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

My flirtation with the ultimate golden age sci-fi gadget

I re-discovered my slide rule a while back, the one I used in school maths lessons, way back when. I didn’t know just how utterly classic such things were, even then.

Aha - now I can stop the Plorg Monsters from taking Earth's water!

Aha – now I can stop the Plorg Monsters from taking Earth’s water! Maybe with an app on my Surface Pro 3, but surely via my old slide rule!

These things mostly worked because of a quirk of mathematics – the logarithm, which means you can add logs, as a linear measure, to multiply. And there’s more. In the photo, I’ve set my slip-stick to do the pi times table – and believe me, it’ll calculate that to about two decimal places (which is OK for a quick estimate) faster than you can punch the same thing into a calculator. All you have to do is slide the centre piece to the right point and look along the ruler. Cool.

Time was when no self-respecting space adventurer set off without one of these. They were a staple in Robert Heinlein’s sci-fi, among others. With them you could not only defeat the squidgy aliens who were trying to make off with all Earth’s water – you could go on to conquer the entire universe.

And, just to nail how fast the world changes, NASA actually did conquer the Moon with slide rules. Apollo-era engineers carried them the same way we carry phones.

My slide rule’s linear, but they were also available as circular calculators – disks – often optimised for other functions such as electrical calculation. My father had one.

I have to admit that I’m using computers to do the maths for a hard sci-fi story I’m writing just now for an upcoming anthology. But still, the slide rule’s there as a standby. And the idea of it – well, I find that pretty inspiring. Do you?

Copyright © Matthew Wright 2015

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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

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Orion’s first flight is good news – but can NASA sell the space dream?

I checked the latest space news on Saturday with bated breath. NASA had a lot riding on this week’s Orion flight. In a climate of limited budgets and little real public enthusiasm, failure wasn’t an option.

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

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

The problem is where Orion goes next. By Cold War standards ambitions are vague; a couple more test flights, fly around the Moon or go to a captured asteroid by 2021-25, and then on to Mars some stage in the 2030s….eventually. Maybe. Both these aims and the time-frame stand at odds with Apollo-era determination when goals, budgets, public support and intent all meshed. I wouldn’t be surprised if Orion flounders before it gets much further, purely because of that mushiness vs public apathy vs budgetary realities.

Which is a pity, because it’s a good spacecraft and the flight on Saturday demonstrated – after two tragic ‘private enterprise’ failures – that the Apollo-era NASA ‘business model’, which rested on private contractors and commercial suppliers – still works. Rocket science is just that – it’s risky, difficult, and stretches materials science. Cutting corners, private-enterprise style, may save money. But when it comes to spaceflight there’s no room for error.

EFT-1 Orion being prepared to flight atop a Delta 4 Heavy. NASA, public domain.

EFT-1 Orion being prepared to flight atop a Delta 4 Heavy. NASA, public domain.

The other point is that Orion is not – as some critics suggest – a retrograde step. Sure, Orion looks like a 1960s capsule. But it isn’t – it’s stuffed with twenty-first century tech. Don’t be fooled by its 2002-era PowerPC 750FX-based computers, either; space computer hardware has to be well proven and rugged. If it fails at the wrong moment, you die. Armstrong and Aldrin’s Raytheon AGC fly-by-wire computer partly crashed when they were descending to the Moon in 1969. But not totally – and it was safe to land.

What’s driving the illusion of Orion being ‘retrograde’, I think, is that we’re conditioned to imagine space ‘progress’ as ‘advance’ from one-shot cone-shaped ‘capsules’, to multi-use winged spaceplanes designed to fly, literally, into space. They were the future, way back when. Except they weren’t. The problem is that the laws of physics don’t co-operate. Mass is everything in spaceflight – dry mass to fuel mass ratio, in particular. The Shuttle orbiter had to lug a LOT of mass into orbit that was useless up there – wings, tail, landing gear, hydraulics, heat shield and so forth. Dead loss for your fuel budget. And that’s apart from the risks of strapping the spaceplane to the side of its booster.

Orion recovered off California after the flight, 4 December 2014. NASA, public domain.

Orion recovered off California after the flight, 4 December 2014. NASA, public domain.

For anything beyond low-earth orbit, you need a vehicle that lacks the encumbrance of aircraft-style flight hardware – but which can still make an aero-braked descent to Earth, because it’s not practical to carry the fuel you need to slow down by rocket. Ideally the spacecraft also has to generate a certain amount of aerodynamic lift, both to steer the descent and to reduce deceleration forces on the crew. The resulting shape is specific, and Apollo, Orion, the Boeing CST-100 and Chelomei’s 1970s-Soviet era VA re-entry capsule all use virtually the same truncated cone design. McDonnell Douglas’ Gemini, Space X’s Dragon, the Soyuz and Shenzhou offer only minor variations on the theme.

