Which really does need to be remembered by the greens.
It only takes a single badly understood volcanic event (eruption or otherwise) to not only negate, but reverse any measures we take over the next few years.
That's not a reason not to do anything. But it does suggest we need some perspective.
Say that again? Why should the latitude mean that one route is significantly closer than the other way, for two locations that are as near as damn 180 degrees apart in longitude? Surely it will affect both routes equally. Am I about to learn something?
Bleeding obvious, I'd have thought. In fact I'd have thought that the Russkis will have placed remotely detonatable charges at distant spots on most cables, the Chunnel, interconnectors for volts, and all sorts of pipelines.
I'd have thought differences in intervening weather systems (e.g. prevailing winds, pressure) rather than rotation; but I don't know for sure.
#Paul
ELF radio. The antennas for the UK Navy were at Rugby. Now at Anthorn and Skelton.
You need to look at great circle distances, rather than longitude. In round figures, the great circle distance between Tonga and the UK is
16,000 km. The circumference of the earth is 40,000km, so going the other way is 50% longer, at 24,000 km.
Indeed, but how much useful info could be transmitted in a couple of minutes is difficult to say
And from
I'm going to have to try this with bits of string on a globe. I think my suggestion would only have been true if the UK and Tonga had been diametrically opposite (ie a straight line joining them goes through the centre of the earth). I'd naively thought that *any* two points on the globe that were 180 degrees apart in longitude would have both routes the same as each other, even if their latitudes were different. I can sort of see why I'm wrong if the straight line misses the centre of the earth. Told you I was about to learn something ;-)
So the difference in distance (coupled with other variables like variations in weather systems affecting the speed of the pressure wave) explains the two pulses I saw. And the two times were 15 hours for the first pulse and 22 hours for the second, which is a ratio of 1:1.47, which ties in nicely with your "50% longer", and suggesting that there was not actually much difference in speed.
Use the underwater telephone systems to talk to a surface ship where the surface ship does the relaying by HF or satellite. The UK navy system details are classified but the range is sufficient to be "useful" .
I was only using rounded figures, as I don't know the circumference of the earth on that great circle. It is, of course, an oblate sphere, not a true sphere, so the circumference differs, depending where you measure it. It might well be 47% longer, rather than the rounded 50% I gave.
Well I was listening yesterday to China Radio International, and they said that although there had been some damage to a couple of their subs (did not say why they might have been there in the first place) it was mainly the waves, and ash and apparently something called Pyroclastic waves that caused most casualties and deaths around the area as far away as South America and Fiji, China, Australia and New Zealand should be able to land on the island today, when several feet of ash is cleared from their runway. Its apparently not safe for surface ships getting too close in case things take a turn for the worse. As for Wildlife, nobody has said. I know there was an oil spillage at a terminal in South America from a tanker unloading when the wave arrived and snapped off the pipes. Brian
Yes and there are cyclones around now it seems. Yes Fiji had problems but most of the problems are on the smaller outlying islands in the direction of Tonga. Brian
As the cables are now fibre optic, I assume they are somehow picking up info from the repeaters, which are about 100km apart. Quite how they'd do that is no doubt why it's classified!
There's some interesting reading at
Hmm. That news story about their subs seems to have been pulled. I couldn't find a mention of it searching just now on China Radio International or other pages with a .cn domain.
Well its bollox
There are an infinite number of paths from one side of the globe to the other.
Stop thinking about where its latitude or longitude, think of the poles. each line of longitude is a great circle route between the two.
This is the case where the longest and shortest paths are equal.
Obviously the closer two points are the greater the spread between the minimum and maximum path lengths, but there are always an infinite number of paths...
Ther is no reason to assume that the pulse has to ether go via the shortest route, or the longest
True, there are an infinite number of paths but the shortest two will be on the great circle that goes through the two points. The shortest *may* be the one that is strongest because attenuation will depend on distance. So what you'd expect to see is a strong pulse for the great circle route either way round (so two pulses) with a "smear" of smaller pulses for various delays afterwards, corresponding to the infinite number of longer (non-great-circle) routes. Would you even see the pulses that have gone by all the other indirect routes?
And my graph
Not the shortest two. The shortest one. If I walk across my garden, I can take the shortest route. The next shortest will also be entirely within my garden - it won't be the 39,999.99 km route going the *other* way around the great circle.
I agree. I'm wondering whether all the pulses that travel by *slightly* longer routes than the direct one will be received, because their wavefronts will not be perpendicular to the straight line joining the points (where "straight" is a great circle). And by extension of that, the "round the back" route that is the opposite way round the great circle may be received because its wavefronts are perpendicular to the line of travel.
Going back to the string-and-globe. I managed to find my battered little globe, and eventually managed to find a bit of string and a ruler. For the record, I measured 16 cm by the direct great circle route and 22.5 cm by the indirect great circle route. That's a ratio of 1:1.4 which roughly agrees with the earlier estimate of the indirect route being 50% greater.
And the earth is very *nearly* a circle: the equatorial circumference is
24,901.461 miles whereas the polar circumference is 24,859.734 miles
No.
The *longest* and the shortest.
Shortest, but there is no reason to assume straight lines, so there is no longest.
Wouldn't it be like a wave diffraction pattern, where different paths generally cancel except at very specific places. Or like the quantum diffraction idea and I think Feynman integral, where you integrate over every possible path.
Anyway, two specific blips might be due to distinct layers in the atmosphere and separate propagation speeds. Or maybe even due to some effect through the earth or water.
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