Posts by Alastair McKinstry

Interstellar Bebo spamgasm targeted at 'water world'

More like 2 G

Gl 581d is about 7 Earth masses, but due to the larger radius, the gravity is more like 2g.

This means it would be tiring for us, but not a problem. Water-based creatures have no problems with it.

One important bit about "deep oceans" is "no continents". There is a maximum height for mountains, beyond which the pressure of the weight of the mountain melts the rock underneath. This means mountains would be no more than 20 km or so off the ocean surface, while the ocean could be 100km deep. No continents or islands, no monkeys swinging in the trees.

Regards

Alastair McKinstry

Ready or not, IPv6 is coming

IPv6 is a Value Subtract Service

The trouble is, from a business rather than techie point of view IPv6 is a "Value Subtract Service".

Its mostly ISPs who need to implement it (little point in buying IPv6 endgear without transit), but

IPv6 was designed as "just a small fix" : the same functionality, almost, as IPv4, but you no longer

get a side-market in static IP addresses. You only have to pay extra for dual-stack gear.

So ISPs only move to IPv6 when the pain is sufficient, such as Asians running out of IPv4,

or US cable modem giants for who 10.0.0.0/8 NAT isn't large enough.

The techie problem with NAT, though is the way it breaks so many apps, and routing: You really don't want lots of /32 servers out there.

Sat scope discovers Earthlike 'sauna world'

Don't know what its made of

A "sauna planet" is speculation at the minute. If it has water vapour, its above the critical point of 647K , which is where "gas" and "vapour" are distinguishable. Definitely not where you want to be.

Its denser than Mercury (lots of Iron in the core? ) ; we can't tell at this stage if it has a solid or molten lava surface. Some of that depends on the mass, which isn't well determined yet;

(they published it at their CoRoT symposium which was organised long ago; it was publish now or perish if someone beats them to it).

Virtualization and HPC - Will they ever marry?

virtualization and jitter

One thing that kills HPC with scale is OS jitter. This becomes an huge issue with large core counts: when you run parallel jobs they need to run in sync: if any core lags (running another process, or handling interrupts,etc) , then the other (n-1) cores waste cycles waiting for it. You absolutely can't have a CPU moonlighting as part of another job!

OTOH, virtualization could add nice 'checkpointing' facilities and simplify scheduling on HPC clusters. But virtualizaton would need to be implemented across the cluster as a whole, with negligible overhead (5 - 10% performance loss is what loses you the bid in HPC circles). But its solving a different problem than in enterprise virtualization: adding / removing cores "dynamically" is already a solved problem in HPC, done with schedulers such as PBS and loadleveler.

Greenpeace: UK gov trying to strangle wind power

No silver bullets, but look at conservation

Time to pay attention to both sides of the equation.

All work mentioned so far looks at current consumption and assumes that this is the goal we must aim for, ignoring the fact energy usage per capita is still rising, and that we've built an economy around cheap energy. As energy costs rise,

it becomes more economic to be efficient; and its easier (long-term) to drop usage than create more energy.

In building my own house, I've moved from a 4-bed with ~15 kw oil heating, to 4-bed with ~2 kw electric, only the new house is heated 2-4 hrs/night, 4 months a year, rather than 8-12 hours, 8 months a year.

Including other efficiencies, i've a better standard of living (20 degrees, round the clock, round the year) at 20% the energy usage.

Ditto with transport costs, and many (most?) other industry costs.

I repeat, an 80% drop in energy usage, no standard of living drop.

Not easy, it takes time to rebuild every house to passive house standards, to move out of suburbs and into cities where you can walk/cycle rather than 2-hour commutes, but its not only possible, it will happen.

short-term is going to be painful: the oil price crisis is manufactured. The point of OPEC was to make sure we had an oil-dependent world, and now they're reaping the profits.

But once you look at both sides, renewables work.

Back to the problems with wind: they're not the only renewables. There is also solar, biomass, wave, ... but also, other technologies kick in to help. Smart metering and electricity consumption: eg setting freezer hysteresis temps to turn on the freezer when electricity is cheap (ie wind available), charge batteries, run washing machines, store underfloor heat, etc: thats how to store energy.

Stop looking for one single silver bullet and the problem can be solved.

Nuclear looks fine until you start asking: what about the rest of the world, not just Britain? Uranium is in easy supply because nobody is currently using it.

Fill the world with reactors and U is quickly consumed; at least the top 0.5% or

so good-quality ores. After that, it takes a lot of processing: 30% as much

CO2 per kWh as a gas power station.

The countries who look most positively on nuclear are those who are willing to do what it takes to get it when it runs short; within 20 years. France will get its Uranium from Africa, Canada and will be willing to send the aircraft carriers to get it. Ditto the US and, maybe, the UK? But what about Ireland ? what about Portugal? or Poland?

Schoolboy's asteroid-strike sums are wrong

satellites

Satellite density: Methinks 40,000 is the number of objects that US SpaceWatch tracks. This includes bits of boosters and dead satellites and garbage, not just active spysats, etc.

Big Climate's strange 'science'

This is from a physicist ? bull.

"Somehow we survive".

Nope. we've been around 10,000 -- 1 million years or so. _Life_ survives.

In some of the climate catastrophies you've mentioned 3/4 of all species were

wiped out.

Models have their weaknesses - they always have, and they are well known. But Global warming does not depend on the models, but observations.

We know how greenhouse gases work, you can do it in the lab. We know they're rising, and we see the temperature rising.

We've millions of years of climate data, of differing quality, in lots of proxies: isotopic analysis, gas histories in ice, etc.

Europe hails foothold in space

closed shuttle

@Brett: I believe the space shuttle needs to open its cargo bay doors to radiate heat, as part of its design. (Failing to open the doors was a worry in earlier

missions). Remember, its a nice, insulated container to avoid baking on

re-entry. Just sealing the shuttle is not as easy as it sounds.