Beta

Slashdot: News for Nerds

×

Welcome to the Slashdot Beta site -- learn more here. Use the link in the footer or click here to return to the Classic version of Slashdot.

Thank you!

Before you choose to head back to the Classic look of the site, we'd appreciate it if you share your thoughts on the Beta; your feedback is what drives our ongoing development.

Beta is different and we value you taking the time to try it out. Please take a look at the changes we've made in Beta and  learn more about it. Thanks for reading, and for making the site better!

Biggest Detector To Look For Gravitational Waves

kdawson posted more than 4 years ago | from the mission-of-gravity dept.

Space 109

Hugh Pickens sends in coverage in the Telegraph of a joint NASA-ESA experimental mission, to launch around 2020. It involves three spacecraft orbiting the Sun, separated by 3 million miles, each with a payload of two lasers and a 4.6-cm cube of gold-platinum alloy. The point of it all is to look for gravitational waves. The mission is called LISA, a reasonably non-strained acronym for Laser Interferometer Space Antenna. The Telegraph makes a point of LISA being the largest experiment ever constructed (in terms of its dimensions). Neither that newspaper nor the project page at NASA mentions how much the experiment will cost, but it's almost certainly an order of magnitude or more above the $66 million estimated for a gravitational wave detector the size of the galaxy, which we discussed last fall.

cancel ×

109 comments

Dimensional challenges (4, Funny)

SimonInOz (579741) | more than 4 years ago | (#32163436)

I read that as a 4.6m cube of gold/platinum alloy and was thinking that was just the sort of thing Lex Luthor would want to steal.

Now come on, it'd make a great show ...

Re:Dimensional challenges (1)

GNUALMAFUERTE (697061) | more than 4 years ago | (#32165138)

I don't think so.

Lex looks more like the kind of guy that would take forty cakes. He would take 40 cakes. That would be as many as four tens. And that would be terrible.

Re:Dimensional challenges (0)

Anonymous Coward | more than 4 years ago | (#32168124)

I still have the pic in my /b/ folder.

Re:Dimensional challenges (1)

MartinSchou (1360093) | more than 4 years ago | (#32165364)

Sure ... except it's a 4.6 centimeter cube, not a 4.6 meter cube. Not worth stealing if you're Lex Luthor

Re:Dimensional challenges (0)

Anonymous Coward | more than 4 years ago | (#32166070)

Hence the "I read that as..."

Re:Dimensional challenges (0)

Anonymous Coward | more than 4 years ago | (#32167018)

Not very unexpected that a user on the internets would misinterpret a post only to get a reason to bark.

Lousy Democrats (5, Funny)

BitHive (578094) | more than 4 years ago | (#32163454)

Shooting all our remaining gold into space so they can shine lasers at it. Typical.

Re:Lousy Democrats (1)

masterwit (1800118) | more than 4 years ago | (#32163476)

Cash4Gold is going to make a killing!

I knew those wise investors had it right all along...

Re:Lousy Democrats (1)

BraksDad (963908) | more than 4 years ago | (#32164978)

This would ensure we could all see our gold glittering across the night sky. Puts a new meaning to stars wearing jewelry.

Dang Demmycrats (0)

Anonymous Coward | more than 4 years ago | (#32165140)

Shootin' all our remaining gold inta space so they can done shine them laseeebeams at it. Dagnammit!

FTFY.

Re:Dang Demmycrats (1)

Garridan (597129) | more than 4 years ago | (#32165526)

FTFY'all.

FTFY'all.

Re:Lousy Democrats (1)

Garridan (597129) | more than 4 years ago | (#32165520)

Don't worry, our currency isn't based on our gold stores anymore. Didn't Ron Paul teach you people anything?

OTOH, 2 kg of gold is worth about $77k. Price of a similar amount of lead? Less than $5. Oh... you don't want it to react to the atmosphere (um... in space)? Plate it in gold, or better yet, cover it in enamel for $5 more. Makes you wonder how they spend the rest of the billions of dollars, doesn't it? I whole-heartedly support our space program, but this just pisses me off.

Re:Lousy Democrats (4, Interesting)

jandoedel (1149947) | more than 4 years ago | (#32166484)

it's only the thin coating surrounding the mass that is made of a gold/platinum alloy, not the entire cube. So it is NOT 2kg of gold...
actually gold coatings are used quite a lot for these things.

They have a mass floating freely in space, and surrounding it is this gold/platinum coat, that never touches it, it just flies around it and has microthrusters to keep it away from the central mass. This gold/platinum coat is shielding the mass from some external influences, like the solar magnetic field, so that the central mass only feels the influence of the gravitational waves.

Unlike the "Galaxy sized detector" (5, Insightful)

TwineLogic (1679802) | more than 4 years ago | (#32163498)

This detector would be 3,000,000 miles across when measured from one man-made component to another. The article linked to as a 'galaxy sized detector' is actually about a proposal to observe pulsars looking for the effect of gravitational waves.

When observing pulsars, I assume it is not possible to be 100% of what one is seeing, considering that pulsar observations continue to accumulate and scientists have not had the chance to see a pulsar close-up.

In comparison, using man-made scientific instruments, which are much more under the control of the investigating scientists, to perform the measurement is more trustworthy than observing pulsars. In this regard, the huge scale of the equipment (3 Million Miles) is very significant -- the instruments will be able to make a fine measurement across this distance -- and comparing it with the size of the galaxy is not really a valid comparison.

