Come on big gravity waves... No whammies!

November 18, 2005 9:38 AM

Do Gravity Waves Exist?This is one of the big unanswered questions in physics. Gravity telescopes such as the LIGO and the Geo 600 may soon tell us. These massive detectors are sensitive to a displacement of 1 part in 1000000000000000000000-- that's like "measuring a change of one hydrogen atom diameter in the distance from the Earth to the Sun." Such a discovery would mean a tremendous boom to science. And big cash payouts to those who put their money where there mouth was.
posted by justkevin (32 comments total)

BOOOOOM!
posted by mikrophon at 9:41 AM on November 18, 2005

2nd there = their
posted by justkevin at 9:44 AM on November 18, 2005

Do Gravity Waves Exist?

For that matter, do comedy waves exist?
posted by ZenMasterThis at 10:03 AM on November 18, 2005

These gravity waves have a vibrating newsletter about mushroom overlords?
posted by Captaintripps at 10:11 AM on November 18, 2005

This is pretty awesome stuff. I wish they'd get a little deeper into it or provide links to gravitational physics for (not so) dummies. Radio waves are another way of explaining photons, what's the particle for gravitational waves?
posted by substrate at 10:15 AM on November 18, 2005

Gravitons.
posted by ZenMasterThis at 10:18 AM on November 18, 2005

"gravitational physics"

The only gravitational physics that is widely accepted is general relativity which very much does not talk about "gravitons" and in fact you'll find relativists to be touchy about people talking about gravity as a "field" or something mediated by a particle. From the relativistic point of view, gravity is a property of spacetime related to mass.

Following the links above and similar, you will find people trying to connect relativity physics with particle physics and there you'll find the "graviton", a very speculative particle and well beyond our current means to detect if it exists.
posted by Ethereal Bligh at 10:35 AM on November 18, 2005

And if they exist, can gravity surfing be far behind?
posted by spock at 10:41 AM on November 18, 2005

My mistake. Gravity Surfing already exists.
posted by spock at 10:43 AM on November 18, 2005

What do you think skateboarding and surfing itself is?
posted by loquacious at 10:44 AM on November 18, 2005

You are forgetting about the coolest satellite of all, the Gravity Probe-B. It has 2 silicon-quartz gyros that are the most perfect spheres ever made. If they were earth-sized, the change in elevation wouldn't vary by more then 12 feet, and they can spin at 10000rpm for 1000 years and only lose 1 percent of speed. Interesting stuff! They just hit a year of data collection recently and are about to start number crunching.
posted by Mach5 at 10:47 AM on November 18, 2005

It's worth noting also the indirect observations of gravity waves that already have been made. As gravitational waves are emitted by a system, there is, of course, energy loss, due to conservation of energy. In a binary star system (two stars orbiting one another), that energy should be observable as the orbit collapsing, and the orbital period decreasing. Hulse and Taylor observed this change in the orbit of a pair of neutron stars over several years, and their data matched up to the general relativity prediction extremely well.
posted by kickingtheground at 11:11 AM on November 18, 2005

That gave me today's science hard on. Thanks!
posted by Smedleyman at 11:23 AM on November 18, 2005

Beat me to it, kickingtheground. I got to see Joseph Taylor speak at Trinity University in San Antonio in 1995, as part of their wonderful Distinguished Scientist Lecture Series. Best presentation of science to laymen I've ever seen.

I happen to have my notes right here. The pulsar, part of a binary system, pulses with a period of about 59 msec. It's about 20k LY away. The orbital period is 7.8 hrs. Due to loss of energy as gravitational radiation, the orbital period shortens by about 1 second per year. This decay is parabolic, exactly matching the prediction of general relativity. Hulse and Taylor tracked this from 1975 to 1992.

Taylor proposed a gedanken experiment to detect gravitational radiation. Spin a metal rod of 500 tons at 30 cycles/second. The gravitational radiation from this would be about 10^-22 erg/sec. (An eye blink requires about 1 erg.) The Hulse-Taylor pulsar emits grav rad at about 10^33 erg/sec, which is about 1/400 of its electromagnetic output.
posted by neuron at 11:49 AM on November 18, 2005

The wonders at CERN are neat too...there are some amazingly sensitive detectors there. Not quite as gnarly as the gravity wave thingumajig but close.
posted by lalochezia at 12:14 PM on November 18, 2005

Taylor proposed a gedanken experiment to detect gravitational radiation. Spin a metal rod of 500 tons at 30 cycles/second.

You know I tried that, but couldn't get it to spin any faster than 20 cycles/second. :(
posted by Bort at 12:33 PM on November 18, 2005

Possibly stupid question from a non-scientist: If I understand what I've read (and I probably don't), gravity waves can't be "seen". As they seem to be using lasers for the detection process...aren't they really just detecting the effect that gravity waves has on electromagnetic waves? Not that that's a bad thing. Maybe that's the goal. Simple detection.
posted by weirdoactor at 12:42 PM on November 18, 2005

gravity waves has = gravity waves have

(I'm also not an English major...)
posted by weirdoactor at 12:44 PM on November 18, 2005

Possibly stupid question from a non-scientist: If I understand what I've read (and I probably don't), gravity waves can't be "seen". As they seem to be using lasers for the detection process...aren't they really just detecting the effect that gravity waves has on electromagnetic waves? Not that that's a bad thing. Maybe that's the goal. Simple detection.

