Time’s no illusion – unlike gravity. Weird but true!

It seems axiomatic these days, especially among the quantum woo set, to call ‘time’ an illusion – a perception. Of course this is scientific rubbish. There’s no question that humans perceive time in many ways, but in terms of physics time IS real, independent of how we sense its passage.

Solar flare of 16 April 2012, captured by NASA's Solar Dynamics Observatory. Image is red because it wa captured at 304 Angstroms. (NASA/SDO, public domain).

Solar flare of 16 April 2012, captured by NASA’s Solar Dynamics Observatory. Image is red because it wa captured at 304 Angstroms. (NASA/SDO, public domain).

Unlike gravity. That’s the irony, you see. Gravity’s an illusion? Why? Short answer is that the universe is actually weirder than the woo brigade know. Let me explain. According to our friend Albert Einstein, gravity doesn’t exist as a force. Of course, you might have a bit of difficulty imagining gravity is an illusion if you’ve just gone for a gutser down the front steps. But trust me – it is.

Here’s how it works.

Einstein’s Theory of General Relativity – coming up for its centenary and proven to be true, without exception, every time it’s tested – shows that space and time are one entity. A four-dimensional reality with up-down, left-right, forward-back and time.

This space-time fabric is distorted by mass/energy (the same thing in terms of how the universe works). The usual metaphor is to imagine a rubber sheet. Mass/energy can be envisaged as a bowling ball dropped into the sheet. It’ll sag, stretching and curving the rubber.

This rubber sheet, remember, reflects not just space but also time. Consequently, a large mass (or a lot of energy) alters the rate at which time passes. You experience that every day on your phone – its GPS relies on GPS satellites, which have to account for the difference in the rate of time between Earth’s surface and the altitude the satellite’s orbiting at. Time dilation is also caused by the velocity difference between the satellite and Earth’s surface – a function of Einstein’s earlier theory, Special Relativity – which adds to the mix.

GPS works by micro-precise time measurement. If the satellites didn’t take account of Einsteinian frame-dragging, they couldn’t pin the position of your phone to a few metres.

So. Time’s real. What about gravity? Well, that’s the kicker. All-round smart guy Sir Isaac Newton, co-inventor of calculus among other things, identified a relationship between mass and gravity. The larger the mass, the more gravity it has. Simple.

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.

Newton’s theory worked perfectly well, even allowing mathematicians of the early nineteenth century to predict the presence of a new planet – Neptune – from the way it affected Uranus’ orbit. But there were points where it didn’t work. Mercury had orbital characteristics that couldn’t be fully explained by the tugs of all the known planets.

For a while, astronomers theorised there was another world inside Mercury’s orbit – Vulcan. But it could never be found. And then Einstein’s theory came along, and the whole need for Vulcan went away.

Gravity, Einstein explained, wasn’t a force at all. It was a function of mass, sure – but not quite the way Newton thought.

Instead, Einstein calculated, gravity was an effect of the curvature of space-time. Particles would always try to take the shortest route between two places. However, if space-time was curved, they’d be forced to take a curved path. The difference was what we perceived as gravity, an effect intimately associated with mass or – and this is the kicker – energy.

Energy? Sure. Special Relativity showed that mass and energy were different aspects of the same thing (a little mass = a LOT of energy – and go on, you KNOW the equation).

Enough energy, in short, would also distort space-time and, in effect, create its own ‘gravity’. And this was where Mercury came in. The pertubations in its orbit, according to Einstein, weren’t caused by a hidden planet. They were caused by the energy of the Sun itself, acting as an additional distortion in space-time. In 1919 that prediction was borne out when some very precise measurements were taken of Mercury’s position during a transit of the Sun. It was exactly where General Relativity said it should be, if gravity was actually a product of the curvature of space-time.

This was the first proof of the theory – and, as we’ve seen, it’s been shown to be true every which way, ever since.

Gravity, in short, wasn’t a force of itself; it was a function of the way space-time was distorted by mass/energy. This also explained why you couldn’t have anti-gravity, because gravity wasn’t a real force with polarity. It was a structural product of the way the universe worked, but not something real of itself.

