Finding another Earth isn’t easy. Unfortunately.

Are you looking for a second Earth? We need to – humanity is on the fast track to ruining our one.

Simulated Exo-Earth. A picture I made. Apart from the fractal artefacts, does anybody notice what's wrong with it?

Simulated Exo-Earth. A picture I made. Apart from the fractal artefacts, does anybody notice the science issue that I didn’t correct?

Of course it’s not an easy task. A planet discovered the other week with the help of Kiwi astronomers underlines the problems. Four astronomers here in New Zealand contributed data to the OGLE microlensing follow-up network program in 2012. The results were published recently – and the good news is, OGLE found a planet.

OGLE, incidentally, stands for ‘Optical Gravitational Lensing Experiment’. An apt acronym. It works by exploiting a quirk of Einstein’s theory of relativity – that mass distorts space-time. Massive stars bend light around themselves, acting as ‘lenses’ and enabling us to point a telescope at the massive star, and so detect faint objects passing directly between us and them, that we wouldn’t otherwise be able to observe. The gravity lens around the distant star is known as an ‘Einstein Ring’, and the method is usually used to pick up planets orbiting in the ‘halo’ of a star – the debris orbiting it, like our Oort Cloud. These are known as Massive Compact Halo Objects (MACHOS). Cool or what?

Anyhow, back to the news. The planet is called OGLE-2013-BLG-0341LBb, and it’s about 3000 light years away in the constellation Cassiopeia.

The good news?

- It orbits its sun at 0.8 AU – nearly the distance of Earth (yay!)

- It’s about Earth sized – mass is thought to be only twice ours (yay!)

- That doesn’t imply twice our surface gravity (yay!) [I can't calculate it unless I know the radius and density of the planet, which I don't, but if density is the same as Earth, average 5.5 g cm <exp>3, then the surface gravity won't be double because surface gravity is also proportional to the radius. Just saying.]

- It’s orbiting just one star in a binary pair (Tattooine, sort of – yay!)

Let me illustrate mass vs surface gravity. Although it has a mass 14.5 times that of Earth, 'surface gravity' on Uranus is just  89 percent that of Earth. That's because the radius is about 4 times Earth's. I made this picture with Celestia.

Let me use Uranus to illustrate mass vs surface gravity. Although it has a mass 14.5 times that of Earth, ‘surface gravity’ on Uranus is just 89 percent that of Earth. That’s because the radius is about 4 times Earth’s. I made this picture with Celestia.

So is this Earth 2? Well, if I were you I’d take warm clothes. The bad news is that the star is a red dwarf, 400 times less energetic than the Sun, so the planet has a surface temperature of 60 degrees Kelvin – in centigrade, a chilly -210 degrees. (Booooo!)

The search for Earth-like planets has got exciting lately as we’ve developed the tech to discover them. Problem is, the gear is not good enough to image them directly. We can’t learn much other than the size and orbital distance – from which we can derive its year, mass and temperature. If we’re lucky, we might also get a handle on its atmospheric makeup, via spectrography as it transits its sun.

For these reasons, usually when we detect a planet that’s otherwise in the ‘goldilocks’ zone, we don’t know whether it’s actually like Earth. It might be like Venus – runaway greenhouse with sulphuric acid, crushing atmosphere and oven-like temperatures. We don’t know. Don’t forget, if astronomers 3000 light years away were using the same techniques to analyse our solar system, they might conclude there were two Earths here from the planetary mass and orbital data.

The way things are going, of course, we’re likely to end up with two Venuses. Venuses? Venii? You know what I mean.

And it’s a worry.

Copyright © Matthew Wright 2014

Flying saucers and other aerial crockery

A UFO was caught over the South Island the other week by an Australian film crew. By “UFO” I mean “unidentified object” which was “flying”. We don’t know what it was – and the objects could have been an artefact of the video.

Jupiter rising over Io - a picture I made with my Celestia installation

Jupiter rising over Io – a picture I made with my Celestia installation

Needless to say, I am certain they weren’t alien spacecraft, any more than any other UFO is.

I can hear the howling. ‘But the universe is big, surely other planets must have life?’

Sure. Space is enormous.  No doubt life’s emerged elsewhere. But – again – it doesn’t follow that the aliens have developed civilisation, jumped into spacecraft, and flown here. It particularly doesn’t follow that they’ve done so merely to lurk mysteriously on the edge of our vision, violating cows, revealing themselves to lone witnesses on dark country roads, and so on. Or that they’d be big-headed, big-eyed, child-bodied versions of us with an ethical view that fixes the faults of western society.

