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Evie
The Bat Cave EAR

Evie is an aeorspace engineer and will blog about current events in various fields including but not limited to: Space, Astronomy, Genetics, Biology, Green Energy, Neuroscience, Physics, Quantum Physics, Evolution, Environmental issues, Engineering.. Pretty much anything and everything that catches her eye. Stay tuned! Thoughts, comments, requests – always welcomed!

My posts are presented as opinion and commentary and do not represent the views of LabSpaces Productions, LLC, my employer, or my educational institution.

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Awesome Stuff
Monday, December 20, 2010

Credit: Wikipedia Back in the early 1900's, one of the many cool things Einstein found through his theory of General Relativity, was the theoretical existence of these things called Gravitational Waves.

As their name suggests they are predicted to be ripples, or fluctuations in the curvature of Space-Time, that propagate the way waves would, emanating from a source such as a black hole, neutron star, binary star, or any other ridiculously super massive object.

Apparently, Space-Time itself is curved, and becomes more or less curved depending upon the objects held in it. The more massive the object held in space-time is, the more curvature develops there.

When a highly massive object moves or gets accelerated, it affects that Space-Time significantly enough to cause these ripples or waves. The energy the waves carry and transport is called Gravitational Radiation, which travels at the speed of light and loses strength as it propagates, but never stops or even slows down.

Credit: The Hong Kong University of Science and TechnologyAlthough there has yet to be direct observation of these waves, there is plenty of data to support their existence in the form of indirect observation. Like the observations of orbits of binary pulsars, that seem to be losing orbital energy at the exact rate that General Relativity predicted they would, due to the emission of Gravitational Radiation.

The reason scientists are so excited about detecting these waves directly, is that this would not only confirm the validity of General Relativity in places where super high gravity is concerned, and allow us to learn tremendous amount about the sources of these waves, i.e. black holes and the like, but also this would give us a way to perceive things like dark matter and potentially dark energy, that cannot be detected using our current photon based technology.

The quest to find these elusive Gravitational Waves has brought forth a collaborative project by ESA and NASA called LISA or Laser Interferometer Space Antenna. Sadly it is still in early development, not expected to launch until 2020, and will take a year or so to get situated in place, but regardless, LISA is totally awesome.

It consists of 3 separate identical space crafts, that will be deployed to orbit the Sun in equilateral triangular formation, with each arm being 5 million km long, and lagging by 20 degrees, or 50 million km behind Earth.

Basically, each of the crafts will have 2 free floating cubes made of a gold platinum alloy, which will of course be shielded from adverse effects of space radiation. The distance between the cubes in the 3 different spacecrafts will be monitored continuously using super duper highly accurate laser based techniques, which have been in development for the past 6 years, just to be able to reduce the amount of noise to a level where the Gravity Waves will be detectable.

The 3 crafts will communicate through laser beams, which will pinpoint the exact location of each of the free floating gold alloy cubes, relative to each other at all times.

If a Gravitational Wave were to pass LISA, it would change the distance between the cubes ever so slightly,  by something on the order of a picometer, 10^-12 meters, like 100 million times smaller than a human hair. So pretty hard to detect.

That location data will be sent down to Earth continuously, where it will be processed. If the interference pattern found between the laser beams is the same, that means nothing has moved, and no Gravitational Waves passed by. However, in the event that the interference patterns that emerge are not the same.. well that means there was movement.

Those tiny fluctuations in position of those cubes, that cannot be accounted for by any other explanation, will be presumed as being caused by Gravitational Waves. Of course, the math, and engineering is a little bit more complex than that. But hopefully you get a bit of the picture.

Stay tuned for more LISA updates!


For more about LISA on the NASA site and on the ESA site
Wikipedia on Gravitational Waves
Cool Daily Galaxy post on the topic


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Trip

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I wonder how they account/compensate for variability in pressure from solar radiaion, which would peturb the orbit of these cubes?

Ned

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I know that the signal to noise problems encountered in space will overall be less than on earth.


Evie
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That's a good question. I haven't seen any details on how they're doing shielding, just that they are doing a hell of a lot of it.

Michele

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It's not so much shielding, as "drag-free operation". The cubes float inside housings in the spacecraft, and their positions are measured using capacitors and interferometry; when the cubes move with respect to the spacecraft, the spacecraft thrusters are actuated (ugly verb), so that the whole spacecraft follows the freely falling motion of the cubes.

Another way to look at this is that when solar pressure pushes on the spacecraft, these begin to move with respect to their freely falling cubes; this relative motion is detected and corrected. See lisa.nasa.gov for a little more about LISA technology.


Evie
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Thanks Michele, that is good to know. That is some precise thrusting capability on really small scales. I'd love to see how they accomplish that mechanically.

Hehe.. not a fan of the 'actuation' verb, eh?  I kind of like it. Has a nice Sci Fi ring to it :)

Dov Henis

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It takes a change of culture, of the mode of reactions to circumstances, to effect a change of habit. Genetics is the progeny of culture, not vice versa. This applies in ALL fields of human activities, including economy, to ALL personal and social behavioral aspects.

 Since the early 1900’s ALL “science” has been taken over by the Technology Culture of the religious Americans, represented by the trade-union-church AAAS. Plain and simple. There has not been any science in the world since then except “religious-American-science”.

 On the blissful religious science ignorance…:

 USA-World Science Hegemony Is Science Blind

 Since the early 2000s I have been posting many articles on science items surveyed and analyzed by me, without religious background-concepts. I have been doing this because I was deeply disturbed by the religiosity of the 1848-founded AAAS trade-union and by the consequent religious background-tint of  its extensive “scientific” publications and activities.

 On my next birthday I’ll be 88-yrs old. I know that I’m deeply engaged in a Don Quixotic  mission-war to extricate-free  the USA and world Science from the clutches and consequences of the religious-trade-union-church AAAS, adopted strangely by the majority of scientifically ignorant religious god-trusting Americans and by their most other humanity following flocks…

 But I am sincerely confident that only thus it is feasible and possible to embark on a new, rational, Human culture (Scientism) and on new more beneficial and effective technology courses for humanity…

 Dov Henis (comments from 22nd century)

http://universe-life.com/ 

Energy-Mass Poles Of The Universe

http://universe-life.com/2012/11/14/701/

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