Two interesting but possibly silly factoids about Star Wars

A while back Peter Mayhew – the 7’6” guy inside Chewbacca’s costume in the original Star Wars – released a lot of ‘behind the scenes’ stills from the production.

They’ve got a period look – the movie was shot in the age of disco, flares and vinyl-topped cars. But it’s kind of cool to think Star Wars still has the power to capture our imaginations despite its stylistic origins in the decade taste forgot. Which leads me to a couple of factoids:

'That's no moon'. Wait - yes it is. It's Mimas, orbiting Saturn.

‘That’s no moon’. Wait – yes it is. It’s Mimas, orbiting Saturn.

1. Tattooine is a real place. Most of the movie was filmed at Pinewood (hence the surfeit of British seventies brat-packers in bit-parts) but Lucas filmed the desert sequences in Tunisia near a town that looks like the Star Wars version. The name of that town? Foum Tataouine. Though before you all go ‘squee, how cool is it that they found a town of the same name’, think about how movies are actually made.

Not only is Tataouine a real place – it was liberated from the Nazis in 1943 by New Zealanders. I’ve met some of the guys who were in on the drive. (Just to compound the trivia, Luigi Cozzi’s Italian spaghetti version of the Lucas epic, Star Crash (1978) was filmed in part at Bari, where the Kiwis landed later the same year).

 2. Darth Vader’s real accent. Darth Vader was played by British actor and weight-lifter Dave Prowse, but he lost his voice to James Earl Jones. Prowse is from the West Country – Sir Arthur C. Clarke, who was also West Country, spoke the same way. A soft, lilting accent that is one of England’s quintessential classics. But not, it seems, suitable for the movie’s chief villain.

Call it meta-entertainment. The story behind the adventure. Or something.

I can’t help thinking that the story behind the forthcoming Disney knock-offs won’t be anywhere near as interesting.

 Copyright © Matthew Wright 2014

 

And now, some shameless self promotion:

It’s also available on iTunes: https://itunes.apple.com/nz/book/bateman-illustrated-history/id835233637?mt=11

Nook coming soon.

You can still buy the print edition here: http://www.batemanpublishing.co.nz/ProductDetail?CategoryId=96&ProductId=1410

Welcome to the weird, weird world of hyper-extreme Sheldon physics

It’s coming up for a century since Albert Einstein explained the entire ‘classical’ universe. Neatly, and in ways that have been tested every which way, without being disproven.

Albert Einstein lecturing in 1921 - after he'd published both the Special and General Theories of Relativity. Public domain, via Wikimedia Commons.

Albert Einstein lecturing in 1921 – after he’d published both the Special and General Theories of Relativity. Public domain, via Wikimedia Commons.

He never did manage to reconcile quantum physics with his macro-level rules, but there’s no question that Einstein got it right about the big stuff. General Relativity, remember, is actually a theory of gravity. And everything about it has been checked out. Repeatedly.

Still, there are points where his rules break down. I mean, literally. Points. As in mathematical points. Places that have no diameter.

They’re called ‘singularities’, and they’re inside every black hole. We can’t see them, because the singularity is masked by the event horizon. This is the point where the escape velocity of the object exceeds lightspeed – meaning light doesn’t escape, hence the term ‘black hole’.

Einstein predicted that too. And the fact that the singularity was inside an event horizon was the proverbial Good Thing because, according to theory, all the physics we know and love break down at the singularity. There has been speculation they might act as a gate (‘Einstein-Rosen Bridges’). But to Einstein and most of those who came after, it was academic, because nothing could escape the event horizon.

Enter Stephen Hawking. In 1974 he argued that black holes MUST emit particles under quantum rules. Imagine a particle just inside the event horizon. Thanks to quantum uncertainty, it is both on one side and the other. When the wave function collapses, there is a chance that the black hole has radiated a particle.

Black holes, in short, evaporate thanks to quantum effects. It takes a while for stellar-mass holes (and they’d gain more mass than they lost, via matter spiralling into them). But the particle-size black holes possible in the CERN supercollider have a lifespan of a millionth of a second. Or less.

Hawking radiation, however, doesn’t resolve the other paradox of black holes – which is that they cause loss of ‘information’. It vanishes into an event horizon and is gone, violating energy conservation rules and the conservation of information in the physics sense – unitarianism. Various explanations have been offered, none of them entirely satisfactory because the black hole exists at the intersection between the two incompatible theories – General Relativity and quantum mechanics.

This week, Hawking suggested that the best answer to the paradox is to assume that an event horizon doesn’t exist. It merely appears to; in fact the information is re-radiated, chaotically.