The biggest question that came out of this, of course, wasn’t whether gravity was real, which it obviously wasn’t – but why time seemed to move only in one direction. And that’s something that hasn’t been answered. Yet.

More soon.

Copyright © Matthew Wright 2015

A chat with Elvis about Nibiru and other woo

Every other Tuesday, Elvis* – who’s living on Mars disguised as a walrus – drops in for a burger from the slider joint just down the road, because nobody on Mars knows how to make a good one. This week, as we chowed down on Chicken Anchovy Supreme, I mentioned that somebody’d posted a comment on my blog about Scholz’s Star – the red dwarf that skidded past the solar system around 70,000 years ago.

Conceptual picture I made of a red dwarf with large companion using my trusty Celestia installation.

Conceptual picture I made of a red dwarf with large companion using my trusty Celestia installation.

By this guy’s proposal the star – sorry, ‘Nibiru’ – hosted a planet with intelligent life who’d come to Earth and coded secrets into our genes, and he pointed me to a website that – er – proved it.

Actually, when I looked at the site, it was filled with stuff about aliens – aka Sumerian gods – wanting to steal Earth’s gold in order to warm their planet. A prelude, I suppose, to the way aliens always wanted to steal women and water in the 1950s.

Elvis wasn’t worried. Between mouthfuls, he told me this sort of argument is common enough among the woo brigade. There’s no point trying to counter-argue using science because the people who peddle this stuff believe what they say as an act of their own faith in it and merely get angry if you question it.

I still thought science might offer something and pointed out that red dwarfs are the smallest and most innocuous looking stars ever, but they have an unfortunate habit of suddenly exploding into a wild fury. Their brightness can increase 400 times or more on the back of a major flare. They make our local solar flares, even the biggest, look feeble. And if you’re in the way of that licking – well, there you are, an innocent little cell just starting out on the evolutionary tree, and suddenly you get the world’s worst dose of radiation poisoning and die. Oops.  And before life can re-develop, the broken bits get radiated. And again…and again…and again…

Solar flare of 16 April 2012, captured by NASA's Solar Dynamics Observatory. Image is red because it wa captured at 304 Angstroms. (NASA/SDO, public domain).

Solar flare of 16 April 2012, captured by NASA’s Solar Dynamics Observatory. Image is red because it was captured at 304 Angstroms. (NASA/SDO, public domain).

That happened on early Earth, too, when our Sun was young and boisterous. Life didn’t start developing until after the Sun had stopped lashing us. Turns out that life needs a stable environment. Red dwarfs don’t offer one – ever. And that, I explained to Elvis, was quite apart from the fact that alien life is – well, alien. The chances of an alien planet producing a biota identical to ours is pretty low.

Not to mention that Scholz’s Star is orbited by a brown dwarf companion at the distance of Venus – a companion that has three-quarters the mass of the star, meaning they’re actually orbiting a mutual point in space where their gravitation balances, the barycentre. Planets could stably orbit the barycentre, providing they were further out again – but that would put them too far away to have human-type life on them.

And the other problem is the travel. Sure, Scholz’s Star came close by astronomical standards. But that’s the point. Astronomical. It never came closer than 0.82 light years. Yup, light – the fastest thing you can get – still took eight-tenths of a year to reach it. In everyday terms, that’s 7,800,000,000,000 kilometres. Woah! As I told Elvis, our fastest space probe, New Horizons, would take 16,000 years to cross that distance.

He nodded throughout. Obviously he didn’t dispute it. But I hadn’t addressed his basic point.

‘The problem,’ Elvis suddenly said, ‘is that as a species we humans suffer terrible delusions about self-importance.’

‘Don’t say that too loudly,’ I said ‘you’ll upset people.’

‘What do I care? I live on Mars.’ He crumpled his burger wrapper.

‘Tuesday week?’

‘Yeah.’

Copyright © Matthew Wright 2015

*Well, he says he’s Elvis, anyway. But even if he’s AN Elvis (as I actually suspect) rather than THE Elvis, who cares? He talks sense, which isn’t bad for someone who lives on Mars most of the time and has to hide inside a walrus costume to avoid being mobbed by Elvis impersonator fans.

