The average sci-fi fan likely takes for granted the speed of light and no doubt breaking the speed limit so callously is an expected aspect of story telling, but there are some really interesting implications to traveling at relativistic speed that I don’t think a whole lot of people are aware of. A fairly simple implication is, from our point of view, that an object approaching us at or near the speed of light (ie relativistic speed) appears as tinted blue. A more complicated implication is that time is running slower for the relativistic passenger. Let me explain…

Let’s say there’s a guy riding a motorcycle near the speed of light.  Because light acts like a wave, the motion of the object is going to compress and stretch the light waves radiating from it.  This is known as the Doppler Effect and is evident every time you pass a blaring siren – you hear the pitch rise as you approach it and then drop off as you move away from it – “yyyyyeeeeaaaarrrrooooowww!”  This is simply because the sound waves are being compressed as you approach it; this shortens the wavelength and creates a higher frequency sound.  Naturally, as it recedes, the sound drops in pitch because the waves are stretched to lower frequencies.

This is really a property of all waves, including light.  In fact, it’s happening all around us but the amount of shift in the light spectrum is so tiny that we just can’t detect it.  However taking our scenario above, the speed of the motorcycle rider would significantly amplify the shift and he would appear to turn blue as he approached you and red as he passed you.  Incidentally, this Doppler Shift is used by astronomers to detect planets orbiting other stars (among other things).

Another interesting implication of traveling at relativistic speed is that time slows down for the traveler in relation to the observer.  This is known as Time Dilation and is a result of time being relative from observer to observer as described by Einstein’s Theory of Relativity.  In the case of our motorcycle rider, because of his speed his watch appears to run slower to the people observing him.  This is a strange property of the Universe but we observe it in many places.  One of the best examples is muon decay from cosmic rays colliding with our upper atmosphere.

Cosmic Rays are high energy particles formed in powerful celestial events such as the cores of stars, supernovae, neutron stars and black holes.  They blast out in every direction in the cosmos and daily they smack into our atmosphere.*  When these protons collide with air molecules they break apart into sub-atomic particles that decay very quickly.  One of these types of sub-atomic particles is the Muon, something very similar to the Electron yet significantly more massive and highly unstable.  Muons created in these collisions live for one to two microseconds or 1.0 × 10^-6 seconds.  That’s a ridiculously short time so it would be expected that we can only detect these muons in the upper atmosphere because there aren’t around long enough to make it to the surface – even traveling at the speed of light.  Yet they reach muon detectors on the surface daily!  What gives?

The reason is because of Time Dilation, pure and simple.  The one to two microseconds the muon experience appear to be longer to us, the observer.  In other words, time for the muon runs slower from our point of view.  To explain why is a bit involved, but the video below does a good job.  In a nutshell, relativity is allows for time to be flexible to keep the speed of light a constant for everyone.

* it should be noted that these collisions are at MUCH higher energies than that produced by the LHC, and because the Earth is still here it’s safe to assume that the LHC can’t produce an Earth devouring black hole – otherwise it would have already happened.

Often called “The Man Who Fought for Three Flags,” Larry was born in Finland in 1919 as Lauri Allan Törni.  As a young man he fought the Soviets in the early part of the Second World War and was later sent to Germany to train with the Waffen SS where he became an infantry officer.  He spent the rest of the war continuing to fight the Soviets in Finland and his exploits as the leader of a detachment of guerrilla fighters behind enemy lines made him famous on both sides of the conflict.

As the war came to an end, Thorne escaped a British POW camp and returned to Finland where he ended up in jail for a few years before being pardoned.   This is where his life took a dramatic turn.  After escaping to Sweden a year later, Thorne came to America and joined the Army under the the Lodge Act; switching his name to Larry Thorne in the process.

It wasn’t long before he was selected for Special Forces and became “an ideal Green Beret.”  As a member of 10th SFG(A), Thorne was well positioned to serve in Europe – teaching mountaineering, survival and guerrilla techniques to fellow SF soldiers.  By 1960 he was commissioned an officer again, his third time and third nation of allegiance.

One of the missions Thorne was famous for while serving in 1oth Group was a recovery mission high in the mountains of northern Iran.   He succeeded where two other missions had failed, recovering classified material and the bodies of a C-130 crew.  Not long afterward he deployed to Vietnam as part of 7th Group and returned for another deployment with the elite MACV SOG.  Running reconnaissance missions into Laos and Cambodia, Thorne was back to doing the type of work he did in WW2.

Thorne’s chopper crashed on one of those missions in October of 1965 and he was presumed  dead until his remains were located in 1999.  He was buried with full military honors at Arlington Cemetery – a man who fought for Finland, Germany and died an American soldier.

His legacy however lives on.  The headquarters building for the entire 10th SF Group bears his name, but more importantly the Group has an award in his name – The Larry Thorne Award – for the best detachment in the Group.  One of the things I loved about SF over other SOF units such as the Ranger Regiment is the type of people it attracts.  In the ’90s I served with an NCO who’d escaped from East Germany as a teenager and went on to become an American SF soldier – again, perfectly positioned in 10th Group to be on a team working in Europe.

