NASA - 2012: answers
Simple questions - simple answers (Beware of "scientific" arguments!) Lightspeed, Hyperspace and Wormholes Question: My name is Yoga, I live in Indonesia and am 12 years old. I am interested by science fiction movies, especially about star travel, such Star Trek, Babylon V, and so. When I saw those movies, there was always something that confused me so much. What's the differences between LIGHTSPEED, HYPERSPACE and WORMHOLE? I can understand about light speed, but I don't know if a wormhole could be used in space travel. As far as I know, quantum theory was just used to prove other dimensions of our world (parallel worlds), so is there any connections here between this wormhole and space traveling? Well, Mr. Stern, I think these are the questions to which I'd like to know the answers. Can you please help me? Reply: Dear Yoga, The stories of science fiction movies come from professional writers, not from scientists. About 100 years ago Einstein found (something confirmed since then in many ways) that no material object can move faster than light, 300,000 kilometers per second. (If YOU moved that fast, time would pass at a different rate, so TO YOU the speed might seem greater--but not to someone in the outside world). Writers of fantasy stories, and later of fantasy movies, felt restricted by that fact, which suggested that back-and-forth travel or communication with civilizations on planets outside the solar system was impossible on the short time scale of travel and communications between countries on Earth. As seen now, a projected trip to another world (even using technology we do not have yet!) might take many thousands of years. So writers picked up some scientific terms, suggesting some day in the future the limitation of light speed may be overcome, by using hyperspace or wormholes. However, these are just ways for literature and films to imagine things which physics says (at least right now) cannot be done. I am not sure about wormholes, which have to do with general relativity: the added dimensions proposed by some theories extend only a very short distance into our universe, and are not likely to help us navigate the three principal dimensions of our universe (or 4--though time is a different kind of dimension) If you like science fiction, you might look up "Flight of the Dragonfly" by Robert Forward for a physically acceptable way (though one technologically extremely difficult) of flying to a nearby star. What is precession and does it change the Length of the year? I've enjoyed your page on the precession of the equinoxes at: I understand that a year is the time between two successive vernal equinoxes. In a year the earth will have orbited around the sun and the earth's axis will have precessed a very little bit so that both the orbit around the sun and the precession of the earth's axis go together to make up the length of time between two successive vernal equinoxes. Now suppose the earth's axis were not precessing. How long would a year be? How much does the precession of the earth's axis affect the length of a year? Thank you for your attention and any information will be greatly appreciated. Reply Dear Gary,Let's first try a simple minded approach. The phenomenon is called PREcession, so the spring equinox moves to a point a little EARLIER in the Sun's journey around the zodiac. The location of the spring equinox makes one circuit of the zodiac in 26000 years. Therefor, if the spring equinox did NOT move to intercept the Sun on its trip around the sky, the year (equinox to equinox, say) would be about (365 x 86400)/26000 seconds longer, or about 20 minutes. But it's more complicated. What year do you have in mind? A CALENDAR year extends from equinox to equinox, or from solstice to solstice. Most people want holidays to stay with the right seasons, not migrate between summer and winter (as Moslem ones do). If the precession were to stop, the year in which holidays kept a fixed position that would be 20 minutes longer. On the other hand, if your field is celestial mechanics or astronautics, "a year" is presumably the EARTH'S ORBITAL PERIOD around the Sun. The orbital period does not depend on which way the Earth's axis points in the sky--it is always the same, precession or no precession (and it hardly varies over millions of years). So it is always the longer of the two preceding ones. A similar analogy holds for the day. Is it NOON TO NOON (24 hours average) or is it the ROTATION PERIOD of the Earth around its axis? The latter is 4 minutes shorter, because "noon to noon" includes a small contribution from the shift of the Sun's position in the sky, about one degree per day. Ask a simple question... sorry about the complicated answer! Planetary line-up and the sunspot cycle Enjoyed browsing through some of your efforts on the Web. I am hoping you could help settle some of my thoughts before I make a fool of myself. In your experience, has anyone tried to correlate lineups of the sun, earth and major planets' magnetospheres with the sunspot cycles? My spare-time effort found some correlation between lineups and cycles in a number of years. My wonderment centers around the possibility that some forces of the planets when lined up, possibly relating to their magnetospheres, impact the suns magnetosphere causing a solar max. I've also considered the possibility that related magnetosphere effects could be the cause of previous polar reversals on the earth. Additionally, ringing of our magnetosphere might impact charged tectonic plates...but that is again another direction. Only if you have time, please comment. Reply: There exists a tempting closeness between the length of the solar cycle and the orbital period of Jupiter, but I don't think the two are related. I cannot imagine any mechanism coupling the two-- especially since the Sun rotates in about 27 days, so the relative period of Jupiter going around the Sun is of that order. Furthermore, the solar wind moves with supersonic speed, which means that solar disturbances can (and do) travel downstream with it, but disturbances from a planetary magnetosphere (whatever they might be) don't easily propagate sunward. Above and beyond all these, there is always the question of energy-- the currency in which the price of any physical process must be paid. The energy required in the solar cycle is much bigger than anything planetary magnetospheres can supply. So what causes the cycle? The Sun rotates unevenly, slower near the poles, faster near the equator, probably because of the way gas flows in it (Jupiter also has such a difference). In a magnetized hot gas, this difference deforms and amplifies the magnetic field, and there exist some general theories of the sunspot cycle based on this, although many details remain unclear. The general idea is that as the magnetic field gets amplified, it forms concentrated "ropes" which push out the hot gas, and when they reach a certain strength, enough gas is displaced that the ropes are light enough to float to the surface, where they are seen as sunspots. Again, the magnetosphere is a relatively weak influence on the Earth's internal magnetism--even a big magnetic storm only reduces the surface equatorial field by 1%. Furthermore, the time scale differs--reversals happen on time scales of 0.5-1 million years, while magnetic storms have a 1-day scale or faster. What seems to be involved are the currents which circulate in the Earth's core, presumably driven by flows there, which (like flows on the Sun) get their energy from heat. The magnetic field is fairly complicated--the 2-pole structure we see (north-south) is dominant, but not by as much as it seems, because more complicated modes get filtered away faster by distance. Right now the 2-pole field is declining at about 5-7% per century, but the late Ed Benton has shown that the more complex parts are gaining energy, and the total sum is fairly constant. Maybe, when a reversal occurs, for a while the 2-pole part gets small and the total field is rather complex (4, 8 poles..), and when the simple pattern re-emerges, it is reversed.
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