On the other hand, the snark-value of the comparison was high, and providing the link without these details only raised the snark-tasticness.

Re:Unlike the "Galaxy sized detector" (1)

craklyn (1533019) | more than 4 years ago | (#32164006)

It's pretty disingenuous to link the cost of a detector to its size, as though size indicates scientific merit.

But maybe I'm just bias because I have studied atoms (0.5x10^-10 meter scale) on a graduate student stipend ($20k per year). This cost my university a measly $400,000,000,000,000 per meter per year.

Re:Unlike the "Galaxy sized detector" (3, Informative)

Anonymous Coward | more than 4 years ago | (#32164366)

...the huge scale of the equipment (3 Million Miles) is very significant -- the instruments will be able to make a fine measurement across this distance -- and comparing it with the size of the galaxy is not really a valid comparison.

It's a valid comparison because, when you're using pulsars to detect gravitational waves, the effective size of your detector is the distance from one pulsar to another, which is (some large fraction of) the size of the galaxy. Okay, pulsars aren't man-made - but if we deliberately set out to make the transmitter component of a galaxy-sized gravitational-wave detector, we wouldn't be able to produce anything nearly as suited for the task as they are. They keep time as well as our best clocks, and are trillions of times as powerful as any radio transmitter we could build (and they need to be, if we want to see them at these distances).

The snarkiness is entirely justified, I think, as a response to the Telegraph's claim that LISA is the largest gravitational wave detector, when it's not. This doesn't mean that it isn't useful, though. LISA and pulsar observations are sensitive to gravitational waves of different frequencies - about 10^-1 and 10^-9 Hz respectively - so they're complementary techniques in the same way that (say) optical and radio astronomy are.

Re:Unlike the "Galaxy sized detector" (3, Insightful)

JakartaDean (834076) | more than 4 years ago | (#32165066)

It's a valid comparison because, when you're using pulsars to detect gravitational waves, the effective size of your detector is the distance from one pulsar to another, which is (some large fraction of) the size of the galaxy. Okay, pulsars aren't man-made - but if we deliberately set out to make the transmitter component of a galaxy-sized gravitational-wave detector, we wouldn't be able to produce anything nearly as suited for the task as they are. They keep time as well as our best clocks, and are trillions of times as powerful as any radio transmitter we could build (and they need to be, if we want to see them at these distances).

The snarkiness is entirely justified, I think, as a response to the Telegraph's claim that LISA is the largest gravitational wave detector, when it's not. This doesn't mean that it isn't useful, though. LISA and pulsar observations are sensitive to gravitational waves of different frequencies - about 10^-1 and 10^-9 Hz respectively - so they're complementary techniques in the same way that (say) optical and radio astronomy are.

Wikipedia http://en.wikipedia.org/wiki/Gravitational_wave [wikipedia.org] does a pretty good job of describing these things, with the bonus that it doesn't say anything about "proving" Einstein's theory of general relativity. The take-home point is how tiny these waves are. The predicted energy is enough to distort space by 10 ^-20. From the stupid wording in the Telegraph article, the satellites will be 5 million kilometres apart, and will be able to detect displacements of "40 millionths of a millionth of a metre." So, they can detect displacement of 40*10^-12 / 5*10^9 which I get as 8*10^-22, so good enough I guess. The scales are unimaginable to me, at both ends.

Re:Unlike the "Galaxy sized detector" (1)

wall0159 (881759) | more than 4 years ago | (#32166548)

"The scales are unimaginable to me, at both ends."

Yup -- doesn't maths rock? It allows our stupid ape-brains to grok deep truths! :-)

Re:Unlike the "Galaxy sized detector" (3, Informative)

L4t3r4lu5 (1216702) | more than 4 years ago | (#32167108)

Well, 5000000km is just under 4 x the diameter of the sun (1.4m km), and "40 millionths of a millionth of a metre" is as close to matter 1/333 the average thickness of a cell membrane (3nm).

Hope this clears things up for you :)

Re:Unlike the "Galaxy sized detector" (0)

Anonymous Coward | more than 4 years ago | (#32167774)

Sorry, could you post that in Football Fields, please?

Re:Unlike the "Galaxy sized detector" (1)

L4t3r4lu5 (1216702) | more than 4 years ago | (#32169380)

Sure! Respectively, 54500 football fields, and 0.000000000000002 football fields.

For an idea of how far the first one is, it would take Usain Bolt, at his 2008 Olympics speed of 34.5km/h (100m in 9.58s), it would take him 16 years 6 months to run that distance, a Bugatti Veyron going at top speed (409.7km/h) 1 year 3 months, and Voyager 1 (17km/s) 3.5 days :)

Re:Unlike the "Galaxy sized detector" (1)

Nautical Insanity (1190003) | more than 4 years ago | (#32164460)

3,000,000 miles across when measured from one man-made component to another.

The article linked to as a 'galaxy sized detector'

comparing it with the size of the galaxy is not really a valid comparison.

There has to be at least one good, snarky, yo' mama joke in there.

Re:Unlike the "Galaxy sized detector" (0)

Anonymous Coward | more than 4 years ago | (#32167372)

3,000,000 miles across when measured from one man-made component to another.

The article linked to as a 'galaxy sized detector'

comparing it with the size of the galaxy is not really a valid comparison.

