Archive for July, 2010

Fermi, With or Without Exclusion

Posted in Astronomy, SETI, Space with tags , , on July 29, 2010 by davidnm2009

I’m not a big commenter, generally, but I felt motivated to leave one on this post on Charlie’s Diary. Basically it concerns the Fermi Paradox.

The Fermi Paradox is a difficult one for me. Obviously I’m interested – the fact I can’t quite shut up about it is the giveaway. But, and here is the problem, as I’ve said before, my considered opinion is that we can’t usefully speculate on it at the moment.

I was trying to wrack my brains again for anything useful that I could say. So, here is what I think we can say:

  • 1: We exist, so we can reasonably conclude that civilisations are at least possible, i.e. there is nothing in the basic physics that effectively rules them out.
  • 2: Our planet doesn’t appear to have been visited at any point in our fossil record. [1]
  • 3: If higher-rated societies on the Kardashev scale exist, then they can’t be anywhere nearby. Although our galaxy has lots of elegant little structural quirks, I don’t think anyone has ever suggested that they’re down to super-civilisation infrastructure projects! [2]
  • 4: Radio signals at interstellar distances – there is absolutely no agreement on this. I’ve seen it argued both way, with no clear sign of a consensus. So I suspect this means we can’t yet conclude anything useful here, either.
  • 5: This is a bit of a cheat as it hasn’t technically happened yet, but the next round of Kepler mission data (due in February 2011) should begin to tell us something about the mass function for terrestrial-type planets. At the moment, all we can really say is that they definitely exist, and some other stars have them.

Not looking very definitive, is it? It’s looking like the paradox might stay paradoxical for some time yet.

_____________
[1] But is there necessarily any reason why aliens would come here? Consider – if the typical life-bearing planet is a tide-locked world around an M-dwarf, why would you send a mission to a G-class star? They’re too hot, too short-lived, emit far, far too much ionising UV and any putative planet would have to orbit so far out that it would actually still have a day-night cycle! I mean, yuck, right?

[2] Although you do have to wonder if the Type III equivalent of Capita was behind the Antenna Galaxies – definitely a PFI bodge if there ever was one!

[3] Yes, the post title is a physics pun. And not a particularly good one, no.

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An Erratum

Posted in Speculation, Writing with tags , , on July 29, 2010 by davidnm2009

A couple of days ago, in The Misfits, I quoted an energy of ~ 8 * 10^26 J for the plotline-demanded impact event.

Following on from a comment on this post, I’ve had occasion to re-check my figures. And I’ve discovered that they’re a bit off. I suspect I may have dropped a decimal place somewhere in the earlier analysis. Given that I was doing it at 11.30 at night, however, I’m hardly shocked! (I’ve edited the document to reflect the changes. Part of it, I think, was the classic school-boy error of forgetting that radius = 1/2 of the diameter. And of course volume goes by the cube of radius, so when I fed in the diameter where I meant the radius, that instantly inflated all the numbers by a factor of 2x2x2=8, and that’s *before* you get to decimal-place errors …)

The actual figure should be 4.3 * 10 ^ 25 Joules, so the impact will release about 6% as much energy as the two suns do per second, not 250%. However, this is still not good news. To put this in perspective, imagine a sphere of granite about 380 Km across (or about as big as some of the moons of Saturn). If the entire sphere was at a temperature of 20 C, an impact this energetic would be able to melt all of it. (Or heat it through 680 degrees C, which would take it to an even 700, which is about what Wikipedia claims for the temperature of lava…)

So to rephrase, this hypothetical impact can melt something the size of a Mimas.

It’s still not good news. And as such I still maintain that Minoris will lose its crust, although it may hang on to more atmosphere then I’d initially suggested. However it is safe to assume that once the thirty hours are up, it won’t be humanly-inhabitable anymore.

Orks Attack!

Posted in Art with tags on July 29, 2010 by davidnm2009

I was fiddling around with Poser again last night, and this was the result:

A higher-res version (with full model credits) is on my dA page, here.

The Danger Of False Alarms

Posted in Personal, Social Concern with tags , on July 26, 2010 by davidnm2009

Sensible health and safety policy isn’t always easy to do. Here is an instructive example:

  • Williams said he discovered that the physical alarm system had been disabled a full year before the disaster. When he asked why, he said he was told that the view from even the most senior Transocean official on the rig had been that “they did not want people woken up at three o’clock in the morning due to false alarms”.

Oddly enough, on this one thing at least, I do have some sympathy for the Deepwater Horizon people.

