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Einstein’s theory of relativity states that nothing can exceed the speed of light, leading to definite areas of the universe that can and cannot be affected. These areas are within our past and future light cones, with everything else in the “otherwhen.” Even with the ability to travel at the speed of light, there are many places in the universe that we could never reach.
According to Einstein’s theory of relativity, nothing in the universe can exceed the speed of light (300,000 km/sec or 186,000 miles/second). This “universal speed limit” has all sorts of implications. One such implication is that every object in the universe has definite portions of the universe that it can and cannot affect within a given period of time.
Let’s see an example. On average, the sun is 150 million kilometers from the earth and light takes about 8 minutes to make the journey. Therefore, even at the speed of light, I cannot reach the surface of the sun in less than 8 minutes. Those areas which cannot be reached or influenced within a certain time period are said to be in the other when.
We think of time linearly, with the future stretching out before us and the past behind us. Those areas of the universe that we could theoretically have had an influence on are said to be within our past light cone. Those areas over which we can have an influence (if we could travel at the speed of light) are said to be in our future light cone. Nothing in the past or future cones of light is said to be in our “locality”; everything else is in the otherwhen.
If you live to be 100, there are many places in the universe that you could never reach even if you could travel at the universal speed limit and even if you devoted your entire life to travel. In fact, even if you could live for thousands of years and find a rocket capable of traveling at the speed of light, you would only be able to reach an infinitesimal portion of the known universe.
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