The fact that lay-people presented with partial evidence can’t explain an observed phenomenon doesn’t prove it’s an alien spaceship. The fact that science can’t explain it from partial data doesn’t, either. That’s false-premise logic.

I’ve seen plenty of weird aerial stuff myself. The best was over Wellington in April 1986, when I spotted a slow-moving fireball parallel to the southern horizon, shedding sparks. I knew what it was. The thing was moving in the direction I’d expect from the usual orbital paths, the only ‘unidentified’ part was whether it was US or Soviet.

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. NASA, public domain, via Wikipedia.

To me the phenomenon of ‘space aliens’ is a product of the way western culture is conditioned to think. The trigger was the mid-twentieth century assumption that Earth was archetypal and that every world capable of supporting life would bear one intelligent species, probably a bipedal hominid. In due course, this would become civilised, space-faring and visit other worlds. Just like Europe’s explorers during the age of exploration.

It is no coincidence that we decided aliens were visiting just as we began to take spaceflight credibly. The idea emerged in June 1947 when US pilot Kenneth Arnold reported nine boomerang-shaped objects paralleling his aircraft near Mount Rainier. A journalist misquoted that as ‘saucers’, which promptly became the shape of the interlopers thereafter. The origin of that shape as a journalists’ misquote was rather lost amid the flood of blurred photographs of aerial lampshades that fringe enthusiasts were subsequently able to provide as proof of their own encounters.

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. NASA/JPL, public domain.

These 1950s-era aliens came from Mars or Venus and looked like us, only with handy super-powers such as telepathy. Alas, the Mariner and Venera probes of the 1960s revealed Venus was a runaway greenhouse oven – and Mars was a cold, cratered world without breathable air. Luckily it turned out, after that discovery, that the aliens really came from well-known stars on the school science curriculum, like Aldebaran. Then in 1978 Stephen Spielberg’s Close Encounters of the Third Kind hit the cinema, and the current alien trope followed.

You get the picture.

My take? We have had civilisation for an eye-blink against the age of the Earth. It may only last another eye-blink, by that scale. Who says aliens have the same capability at the same time? They might have flourished and gone a billion years ago. Or their time might be a billion years in the future.

Space is also immense. Who says they’d find us anyway? Or that we could be important? To give that a sense of proportion, our sun’s invisible, without telescopes, from just under 60 light years.* I’ve heard it argued that ‘they’ could hear our transmissions – TV, radio, radar and so on. Actually, we’re just as invisible that way too. In theory I Love Lucy – which began transmission in 1951 – has just reached the planet we photographed, orbiting Beta Pictoris, 63 light years away. Actually our broadcasts, even high-frequency radars, don’t get that far because of the inverse square law, coupled with natural background radio noise. Our stuff’s lost in the static. Yet our galaxy is 100,000 light years across. Feel small? You should. And if aliens did arrive, would we recognise them as life? Or be able to communicate? They’re alien, remember. Maybe they’d be too busy talking to their own kind – you know, other algae.

Put another way – sure, we see stuff in the sky we can’t explain. But that doesn’t mean it isn’t explicable. Or that ‘aliens’ are among us.

Thoughts?

Copyright © Matthew Wright 2014

 

* Geek time. Muahahahaha. Stellar brightness is measured by magnitude, an inverse scale in which lower is brighter. The true magnitude of a star is its absolute magnitude. But this fades with distance (inverse square law), so its visual magnitude, the brightness we see from a distance, is less. This is known as the apparent magnitude. Any star of apparent magnitude greater than about 6 is invisible to the average naked eye. The distance where the apparent magnitude (m) fades to invisibility can be calculated from the absolute magnitude (M) using the distance modulus equation r = 10<exp>((m-M)/5+1) where r is the distance in parsecs. If you apply that to the Sun, absolute magnitude 4.83, you discover it fades to apparent magnitude 6 at about 57 light years, which is about 0.057 percent the diameter of the galaxy.

 

 

My hypothesis that English is a loose language

I’ve always thought English is a loose language. Take the words ‘theory’ and ‘hypothesis’, for instance. Even dictionary definitions sometimes mix their meanings up.

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 the Special and General Theories of Relativity. Public domain, via Wikimedia Commons.

Scientifically, the word ‘theory’ means a ‘hypothesis’ that has been established to be true by empirical data. Take Einstein’s two theories of relativity, Special (1906) and General (1917). We call them ‘theories’, by name, but everybody with a GPS-equipped cellphone or GPS system encounters proof that Einstein was right, every time they use it.

