• A Cosmic Gravitational Wave Background?
    25 replies, posted
[QUOTE] by Paul Gilster on November 24, 2010 A gravitational wave is a ripple in spacetime, one that follows naturally from the theory of general relativity — Einstein did, in fact, predict the existence of such waves back in 1916. Yet so far we have had nothing but an indirect detection in the form of the Hulse-Taylor binary (PSR B1913+16), a pulsar in a binary system that includes a second neutron star, the two orbiting around a common center of mass. The 1993 Nobel Prize in physics went to Richard Hulse and Joseph Hooton Taylor (Princeton University), who showed that the system’s orbital decay corresponds with the loss of energy due to the kind of gravitational waves Einstein predicted. What we now need is a direct detection, but these waves have proven to be a tricky catch. Consider this: The distance between two spacecraft flying five million kilometers apart would be changed by about a picometer by the effects of gravitational waves. That’s a distance 100 million times smaller than the width of a human hair, some .000000000005 meters. Yet it’s the distance scientists hope to measure with the LISA mission (Laser Interferometer Space Antenna), in which three spacecraft will fly in a triangle connected by laser beams, a formation flight orbiting the Sun roughly 20 degrees behind the Earth. The plan: Aboard each of the spacecraft will be a cube of platinum and gold that floats freely in space. Passing gravitational waves should cause the distance between the cubes to vary, and the good news out of the Jet Propulsion Laboratory this week is that after six years of working on the LISA technology, scientists have tuned its phase meters (laser beam detectors) to the point where such a detection should be possible, the laser ‘noise’ dropping sufficiently to allow the evanescent wave signature through. Thus JPL physicist Bill Klipstein: [QUOTE] “In order to detect gravitational waves, we have to make extremely precise measurements. Our lasers are much noisier than what we want to measure, so we have to remove that noise carefully to get a clear signal; it’s a little like listening for a feather to drop in the middle of a heavy rainstorm.”[/QUOTE] A feather in a rainstorm indeed, and even that seems to understate the case. JPL is now demonstrating that its instruments are sensitive enough to make detecting gravitational waves a possibility. The principle should sound familiar, as it’s basically interferometry (though with a time delay), often discussed here in terms of pooling the resources of multiple telescopes so as to produce an effective aperture equal to the separation of the telescopes. In LISA’s case, the three spacecraft are affected by passing gravitational waves so that the distances between the test masses changes, a fact revealed by the distances traveled by the laser beams of light. Ground-based data processing will then tell us whether the light detected by the onboard phase meters shows any variation in distance between the spacecraft. By introducing artificial noise into their detectors, the JPL team has been able to show that its data processing techniques can filter it out, highlighting those one-picometer distance changes scientists hope to see. The LISA mission is a joint project between the European Space Agency and NASA that would launch around 2020 if selected. The National Research Council’s decadal report, which more or less put an end to the Space Interferometry Mission, has given LISA a high recommendation. [IMG]http://www.centauri-dreams.org/wp-content/uploads/2010/11/gravitational-wave-sky-new.jpg[/IMG] Image: The gravitational-wave sky, as observed by LISA. The plane of the Galaxy is visible as the white horizontal band of emission from millions of Galactic binaries. The dots and squares mark the locations of a small fraction of the black-hole mergers and capture events that LISA will observe, while the purple background represents the relic gravitational radiation that LISA may detect from the very early Universe. Credit: NASA/ESA. If it succeeds, the LISA mission will open up a new way of observing the universe, looking for low frequency gravitational waves (0.03 milliHertz to 0.1 Hertz), a band thought to contain the emission from massive black hole binaries of the kind that form after the merger of entire galaxies. Gravitational waves are all about huge astronomical events like this, generated by compact objects like stellar remnants falling into galactic black holes and neutron stars in tight binaries. The behavior of spacetime when pushed to extremes may teach us not only about dense matter and stellar remnants, but about the expansion history of the universe itself. What would a Cosmic Gravitational Wave Background look like, and what could it tell us about the earliest moments of the universe? Remember that the Cosmic Microwave Background emerged about 400,000 years after the Big Bang, and represents the oldest light we can see via electromagnetic astronomy. Gravitational waves should be able to propagate to us from before that era, making them a probe of the early universe that could identify the existence of new fundamental objects like cosmic superstrings, if they exist, thus offering a window into the various models of string theory and sketching the history of the phase transitions that shaped the cosmos. [IMG]http://www.centauri-dreams.org/wp-content/uploads/2009/05/tzf_img_post.jpg[/IMG] [/QUOTE] Source: [url]http://www.centauri-dreams.org/?p=15438[/url]
:aaaaa: Holy shit.