There has to be at least one good, snarky, yo' mama joke in there.

How big across is your detector, Professor?

Tree millions ub miles, same as one o' yo mama's thighs, give or take a chikken wing.

Costing (5, Insightful)

kakapo (88299) | more than 4 years ago | (#32163522)

From memory, LISA is usually listed as being in the $1.5- $2 billion dollar range, which puts in the same category as Hubble or the forthcoming James Webb telescope.

Worth every penny, too, in my opinion.

Re:Costing (2, Informative)

ganv (881057) | more than 4 years ago | (#32169630)

Definitely worth every penny. Gravitation wave detection will bring a completely new window on the universe. Even the first radio telescopes or the first infrared telescopes only opened up a new part of the electromagnetic spectrum, and the space observatories have simply allowed higher resolution. Gravitational observatories will be the first to see an entirely new type of radiated energy. The sensitivity of LISA and the frequency band they can study allows them to detect common gravity wave sources...as opposed to ground based instruments which are only likely to detect rare events like black hole or neutron star mergers. Seems to me that if they can get the system working in space it is essentially certain to see gravity waves.

So I didn't RTFA (2, Interesting)

jasno (124830) | more than 4 years ago | (#32163538)

What happens if they don't find anything?

Do gravitational waves radiate energy? Have we seen instances, such as during a supernova, where there was missing energy which could be explained by them?

Re:So I didn't RTFA (1)

Xaedalus (1192463) | more than 4 years ago | (#32163638)

Along these lines, how would we know if we've discovered a wave? And what would distinguish a graviton wave from a ripple in space-time?

Re:So I didn't RTFA (2, Informative)

John Hasler (414242) | more than 4 years ago | (#32164286)

A gravitational wave is a "ripple in space-time".

Re:So I didn't RTFA (0)

Thinboy00 (1190815) | more than 4 years ago | (#32164646)

A gravitational wave is a "ripple in space-time".

...according to general relativity, which has not been reconciled with quantum mechanics yet.

Re:So I didn't RTFA (1)

Lotana (842533) | more than 4 years ago | (#32164770)

What does gravity has to do with quantum mechanics? I was under the impression that such ripples would be larger than the size required for quantum effects to occur.

Re:So I didn't RTFA (2, Informative)

MrZilla (682337) | more than 4 years ago | (#32166120)

What does gravity has to do with quantum mechanics?

Oh nothing at all. It's just one of the biggest unsolved problems in physics at the moment.

Re:So I didn't RTFA (1)

marcosdumay (620877) | more than 4 years ago | (#32168896)

Ok, they aren't conciliated. But quantum mechanics (QM) says nothing about gravity (that is the problem), while general relativity (GR) is nearly all about gravity. So, in a gravity experiment, people will expect the universe to behave the way GR says it will, not QM.

Now, ok, maybe the universe won't behave like GR says it will. I guess after detecting a wave, people will try to look for its causes. If there are lots of waves without a cause that fits it under GR (unlikely), I guess people will start to contest it. Anyway, QM has nothing to do witht he experiment.

Re:So I didn't RTFA (1)

Alwin Henseler (640539) | more than 4 years ago | (#32163840)

If they're not able to obtain meaningful results (for example if something goes wrong, or the signal/noise ratio somehow gets botched so that results aren't trustworthy), it'll just improve the state of the art of the engineering involved (=not worth it).

If OTOH obtained measurements are solid, then any result is useful, even if 'the meter reads zero'. Remember this experiment would serve to support or dis-prove a theory, so either result would advance the science fields involved.

Re:So I didn't RTFA (1)

bill_mcgonigle (4333) | more than 4 years ago | (#32164080)

What happens if they don't find anything?

Then it re-enforces the notion that we're living in universe that cheats. Like a simulation would.

We already have data that fits the theory [blogspot.com] so perhaps this space probe could show that it was wrong, somehow. It seems better to spend money chasing promising results, though.

Re:So I didn't RTFA (1)

Thinboy00 (1190815) | more than 4 years ago | (#32164666)

What happens if they don't find anything?

Then it re-enforces the notion that we're living in universe that cheats. Like a simulation would.

We already have data that fits the theory [blogspot.com] so perhaps this space probe could show that it was wrong, somehow. It seems better to spend money chasing promising results, though.

Noting for reference that said link has nothing to do with simulated reality [wikipedia.org] (e.g. The Matrix).

not funded yet (4, Informative)

bcrowell (177657) | more than 4 years ago | (#32163542)

I believe the slashdot summary and TFA are misleading, because they make it sound like LISA will definitely be built. According to the WP article [wikipedia.org] , LISA is competing against two other space-based science projects for funding, and the decision won't be made until 2013.

Personally, I would love to see LISA fly. Gravitational waves were first predicted in about 1914. Most aspects of general relativity have been tested pretty thoroughly at this point, but almost a century later we still have no direct confirmation that gravitational waves exist (although there is very strong indirect evidence). And if they can be detected, then it opens up an entirely new way of doing astronomy: not with electromagnetic waves, but with gravitational ones.

Re:not funded yet (0)

Anonymous Coward | more than 4 years ago | (#32163730)

Another excellent use of money to fund the development of new technology that will eventualy benefet mankind when it is released to the public domain.

How badly do we need interferometers in our every day lives? imagine pointing one of those at a potential boss during your interview process!

