Travelling at Light Speed
Date: 04/11/98 at 16:20:00 From: Mr. DEAN LOWELL CRUMMY Subject: LIGHT TRAVEL How long in time, not distance, would it take to go to Mars or Jupiter? At light speed?
Date: 04/13/98 at 09:48:19 From: Doctor Barrus Subject: Re: LIGHT TRAVEL Hi, Dean! It depends on how far away from Mars or Jupiter the earth is. The earth, according to: http://www.star.le.ac.uk/espace/Planets/relativep.html is located an average of 150 million kilometers away from the sun, and Jupiter and Mars are at average distances of 780 and 228 millions of kilometers away from the sun, respectively. But every planet is revolving around the sun, and at different rates, so the distance from planet to planet is constantly changing. So, assuming that the sun, the Earth, and Mars were all lined up (which they're not), you could have Mars and Earth as close together as (228 - 150 =)78 million kilometers ... <---------------228----------> (Sun) * * Earth Mars <------150----------><---78--> ... or as far apart as (228 + 150 = )378 million kilometers: * (Sun) * Mars Earth <---------228-----------><----150-------> Similarly, distances between Earth and Jupiter could be anything from around 630 million kilometers to 930 million kilometers. Of course, these calculations aren't exact, because the two planets and the sun rarely line up like in the diagrams above, and the distances I used are just average distances -- the planets can be closer to or farther away from the sun. I just gave the example above so that you could see that the distances can really vary. But let's suppose that we know the exact distance between the earth and another planet. Then to find out how long the trip would be, we'd use the formula distance = speed * time to get distance time = ---------- speed So, suppose the Earth and Mars are 200 million kilometers away from each other right now. Then a trip to Mars would take time t, where t = (200 million kilometers)/(speed of light) = (2 * 10^11 meters)/(3.0 * 10^8 meters per second) [Here, I just converted the kilometers into meters (using the fact that there are 1000 meters in a kilometer), wrote the distance in scientific notation (so it's easier to calculate), and wrote out approximately what the speed of light is.] So: t = 667 seconds (approximately) which translates to 11 minutes and 7 seconds. (NOTE: This is how long someone on *earth* would see the trip as taking. A person actually on the ship to Mars, traveling at the speed of light, wouldn't be aware of ANY time passing. This would happen because of the phenomena that Einstein explained in his theory of relativity.) So in summary, it isn't possible to answer your question exactly, because the distances between earth and Mars and Jupiter are always changing, and therefore the times required to travel to them at light speed also change. If we did know the exact distance, though, we could figure out approximately how long a journey of that kind would take. -Doctor Barrus, The Math Forum Check out our web site! http://mathforum.org/dr.math/
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