Our civilization is almost ready to colonize the next star system (4 light years away) at around 8000 years old
That seems like a very optimistic observation to me. We currently have limited capability to send a few people to a Low Earth Orbit, just outside our atmosphere. In the last 50 years, we've not made any significant progress.
The delta-V required for interstellar traffic in a reasonable time cannot be met with chemical rockets, fission, or even fusion drives. The amount of fuel would simply be too large to be practical. Don't forget you need to brake as well.
In addition to the delta-V challenge, there's also the problem of the proper course. How would we know from earth which planet in our neighbourhood could support human life ?
You're right about metals, but energy is a big problem for future civiliations on earth. We've already used up all easily accessible oil. There's still plenty of oil left right now, but nothing is easily extractable (or easy to find) for civilisations who don't have our current knowledge and technology.
Without oil, it's not easy to jump start a new civilisation into space.
He says NASA satellite data shows the average temperature in June was 0.43 degrees higher than normal. NOAA says it was 1.22 degrees higher.
That's because they measure completely different things. Satellites measure the lower troposphere, while NOAA uses ground based meteorological stations.
Especially in short time frames, the difference can be quite big. Over longer times, the average trend is similar, although some discrepancies have been observed too. See this page for a discussion: http://en.wikipedia.org/wiki/Satellite_temperature_measurements
He says too many of the weather stations NOAA uses are in warmer urban areas.
Funny how the NOAA anomaly map for 2010 shows hardly any warming in urban areas, and plenty of warming in thinly populated areas (Africa, Canada, and major oceans)
Going from 280 to 380 ppm is a relative increase of 35%. That's certainly a significant increase. Don't get distracted by the relatively small overall concentration in the atmosphere. This is completely irrelevant. What matters is the total mass of CO2 the light passes through from the sun to the earth's surface. This total mass has been increased by 35%.
Actually, the Antarctic ice cap is losing volume, even though it is gaining surface area. The Arctic ice cap is losing both volume and area. Greenland ice is also losing volume.
Europe may have had a cold winter, but globally the period Dec 2009-Feb 2010 was warmer than average. Similarly, the spring/early summer period was also warmer than average.
As far as the temperature on any given point on the globe, it's a combination of weather and climate. Global warming has pushed the averages up a little, but daily weather will always be the major factor in the temperature swings.
The Antarctic ice sheet isn't really melting, but the glaciers are moving at an increased speed, carrying more ice towards the edges (where it is melting).
The current model of coherent memory/identical time/everything can route to everywhere just can't scale to machines of this size
Why not ? Obviously, you can't have a million processors accessing the same variable in memory, but with a layered system of caches, you could keep most processors working in their own local copy. As soon as a processor writes to memory that's also used by another process, extra hardware will keep the memory coherent. This architecture is basically a superset of a message passing architecture (memory coherency signals are equivalent to messages), but much simpler for the CPU. Because the CPU isn't aware of the messages, this allows the coherency hardware to be improved without changing the program in any way.
You don't need to land the whole mass on the moon. Instead, you can land an almost empty fuel container, fill it up, launch that from the moon, and fill up your main craft in LEO.
I haven't had a wristwatch for many years, and I rarely miss it. Whenever I need to know the time, there's usually a clock nearby. After I got a cellphone, I've been using that to tell the time if there's no clock in sight, which is usually not more than once a day. If I forget to charge the phone, I'll survive without it.
Only the oxides are harmful. When nitrogen is bound in other compounds, it works as a fertilizer. Plants need nitrogen, but they generally can't get it from the air, but they will readily absorb it from the soil.
You could just write down "sqrt(sin(53.128457638) + e^(3.563462378 * pi)) " on the answer sheet. The conversion to a single number is trivial with a calculator, so there is no need to include that in the exam.
Once you get infected with a trojan (which happens to a lot of people), it is trivial to put some fake public keys on your machine, or to insert a fake e-mail straight into your inbox.
My bank uses a better solution: they send me regular mail. They don't even have my e-mail address, so I can ignore any mail that claims to be from them.
No, the Linux kernel is bloated because of all the features it has. Put the same features in Minix, and it would be at least the same size, and probably bigger.
Efficiency rate should be better than first converting it to liquid fuel and burning it a car. It's the same chemical energy stored in the atomic bonds, but it's all directly converted to heat. A big power plant has higher efficiency rate than a small internal combustion engine.
Emissions may be a concern, especially if the waste doesn't burn completely. To improve that, you could add some natural gas, or other fuel to increase temperature. The extra energy can also be converted to electricity. Other emissions, such as chlorine from PVC must be neutralized, but this is a known problem in waste incineration.
Slashdot Mirror
Our civilization is almost ready to colonize the next star system (4 light years away) at around 8000 years old
That seems like a very optimistic observation to me. We currently have limited capability to send a few people to a Low Earth Orbit, just outside our atmosphere. In the last 50 years, we've not made any significant progress.
The delta-V required for interstellar traffic in a reasonable time cannot be met with chemical rockets, fission, or even fusion drives. The amount of fuel would simply be too large to be practical. Don't forget you need to brake as well.