Re:not funded yet (1)

dunng808 (448849) | more than 4 years ago | (#32163986)

NASA could save a lot of money by studying Kristy Alley.

Re:not funded yet (1)

DryGrian (1775520) | more than 4 years ago | (#32164792)

I popped in for an obligatory "Rosie O'Donell", but I tip my hat to you, sir.

Re:not funded yet (4, Informative)

Chris Burke (6130) | more than 4 years ago | (#32163736)

The NASA and JPL mission pages don't make it clear that this is unfunded as of yet either, which is annoying since I've been reading up on this experiment for some time and am pretty excited about it!

I, too, would love to see LISA fly. We really do need robust tests of gravity waves, and a whole new world of observations will open up to us if it pans out.

One of the coolest things about the mission itself that I read about is the 'drag free' aspect. To ensure that the test masses are in free-fall around the sun without interference by things like the pesky solar wind, they're housed free-floating in a chamber inside the LISA spacecrafts themselves. The spacecraft absorbs the solar wind or other outside forces while measuring any change in relative position to the test mass and using micro-thrusters to keep itself centered on the mass and thus in the same free-fall drag-less orbit. Effin cool imo, even if I don't think it's first time it's been done. :)

Re:not funded yet (1)

gyrogeerloose (849181) | more than 4 years ago | (#32163886)

The spacecraft absorbs the solar wind or other outside forces while measuring any change in relative position to the test mass and using micro-thrusters to keep itself centered on the mass and thus in the same free-fall drag-less orbit. Effin cool imo

If I understand you correctly, you're saying that to keep the mass in the proper orbit and, I have to assume, from banging against the walls of its containment chamber, the spacecraft adjusts its position in relation to the mass, right? Effin' A, that's effin' cool.

Re:not funded yet (1)

Chris Burke (6130) | more than 4 years ago | (#32164068)

That's my understanding as well, yep. It's a brilliant way to compensate for drag without having to measure the drag, just the resulting deviation from freefall.

Re:not funded yet (1)

gyrogeerloose (849181) | more than 4 years ago | (#32164298)

Brilliant indeed. It makes me very happy that in a world that often seems so full of stupidity, there are people who are smart enough to figure that sort of thing out.

Re:not funded yet (1)

Trecares (416205) | more than 4 years ago | (#32164486)

But wouldn't that mean the cube's trajectory lead into the sun? The cubes would be drawn to the sun, and since the cube moves, the satellite has to move inwards, falling into the sun? Kind of reminds me of that Stargate episode where they had to tinker with the space mine heh.

Re:not funded yet (2, Informative)

Chris Burke (6130) | more than 4 years ago | (#32164540)

But wouldn't that mean the cube's trajectory lead into the sun?

It'll be orbiting the sun, in an orbit much like earth's.

Re:not funded yet (0)

Anonymous Coward | more than 4 years ago | (#32170122)

Actually, if memory serves (it has been 7-8 years since I heard a talk on this project) the satellites will be placed in 3 different Lagrange Points created by the Earth and the Sun. So, the orbits will be exceedingly like that of the Earth's.

Re:not funded yet (4, Funny)

HBoar (1642149) | more than 4 years ago | (#32164626)

I think you need to look up what the word 'orbit' means.....

Re:not funded yet (1)

Cyberax (705495) | more than 4 years ago | (#32164402)

Yes, it's not the first time.

Gravity Probe B did the same with _rotating_ _gyroscopes_. In hard vacuum. Cooled to liquid helium temperature.

Now that is cool!

Re:not funded yet (1)

John Hasler (414242) | more than 4 years ago | (#32164500)

> The spacecraft absorbs the solar wind or other outside forces while
> measuring any change in relative position to the test mass and using micro-
> thrusters to keep itself centered on the mass and thus in the same
> free-fall drag-less orbit.

That method could be used to test the Pioneer Effect. You would, of course, need to keep the center of mass of the spacecraft near the center of mass of the test mass, not merely keep the test mass from touching the walls of the chamber.

Re:not funded yet (1)

MichaelSmith (789609) | more than 4 years ago | (#32165160)

> The spacecraft absorbs the solar wind or other outside forces while
> measuring any change in relative position to the test mass and using micro-
> thrusters to keep itself centered on the mass and thus in the same
> free-fall drag-less orbit.

That method could be used to test the Pioneer Effect. You would, of course, need to keep the center of mass of the spacecraft near the center of mass of the test mass, not merely keep the test mass from touching the walls of the chamber.

The system I read about used microwaves to measure the position of the test mass inside the chamber, which obviously impart momentum to the mass, so I imagine you would need to keep the test mass centered as much as possible to have any kind of precision.

Re:not funded yet (1)

networkBoy (774728) | more than 4 years ago | (#32169074)

measure it from the 6 (or three if sphere) points that are equidistant from the test mass, thus while the measurement imparts some force, you are applying that force on all 6 sides of the cube.

Re:not funded yet (0)

Anonymous Coward | more than 4 years ago | (#32170266)

I don't think it's first time it's been done

Yeah, it is very cool. This site [dragfreesatellite.com] has a list and the first was launched in 1972.

Re:not funded yet (0)

Anonymous Coward | more than 4 years ago | (#32166252)

I believe the slashdot summary and TFA are misleading, because they make it sound like LISA will definitely be built. According to the WP article [wikipedia.org] , LISA is competing against two other space-based science projects for funding, and the decision won't be made until 2013.

