我与小娜（14）：引力波是怎样探测的？

我与小娜（14）：引力波是怎样探测的？

        小娜知道: An interferometer like LIGO consists of twoperpendicular (相互垂直)"arms"(in LIGO's case each one is 4km long!) along which a laser beam（激光束） is shone（发射） and reflected（反射） by mirrors at each end.

        小娜知道，When a gravitational wavepasses by, the stretching（拉长） and squashing（压扁） of space causes（引起） the arms of the interferometer alternatelyto lengthen（增长）and shorten（缩短）, one getting longer while the other getsshorter and then vice-versa.

        小娜知道，As the interferometers' armschange lengths, the laser beams traveling through the arms travel differentdistances - which means that the two beams are no longer（不再） "in step"（同步） and what we call an interference pattern isproduced（引起干涉模式）. (This is why wecall the LIGO instruments "interferometers".)

    小娜知道，Now the effect of this change in arm length is very small -- for atypical passing gravitational wave we expect it to be about 1/10,000th thewidth of a proton（大有质子宽度的万分之一）!

    小娜知道，But LIGO's interferometers are so sensitive（如此灵敏） that they can measure evensuch tiny（微小） amounts.

    小娜知道，LIGO scientists can look for the pattern of arm length changes that weexpect from different types of gravitational wave source: if they see thepattern, they'll know a gravitational wave has passed by!

    我认为，探测引力波的技术原理很简单，但是，实际做起来却不容易，为什么？且听下回分解。

袁萌  2月17日[1]

 

[1]