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Pioneers 10 and 11, which preceded Voyager, both carried small metal plaques identifying their time and place of origin for the benefit of any other spacefarers that might find them in the distant future. With this example before them, NASA placed a more ambitious message aboard Voyager 1 and 2-a kind of time capsule, intended to communicate a story of our world to extraterrestrials. The Voyager message is carried by a phonograph record-a 12-inch gold-plated copper disk containing sounds and images selected to portray the diversity of life and culture on Earth. The contents of the record were selected for NASA by a committee chaired by Carl Sagan of Cornell University, et. al. Dr.
Wissen = knowledge
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The real value of the Drake Equation is not in the answer itself, but the questions that are prompted when attempting to come up with an answer. Obviously there is a tremendous amount of guess work involved when filling in the variables. As we learn more from astronomy, biology, and other sciences, we'll be able to better estimate the answers to the above questions. Many of these questions will be addressed in depth in future issues of .
NOTE: This section is about stellar-mass black holes. For information about black holes that measure in the billions of solar masses , see Active Galaxies & Quasars . There are many popular myths concerning black holes , many of them perpetuated by Hollywood. Television and movies have portrayed them as time-traveling tunnels to another dimension, cosmic vacuum cleaners sucking up everything in sight, and so on. It can be said that black holes are really just the evolutionary end point of massive stars .
Have you ever looked up at the night sky wondering where those elusive constellations are? Do you wonder what that really bright star (or planet) is called? With Stellarium , you will wonder no longer!
I have read a lot about Black holes and have gained wisdom of the subject. My question- are there such things as white holes- and if so- what do they do? Before I answer this question I would like to point you to Kate Becker's discussion of why it is so hard to understand the expansion of the universe.
A white hole , in general relativity , is a hypothetical region of spacetime which cannot be entered from the outside, but from which matter and light have the ability to escape. In this sense, it is the reverse of a black hole , which can be entered from the outside, but from which nothing, including light, has the ability to escape. White holes appear in the theory of eternal black holes . In addition to a black hole region in the future, such a solution of the Einstein field equations has a white hole region in its past. [ 1 ] However, this region does not exist for black holes that have formed through gravitational collapse , nor are there any known physical processes through which a white hole could be formed. Like black holes, white holes have properties like mass , charge , and angular momentum .
Stabilizing a wormhole with exotic matter In principle, a wormhole could be stabilized by threading its throat with `exotic matter'. In the stable wormhole at left, the exotic matter forms a thin spherical shell (which appears in the diagram as a circle, since the embedding diagram is a 2-dimensional representation of the 3-dimensional spatial geometry of the wormhole).