Artists impression of a GRB. Zhang Whoosley, NASA, public domain, via Wikipedia.

Artists impression of a GRB (which is extreme, but not weird extreme). Zhang Whoosley, NASA, public domain, via Wikipedia.

All this is weird. But wait, if you extend the theoretical thinking it can get way weirder.

According to Hawking’s early work, the universe – during the early milliseconds of the Big Bang – might have created a ‘naked’ singularity. Later he revised that idea and said it hadn’t.

But imagine if it had. Naked. A singularity unprotected by an event horizon. Anything could happen. In all probability it would emit particles. But it might emit a monkey with a typewriter, tapping out King Lear. Or Sauron. Or The Heart of Gold. Or something so wild and crazy we can’t comprehend it. The laws of physics – which include probability and the order of events – don’t exist in a singularity.

Feel like you’re trapped inside Dr Who?

Could it happen? In theory, the singularity would become a torus outside the event horizon on a black hole that spun fast enough. And there is a theory – ‘loop quantum gravity’ – which postulates that naked singularities could exist anyway. The theory’s unproven.

And as of this week there’s Hawking’s notion of no event horizon anyhow – turning ‘black holes’ into…well, probably rather more than fifty shades of grey.

Wild? Sure. Weird? Absolutely. But that’s extreme physics for you.

Pass me a bunch of fermions. I’m famished.

Copyright © Matthew Wright 2014

Coming up: More writing tips, science geekery, humour and more. Including the awaited lightspeed-with-custard experiment. Watch this space.

Bring me my interositer, pathetic Earthlings!

Anybody remember those cheesy alien movies from the fifties? Aliens with googly eyes and big heads arrive to steal women, steal Earth’s water, or both.

Needless to say, movies such as This Island Earth, I Married a Monster from Outer SpaceIt Came From Outer Space and Brain from Planet Aurus (which was about a brain from planet Aurus) had a good deal of fiction about them. Science? Uh…no…

Yes, I know science isn’t what they were about –  they played on our social fears as a device for lifting money at the box office, and as such were bedded in the human psycho-social framework

I thought I might be fun to run through the science in them anyway. Just for fun.

Anybody see a monolith go by? A picture I made with my trusty Celestia installation - cool, free science software.

Anybody see a monolith go by? A picture I made with my trusty Celestia installation – cool, free science software.

1. Aliens that look like humans
The thing about aliens is they’re alien. All Earth animals are built around the same basic plan, the tetrapod that flourished in the Devonian period – head, body, four limbs and (usually) a tail. But go back to the pre-Cambrian era and you find total weirdos, such as Edicarians. Some were so odd that paleontologists couldn’t even work out which way up they were meant to walk. And that’s just life on this planet. Now imagine life on another. I bet it won’t look like a human with a crustacean glued to its forehead (“yIqIm dude QIp tlhIngan. DaSovrup QuchDu’ lobster?”)

2. Aliens want human women
This trope was mostly about 1950s social fears. But as for the science of it – well, see (1). The chance of an alien being attracted to a human woman is about the same as an alien being attracted to oxalis. Or anything else from Earth. They’re alien. Harry Harrison riffed on it in one of his Stainless Steel Rat novels when his hero dressed up in a suit designed to look like one of the repellently squishy invaders – discovering, the hard way, that this was the height of alien pulchritude.

3. Aliens want Earth’s water
Why? We’re at the bottom of a gravity well. Also, we bite. There’s plenty of water for the taking in the Oort cloud, Kuiper belt and elsewhere. Hey – aliens might have been siphoning it for millions of years. We wouldn’t know. Or care.

4. Aliens are here to show us a better moral path
Laudable but silly. Even animals on Earth have a different moral path than humans – few, for instance, are motivated by conscious malice the way some humans are. Extrapolate that to aliens. The chance of them having world views that correct particular human failings, especially failings culture-specific to the West, is about the same as them wanting Earth’s women. See (2).

Ultimately the key word is alien. Would life on an alien world share our animal-plant split? Would alien evolution lead to a single species becoming intelligent? Would aliens become intelligent at all? Maybe they have many intelligent species. Would we even recognise their intelligence? The answer is ‘we don’t know’. Yet.

Of course that doesn’t stop us enjoying old movies. Or wondering about answers to these questions – which I hope you will. Thoughts?

Copyright © Matthew Wright 2014

Coming up: Measuring lightspeed with custard, as soon as I get some photos. More writing tips. Watch this space. 

