这个实验令人兴奋,因为它用到了如今人类的最高水平技术.但实验有两个潜在的问题,一是我们对暗能量了解有限,它会不会影响原子的波函数仍不确定,二是在这么低的能量下,有可能存在未知的力干扰实验.但不管如何,我们期待实验结果,希望是另所有物理学家眉开眼笑的结果.
作者: pwl1991317 时间: 2010-1-31 22:26
怎么不是英文的。。。。。。。。。。。。。作者: huashi3483 时间: 2010-1-31 22:27 How to Build a Dark Energy DetectorAll the evidence for dark energy comes from the observation of distant galaxies. Now physicists have worked out how to spot it in the lab.
The notion of dark energy is peculiar, even by cosmological standards.
Cosmologists have foisted the idea upon us to explain the apparent accelerating expansion of the Universe. They say that this acceleration is caused by energy that fills space at a density of 10^-10 joules per cubic metre.
What's strange about this idea is that as space expands, so too does the amount of energy. If you've spotted the flaw in this argument, you're not alone. Forgetting the law of conservation of energy is no small oversight.
What we need is another way of studying dark energy, ideally in a lab on Earth. Today, Martin Perl at Stanford University and Holger Mueller down the road at the University of California, Berkeley, suggest just such an experiment.
The dark energy density might sound small but Perl and Mueller point out that physicists routinely measure fields with much smaller energy densities. For example an electric field of 1 Volt per metre has an energy density of 10^-12 joules per cubic metre. That's easy to measure on Earth.
Of course there are some important differences between an electric field and the dark energy field that make measurements tricky. Not least of these is that you can't turn off dark energy. Another is that there is no known reference against which to measure it.
That leaves the possibility of a gradient in the dark energy field. If there is such a gradient, then it ought to be possible to measure its effect and the best way to do this is with atom interferometry, say Perl and Mueller.
Atom interferometry measures the phase change caused by the difference in two trajectories of an atom in space. So if a gradient in this field exists it should be possible to spot it by cancelling out the effects of all other forces. Perl and Mueller suggest screening out electromagnetic forces with conventional shields and using two atom interferometers to cancel out the the effect of gravitational forces.
That should allow measurements with unprecedented accuracy. Experiments with single atom interferometers have already measured the Earth's gravitational pull to an accuracy of 10^-9. The double interferometer technique should increase this to at least 10^-17.
That's a very exciting experiment which looks to be within reach with today's technology.
There are two potential flies in Perl and Mueller's ointment. The first is that the nature of dark energy is entirely unknown. If it exists and if there is a gradient, it is by no means certain that dark energy will exert a force on atoms at all. That will leave them the endless task of trying to place tighter and tighter limits on the size of a non-existent force.
The second is that some other unknown force will rear its head in this regime and swamp the measurements. If that happens, it's hard to imagine Perl and Mueller being too upset. That's the kind of discovery that ought to put a smile on any physicists face.
Ref:arxiv.org/abs/1001.4061: Exploring The Possibility Of Detecting Dark Energy In A Terrestrial Experiment Using Atom Interferometry作者: diguaaiqianqian 时间: 2010-2-1 16:24
很好，我很喜欢，激起了我的兴趣作者: rockhuman 时间: 2010-2-1 23:57
今年美赛考这个 昨晚有人来告诉我了。。。。。。。
嘘。。。。作者: rockhuman 时间: 2010-2-2 00:05
请问坛主是从哪里找到那么好的文章的呢？作者: 大笨象 时间: 2010-2-2 23:35
呵呵.确实不错..作者: wuhao080910 时间: 2010-2-5 23:15
似乎我们的论文与美国论文差距很大啊！作者: 梦游枪手 时间: 2010-2-6 22:54
飘过~~~~~~~~~~看不懂 呢作者: 明心见性 时间: 2010-4-6 22:22
呵呵.确实不错.......!!!!!!!!!!!!!!作者: love2008bin 时间: 2010-4-7 22:14
不错不错。呵呵。。。。。。。。。。。。作者: liuxn_2005 时间: 2010-4-11 10:40
确实不错.......!!!!!!!!!!!!!!。。。。。。。。。。。。。。。。。。。。。。。。