This is not completely true. LISA is currently undergoing review as part of the astronomy decadal process in the US. The decadal process decides which missions/projects to prioritize for the next decade and will be announced by the end of the year. ESA will have their own decisions, but much depends on what the decadal report recommends. If the US does not prioritize LISA, nor will ESA. This doesn't necessarily mean it won't fly...just not in the next 10 years. Past reviews have praised LISA's science and questioned technological readiness, so it's likely some GW detection mission will fly eventually.

In the meantime, LISA pathfinder should fly in the next few years, which will hopefully help with the ESA recommendation. And we continue to work on improving our understanding of LISA's sources to make the mission more of a success.

(And while I don't know the funding situation all that well, I regularly talk to the people who do, and I personally work on LISA related science).

Re:not funded yet (0)

Anonymous Coward | more than 4 years ago | (#32176276)

I agree withthe previous poster - I wouldn't take the original article too serious, I believe it is part of a concerted action from LISA to save their butts since they're in real danger to lose their mission. Let me explain this in more detail below.

Disclaimer: I work on another mission that is part of the three that are currently competing for the 2020/2021 L-class slot with ESA (and am posting AC for this reason). These missions are LISA, Laplace (a mission to piggy back on a NASA mission to Jupiter and land on Ganymede) and IXO (a X-ray telescope). So, yes, I know the process fairly well.

At the moment ESA is doing industry studies for Laplace and IXO. For LISA the pathfinder is being built (and has overrun its schedule and costing). The plan is to downselect one of these three missions in summer 2011, then to do a full industrial study for the two remaining missions, and then to select one of the missions to be launched in 2020/2021.

In parallel, as stated above the decadal process in the US is going on. That's done by the National Science Foundation for LISA and for IXO, but NOT for Laplace (since with NASA the planetary science budget and the astronomy budget are separate). Both processes are formally separate processes, i.e., the ESA advisory structure will look at the outcome of the European studies and at the science cases (called "yellow book" for some strange reason) independently of the NSF, but it is clear that the decision in Europe won't be made in a vacuum and the decadal process will influence it. Knowing both processes rather well, including panel chairs in the decadal process and members of ESA's Astronomy Working Group and the Space Science Advisory Committee, I would bet that the outcome of both selections would be very similar *even if* the SSAC didn't know what comes out of the decadal process. These reviews really are that thorough that a very good picture on the feasibility and science case is made (for example, for the mission I'm involved in, independent costings were made by NASA headquarters and industry, and a total of 300 pages of supplementary information was provided to the decadal review, which asked really good questions; and similar thorough questions were asked during the mid-term reviews on the ESA side).

Talking to people within the LISA, Laplace, and IXO projects, the technological readiness of Laplace and IXO is high (in aerospace lingo TRL 6 and higher). There is a general agreement that IXO's costing and technological readiness is higher than that of Laplace, but of Laplace being a much easier sell as its science case is much more focused. In addition, David Southwood (ESA's director of science and robotic exploration) is personally more interested in Laplace and Laplace would fit better into ESA's portfolio of planetary missions than IXO. However, Laplace relies even more on NASA than IXO (both missions are joint ESA/NASA missions, but ESA's relative share in IXO would be higher, i.e., there would be more influence/contributions/technological leadership for Europe if IXO went forward, which is important politically, if you're talking spending about 1+ billion Euros [the 800million L-class cost cap plus contributions from the member states]). In addition, Laplace and IXO both have a very large science community behind them (1000+ planetary scientists, 2000+ astronomers). LISA, on the other hand, has a small community (200 odd people max) and is plagued by technological problems. The LISA path finder is over budget and delayed. On the other hand, their science case is very compelling, although it might be better to wait for results from LOFAR and in 5-10 years SKA to see whether gravitational waves can't be detected by other means. For this reason, while I believe that eventually a gravitational wave mission will fly, I would bet that Laplace and IXO will be selected for further studies in mid-2011 and that LISA will be postponed and only compete for the 2nd L-class slot (2025-2030) once it is 100% clear that the pathfinder works.

millions (2, Funny)

thoughtsatthemoment (1687848) | more than 4 years ago | (#32163548)

Damn, I thought one could just write papers to prove something. Now we have to spend millions.

Re:millions (1)

Alwin Henseler (640539) | more than 4 years ago | (#32163738)

Damn, I thought one could just write papers to prove something. Now we have to spend millions.

In science, the only things you can prove by writing papers is that you are able to write, or that you understand math (since ultimately, math is a matter of definition - by humans).

Proving anything else requires field-testing one way or another. Where 'field-testing' may be done in your kitchen sink, if possible.

Re:millions (1)

camperdave (969942) | more than 4 years ago | (#32164314)

since ultimately, math is a matter of definition

... Or the definition of matter is math.

Re:millions (1)

John Hasler (414242) | more than 4 years ago | (#32164536)

> Where 'field-testing' may be done in your kitchen sink, if possible.

Or, if you are a theoretical physicist, by somebody else.

Re:millions (1)

lxs (131946) | more than 4 years ago | (#32166766)

You've obviously never met a theoretical physicist. Many are of a deep seated belief that reality is but a mere shadow of their maths. Luckily the good ones keep a sense of humor about it and give a nod in the direction of reality now and then.