Thorne’s exploits in Vietnam are covered in Major John Plaster’s excellent book SOG: A Photo History of the Secret Wars.

One of the most effective ways to do this is to look at the apparent brightness of lights of a known magnitude.  Because light energy fades in a very predictable way (inverse square falloff), you can determine the distance accurately as long as you know the absolute brightness.  So try this thought experiment: if you went out on a deserted road at night and placed 100 watt light bulbs along the road every hundred meters, the closest lights would be the brightest and the farthest would be the dimmest - yet in reality they are all of the same absolute brightness.  If you stand next to each of them, they put out 100 watts of energy, but the light traveling from the farther ones loses energy, so it appears dimmer.  So by measuring the brightness of each light you could determine the distance because you know how bright it actually is and how bright it appears; essentially just by measuring the loss of energy over distance.

So how do we do this to measure the distance to stars?  As you can see in the image to the right, stars come in a wide variety of sizes and brightness (click to enlarge).  From the relatively cool, tiny Red Dwarf to the hottest, most massive blue Hypergiants, the brightness of stars varies considerably even amongst the same type.  With so much variation, it would be impossible to accurately use brightness to measure distance.  If only there was a class of bright object scattered throughout the Universe that always had the same brightness?  It turns out there is!

When a star with a mass similar to our Sun runs out of its hydrogen fuel, it can’t generate heat pressure to fight against gravity and the core starts to compress.  This compression generates heat again and causes the core to start fusing heavier and heavier elements – hydrogen into helium, helium into lithium, lithium into berylium, etc.  Heavier elements require increasing amounts of heat and continue to release energy with each pair of atoms fusing.  For a more detailed explanation of this process, check this link out.  For stars like our Sun, the process causes the star to shrink then swell up, shedding material into space until only the ultra-dense core remains.  This is when a star becomes a White Dwarf.

White Dwaves, like the stars they formed from, come in different sizes and brightness, so this isn’t our standard candle.  But something interesting can happen when a White Dwarf orbits another star.  Our star sits in space alone, except for the planets orbiting it, but out there in the cosmos binary star systems where two stars orbit each other are quite common too.  Now if one of those stars becomes a White Dwarf, a situation can occur where the smaller but often equally massive object gravitationally pulls material off it’s neighboring star.  This leaching effect causes matter to collect on the small ultra-dense (and therefore gravitationally powerful) White Dwarf.

How dense is a White Dwarf?  Dense. So dense that one the physical size of the Earth would have a density of 1 x 10⁹ kg/m³.  In case you forgot Scientific Notation, that’s 1 billion kilograms per square meter.  The Earth, on the other hand, has an average density of only 5.4 x 10³ kg/m³ or 5400 kilograms per square meter.

As this material collects onto the surface of the White Dwarf, its mass increases.  But there’s a problem that makes it a ticking time bomb.  As the mass increases, gravity crushes the object down even further, forcing all of the atoms closer and closer.  Eventually there is no room left because the electron density is too great and the object stops shrinking (via the Pauli exclusion principle).  Eventually the mass of the White Dwarf builds until it exceeds the Chandrasekhar limit, triggering carbon fusion which in a sense jump starts the once dead star.  However as soon as this happens, a portion of the matter ignites a runaway reaction which tears the star apart, unleashing a supernova.

And what’s so special about that?  What does this have to do with those 100 watt light bulbs I was talking?  Well, because of the Chandrasekhar Limit, which is roughly 1.38 times the mass of our Sun,  we have an explosion that’s always the same brightness wherever it happens.  In other words, light bulbs with a with a wattage 1.38 times the mass of our Sun blink on across the cosmos.  So astronomer look for these Type 1a Supernova and knowing how bright they really are, determine their distance by measuring the loss of light energy.

UPDATE! So it turns out I missed a paper that throws into question the matter accretion scenario for Type 1a Supernovae.  Rob Knop goes into detail on his blog.

Here’s a clip from a recent shoot out in the desert.  The targets are 10×17″ AR500 steel targets – about the size of a laptop screen.

Update:  I just came back from another trip out to the same area and this time made a few hits on the steel targets at a whopping 1750 yards.  Time of flight to the target was almost 2 seconds and it was another 3 seconds before we heard the report.

What the hell is that?  It looks like a comet, doesn’t it?  But it’s not.  Spectral analysis of the tail shows that it’s not gas and orbital analysis says it’s connected to the Flora family of near Earth asteroids.  What you’re looking at here is most likely a very recent asteroid impact with the debris trailing off, driven by the solar wind.  Initially the Lincoln Near-Earth Asteroid Research (LINEAR) sky survey discovered the unusual site and then Hubble was pointed at it to reveal the detail you see above.

This is pretty amazing and the very first time we have witnessed an asteroid collision!

