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A Galaxy-Sized Observatory For Gravitational Waves

kdawson posted more than 5 years ago | from the galaxy's-your-oyster dept.

Space 190

KentuckyFC writes "Gravitational waves squash and stretch space as they travel through the universe. Current attempts to spot them involve monitoring a region of space several kilometers across on Earth for the telltale signs of this squeezing. These experiments have so far seen nothing. But by monitoring an array of pulsars throughout the galaxy, astronomers should be able to see the effects of gravitational waves passing by. They say such an array of pulsars should effectively shimmer as the gravitational waves wash over it, like a grid of buoys bobbing on the ocean. That'll create an observatory that is effectively the size of the entire galaxy. These observations should be capable of monitoring how galaxies and supermassive black holes evolve together, and shed light on the physics of the early universe. Best of all, the next generation of radio-telescope arrays should be capable of making these observations at a cost of around $66 million over ten years. That's a small fraction of the hundreds of millions that Earth-based observatories have already cost."

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Guess LIGO failed too many times (-1)

Anonymous Coward | more than 5 years ago | (#29432419)

See http://www.thunderbolts.info/thunderblogs/davesmith_au.htm [thunderbolts.info] and also http://www.thunderbolts.info/thunderblogs/guest.htm [thunderbolts.info] . I guess when you look for evidence of something and find absolutely nothing, it's okay not to abandon the theoretical reasons why you looked for it in the first place. Clearly you just need to use a galaxy as a detector this time. Yeah, right. How scientific. How long will it be until you guys quit defending this non-falsifiable bullshit and learn what Karl Popper [wikipedia.org] tried to teach us a long time ago?

Re:Guess LIGO failed too many times (3, Informative)

A beautiful mind (821714) | more than 5 years ago | (#29432521)

What do you mean finding absolutely nothing? They just ruled out the higher end of the spectrum for gravitational waves. They learned a lot in building very precisely calibrated instruments to do the gravitational wave detection. They continue to lower the detection threshold.

Re:Guess LIGO failed too many times (0)

Anonymous Coward | more than 5 years ago | (#29432585)

That's not how the General Public views how science works. If it doesn't immediately give them a bigger erection, bigger breasts, or a fuller head of hair it is deemed a failure and should not be funded further. Sad but true, we're surrounded by IDiots.

Re:Guess LIGO failed too many times (1)

sadness203 (1539377) | more than 5 years ago | (#29433003)

Nothing to do with iDiots. Or does it ?

Re:Guess LIGO failed too many times (-1, Troll)

Louis Savain (65843) | more than 5 years ago | (#29433187)

This is precisely this type of condescending, we-are-am-smater-than-you attitude that turns people off on science and scientists. Maybe physicists should concentrate on the foundational issues (e.g., the true nature of motion) first before they go chasing after gravity waves. You folks are not as smart as you think you are.

Did you know that over 90% of physicists believe that matter can move in spacetime even though it is known that spacetime is frozen from the infinite past to the infinite future? Did you know that physicists have no clue as to what keeps a moving particle in motion? Did you know that most physicists believe that moving bodies remain in motion for no reason at all, as if by magic?

My own research, based on the application of the principle of causality to motion, has led me to conclude that we are swimming in a enormous sea of energetic particles. Having a correct causal model of motion will unleash an age of free energy and extremely fast transportation.

The Problem With Motion [blogspot.com]

Re:Guess LIGO failed too many times (1)

Goaway (82658) | more than 5 years ago | (#29433691)

Is it Crackpot Hour on Slashdot tonight? First electric universe, and now free energy?

Re:Guess LIGO failed too many times (-1, Troll)

Louis Savain (65843) | more than 5 years ago | (#29433981)

If you got any gonads, identify yourself and be on the record. Why be ashamed of what you are? A little bit of gonads is all it takes. :-D

Re:Guess LIGO failed too many times (4, Insightful)

Chris Burke (6130) | more than 5 years ago | (#29432845)

What do you mean finding absolutely nothing?

Judging by his links to thunderbolts.info, what I think he means is "I'm a crazy idiot who doesn't understand anything, and think this is a sound foundation to question the work of scientists everywhere. Solar wind is caused by an electric field! What do you mean it's a plasma with equal amounts of positive and negative charges, and a field can't move opposite charges in the same direction? No really, I have no idea what you're talking about because I never too physics in school! But my theories are right anyway!"

Re:Guess LIGO failed too many times (2, Informative)

John Hasler (414242) | more than 5 years ago | (#29433511)

> They just ruled out the higher end of the spectrum for gravitational waves.

No. They failed to detect high-frequency gravitational radiation above a certain level. Conventional theory predicts that the radiation they failed to detect should be fairly rare, so the result tends to confirm the established theory while leaving the proponents of some alternative theories with some explaining to do.

That's dumb (0, Troll)

tjstork (137384) | more than 5 years ago | (#29433963)

Maybe we're just skeptical and don't believe that they exist until you can prove that they do. I thought that was called science. What you are saying is that Santa Clause exists,but you just haven't seen him yet. Let me know when he shows up.

Re:That's dumb (1)

A beautiful mind (821714) | more than 5 years ago | (#29434053)

Gravitational waves are a consequence of general relativity, so IF gravitational waves don't exist then GR is at least partly wrong. That's a bit stronger than believing in Santa Claus I'd think.

