# Unit of time **URL:** \ **Category:** Factual Questions\ **Created:** [September 4, 2003, 5:13pm UTC](https://boards.straightdope.com/t/unit-of-time/199555 "2003-09-04T17:13:27Z")\ **Posts on this page:** 8\ **Page:** 2
**Author:** ![Achernar](https://avatars.discourse-cdn.com/v4/letter/a/e274bd/32.png) [@Achernar](https://boards.straightdope.com/u/Achernar)\ **Post date:** [September 4, 2003, 11:18pm UTC](https://boards.straightdope.com/t/unit-of-time/199555/21 "2003-09-04T23:18:49Z")
The age of the universe is a tough thing to define and measure. Often in astronomy we’ll use a unit of time called the _Hubble Time_, which is the inverse of the Hubble parameter. For H[sub]0[/sub] = 70 km/s/Mpc, the Hubble Time H[sub]0[/sub][sup]-1[/sup] is about 14 billion years. The Hubble Time is by design close to the age of the Universe, but it could actually be greater or smaller. ---
**Author:** ![bonzer](https://avatars.discourse-cdn.com/v4/letter/b/45deac/32.png) [@bonzer](https://boards.straightdope.com/u/bonzer)\ **Post date:** [September 4, 2003, 11:22pm UTC](https://boards.straightdope.com/t/unit-of-time/199555/22 "2003-09-04T23:22:00Z")
> [@](#): > > \*Originally posted by chappachula \* > there is a measure used by astronomers called a “jiffy” > > its the smallest fraction of a second ever considered to be relevant in science–a decimal point followed by 43 zeros and a 1. No, that’s the Planck time. By contrast, there appear to be [a number of different definitions of a “jiffy”](http://whatis.techtarget.com/definition/0,,sid9_gci822188,00.html), all far, far longer than this. Tolman’s definition - the time it takes for light to cross a nucleon - is the one I’ve come across before, though I’ve never heard a particle or nuclear physicist actually use the term in practise. That said, knowing that the time required is about 10[sup]-24[/sup] seconds is useful if you’re studying them (nucleons that is, not physicists) and the number is relevant in the unfolding of the early stages of the Big Bang. ---
**Author:** ![alterego](https://avatars.discourse-cdn.com/v4/letter/a/6bbea6/32.png) [@alterego](https://boards.straightdope.com/u/alterego)\ **Post date:** [September 5, 2003, 11:28am UTC](https://boards.straightdope.com/t/unit-of-time/199555/23 "2003-09-05T11:28:18Z")
> [@](#): > > \*Originally posted by Q.E.D. \* > \*\*Eh? Think you mistyped. 1.0 x 10[sup]-14[/sup] nanoseconds is a really tiny length of time–1.0 x 10[sup]-24[/sup] seconds, or almost double the Planck time. On the other hand if you meant 1.0 x 10[sup]14[/sup] ns, that’s only 100,000 seconds or about 27.7 hours. \*\* whoops 😉 ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [September 5, 2003, 1:40pm UTC](https://boards.straightdope.com/t/unit-of-time/199555/24 "2003-09-05T13:40:46Z")
If an aeon is a billion years, I make that to be 3.15 x 10[sup]13[/sup] seconds, or 3.15 x 10[sup]22[/sup] nanoseconds. But I might have misplaced a decimal point somewhere along the line… ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [September 5, 2003, 1:57pm UTC](https://boards.straightdope.com/t/unit-of-time/199555/25 "2003-09-05T13:57:44Z")
I make it 3.16 x 10[sup]16[/sup] seconds. ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [September 5, 2003, 1:57pm UTC](https://boards.straightdope.com/t/unit-of-time/199555/26 "2003-09-05T13:57:56Z")
The age of the universe might be the longest time that makes sense to talk about, but it is not a _unit_ of time, per the OP. **alterego** , infinity is not a unit. It does not quantify time. As the definition says, it represents the concept of a boundless quantity. You couldn’t say, “Honey, I’m running out to the edge of the universe, I’ll be back in 2 infinities, maybe 3 if traffic is bad.” **chappachula** , I have never heard of this definition of a jiffy. Computer scientists use a jiffy to mean 0.01 sec., probably because it slips off the tongue more easily than centisecond. ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [September 5, 2003, 2:04pm UTC](https://boards.straightdope.com/t/unit-of-time/199555/27 "2003-09-05T14:04:19Z")
Hmm **Q.E.S** , let’s see: 60 seconds in one minute x 60 minutes in one hour = 3600 x 24 hours in one day = 86,4000 x 365 days in one year = 31,536,000 or 3.15 x 10[sup]7[/sup] seconds in one year. Ah yes, I multiplied by a million, not a billion. As you were. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [September 5, 2003, 2:06pm UTC](https://boards.straightdope.com/t/unit-of-time/199555/28 "2003-09-05T14:06:54Z")
> [@](#): > > \*Originally posted by UncleBeer \* > \*\*Longest = an afternoon at my mother’s house. > Shortest = the period leading up to that. \*\* Longest = The time it takes the person in front of you at a toll booth to search there seats for a dime. Shortest = The time between the light turning green and the cab driver behind you honking to get you moving. [Previous page](https://boards.straightdope.com/t/unit-of-time/199555.md?page=1)