This is because GPS satellite clocks have a correction built into them to cope with Special Relativity time dilation that occurs because they’re moving at a different velocity than the surface of the Earth. It’s miniscule –  6 millionths of a second loss every 24 hours. There’s also the need to cope with General Relativity time acceleration relative to the surface of the earth, because they’re in orbit, putting them further away from the mathematical centre of Earth’s mass than we are on the surface of the planet. That totals 45 millionths of a second gain every 24 hours.

If all this sounds supremely geeky and too tiny to worry about, millionths of a second count,  because its on differences at that order of magnitude that GPS calculates positions. If the net relativity error of 39 millionths of a second every 24 hours wasn’t corrected, GPS would kick up positional errors of up to 12 km on the ground. Einstein, in short, was totally right and if we didn’t use Einstein’s equations to correct GPS, we’d be lost. Literally. Yet we still call his discovery a ‘theory’.

Hypothesis,on the other hand, is the idea someone comes up with to explain something. Then they run tests to figure out the rules. Take gravity. Everybody knew it existed. However, Newton figured he could come up with rules – his hypothesis. Once Newton had a hypothesis, he was able to run experiments and sort out actually how it worked – creating his theory of gravity.

Neptune. A picture I made with my trusty Celestia installation (cool, free science software).

Neptune. Discovered by mathematics, thanks to Newton’s theories. A picture I made with Celestia (cool, free science software).

One of the reasons why these explanations are called ‘theory’ is because science sometimes finds refinements. Einstein’s theory of General Relativity is also a theory of gravity, integrating the extremes of time and space Einstein described in his Special theory. It replaced Newton’s theory. But that didn’t mean Newton was wrong in the terms he observed and described. On the contrary, his equations still work perfectly for the things around which he developed the theory.

So in the strictest sense, ‘hypothesis’ means ‘how we think things work’, while ‘theory’ means ‘how we’ve shown things to work’. Science sometimes creates supersets of theories, like onion skins, that explain things differently – but usually don’t invalidate the core of the earlier theory.

And my hypothesis, which I think should be elevated to theory status on this evidence, is that English is a pretty loose language. Thoughts?

Copyright © Matthew Wright 2014

 

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The science behind this year’s blood moons

Well, the first ‘blood moon’ of 2014’s come and gone. I missed it – the night sky where I live was socked in with 10/10 overcast at an altitude of about 200 metres.

US Navy photo of a total lunar eclipse in 2004, by Photographer's Mate 2nd Class Scott Taylor. Public domain, via Wikipedia.

US Navy photo of a total lunar eclipse in 2004, by Photographer’s Mate 2nd Class Scott Taylor. Public domain, via Wikipedia.

Still, I’ll have another chance on 8 October. And another on 4 April 2015. And a fourth on 28 September that year.

Although unusual, it’s not a unique occurrence to have four eclipses in quick succession. Technically they’re known as a tetrad.

The reason why eclipses are a bit erratic is interesting. A lunar eclipse is simple enough – the Moon passes through the shadow of the Earth. The reason lunar eclipses don’t happen every 27 days, as the Moon orbits the Earth, is because the Moon doesn’t always pass through the shadow when it’s ‘behind’ the Earth relative to the sun. It would if everything was lined up flat on the same plane – but it isn’t.

In fact, the Moon’s orbit is tilted relative to the ecliptic – the plane in which Earth and Sun orbit. The tilt varies between 4.99 and 5.30 degrees. The two points at which the orbit intersects the ecliptic are known as ‘nodes’, and they move around the Moon’s orbital path – technically, ‘precess’ – at a rate of  19.3549° annually.

For an eclipse to occur, the node (‘ascending’ or ‘descending’) has to coincide with the point where the Moon would pass through Earth’s shadow (which is on the ecliptic). That happens every 173.3 days. An eclipse is possible at that time, though again, the orbital mechanics don’t always mesh exactly.  There are more factors than just ecliptic and orbital angle. Earth’s shadow has a dense part (umbra) and a less dense part (penumbra). Sometimes there is only a partial eclipse. Sometimes it’s total.

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.

The interlocking mechanisms of orbital mechanics – the way Earth, Sun and Moon all move in a complex dance of planes, angles and distances – means we end up with circumstance where strings of lunar eclipses – like the current tetrad – cluster. Between 1600 and 1900, for instance, there were no tetrads. But this coming century, there will be 8 of them.

