Answer:conversion factor between time and distance. If you have a certain amount of time tt, you can calculate the corresponding amount of distance by multiplying it by cc.Note: I'm not talking about the distance any particular object travels in the time tt. If you have a car traveling at speed vv, you can find out how far the car moves in time tt by multiplying by vv, but that's not converting time into distance. The conversion is something more fundamental.The fact that time and distance can be converted into each other like this is one of the ways relativity changed our view of the world. One of its consequences is that speeds can now be measured as pure, unitless numbers. How so? Well, normally, we might measure distance in meters and time in seconds. So when you calculate a velocity as distance divided by time, you get an answer in meters per second. But because time can be converted into distance, now you can measure time in meters as well. So if you divide distance (in meters) by time (in meters), the meters cancel out and you get a pure number.As a pure number, c=1c=1. There are a few things that travel at speed 1, including light and gravity. Light was simply the first one that we discovered, which is the only reason cc is called the "speed of light."Once you see that cc is important for reasons having nothing to do with the fact that light travels at that speed, hopefully it seems less strange that it enters into the formula E=mc2E=mc2. Just as you can convert time into distance, you can also convert mass into energy. You just have to multiply by cc twice, not just once, to make the units work out.
Explanation:conversion factor between time and distance. If you have a certain amount of time tt, you can calculate the corresponding amount of distance by multiplying it by cc.Note: I'm not talking about the distance any particular object travels in the time tt. If you have a car traveling at speed vv, you can find out how far the car moves in time tt by multiplying by vv, but that's not converting time into distance. The conversion is something more fundamental.The fact that time and distance can be converted into each other like this is one of the ways relativity changed our view of the world. One of its consequences is that speeds can now be measured as pure, unitless numbers. How so? Well, normally, we might measure distance in meters and time in seconds. So when you calculate a velocity as distance divided by time, you get an answer in meters per second. But because time can be converted into distance, now you can measure time in meters as well. So if you divide distance (in meters) by time (in meters), the meters cancel out and you get a pure number.As a pure number, c=1c=1. There are a few things that travel at speed 1, including light and gravity. Light was simply the first one that we discovered, which is the only reason cc is called the "speed of light."Once you see that cc is important for reasons having nothing to do with the fact that light travels at that speed, hopefully it seems less strange that it enters into the formula E=mc2E=mc2. Just as you can convert time into distance, you can also convert mass into energy. You just have to multiply by cc twice, not just once, to make the units work out.