Re:That's dumb (3, Informative)

Profane MuthaFucka (574406) | more than 5 years ago | (#29434311)

The guy you're responding to, tjstork, is an idiot, not worth your time. He's also a conservative, but I repeate myself. The only reason it's relevant is that his opinions come from his ideology. In his mind, you are already wrong because you like science, and science is paid for in large part by public dollars. This makes science the enemy to him.

He'll stick to his scientifically ignorant position, and you will fail to educate him.

Just a heads up.

Re:That's dumb (0, Troll)

tjstork (137384) | more than 5 years ago | (#29434837)

He'll stick to his scientifically ignorant position, and you will fail to educate him.

Oh look at you, the same old lying liberal pig as ever. All you talk about is learning with one hand while on the other you ban owning chemistry sets, get rid of electricity experiments in schools, forbid kids from flying rockets in fields, or planes, or working with any sort of mechanical thing in the name of safety.

You can talk about how much you love science and point your crooked and greedy finger at religion as the supposed enemy of man, but the fact is, science is even more the enemy of you communists, because you sick and subhuman traitors are not interested in humanity advancing as much as you are in every human being the exact same thing. You ban altering the earth in every conceivable way, all the while laughing at people caught up in your lies of environmentalism and safety.

Yet, the truth is really simple, you evil bastard. You can't learn about biology unless you cut the animal open first. You can't learn about the earth unless you dig inside it. You can't learn about the sky unless you fly in it. You can't learn about chemicals until you mix them. The more you block people from doing it, the more you spread ignorance throughout humanity.

And the thing is, your side is doing it deliberately, because at the end of the day, you want to hoard knowledge, not share it.

Re:That's dumb (1)

tjstork (137384) | more than 5 years ago | (#29434957)

Gravitational waves are a consequence of general relativity, so IF gravitational waves don't exist then GR is at least partly wrong. That's a bit stronger than believing in Santa Claus I'd think

Well, if GR was wrong on that score, don't you think physics would suddenly get a lot more interesting? I mean, seriously, its the prospect of Santa Claus popping up and gravity waves not being there that really, fundamentally, the human force that drives science. People want to be surprised by the experiments that they do.

Re:That's dumb (1)

Fallen Seraph (808728) | more than 5 years ago | (#29434551)

No, you really, really, don't get it. It's not like someone one day decided there are gravity waves, and conned people into spending millions on tests for them.

Eintein's theory of General Relativity (GR) predicts that gravity waves exist, and GR has already made several other verified predictions. It's a bit like a boat in the water. What we've verified with GR already is that the boat displaces water, this is the distortion that objects with mass cause to occur on spacetime. Gravity waves would be the wake the boat leaves behind as it moves through the water.

This is expected to be most evident in binary star systems, as the stars rotating around one another have a relatively high angular momentum, as well as the large masses required to make gravity waves easier to detect.


Now, your analogy to Santa Claus is pretty bad, what with Santa being based on myth and all, but if we ignore that for a second and ran with it, it'd be saying something like this:
We can see a flying sled, pulled by reindeer in the sky between December 24th and 25th. Also, any house this sled visits finds mysteriously delivered presents under their Christmas tree, which no one in the house placed there. We haven't seen anyone in the sled, but we believe that the sled is related to the presents appearing on that particular night. So now we're looking for the little man in the sled (maybe it's an elf, maybe it's Santa, maybe it's Jack Skellington for all we know) that we believe is dropping off the presents. For the last experiment, we looked for things at eye level, but saw no one. Therefore, if there is someone coming into the house from the sled, they must be shorter than 6', thereby ruling out Jack Skellington. We have now developed a new tests that will look two foot above, and two foot below our eye level.



Science isn't just about observing events and figuring out the cause. It's also about attempting to make predictions based on existing knowledge, and verifying those predictions with experiments.

PS - Wow, that analogy was painful to continue running with <.<

Better there are no gravity waves. (1)

tjstork (137384) | more than 5 years ago | (#29434785)

Eintein's theory of General Relativity (GR) predicts that gravity waves exist, and GR has already made several other verified predictions. It's a bit like a boat in the water. What we've verified with GR...

No, but my point is that every breakthrough in physics came through because people were ho hum and looking through some theory where they expected to find a result, and didn't. Once upon a time people thought Newtonian mechanics was all there was. We think 100 years of Einstein (wow!), is a long time, but just imagine 300 years of Newtonian physics. All these famous problems that lead to quantum physics - like where does the sun get its energy from, black body radiation, brownian motion, etc, are all really edge cases of newtonian physics.

Science isn't just about observing events and figuring out the cause. It's also about attempting to make predictions based on existing knowledge, and verifying those predictions with experiments.

But its not really useful, unless those predictions were wrong. That's my point. If they find gravity waves, and it confirms GR, that's all well and good but it doesn't really do anything useful as it doesn't change anything and in that sense its a waste of money. But, if there are no gravity waves, or, more spectacularly, there is no Higgs Bosun, then, really, our understanding or rather, physics understanding, of how gravity and mass works is completely wrong, and that would be as interesting as when Rutherford first aimed a beam at a gold foil and realized that the density of the gold is not uniform and got a rather surprising finding about how small atomic nuclei are relative to the size of the space around them.

Re:Guess LIGO failed too many times (4, Informative)

techno-vampire (666512) | more than 5 years ago | (#29432787)

I guess when you look for evidence of something and find absolutely nothing, it's okay not to abandon the theoretical reasons why you looked for it in the first place.

That's correct. Lack of evidence isn't enough to disprove a theory; what you need is evidence that directly contradicts the theory. In the case of gravity waves, it might be observation of an event that should produce detectable gravity waves, combined with our not detecting them.

