You Are Here
This is a section of an image from Nasa's Planetary Photojournal Catalog Page (you can get the full version there in a variety of sizes and formats). It was taken from the Voyager 1 spacecraft when it was over 4 billion miles away from Earth.
See the tiny dot about halfway down the reddish streak on the right? That's the Earth.
We succeeded in taking that picture [from deep space], and, if you look at it, you see a dot. That's here. That's home. That's us. On it, everyone you ever heard of, every human being who ever lived, lived out their lives. The aggregate of all our joys and sufferings, thousands of confident religions, ideologies and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilizations, every king and peasant, every young couple in love, every hopeful child, every mother and father, every inventor and explorer, every teacher of morals, every corrupt politician, every superstar, every supreme leader, every saint and sinner in the history of our species, lived there on a mote of dust, suspended in a sunbeam.
The earth is a very small stage in a vast cosmic arena. Think of the rivers of blood spilled by all those generals and emperors so that in glory and in triumph they could become the momentary masters of a fraction of a dot. Think of the endless cruelties visited by the inhabitants of one corner of the dot on scarcely distinguishable inhabitants of some other corner of the dot. How frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds. Our posturings, our imagined self-importance, the delusion that we have some privileged position in the universe, are challenged by this point of pale light.
Our planet is a lonely speck in the great enveloping cosmic dark. In our obscurity -- in all this vastness -- there is no hint that help will come from elsewhere to save us from ourselves. It is up to us. It's been said that astronomy is a humbling, and I might add, a character-building experience. To my mind, there is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly and compassionately with one another and to preserve and cherish that pale blue dot, the only home we've ever known.
[Carl Sagan, in a commencement address given May 11, 1996]
For an alternate means of trying to grasp the sense of scale in the galaxy (let alone the universe), visit the Build a Solar System page from the Exploratorium in San Francisco. It lets you enter a scaled size for the sun and calculates the sizes and distances of the planets and some "nearby" stars on that scale. (Requires JavaScript.)
Also, here is a series of charts showing the relative sizes of the smaller planetsin our solar system, then the larger planets, then the Sun, and then progressively larger stars.