It looks like you're using an Ad Blocker.
Please white-list or disable AboveTopSecret.com in your ad-blocking tool.
Some features of ATS will be disabled while you continue to use an ad-blocker.
Originally posted by jkrog08
reply to post by Kruel
That should clear it up for you,relativity is a very confusing subject.Stars light is observed from light from the past because the distance traveled takes even light time to arrive at Earth.BTW,what is that supposed to be on your avatar?
Relativity, and How it Affects Human Space Exploration and Travel
Some of the most complex theories in physics have to do with the study of relativity. The general principle of relativity states that in all frames of reference, the physical laws remain the same. Galileo Galilei described the principle of Galilean relativity in 1632, in his book Dialogue Concerning the Two Chief World Systems (Dialogo sopra i due massimi sistemi del mondo). In it, he theorized that in all "inertial frame of reference" (which is a frame of reference where Newton's first law of motion -which states that an object at rest will remain at rest and a moving object will continue moving at a constant speed unless acted on by a net force- holds true), the fundamental laws of physics all hold true. Once example of this is the fact that although the Earth is moving around the Sun, we cannot tell without looking at things that do not move like we do. Then, in 1908, Albert Einstein, with the help of Hendrik Lorentz and Henri Poincaré, published a paper called "On the Electrodynamics of Moving Bodies", in which he proposed the special theory of relativity. This dealt with measurements in inertial frames of reference. This theory is where the mass-energy equivalence equation (E=mc²) is derived. One of the many things the theory does is contradict the Newtonian notion of "absolute" or "universal" space and time, stating instead that observers moving differently perceive time and space differently. Another is show that c, the speed of light in a vacuum, is not just the speed that light travels in a vacuum, but a fundamental feature of the way that space and time interact and are joined as spacetime. This means that no particle with mass can travel at or faster than the speed of light. These two components of the special theory of relativity will greatly affect the future of human space exploration and travel. Space is big. Really big. This is the greatest problem with our exploration of space is that things are very far away, and our tools for exploration move very slowly. Voyager 1, launched September 5, 1977, and as of May 9th of this year had traveled over 15.89E12 meters (14.72 light-hours) from the sun, and that's with gravity-assisted speed boosts. Voyager 1 is expected to have enough power to communicate with Earth through 2025. Although it will not be able to communicate with us, Voyager will continue to travel due to the principle of inertia. But we will never know what Voyager encounters after it loses contact with us. At it's rate, a journey to the nearest star to the sun, Proxima Centauri, would take 72,000 years. It will be very difficult to actually explore space with the current technology. And even if we could keep probes transmitting for much longer the projects may never be able to take place because the cost would be hard to justify. Finding financial justification for a project that may not yield results for decades, centuries, even millennia, would be near impossible. Even on a smaller scale it is difficult to explore just our solar system, simply because of the length of time it takes to get probes anywhere. Just to get to Mars takes about six months. This also affects travel and colonization. If a colony on Mars were established, in the event that anything was needed from Earth, it would take six months for it to get there. So in order for space exploration and travel to be effective, we need to be able to go faster. But it is more than just technology that limits how fast we can go. Special relativity does that too. Special relativity shows that no particle with mass can travel at or faster than the speed of light. One of the reasons that faster-than-light motion is prohibited is casuality, or cause-and-effect. If two events (One and Two) occur simultaneously in a frame of reference, but are separated by space, there are frames of where one occurs before the two, and frames where the two occurs first. So if event one causes event two, there are frames of reference where the cause occurs before the effect. If faster-than-light motion could be obtained, one could send signals into one's own past, contradicting casuality. If casuality is to be preserved, matter or information cannot travel faster than light. So we cannot travel faster than light. But if there if we could find a way to travel at speeds closer to the light speed we would still have a problem eventually. Although speeds closer to the speed of light would make exploration and travel in our small section of space very effective and efficient, it still would make exploration and travel farther away from us hard. The closest star to the Sun, Proxima Centauri, is approximately 4.22 light-years away. With the best technology we currently have, nuclear pulse propulsion, it might be possible to reduce travel time to Proxima Centauri to a century or less. For humans, that's quite a while. The best possible candidate for a terrestrial planet outside our solar system is Gliese 581 d, which is about 20 light-years from the Sun. So even if someday we manage to travel any where close to the speed of light, it would still take over twenty years to travel to Gliese 581 d. If someday in the far future we would ever chose to send a manned mission to the planet, one would think that the crew members would age so much on the mission that it may not be possible. And that's where another consequence of the theory of special relativity comes in: time dilation. Time dilation is phenomenon associated with special relativity. Time dilation, which has been experimentally proven, shows that time passes differently for things moving at different speeds. This is often illustrated by a thought experiment called the "twin paradox". In it, there are a pair of twins. One twin gets on a space ship and makes a journey into space at a very high speed. The twin returns from the journey to find that he or she or has aged less than the other twin has. More time has passed for the Earthbound twin than for the traveling twin. Time dilation could make it possible to send manned missions far away from Earth without the crew members aging so much. Although the time on Earth would pass "normally", to the crew members, the journey would be much shorter. Missions to places many light-years away may mean that much time will have passed on Earth, but the crew members would not die of old age like one might think. Of course, in order for the time difference to be effective enough, the crew would have to be traveling extremely fast. With today's technology, humanity is very limited. Limited by space and time, by age, by death, by technological breakdown. But if we could develop a way to travel fast, closer to the speed of light, the limits may fall away, and the universe would lie open to us- we could explore and travel farther than the imagination. There is a beautiful universe just waiting to whisper its secrets in humanity's ear. All we have to do is move fast enough to hear them.