Jose Drost-Lopez

More brain connections than stars in the universe? No, not even close.

In Reality Check on September 10, 2010 at 11:35 pm

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.

Cosmic Microwave Background map of the universe

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.

The core of the Milky Way. Our solar system is a microscopic spec of dust in there.

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.

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  1. Reblogged this on peakmemory and commented:
    I was reading Sondra Kornblattt’s “A Better Brain at Any Age” and came across this quotation: “There are more connections in your brain than there are stars in the universe.” This seemed obviously false to me. With a little Internet searching, I found this very good refutation.

  2. […] the brain might not have more connections than stars in the universe (sorry guys), it is still complex. In fact, someone I respect defined a neuroscientist as “someone who […]

  3. There are more connections in all the human brains combined than there are stars in the universe is what the origin should have been. All humans combined it is 700 sextillion versus the approximated 70 sextillion stars

  4. You are ignoring the fact that “synapses” are NOT the only connections between cells. There are virtual, invisible, and instantaneous “connections” between vastly separated points in the brain. And this does not include connections provided by the corpus callosum.
    This has been known for a very long time.
    See: “Brain Yields New Clues On Its Organization For Language”
    By SANDRA BLAKESLEE
    Published: September 10, 1991
    NY TIMES
    http://www.nytimes.com/1991/09/10/science/brain-yields-new-clues-on-its-organization-for-language.html

  5. The quote goes “there are more connects in the human brain than stars in the galaxy”
    The galaxy is much smaller than the universe. That’s the way I heard it at least.

  6. […] More brain connections than stars in the galaxy? Not even close – Decode The Mind […]

  7. […] And the synapses in a single brain number more than the number of galaxies in the observable universe, and more the stars contained in the Milky Way galaxy!!!  Tell me that happened on accident.  Go […]

  8. Wrong. You can’t just count synapses. This concept refers to number of ways to connect. For example, the most beautiful rich colored, high resolution photograph on your computer screen is made of 3 code generated colors only. Yet, millions, even billions of colors are generated from 3 colors. Now, instead of 3 basic units, go back, do the calculation for 100 million basic units

  9. Wrong. You can’t just count synapses. This concept refers to number of ways to connect. For example, the most beautiful rich colored, high resolution photograph on your computer screen is made of 3 code generated colors only. Yet, millions, even billions of colors are generated from 3 colors.
    Now, instead of 3 basic units, you have to count the synapses on each nerve ending, and count the number of potential connections. which is going to be about in the hundreds or thousands per neuron. Then there are interconnections between multiple neurons and the huge number of possible combinations.

  10. Observable by human optical is relative to active synapses in brain at that time. When the brain begins to recognize its reflection more connections appear right before the human eye or experience. Optical illusion? No. Even in well lit suburb? Yes.

  11. The distinction, I believe, is between “actual” connections and “potential” connections. As far as I understand, the above article is correct with respect to actual connections and mathematically incorrect with regard to potential connections.

  12. My understanding is that the above article is correct with respect to “actual” connections and mathematically incorrect with respect to “potential” connections.

  13. As mentioned, some of the incorrect statements erroneously conflated one estimate of the number of possible inter-connections (as in a plastic brain that can form new, different connections at any point) with the number of connections at any instant in time. The latter would be the 100 trillion figure. But the former is possibly greater than the number of (sub-atomic?) particles in the universe. Of course, possible interconnections and useful interconnections could be two different things with vastly different numbers.

  14. […] each of which connects to counterparts on thousands of other neurons. There are thus more than 100 trillion synaptic […]

  15. […] each of which connects to counterparts on thousands of other neurons. There are thus more than 100 trillion synaptic […]

  16. […] each of which connects to counterparts on thousands of other neurons. There are thus more than 100 trillion synaptic […]

  17. Thanks for the info, however i heard a doctor talking aboyt synapses in “oligodendrocyte”.
    Is this detail makes a difference?

    BTW, u dont even know what an “oligodendrocyte” is! 😐

    • Thanks for the info, however i heard a doctor talking about synapses in “oligodendrocyte”.
      Does this detail make a difference?

      BTW, I dont even know what an “oligodendrocyte” is! 😐

  18. Oh! Thanks for that. I was skeptical having heard that on a series of science documentaries on tv. I’m now wondering how many connections computers have now and may have in the future

  19. You’ve completely misunderstood the quote and your calculations are far too simple resulting in a result that isn’t even close to the correct answer.

    Its not more actual brain connections than stars in the universe, its that there are more possible combinations than stars (or even subatomic particles) in the universe. In other words there are more potential ways of wiring the brain than there are subatomic particles in existence. The point is to demonstrate that there are an unimaginable vast number of ways of varying a personality/mind/person… Ironically its the number of STARS that are NOT EVEN CLOSE to the possible combinations of neurons in the brain. We’re talking many many orders of magnitude behind for number of stars because the combinations of neurons possible are so large the number becomes difficult to even calculate but its probably billions of orders of magnitude behind.

    We’re talking about 10^5,000,000,000 neuron connections, so 10^22 stars is laughable small in comparison, and thats just neurons, we’re not even including synapses in that and there are even more synapses than neurons. 10^5,000,000,000 – 10^22 = 10^4,999,999,978. Basically the number of stars when shown on the scale of the number of possible neuron connections, is in effect 0, its that insignificant in comparison.

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