How Stephen Hawking reconciled the irreconcilable

I finally caught up with The Theory of Everything the other week – an awesome biopic about Stephen Hawking, the British physicist whose life’s goal is to find a theory – a single equation – that explains – well, everything. And what they didn’t mention in the movie is that he’s already made the first big discovery along that path.

The Horsehead nebula, Barnard 33, as seen by Hubble. Wonderful, wonderful imagery.

The Horsehead nebula, Barnard 33, as seen by Hubble. Wonderful, wonderful imagery.

Let me explain. There are two main theories of the universe. Albert Einstein’s ‘General Theory of Relativity’ of 1917 totally explains space-time – the macro-scale universe. Quantum physics, which emerged a little later at the hands of Paul Dirac, Max Planck, Neils Bohr and others, works brilliantly in the micro-world – specifically, scales around a Planck length (1.61619926 × 10-35  metres). But the two don’t play nicely together. Not at all.

So far, nobody’s been able to reconcile them – despite the profusion of hypotheses such as string theory, where the maths work out fine, but where nobody has been able to find any evidence to prove it. (I can’t help thinking this is why Sheldon is a string theorist…)

Finding a ‘theory of everything’ has long been Hawking’s goal; and with Jacob Bekenstein he was the first to discover a way in which both Einstein’s General Relativity and the Copenhagen interpretation of quantum physics could work together. They found that way in 1975, at the extreme edge of the possible – inside a black hole. Here’s Hawking’s original paper, ‘Particle Creation By Black Holes’ Commun. math. Phys. 43, 199—220 (1975).

A bit of explanation first. A ‘black hole’ is actually a ‘singularity’, a mathematical point where the curvature of space-time becomes infinite. The normal laws of space-time – the ones our friend Albert Einstein described – totally fail at that point. Even causality doesn’t apply. As Hawking once pointed out in a lecture, we can’t even imagine what might happen inside a singularity (he suggested a singularity could emit Cthulthu – it wouldn’t violate the laws of physics. I disagree. I can’t even pronounce Cthulthu. I think it would emit Sauron instead.)

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

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

Luckily for us, the everyday universe is shielded from singularities by the event horizon – the point where the escape velocity of the singularity exceeds light-speed. Stuff can fall in. But nothing gets out. Hence the term ‘black hole’. Hawking disputed that. Quantum theory states that particle pairs – positive and negative – are always appearing out of nowhere, then annihilating each other. It doesn’t violate thermodynamics because the net energy outcome is still zero. The effect is known as ‘quantum vacuum fluctuation’.

What I’m about to describe is the heuristic overview – the physics of it is complex and involves some mind-exploding mathematics (‘Bogoliubov transformations’). Basically, Hawking reasoned that if a quantum vacuum fluctuation occurred on the event horizon, there was a chance that one particle, the negative, would be drawn in while the other escaped. They couldn’t annihilate each other, because nothing can escape the horizon. Being negative, the falling particle would reduce the mass of the black hole. Meanwhile the positive particle would escape – effectively as heat – from the black hole.

The result was that ‘black holes’ weren’t actually the black dead ends previously imagined. They were glowing. And they’d eventually evaporate. And THAT is Hawking Radiation.

This also meant that black holes had life limits, and while larger-mass holes had lifespans measured in billions of years, small ones would disappear quickly – which, incidentally, is why nobody’s worried about forming one with a few tens of particles in the Large Hadron Collider at CERN, which is about to be deployed at full power for the first time this year. It’d evaporate in way less than a microsecond. And so Hawking showed that, yes – at least in this extreme case – quantum physics and Einsteinian determinism could play nicely together.

The next question was whether the two could be reconciled in more everyday terms. And that’s been the stalling point. But if anybody can solve it – well, I figure it’ll be Hawking.

Copyright © Matthew Wright 2015

Getting winked at by a mystery star! Really

The latest wow-find from astronomers has snuck up on us by stealth. A small red dwarf star discovered in November 2013 by German astronomer Ralf-Dieter Scholz looked, first off, to be pretty ordinary.

Conceptual picture I made of a red dwarf with large companion using my trusty Celestia installation.

