Scientific Minds Want To Know
For five decades, most attempts at weather modification involved cloud seeding, a process usually meant to trigger rain by dispersing certain chemicals from airplanes. Thing is, it may not even work very well wile its environmental impact is cause for concern. Now, researchers from the University of Geneva are exploring whether firing lasers into the sky could stimulate rain more effectively and safely. They've published results from their experiments in the journal Nature Photonics.From Nature News:
Firing a laser beam made up of short pulses into the air ionizes nitrogen and oxygen molecules around the beam to create a plasma, resulting in a 'plasma channel' of ionized molecules. These ionized molecules could act as natural condensation nuclei, (optical physicist Jérôme) Kasparian explains.
To test whether this technique could induce droplets, the researchers fired a high-powered laser through an atmospheric cloud chamber in the lab containing saturated air. They illuminated the chamber using a second, standard low-power laser, enabling them to see and measure any droplets produced. Immediately after the laser was fired, drops measuring about 50 micrometres wide formed along the plasma channel. Over the next three seconds, the droplets grew in size to 80 micrometres as the smaller droplets coalesced.
The next step for Kasparian and his team was to take the technique outside....
Kasparian and his colleagues tested the (high-powered, portable) Teramobile laser over a number of different nights and in various humidity conditions. Once again, they detected the amount of condensation induced by monitoring how much the light from a second laser was back-scattered by any droplets. In low humidity conditions, the Teramobile laser did not induce droplets. But when the humidity was high, the team measured up to 20 times more back-scattering after the Teramobile laser was fired than before, says Kasparian, suggesting that condensation droplets were forming.
Working in a rare, "natural seafloor laboratory" of hydrothermal vents that had just been rocked by a volcanic eruption, scientists from the Woods Hole Oceanographic Institution and other institutions have discovered what they believe is an undersea superhighway.
Some Black Holes can kill galaxies
Although nothing can escape from a black hole, before matter falls into one, it swirls around to form a disk that heats up as it packs together, radiating energy.
Supermassive black holes are thought to reside at the center of almost every galaxy, with some growing to billions of times the mass of our sun. To see what impact these monsters might have, researchers relied on data from the Hubble Space Telescope and the Chandra X-ray Observatory, looking for galaxies with very high X-ray emissions, a classic signature of black holes devouring gas and dust.
The scientists discovered the accretion disks of super-massive black holes in at least one-third of all the massive galaxies in the universe far outshines the combined output of the hundreds of billions of stars in their host galaxies at some point in their histories. This outpouring of energy is high enough to strip apart every massive galaxy in the cosmos 25 times over, while the X-ray emission from them turns out to dwarf that from every other source in the universe put together.
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