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Scientists are finally sure: Voyager 1 entered the heliosheath on December 16, 2004. The heliosheath is the region that separates our solar system from interstellar space. You’ve heard of the solar wind? It forms a bubble, called the heliosphere, that surrounds the solar system as it orbits the core of the Milky Way galaxy. When Voyager 1 entered the heliosheath, it crossed the termination shock, a boundary/shockwave where the supersonic solar wind slows to subsonic speeds. There’s only one more boundary to cross. It’s not known when Voyager will cross the heliopause, or if it will still be functioning when it does, but when the solar wind that forms the heliosphere is finally stopped by the impossibly sparse gas and dust that’s swirling out there in the impossibly vast space between stars, that’s the heliopause–the true edge of our solar system.

I am not what most people think of as a traditionally religious person, but when I contemplate this, it gives me a feeling I cannot describe or put into words. This time, it’s not the dread that used to bother me while considering my insignificance in the universe. It’s more like wonder, but that word is inadequate.

Part of it is that a group of humans, inconsequential little beings on an unremarkable rock way off to the side of one among innumerable galaxies, have created something that has autonomously made its way so very far from where it started. It’s a staggeringly monumental achievement when you look at it (okay, when I look at it) in terms of our apparent irrelevance in the universe. And the other thing is that it is altogether possible that we will never again send an object into space with as great (if hopelessly faint) a possibility of connecting with extraterrestrials. So I’m also moved about the fact that both Voyagers 1 and 2 carry messages from earth designed to tell the universe a thing or two about the inhabitants of the third planet of this one little yellow star out here.

I recently read The Sacred Depths of Nature by Ursula Goodenough. Ms. Goodenough knows exactly the emotions I have failed to describe, because she has experienced them herself, which motivated her to create this fascinating examination of life, the universe and the natural world: she takes us from subatomic particles through the evolution of life, on up to the horrifying scale of the universe. Her approach in the book is to lay out the science at each level, then reflect on the spiritual meaning she finds infused in everything around us. To me, reading her short but powerful book felt nothing short of revelatory.

Further reading:

• Voyager 1 Sends Messages from the Edge
  
• Heliopause; from Wikipedia, the free encyclopedia
  
• The Sacred Depths of Nature
  
• Voyager Project Web Site