Neat Stuff: Top 13 Unanswered Questions in Science

[peeplj]

Hi guys, came across this link and thought I'd share:

http://www.newscientist.com/channel/spa ... 524911.600

Cool stuff....makes you wonder.

--James

[Walden]

14. Where do the socks go, when you put them in the dryer?

[Flyingcursor]

Interesting article.

One of the articles mentions that broadcasting in the 1420 mhz range is prohibited by international law. Anyone have any idea why that would be?
Why would a radio frequency be prohibited by international law?

- Confused

[dubhlinn]

No idea but I imagine it has to do with airplane communications with ground control.

Slan,
D.

[Random notes]

My guess would be that 1420 MHz is reserved for radiotelescope exploration just to avoid local pollution.

Just a guess, tho'

Really interesting piece - I was recently trashing homeopathy to my sister-in-law who is big on herbs and alternative med. I'll have to be careful what I say in the future.


Roger

[BillChin]

TAKE our best understanding of gravity ...

This has been on my mind for some time. Is gravity propagated by waves or particles or some combination? Does gravitational influence travel at the speed of light? The mind puzzle would be if you created new mass from transmitted energy, would the gravitational effect propogate at the speed of light?

It is difficult to conduct meaningful experiments because gravity is such a weak force, and it is non-trivial event to create mass or destroy mass. Destroying mass converts it to energy and that would throw off any reading for the tiny gravity component. Creating mass is a more interesting way to proceed, but again, the gravity would be tiny for any amount of mass that humans can currently create.
+ Bill

P. S. Well I went looking for answers, from:
http://www.curtin.edu.au/curtin/dept/ph ... index2.htm

P. P. S. But What if the THEORY is incorrect? That gravity is not propagated by waves and does not travel at the speed of light? Wowsers then...

According to Einstein's special relativity, nothing can travel faster than the speed of light. This statement applies to gravity also. When you throw a stone into a pool of water a disturbance is created, namely the waves. In general relativity, the geometry of spacetime depends on the distribution of matter. Any significantly large accelaration of matter such as a star exploding or collapsing produces a disturbance of spacetime.

This disturbance propogates through space at the speed of light, and is called gravitational radiation, or a gravitational wave. Gravitational waves are thought to be produced by large disruptions in spacetime. Events such as supernova, binary pulsars and collapsing stars are good candidates for producing gravitational waves as they all involve radipdy accelarating matter.

As yet no gravitational waves have been experimentally detected. Their existance is based entirely upon theory. Imagine a binary pulsar system in which the stars orbit at, say 0.2 percent of the speed of light (ie. very fast!). If the period of orbit of the pulsars was to decrease by a small amount each day, we could infer that some energy is being gradually removed from the system. This would cause the distance between the two pulsars to decrease a small amount each day to reflect the loss of energy in the system. If the only way the energy loss can occur is through gravitational radiation, then we can infer the existance of gravitational waves. In fact, such systems are known to exist in the universe and are being observed.

So how do we detect gravitational waves? We need a gravitational wave detector that is sensitive to the gravitational radiation. Herein lies the problem: the vibrations of matter resulting from gravitational waves are extremely small. For example, if a star was to collapse into a black hole in our galaxy, the gravitational radiation would cause 2 masses on earth a distance of 1m apart to move by 0.01 times the diameter of an atomic nucleus. That is an extremely small motion to detect.

[izzarina]

Really interesting piece - I was recently trashing homeopathy to my sister-in-law who is big on herbs and alternative med. I'll have to be careful what I say in the future.

I'm usually a skeptic when it comes to that type of thing (homeopathy...not herbs in general which I never doubted worked), but after getting the Chicken Pox at age 29, I can absolutely guarantee that it DOES work. The only thing that helped with the itching and discomfort was Rhus Tox, which is poison ivy. I have no idea HOW it works, but it does.

[Random notes]

I can buy into herbals. There are any number of compounds in plants that have therapeutic value and many modern pharmaceuticals are derived from plant compounds. But I have a real problem with the rationale behind homeopathy. That a chemical that was once in water but has been diluted out not merely below detectable limits but beyond the point where even a single molecule of that chemical is present can still leave an "imprint" on the water is simply -IMHO - nonsense. If there is a therapeutic value to homeopathy it is likely related to the placebo effect. The connection between the mind, the brain and the immune system (neuroimmunomodulation) is complex and difficult to study.

In your case, itching is (I think) directly related to histamine release and that is the very limited field on which the Belfast study bears. There are a homeopathic remedies sold at my local Co-Op and some of the people there believe that they are effective for relief of allergies which may also be histamine-mediated. (Maybe we can get Dr. Amar to weigh in on this.)

The discovery of a specfic effect related to histamine release is interesting. In order for it to accepted, though, it has to be replicated and a mechanism has to be proposed and tested. But "...it remains true that no homeopathic remedy has ever been shown to work in a large randomised placebo-controlled clinical trial."

Still, I wouldn't mind being dead wrong about homeopathy - scientists seems to make the most progress when someone discovers that everything they know is wrong.

Roger

[emmline]

So how do we detect gravitational waves?

Sorry Bill. It's enough of a stretch for me to think of gravity as involving particles at all. I grasped the concept of bent space, and objects following the resulting geodesic which may not be a straight line, but it's hard to throw particles or waves into that mix.

I think about physicists similarly to the way I think about really good musicians--i.e., Dang that's cool! I wish I could do that!

[Jeff Stallard]

There's no such thing as gravity! The Earth sucks!

[emmline]

So how do we detect gravitational waves?