Totally mind-blown by ‘Gravity’ and its real physics

The other weekend I went to see Gravity, in 3D. As we left the cinema there was only one thing I could say to my wife. ‘That was f—-ing AMAZING.’

Gemini 7 from Gemini 7, 15 December 1965. NASA, public domain, via Wikipedia.

Gemini 7 from Gemini 6, 15 December 1965. NASA, public domain, via Wikipedia.

I use that word a lot, just not usually on this blog. But the intensifier’s apt. After weeks slating dumb movie physics (and more to come) I was gob-smacked. Alfonso Cuaron, Kevin Grazier and the team made a massive effort to reproduce free fall. Free fall? Absolutely. It’s not ‘weightlessness’, and the astronauts are not ‘beyond the pull of Earth’s gravity’. Not in low orbit. It’s ‘free fall’ – as in falling and missing the ground. That’s what orbiting is. Seriously. Wanna see the math?

They should also have called the movie ‘Conservation of Angular Momentum’, because that’s what the physics were – everything spun…and kept spinning, because there was no force to stop the spin… Coool.

Agena target vehicle photographed from Gemini 11. Public domain, NASA, via Wikipedia.

Agena target vehicle from Gemini 11. Public domain, NASA, via Wikipedia.

Then there was the gorgeous imagery. I felt like I’d been transported back to the National Geographics I read as a kid – wonderful glossy Kodachromes of Gemini missions with Earth floating blue and magical behind them.

All that’s overlaid by the story –  an edge-of-the-seat tension drama.  Sandra Bullock’s character was tremendous. Ever wondered what you might do in a life-or-death situation? Go to pieces? Or decide to do whatever has to be done to stay alive – even if it means dying in the attempt? She took us on that decision and journey. Damn it was good!

I think the minor reality compromises the makers made to tell the story didn’t compromise suspension of disbelief. This was an awesome movie.

Of course, I’m going to list a few of those compromises – along with ways the movie also showed up the reality. But that includes spoilers – so if you haven’t seen the movie, go see it – trust me, you WANT to see this one! Then read the rest of this post.

I’ll separate the spoilers with this photo of the real thing – which is what the movie looked like. You can see my house, adjacent to the lower box on the aerial.

Spacewalk to assemble the ISS, 12 December 2006. New Zealand is below - North Island to the right, South to the left. My house is directly under the aerial centre-frame. Photo: NASA, public domain, via Wikipedia.

Spacewalk to assemble the ISS, 12 December 2006. New Zealand is below – North Island to the right, South to the left. Photo: NASA, public domain, via Wikipedia.

So – the compromises. [Spoiler Alert!] There was the scene where Bullock had to let Clooney drift. In fact they were already stopped; she had merely to tug on the cable with her pinkie finger, and he’d have drifted slowly towards her. Then there’s flying from one satellite to another using only an MMU (Manned Manoeuvering Unit) back-pack, which was flown for real in 1984 and then retired.  Hubble and the International Space Station (ISS) orbit in different planes - different angles relative to the equator – which takes a lot of energy to alter. Not possible even with a fully fuelled MMU, which has velocity-change capability (‘delta-V’) of 24.4 metres per second. There are also the physics of rendezvous in space, which are counter-intuitive – you don’t fly from place to place like the movie. I believe the original expert on how it’s done for real is Buzz Aldrin.

[Spoiler alert!] Spacesuits are harder to take on and off than portrayed, and the underwear isn’t lycra – it’s nappies (diapers), cotton long johns, and a liquid-cooling garment. Here’s a video. Actual donning time is about 20 minutes. There’s a pressure differential; the Extra Vehicular Mobility Unit (EMU) – NASA’s term for the spacesuit, which lacks any propulsion system – is pressurised to 4.3 PSI (222.37 torr), whereas the ISS operates at 14.7 PSI (760.2 torr). This means the astronauts have to spend four hours pre-breathing oxygen to avoid dysbarism – ‘the bends’, before a space-walk. Total time in the suit might be ten hours or more. That’s why the engineers insist on the nappy.

Gemini astronaut space-walking. Public domain, NASA, via Wikipedia.

Gemini astronaut space-walking. Public domain, NASA, via Wikipedia.

[Spoiler alert!] People don’t snap-freeze in vacuum. It is a brilliant insulator and heat is lost through radiation, not conduction. That’s why thermos flasks work. In shadow at Earth’s orbital distance it’s over 160 degrees C below, but that doesn’t alter the physics. The human body is more than half water, which has high thermal energy storage capacity (334 million joules per cubic metre). You’d freeze solid providing you stayed in that shadow, but not in minutes. Or hours…

And now the realities. Get this – a lot of the mayhem they showed has actually happened before, mostly to Soviet spacecraft. [Spoiler alerts!]

