Word: problem
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Dates: during 2000-2000
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...human brain is the most complex object in the known universe, with billions of chattering neurons connected by trillions of synapses. No scientific problem compares to it. (The Human Genome Project, which is trying to read a long molecular sentence composed of billions of letters, is simple by comparison.) Cognitive neuroscience is arming so many brilliant minds with such high technology that it would be foolish to predict that we will never understand how the brain gives rise to the mind. But the problem is so hard that it would be just as foolish to predict that we will...
There are reasons to believe that these two problems are really the same problem. That is, we think that when we learn how to make a mathematically consistent theory that governs both gravitation and the forces already described by the standard model, all those seemingly arbitrary properties will turn out to be what they are because this is the only way that the theory can be mathematically consistent...
...problem with wormholes is that the openings are microscopic and tend to snap shut a fraction of a second after they're created. The only way to keep them open, as far as we know, is with matter that has negative density. In layman's terms, that's stuff that weighs less than nothing. This may sound impossible, but the Dutch physicist Hendrik Casimir theorized in 1948 that holding two plates of electrically conducting material very close together in a vacuum actually does create a region of negative density that exerts an inward pressure on the plates. The force predicted...
Stephen Hawking has addressed the problem in a different way, proposing what he calls a chronology-protection conjecture. Somehow, he argues, the laws of physics must always conspire to prevent travel into the past. He believes that quantum effects, coupled with other constraints, will always step in to prevent time machines. The jury is still out on this question. We may need to develop a theory of quantum gravity to learn whether Hawking is right...
...might think that bolting the two plates together would fix the problem or at least buy a little time. But given the forces involved, holding the San Francisco Bay Area together for even a brief period of time would require bolts the size of the World Trade Center towers--an engineering feat that not even a modern-day Pharaoh could afford...