The Earth is a ball of rock. About three quarters of its surface is covered by ocean. Walking around the Earth would be like a centimetre-tall man walking across England.
This is but a tiny distance in the grand scheme of things.
If the Earth were the size of a person's head, the moon would be a tennis ball at the other end of the garden, moving around your head once every month. Meanwhile, your head is going around the Sun - a fireball the size of your local park - taking a year to get back to where you are now. The Sun you are orbiting is ten park-lengths away from you. Mars - smaller than your head but larger than the tennis ball moon - is also going around the Sun, but a few park-lengths further away from it than you are. It has a couple of moons going around it in the same way that our tennis ball moon orbits your head once a month.
This is still just small-scale stuff.
Now suppose the Sun is a tennis ball. The Earth - only a millimetre across - is about a metre away, going around it once a year. Mars - a speck of dust - is about one and a half metres away from the tennis ball Sun, going around it once every two years. The moons of Earth and Mars are too small to see. So is scorched Mercury, which is closer to the tennis ball Sun than the Earth. Cloudy Venus is between us and Mercury. All the planets go around the Sun at different speeds. Five metres from the tennis ball Sun orbits Jupiter, the size of a marble - huge compared to the millimetre Earth. Jupiter has lots of moons, including four that are fairly large (though still too small to see on this model). One, Io, has active volcanoes. Another, Europa, is covered with ice, beneath which may be warm oceans where alien life-forms might have evolved. Ten metres from the tennis ball Sun orbits Saturn, a slightly smaller marble. Both Jupiter and Saturn are gas giants. Only moons and small planets like the Earth can have solid surfaces. Saturn has rings made up of little fragments of rock and dust. It also has moons. More than thirty metres away is Uranus, and further still Neptune. Both are gas giants, smaller than Saturn but much larger than the Earth. Even further away, and in a band between Mars and Jupiter, are countless asteroids, also orbiting the Sun.
This is still only a drop in the ocean.
If the Sun is a millimetre across, the Earth orbits a centimetre away from it, Jupiter five centimetres away, Saturn ten. Twenty kilometres away from our millimetre Sun is the next nearest millimetre sun. It appears as a pinprick of light in our night sky. There are more than a hundred thousand million stars like this, similarly spaced, in the one huge rotating disc we call our Galaxy. Some are much larger and brighter than our own Sun, but only appear as dots in the night sky because they are so far away. Others are much smaller and dimmer. Many could have planets going around them like Mars, Jupiter and Earth, and planets around other stars could support all kinds of alien life.
And there are billions of galaxies outside our own.
(a) A 2.5 light-years wide view of the Orion Nebula. (b)The Eagle Nebula - 7,000 light-years away. Credit: M. McCaughrean, C.R. O'Dell and NASA / J. Hester, P. Scowen and NASA.
The furthest a human being has been is to the moon, which is so close to us that it vanishes when we shrink the Sun to a tennis ball. We only discovered the true nature of the planets a few centuries ago. Before the invention of the telescope we thought everything went around the Earth. Now we know that the Earth and the other planets go around the Sun, which is just one of millions of stars going slowly around the centre of the Galaxy. Only since the last century have we had good and clear pictures of planets like Jupiter and Saturn, their colourful moons, distant galaxies and nebulae. Only in the last few decades have we obtained photographs from the surfaces of the moon and Mars.
The Earth has existed for four and a half billion years. If the Earth's history is scaled down to one day, man has only walked its surface in the last second before midnight. Hence my view that people take themselves too seriously. (See top of section.)
So the next time you get stressed about something, and your worries start to take over your life, just remember that whatever happens, the universe at large will go on just fine. When you look at the universe with the Sun shrunk to one millimetre across, the Galaxy of stars still stretches on for as far as the eye can see, but Earth and human concerns have been reduced to nothing. Wars over who controls land, national pride, sport, academic prestige... to the universe at large these concepts are so trivial that their very existence borders on the ridiculous. So rather than lose sleep over such things, be content with the hand life has dealt you, and go feed the ducks.