzer Space Telescope further pare that down to a single star like our sun annually. Hey, not a bad guess on that one. When you consider that the rate of stellar formation was higher in the past (back when a civilization would have to start out to get to a communication stage by now), things might look even better than initially expected!

The next term, fn, the fraction of stars that have planets, is something that couldn’t be honestly addressed until very recently. The original shot-in-the-dark supposals were between one fifth (0.2) and one half (0.5). The first “exoplanet” was confirmed in 1995, but it was only with the launching of the Kepler Space Telescope in 2009, however, that we gained the ability to identify smaller, rocky planets (like our own) by observing the dip in starlight from their parent stars as they cross in front. Kepler has provided a flood of planetary candidates, almost 3,000 of ‘em, leading to some bold predictions, such as that of Harvard-Smithsonian Center for Astrophysics researcher Francois Fressin, that nearly every sun-like star should have at least one planet. Uh, wow. Drake’ll take that, for sure.

Moving further down the chain… is still the realm of speculation. We await the confirmation of Kepler’s current 461 “maybes” that seem to exist within their host star’s so-called “habitable zone,” which would assist in constraining ne, the possible “life-supporting” planets each particular star boasts. A true Earth twin hasn’t been discovered yet, but as Kepler casts its net wider in 2013, many believe that moment is mere months away.

WHAT DOES THIS MEAN?
 

Frank Drake should be a happy man! And the rest of us, too, as we slowly trudge through the components of the equation with continuing data, bringing us closer to answering our fundamental questions. The value of fp, the fraction of habitable planets that do develop life, will be harder to put a figure on. Spectroscopic techniques can determine the components of far-off atmospheres, but none with the telltale markers of respiration have yet been identified. And once you get observational data for fi, the fraction of those planets that develop intelligent civilizations, it’s pretty much game over, right? One would be enough to make us greatly rethink our place in the universe.

But how likely is it? Proponents of the Rare Earth Hypothesis, such as Peter Ward and Donald E. Brownlee, suggest there are other factors affecting the possibility of intelligent life that aren’t accounted for in the Drake Equation and other estimates. Still, the numbers we’ve compiled over the last half-century have to be encouraging to those who dream of the ultimate foreign correspondence.