* Re-entry while tumbling. The Soyuz 1 mission tumbled into the atmosphere after failure of the control systems on the maiden flight of the Soyuz 7K-OK spacecraft, 24 April 1967. The sole cosmonaut, Vladimir Komarov, never gave up – he was a fantastic pilot, and managed to control the entry in the end. But the parachute release door was damaged. Komarov released the reserve chute, but it tangled with the drag chute and he was killed when Soyuz 1 slammed into the ground near Orenburg.

Soyuz TMA. Public domain, via Wikipedia.

Soyuz TMA. Public domain, via Wikipedia.

* Re-entry without PAO separation (Priborno-agregatniy otsek = service module). Only the SA re-entry module (‘B’ in the diagram) returns to Earth, base-end first; the other modules are jettisoned before re-entry. During the mission of Soyuz 5, 18 January 1969 – the orbital module (‘A’) jettisoned normally, but the PAO (‘C’) did not separate, causing the re-entry module to hit the atmosphere nose first with the PAO behind it. Oops. Luckily the bolts burned through and the PAO broke away, allowing the re-entry module to spin and present the heat shield to the atmosphere. It happened again with Soyuz TMA-10 on 21 October 2007, and AGAIN with Soyuz TMA-11 on 19 April 2008.

* Fire in orbit. On board Mir space station, 23 February 1997. It took 14 minutes to extinguish.

* Collision between spaceship and space station solar panel. Mir again, 25 June 1997 – the Progress M-30 freighter mowed through a solar panel on the Spektr module, colliding with the module and puncturing it.

* Spacecraft sinks on splash-down and the astronaut’s spacesuit fills with water. Happened to Gus Grissom on 21 July 1961 with Mercury-Redstone 4.

Damn, Gravity was a good movie!

Have you seen Gravity yet? What did you think of it?

Copyright © Matthew Wright 2013

OMG – the baddest sci-fi mega-mech…e-v-a-h!

I posted last week about why huge bipedal fighting ‘mechs’ from sci-fi like Pacific Rim are unlikely, unless the laws of physics change.

Copyright (c) Matthew Wright 2004, 2012

An Airfix kit I made of a Mk IV tank – battlefield mech, 1917 era.

But that doesn’t mean sci-fi mechs have to be boring. Not at all.

More in a moment. First off – what’s wrong with a 120-metre x 20-metre biped mega-mech?  Alas, even if you could get your mech to move, it’s a 2400 square metre target balancing on pivot points wa-a-a-ay below its centre of gravity. There are reasons why soldiers don’t stand tall and walk very, very slowly towards the enemy. When it was tried, on the Somme in 1916, the British Army suffered its heaviest one-day losses – ever.

The same’s true of real mechs – main battle tanks. In the First World War, infantry tanks were high-sided. The fact that height made them targets was understood, But the design committee couldn’t compromise on the height of the tracks, because the criteria was for a vehicle able to drive over trenches – dictating a rhomboidal profile equivalent to a 20-metre diameter wheel.

My 'Dragon' model of M. I. Koshkin's T-34. Lighting rig was improvised.

A ‘Dragon’ model of M. I. Koshkin’s T-34. Sits on the shelf beside my writing desk, usually. Lighting rig was improvised.

Inter-war tanks had different criteria but were still high-sided. Then, during the Second World War, sloped armour – again, well known in naval circles – was applied by Mikhail Ilyich Koshkin to his T-34. Modern tanks follow that lead. Tank tactics reflect ‘low is better’ too – a commander looks for places to go hull-down. You can’t do that in a 120-metre high bipedal mech.

So does this mean mech sci-fi has to be dull? Not at all. I’m thinking of the most awesome mech I’ve ever seen in SF – Stanislaw Lem’s Cyclops. Total badass. To one reader, ‘goddamn dynamite, I mean, like whoa.

Best MBT in the world - the Challenger 2. Well, it's British, innit. "It's only a model". "Shh"

Best MBT in the world – the Challenger 2. “Eeee, lad, that’s ‘cos it’s British, innit.” “It’s only a model”. “Shh”. Note the background …the same as the T-34′s.

Get this. Lem’s Cyclops is an autonomous robot weighing 80 tons, 25 feet high, levitated on force fields, protected by ceramic armour and energy fields, with near-inexhaustible energy reserves. It’s armed with an antimatter cannon capable of continuous fire in all directions – annihilating everything in a constant nuclear-yield detonation, soaking the battlefield in relativistic-scale energies and lethally hard radiation.

