The best explanation I’ve seen for the conception of the distances of interstellar space is thus:
*The Hitch Hiker’s Guide to the Galaxy is a wholly remarkable book. It has been compiled and recompiled many times over many years and under many different editorships. It contains contributions from countless numbers of travellers and researchers.
The introduction begins like this: “Space,” it says, “is big. Really big. You just won’t believe how vastly hugely mindboggingly big it is. I mean you may think it’s a long way down the road to the chemist, but that’s just peanuts to space. Listen …” and so on.
(After a while the style settles down a bit and it begins to tell you things you really need to know, like the fact that the fabulously beautiful planet Bethselamin is now so worried about the cumulative erosion by ten billion visiting tourists a year that any net imbalance between the amount you eat and the amount you excrete whilst on the planet is surgically removed from your bodyweight when you leave: so every time you go to the lavatory it is vitally important to get a receipt.)
To be fair though, when confronted by the sheer enormity of distances between the stars, better minds than the one responsible for the Guide’s introduction have faltered. Some invite you to consider for a moment a peanut in Reading and a small walnut in Johannesburg, and other such dizzying concepts.
The simple truth is that interstellar distances will not fit into the human imagination.
Even light, which travels so fast that it takes most races thousands of years to realize that it travels at all, takes time to journey between the stars. It takes eight minutes from the star Sol to the place where the Earth used to be, and four years more to arrive at Sol’s nearest stellar neighbour, Alpha Proxima.
For light to reach the other side of the Galaxy, for it to reach Damogran for instance, takes rather longer: five hundred thousand years.
The record for hitch hiking this distance is just under five years, but you don’t get to see much on the way.*
– Douglas Adams, The Hitchhiker’s Guide To The Galaxy