Re:millions (1)

John Hasler (414242) | more than 4 years ago | (#32172668)

> You've obviously never met a theoretical physicist. Many are of a deep
> seated belief that reality is but a mere shadow of their maths.

They are right.

Re:millions (1)

thoughtsatthemoment (1687848) | more than 4 years ago | (#32175902)

Of course. When matter is energy, and energy is matter, why can't we say math is reality and reality is math.

Should we open a betting pool? (0)

Anonymous Coward | more than 4 years ago | (#32163652)

I bet gravity "waves" don't exist.

Re:Should we open a betting pool? (0, Troll)

carp3_noct3m (1185697) | more than 4 years ago | (#32163756)

I bet you're wrong. 100000000000000000000000000000000000000000000000000 trillion dollars.

Re:Should we open a betting pool? (1)

iammani (1392285) | more than 4 years ago | (#32163804)

I bet you both are wrong. I bet gravity waves are sometimes seen, sometimes not.

Re:Should we open a betting pool? (1)

Taco Cowboy (5327) | more than 4 years ago | (#32165980)

I bet you both are wrong. I bet gravity waves are sometimes seen, sometimes not.

I bet all three of you are wrong.

When measured, kenot be observed.

When observed, kenot be measured.

Am I getting at least a patent for this?

Re:Should we open a betting pool? (1)

3seas (184403) | more than 4 years ago | (#32163834)

sure they do and all we have to do to prove it is get the galaxies to stand up in sequence...

LISA - deja vu?? (0)

kaaona (252061) | more than 4 years ago | (#32163788)

As I recall, the last LISA was [also] a grossly overpriced failure.

Re:LISA - deja vu?? (0)

Anonymous Coward | more than 4 years ago | (#32164652)

It looks like Apple has finally managed to sell one to NASA, they just had to wrap it around in gold film.

Re:LISA - deja vu?? (1)

MichaelSmith (789609) | more than 4 years ago | (#32165166)

The UI was groundbreaking, and IMHO, better than most GUIs in use today.

I was like wtf? (4, Funny)

future assassin (639396) | more than 4 years ago | (#32163830)

Won't the Ferengi attack the satellites to steal the gold-pressed latinum?

Re:I was like wtf? (0)

Anonymous Coward | more than 4 years ago | (#32163940)

the cube is gold and platinum which the Ferengi don't really value. Latinum != Platinium.

Re:I was like wtf? (1)

ooshna (1654125) | more than 4 years ago | (#32164184)

Yeah Platinum can be teleported and created Latinum cannot.

Re:I was like wtf? (1)

kybred (795293) | more than 4 years ago | (#32164922)

Yeah Platinum can be teleported and created Latinum cannot.

I thought the 'p' in platinum was silent.

Re:I was like wtf? (0)

Anonymous Coward | more than 4 years ago | (#32165412)

Silent 'p'? Soundproofed bathroom?

BZZZZZT WRONG (0)

Anonymous Coward | more than 4 years ago | (#32166238)

Star Trek - miseducating nerds for over forty years!

Re:I was like wtf? (0)

Anonymous Coward | more than 4 years ago | (#32175870)

No, it's just shorthand for lazy posters. Gold-pressed latinum :gold-p-latinum : gold-platinum.

I'll save them the trouble. (0)

Anonymous Coward | more than 4 years ago | (#32164058)

Just point it in the general direction of their local Jenny Craig, or wherever Kirstie Alley happens to be.

Re:I'll save them the trouble. (1)

MichaelSmith (789609) | more than 4 years ago | (#32165172)

The local doughnut shop?

LISA vs. Pulsar Observations (3, Informative)

stewardwildcat (1009811) | more than 4 years ago | (#32164434)

Just to let you all know, LISA and the Pulsar observations are not observing the same things. Sure they are fighting to detect the first gravitational waves but they are looking at different regimes. Its like comparing the GBT radio telescope to Hubble, they are fundamentally different even if they are looking for the same type of objects. http://www.physik.hu-berlin.de/qom/research/freqref/lisa [hu-berlin.de] explains what frequencies LISA will be sensitive to. The Pulsar array is most sensitive to 10^-4 where as LISA is higher frequencies. LIGO is even higher in frequency. You learn about different objects and new phenomena by studying ALL frequencies available to you. Many astronomy projects are expensive as hell but they develop new technologies that benefit our daily lives. Who knows what laser interferometry in space will generate for the public funding the project.

Gravitational waves my foot (0)

Anonymous Coward | more than 4 years ago | (#32164476)

I never understood how it is that people expect that the shape of gravitational influence between things in the universe could somehow be different than the mass/energy distribution of the actual objects.

If there are black holes quickly orbiting each other then anyone at a constant distance from the center of the orbiting black holes will see their gravity change as the black holes get closer and farther away from them... No mystery..big whoop.. nothing worth going out of your way to research. When you throw in realitivity objects moving realitive to each other see a mass and therefore gravitational difference based on the lorentz factor... again well understood... no mystery...

My second statement because I love basking in my own ignorance.. why do we need massive distant objects to show that gravity waves exist again? Doesn't gravity follow a sqaure law.. and these objects are how far? If we can use gravitometers to map oceans or determine the density of rocks a few feet under the ground why can't we just as easily detect gravity waves from nearby local objects here on earth under our direct control?