Conceptual picture I made of a red dwarf with companion using my trusty Celestia installation.

It even had a boring name: WISE J072003.20−084651.2, courtesy of being found lurking in data collected by the WISE Satellite. It is estimated to be 19.6 light years distant – in our neighbourhood, as stars go, but not exceptionally close. It has around 86 times the mass of Jupiter, making it a M9.5 class red dwarf, one of the smallest possible.

It is orbited – at the equivalent distance of Venus – by a ‘brown dwarf’ companion, a body with 65 times the mass of Jupiter. This world is warmed to near-luminescence by gravitational compression and – potentially – deuterium fusion, but isn’t massive enough to trigger hydrogen-1 fusion and light up like its star.

Yawn. Red dwarfs are the most common stars around. Proxima Centauri, the closest star to the Sun, is a prime example. In fact, of the 60 stars known within 16.3 light years, 46 are red dwarfs. We’re finding lots in our neighbourhood lately because many are so cool and dim – by stellar standards – they’re invisible even to high-powered telescopes. It takes satellites with sensitive infra-red detectors to pick them up. Brown dwarfs are also appearing to these instruments – singly, or orbiting stars that (wait for it) are often red dwarfs.

Since 2013, though, Scholz’s Star has rung alarm bells. First was its proper motion – the way it tracked tangentially across the sky, relative to other stars. Eric Mamajek of the University of Rochester in New York led a team looking into that, using data collected by the South African Large Telescope and the Las Campanas Observatory’s Magellan telescope in South America. They discovered the proper motion was very slow. But the star itself had very high radial velocity – its actual speed. Around 83 kilometres a second, in fact – four times the usual velocity of stars in this part of the galaxy.

This added up to a star that was travelling fast – but which from our viewpoint didn’t appear to be moving. That’s no paradox – imagine you’re looking up a straight road at a car disappearing into the distance. It’s moving fast, but from where you’re standing, it isn’t moving left or right (‘proper motion’). That’s because it’s moving directly away – and that’s true of Scholz’s Star.

Comparison between stars and brown dwarfs. Not strictly to scale. Public domain, NASA/JPL/Caltech.

Comparison between stars and brown dwarfs. Not strictly to scale. Public domain, NASA/JPL/Caltech.

Mamajek and his team ran 10,000 mathematical simulations to find out how close it had been. And – just announced this month – they discovered that, some 70,000 years ago, Scholz’s Star skimmed past our solar system. With a closest approach of just 0.82 light years – some 52,000 times the distance of Earth from the Sun – it banged through the outer fringes of the Oort cloud, the icy cloud of debris left over from the formation of our solar system, which extends out to a light year or so.

The star was far too small and far too distant to affect the orbits of the Sun’s planets. Here on Earth, the Moon has 2,000,000,000,000,000 times the tidal effect exerted by Scholz’s Star at closest approach. But it will have perturbed some of the the ice-and-dirt clusters of the Oort cloud.  Passing stars are thought to do this every so often, and it’s thought that Scholz’s Star was far from the most serious. Some material will probably have been lobbed sunwards, and will still be on their way in – meaning there will be a small scattering of comets arriving in about 2,000,000 years. Yah, we’re talking about astronomy here – which means having a barrel full of zeroes by your desk.

Did ancient humans see the star? If we draw a circle around the Sun at 100,000 times Earth’s distance and plot Scholz’s Star’s path through it, we find the star took around 10,000 years to traverse that line. Back then it had huge ‘proper motion’ by stellar standards – enough to move across the sky by the angular width of the full Moon in 26 years.

But even at closest approach Scholz’s Star would have been around 11.8 magnitude and thus utterly invisible to the naked eye. But the thing about red dwarfs is that they’re often magnetically unstable – and emit huge flares. In some cases that can increase the brightness of the star, briefly, about 400 times. That would have been enough to make it visible as it tracked through our skies – intermittently. The jury’s out on Scholz’s Star, but Mamajek has speculated that it probably did flare regularly.

Yup, Scholz’s Star was probably winking at us. Which is kind of cool. And begs a question – what would happen if a star came even closer? More soon.