Here’s Alex Andreev’s visual concept.

It’s from Stanislaw Lem’s The Invincible (1964)I read that novel in 1978 and – setting aside Wendayne Ackerman’s peculiar translation from Polish, via German – it’s total OMG.  Mech-machine evolution…versus humans. And Lem also envisaged the ultimate end; a robot fly (‘grey goo‘). Tiny, individually disposable, always replaceable – available in multi-billions – and able to connect into swarms that were …invincible. Blasting them was like fighting the ocean with swords. The logic pivoted on energy consumption.

That was the ultimate sci-fi mega mech. Infintesimally tiny – yet, vastly huge. Expendable, yet indestructible. Brilliant. But then, Lem’s stuff always is. Here’s part of the sequence where the Cyclops goes into combat with the flies. Lem is one hell of an author! Don’t just take my word for it.  Find a copy of that book and read it – because, my friends, Stanislaw Lem has shown us how mechs are done.

And – more importantly – how we’ll relate to them.

Copyright © Matthew Wright 2013

Next week: My review of Gravity. Before then - NaNo writing tips and advice. Watch this space.

Why is the sky blue? And other annoyingly rhetorical questions

I am often bemused by people who use ‘why is the sky blue’ as rhetoric – often to symbolise some question for which there is no answer.

Actually there is an answer, and we’ve known it since 1871: ‘Rayleigh scattering’. It’s also why sunsets look red and orange. The effect is named after John William Strutt, Third Baron Rayleigh (1842-1919), the British physicist who discovered it.

The phenomenon works like this: incoming sunlight, which contains light of all wavelengths and hence colours, is scattered by molecules in the upper atmosphere. The increasing density of atmosphere itself also acts as a scattering mechanism.  The wavelength of light mostly scattered (technically, absorbed and re-emitted) is at the shorter end – blue and green, creating the diffuse glow across the whole sky which, to the human eye, usually looks light blue.

Other wavelengths are scattered when the light comes at a direct angle, which is why the Sun appears yellow (but don’t look – it will damage your eyes).

This scattered light is also polarised. That’s why a polariser on your camera produces such a dark blue at certain viewing angles relative to the sun.

Oriental Bay - named after one of the original colony ships that arrived in 1840 and a popular walk for Wellingtonians today.

Oriental Bay, Wellington – an image I took with full polarising, creating false-colour blue in the sky.

When the sun angle lowers, and the light is passing through a thicker layer of atmosphere, more of the blue wavelengths are scattered and only the longer wavelengths are obvious – orange and red – hence the colours of sunset, gradiating to a darkening blue above.

Blue sunset on Mars - for the same reason skies are blue on Earth. An approximately true colour image by the Spirit rover at Gusev Crater, 2005. Photo: NASA/JPL, public domain.

Blue sunset on Mars – for the same reason skies are blue on Earth. An approximately true colour image by the Spirit rover at Gusev Crater, 2005. Photo: NASA/JPL, public domain.

This scattering effect is true everywhere – not just on Earth. It varies slightly because atmospheric compositions differ, and the oxygen in our atmosphere is a factor. However, if you were dangling from a balloon in Jupiter’s atmosphere and looked up, you’d see blue sky there, even though the air is mostly a poisonous mix of hydrogen, helium and traces of other stuff like phosphene. Even the sky of Mars is blue – we’ve imaged that blue slice-wise through the upper air. It appears pink from lower down, looking up, because suspended dust in the atmosphere scatters the longer wavelengths. That’s still Rayleigh scattering. And Martian sunsets are blue – for exactly the same reason.

Mars imaged in 1995 by the Hubble Space Telescope - with blue cast due to Rayleigh scattering. Cool. Photo: NASA, public domain.

Mars imaged in 1995 by the Hubble Space Telescope – with blue cast due to Rayleigh scattering. Cool. Photo: NASA, public domain.

Earth’s sky appears blue, I might add, to us. Humans are lucky; our colour vision is based on three receptors. Many animals use two, which reduces the palette of colours they can see. (Of course, most of them also have much better night vision: swings and roundabouts).

So there you have it. Next time anybody idly gets rhetorical and asks ‘why is the sky blue’, you can go all Sheldon on them with an annoying literal answer. Or talk about Martian sunset colours, but I suppose that comes to the same thing really.

Copyright © Matthew Wright 2013

Into the unknown beyond the edge of the solar system

This week’s news that Voyager 1 has left the solar system is pretty cool.