Maybe I just don't believe in gravitational waves because for godsake I'm too stupid to understand what the hell they are even supposed to be.

Why gold and platinum? (2, Interesting)

MacroRodent (1478749) | more than 4 years ago | (#32165176)

Wouldn't a lump of lead work as well and be cheaper?

Re:Why gold and platinum? (2, Insightful)

SteveFoerster (136027) | more than 4 years ago | (#32165262)

Given how much it will cost to get these things into orbit around the sun, I'm guessing the cost of the actual materials is comparatively trivial.

Re:Why gold and platinum? (1)

MacroRodent (1478749) | more than 4 years ago | (#32166206)

You are probably right, but it still does not answer the question. The lump of lead is still much cheaper, so there has to be a good justification for using funds on the gold and platinum, instead of more or better instrumentation, more propellant, or other such costs of the project.

(There is also a PR angle: the use of such classic luxury materials sounds extravagant to taxpayers...)

Re:Why gold and platinum? (0)

Anonymous Coward | more than 4 years ago | (#32169642)

Yeah, but the lead does not act too good to the cold temperatures ...
Common problem with the lead sealed tin-cans of food and some unhappy polar explorer ... problem being that the lead scrumbles to dust in cold ...

Re:Why gold and platinum? (1)

Lord Crc (151920) | more than 4 years ago | (#32167190)

Wild guess, perhaps it has something to do with reflective and thermal properties of the material?

They're using the mass as a reference for the satellite position, so I assume they measure the distance to the mass using lasers, hence the need for the mass to be reflective.

Also to increase accuracy I'm guessing that they'd want to minimize the change in physical size of the mass due to thermal fluctuations.

Or I could be completely wrong and they do it just cause it sounds cool :D

Re:Why gold and platinum? (1)

marcosdumay (620877) | more than 4 years ago | (#32168976)

It's unlikely to be due to the reflectivity, if it was the case, a coated cube would be enough. Gold and platinun are known for their stability, so I guess they were choosed because the vacuum inside the ships isn't expected to be perfect (as a second tought, duh, it's inside a ship, so it can't be) and they don't want the cubes to absorb the gases around them.

Re:Why gold and platinum? (1)

John Hasler (414242) | more than 4 years ago | (#32172880)

> It's unlikely to be due to the reflectivity, if it was the case, a coated
> cube would be enough.

It is coated with gold, probably primarily for reflectivity.

> I guess they were choosed because the vacuum inside the ships isn't
> expected to be perfect (as a second tought, duh, it's inside a ship, so it
> can't be)...

It is inside a special chamber inside a spacecraft. It will have the best vacuum possible.

> ...and they don't want the cubes to absorb the gases around them.

There won't be any. However, the gold coating will help minimize the amount of gas adsorbed before the chamber is evacuated.

Re:Why gold and platinum? (1)

John Hasler (414242) | more than 4 years ago | (#32172818)

> Wouldn't a lump of lead work as well...

No. Platinum is much denser and also much harder. The cube is plated with gold because it is highly reflective and inert.

My Own Gravity Wave (0, Offtopic)

b4upoo (166390) | more than 4 years ago | (#32165650)

Years ago I rented a tiny travel trailer that was quite old. The rent deal was fabulous and the guy that owned the park was a good fellow. At any rate I seem to have created my own gravity wave. I bedded a young woman and in the act of passion all four legs of the bed shot right through the floor. I never missed a stroke.
                  The fellow that owned the park came to make the repair the next day while the girl was still there. After he put in a new floor in the bedroom I entered and he congratulated me for the strength and success of my passions.
                  The moral being that if we musty have gravity waves we should get some good fun out of it!

Cosmology in deep crisis (0)

Anonymous Coward | more than 4 years ago | (#32165836)

There are noe gravitional waves. There are no black holes. There are no dark matter. There are no dark energy. There are no big bang.

We need fresh, new ideas which actually make an attempt to explain what we observe.

A platinum cube? (1)

Dialecticus (1433989) | more than 4 years ago | (#32166450)

... each with a payload of two lasers and a 4.6-cm cube of gold-platinum alloy ...

... which they intend to use as a duodynetic field core. 5 or 6 pounds should be sufficient.

Re:A platinum cube? (1)

imakemusic (1164993) | more than 4 years ago | (#32166956)

5 or 6 pounds should be be enough for anyone.

ftfy

Dumb question regarding gravity in general (3, Interesting)

smooth wombat (796938) | more than 4 years ago | (#32167680)

We know the Holy Grail is to have a Grand Unified Theory of the four forces. To date, three have been combined with gravity being the lone holdout.

Is there a reason why gravity can't be a force unto itself but rather, the result of the other three forces? By that I mean, since the Strong and Weak forces hold things together, is there some reason they can't be creating gravity with their forces weakening the further out you go, similar to how radio waves get weaker as they propagate outwards.

Even though this experiment is an attempt to detect gravitational waves, since we haven't found any to date, could the above be a different explanation for why we haven't found any (yet)?

Re:Dumb question regarding gravity in general (1)

hansraj (458504) | more than 4 years ago | (#32172204)

Is there a reason why gravity can't be a force unto itself but rather, the result of the other three forces? By that I mean, since the Strong and Weak forces hold things together, is there some reason they can't be creating gravity

I am having comprehension problem with what you wrote (Not a native English speaker..). Do you mean to ask:

A) Why gravity couldn't be independent of the other three forces?, or
B) Why couldn't gravity be a manifestation of the other forces over a distance?