And, while I'm at it, I'd like to point out that what Popper taught us was that a theory was useless unless there's a way to falsify it, at least in theory. If you can find a way to show that any conceivable experimental results can be viewed as confirming the theory, it's useless because it can't be tested. In the case of gravity waves, they're but one of many things predicted by General Relativity, and one of the few that's not been observed as yet.

Re:Guess LIGO failed too many times (1)

Stridar (325860) | more than 5 years ago | (#29434303)

That's correct. Lack of evidence isn't enough to disprove a theory; what you need is evidence that directly contradicts the theory.

We are approaching the point where the lack of evidence becomes evidence of non-existance. But as of yet, I know of no alternative theory.

Re:Guess LIGO failed too many times (0)

Anonymous Coward | more than 5 years ago | (#29432943)

Gravitational waves have been confirmed in other ways. Not sure if the observations were done incorrectly or if the theory is wrong? Get a more sensitive instrument. Or at least a theory that explains the previous observations that seem to confirm gravitational wave while also predicting the failure to detect them in another way.

Re:Guess LIGO failed too many times (0)

Anonymous Coward | more than 5 years ago | (#29433223)

was poppers idea of falsification falsifiable..?

well actually it doesn't seem to be if you think about it.

i would say that for an idea to have any usefulness in terms of science, it ought to be able to stand up to itself.

Re:Guess LIGO failed too many times (3, Informative)

mbone (558574) | more than 5 years ago | (#29433235)

LIGO and Pulsars set limits (or could detect) gravitational waves in very different parts of their frequency spectra - periods of milli seconds versus periods of months. The sources are different, the detection physics is different, etc. It's certainly worth trying both.

Also, none of the existing detectors are good enough that you can say for certain that there are known or likely astrophysical sources bright enough that they should see them. You can't talk about falsifiability until you cross that threshold, which I would expect to see happen in a decade or so.

I don't get it. (0, Troll)

XPeter (1429763) | more than 5 years ago | (#29432465)

We spend billions on observatories, but what's the point? I understand taking an in-depth look at our galaxy, but this is ridiculous. We should concentrate on landing on mars and other planets in our solar system, then concentrate on other things.

Re:I don't get it. (4, Insightful)

A beautiful mind (821714) | more than 5 years ago | (#29432575)

A human landing on mars gives us pretty pictures and a bunch of cozy, warm feelings.

Understanding fundamental physics (and mathematics) gave us the computer age along with keeping Moore's "law" working for the past 40 years. What did physics ever give to you? Pretty much every major engineering invention since 1950 depends on it in some way or other.

Re:I don't get it. (1)

Foobar of Borg (690622) | more than 5 years ago | (#29434105)

Understanding fundamental physics (and mathematics) gave us the computer age along with keeping Moore's "law" working for the past 40 years. What did physics ever give to you? Pretty much every major engineering invention since 1950 depends on it in some way or other.

The sad thing is that I've met plenty of computer geeks who basically say that physics is useless. They then go back to their beloved computers without realizing the tragic irony of what they just said. That's the pathetic thing about computer "science" majors. They think they know everything because they know how to fuck around with a computer, but they are too stupid to realize that they don't know usually what they are talking about.

Re:I don't get it. (4, Interesting)

icebike (68054) | more than 5 years ago | (#29432579)

> We spend billions on observatories, but what's the point?

Calm down. There is a depression going on.

All that money enters the economy employing everyone from astronomer to shoe-shine guys. In the mean time some science gets done.

If your tag line is to be believed, you will forgive us if we wait till you are actually OUT of your mom's basement before we task you with prioritizing our national science budget.

Re:I don't get it. (-1, Flamebait)

XPeter (1429763) | more than 5 years ago | (#29432627)

> >Calm down. There is a depression going on.

.

Exactly. So, why should we be spending money that we don't have?

Finding gravitational waves isn't going to help 99.99% of the population.

Re:I don't get it. (4, Insightful)

Gerafix (1028986) | more than 5 years ago | (#29432833)

Since when does everything science accomplish have to have immediate material benefit to humanity? Science is the advancement of Homo sapien knowledge about the universe. If you're going to complain about spending money complain about throwing trillions of dollars at the people who brought down the economy. Some people need to grow up.

Re:I don't get it. (3, Insightful)

mcpkaaos (449561) | more than 5 years ago | (#29433165)

He's 15 years old. It's much easier for him to understand and critique something that has been summed up than to spend the time and critical thought necessary to understand our present economy. Let's give the little bastard^Wwhippersnapper a break, he's trying.

Re:I don't get it. (1)

jfengel (409917) | more than 5 years ago | (#29433693)

> Since when does everything science accomplish have to have immediate material benefit to humanity?

To play devil's advocate... it's not so much a matter of "what science accomplishes" as "who pays for it". One is entitled to some sort of opinion when one is paying for it, via tax dollars.

It is, as you point out, shortsighted to assume that all science must have an immediate benefit to be worth it. But it is worth considering whether money spent on basic research might be better spent elsewhere.

(Personally, I'd rather spend a lot more on basic research, but those who want to pay less for it are entitled to an opinion when it's their money.)

Re:I don't get it. (1)

poopdeville (841677) | more than 5 years ago | (#29433749)

Gravitational waves are basic research. You don't get much more basic than wave propagation of a fundamental force.