I changed my mind. The answer is obvious. We shrink Frankie Avalon to Planck length and turn him loose with a surfboard.

[scottielvr]

Thanks for posting this; fascinating stuff, though most of it makes my brain bleed. It's fun to be reminded that the life of the research scientist is one haunted by feelings of ignorance, embarrassment and maddened frustration.

I'd wondered where cold fusion had gone; good to see it hasn't. That belonged on the "Where are they now" thread, I guess.

[Darwin]

This is an excellent example of the fact that scientific theories can seldom, if ever, be considered as final truths. They tend to be the best we can do with what we know, but what we know keeps changing. More details always require more detailed explanations. The more fine-grained the theories become, the more accurate they become in terms of making predictions--and the more uncomfortable for those who want a relatively simple "theory of everything". On the other hand, the end result may actually lead to simplification. Surely both particle physics and cosmology are approaching levels of complexity that would make William of Ockham barf.

If the "ultra-energetic cosmic rays" and "dark matter" problems require revsions of "laws" proposed by Einstein and Newton, that's great. Things can only improve from there. For one thing, these are the kinds of problems that keep scientists from maintaining religion-like belief in the inerrancy of their theories. In the end, even the greatest of the prophets can be doubted.

As a Big Bang skeptic, the "horizon problem", the "dark energy problem", and the "not-so-constant constants" are of particular interest to me.

It is mentioned that one of the problems with "tetraneutrons" is that, "t would mean that the mix of elements formed after the big bang was inconsistent with what we now observe and, even worse, the elements formed would have quickly become far too heavy for the cosmos to cope."

But, of course, if there never was a Big Bang, then all analysis based on this mythical event becomes irrelevant.

[chas]

So how do we detect gravitational waves? We need a gravitational wave detector that is sensitive to the gravitational radiation. Herein lies the problem: the vibrations of matter resulting from gravitational waves are extremely small. For example, if a star was to collapse into a black hole in our galaxy, the gravitational radiation would cause 2 masses on earth a distance of 1m apart to move by 0.01 times the diameter of an atomic nucleus. That is an extremely small motion to detect.

It's not easy. The current project has two interferometers, each with (I think) 4 km arms, one in Louisiana, the other in Washington state. It's a very interesting project, and while I question its scientific necessity, just as the Apollo program, it's leading to some major advances in things like optics polishing and vibration isolation. More here:

www.ligo.caltech.edu

[BillChin]

So how do we detect gravitational waves? We need a gravitational wave detector that is sensitive to the gravitational radiation. Herein lies the problem: the vibrations of matter resulting from gravitational waves are extremely small. For example, if a star was to collapse into a black hole in our galaxy, the gravitational radiation would cause 2 masses on earth a distance of 1m apart to move by 0.01 times the diameter of an atomic nucleus. That is an extremely small motion to detect.

It's not easy. The current project has two interferometers, each with (I think) 4 km arms, one in Louisiana, the other in Washington state. It's a very interesting project, and while I question its scientific necessity, just as the Apollo program, it's leading to some major advances in things like optics polishing and vibration isolation. More here:

www.ligo.caltech.edu

Wow, interesting stuff. I find it funny that two rabbits jumping, one at each location, might throw this experiment for a loop or two. The most interesting outcome would be if no waves are detected even by 2010. A person can only imagine the implications if gravity does not propagate at the speed of light.

I am convinced that a lot of stuff that we believe to be scientific "fact" today will be considered as quaint as 2000 year old "facts" in my lifetime. Many widely held scientific facts accepted today will seem as idiotic as a flat earth. The rate of research is so much faster now in so many areas.
+ Bill

>>>
No Noise, Please!
If only it were so easy. Many, many types of competing vibrations, or noise, can jostle the test masses enough to mask the effect of a true gravitational wave.

Loggers felling trees nearby cause noise. The crash of ocean waves produce noise. “Even the motion of the atoms inside the mirrors are making the mirrors move,” says Gabriela González, a physicist at nearby Louisiana State University.

Scientists have taken painstaking precautions to reduce the impact of noise on LIGO. The mirrors are suspended on a single thin metal wire to reduce the effects of forces other than gravity. To dampen competing vibrations, investigators constantly adjust the mirrors with the ultraprecise equivalent of a car suspension system.

Still, how do you detect a gravitational wave and not a rabbit jumping nearby? “That’s the $300 million question,” laughs González. One way is by checking if a suspected wave coincided with a disturbance registered by other instruments on site, which look for changes in ground motion, magnetic field, power line voltage, and other aspects. Another way, González explains, is by double-checking results with LIGO’s twin—a complete duplicate facility constructed in a barren scrub desert in Hanford, Washington. At 3,030 km away, it’s distant enough that seismic and other disturbances won’t affect both observatories simultaneously.

So Have They Found Anything at All?
Nope. LIGO started making preliminary runs in 2002, but it still hasn’t noticed its first gravitational wave. Weiss says the instruments are not yet at the level of sensitivity they need to be to detect waves easily. To get to that level, the team spends their days “commissioning”: calibrating devices, finding and solving glitches, and analyzing noisy squiggles of initial data.

Expect the observatory to turn on for real in 2005. By 2010, next-generation equipment will be retrofitted into all existing LIGO facilities. This will improve the sensitivity by about 15 times to capture more, fainter, and different frequencies of gravitational signals.

Most astrophysicists feel that LIGO’s payoffs will be worth the incredible effort it has taken to construct and operate it. “Imagine life before Galileo pointed a telescope at the sky,” suggests Janna Levin, a Columbia University cosmologist. “There’s no question. It could be that big.”