The naive approach to health and safety holds that there is no such thing as a false alarm, and that people should be willing to tolerate any degree of minor inconvenience for ‘safety’. Unfortunately, this is horrifically counter-productive in practise, and can in effect actually endanger life rather than protect it. Let me give an example…

At the university where I work, we have a fire alarm system. It operates on a ‘zone’ system – the building is divided into a number of zones. When a fire breaks out in one of them, an automated alarm will go off to evacuate that area. The zones next to it get ‘alerts’ – not actual alarms, but a blaring speaker in each room that announces in a deafening, stentorian voice that ‘THERE IS A FIRE ALERT IN A NEIGHBOURING ZONE – STAND BY FOR FURTHER INSTRUCTIONS!’ It does that at something close to 90 dB, and can carry on doing this for up to half an hour. (The only people who can turn this off are Security, and that involves rousing them from their daily tea-break, which starts at about 9 AM and finishes some time around 5 PM.)

Problem is, fires aren’t the only thing that set it off. Hot weather sets it off. Heavy rain on the asphalt roofing can set it off. The frequent burning smell from Engineering can set it off. For all I know, the phases of the Moon might set it off too. And this is a big problem. It disrupts work. It annoys people. It shortens tempers. And also, very, very dangerously, it habituates people to the idea that when an alarm sounds, it’s false.

This is bad.

It means that, one day, the alarm will go off for real – and no-one will react. Everyone will assume that it’s just another stupid false alarm. And they’ll only realise it isn’t when the flames start licking at the office window.

Basically, something some health-and-safety types really need to realise is that conditioning people to assume that alarms are false is not clever.

The Slow Problem

Posted in Space, Speculation with tags , , on July 22, 2010 by davidnm2009

Ladies and gentlemen, we have a small problem.

I say a ‘small’ problem – actually it’s arguably quite a large one. It’s called stellar evolution [1]. You see, from the moment the original protostar ignited, our Sun has – in a sense – been dying. Now, before everyone looks too shocked, this isn’t actually news. Also, it’s not dying particularly fast. It’s been going for ~5 billion years, and it should run for another ~5 billion years. However…

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Occupational Hazards

Posted in Amusing, Astronomy with tags , , on July 20, 2010 by davidnm2009

Astronomy has some very odd occupational hazards.

  • At the Mauna Kea observatories, you’re banned from going to sleep(!). The problem is that, at high altitude and an air pressure of ~ 600mb, some sleepers don’t wake up again.
  • There’s a radio telescope facility in India. A colleague of mine who did some observing there was warned not to go outside at night, due to the risk of being attacked by panthers(!).
  • The Roq de Los Muchachos Observatory is the most scenically-beautiful that I’ve yet been to. It’s also the most convenient, being (in principle) about 4 hours’ flight from Europe. (It’s longer from the UK because there aren’t any direct routes – you change at either Madrid, several places in Germany or in Tenerife.) But, it also has just a bit of a body count. The week before I was there in 2008, someone fell to their death off of the back of one of the MAGIC telescopes. Also, people keep driving straight off the roads – and the roads zig-zag up a very steep hillside. Going off that will hurt.
  • Although I’ve never been there myself, apparently the safety advice at the VLT in Chile is something to the effect of ‘Don’t go outside at night, because if you fall over and break something you’re in the middle of nowhere and there’s no way to get help to you’.
  • I imagine that if you visit the South Pole Telescope, there might be just a small problem with hypothermia. (Oh, and maybe rabid zombie penguins too…)

Basically, observing is less sedate than you might think.

Also (perhaps sadly) we don’t actually look through the telescopes any more. In fact, I’m not aware of any research-class instruments that have an eyepiece attached. (You can usually see the output on a screen in the control room, though.) Saying that, I think there is an old finder-scope bolted onto the side of the INT, but I’m not sure if anyone’s used it in a long time.

An 8-metre with an eye-lens would be cool … until it accidentally points at anything bright, that is, and the unlucky viewer gets blinded, of course.

Best PR Fail Ever?

Posted in Amusing, Writing with tags , on July 19, 2010 by davidnm2009

I was just reading this very old thread from Making Light on the subject of the dreaded Rejection Letter (which is just the occupational hazard of would-be published authors, when you get down to it). The thread is equal parts hilarious, depressing and informative, and thus well worth a read.

However, this comment in particular caught my eye.

Ummm … meat products in the post? Meep?

I can understand that PR people do need to be ‘innovative’, for all that sounds like the worst sort of pseudo-managerial BS. But there is a fine line between ‘innovation’ and ‘dementia’. I think plans that involve mailing meat to people really are tipping toward the dementia side!