Re:I don't get it. (1)

TheBilgeRat (1629569) | more than 5 years ago | (#29433011)

Umm...actually finding gravitational waves would help 100% of the population. That, and the weight of gravitrons. I'd like the theory holding me to the ground to become a law sometime-not too keen on drifting out of the atmosphere on a whim of disbelief...

Re:I don't get it. (1)

TropicalCoder (898500) | more than 5 years ago | (#29434411)

"Umm...actually finding gravitational waves would help 100% of the population."

Finding gravity waves is the key to finding anti-gravity waves. You see, every particle has its anti-particle. The are electrons and positrons. The are protons and anti-protons. There are top quarks and there are bottom quarks. There are charming quarks and there are boring quarks. There are gluons and anti-gluons. Just imagine what a beam of these would do to your enemy. Leaves nothing but quarks flying in all directions! Not a pretty sight. There is the w-boson, also called the "God particle" and its opposite - the "Atheist particle." Then finally there are gravitons and there are anti-gravitons. Anti-gravitons are the basis of your common tractor beam. I hope you found this discussion illuminating.

Re:I don't get it. (0)

Anonymous Coward | more than 5 years ago | (#29433023)

"Finding gravitational waves isn't going to help 99.99% of the population."
"I think there is a world market for maybe five computers."

Pray stop making bald statements which you are insufficiently experienced to understand the implications of. Or, in simpler words, shut up and let your betters talk.

Re:I don't get it. (5, Insightful)

Fluffeh (1273756) | more than 5 years ago | (#29433227)

Exactly. So, why should we be spending money that we don't have?

Finding gravitational waves isn't going to help 99.99% of the population.

How about you look at this this way instead:

There is a lot of money going around to try to help a flailing economy. Why should that money go ONLY to those who have been bad at their business? Automakers that don't make the right cars? Banks that don't have solid lending strategies? Why NOT give some of that money that's all going to the same economy to scientists who quietly go about their business and get things done?

Re:I don't get it. (1)

icebike (68054) | more than 5 years ago | (#29433319)

> Exactly. So, why should we be spending money that we don't have?

Because you can not frugally "save" your way out of a depression. That simply leads to a deeper depression.

Its cheaper to build these things (as well as other infrastructure) in a down economy than wait till everyone if fully employed and demanding big salaries.

Re:I don't get it. (1)

4D6963 (933028) | more than 5 years ago | (#29434961)

I know it's counter intuitive, and back when I was about your age (that's right, I'm patronising you. Feels good man.) I myself didn't get it, but basic science (the kind that seems like useless theoretical dicking around like that gravitational waves thing) is a sort of long term investment, and a great kind of investment, as you can get several times your investment back.

Think about it, what good was nuclear research in the 19th century? Yet a few decades later they probably kept us safe from an all out war against USSR, they power clean power plants, submarines, aircraft carriers, cruisers, destroyers and space probes. The research on quantum physics keeps on giving more and more, mostly as we manufacture things that keep getting smaller, like computer chips. We wouldn't have GPS if it wasn't for Einstein's relativity, and I let you guess what good did research that made transistors was good for. If you look into any technology and progress you'll find that at its root is basic research that wasn't obviously going to give that. Who would have thought that research in chemistry and fluid physics would get us to the moon?

So what do you know, maybe when you'll be older you'll owe your flying car to current research on gravitational waves.

Also, look at it this way. If we only did applied research to find things with direct applications, we wouldn't have gotten far. A good analogy is, if explorers had always only sailed within sight of a coast, we would have never discovered the Americas.

Re:I don't get it. (0)

Anonymous Coward | more than 5 years ago | (#29432581)

Who modded this overrated? The OP has a valid point, are the mods on their periods?

Re:I don't get it. (1)

Gerafix (1028986) | more than 5 years ago | (#29432683)

No it isn't, you fool. There's no Grand Scientist Bureaucracy where they dole out what every scientist is going to work on. There are many different fields and many different scientists who would like to work on many different things. Damn false dichotomies with you people, get a grip on reality for IPU sake.

If we learn about gravity.... (1)

NoYob (1630681) | more than 5 years ago | (#29432679)

maybe we can create artificial gravity like in the movies without having to have big centrifuges built into the hulls.

Re:I don't get it. (1)

John Hasler (414242) | more than 5 years ago | (#29433665)

> We spend billions on observatories, but what's the point?

To learn.

> I understand taking an in-depth look at our galaxy, but this is ridiculous.

Why?

> We should concentrate on landing on mars...

Well, then you and your colleagues[1] should concentrate away. Meanwhile, these people choose to concentrate on something else.

[1] I assume you have colleagues: why else do you write "we"?

Usefulness (2, Funny)

JustNiz (692889) | more than 5 years ago | (#29432507)

>>> "Gravitational waves squash and stretch space as they travel through the universe

Gravitational waves are very useful in the kitchen. I use them for juicing oranges.

Re:Usefulness (3, Insightful)

A beautiful mind (821714) | more than 5 years ago | (#29432859)

Detecting or not detecting gravitational waves validates* or invalidates part of Einstein's theory of general relativity. That's a pretty big deal. It means that we have found the first flaw in a theory whitstanding constant attacks on it since 1915 if we would not find gravitational waves.

*take "validates" in this context to mean that there is no experiment or information in disagreement with the theory, therefor going by science's falsification requirement, science considers the theory to be currently valid.

Re:Usefulness (1)

TheRealMindChild (743925) | more than 5 years ago | (#29434273)

Every time someone finds something that Einstein "may have gotten wrong", we just end up with more evidence that he was right.

