Our observable universe is huge. Make that really huge. So if you have ever read that our brain connections outnumber the stars in the universe (perhaps here or from this book), I hope you frowned in skepticism.
Here are the real numbers:
Neurons (rough overestimate for adults): 10^11, or 100 billion
Synapses (based on 1000 per neuron estimate): 10^14, or 100 trillion
Stars (estimate for observable universe): 7 x 10^22; that’s 70 sextillion!
For every brain synapse (“connection”) we have, there are (at least) 700 million (700,000,000) stars somewhere out there. In other words, the number of stars per human synapse is about the number of people in Europe. Only if we count up the synapses of all the people alive (10^21) do we get a number comparable to the star count.
How could confusion arise on such a whopping difference? The mistake is clear in my first link above (“Cool Brain Facts”). The site assumes that most stars are in our galaxy, the Milky Way. That’s monumentally incorrect–our galaxy is unexceptional (star-wise or otherwise) among the approximately 100 billion galaxies within detectable range. On the bright side, this fact suggests an easy correction for our myth:
The number of synapses in the human brain is larger than the number of galaxies in the observable universe. Also, there are more synapses in an average human brain than there are stars in our Milky Way galaxy.
Let me clarify that the brain is a magnificent organ no matter how you spin the numbers. As early as two millenniums ago Hippocrates realized its importance: “from the brain, and from the brain only, arise our pleasures, joy, laughter and jests, as well as our sorrows, pains, griefs, and tears.” But no matter the intricacy of our brains, let’s not belittle the majestic scale of the cosmos.