Flares Are Back!

Apparently I do requests now, as someone who shall remain nameless wanted me to post about this.


On Thusday night, I saw my first-ever Iridium flare! If you're too lazy to click on the link to Wikipedia (or they're SOPA'ed out again), I will explain it myself with lies and half-truths and everything.

Some years back, a bunch of rich idiots including but not limited to Bill Gates and Motorola decided that America knew what the world wanted in a mobile phone, namely a handset the size of a breezeblock that cost $3,000 minimum and a contract that would charge $10 a minute of calltime. 

The thing is that America is a big country that is sparsely populated for most of its territory. The cost of fitting conventional GSM towers all over the nation to give European-style levels of coverage would cost billions. BILLIONS! 

The solution? Well, how about bigger cells? Trouble is, for the shortwave frequencies that go furthest without needing huge antennas and frying the users head, the earth's curvature becomes a problem as the radio broadcasts only go out to the horizon. 

So, how do you see further over the horizon? From higher up. 

Instead of a network of hundreds of thousands of cell towers, they envisaged a network of seventy-seven satellites in low-ish Earth orbit, providing phone coverage not merely across the US, but ANYWHERE ON EARRRRTHHHH (and also in any nearby space stations). 

The seventy-seventh element in the periodic table is Iridium, so that's where they got the name. 

A couple of problems occurred. One was that Satellites are REALLY expensive, as are the rockets to launch them. The other was that GSM networks spread like crazy, even in poor countries that'd never had a fixed-line telephone network, as the cost of GSM kit was hugely less than millions of miles of copper cable. As more people bought GSM network gear, the cost went down and down and down. 

In the meantime, the cost of the satellites went up and up and up. Eventually, they had to settle on only sixty-six, but didn't rename the network to element 66, possibly because Dysprosium sucks as a name. 

Eventually, they launched their network and sold services to basically no-one outside of international news services and ultra-rich yachtsmen. They ran into financial difficulties and would have died a death if it hadn't been for a little old thing called war. 

The wars in Afghanistan and Iraq revealed that a lot of the fancy communications gear the US Armed forces had spent billions of moneys on was in a lot of ways pretty crap. All around them, embedded journalists were running round with phones that were more reliable, more rugged and more effective than the Army's own kit. The Pentagon immediately started throwing money at Iridium and everyone was happy except for the people who got bombed and shelled and stuff thanks to a phone call but they were all non-American and thus didn't count. 

Aaaaanyway, the interesting thing about Iridium is the satellites. Ignoring the one that crashed into a Russian Strela-2M communications satellite, the surviving Iridium satellites have one very interesting design feature, a pair of large, flat, mirror-finish radio antennas. 

Around dawn and dusk, passing Iridium satellites will reflect the sun's rays down to earth, appearing for a few seconds as a *really* bright moving star (up to thirty times brighter than Venus!). Some flares are visible in broad daylight! 

The great thing is they're predictable. I have an app on my Android smartphone that takes my GPS position and works out where and when I'll see a flare (actually it cheats and asks a web server to do the hard sums). Tonight, I went out at the appointed time (18:34), looked where the pointy thing said and waited. 

Out of nowhere, a star appeared. It got brighter until it looked like the main light of a plane without the wingtip lights or blinking anticollision lights; it moved steadily north-east and then faded down to invisibility again. 

I'd seen a half-tonne satellite seven hundred miles up while it was somewhere over the North Sea, a little south of Norway! 

And that was my evening.


For you kids too cool for smartphones, you can always try www.heavens-above.com as that'll do the same job as the app.

When Worlds Collide

In the good old days before physics and maths got all post-modern on us, the solar system ran like clockwork and the trains were always on time. Planets knew their place and wouldn't dream of spinning out of orbit and smacking each other in a Michael Bay-style extravaganza of explosions and mayhem. Unfortunately, standards have since slipped.

Actually, the idea that the planets were stuck in their tracks like some sort of cosmic Scalextric set was in trouble as far back as Newton, who could do the maths to prove the stability of a single planet orbiting the sun but wasn't able to produce a general solution to the problem of the Moon's orbit. Newton believed a general solution for all the planets was impossible and that the long-term stability of the solar system was thanks to God fiddling with the celestial clockwork every so often.

Thanks to computers, we can now run simulations of the solar system for billions of years into the future before tiny unknown forces like the mass lost by the sun due to the solar wind, or the effects of galactic tidal forces make a joke of the numbers. The possible planet-smashing predictions reported by the press are the result of 2500 simulations run by Jaques Laskar and Mickaël Gastineau of the Paris Observatory who in each run simulated the next five billion years of the solar system's future, up until the point where the Sun grows into a red giant and vaporises most of the inner solar system.

The interesting thing to me is what the difference was between each run: They changed the initial position of Mercury by a single metre.

In 20 of their cases, Mercury's orbit eventually went nuts; sometimes falling into the sun, sometimes smacking into Venus. Regardless of how Mercury flew off the rails, the peturbations it caused on other planets was enough to cause some serious orbital shennanigans, including a possible Mars-Earth smackdown of the Hollywood kind.

So, given time, the tiniest planet (Sorry, Clyde) can throw the solar system into disarray. Makes me think of the old joke about the Earth falling into the Sun if everyone in China jumped at the same time. Well, it might not happen right away...

One for Mythbusters, perhaps.

Oooh! I'm quite fat! what if I jump up and down for a really long time? What would happen first; the Earth falls into the Sun, the Sun eats the Earth or I get in shape?