Personally, I don't believe in something like gravitational waves, but I'm more inclined to trust his intelligence more than mine.

Re:Usefulness (1)

4D6963 (933028) | more than 5 years ago | (#29434977)

I feel the same way, you can bet your money on Einstein every time, but we have to test anything we can anyway to verify everything and hope to learn more.

Re:Usefulness (0)

Anonymous Coward | more than 5 years ago | (#29434765)

It is indeed interesting that we have yet to find evidence of gravitational waves at the same time as we have no perfect explanation for the Pioneer anomaly and the Flyby anomaly. For example, could it be that the real space-time has more properties than those that are described in General Relativity, or would that be impossible?

Re:Usefulness (1)

TheRealMindChild (743925) | more than 5 years ago | (#29434799)

Or... there is a mass we don't know is there. The universe tends to be a lot simpler than we try to make it.

Re:Usefulness (1)

MillionthMonkey (240664) | more than 5 years ago | (#29433911)

I use them to make binary neutron stars swirl into each other and explode. They remove energy from the system so you can pack those stars in there real good... and rapidly spinning black holes make great gifts for the kids.

Is thisntest desing in such away (1)

geekoid (135745) | more than 5 years ago | (#29432531)

that is could falsify the theory? if so then go for it.

I mean, they don't have to exist, there are other theories out there.

Re:Is thisntest desing in such away (1, Insightful)

BJ_Covert_Action (1499847) | more than 5 years ago | (#29432739)

Is thisntest desing in such away

Is your title designed in such a way that could falsify your hopes of being taken seriously?

....

Yes.

Re:Is thisntest desing in such away (2, Funny)

rts008 (812749) | more than 5 years ago | (#29432905)

Is thisntest desing in such away that is could falsify the theory?

What language is this written in?
What does it translate to in English?

Gravity waves distort time (0)

Anonymous Coward | more than 5 years ago | (#29432543)

Physics tells us that gravity waves distort time. So, instead of setting up a billion dollar array of telescopes over several square kilometers to monitor this, why not set up an array of clocks with real time feed into a central computer that would record any temporal fluctuations?

Re:Gravity waves distort time (1)

poopdeville (841677) | more than 5 years ago | (#29433789)

they did. telescopes are clocks. Radiotelescopes are extremely high temporal resolution clocks.

A complementary approach (4, Interesting)

beanyk (230597) | more than 5 years ago | (#29432569)

Just wanted to point out that the pulsar timing array approach will cover a completely different frequency range (~ 10^-9 to 10^-7 Hz) to existing ground-based detectors (LIGO, Virgo and friends), which operate in the 10^1 to 10^4 Hz range. In between are projects like LISA (http://lisa.jpl.nasa.gov/).

The different frequency ranges mean different astrophysical sources of gravitational waves; generally speaking, the more massive the system, the lower the GW frequency. LISA, for instance, would see the radiation produced by the supermassive black holes at the centres of galaxies, while the other detectors would be targetting much smaller systems.

Re:A complementary approach (3, Interesting)

TropicalCoder (898500) | more than 5 years ago | (#29432813)

Thank you for your interpretation of the meaning behind today's article. It was a revelation for me to consider gravity waves as an analogue of electromagnetic waves. On the The North American Nanohertz Observatory for Gravitational Waves web site [arxiv.org] there is more information. They say "The timing precision of today's best measured pulsars is less than 100 ns. With improved instrumentation and signal-to-noise it is widely believed that the next decade could see a pulsar timing network of 100 pulsars each with better than 100 ns timing precision." I thought it interesting that they only get 100. Then if you did a long term integration of these signals, you may get down to pico-second timing. Such a timing base may be used to correct atomic clocks in GPS satellites and have many other uses. This is all just pure speculation by a non-physicist, so take it with a grain of salt.

Re:A complementary approach (1)

Rakshasa Taisab (244699) | more than 5 years ago | (#29433993)

And what do you do when the pulsar star has the 'glitch' in its rotational speed, caused by what ever it is... adjustment of the crust, startquakes, or what the theory of the month is.

Not a very good clock, now is it. ^_^

Well I never thought of that - n/t (1)

TropicalCoder (898500) | more than 5 years ago | (#29434047)

This space intentionally left blank.

Re:A complementary approach (5, Informative)

Scott Ransom (6419) | more than 5 years ago | (#29434879)

The good thing is that the pulsars which glitch are the young ones (hundreds to millions of years old). The pulsars that we are using for NANOGrav are millisecond pulsars which are hundreds of millions or billions of years old, have much smaller magnetic fields than young pulsars, and basically never glitch. They are extremely stable rotators -- much better than normal pulsars.

Re:A complementary approach (3, Interesting)

electrostatic (1185487) | more than 5 years ago | (#29433265)

If the pulsars under observation are, say, 100-1000 light years apart, then the time necessary to notice a gravitational wave perturbation would seem to be on the order of 100-1000 years, respectively.

IOW, because gravitational waves travel at light speed (general theory of relativity), then a "stretch and squeeze" at one pulsar would reach the more distant pulsar many years later. The observed delay is of course a function of the distance between the pulsars, the angle of the wave and the angle of them to earth.

OTOH, a gravitational wave train with a wavelength much shorter the the distance between the pulsars could also be observed if a lot of pulsars were involved -- and if the observation period was at least one cycle. The 10^-9 frequency mentioned equates to a 31.7 year period.