Hot damn.
im underwhelmed
Stop being a idiot this could change everything. Good work Eudoxia.
you know nothing
Sounds like a really difficult task.
First steps towards inventing artificial gravity generators?
:psyduck: this is why I'm not an astrophysicist
[QUOTE=Eudoxia;26266619][img]http://www.centauri-dreams.org/wp-content/uploads/2009/05/tzf_img_post.jpg[/img][/QUOTE] If i see that image one more time
I'm proud to study at the European University where LISA is being build :) (Leibniz University Hannover in conjunction with the Albert Einstein Institute of Gravitational Physics - AEI-MPG) [editline]24th November 2010[/editline] [QUOTE=cyanidem;26268885]Sounds like a really difficult task.[/QUOTE] It is. I know GEO600, the gravitational wave detector here in Hannover (actually in Sarstedt, 6 km from my Home :P), and the main problems are noises - Thermical, seismic etc, they all limit the sensitivity. For LISA, the seismic noises are gone and you can measure gravitational waves in lower frequency ranges a lot better where seismic noise doesn't allow it here on earth.
[QUOTE=aVoN;26271800]Leibniz University Hannover[/QUOTE] I read that as "Lesbian University Hangover". Todays society has irreversibly damaged my brain.
[QUOTE=hypern;26267850]Stop being a idiot this could change everything[/QUOTE] Okay then, explain how it will change everything.
[QUOTE=Mingebox;26272050]Okay then, explain how it will change everything.[/QUOTE] Read the fucking article.
I think sometimes a td;du is required for some people. That is, too dumb, didn't understand :v:
[QUOTE=BloodStream;26277183]Read the fucking article.[/QUOTE] I did, and I'm pretty sure the magical world of proving the existence forces that we're mostly sure exist anyway doesn't encompass "everything"
Reminds me of the Cavendish Experiment, albeit on a larger scale and more defined and precise, and for measuring distance instead of a gravitational constant.
My grandfather worked at JPL. on the apollo missions.
I can´t stop thinking of a SGU episode [sp]Message in the cosmic background radiation[/sp] Other then that. I can´t really imagine the timescale their talking about
[QUOTE=hypern;26267850]Stop being a idiot this could change everything. Good work Eudoxia.[/QUOTE] what did eudoxia do
[QUOTE=Mingebox;26278311]I did, and I'm pretty sure the magical world of proving the existence forces that we're mostly sure exist anyway doesn't encompass "everything"[/QUOTE] It proves that gravity in fact is a wave. As of right now, we can't really say what gravity really is.
Trying to comprehend this makes my balls ache. No kidding.
Does that mean we can generate counter-waves to float?
[QUOTE=Mr. Someguy;26287595]Does that mean we can generate counter-waves to float?[/QUOTE] Why yes, it is. You do have a gravity wave generator, do you? I looked at the 7/11 and couldn't find any, so maybe I'll go out to Walmart and see if they have any there.
[QUOTE=Mingebox;26287716]Why yes, it is. You do have a gravity wave generator, do you? I looked at the 7/11 and couldn't find any, so maybe I'll go out to Walmart and see if they have any there.[/QUOTE] This is not how Gravity Waves work...
[QUOTE=aVoN;26291611]This is not how Gravity Waves work...[/QUOTE] sorry but they dont work until next year
Sorry, you need to Log In to post a reply to this thread.