So why red? The answer is one of the reasons why science is so cool. If you were standing on the Moon during a lunar eclipse, you’d see the Earth as a dark circle rimmed with fire – the light of every sunset and sunrise happening on Earth, all at once.

It’s red because of Rayleigh scattering – the way that the atmosphere scatters particular frequencies of light. I won’t repeat the explanation here – check out my earlier post.  Suffice to say, when sunlight passes through a horizontal thickness of atmosphere, the red wavelengths are what emerge – and those red light wavelengths refract into the shadow of Earth, lighting the Moon in blood-red hues.

So when you see a ‘blood moon’, what you’re actually seeing is the reflected light of every sunrise and sunset on Earth, all at once.

And that, my friends, is the really neat thing about those eclipses. Harbingers of doom? To me it’s cool science, on so many levels.

Copyright © Matthew Wright 2014

 

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The Big Bang theory wins again. So does Einstein.

It’s a great time to be a geek. We’re learning all sorts of extreme stuff. There’s a team led by John Kovac, from the Harvard-Smithsonian Center for Astrophysics, who’ve been beavering away on one of the fundamental questions of modern cosmology. The secret has demanded some extreme research in an extreme place. Antarctica. There’s a telescope there, BICEP2, that’s been collecting data on the cosmic background temperature. Last week, the team published their initial results.

Timeline of the universe - with the Wilkinson Microwave Antisotropy Probe at the end. Click to enlarge. Public domain, NASA.

Timeline of the universe – with the Wilkinson Microwave Antisotropy Probe at the end. Click to enlarge. Public domain, NASA.

The theory they were testing is as extreme as such things get and goes like this. Straight after the Big Bang, the universe was miniscule and very hot. Then it expanded – unbelievably fast in the first few trillionth trillionths of a second, but then much more slowly. After a while it was cool enough for the particles we know and love today to be formed. This ‘recombination’ epoch occurred perhaps 380,000 years after the Big Bang. One of the outcomes was that photons were released from the plasma fog – physicists call this ‘photon decoupling’.

What couldn’t quite be proven was that the early rate of expansion – ‘inflation’ – had been very high.

But now it has. And the method combines the very best of cool and of geek. This early universe can still be seen, out at the edge of visibility. That initial photon release is called the ‘cosmic microwave background’ (CMB), first predicted in 1948 by Ralph Alpher and others, and observed in 1965 by accident when it interfered with the reception of a radio being built in Bell Laboratories. That started a flurry of research. Its temperature is around 2.725 degrees kelvin, a shade above absolute zero. It’s that temperature because it’s been red-shifted (the wavelengths radiated from it have stretched, because the universe is expanding, and stuff further away gets stretched more). The equation works backwards from today’s CMB temperature, 2.725 degrees Kelvin, thus: Tr = 2.725(1 + z).

The COBE satellite map of the CMB. NASA, public domain, via Wikipedia.

The COBE anisotropic satellite map of the CMB. NASA, public domain, via Wikipedia.

The thing is that, way back – we’re talking 13.8 billion years – the universe was a tiny fraction of its current size, and the components were much closer together. Imagine a deflated balloon. Splat paint across the balloon. Now inflate the balloon. See how the paint splats move further apart from each other? But they’re still the original pattern of the splat. In the same sort of way, the CMB background pattern is a snapshot of the way the universe was when ‘photon decoupling’ occurred. It’s crucial to proving the Big Bang theory. It’s long been known that the background is largely homogenous (proving that it was once all in close proximity) but carries tiny irregularities in the pattern (anisotropy). What the BICEP2 team discovered is that the variations are polarised in a swirling pattern, a so-called B-mode.

The reason the radiation is polarised that way is because early inflation was faster than light-speed, and the gravity waves within it were stretched, rippling the fabric of space-time in a particular way and creating the swirls. Discovering the swirls, in short, identifies both the early rate of expansion (which took the universe from a nanometer to 250,000,0000 light years diameter in 0.00000000000000000000000000000001 of a second…I think I counted right…) and gives us an indirect view of gravitational waves for the first time. How cool is that?

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.

What’s a ‘gravitational wave’? They were first predicted nearly a century ago by Albert Einstein, whose General Theory of Relativity’of 1917 was actually a theory of gravity. According to Einstein, space and time are an entwined ‘fabric’. Energy and mass (which, themselves, are the same thing) distort that fabric. Think of a thin rubber sheet (space-time), then drop a marble (mass/energy) into it. The marble will sink, stretching the sheet. Gravitational waves? Einstein’s theory made clear that these waves had to exist. They’re ripples in the fabric.