Galaxy envy? (3, Funny)

davidwr (791652) | more than 5 years ago | (#29432595)

Will beings in larger galaxies taunt us because their gravity-wave detectors are bigger than ours?

Re:Galaxy envy? (1)

eviloverlordx (99809) | more than 5 years ago | (#29433055)

I guess size really does matter.

This is /. (0, Flamebait)

Sybert42 (1309493) | more than 5 years ago | (#29432649)

We are virgin males who are into Computer Science. We are not into astronomy.

Re:This is /. (0)

Anonymous Coward | more than 5 years ago | (#29432851)

You are marked as flamebait but I was seriously wondering why is it that everytime some story like this appears on /. there are a bunch of people going "waste of money! what's the point?"

Perhaps them being the oompa loompas of science explains it.

So what happens (1)

Xaedalus (1192463) | more than 5 years ago | (#29432705)

If there are no gravitational waves to be found? If we search the entire spectrum, and we don't find any, then I assume that falsifies the grav-wave theory (and the entire Honorverse). At that point, what is the next step/theory? In a related note, does gravity pull, or push? I think I remember reading somewhere that Einstein said gravity pushed, rather than pulled.

Re:So what happens (2, Interesting)

Ralph Spoilsport (673134) | more than 5 years ago | (#29432841)

I think that is an excellent question. It's the classic divide between Einstein and Bohr. For Einstein, gravity is geometric, for Bohr et al, it is a product of Stuff and Stuff exists as particles, waves, and/or both.

If they don't find gravity waves in this attempt, I would suspect the following to happen:

A: One bunch, the Einsteins of the lot will say "Well, I toldja so..."

B: The Quantum types will simple demand more money for an even bigger test that will look at clusters of Galaxies or some such conglomeration of Stuff.

When that test fails, go back to step A. Rinse. Repeat.

RS

Re:So what happens (1)

amRadioHed (463061) | more than 5 years ago | (#29433005)

I don't think Einstein said that gravity pushed or pulled, it just warped space-time.

Re:So what happens (1)

Xaedalus (1192463) | more than 5 years ago | (#29433661)

But gravity is a force. As a force - does it push, or pull? We know that it exerts a force over matter... but what are the implications if it pushes rather than pulls?

Re:So what happens (1)

Bottlemaster (449635) | more than 5 years ago | (#29434499)

What are the implications of and differences between forces which push and forces which pull? Nonetheless, the question doesn't apply to gravity because, as the GP said, gravity isn't a force.

Re:So what happens (0)

Anonymous Coward | more than 5 years ago | (#29434873)

Whether gravity pushes something down or pulls it down, it's still applying a downward force and accelerating it downward. What do you mean by push and pull, anyway? Normally, you push something away, or pull it towards you, so by that definition, gravity always pulls.

However, both of those definitions are simply based on which way something is moving. Are you using some definition of push and pull where there's a major difference in what sort of force you're applying?

Not interested, sorry (0)

Monkeedude1212 (1560403) | more than 5 years ago | (#29432789)

I'm Christian.

Trolling aside -

How does this actually function like an observatory? Aren't our observatories capable of looking at stars and such... aren't these just like... a bunch of satellites floating out past earth tracking "Gravity"?
I clearly don't understand how pulsars work.

Re:Not interested, sorry (0)

Anonymous Coward | more than 5 years ago | (#29433251)

carefully read the article. Then go read up about the parts you dont understand. Theres nothing magical to see here ( sorry ).

Galaxy-sized observatory? (0)

Anonymous Coward | more than 5 years ago | (#29432803)

Wait, by this definition, wouldn't every observatory ever built qualify as 'galaxy-sized'?

Re:Galaxy-sized observatory? (1)

hansraj (458504) | more than 5 years ago | (#29432919)

If every observatory ever built were using a galaxy as a sort of measuring instrument, then yeah. What's your point?

Re:Galaxy-sized observatory? (1)

Monkeedude1212 (1560403) | more than 5 years ago | (#29432973)

Thats what I don't understand - how do you use the galaxy as a measuring instrument?

Re:Galaxy-sized observatory? (1)

Sebilrazen (870600) | more than 5 years ago | (#29433201)

Pulsars are your measuring instruments. They feed back their measurements as a periodic electromagnetic signal. Since the period, per pulsar, is standard any deviation could indicate a measurement to be researched. Pulsars are distributed roughly equally throughout the galaxy, so in theory we can use the entire galaxy as our observatory.

Disclaimer: not an astrophysicist, I could be entirely wrong.

And yet we spend only 1.6 million on tracking NEOs (0, Troll)

Absolut187 (816431) | more than 5 years ago | (#29432969)

http://arstechnica.com/science/news/2009/08/nasa-asteroid-tracking-program-stalled-due-to-lack-of-funds.ars [arstechnica.com]

1.6 million for tracking NEOs that could cause global extinction.

66 million to look for "gravity waves" that may or may not exist.

Smart.

Re:And yet we spend only 1.6 million on tracking N (1)

Chris Burke (6130) | more than 5 years ago | (#29433109)

I agree that we should be funding the tracking of NEOs more, but remember that the money for these two projects isn't coming from the same pool. One is a NASA sub-project, the other is an international project conducted by a variety of observatories and funded by a variety of organizations. So it's not as simple as "do this instead of that".

That's a little presumptuous. (2, Insightful)

mosb1000 (710161) | more than 5 years ago | (#29432993)

"Gravitational waves squash and stretch space as they travel through the universe."

