Dark Physics Quiz | Physics

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1. There is nothing, truly nothing. No matter or energy, neither time nor space. And then, in an instant, there is a flood of... something - exploding, expanding, taking on shape and structure, generating the very laws of the universe. Had there only been someone there to hear, what they might have called it?

Answer: The Big Bang

What was present prior to the Big Bang? Most cosmologists argue that since time, space, matter and energy all began with the Big Bang, there WAS no before, and that therefore, even the question "What came before" is meaningless. Still there are other scientists who will speculate on this subject.

Some believe in the Big Crunch and theorize that through an infinity of time the Universe has been expanding to a limit only for gravity to draw it back into a point where the Big Bang occurs again. Some string theorists speculate that a collision with a parallel universe triggered the Big Bang.

2. The chaos coalesces. Gravitational attraction brings tiny bits of matter together. But there are points at which there is neither matter nor electromagnetic radiation. Still, a strange quantum-mechanical potential lurks there. Which of these could it be?

Answer: Zero point energy

The zero point or quantum vacuum is a particle free area in which the lowest energy state has been reached. But of course, this does not necessarily mean that no energy is there. A quantum view sees particles and antiparticles periodically arising out of the apparent nothingness and annihilating one another... or almost annihilating one another.

This being a quantum view, a little energy occasionally manages to escape. When one carefully measures the attraction between two metal plates at temperatures approaching absolute zero, this energy is unmasked as the Casimir force.

3. On a tiny blue planet orbiting a seething gaseous ball, somewhat intelligent life notices a baffling phenomenon. When they take an empty box and punch a hole in it, radiation streams out from the black interior of the empty box. What name is given to this radiation?

Answer: Black Body Radiation

A dark box or cavity has the properties of a black body. It should be unsurprising that in the world of physics a "black body" placed in a dark room radiates energy. One of the ways in which the "classical" physics of the 18th and 19th century broke down was in its inability to account for the spectrum of black body radiation. Max Planck's equation for black body radiation is held to by many to be the starting point of modern quantum physics.

4. Other denizens of the small blue planet occupy their time with attempting to suck every last molecule out of closed containers to produce a perfect vacuum. Which of the following are examples of a truly perfect vacuum?

Answer: Neither

Should that last stubborn molecule be sucked out of a closed container, its temperature would not be zero and the container would not be entirely empty. Photons would continue to be released and reabsorbed from the walls of the container. Deepest space still contains the background radiation from the Big Bang. True nothingness might have existed prior to the Big Bang, but even this is speculation. Perhaps at this point, we should consider Aristotle's view on the existence of a vacuum. Since the absence of everything defines "non-existent", then the void (vacuum) could not exist in physical reality.

5. Stars form. Stars age. And as the larger stars age, they exhaust their fuel until finally one force predominates: gravity. These stars collapse on themselves, becoming ever smaller until their density is so high, their gravitational force so great, that nothing, not even electromagnetic radiation, can escape their grasp. When the inhabitants of our small planet conceive of these holes in the sky, what do they come to be called?

Answer: Black holes

British geologist John Mitchell imagined the existence of an object dense and massive enough so that its escape velocity exceeded the speed of light. He concluded that "all light emitted from such a body would be made to return towards it by its own proper gravity." So theorized John Mitchell in 1783. However, the verification of the existence of black holes has proved to be a more complicated matter.

American physicist John Wheeler coined the term "black hole" in 1964. In 1970 Stephen Hawking laid out the physics of the black hole, and in the same year, astronomers observed a candidate object in the constellation Cygnus. The Hubble telescope has identified other black hole candidates, and the existence of black holes is widely accepted, although not considered entirely proven (see http://physics.uoregon.edu/~jimbrau/astr122/Notes/Chapter22.html#bhole).

6. The creatures of the little blue planet have fertile imaginations. They can, for instance, imagine an infinity of nothing, a place with infinite volume where there is neither matter nor energy. And having imagined such an absolutely desolate place, what temperature do they assign to it?

Answer: Absolute zero

Even in deepest space, the temperature hovers at approximately 3 degrees Kelvin above absolute zero, a fact attributed to leftover microwave radiation from the Big Bang. Achieving a temperature of absolute zero would require the exclusion of all matter and energy from a fixed volume of space, a feat considered by most to be a practical impossibility.

