time, big numbers (and small ones too)
Dec. 28th, 2006 03:52 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
kengr(from a mailing list I'm on)
And at the opposite end of the time scale...
Modern personal computers run at gigahertz rates. That means that a one gigahertz system has a "clock cyle" that is one nanosecond long. A two gigahertz system has one that is half a nanosecond long.
But to get a better feel for a nanosecond, consider this.
In one nanosecond, light travels about 11 inches. Electricity in wires travels much slower. So in one nanosecond, the signals in your computer may travel less than 6 inches.
Which is why the "onboard cache" on the CPU is so important. There isn't *time* to fetch data from the memory chips a few inches away on the motherboard!
Scientists will speak of picoseconds in discussing some phenomena. How long is a pico second? It's 1/1000 of a nano second. Or about the time it takes light to travel the width of a grain of salt.
Greetings all
As a research scientist I sometimes find myself explaining things to folks that are way outside their realm of expertise. This is especially so if you are talking about long periods of time (in this case it was evolution and how things change slowly over the eons), most folks just can't grasp terms like "million" and "billion." To try and help someone this morning grasp these numbers I came up with the following scale and I though I'd pass it on.
A billion seconds ago it was (more or less) April, 1975.
A billion minutes ago it was August of 105 AD.
A billion hours ago it was 112,070 BC and humans-to-be were just getting the hang of how to chip stones into tools.
A billion days ago was 2,740,000 years in the past (again, more or less). Megafaunal mammals were wandering around looking at the flat spot that would one day host Mt Hood and some short, hairy creatures were balancing precariously on their hind legs and leaving their bones in Oldivai Gorge.
A billion years ago nothing at all lived on the land and in the oceans multicellular creatures were still somewhat of a rarity.
And now back to my time sheet which is due tomorrow.
Arnor
And at the opposite end of the time scale...
Modern personal computers run at gigahertz rates. That means that a one gigahertz system has a "clock cyle" that is one nanosecond long. A two gigahertz system has one that is half a nanosecond long.
But to get a better feel for a nanosecond, consider this.
In one nanosecond, light travels about 11 inches. Electricity in wires travels much slower. So in one nanosecond, the signals in your computer may travel less than 6 inches.
Which is why the "onboard cache" on the CPU is so important. There isn't *time* to fetch data from the memory chips a few inches away on the motherboard!
Scientists will speak of picoseconds in discussing some phenomena. How long is a pico second? It's 1/1000 of a nano second. Or about the time it takes light to travel the width of a grain of salt.