Does anyone else find these words to be a little presumptuous. It's not like they've ever detected any. Might I suggest the following wording instead:

"Gravitational waves would squash and stretch space as they travel through space, if they exist"

Re:That's a little presumptuous. (3, Insightful)

nstlgc (945418) | more than 5 years ago | (#29433243)

Technically speaking, no. They squash and stretch space by definition. If they don't exist, space obviously won't be squashed and stretched by them, but that won't change their definition. They just won't exist. It's like saying "a unicorn has wings". The fact that it allegedly doesn't exist doesn't mean it doesn't have wings when someone draws one.

Re:That's a little presumptuous. (1)

mosb1000 (710161) | more than 5 years ago | (#29433527)

No, the article is making a claim about space, which is real. It would be like me saying "Unicorns are eating my lawn," which is obviously not true. What I should say is "Unicorns might eat my lawn, if they exist."

Huh?!? WTF?!? OMG!?! PINK PONIES?!? (0, Offtopic)

gbutler69 (910166) | more than 5 years ago | (#29433687)

You FAIL! Unicorns don't have WINGS!!!!!

They have HUGE PENISES!

Re:That's a little presumptuous. (1)

poopdeville (841677) | more than 5 years ago | (#29433841)

If gravitational waves exist, they are nothing but the wave-like propagation of the gravitational force. We already know the gravitational force exists, and warps space-time.

Galaxy size observatory (0)

Anonymous Coward | more than 5 years ago | (#29433027)

NASA used to have a telescope aboard a C141 starlifter. I guess you could have a bigger flying telescope aboard a C5 Galaxy.

Say wasn't the Enterprise D a Galaxy class starship ?

This would be wonderful (0)

NoYob (1630681) | more than 5 years ago | (#29433061)

I would love to know how fast gravity waves travel. I wonder if they travel faster than light - I know, 300,000 km/s is the Universal speed limit according to Einstein, but...? . If a black hole can keep light from escaping, that means the speed of light isn't escape velocity, and that means that gravity is getting to it faster than the speed of light?

Re:This would be wonderful (0)

Monkeedude1212 (1560403) | more than 5 years ago | (#29433191)

No. It means the Gravity is so strong that the "force" pulling the light inwards is stronger then whatever force propels light at 300000 km/s. If you imagine space time like a blanket, and gravity from a planet like a tennis ball on the blanket, the curvature thats created in the blanket is like the effect of gravity. Thus if you propel an item along the curve, it will orbit around that tennis ball.

A black hole has been theorized to be a pea on that blanket that is so heavy that the "curve" created in space time is almost vertical or even somehow surpasses vertical - thus not letting light escape. There is a point at which light CAN escape from a black hole, a certain distance away (the horizon as they call it) - which is the point at which the force of Gravity and Light are equal and light is basically trapped there.

However, the strength of Gravity has nothing to do with its SPEED. It's speed is how fast it effects the objects around it. As in, Einstein theorized that it travels at the same speed of light, so we are orbitting around the sun, being pulled in by a force that originated 8 or so minutes before it affected Earth.

Meaning if the sun were to instantaneously disappear - we would orbit in our same path until we no longer saw any light. At least thats the theory. However Gravity could be faster, or slower, there isn't really anything concrete to suggest anything Einstein said was really right.

Re:This would be wonderful (1)

DarrenBaker (322210) | more than 5 years ago | (#29433321)

The speed of light is actually the speed of energy, so if gravity waves are energy, then it will be at or slightly below the speed of light. Otherwise, if it's matter-based, then its maximum speed would be about the speed of sound. I believe.

Re:This would be wonderful (0)

Anonymous Coward | more than 5 years ago | (#29433689)

Otherwise, if it's matter-based, then its maximum speed would be about the speed of sound.

*WOOOSH*

Re:This would be wonderful (0)

Anonymous Coward | more than 5 years ago | (#29434949)

The speed of sound in vacuum? WTF! Gravity waves can travel in a vacuum, therefore they must be non-material.

Re:This would be wonderful (0)

Anonymous Coward | more than 5 years ago | (#29434973)

Uh, no, it is a limit that represents the resistence of movement through spacetime continnum. In other words, its a measurement of viscosity of the sapcetime foam.

Re:This would be wonderful (1)

John Hasler (414242) | more than 5 years ago | (#29433395)

> I would love to know how fast gravity waves travel.

At the speed of light.

> If a black hole can keep light from escaping, that means the speed of light
> isn't escape velocity, and that means that gravity is getting to it faster
> than the speed of light?

Gravitational radiation does not come from inside a black hole any more than electromagnetic radiation comes from inside an electron.

Re:This would be wonderful (4, Informative)

Anti_Climax (447121) | more than 5 years ago | (#29433621)

I seem to recall an experimental observation in the last few years involving Jupiter, through which they verified with about 90% certainty that the speed at which gravity propagates through space/time is equal to the speed of light.

A little googling turned this up:
http://www.nrao.edu/pr/2003/gravity/index-p.shtml [nrao.edu]

Any armchair physicists here? (1)

DarrenBaker (322210) | more than 5 years ago | (#29433299)

So, stop me if I'm way off base, but might it be impossible to detect gravity waves? If a gravity wave is a change in the gravitational constant of a finite space, then wouldn't that affect the mass, and the space-time qualities of a sensor within that space, rendering its observations relative, and useless?

Or does my thought experiment lack a certain... Knowledge?

Thanks!