Voyager 1 launching, 5 September 1977. Photo: NASA, public domain.

Voyager 1 launch, 5 September 1977. Photo: NASA, public domain.

Actually, not just cool. Totally awesome.  JPL scientists were able to use Voyager’s ‘plasma wave’ instrument to measure oscillations in plasma around the probe, giving its density; and this week, the plasma science team at the University of Iowa analysed the data and confirmed that the probe had entered interstellar space.

The important part is what it means. For the first time in the 4.6 billion year history of our world, something from Earth has left the solar system.

It is the stuff of dreams.

Not bad for a space probe launched when trousers were flared and disco was in. The day was 5 September 1977. With its twin, Voyager 2, the 770kg probe was the low-budget reality of a ‘grand tour’ that fell victim to post-Apollo penury. And once their Titan-Centaur boosters had exhausted their fuel, the Voyagers were on a rail for the interstellar void. Both had gold records on board – not Bee Gees – recording human endeavour, should the probes ever be found some time.

Picture taken by Voyager 1 of Saturn - a view impossible from Earth, where we don't get that angle on the night side. Photo: NASA, public domain.

Picture by Voyager 1 of Saturn, November 1980 – a view impossible from Earth, where we don’t get that angle. Photo: NASA, public domain.

But both Voyagers were still up for major course changes for free. In the late 1970s, the four major planets – Jupiter, Saturn, Uranus and Neptune – were aligned in such a way that a probe could be lobbed from one to the other, using the gravitational field of each planet to bend the trajectory. Some of the momentum of each world was transferred to the probe, slowing the planet infintesimally, and radically altering the course of the Voyagers.

Voyager 2 flew past all four giant planets. But Voyager 1 encountered only Jupiter and Saturn. By taking a different trajectory, Voyager 1 could get a close look at Titan, Saturn’s largest and most enigmatic moon.

The courses and positions of four probes leaving the solar system, all launched in the 1970s. I made this with my handy Celestia installation - cool, free science package.

The courses and positions of four probes leaving the solar system. I made this with my handy Celestia installation.

That carried a cost. Voyager’s course was twisted out of the plane of the ecliptic, the narrow band in which the planets orbit the Sun. And now – 36 years and 18.6 billion kilometres after launch, Voyager 1 has passed through the heliopause – where the solar wind thrown off by the Sun meets the interstellar medium – and stops.

Voyager probes at the heliopause. Credit: NASA/JPL, public domain.

Voyager probes at the heliopause. Note how the heliopause is compressed, like a bow wave, in the direction the solar system travel as it orbits the galactic centre. Credit: NASA/JPL, public domain.

It’s unknown space. Although the Oort cloud and dwarf planets such as 90377 Sedna, have orbits that go beyond it, the heliopause is a practical line in the sand (well, in the vacuum) for scientific purposes.

Voyager 1 detected that the solar wind had dropped to zero in 2011, meaning it was approaching the border. It’s likely the probe crossed into the interstellar void in August 2012. Certainly it was well into the interstellar medium this year – some 125 times as far away from the Sun as Earth.

It’s worth remembering that these measurements involve detecting miniscule numbers of particles. Despite interesting artistic renderings like the one above,  both heliopause and interstellar medium are hard vacuum, with a density of one atom per cubic centimetre.

The practical mission of both Voyager probes will finish in a decade or so. They are each powered by three radioactive thermal generators, and those are dwindling. By 2025-30 there won’t be enough power to run even individual instruments.  But that won’t stop both hurtling onwards into deepest space until they hit something – or the universe ends, monuments to human endeavour that will last longer, perhaps than our own planet. In 40,000 years, Voyager 1 will come within 1.6 light years of the star Gliese 445 – an M-class dwarf star which, by then, will be a mere 3.45 light years from us. It’s coming towards us faster than Voyager 1′s heading for it.

The whole thing is pretty cool and amazing.

Copyright © Matthew Wright 2013

 

Is there life on Mars – again?

NASA has plans afoot to build a second nuclear powered Mars rover, Curiosity style, and land it on the planet in 2020 with another fireball-and-rocket crane spectacular.

Curiosity landingOnce there it will look directly for signs of ancient life, on the logic that there won’t be any to find easily today. But an older, wetter and more convivial Mars might have been a different story

The rover will even have a box for samples that might be returned to Earth by some later mission.

Which is pretty cool on just about every count. And maybe we’ll get answers to questions that have been burning since long before the dawn of the space age

Assuming, of course, we ask the right ones. That’s been the problem.  When the Vikings landed on Mars in 1976 they were geared to look for life-as-we-know it. The results were ambiguous and likely caused by the perchlorates that we now know saturate the upper layers of the Martian soil.

