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In 2008 astronomers discovered surprising amounts of water molecules where planets were forming near young stars. But how, they wondered, could those molecules survive? They should have been destroyed by ultraviolet radiation. In theory, planetary du
HEALTH REPORT - Health: Looking for Skin CancerBy Brianna Blake Broadcast: Tue, 4 Jul 2006 16:00:00 UTC I'm Faith Lapidus with the VOA Special English Health Report. Tanning beds produce ultaviolet ra
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Let's start with the people inside the plant. And their situation is not great. It's pretty clear they will be getting very high doses of radiation and certainly the potential for lethal doses of radiation. So you can - And they know it, don't they?
Sunscreened Plants 遮光植物 A NASA researcher is finding that alfalfa plants grow more poorly when exposed to UVB -- ultraviolet B radiation from the sun. Learn more about sunscreened plants -- today on Earth and Sky. JB: This is Earth and Sky. Eart
物理学 statics 静力学 motion 运动 inertia 惯性 gravitation 引力 relativity 相对 gravity 地心引力 vibration 震动 medium (media) 媒质 frequency 频率 wavelength 波长 pitch 音高 intensity 强度 echo 回声 resonance 回声,洪