Re:Any armchair physicists here? (0)

Anonymous Coward | more than 5 years ago | (#29433539)

If a gravity wave is a change in the gravitational constant of a finite space, then wouldn't that affect the mass, and the space-time qualities of a sensor within that space, rendering its observations relative, and useless?

Possibly. But if the sensor is not within that space where the wave passes, then it could be detected. Alternatively, if the sensor resides in, but detects something that is not within that space, it could work, too, if these waves exist.

By "space" I don't mean the general term of space, but rather vicinity, of course.

Re:Any armchair physicists here? (3, Informative)

superluminique (1567063) | more than 5 years ago | (#29433997)

DarrenBaker, a gravity wave is not a change in the gravitational constant; it is a deformation of the space-time fabric itself. So it doesn't change the gravitational (attractive) force between masses but simply moves the "fabric" on which they lie.

Imagine a stretchy, rubber fabric that you pull/push or move upward/downward from one side such that a wave propagates through. Then two masses lying on this fabric, link ping pong balls that you would stick on, would move closer/further apart. That's basically the effect that people are trying to measure. Of course, if these "test" objects are perfect in such that they're infinitely small, everything behaves in a trivial way. The catch is when your object is not "perfect" anymore and possesses some finite size. This seems to be concept that you worry about and you are right. Because of it's finite size, the object itself would change size. However, it does not matter at all because this change is not significant. Here's why:

The amplitude of a gravity wave is express in a weird unit expressing the ratio of the spatial compression in one direction to the stretching in the orthogonal direction (see the nice animation here [wikipedia.org] ). A typical gravity wave would have an amplitude of 10^-20., which basically mean that any object would change size by this fraction. So this is practically undetectable unless you consider something really big like the "arms" of the LIGO gravity wave detectors [caltech.edu] or this pulsar timing array. The other thing to take into account is the fact that what you are trying to detect acts like a wave. Waves that this pulsar array is after have frequencies of nanohertz, or wavelengths of 3*10^17 meters (this is about 32 light-year!). For LIGO, frequencies are the order of 1 hertz, so 300 000 km. Hence if your object, the pulsar for the pulsar array, or the mirror/detector for LIGO is much smaller that the wavelength that you attempt to detect, it really doesn't have any effect on what you are trying to measure.

Re:Any armchair physicists here? (1)

John Hasler (414242) | more than 5 years ago | (#29433711)

> So, stop me if I'm way off base, but might it be impossible to detect gravity
> waves?

Proving that they cannot be detected would be exactly the same as proving that they do not exist.

Re:Any armchair physicists here? (4, Informative)

Anti_Climax (447121) | more than 5 years ago | (#29433781)

A gravity wave, as derived from the theory of relativity, doesn't specify that the gravitational constant would oscillate - simply that the shifting of large masses, like co-orbital black holes and such, will distort spacetime in wavelike manner. Those perturbations of spacetime would travel from their origin outward at the speed of light.

It's best to think of it in terms of the bowling-ball-on-a-rubber-sheet analogy of space-time. If you take a large mass like a bowling ball and set it in the middle of a large rubber sheet, it will depress deeply nearby and taper off the further away from it you go on that sheet. If that bowling ball magically disappeared, there would be a wave that travelled across that sheet as well as if you had 2 bowling balls spinning around each other.

The way we've been trying to detect gravity waves so far (LIGO) uses lasers set up at right angles so if space were to compress or stretch in one dimension, the beams the were previously in phase would shift apart. This can detect a stretching of spacetime equal to a fraction of the wavelength of light used in the lasers.

In actuality, it is the change in the behavior of spacetime that lets us measure in that manner, but if the wave were to stretch spacetime in all dimensions, LIGO couldn't work. Hope that explains it.

Re:Any armchair physicists here? (1)

Migraineman (632203) | more than 5 years ago | (#29434855)

You, I, and the lasers are inside the three-space being acted upon by the gravitational wave. How the hell are we supposed to measure this phenomenon from the "inside?"

Re:Any armchair physicists here? (1)

mbone (558574) | more than 5 years ago | (#29434145)

A gravity wave will change the distance to objects at right angles to its direction of propagation. This effect is biggest when the distance to an object is order the wavelength of the wave, or longer. (Since they travel at the speed of light, the relation between wavelength and frequency is the same as for light.) Likewise, the sensitivity is biggest when the period of the wave is between the frequency of measurement and the total duration of observations. So, pulsars are sensitive to waves with periods between about a day (they are not observed continuously) and some decades (the length of data).

Some waves are sinusoidal (distant objects appear to move closer and further away periodically), while impulsive gravitational radiation can have "memory" - i.e., the distance after the burst goes by will be permanently changed.

All of the above assumes we know the correct theory of gravity, which we won't be sure about until we actually get to study them.

Gravitational Waves Exist (1)

rotenberry (3487) | more than 5 years ago | (#29434241)

I believe that any theory of gravity where

1. Energy is conserved

2. Gravitational information propagates at a finite speed (most theories set this speed equal to the speed of light)

will have gravitational waves of some sort.

Is there any physicist who does not believe in both 1 and 2?

Gravitational waves exit. The real problem is detecting them and interpreting the waveforms.

Re:Gravitational Waves Exist (1)

mbone (558574) | more than 5 years ago | (#29434595)

The really interesting thing is that General Relativity predicts two and only two polarizations, while other theories (that cannot be distinguished from G.R. in the usual solar system tests) have more polarizations. If and when we get a good, high SNR, detection of gravitational radiation, a profound test of gravity should follow in short order.

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