* Posts by R W Rodway

8 posts • joined 7 May 2008

Linux clockpocalypse in 2038 is looming and there's no 'serious plan'

R W Rodway

Re: Not just Linux

Actually that's a slightly different date overflow problem. Dates in DVB are represented as a 16 bit modified Julian Date and a 6 digit BCD encoded time within the day.

A modified Julian Date is the last 5 digits of the full Julian date. The current full Julian date is 2457074

so the modified Julian date is 57074. 16 bits mean that 65535 is the last modified Julian date that can be represented in the DVB format, which is 22nd April 2038

Almost the same date and definitely a problem, but a very different derivation


Boffins lay bare exotic Lara Croft meteorite element ununpentium

R W Rodway

Soon we shall be able to synthesis Naquadah. And then we can make stargates!

Reg man goes time travelling at iconic observatory

R W Rodway

Re: Is there a physicist in the house?

Light (or radio) gathering ability I think. With an actual square KM of dish you can gather a lot of RF energy, which lets you see fainter things. What the long baseline does is let you resolve smaller things, but if you want to see fainter things, you need the disk area.

At least thats what this amateur physicist thinks, I'm quite ready to be corrected by a real physiscist :)

Twenty classic arcade games

R W Rodway

Re: Has to be ... Star Wars!

Yup, got to concur with Star Wars. I spent FAR too much time playing that at Uni. Including one 11 hour game (got to 95 million+, 350 odd death stars (the counter stuck at 99, but after 256 it went back to 0), and then the arcade closed and they threw me out! Still don't know if the score can handle 100M :))

Commentards Ahoy! How about a Petabyte of storage?

R W Rodway

Hmm,. I have my doubts about that 1.5KN/m^2 thing....

80 kg person (0.8kN), assume foot area of 30cmx15cmx2 (2 feet), gives 0.09m^2 and a total force (just standing still) of 8.888kN/m^2. Should I be worried about falling through the floor? Standing on one foot would be right out!

Assuming that averaging over the room is OK, then you have no problem with your 400kg unit, even with 5 people also in the room, as long as the total size of the room is 5.4m^2 or more. Or a room 2.3m on a side, which is not exactly large...


Apple's Tim Cook gets one million reasons to stay on as CEO

R W Rodway

United States of Apple?

Hmm, well, using that 4029% rate, that makes the market cap of Apple in 2021 about 14.682 Trillion

Now US GDP in 2010 was 14.5265T, lets assume a 3% growth rate, so that makes US GDP in 2021 20.1081T

So Apples market cap will be 73.02% of GDP. Somewhere around there maybe they'll change the US flag to the Apple logo? :)

Is the earth getting warmer, or cooler?

R W Rodway
Thumb Up

Frying tonight

Well, I don't think we should get worried about the slow increase in solar luminosity killing us any time soon. The variance in total solar irradiance seems to be about 1 W/m^2 from the minimum to the maximum of the cycle, varying around a base of 1366W/m^2. So that's 0.073% variance. The time taken for the sun to warm such that the minimum TSI is equal to todays maximum TSI would then the 0.073/6 billion years, or about 12.2 million years. Plenty of time to get the beers in before we all cook.

Incidentally, though I do think that AGW is a problem I think energy security (aka keeping the lights on) over the next few years/decades is a far bigger concern.

R W Rodway

@Inconvenient Truth

Well of course it cooled down. Adding more Co2 to the atmosphere doesnt cause the temperature to keep getting hotter and hotter ad-infinitum, it causes it to get hotter until the increased radiation from the Earth (due to it's now hotter temperature) balances the incoming solar radiation. What Co2 does is to cause a given rate of radiation from the Earth to corellate to a higher surface temperature. It's the same as putting a blanket on the bed at night. If the current temperature of the earth is hotter than that equilibrium point then it will cool, as was the case with that molten ball of rock at the start of the Earths history. Even with all those greenhouse gasses in the atmosphere the equilibrium temperature was way below the current temperature, so the earth cooled until it reached that temperature. This is also complicated by the suns luminosity then, which as best we understand was quite a lot less than it is now (the current theory iirc has it that the sun increases in luminosity gradually (about 6% per billion years) until eventually the hydrogen is depleted and it becomes a red giant) This means that for a given greenhouse gas concentration the equilibrium temperature will be lower (blanket example, if the temperature in the room goes down, even though you have a blanket on, you will cool down, Adding a second blanket though will help)

I gather that the current best estimate for the Co2 sensitivity is about 3 degrees per doubling of Co2 concentration. So if the average temp now is 14C and we double the concentration of Co2 then the average temp will slowly rise until it gets to 17C (and then stop if we don't add any more Co2).

However if instead aliens come along and microwave the earth, raising its temp to 50C, incidentally doubling Co2 concentrations in the process then the Earth will COOL gradually until it reaches 17C. But it won't go back to 14C again unless the extra Co2 is removed (or something else counters its effect, like the sun reducing in luminosity a bit)

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