Evaluation

Process 1

scientist-responsible for the content

The scientist is responsible for collating all the questions which are brought up, and searching the Internet for answers. Where interesting explanations are found, they can be posted and where this is not possible, the questions can be posted to stimulate further debate.

Examples of questions:

Will Einstein's theory of gravitation continue to prevail in decades to come?
Even if we can't answer this question right now, let's think of:

In Einstein's universe, mass is converted into energy in the cores of stars, enabling them to shine, while matter curves space, and time flows faster or slower depending on relative motion or gravity. Einstein's General Theory of Relativity has largely stood the test of time; its manifestations are much evident in the observable universe. Indeed, current models of how the cosmos began and evolved are largely founded upon Einstein's theory.

Present models acknowledge that in "the big picture," gravity reigns supreme and alone will decide whether the universe keeps expanding or falls back on itself in a "Big Crunch ." So it's understandable that some physicists remain unsettled that a key prediction of Einstein's General Theory, namely gravitational radiation, remains unverified nearly 80 years later.

Then there are black holes.
Most relativity researchers now believe that General Relativity is not only consistent with black holes but demands that they exist under certain conditions. Prove that black holes populate the co smos, and you've pretty much confirmed an important component of General Relativity. Also, if black holes are for real, under certain conditions they could prove to be powerful sources of gravitational waves, which are also po stulated by General Relativity. However, other cosmic phenomena could generate these ripples in spacetime.

RELATIVITY GOES DIGITAL

Einstein's Challenge

In 1916, Albert Einstein published his General Theory of Relativity, which argues that gravity is bound up with the curvature of spacetime by matter (or its equivalent in energy). Expressed mathematically as a set of 10 highly complex, coupled, nonlinear partial differential equations, the theory predicts that a sufficiently dense body -- particularly a black hole -- would possess a gravitational field so strong that it would cause space to curve in on itself.

Solving the equations in their full generality (i.e. without restrictions placed on time or geometry) will be essential for understanding what happens when two black holes collide and coalesce, the behavior of a pair of spiraling neutron stars, or the inner collapse of massive stars when they run out of fuel.

For example, any disturbance to a black hole will cause it to oscillate and emit gravitational waves. A cataclysmic event, such as the collision of two black holes (theory and observations suggest that there should be a few black hole collisions within a detectable range each year), is predicted by the theory to send gravitational waves rippling through space. The resulting signal, though faint, should be detectable here on Earth by instruments slated for completion by the turn of the century.

The first test of Einstein's General Theory of Relativity (the bending of light by the gravity of a large mass, seen in a solar eclipse) was made by a team led by Sir Arthur Eddington, who became one of the strongest supporters of the new theory. But when it came to gravity wave s, Eddington was skeptical and reportedly commented, "Gravitational waves propagate at the speed of thought."

Eddington was not the only skeptic. Many physicists thought the waves predicted by the theory were simply a mathematical artifact. Yet others continued to further develop and test the concept. By the 1960s, theorists had showed that if an object emits gravitational waves, its mass should decrease. Then, in the mid 1970s, American researchers observed a binary pulsar system (named PSR1913+16) that was thought to consist of two neutron stars orbiting each other closely and rapidly. Radio pulses from one of the stars showed that its orbital period decreases by 75 microseconds per year. In other words, the stars are spiralling in towards each other -- and by just the amount predicted if the system were losing energy by radiating gravity waves.

Why Should We Care About Gravity Waves?

Gravitational wave astronomy could expand our knowledge of the cosmos dramatically. For starters, gravitational waves, though weakening with distance, are thought to be unchanged by any material they pass through and, therefore, should carry signals unalt ered across the vast reaches of space. By comparison, electromagnetic radiation tends to be modified by intervening matter. Aside from demonstrating the existence of black holes and revealing a wealth of data on supernovae and neutron stars, gravitational wave observations could also provide an independent means of estimating cosmological distances and help further our understanding of how the universe came to be the way it looks today and of its ultimate fate. Gravitational waves might unveil phenomena never considered before. Nature is smarter than any theorist trying to imagine or calculate what might be out there!

Some links for Einstein's Theory of Relativity: http://www.phys.unsw.edu.au/einsteinlight/jw/E=mc2_is_it_true.htm and http://www.phys.unsw.edu.au/einsteinlight/
about energy: www.albinoblacksheep.com/flash/honda

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Process 1

RELATIVITY GOES DIGITAL

Einstein's Challenge