Published: 2 May, 2001

Sun could fit 1 million earths

How many earths will fit in the sun?

How many earths would fit inside the sun? This is a very good question because it gives exactly the terms in which the answer should be put. This is a good instinct, because often people who want to convince us of something will give numbers to impress us and sometimes we forget to ask ourselves how big these numbers really are in terms of something that we understand. For instance, if someone points out that in 1991, 74 people died while sky diving, it may sound like a very, very dangerous activity. But, what is the point of reference? In fact, this was out of 5 million sky-dives. If someone took one sky-dive, he or she would have been 10 times more likely to die in an automobile accident during that same year.

Turning now to the sun and earth, the quickest answer to the question is to divide the volume of the sun by the volume of the earth, to find an answer of 1.3 million earths. Indeed, the sun is quite large. But, here we have only thought about the volume, which means: to fit this many earths, we will have to break them all up and crush them together to remove all of the extra spaces in between. If, instead, we decide to pack the earths carefully inside the sun without breaking any, then we will always be left with some extra spaces in between, as when stacking marbles or cannon balls. Nature has taught us the most efficient arrangement for such stacking. The atoms in metals like copper, silver and gold are packed in the best possible arrangement, something called "close packing". Even with this close packing, still about 26% of the space always goes to waste. So, in the end, we will only be able to fit about a million earths inside the sun. Keep in mind, though, that after all of this careful packing, all of these millions earths will quickly burn up into something called a plasma.