Read more at the Hubble website…

]]> http://illuminatingreality.com/?feed=rss2&p=481 0 http://illuminatingreality.com/?p=473 http://illuminatingreality.com/?p=473#comments Tue, 02 Feb 2010 01:06:22 +0000 Brandon http://illuminatingreality.com/?p=473 When I was in 1/10th SFG(A) back in the 90s, we had a month dedicated every year to teaching, developing and practicing winter warfare skills and techniques.  This was important because all three battalions of our Special Forces Group was regionally aligned to operate in all of Europe and that meant we had to be prepared to operate in mountainous regions such as the Alps or the Fjords of Scandinavia.   For that reason we had to learn not only how to survive in snowy conditions but also how to fight and win.  Much of this training was just down right fun, be it learning how to cross country ski or travel via snow mobiles, but there was also a very important tactical component to it that required training and practice to develop.

Since the GWOT began, all of the SF Groups have been very busy operating in Afghanistan and Iraq – a region that only 5th Group is regionally aligned and trained for.  This has required every team that rotates through the region to learn new skills, culture and languages that they normally aren’t trained for, and this has been going on for over eight years now.  Unfortunately, many of those regional specialty skills are quite perishable, especially language skills.  So it made me happy to see members of my old SF Group out in the snowy Rocky Mountains training hard in winter warfare between rotations.  Even though these winter skills apply to certain parts of Afghanistan and northern Iraq, it’s very easy to see how over the years they could be ignored in favor of focusing Central Asia-oriented skills.

Read more at the USASOC PA blog…

There is however one key plot point that I’d like to talk about and a related evolutionary story, so if you haven’t seen the movie yet, you may want to wait to read this.

Potential spoilers below…

In the film, the protagonist Jake Sully decides that he has to capture and tame a massive flying predator.  To do so he plans to attack from above and behind his prey, where it’s traditionally not used to having to look for threats.  This has an interesting historical analog.  The famous demise of the Channel Islands fox (see below) was once described by a park scientist as a creature which had evolved over the millennia as “a species that never had to look up to spot potential threats”, so was suddenly decimated by newly-arrived aggressive golden eagles.

“Invited by The Nature Conservancy to help build pens there for the expansion of its captive breeding program, we spent the better part of four days in the island’s interior (normally off-limits to outsiders) working on the slopes of a small valley near the historic and ridiculously picturesque Stanton Ranch erecting four 600-square-foot pens where the remaining housecat-sized wild foxes would be caught up and installed to better ensure their safety, increase their drastically low numbers, and ultimately enable their survival.

Historical nutshell time! The foxes lived perfectly on the Channel Islands with bald eagles and mice and blue jays and bugs and native human inhabitants for as much as 16,000 years, but that all began to change when between 1947 and 1971 some 1,800 tons of DDT and an unknown amount of PCBs were dumped in Torrance, making its way through sewer lines into the bay near Palos Verdes where it spread. Bald eagles on the islands eventually ate fish tainted with the pesticide and died off, and in their place came opportunistic golden eagles from the mainland, with a far greater taste for flesh than fish.

With no baldies to harrass them, the golden eagle couldn’t help but thrive by exploiting unchecked a virtually endless food supply in the expanding populations of feral pigs–  an ecologically disastrous byproduct of the farming and ranching that took place on Santa Cruz for more than 150 years. The golden eagle wasn’t picky and would gladly eat island foxes, too. And as if the eagles weren’t enough of a threat, the pigs contributed by basically rooting up much of the native vegetation, thereby both reducing the food available to the fox and also leaving them few places to hide and escape the eagles. Seriously, by 1994 when the animal was listed as an endangered spicies there were populations of foxes on some islands that barely numbered in the double digits. In the course of the recovery effort that began in the late 1990s, the golden eagles have been trapped and relocated, bald eagles have been successfully reintroduced, and the pigs — some 5,000 of them — have been killed off.

With my departure from the zoo a year after my visit to Santa Cruz Island, I confess I haven’t been keeping as abreast of the island fox recovery efforts these past few years. So it came as a surprise to learn that the captive breeding program has been so successful that the pens we built have actually been closed since last year – and for good reason: they’re just no longer needed.”

Yemen in many ways is like Afghanistan or nearby Somalia, with a very weak central government and a handful of powerful insurgent groups to challenge it.  Not all of these groups are religious extremists- many are just tribal groups vying for power in a fractured country.  Regardless, they all threaten a monetarily poor and politically weak government that doesn’t have a whole lot of friends around the world.  The government’s inability to control the outlying countryside has even led to Saudi forces launching air strikes inside of Yemen against cross border insurgent groups.

So I suspect the Yemeni government is seeing the latest attention pointed their way as a chance to bring in some much needed funding as well as allies.  All they really have to do is convince Western powers that these groups that threaten them are all linked to al-Qaeda, are a threat to the West and can be neutralized with large sums of money, equipment and training.  So if you can’t see where I’m going with this, the danger is that we end up getting suckered into a situation where someone is playing “the enemy of my enemy is my friend.”  Granted, I don’t think we have much of a choice seeing how threats like al-Qaeda will always seek safe haven in lawless areas, but we would be wise not to get sucked into a situation that could backfire on us.

The author of a previous video on Open Mindedness has posted a new video about Critical Thinking that’s an excellent primer on the concept and shows why it’s not only effective but something we should all strive to do.