I might be wrong (IANAP) but the Standard Model already unifies the three other forces except Gravity. That means that if you can show that gravitational interaction arises from strong and weak interactions then essentially you have shown that the Standard Model is in fact GUT.

If on the other hand gravity is independent of the other forces then all attempts to unify gravity with them will fail, but since we assume one theory behind everything the lookout will continue.

If the continued search of gravitational waves do not succeed then in the long run it will point to serious flaws in GR. (Every failed attempt narrows down the search range of gravitational waves, and at some point the remaining range will conflict with something else).

Re:Dumb question regarding gravity in general (1)

smooth wombat (796938) | more than 4 years ago | (#32172550)

B. I know I wasn't quite as elegant in my language as I should have been, but it's one of those questions I've had rattling around my skull for some time and would pop out if I met Hawking, Kaku, etc.

The question has always been, why is gravity the weakest of the three even though it's the one we're most familiar with? My solution (yeah right) would be because the other three forces are so much stronger that like radio waves, their strength decreases the further out you go.

Again, since we haven't detected any gravitational waves, using either Occam's Razor or Sherlock Holmes' comment about eliminating the impossible and whatever is left, no matter how improbable, must be the truth, it would seem the reason we can't unify gravity with the other three is because it's not a separate force, but is the result of the other three forces interacting with one another.

On a side note, if someone in the field decides to pursue this and finds I'm partially or fully correct, I want credit for it. It will probably be the only thing history will know me for (unless I'm elected benevolent dictator of Earth).

Re:Dumb question regarding gravity in general (1)

John Hasler (414242) | more than 4 years ago | (#32172924)

> Again, since we haven't detected any gravitational waves, using either
> Occam's Razor or Sherlock Holmes' comment about eliminating the impossible
> and whatever is left, no matter how improbable, must be the truth...

One of the things that is left is that our detectors are not yet sensitive enough.

Re:Dumb question regarding gravity in general (1)

Chris Burke (6130) | more than 4 years ago | (#32174308)

We know the Holy Grail is to have a Grand Unified Theory of the four forces. To date, three have been combined with gravity being the lone holdout.

Actually, the three forces we've unified are electricity, magnetism (as electromagnetism) and then the weak force into the "electroweak". The Strong force has yet to be unified.

Since GR came along to describe gravity not as force but as geometry, the desire to unify it has been lessened. Not that that people don't want to. But surely unifying the electroweak and strong forces comes before speculating that gravity doesn't exist unto itself and is just an aspect of the "electroweakstrong" force.

Is there a reason why gravity can't be a force unto itself but rather, the result of the other three forces? By that I mean, since the Strong and Weak forces hold things together, is there some reason they can't be creating gravity with their forces weakening the further out you go, similar to how radio waves get weaker as they propagate outwards.

*shrug* Sure. Propose a mechanism by which it could happen, see if your hypothesis makes any testable predictions, and we go from there.

Just fyi, though... The strong and weak forces both drop off at a rate much faster than the approximately inverse-square relationship of gravity. Both are really only relevant at distances on the order of the size of atomic nuclei. This is why neutrinos (and the favored dark matter candidates which are similar) are so hard to detect, because they only interact via the weak force. There's also the problem that the strong force only operates on color, which quite a few mass-full particles don't have.

But if you can think of some way that these interactions produce the long-reaching effects of gravity, more power to you!

Even though this experiment is an attempt to detect gravitational waves, since we haven't found any to date, could the above be a different explanation for why we haven't found any (yet)?

I honestly don't know how, but really, I'm not sure what the above is supposed to imply. Why wouldn't there be gravity waves in this case? The electroweak and strong forces fluctuate in a cyclical fashion, so wouldn't any effect created by those forces have the same potential?

Anyway, I wouldn't take the non-discovery of gravity waves as a huge mystery that must be solved quite yet. They're just really hard to detect, as even some of the biggest hypothetical sources produce very tiny waves with extremely long periods. LISA hasn't been launched (or even funded T_T) yet, and the longest period of gravity wave it will be able to detect is 10 seconds.

My prediction: (0)

Anonymous Coward | more than 4 years ago | (#32176236)

They won't find one. Why? Because gravity is a feature of mass in space - not a force or an energy. There are no gravitons and there are no gravity waves.

Re:My prediction: (0)

Anonymous Coward | more than 4 years ago | (#32177256)

There almost certainly are gravity waves. Gravity is a feature of space, or rather of geometry, and the theory (GR) that describes static fields also permits wave solutions produced by changing mass-energy quadrupoles, such as the Hulse-Taylor binary pulsar system. Incidentally, this system appears to be losing energy at precisely the rate you'd expect it to from gravity wave emission.

Load More Comments
Slashdot Account

Need an Account?

Forgot your password?

Don't worry, we never post anything without your permission.

Submission Text Formatting Tips

We support a small subset of HTML, namely these tags:

  • b
  • i
  • p
  • br
  • a
  • ol
  • ul
  • li
  • dl
  • dt
  • dd
  • em
  • strong
  • tt
  • blockquote
  • div
  • quote
  • ecode

"ecode" can be used for code snippets, for example:

<ecode>    while(1) { do_something(); } </ecode>
Create a Slashdot Account

Loading...