In fact, some consider there to be a "Third Law of Thermodynamics" that forbids the achievement of absolute zero.

7. As the beings of the small planet turn their attention to things ever smaller and more insubstantial, they cannot but succumb to the temptation to make analogies between the behavior of the larger things they can see and the smaller things they cannot. Thus, they come to believe that just as ocean waves are oscillations in a sea of liquid water, so light must oscillate in its own vast sea of "luminiferous ether". Which scientist showed that light and other electromagnetic waves could propagate in nothing?

Answer: Einstein

An interesting feature of physics is the frequency with which theory drives discovery. The existence of black holes is first conceived, next their characteristics are predicted, and then physicists go looking for them in real world. In this way, classical physicists of the 19th century came to postulate the lumineferous ether, the substance in which electromagnetic radiation was propagated. According to Einstein, Newton's framework was "probably the greatest stride ever made in the effort towards the causal nexus of natural phenomena." Yet Newton's theories, which required action at a distance, conflicted with everyday life, in which interaction always sprung from immediate contact. Einstein maintained that the path taken to rectify this disparity "leads to the hypothesis of an ether." (Einstein, address delivered on May 5th, 1920, in the University of Leyde, http://www.tu-harburg.de/rzt/rzt/it/Ether.html)

8. Peering through their telescopes into the void, observers on our little blue world have watched the galaxies in their dance and concluded that 96% of the universe's mass is invisible. So now, in Cleveland, England, at the bottom of Europe's deepest mine, in a deep mine in Minnesota, and in a tunnel under Stanford University, detectors sit. They wait for a neutralino, for a WIMP, for a Nobel Prize. What are they hoping to detect?

Answer: Dark matter

Scientists have mapped the pattern of residual energy from the Big Bang (the Cosmic Background Radiation). From this they have inferred that only 35% of the total mass and energy of the universe is accounted for. Worse, they have detected only 5% of the 35%, the other 30% being dark matter, evidence of which scientists eagerly seek in mines and tunnels. Names proposed for particles of this as yet undiscovered matter include "neutralino" and "WIMP", the latter an acronym for "weakly-interacting massive particles".

Many believe that a Nobel Prize awaits the one who first finds credible evidence of dark matter.

9. As the power of their telescopes increases, the inventive folk of the little blue speck in the void notice that not only do the galaxies seem to be spreading out and moving away from one another but that the galaxies farthest away seem to be moving away faster. One possible explanation for this is that matter carries only 1/3 of the mass of the universe while a type of energy carries the rest. Since this energy is at present undetectable, what has it been called?

Answer: Dark energy

Since even detectable matter and dark matter combined account for only 35% of the universe's expected mass, the other 65% has been assigned to "dark energy". Scientists expect energy to be so thinly spread that the only possibility of detecting it would be to find it in deep space. According to current theories, the distribution of the universe mass is as follows: dark energy 65%, dark matter 30%, free hydrogen and helium 4%, stars 0.5%, ghostly neutrinos 0.3%, heavy elements 0.03%.

10. The scientists inhabiting the little blue planet conclude that their universe must suffer one of three fates: implosion (The Big Crunch), infinite expansion in a plane or infinite hyperbolic expansion. The value of a certain constant, they theorize, will determine the universe's fate. What has this crucial constant been named?

Answer: The cosmological constant

In 1917, Albert Einstein constructed his general theory of relativity, which included the constant lambda that came to be known as the cosmological constant. Originally postulated as a means to balance gravity and allow for a static universe, this constant remained in use even after the universe was observed to be expanding steadily.

In 1997, observations of a distant supernova confirmed that the universe is not only expanding, but that the rate of expansion is increasing. Scientists now theorize that because dark energy offsets gravity the cosmological constant is exactly one and that therefore, the universe is flat and will expand forever.

Source: Author uglybird

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Dark Physics Trivia Quiz

Some physicists seem obsessed with ... well...nothing - with empty, vacuous blackness and the things that arise from it. Enter the world of dark physics. And don't a-void the seemingly obvious answers. They're probably correct.

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