Copyright © Matthew Wright 2015

Why I think Mars One is a really stupid notion

I posted last week about the silliness of trying to colonise Mars on a one-way basis, unless you’re sending Justin Bieber.

Sure, most colonists here on Earth made the trip one-way. But Earth’s way more hospitable. Even Roanoke. You can breathe the air, for a start.

Artists' impression of the Orion EFT-1 mission. NASA, public domain.

Artists’ impression of the Orion EFT-1 mission. NASA, public domain. Eventually, Orion may be part of the system that takes us to Mars – and brings us back.

Mars – that’s another planet. It has red skies and blue sunsets, temperatures that make Antarctica look summery, and surface air pressure about 0.6% that of Earth, though that’s academic because it’s mostly carbon dioxide anyway. Mars also has no magnetic field, which means the surface is irradiated from space. Then there’s the dirt, which the Phoenix lander found was saturated with naturally-formed perchlorates. Know what perchlorate is? Rocket fuel. It’s nasty stuff, it’s toxic, and the chances of keeping the habitat clear of it after a few EVA’s seems low.

The biggest problem is that nobody’s been there yet. There’s bound to be a curve ball we don’t know about. It’ll be discovered the hard way.

That was the Apollo experience forty years ago. It turned out lunar dust is abrasive and insidious. As early as Apollo 12, astronauts found dust in the seals when they re-donned their suits for a second EVA – moon-walker Pete Conrad reported that ‘there’s no doubt in my mind that with a couple more EVA’s something could have ground to a halt’. All the later Apollo astronauts hit it; leak rates soared in the suits as dust worked its way into the sealing rings.

I think it’s safe to say something of equal practical difficulty will be discovered about Mars, one way or another. Not good if you’ve just arrived – permanently. Besides, what happens if someone gets needs a hospital now? Or is injured? Well, that’s a no-brainer. You can imagine the colony consisting of a cluster of grounded Dragons with a row of graves next to it.

Cut-away of the modified Apollo/SIVB 'wet lab' configuration for the 1973-74 Venus flyby. NASA, public domain, via Wikipedia.

Cut-away of the modified Apollo/SIVB ‘wet lab’ configuration for the 1973-74 Venus flyby. NASA, public domain, via Wikipedia.

Mars One plan to send more missions every two years, each with four colonists to join the happy bunch. If they’re alive. My money says they won’t be. This is Scott of the Antarctic territory – high-tech for the day (Scott even had motorised tractors) but still gimcrack.

The main reason we’ve not gone there yet, despite space agencies making serious plans since the 1960s, is cost. Manned interplanetary fly-bys were (just) within reach of the hardware built for the Moon landings – and until the Apollo Applications Programme was slashed to just Skylab, NASA was looking at a manned Venus flyby for 1973-74, using Apollo hardware.

Composite panorama of Mars. Not going to be seen by the 2018 expedition, as they'll fly past the night side. NASA, public domain.

Composite panorama of Mars. NASA, public domain.

Unfortunately, stopping at the destination, landing on it, and all the rest was another matter. It was easy to accelerate an Apollo CSM and habitat module into a free-return Venus or Mars trajectory; no further fuel was needed, it’d whip past the target at interplanetary velocities, and the CM could aerobrake to a safe landing on Earth. But stopping at the destination, landing and then returning home? In rocketry – whether chemical or nuclear-thermal (NERVA), the two technologies available until recently, mass-ratios are critical.

Mass ratio is the difference in mass between an empty and fuelled rocket at all times, and fuel takes fuel to accelerate it. It’s a calculation of sharply diminishing returns, and the upshot for NASA and other Mars mission planners in the twentieth century was that a practical manned landing mission was going to (a) require a colossal amount of fuel, and (b) would still transit by low-energy Hohmann orbit requiring a 256 day flight each way, meaning more life support, which meant more fuel (see what I mean?).

Some plans looked to refuel the system from Martian resources, but that had challenges of its own. Either way, the biggest challenge in all Mars mission schemes was the first step, lifting the Mars ship off Earth into a parking orbit. No single rocket could do that in one go, meaning multiple launches and assembly in orbit, raising cost and complexity still further. With figures in tens and hundreds of billions of dollars being bandied about, and no real public enthusiasm for space after Apollo, it’s small wonder governments were daunted.

