People are quite good at estimating various things. To demonstrate what I mean, try answering the four following questions. How long does it take an average person to walk half a kilometre? Approximately how many eggs fit into small box? How much taller is an adult person compared to a six-year-old? What is the average difference in temperature between summer and winter? It is very likely that your answers to the questions above were to some extent correct.
Everybody knows that an ordinary human walks a distance of a few hundred meters in a couple of minutes, that about five to ten eggs fit into a small box, that a child is about two or three times smaller than an adult, and that the difference between summer and winter temperatures is several dozen degrees at most. No reasonable person would tell you that they can walk half a kilometre in about a tenth of a second, that about a billion eggs fit into a box, that a twenty-year-old is about a hundred thousand times larger than a child or that the temperatures in summer can be up to a million times greater than those in winter. Our brains are excellent at estimating these things, since we encounter them on a daily basis.
But once we get over the border of the ordinary world, our perspective suddenly vanishes. How many atoms fit into the dot of the question mark at the end of this sentence? How much farther from Earth is the Sun compared to the Moon? What is the difference in temperature between the Sun’s core and its surface? If you have not happened to learn the answer to one these questions, you might not be able to respond. And if you have at least tried, it is very likely that your answer is far off from reality. Our brains do not encounter atoms or stars on a daily basis, which makes answering these questions immensely difficult for them. The aim of this chapter is therefore to bring a little bit of perspective into the mysterious world of the cosmos.
Keishinrei 