Apollo vs Orion. NASA, public domain.

Apollo vs Orion. NASA, public domain.

Orion, in short, is a recognition of the physics of rocket-propelled spaceflight. Budgets permitting, the 2020s should bring a flurry of similar spacecraft into low-earth orbit – Space X’s Dragon and Boeing’s CST-100, servicing the space station. The Russians (hopefully) will be in on the mix with their late-generation Soyuz. And there’s the Chinese manned programme.

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 for the 1973-74 Venus flyby. NASA, public domain.

Beyond that, Orion will be on hand to fly to the Moon, a nearby asteroid, and eventually Mars. Orion will not, of course, fly by itself on long-duration missions. It’s good for 21 days in space – enough for an Apollo-type jaunt around the Moon – but for longer flights it’ll be docked to a habitat module. This mirrors the 1968 plan to send astronauts on a Venus flyby using Apollo hardware – the crew would have spent most of the 396 day flight inside a modified S-IVB stage, using the CSM only for the launch and re-entry phases.

Orion with propulsion and habitat module for an asteroid mission. NASA, public domain.

Artist’s impression of Orion with propulsion and small habitat module for an asteroid mission. NASA, public domain.

Orion, similarly, will be docked with various habitats and propulsion stages depending on mission. The whole stack will become the ‘interplanetary spacecraft’. But all this assumes budget and enthusiasm, among other things (‘other things’ includes finding ways of dealing with radiation, of which more some other time). Bottom line is that state-run space efforts can be killed with the stroke of a political pen.

Perhaps the biggest challenge, then, will be re-selling the excitement of the space dream to a wider public, both in the US and beyond. And this, I think, is where the focus needs to be for the foreseeable future. Space flight is, after all, one of the greatest ventures in the history of the world.

Copyright © Matthew Wright 2014

The really annoying thing about time travel stories

I’ve always wanted to invent a time machine so I could whip back in time to stop Hitler before he did anything evil. Of course there are a couple of problems. First is I’d be joining the back of a LOOONG queue. The other is that our friend Albert Einstein tells us it’s impossible.

But even if a time machine could be built, nobody’s really figured out what it entails. Here’s the deal.

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

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

Science fiction is rife with stories about time travel, variously either as social commentary, H. G. Wells style, or as cautionary tales – witness Ray Bradbury’s wonderful A Sound of Thunder. Invent a time machine, go back in time and change the past – and you’d better watch out.

Of course, if things change so you don’t exist, then you can’t have invented the time machine. Which means you didn’t go back in time. Therefore you do exist, so you did invent the time machine and… Yah.

Or there’s Harry Harrison’s hilarious Technicolour Time Machine, about a movie maker who uses a time machine to cut production costs on his period drama by going back to the actual period. What I’m getting at is that there’s a gaping great hole in all of this. And it’s an obvious one.

Suppose you COULD time travel. Suppose you’d built a machine to do it. You decide to whip back twelve hours. And promptly choke to death in the vacuum of deep space.

Nikolai Tesla with some of his gear in action. Public domain, from http://www.sciencebuzz.org/ blog/monument-nearly-forgotten-genius-sought

OK, so it’s not a time machine, but this is what one SHOULD look like. Nikolai Tesla, being spectacular with AC electricity (he’s reading a book, centre left). Public domain, from http://www.sciencebuzz.org/ blog/monument-nearly-forgotten-genius-sought

What gives? The problem is that everything in space is moving. Earth is rotating. Earth also moves around the Sun, which itself is orbiting the galaxy, which itself is moving as part of the Local Group, and so forth. We don’t notice or even think about it because we’re moving with the Earth. If we take Earth as our reference point, it’s fixed relative to us. And that leads us to imagine that  time machines are NOT moving through space – Wells, in particular, was quite explicit that his time machine was fixed and time moved around it.

But actually, a time machine that did this – that stayed ‘still’ relative to Earth would have to move through space, because Earth is moving.

Let’s reverse that for a moment. What say your time machine doesn’t move in space at all. You move back and forth through time, but your absolute spatial position is fixed. Not relative to Earth, but relative to the universe.

You leave your lab and leap back 12 hours. Earth won’t be there – it won’t have arrived. Leap forward 12 hours – same thing, only Earth’s moved away. If you’ve only moved a few seconds, you might find yourself plunging from a great height (aaaargh!). Or buried deep in the Earth (choke).

So for a compelling time-machine story you need to have a machine that not only travels anywhere in time, but also anywhere in space. And, of course, any relative dimensions associated with both. That’s right. A machine that travels anywhere through time and relative dimensions in space.

Heeeeeey, wait a minute

Copyright © Matthew Wright 2014

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