Slashdot is powered by your submissions, so send in your scoop

 


Forgot your password?
Close
typodupeerror
×

Submission + - Finding your longitude on Earth with Jupiter's moons 1

Submitted by StartsWithABang
StartsWithABang writes: If you want to know where you are on Earth, you typically use a GPS or, barring that, other terrestrial landmarks to help determine your location. If you didn't have access to that sort of technology or knowledge, you could still use some well-known objects in the sky to determine your latitude. Longitude, however, is trickier, since it's arbitrarily defined. Perhaps surprisingly, for centuries, the best way to determine it was by using the moons of Jupiter, and watching when they enter/exit the shadow of the giant planet.

Submission + - Is a Climate Disaster Inevitable?

Submitted by HughPickens.com
HughPickens.com writes: Astrophysicist Adam Frank has an interesting article in the NYT postulating one answer to the Fermi paradox — that the human evolution into a globe-spanning industrial culture is forcing us through the narrow bottleneck of a sustainability crisis and that civilization inevitably leads to catastrophic planetary changes. According to Frank, our current sustainability crisis may be neither politically contingent nor unique, but a natural consequence of laws governing how planets and life of any kind, anywhere, must interact. Some excerpts:

The defining feature of a technological civilization is the capacity to intensively “harvest” energy. But the basic physics of energy, heat and work known as thermodynamics tell us that waste, or what we physicists call entropy, must be generated and dumped back into the environment in the process. Human civilization currently harvests around 100 billion megawatt hours of energy each year and dumps 36 billion tons of carbon dioxide into the planetary system, which is why the atmosphere is holding more heat and the oceans are acidifying.

All forms of intensive energy-harvesting will have feedbacks, even if some are more powerful than others. A study by scientists at the Max Planck Institute in Jena, Germany, found that extracting energy from wind power on a huge scale can cause its own global climate consequences. When it comes to building world-girdling civilizations, there are no planetary free lunches.

By studying these nearby planets, we’ve discovered general rules for both climate and climate change (PDF). These rules, based in physics and chemistry, must apply to any species, anywhere, taking up energy-harvesting and civilization-building in a big way. For example, any species climbing up the technological ladder by harvesting energy through combustion must alter the chemical makeup of its atmosphere to some degree. Combustion always produces chemical byproducts, and those byproducts can’t just disappear

Submission + - The future of stars like ours, in visuals

Submitted by StartsWithABang
StartsWithABang writes: When stars between about 40% and 800% the mass of our Sun run out of hydrogen fuel in their cores, they expand into a red giant phase, burning helium in their center. The intense stellar winds produced blow off the star’s outer layers, and when the core runs out of helium to burn, the central region contracts to a white dwarf, producing intense ultraviolet light that lights up the expelled gas and ions, often found in extremely rare ionization states: a planetary nebula. Here's the story of the Cat's Eye Nebula, one of the closest, most detailed planetary nebulae of all, as told (mostly) through pictures.

Submission + - Finding ET – we're gonna need a bigger dish (newscientist.com) 1

Submitted by Z00L00K
Z00L00K writes: The hunt for alien civilisations may need a rethink. A new paper argues that the signals we're listening for might not be the ones ET would choose.

Historically, SETI – the search for extraterrestrial intelligence – involves scanning the sky for radio signals that another civilization is deliberately sending. The simplest would be a constant blast in all directions, but in a narrow range of frequencies, similar to early radio broadcasts – like a constant hum that would tell a listener it is artificial. From light years away, we would not be able to get any other information – all we would be able to tell from Earth is that a signal was there and where it was coming from, not what it says.

Submission + - All in good clean fun! United Launch Alliance CEO pokes at SpaceX via Twitter (adweek.com)

Submitted by braindrainbahrain
braindrainbahrain writes: The new CEO of the United Launch Alliance, Tory Bruno shows his funny side as he pokes fun at his main competitor in the space launch business, SpaceX. So much so, that he got a mention, along with some of his twitter barbs, in Adweek, a publication not generally known for reporting on the aerospace industry.

Slashdot Top Deals

God help those who do not help themselves. -- Wilson Mizner

Close