In addition to the delta-V challenge, there's also the problem of the proper course. How would we know from earth which planet in our neighbourhood could support human life ?
You're right about metals, but energy is a big problem for future civiliations on earth. We've already used up all easily accessible oil. There's still plenty of oil left right now, but nothing is easily extractable (or easy to find) for civilisations who don't have our current knowledge and technology.
Without oil, it's not easy to jump start a new civilisation into space.
He says NASA satellite data shows the average temperature in June was 0.43 degrees higher than normal. NOAA says it was 1.22 degrees higher.
That's because they measure completely different things. Satellites measure the lower troposphere, while NOAA uses ground based meteorological stations.
Especially in short time frames, the difference can be quite big. Over longer times, the average trend is similar, although some discrepancies have been observed too. See this page for a discussion: http://en.wikipedia.org/wiki/Satellite_temperature_measurements
He says too many of the weather stations NOAA uses are in warmer urban areas.
Funny how the NOAA anomaly map for 2010 shows hardly any warming in urban areas, and plenty of warming in thinly populated areas (Africa, Canada, and major oceans)
http://www.noaanews.noaa.gov/stories2010/images/map-blended-mntp-201001-201006.gif
Except that the existing greenhouse effect is already 33 degrees C, of which about 1/3rd is due to CO2.
The attenuations follows a log curve. Best current estimates are for increase of about 3 degrees C in global temperature for every doubling of CO2.
You realize that the possible effects of CO2 on the thermosphere, and the effects of CO2 on global climate are two completely different discussions ?
Going from 280 to 380 ppm is a relative increase of 35%. That's certainly a significant increase. Don't get distracted by the relatively small overall concentration in the atmosphere. This is completely irrelevant. What matters is the total mass of CO2 the light passes through from the sun to the earth's surface. This total mass has been increased by 35%.
Actually, the Antarctic ice cap is losing volume, even though it is gaining surface area. The Arctic ice cap is losing both volume and area. Greenland ice is also losing volume.
Europe may have had a cold winter, but globally the period Dec 2009-Feb 2010 was warmer than average. Similarly, the spring/early summer period was also warmer than average.
As far as the temperature on any given point on the globe, it's a combination of weather and climate. Global warming has pushed the averages up a little, but daily weather will always be the major factor in the temperature swings.
The Antarctic ice sheet isn't really melting, but the glaciers are moving at an increased speed, carrying more ice towards the edges (where it is melting).
The current model of coherent memory/identical time/everything can route to everywhere just can't scale to machines of this size
Why not ? Obviously, you can't have a million processors accessing the same variable in memory, but with a layered system of caches, you could keep most processors working in their own local copy. As soon as a processor writes to memory that's also used by another process, extra hardware will keep the memory coherent. This architecture is basically a superset of a message passing architecture (memory coherency signals are equivalent to messages), but much simpler for the CPU. Because the CPU isn't aware of the messages, this allows the coherency hardware to be improved without changing the program in any way.
You don't need to land the whole mass on the moon. Instead, you can land an almost empty fuel container, fill it up, launch that from the moon, and fill up your main craft in LEO.
It looks like every piece can also be rotated
I haven't had a wristwatch for many years, and I rarely miss it. Whenever I need to know the time, there's usually a clock nearby. After I got a cellphone, I've been using that to tell the time if there's no clock in sight, which is usually not more than once a day. If I forget to charge the phone, I'll survive without it.
Sounds reasonable in the US, perhaps. My provider here in .nl doesn't have throttling or bandwith caps, not even in the small print.
Only the oxides are harmful. When nitrogen is bound in other compounds, it works as a fertilizer. Plants need nitrogen, but they generally can't get it from the air, but they will readily absorb it from the soil.
The amount of water vapor is also more or less constant. If you try to put more vapor in the atmosphere, it will just rain out somewhere else.
Apparently not
You could just write down "sqrt(sin(53.128457638) + e^(3.563462378 * pi)) " on the answer sheet. The conversion to a single number is trivial with a calculator, so there is no need to include that in the exam.
Once you get infected with a trojan (which happens to a lot of people), it is trivial to put some fake public keys on your machine, or to insert a fake e-mail straight into your inbox.
My bank uses a better solution: they send me regular mail. They don't even have my e-mail address, so I can ignore any mail that claims to be from them.
Using a microkernel, the same bloat would be in the userspace drivers, so you gain nothing.
No, the Linux kernel is bloated because of all the features it has. Put the same features in Minix, and it would be at least the same size, and probably bigger.
Go ahead and post your public IP address, then.
http://imgs.xkcd.com/comics/the_drake_equation.png
Efficiency rate should be better than first converting it to liquid fuel and burning it a car. It's the same chemical energy stored in the atomic bonds, but it's all directly converted to heat. A big power plant has higher efficiency rate than a small internal combustion engine.
Emissions may be a concern, especially if the waste doesn't burn completely. To improve that, you could add some natural gas, or other fuel to increase temperature. The extra energy can also be converted to electricity. Other emissions, such as chlorine from PVC must be neutralized, but this is a known problem in waste incineration.