ROMBUS in Mars orbit: Mars Excursion Module backs away ready for landing. Public domain, NASA.

Conceptual art of Philip Bono’s colossal ROMBUS booster in Mars orbit: Mars Excursion Module backs away ready for landing. Public domain, NASA.

My take – which is far from original to me – is don’t try going to Mars now. Focus on building a space-to-space propulsion system that offers better impulse than chemical or nuclear-thermal motors. Do that and the 256-day trans-Mars cruise – which is what drives the scale and risk of the mission, including problems with radiation doses in deep space – goes away. One promising option is the Variable Specific Impulse Magnetoplasma Rocket (VASIMIR), a high-powered ion drive that might do the trick if it works as envisaged. Another is the FDR (Fusion Driven Rocket). Current projections suggest Earth-Mars transit times as low as 30 days.

Of course, if your drive won’t light when you need it to slow down, you’re on a one-way trip out of the solar system. But hey…

Maybe we should send Justin Bieber on that first VASIMIR mission, just in case…

Copyright © Matthew Wright 2015

Yes – a Kiwi might go to Mars, but I still wish it was Justin Bieber

A New Zealander’s reached the short-list of 100 possible candidates for the one-way Mars One mission proposed for 2025-26 by Dutch entrepreneur Bas Lansdorp, co-founder of the project.

Personally I’d have preferred they despatched Justin Bieber and left it at that. But the presence of a Kiwi isn’t bad given that the original long-list ran to 202,586 individuals.

Conceptual artwork by Pat Rawlings of a Mars mission rendezvous from 1995. NASA, public domain, via Wikipedia.

Conceptual artwork by Pat Rawlings of a Mars mission rendezvous from 1995. NASA, public domain, via Wikipedia.

Still, I can’t quite believe the plan. Settlers will be lobbed to Mars in batches of four, inside modified Space-X Dragon capsules. They’ll land, build a habitat based on inflatable modules and several Dragons, and remain there for the rest of their lives. Kind of like Robinson Crusoe, but with all of it beamed back to us for our – well, I hesitate to use the word under these circumstance. Entertainment.

I doubt that the show will run for many seasons. The development timing for the mission seems optimistic – a point I am not alone in observing. There have been a wide range of practical objections raised by engineers at MIT. But apart from that, nobody’s been to Mars before. Sure, we’ve despatched over 50 robots, 7 of which are still operational. But that doesn’t reduce the challenges involved in keeping humans alive in a hostile environment for their natural lives, and I figure from the Apollo experience that there’ll be curve balls along the way.

Those challenges will begin as soon as the colonists are cruising to Mars, a 256 day journey jammed into a 10-cubic metre metal can along – eventually – with 256 days worth of their wastes. Think about it. Popeye lived in a garbage can. The first Mars colonists? Well, they’re going to live in a commode. Hazards (apart from launch-day waste bags bursting on Day 255) include staying fit in micro-gravity and radiation flux. That last is the killer. The trans-Mars radiation environment was measured by the Curiosity rover, en route, and turned out to be – on that trip anyway – 300 millisieverts, the equivalent of 15 years’ worth of the exposure allowed to nuclear power plant workers. A typical airport X-ray scan, for comparison, delivers 0.25 millisieverts.

I suppose the heightened risk of cancer isn’t really an issue, given their life expectancy on Mars (68 days, according to MIT). Though if the sun flares – well, that’ll be too bad. (‘My goodness, what a lovely blue glow. Nice tan.’)

A large solar flare observed on 8 September 2010 by NASA's Solar Dynamics Observatory. Public Domain, NASA.

A large solar flare observed on 8 September 2010 by NASA’s Solar Dynamics Observatory. Public Domain, NASA.

Unfortunately the radiation problem continues on the surface of Mars. The planet lacks a magnetic field like Earth’s and its atmosphere is thin, meaning radiation is a threat even after you’ve landed. The answer is to bury yourself under Martian dirt, but Space One’s plans don’t seem to include that. There also a possible problem – which we’ll look at next time – with the nature of that dirt.

