A play-off, LISA pathfinder difficult set sail!
Launch day today LISA pathfinder, will pave the way for space gravitational wave detection.Image: ESA
UPDATE: LISA pathfinder has launched on December 3, is expected to spend 10 weeks is transferred to the final orbit.Expect the test!
Beijing time at noon Dec. 3 12:15, a vega rocket will be launched into space from French Guiana space center, will LISA Pathfinder (LISA Pathfinder) delivered to a day - 1.5 million kilometers to Lagrangian point 1.The detector worthy of the name, as LISA pathfinder, it will make the first step on the space observation of gravitational waves.
For physics, exactly a century ago, in 1915, is a year of some divine significance.This year, after 10 years of meditation, Einstein finally determine the describe the gravitational field equations.On November 25, 1915, he formally submitted papers describing the general theory of relativity formula.At the same time,
he did once a week, in the German academy of sciences report up to four weeks, officially announced to the world that a ground-breaking conclusions: gravity, but is the bending of space and time.
One hundred years later, at this moment, we will have exciting era.On September 18, 2015, after thoroughly remould oneself, the ground of the gravitational wave detector advanced LIGO formally began to work;Today, LISA pathfinder will officially launch up to heaven.We, our breath, listening to the universe.
This moment, probably Einstein did not dream of.Is deduced from the general theory of relativity, he soon realized, like waves, gravity is also in the form of wave propagation, and speed is the speed of light.He later wrote in the paper, there is no use, however, gravitational wave is too weak, can not detect.
Many scientists are desperately trying to prove Einstein wrong, a successful person is not much, detect gravitational waves of people is a part of it.Einstein did wrong this time: gravitational waves are very weak, but not can't detect.By using the method of laser interference, and a series of cow force in technology, we can detect very small disturbance of space and time.How small?Atom is small enough, if the extended our detector, a head in the earth, in the sun, the probe length even if only a atomic scale changes, we all need to detect it out.Such precision, advanced LIGO has now done.
The detector on the ground, however, have their own suffering.Precisely because it was so sensitive that they sensed it will be affected.Thousands of meters outside the truck drove by highway, dozens of kilometres away someone cut down a tree in the forest, hundreds of kilometres away waves patting beach, will leave traces on the LIGO detector.Due to the existence of noise, on the ground, we can only focus on high-frequency gravitational waves (100-1000 Hz), low frequency gravitational waves can only give up.To detect gravitational waves much lower frequency signal, it must be far away from the earth, into space.
Space to detect gravitational waves of projects is not like the ground so lucky.Space programme has always been famous for its high risk, in the event of failure, basically, instrument completely scrapped, unless the amount of money spent replacement parts (such as the Hubble telescope) or replace the scientific goal (such as a search for extrasolar planets Kepler telescope).
Space laser interferometer gravitational-wave detectors LISA, is put forward for the first time in the sixties and seventies of the last century, but to this day, distance from emission is still a distant prospect.Three detectors in the original design, formation, 5 million km away from the interference between two arm, is equal to the distance from the earth to the moon is 13 times, total can constitute three
interferometer.Distance so far, these satellites in the event of failure, it is impossible to repair.As for those who make detection accuracy to cow force of incredible technology... So to speak, cattle were stable and reliable, basic is a pair of antonyms in technology.
LISA had originally planned to use three probe spacing between 5 million km and constitute three space laser interferometer, used to detect gravitational waves signal.
In fact, LISA is expected to launch phase, has always been "about 10 years".Initially is halfway through the research and development, technology difficulty than expected, leading to launch delays;Eventually the technology mature gradually, tube satellite funds the people began to say, how do I know your technology is reliable?So LISA team proposed a compromise plan: first to launch a scout, are much cheaper than 3 satellite launch, the feasibility is also much higher.If
all normal, stable running and then the money to you then LISA, this is the origin of LISA pathfinder.
Confidence in everyone, such as the result of the with LISA pathfinder said (a) take (face) the pipe money the person, the financial crisis in 2007, NASA to slash spending, a large number of astronomical projects have been cut, LISA is no exception.Fortunately, this project from the start not NASA alone, pulled out of the americans, the European space agency ESA to take over.
ESA said surplus grain at home, however, is running out.LISA can only make concessions, to shorten the probe spacing to 1 million km, interference arm also fell to 2, can only form a interferometer, even names such as eLISA.I really want to say that her happy life ever after.Unfortunately, the reality is cruel.ELISA funds have wanted.Of course, strictly speaking, eLISA project still exists, just before 2034 are not enough funds can be fired.ELISA people began to stir, now look to the far east, looking for the cooperation of Chinese local tyrants;But our country is also planning to study space gravitational wave detector "tianqin plan".
Don't know what to say it's lucky, or unfortunately, LISA pathfinder launch has nailing on the plate, so still don't miss the launch.Originally is enthusiastic to LISA, can only hope that the pathfinder outstanding performance.After all, 20 years later can get funds to LISA lives, in this blog.
So, just to do what LISA pathfinder?
Basically, the whole 1 million km is LISA within a baseline enriched to a satellite, let two 38 centimeters apart without drag gold platinum cube in weightlessness, shielding the outside world through a series of technology of various factors on the interference of two cubes, intermittently with fairly small and quite accurate driver control these little cubic don't run out, and then their geodesic deflection is measured with a laser interference technique.
In other words, free fall.Yes, free fall, not only in physics textbooks and exercises, also appeared in the most cutting-edge scientific research frontier.
LISA pathfinder, is to ensure that two gold platinum cube in freefall, and small changes during laser interference measurement distance.So, it needs to fly to earth's gravity and Lagrangian point of the sun's gravity balance each other, let two measured interval of 38 cm cubes is in a state of free falling (gravity).Probe all functions, it is to ensure that the belly of the two cubes free fall, don't accept outside interference.
LISA pathfinder mission, is to ensure that its internal two gold platinum cube in freefall, and small changes during laser interference measurement distance, eLISA will be used to verify that the future of the technology is feasible.Image: ESA
Free fall is not difficult, difficult is real to the measuring accuracy of outrageous (10 m, atomic radius is 100 times larger than the number).Think about it, even the detector in the layout of the different parts with a precise computer modeling to modify weight repeatedly, can balance the two gold platinum cubic by the gravity of the detector itself.
In addition, you have to try to keep two gold platinum cube in a very narrow range.Within a certain range to let two cube free flap, drifting too far, you can correct it, to continue.This a waving a correct have greatly exquisite, need to be very small and very precise controller, and all this in a smaller detector.Think about have to sigh with emotion, this is strictly a spiral lions do dojo in the shell.
Of course, LISA pathfinder mission is to test whether the technology of cow force is able to run normally.Simple two examples.Gravity is very weak, you jump, the electromagnetic force will be able to use the leg against the earth's gravitational pull on you.Such a tsundere gravity, too easily affected by other factors, so the gold platinum cube is really see the light die - not to say that she was afraid of sunburn, but said that the sun has light pressure, gold platinum cubic will be pressure to promote and no longer is in a state of free fall.In addition, the rocket launch satellites will experience strong acceleration and turbulence, such a precision instrument if the launch is broken, always can not funny.
These difficulties, we can think of, unexpectedly, had been LISA feel scientists solved one by one.Immediately, is the moment when the witness miracle - tomorrow,
our group to do LISA half will attend the launch of National People's Congress, and
we in the soy sauce party will be assembled at 4 PM local time on watching TV in the
office, on the flying ramen great god pray, hope everything goes well with fire.