And therein lay the real issue. On Earth, if one experiment doesn’t work, you devise another and try that, based on what you learned the first time.

Not so easy when you have to transport that repeat experiment to Mars to a chorus of shrinking budgets, where ‘failure’ is likely to kill the next allocation – yet where you might have to follow your Mk II Life Detecting Lab with a third…and a fourth…

Part of the problem was that we didn’t know enough to ask the right questions. Viking’s ambiguous failure threw the issue back to basics. Had Mars even had water? Broadly, that’s where the focus has been since – and now that we have ‘yes’ to a lot of those basic questions, it’s possible to take the next steps.

To me this is a cool application of scientific method – systematically, over decades, and it’s paying dividends.

And we can speculate that even if Mars never had life – or if it did, and it’s gone extinct, it’s likely to have other life soon. Us. Maybe.

Your thoughts?

Copyright © Matthew Wright 2013

Forget Star Wars – here’s the real-life Death Star

It’s in a nebula with the boring name of NGC-3372, and the un-boring name of Homunculus, maybe 7,500 light years from Earth. It’s called Eta Carinae. But you might call it the Death Star.

Eta Carinae. NASA, public domain. Click to enlarge.

Eta Carinae. See that nebula? It’s NGC-3372, also called the Homunculus Nebula – one or two solar masses worth that erupted out of the star in 1843. NASA, public domain. Click to enlarge.

Luckily for us, it’s not pointed our way. We think.

It’s currently a million times more powerful than the Sun, but the output has fluctuated wildly in historic times, like a guttering candle. A major flare that started in 1843 lasted 20 years and made Eta Carinae the next brightest star in the sky after Sirius.

Eta Carinae is 872 times the distance of Sirius. That flare, alone, was as bright as a supernova.

Victorian-age astronomers looked and marvelled. But they didn’t really have the gear that we do. But get this – we can make up for that now. Some of that light was reflected off dust clouds about 85 light years beyond Eta Carinae, from Earth’s vantage point. That ‘echo’ bounced back, whipped past Eta Carinae – and is reaching us now. Let me say that again. We’re picking up light 170 years after we first saw it – by its reflection!  Scientifically, that’s sub-zero cool.

Today the gas blown off in that event appears as a nebula surrounding a blazing blue-white star roiling in pre-hypernova mode.

There are a couple of theories to explain how a hypernova works. Both likely true in different circumstance, but the one that counts is the ‘collapsar’ model. High-mass stars fuse hydrogen around their core at a phenomenal rate. After a while the star starts fusing helium into lithium, and so on up the periodic table until it reaches iron. That’s stable and can’t fuse. So it cools. And then – if the core has more mass Chandashekar’s Limit, extreme things happen, faster than any human could perceive.

Artists impression of a GRB. Zhang Whoosley, NASA, public domain, via Wikipedia.

Artists impression of a GRB. Zhang Whoosley, NASA, public domain, via Wikipedia.

First, the core of the star collapses at light-speed into a black hole. A reflected blast wave erupts at light-speed. The advancing wave intersects with the stellar matter to produce ultra-energetic radiation at gamma frequencies, focussed by the star’s magnetic field and squirted in a beam down its polar axes. Meanwhile, the main blast, following at a more sedate fraction of light-speed, rips the star apart with a glare that can out-shine whatever galaxy the star is inhabiting.

What’s gamma radiation? It’s at the sharp end of the electromagnetic spectrum. Frequencies start at 10,000,000,000,000,000,000 hertz and go up, which gives a gamma burst a wavelength smaller than the diameter of an atom. Gamma ray bursts are among the most energetic phenomena observed. We can detect them in galaxies billions of light years away.

If Eta Carinae blew and its GRB hit us, it’s been calculated that would deliver energy equivalent to one kiloton of TNT in energy for every square kilometre of the hemisphere facing the radiation. Ouch.

Probably it’s not pointed our way, but if Earth was hit by a  burst approaching that intensity, we’d know. A lot depends on energy and duration.  It is unlikely a burst would reach ground level; air is a shield against gamma and x-rays. But part could penetrate at ultraviolet frequencies and burn anybody under it.

The larger problem is gamma radiation hitting the upper atmosphere – smashing the ozone layer, at least. Potentially, a GRB could create nitrogen dioxide smog – plunging Earth into darkness. While this would occur only on the side  struck by the beam, high-altitude winds would spread the effects. And we’d get rain. Nitric acid rain. Here’s the paper analysing the biological effects.

