tagged w/ Spacetime
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General and special relativity are two of the more mind bending theories in modern science. According to them, space and time are a singular entity that is warped by mass, where measurements completely depend on how the person doing the measuring is moving. People generally believe that relativity has no effect in everyday life, since it's generally discussed in terms of things going very fast or objects in highly warped spacetime.
This belief is not entirely true—GPS equipment would not work if the times measured by the satellites were not corrected for time dilation that arises from the rapid motion of the satellites relative to your car. In general, though, most people go about their day without experiencing any ill- (or odd-) effects due to relativity. However, it turns out that, if you can measure accurately enough, the effects of relativity are indeed all around us.
Using the most accurate clocks in existence, a team of researchers at NIST in Boulder, CO have shown that relativity all around us—even on everyday lab scales. The team used an optical "quantum logic clock" that is based on an electron's oscillations between the 1s and 3p quantum energy levels of an 27Al+ ion. A pair of these clocks—each of which will lose less than one second every 3.7 billion years—were tethered together by a special optical cable connecting two adjacent labs. The clocks were then manipulated so that time dilation occurred.
The first experiment had one clock moving relative to the other, a situation that is used to introduce the concept of time dilation to introductory physics students—faster moving clocks will tick away more slowly. In this case, one clock's ion was put in motion relative to the other, and the frequency shift that resulted was measured. Even when the clocks were moving apart at 22.4 miles per hour, it was possible to observe a change in frequency of approximately 45x10-17. This is exactly in agreement with the predictions of special relativity.
A lesser known consequence of general relativity is that time will move slower in a stronger gravitational field. On Earth, one implication of this is that a clock on the second floor of an office building will move faster than one on the first floor. Using the ultra-precise clock setup, the NIST researchers tested this as well. One of the optical clocks was placed about a foot above the other and measurements were taken. They found a fractional frequency change of (4.1±1.6)x10-17; plugging this number back into relativity's formulas produced an equivalent height differential gave 14.5±5.9 inches, a result that nicely bracketed the 12 inch difference in the experimental setup.General and special relativity are two of the more mind bending theories in modern... more
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the relativity theory is yet unfinished. this is the root of the crisis which now happens in physics. with the accomplishment of the theory we may reveal the underlying reality of multidimensional worlds.the relativity theory is yet unfinished. this is the root of the crisis which now... more
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A wormhole exists at the center of a black hole. Wormholes would allow travel from one part of the universe to another part of that same universe very quickly or would allow travel from one universe to another. All around us are tiny doors that lead to the rest of the Universe. Predicted by Einstein's equations, these quantum wormholes offer a faster-than-light short cut to the rest of the cosmos - at least in principle. Now physicists believe they could open these doors wide enough to allow someone to travel through. http://www.makeahistory.com/index.php/submit-an-article/364-wormholeA wormhole exists at the center of a black hole. Wormholes would allow travel from one... more
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worrg
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added this
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2 years ago
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A rising star in theoretical physics offers his awesome vision of our universe and beyond, all beginning with a simple question: Why does time move forward? In January, Caltech physicist Sean Carroll will release his much-anticipated debut book, From Eternity to Here: The Quest for the Ultimate Theory of Time. SciFi buffs will grok out on his thesis that our perception of time is informed by entropy — the level of disorder in a system. The basic laws of physics work equally well forward or backward in time, yet we perceive time to move in one direction only—toward the future and that the movement from low to high entropy as the universe expands establishes the direction in which time flows. To account for it, we have to delve into the prehistory of the universe, to a time before the big bang. Our universe may be part of a much larger multiverse, which as a whole is time-symmetric.
Time may run backward in other universes. Some universes, he argues, don’t experience time at all; once a universe cools off and reaches maximum entropy, there is no past or present.
Here's how Carroll describes his thesis: "Microscopic laws of physics are essentially time-reversal invariant, but macroscopic thermodynamics exhibits a profound time-asymmetry; entropy typically increases in closed systems. This intriguing feature of the real world has a cosmological origin: the entropy of the early universe was fantastically small. After a century of effort, it has been difficult to explain this arrow of time without assuming time-asymmetric boundary conditions. Jennifer Chen and I have suggested a simple scenario in which increasing entropy is natural, based on the idea that the entropy can increase without bound (there is no equilibrium state) and that the way entropy increases is by creating universes like our own. In our picture, any generic state first evolves to an empty de Sitter phase; the small temperature of de Sitter allows for fluctuations into a proto-inflationary configuration, which grows and reheats into a conventional Big-Bang spacetime. The same thing happens in the far past, but with a reversed arrow of time. On ultra-large scales, therefore, entropy is growing without bound in the asymptotic future and past."A rising star in theoretical physics offers his awesome vision of our universe and... more
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