外语教育网
您的位置:外语教育网 > 行业英语 > 天文学英语 > 相关阅读 正文
  • 站内搜索:

在火星上,嗓门可得大一点!

2006-07-28 18:01

  Sound dies quickly in the cold, thin air of Mars. Researchers have modeled a sound wave traveling through the Martian atmosphere and report that it doesn't go far——even a lawn mower's roar dies after a hundred meters or so. The model presents an unusually detailed picture of how sound travels in an alien atmosphere and hints at what it would take to communicate on the Red Planet.

  The shriek of a baby, an ambulance's siren, or a violin sonata are all essentially the same thing: waves of pressure traveling through the air. Sound can also travel through water, or a solid like the ground, but because molecules must bump into each other to propagate the pressure wave, the denser the medium the better. Hoofbeats or footsteps travel farther through the ground than through the air, for example, because the molecules in air have to travel further to bump into one another than those in soil, thus losing energy more quickly.

  The Martian atmosphere is mostly carbon dioxide and only 0.7% as dense as Earth's is, so sound should fade more quickly. But the details of how sound waves travel in the Martian atmosphere were unclear and could be important to future Mars missions.

  Now, a computer model has given a molecule-by-molecule map of how sound moves on Mars. Graduate student Amanda Hanford and physicist Lyle Long of Pennsylvania State University in State College presented the model last week at a meeting of the Acoustical Society of America meeting in Providence, Rhode Island. The model is unusual in its molecular approach; most acoustical models of sound treat the medium it travels through as a continuous block with average properties. Such models are fine for dense atmospheres like Earth's, but treating the air like a loose bunch of freewheeling molecules is more realistic for Mars' rarefied atmosphere, say the researchers.

  Hanford and Long first set up a virtual "box" filled with about 10 million carbon dioxide molecules floating about randomly, at the same density as the Martian atmosphere. A sound wave then appeared on one side of the box, and the model calculated its progress across to the other side, computing nanosecond by nanosecond exactly how the carbon dioxide molecules bumped and moved. The results show that a noise that would travel several kilometers on Earth would die after a few tens of meters on Mars. Quieter sounds would travel far shorter distances, making eavesdropping on a quiet conversation nearly impossible.

  Henry Bass, a physicist at the University of Mississippi in Oxford, notes that if people ever go to Mars and want to communicate audibly, they'll need to design devices that can work with the lower frequencies transmitted by the Martian atmosphere.

相关热词:天文学 英语 相关 阅读
行业英语辅导课程
李 健协和医科大学医学博士,美国国立卫生研究院博士后……详情>>
李健:医学英语网上辅导名师
高 云澳大利亚注册会计师协会会员,会计专业硕士……详情>>
高云:财会英语网上辅导名师
李文沛中国政法大学博士,师从著名法学家周忠海教授……详情>>
李文沛:法律英语网上辅导名师

  1、凡本网注明 “来源:外语教育网”的所有作品,版权均属外语教育网所有,未经本网授权不得转载、链接、转贴或以其他方式使用;已经本网授权的,应在授权范围内使用,且必须注明“来源:外语教育网”。违反上述声明者,本网将追究其法律责任。
  2、本网部分资料为网上搜集转载,均尽力标明作者和出处。对于本网刊载作品涉及版权等问题的,请作者与本网站联系,本网站核实确认后会尽快予以处理。本网转载之作品,并不意味着认同该作品的观点或真实性。如其他媒体、网站或个人转载使用,请与著作权人联系,并自负法律责任。
  3、联系方式
  编辑信箱:for68@chinaacc.com
  电话:010-82319999-2371