Mini solar system could reveal hidden dimensions

[Rick]

A tiny, artificial solar system could reveal hidden spatial dimensions and test alternative theories of gravity, a new study suggests. If the system's "planets" moved slightly differently than expected from standard gravity, it would signal the presence of new physical phenomena - which have proven very difficult to test.

Numerous theories that attempt to unify all the forces of physics into one cohesive model call for hidden spatial dimensions in addition to the three we can sense. In some of these theories, gravity would leak into the extra dimensions - explaining why it is a relatively weak force in the universe we know.

This leakage would dilute its power and cause deviations from the standard law of gravity, which would be especially noticeable at very small scales. But scientists have not been able to measure the force of gravity between closely spaced objects in the lab with enough accuracy to test these theories.

"Direct measurement of the gravitational force at distances smaller than a fraction of a millimetre is an extremely difficult task," says Varun Sahni of the Inter-University Centre for Astronomy and Astrophysics (IUCAA) in Pune, India. Stray electromagnetic forces tend to overwhelm gravity in experiments at this scale, he told New Scientist.
Fixed in space

Sahni proposes an alternative way to measure gravity on small scales. He and colleague Yuri Shtanov at the Bogolyubov Institute for Theoretical Physics (BITP) in Kiev, Ukraine, say it could be done by sending a "solar system in a can" into space.

This artificial system would reside inside a spacecraft that would be sent to the L2 Lagrange point (see image, below right). That point lies about four times as far away from Earth as the Moon does.

A spacecraft placed there would stay fixed in space, relative to Earth, making it easier to monitor. The Earth would also shield it from the Sun's radiation, which pushes gently on any objects it shines on. Any such push could change the spacecraft's position relative to the tiny "planets" held inside it.

Once at the Lagrange point, the artificial solar system would be set in motion inside the spacecraft. An 8-centimetre-wide sphere of tungsten would act as an artificial sun, while a smaller test sphere would be launched 10 cm away into an oval-shaped orbit. The miniscule planet would orbit its tungsten sun 3,000 times per year.
Higher dimensions

If gravity is leaking into extra dimensions, the slight change in its force should cause the planet's oval-shaped orbit to rotate, or precess, slowly. Sahni and Shtanov calculated the effect for a theory called the Randall-Sundrum model, which says that our universe is a 3D slice of a bigger, higher dimensional universe. They find the orbit would precess by 1/3600

 

[Rick]

This might have been posted before, but thought I'd post it here because the article above mentions it.

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13 things that do not make sense

* 19 March 2005
* NewScientist.com news service
* Michael Brooks

1 The placebo effect

DON'T try this at home. Several times a day, for several days, you induce pain in someone. You control the pain with morphine until the final day of the experiment, when you replace the morphine with saline solution. Guess what? The saline takes the pain away.

This is the placebo effect: somehow, sometimes, a whole lot of nothing can be very powerful. Except it's not quite nothing. When Fabrizio Benedetti of the University of Turin in Italy carried out the above experiment, he added a final twist by adding naloxone, a drug that blocks the effects of morphine, to the saline. The shocking result? The pain-relieving power of saline solution disappeared.

So what is going on? Doctors have known about the placebo effect for decades, and the naloxone result seems to show that the placebo effect is somehow biochemical. But apart from that, we simply don't know.

Benedetti has since shown that a saline placebo can also reduce tremors and muscle stiffness in people with Parkinson's disease (Nature Neuroscience, vol 7, p 587). He and his team measured the activity of neurons in the patients' brains as they administered the saline. They found that individual neurons in the subthalamic nucleus (a common target for surgical attempts to relieve Parkinson's symptoms) began to fire less often when the saline was given, and with fewer "bursts" of firing - another feature associated with Parkinson's. The neuron activity decreased at the same time as the symptoms improved: the saline was definitely doing something.

We have a lot to learn about what is happening here, Benedetti says, but one thing is clear: the mind can affect the body's biochemistry. "The relationship between expectation and therapeutic outcome is a wonderful model to understand mind-body interaction," he says. Researchers now need to identify when and where placebo works. There may be diseases in which it has no effect. There may be a common mechanism in different illnesses. As yet, we just don't know.
2 The horizon problem

OUR universe appears to be unfathomably uniform. Look across space from one edge of the visible universe to the other, and you'll see that the microwave background radiation filling the cosmos is at the same temperature everywhere. That may not seem surprising until you consider that the two edges are nearly 28 billion light years apart and our universe is only 14 billion years old.

Nothing can travel faster than the speed of light, so there is no way heat radiation could have travelled between the two horizons to even out the hot and cold spots created in the big bang and leave the thermal equilibrium we see now.

This "horizon problem" is a big headache for cosmologists, so big that they have come up with some pretty wild solutions. "Inflation", for example.

You can solve the horizon problem by having the universe expand ultra-fast for a time, just after the big bang, blowing up by a factor of 1050 in 10-33 seconds. But is that just wishful thinking? "Inflation would be an explanation if it occurred," says University of Cambridge astronomer Martin Rees. The trouble is that no one knows what could have made that happen.

So, in effect, inflation solves one mystery only to invoke another. A variation in the speed of light could also solve the horizon problem - but this too is impotent in the face of the question "why?" In scientific terms, the uniform temperature of the background radiation remains an anomaly.
3 Ultra-energetic cosmic rays

FOR more than a decade, physicists in Japan have been seeing cosmic rays that should not exist. Cosmic rays are particles - mostly protons but sometimes heavy atomic nuclei - that travel through the universe at close to the speed of light. Some cosmic rays detected on Earth are produced in violent events such as supernovae, but we still don't know the origins of the highest-energy particles, which are the most energetic particles ever seen in nature. But that's not the real mystery.

As cosmic-ray particles travel through space, they lose energy in collisions with the low-energy photons that pervade the universe, such as those of the cosmic microwave background radiation. Einstein's special theory of relativity dictates that any cosmic rays reaching Earth from a source outside our galaxy will have suffered so many energy-shedding collisions that their maximum possible energy is 5

 

[Rick]

Forgot to add the link:

http://www.newscientistspace.com/article/dn9484-mini-solar-system-could-reveal-hidden-dimensions.html