
Originally Posted by
geoseph
Memory man siguro tawag ani bai, hehehe. Seriously now, kanang mga objects in outer space, puro mga past kana, kay lagyo man gyud kaayo.
Since light travels at a finite speed, it takes time for light from these celestial objects to reach us. For example, the sun is eight light-minutes away. What we see of the sun at any moment is the sun 8 minutes ago, since it takes light 8 minutes to travel from the sun to the earth.
Some celestial objects are so far away, like quasars, that what we see of these are what these actually were billions of years ago (they think quasars are baby galaxies). The astronomical telescope is thus, the closest thing we have to a time machine. It also gives us the opportunity to glimpse at the evolution of the universe.
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The slowing down of time is fact in nuclear physics. Subatomic particles that only get to live for a short time get to live longer if you accelerate these to speeds near that of light (in vacuum). This phenomenon is only observable to speeds very near that of light. Anything less is not readily measurable. Hence, everyday observations do not demonstrate this phenomenon.
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Some speculate that if time slows down as it approaches the speed of light (and stops at the speed of light), perhaps time can travel in reverse for an object, if its speed of travel is beyond that of light (theoretical particle called tachyons are postulated to travel only beyond the speed of light).
However, the speed of light cannot be achieved by objects (possessing rest mass), since mass also increases dramatically as its speed nears that of light. This means that it takes infinite energy (to move an infinite mass) to make an object travel at the speed of light (unless, of course, it was light in the first place).
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It may be “more possible” to “travel to the future,” than it is to “travel to the past.” However, you cannot come back.
Since time slows down if you travel near the speed of light (in this case, relative to Earth) for say, one year, such that you achieve a time dilation of 10%, then when you return, you would have only aged one year, while everyone else aged ten. You will, in effect, be going to a future nine years ahead.