Actually, what they're (hopefully) detecting is the actual stretching and squeezing of space (they call it a 'strain'). The gravity wave has some polarization, and, if it happens to hit the detector head-on, it will apply stretch one of the orthogonal arms, while squeezing the other. Literally, the length of the arms will change, and the mirrors on the far ends will get a very tiny bit closer or farther away. The idea is that this very tiny differential change in the lengths of the two arms is what's detected by the interferometer.
posted by kickingtheground at 1:03 PM on November 18, 2005

weirodactor, that's a really odd way of looking at things. Yes, we can't see the gravity waves, in the same way that you can't see the microwaves in your, er, microwave, or the wind, or the electrical signals that bring the cable signal to your telly box.

Everything we ever observe or measure is 'just' the effect of something on something else.

I mean, even looking at a physical object with your eyes is 'just' observing the way that electromagnetic waves are affected by the object.
posted by chrismear at 2:25 PM on November 18, 2005

weirodactor, that's a really odd way of looking at things

You've...um...noticed my name, yes? Ha.

I guess I meant "observing the way electromagnetic energy is affected". Which probably means the same thing. I guess I'm just curious about what will be accomplished by proving that they exist. Will this lead to undeniable proof of the Big Bang? Because I'm all for that. But if they wanna build a zero point energy weapon, then NO! STOP! BAD SCIENTIST! NO MAKING ME FLY AROUND WITHOUT MY PERMISSION!

Again, I'm a non-scientist. Ask me about cooking or writing or acting or playing certain video games, and I'll probably sound like less of a moron. Well. Maybe.
posted by weirdoactor at 2:38 PM on November 18, 2005

"weirodactor, that's a really odd way of looking at things."

...but very common. I will grudgingly admit that it's overwhelmingly natural that we would privilege the very particular physical ways we experience the universe and see anything that must be mediated first to be less "real" and less trustworthy—but that doesn't make it true.

Where it gets really, really, really maddening is when someone claims that we "don't really know" about something remote in time or space. Creationists will say that, well, evolution is necessarily merely a theory (in the popular usage of the term, that is, "hypothesis") because it's in the distant past and no one has or ever will see it. You can see the veins on my head throbbing. I don't privilege either my direct senses or proximity in this way with regard to veracity.

When weirdoactor wrote that about "seeing" my immediate thought was that bugbear of mine, when the press insists on claiming that we "listen with radio telescopes". It is a different sort of thing, true, but it display the same kind of naivete.
posted by Ethereal Bligh at 2:47 PM on November 18, 2005

This reminds me of the race to detect properties of the aether - each scientist creating more sensitive equipment, to detect something that simply isn't there, before giving up. I was really surprised to learn in my History of Modern Science class that the Michelson-Morely experiment was originally designed to measure the velocity of the aether - they don't teach it like that in freshman physics!
posted by muddgirl at 2:52 PM on November 18, 2005

I think "naivete" is a rather strong word to use in this case. I much prefer "sci-tarded".
posted by weirdoactor at 2:59 PM on November 18, 2005

Warning: no references herein...

I thought that astronomers were now largely convinced that gravity waves do exist, based on the following experimentobservation. They watched a couple of neutron stars circle one another in a deadly dance and collapse into one. If energy isn't leaving the system, then the stars will stay at a constant distance (assuming circular orbits, of course). But measuring the light output, there wasn't enough coming out to explain the pair collapsing as quickly as they did. "Therefore", the rest was probably coming out in gravity waves.

So somebody told me! Don't remember no more!
posted by Aknaton at 3:12 PM on November 18, 2005

muddgirl writes "I was really surprised to learn in my History of Modern Science class that the Michelson-Morely experiment was originally designed to measure the velocity of the aether - they don't teach it like that in freshman physics!"

Serious? The only times in any of my physics classes that I've heard mention of Michelson-Morley was in regards to measuring the velocity of the earth relative to the aether. Why were you discussing it in your classes, out of curiosity?
posted by vernondalhart at 6:18 PM on November 18, 2005

So... have y'all subscribed to Symmetry yet? It's free!
posted by goodnewsfortheinsane at 6:18 PM on November 18, 2005

"I was really surprised to learn in my History of Modern Science class that the Michelson-Morely experiment was originally designed to measure the velocity of the aether - they don't teach it like that in freshman physics!"

See if you can get a refund for that class.
posted by Opposite George at 7:11 PM on November 18, 2005

Want to help process the data from the laser interferometers looking for gravitational waves? http://einstein.phys.uwm.edu/
posted by musicinmybrain at 9:16 AM on November 19, 2005

PBS' The Elegant Universe provides a nice visualation of the gravity wave.

Select chapter 3 - it's about 2 minutes in.

Available in QT and Real formats.
posted by jungturk at 3:01 PM on November 19, 2005

A definition of the term "visualation" is available in chapter 12, which covers Quantum English.
posted by jungturk at 3:02 PM on November 19, 2005

and jungturk proves that if you have to correct yourself, that at least you can do it with style.
posted by quin at 4:14 PM on November 19, 2005