Sometimes in science articles, and in arguments about abiogenesis or evolution on the Internet, a writer will refer to a length of time as a cosmic, geologic, or evolutionary “blink of an eye”. The length of time varies, but typically the writer means something on the order of a thousand years, the subtly ironic point being that, although a thousand years seems like a long time to us, or in the time frame of human civilization, it’s a very short in the time frame of the Universe.
But some writers are a bit loose with the term. I have seen legitimate, intelligent science writers refer to millions of years as a cosmic blink of an eye, which seems a tad long to me. The universe is 13.8 billion years old. A million years is not a huge fraction of that, but it’s long enough that “blink of an eye” is not an apt comparison.
One time, while arguing on the Internet with someone who claimed that life appeared on Earth “almost instantly” after Earth’s formation (only two hundred million years, I pointed out), they claimed that two hundred million years is a “blink of an eye” (only about 1/70th the age of the Universe, I pointed out).
It got me to wondering, what actually is a cosmic blink of an eye?
I figure that if you want to scale human time scales up to cosmic, a good simple way to do that is to equate one year of human time to one billion years of cosmic. That would make the Universe a healthy young teenager approaching their 14th birthday, and the Earth a rambunctious four-year-old. In order to find out how much time a cosmic blink of an eye is, we simply multiply the duration of a human blink by a billion.
A blink takes about 0.2 seconds, which makes a cosmic blink 200 million seconds. There are 31,557,600 seconds in a year.1
A cosmic blink of an eye is 6.3 years.
Yeah, that’s a little shorter than 200 million years.
In fairness, the phrase is not supposed to me mathematically foolproof. Nobody is doing calculations when the use, or hear, this phrase. It’s supposed to be an ironic way to point out the vast difference between human and cosmic time scales. I’d say as long as you keep it to the order of a thousand years (a cosmic commercial) or ten thousand years (a cosmic smoke break), the phrase “cosmic blink of an eye” is acceptable. When you start using it to refer to a hundred thousand years or more, “blink of an eye” is no longer a reasonable comparison.
- A Julian year, 365.25 days. When scientists recon prehistoric times, they use the Julian year, which differs slightly from our familiar tropical year, which is a Gregorian year (97 leap days every 400 years) plus occasional inconsistent leap seconds. ↩︎
