Anyone in the generation who played video games as children---knows how nostalgic certain games can be.
Common, I wouldn't ever admit to playing a video game today (my high-brow crowed would scorn), but I do own a copy of The Legend of Zelda---and that is totally acceptable. If some NES games are acceptable in high-brow circles (while all current ones are excluded), doesn't this mean they are "high brow?"
And yes, Myst was a great game; and I am not afraid to admit I played it through.
In Nasa's latest tests, a 12ft-wide dish was used to concentrate the sun's rays on to 100g of a substance similar to Moon soil. After a few hours, one fifth of the substance had turned into oxygen.
Humans consume around 0.55 cubic meters of oxygen per day, or about 0.7 kilograms of oxygen per day.
This huge dish (heavy I bet!) is supposed to release 20 grams of oxygen every 'few hours'. So one disc releases around 100-200 grams each day. This means they would need about 3-5 huge, heavy discs per astronaut.
There are several ways to tell the difference between lab- and geologically made diamonds arising from the lack/presense of structural and chemicalimpurities.
Remember the four 'C's: cut, colour, clarity, and carat weight. Lab-made diamonds can now be produced with rather high carat weight, necessary to cut them into gemstones (30-70% of the material is removed in cutting). They are now being grown large enough to be cut as well as any diamond; so 'cut' and 'carat weight' can be the same for the two.
The crystal structure of laboratory diamonds can be made with few gross imperfections, causing the clarity to be quite high. In general, the types of lattice imperfections, decreasing clarity, are rather different for lab and geological diamonds, making it not too difficult to distinguish between the two when there are structural imperfections present. Only the very best crystals in each class would be hard to identify---those without many obviously lab-made or geologically-made lattice imperfections.
The 'c' that makes lab-diamonds not very marketable today is 'colour.' The colour of a diamond arises from natural or artificial chemical impurities. Natural diamonds have an enormous variety of colour because of the variety of (chemical) environments in which they are formed. Artificial diamonds tend to be produced in labs where they are all produced similarly, without much variety in (or any good way to control) the colour. Indeed, most artificial diamonds today are an intense orange-yellow colour because of the nitrogen introduced during processing. A natural orange-yellow diamond could be very expensive because of its rarity, but the market for such 'fancy' diamonds is substantially smaller than for white/clear diamonds.
Anyway, it will be a long time before you couldn't tell the difference. And when lab-diamonds can be made with arbitrary colour, size, and crystal strucuture, the easy way to tell the difference is the LACK of any natural imperfections.
Fine-tuning sounds great for an automobile, but in physics if a theory is fine-tuned it means that it is unnatural or unpredictive.
If you look at a reasonable plot of data, you can probably fit a curve through it. But where did that curve come from? If your theory admits any curve, then 'fine-tuning' the curve to fit the data is not much of an achievement. And if you 'modify the equations of gravity' so that rotation curves of galaxies match observation, while abandoning any fixed theorical principle for guidance, then you haven't done much. Unless of course you come up with a new theoretical principle---which is what Einstein did when he abandonded Newton's framework.
Gravity's interaction is _derived_ from general relativity. If you play around with the derived equations, you lose hope of understanding where they came from, and we're back with Newton. If you get rid of general relativity (which approximates to Newtonian theory in most reasonable every-day limits), then you also have a whole lot of new problems.
Modified Newtonian Gravity (MOND) theory has been around a long time. Dr Zhao's realisation is new, but not the idea or framework. As such, it solves the 'dark matter problem' while complicating many other things.
Evidence for the 'dark matter problem' comes from big bang nucleosynthesis, galaxy surveys, rotation curves, galaxy cluser dynamics observations, weak and strong gravitational lensing, the cosmic microwave background, and large scale structure simulations. Many of these problems are inter-related. MOND theories usually address roation curves while spoiling any hope of explaining all the rest.
Slashdot Mirror
Anyone in the generation who played video games as children---knows how nostalgic certain games can be. Common, I wouldn't ever admit to playing a video game today (my high-brow crowed would scorn), but I do own a copy of The Legend of Zelda---and that is totally acceptable. If some NES games are acceptable in high-brow circles (while all current ones are excluded), doesn't this mean they are "high brow?" And yes, Myst was a great game; and I am not afraid to admit I played it through.
Humans consume around 0.55 cubic meters of oxygen per day, or about 0.7 kilograms of oxygen per day.
This huge dish (heavy I bet!) is supposed to release 20 grams of oxygen every 'few hours'. So one disc releases around 100-200 grams each day. This means they would need about 3-5 huge, heavy discs per astronaut.
Just an observation.
There are several ways to tell the difference between lab- and geologically made diamonds arising from the lack/presense of structural and chemicalimpurities.
Remember the four 'C's: cut, colour, clarity, and carat weight. Lab-made diamonds can now be produced with rather high carat weight, necessary to cut them into gemstones (30-70% of the material is removed in cutting). They are now being grown large enough to be cut as well as any diamond; so 'cut' and 'carat weight' can be the same for the two.
The crystal structure of laboratory diamonds can be made with few gross imperfections, causing the clarity to be quite high. In general, the types of lattice imperfections, decreasing clarity, are rather different for lab and geological diamonds, making it not too difficult to distinguish between the two when there are structural imperfections present. Only the very best crystals in each class would be hard to identify---those without many obviously lab-made or geologically-made lattice imperfections.
The 'c' that makes lab-diamonds not very marketable today is 'colour.' The colour of a diamond arises from natural or artificial chemical impurities. Natural diamonds have an enormous variety of colour because of the variety of (chemical) environments in which they are formed. Artificial diamonds tend to be produced in labs where they are all produced similarly, without much variety in (or any good way to control) the colour. Indeed, most artificial diamonds today are an intense orange-yellow colour because of the nitrogen introduced during processing. A natural orange-yellow diamond could be very expensive because of its rarity, but the market for such 'fancy' diamonds is substantially smaller than for white/clear diamonds.
Anyway, it will be a long time before you couldn't tell the difference. And when lab-diamonds can be made with arbitrary colour, size, and crystal strucuture, the easy way to tell the difference is the LACK of any natural imperfections.
The Retro-Encabulator
Fine-tuning sounds great for an automobile, but in physics if a theory is fine-tuned it means that it is unnatural or unpredictive.
If you look at a reasonable plot of data, you can probably fit a curve through it. But where did that curve come from? If your theory admits any curve, then 'fine-tuning' the curve to fit the data is not much of an achievement. And if you 'modify the equations of gravity' so that rotation curves of galaxies match observation, while abandoning any fixed theorical principle for guidance, then you haven't done much. Unless of course you come up with a new theoretical principle---which is what Einstein did when he abandonded Newton's framework.
Gravity's interaction is _derived_ from general relativity. If you play around with the derived equations, you lose hope of understanding where they came from, and we're back with Newton. If you get rid of general relativity (which approximates to Newtonian theory in most reasonable every-day limits), then you also have a whole lot of new problems.
Modified Newtonian Gravity (MOND) theory has been around a long time. Dr Zhao's realisation is new, but not the idea or framework. As such, it solves the 'dark matter problem' while complicating many other things.
Evidence for the 'dark matter problem' comes from big bang nucleosynthesis, galaxy surveys, rotation curves, galaxy cluser dynamics observations, weak and strong gravitational lensing, the cosmic microwave background, and large scale structure simulations. Many of these problems are inter-related. MOND theories usually address roation curves while spoiling any hope of explaining all the rest.