The thing is, while we think Eta Carinae isn’t pointed at us, the Wolf-Rayet star WR-104 might be.

Do I lie away at night worrying? No. Gamma ray bursts are rare. Really big ones happen in the order of once every 100,000 years in the galaxy. Their effects occur in a cone spreading from the poles of the exploding star. The chance of one hitting Earth is remote.

Still, there is a theory that a GRB might have caused the Ordovician-Silurian extinction event about 450 million years ago. Another theory suggests a burst hit us in the eighth century – it didn’t have enough energy to smash everything, but may have caused climate change

Realistically, for us, there are more likely things that will knock off humanity.

Meanwhile, we can look up at the skies and marvel at the wonders of extreme physics we’re discovering…out there.

Copyright © Matthew Wright 2013

Why a supermoon is just, so, well, super

Last night the Moon shone big and bright. A supermoon.

A supermoon happens when the perigee point of the lunar orbit happens to fall at the point furthest away from the sun, so the Moon is fully illuminated as seen from Earth. A sketch I made with the help of Celestia and a drawing tool.

How a supermoon works.  The perigee isn’t always at this point – the alignment happens about every fourteen months. A sketch I made with Celestia and a drawing tool.

A ‘supermoon’ happens when the lunar perigee – the point at which it is closest to Earth – occurs on the side of Earth’s orbit furthest from the sun, which means the lunar disk is fully illuminated from Earth’s perspective. Hence we get a moon that not only has a visual diameter 12 percent greater than that of the Moon at apogee, but which is also full.

The difference isn’t huge. The Moon’s distance varies from about 405,000 to about 360,000 km from Earth.  It doesn’t add much to the tides – a few inches at most – and is a perfectly normal occurrence.

For me it highlights how unique our Moon is. No other planet in the solar system, except Pluto, has a moon that is such a large proportion of its own size. (Don’t get me started on Pluto’s demotion to ‘dwarf’ planet).

Current theory – devised mainly from Apollo data – suggests that the Moon formed about 4.5 billion years ago, and only 30-50 million years after the Solar System began coalescing, when an impactor the size of Mars  - ‘Theia’ – ploughed into the proto-Earth, probably on a slaunchwise angle.

The impact rendered both bodies fragmented and molten. The iron cores of both sank to the centre of the Earth – which is why Earth has such a large one compared to Mars or Venus – while the lighter material coalesced to form the Moon.

A variant explains how the Moon is two-faced – the far side (which gets just as much light as the near side, so we can’t call it ‘dark’) is very different from the side we see. Why? One theory suggests Earth emerged from the impact with two moons which, themselves, subsequently collided. Splat. Later, tidal effects meant that the heavier side – the one we see, with all the maria – ended up facing the Earth.

Which brings me to the last cool link between this supermoon and the history of the Earth-Moon system. Way back when, as the moon coalesced, it was only about 14,000 miles from Earth and both bodies were rotating far more rapidly than today.

Does the Moon rotate, you say? Actually, it does spin – it rotates once in exactly the same time as it takes to orbit the Earth. This outcome is known as ‘tidal locking’ and occurs when a small body – in the Moon’s case, 1/81 times the mass of Earth – orbits a larger one.

Colour photo of the Moon taken by the Galileo probe in 1990 - a view we never see from Earth. The - uh - 'dark side' is to the left, fully illuminated. NASA, JPL, public domain.

Colour photo of the Moon taken by the Galileo probe in 1990 – a view we never see from Earth. The – uh – ‘dark side’ is to the left, fully illuminated. NASA, JPL, public domain.

Each induces tides in the other, robbing each other of rotational energy. Naturally the larger body ‘wins’, though it’s also slowed in the process. The energy doesn’t vanish, of course. It’s turned partly into heat, and then radiated; but it also partly gets translated into orbital momentum.

What this means in practise is that the Moon moves away from the Earth. In about three billion years, it will be far enough away that it doesn’t stabilise the Earth’s axial tilt.

Can Earth ever be tidally locked to the Moon? Theoretically – yes, but apparently it’ll take 50 billion years. The orbital period of the Moon – and the length of our ‘day’ – would be about 47 of our existing days. But it won’t ever happen. Earth will be swallowed up by the Sun, as it turns into a red giant, well before then.

But that’s way off in the future, and I can guarantee humans won’t be around to see it. Unlike today’s supermoon.

Copyright © Matthew Wright 2013

Coming up this week: My take on Eta Carinae, more writing tips, and more.