One of the outcomes of last week’s discovery is the implication that ‘multiverses’ exist. Another is that there is not only a particle to transmit gravity, a ‘graviton’, but also an ‘inflaton’ which pushes the universe apart. Theorists suspect that ‘inflatons’ have a half-life and they were prevalent only in the very early universe.

There’s more to come from this, including new questions. But one thing is certain. Einstein’s been proven right. Again.

Copyright © Matthew Wright 2014

Coming up: More geekery, fun writing tips, and more.

Into deepest time with the REAL big bang theory

My wife occasionally calls herself ‘Penny’, as in Penny off The Big Bang Theory. Especially when I get together with my mathematician friends and we talk geek.

I’m not sure which of us is meant to be Sheldon. Anyway, the ‘big bang’ theory itself was first proposed in 1927 by a Catholic priest, Monseigneur Georges Henri Joseph Édouard Lemaître (1894-1966). He was trying to explain Vesto Slipher’s discovery that distant galaxies were retreating. And he was ignored. Then, in 1929, Edwin Hubble (1889-1953) suggested the same thing. Like most academic fields, physics is all to do with in-crowds; when Hubble spoke, other physicists pricked up their ears.

Timeline of the universe - with the Wilkinson Microwave Antisotropy Probe at the end. Click to enlarge. Public domain, NASA.

Timeline of the universe – with the Wilkinson Microwave Antisotropy Probe at the end. Click to enlarge. Public domain, NASA.

Their logic went like this. Distant galaxies appear redder than they should.  This is because the wavelengths of light and other electromagnetic emissions from them are being stretched from our perspective, meaning they must be moving away. This effect was first discovered by Ernst Doppler who realised this was why fast-moving vehicles go ‘neeeeoooww’. The sound waves are being stretched from the perspective of a stationary listener as the source moves away, so to them the pitch appears to drop. (You can buy a Sheldon costume so you can be the Doppler Effect, like he was in Series 1 Ep. 6…here.)

It works the same with electromagnetic emissions, and red has a longer wavelength than other visible light, so things moving away appear redder to us. Hence the term ‘red shift. It’s used to describe the phenomenon, even if the wavelength isn’t visible light. (No costumes for this one).

Hubble discovered not only that distant galaxies retreat from us, but that the further away they are, the faster they retreat. Hubble’s Law followed: v = H0D, where v is velocity of recession, Ho is Hubble’s constant, and D is the proper distance. The value for Hubble’s constant has never been agreed, but recent work suggests it might be 71 +/- 7 km/sec per megaparsec. Probably. A bit.

It also turned out that distant galaxies are moving away from us whichever way we look, showing that space-time itself is expanding. Imagine a rubber balloon with equidistant dots on it. Inflate the balloon. The dots move apart equally – and the distant ones are moving away faster. That holds true for space-time.

The conclusion was that the universe had been smaller – a mathematical point, in fact, from which everything exploded into the reality we know and love today. Pretty much like the opening credits on The Big Bang Theory, in fact.

Of course, it wasn’t expansion into a void. It was an expansion of space-time itself. The very fabric of physical reality.

It was a kind of cool idea, but nobody had any way of proving it. Physicists argued over whether there had been a ‘big bang’, or whether the universe operated by a modified ‘steady state’ of constant but expanding existence. Then, in 1948, Ralph Alpher and Robert Herman predicted that we should be able to see cosmic background radiation from the ‘big bang’ – and it was found in 1965. The radiation has a black body (idealised) temperature of 2.72 degrees Kelvin, give or take a tad (I define +/- 0.00057 degrees as a ‘tad’).

Into deepest space: Hubble space telescope image of galaxies from the early universe. Public domain, NASA.

Into deepest space: Hubble Space Telescope image of galaxies from the early universe. Public domain, NASA.

And you know the coolest part? Albert Einstein figured it all out in 1917, before any of the evidence was available. His General Theory of Relativity made clear the universe couldn’t be static – it had to be expanding or contracting. Einstein thought that had to be wrong, so he added a ‘cosmic constant’ to eliminate the expansion. But expansion was true, and he later admitted the ‘constant’ fudge was a mistake. His original equations held good.

Einstein had, in short, figured out how the universe worked – so completely that his theory explained the bits that hadn’t been discovered yet.

How cool is that?

Copyright © Matthew Wright 2013

Coming up soon: ‘Write it now’ and ‘Sixty Second Writing tips’, more humour, more science…and, more.

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

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