Whether the intrepid colonists will get away is entirely another matter. Apart from the hilariously optimistic timetable, the project relies on a modified version of Space-X’s Dragon, which has yet to be human-rated. And then there’s funding, which I understand will come from media coverage. But I suspect the likely barrier will be regulatory. These people will be flying inexorably and certainly to their deaths, and odds are on it will be before the natural end of their lives. Will the nation that hosts the launch permit that?

Still, let’s suppose there are no legislative barriers. And let’s say the colonists get to Mars without their hair falling out or the waste bags bursting and filling the cabin with – well, let’s not go there. Let’s say they land safely. Suddenly they’re on Mars. Forever. What now? And what about those curve-balls?

More next week.

Copyright © Matthew Wright 2015

Searching for that elusive exo-Earth

In the nearly 20 years since Michel Mayer and Didier Queloz confirmed the first known exoplanet around 51 Pegasi, the number of known exoplanets has risen to over 1860 – and there are more to come. The Kepler space telescope, before being hobbled by mechanical failure, created a massive database of planet candidates orbiting the 150,000 stars it looked at – some 4,175 in fact – which are still being checked. Eight new planets were confirmed just last week.

We can be sure there are a lot more out there. Kepler scanned just 0.28 percent of the sky in the direction of Draco, out to 3000 light years. In that patch, it could only detect planets whose orbits cross the disk of their star from our viewpoint. Other planetary systems, tilted at different angles, aren’t detectable by the transit method. But they will be there. And now the hot question – how many planets are like Earth?

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

Exo-Earth. A picture I made. Apart from fractal artefacts, does anybody notice what’s wrong?

Astronomers have found a few planets Earth-sized and below – including two of last week’s confirmations. Some are in the ‘Goldilocks’ orbit where the star’s warmth would allow liquid water to flow on a planetary surface. Though bear in mind that an observer using Kepler to scan our solar system would classify Venus as “Earth-sized” in the habitable zone. The problem is that transit-detection gives us diameter and orbital period, hence mass and density of the planet (and of its parent star). But it doesn’t give visual data – we can’t do spectroscopy on the atmosphere, for instance, though that’s possible with other techniques, and some data has been fielded about planetary atmospheres.

However, it’s only a matter of time (and money) before instruments are able to pick up more data from subtle fluctuations of stellar light. A photon here, a photon there – literally. From that, we’ll learn about planetary colour, atmospheric composition (via changes to starlight passing through it). Maybe we’ll learn whether any have large moons, if the orbit of that moon is in line with the star. Though I wonder. We’re looking for another Earth – but who says our world has been replicated?

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

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

One of the types we’ve found is the ‘hot Neptune’ – a world maybe twice the diameter of Earth with eight or more times the mass. About 19.3 percent of exoplanets found so far fall into this category, as opposed to 5.3 percent of Earth-sized worlds. They also orbit relatively closely to their stars. This is largely a function of technical limits – we can detect the bigger worlds more easily, and picking up the orbits of worlds that are distant from their stars requires years-long observations. So these proportions will likely change. But for the moment that’s where the data points.

Close to its primary, such worlds could be water planets, rather than the ice giants we have in our solar system. Maybe these ‘exo-Neptunes’ define ‘normal’. Or maybe every world is unique – product of many variables, obeying the same laws of physics but emerging in variations defined by subtle differences in composition, size, ambient temperature, and so on. Check out Jupiter’s biggest moons – all different, all formed in the same place at the same time.

The realities of physics mean we won’t travel to these exo-worlds any time soon. Or later (and yes, I know about the ‘Alcubierre drive’). But it’s fun to speculate…and I have a question. Suppose we found another Earth and arrived, en masse. Do you think we’d ruin it, the way we’re making a good job of ruining the Earth we’ve got? Just wondering…

Copyright © Matthew Wright 2015

Click to buy from Fishpond.

Buy from Fishpond.

Click to buy from Fishpond

Buy from Fishpond

Click to buy e-book from Amazon

Buy e-book from Amazon