Questions that need answers!

[jfoldbar]

question.

i just read on wikepedia that the horizon we can see is about 5 kilometers. as a kid i was always taught in school its way more than that

in korea, there is an island in the sea more than 40 kilometers away with no mountains on it. it can be seen from the beach. how is that possible when it is way more than 5 ks.

[Peter Aawen]

^^ Who said Wikipedia was the be-all & end-all fount of knowledge??

You can post up pretty much any crap you like there, & unless someone modifies or updates it, there it stays, for all the 'believers' to spout & refer to as truth, for all time.....!!

[cmar]

SquareRoot(height above surface / 6.752) = distance to horizon

Where height above surface is in centimetres and distance to horizon is in Kilometres.

So in fact wikipedia is actually right in this case.

Tsushima Island, it actually is 50 Km from both South Korea and Japan ( mid way between), and can seen from Korea, but it is not flat, it has mountains.

[jfoldbar]

tsushima's highest elevation is 650 meters, so of course it can be seen.
one island though, geomundo, can be seen from jeju. which is more than 40 ks away. geomundo (horseshoe shaped ne from jeju) has an elevation of 137 meters at the north, and flat elsewhere, meaning according to the calculations you should only be able to see the very top of the peak at that distance. but i can assure you the whole island can bee see from the beach at jeju. which doesnt add up according to the calculations.

[blutoy]

a while ago, we went to Hawaii, done a tour of the USS Missouri, the tour guide told us that the BIG guns back in the day, could be accurate to 23 miles, because that is where you loose track is your vision, because of the curvature of the earth, a bit different now with GPS Guided missiles
so 50km sounds about right
cheer's

[MudChaser]

Why were pocket watches replaced by wrist watches which were replaced by digital watches which were replaced by phone watches we carry in our pockets which were replaced by phones we wear on our wrist?

[BigDutchy]

Hahahahaa that's hilarious

[nilla60]

Pocket watches were the iPod of the day. You were *the* man if you could tell the time without having to run in to town and look at the giant clock in the square. A town clock small enough to have in your *pocket*, how cool would that have been when clocks were the size of a room or large cupboard?

[Peter Aawen]

Why were pocket watches replaced.... ???

One word - Convenience!

Having the time (or your phone) where you can see it at a glance most of the time is far more convenient than having to dig it out of a pocket & check it; the same reason that more & more devices are becoming more convenient to use across the board, but especially those things that we used to hafta carry in a pocket & take out to use, then fitted with ear buds & remote mic's before upgrading to Bluetooth so we could use them more conveniently!!

[Shann Low]

Who needs a watch to tell the time?
It's either Winter time, Spring time, Summer time, or Autumn time!.
Watches measure gravity, NOT time!
Calendars measure TIME!

Clocks and watches measure the rate of the earths spin about its own axis (sunup to sunup), and THAT my friends is the force we know as GRAVITY!

Calendars measure TIME (Which is the earths 365.25 days annual orbit about the Sun)!

Some people have zero knowledge of Time, Measuring your ETA at a destination in minutes is somewhat akin to measuring your distance to a point in grams!

[BigDutchy]

So, a statement like this; the next train might arrive at 15 minutes past 145 grams, is a little silly....

[V Williamson]

^^^ Shann...

"the rate of the earths spin about its own axis (sunup to sunup), and THAT my friends is the force we know as GRAVITY!" ...

ummm... what fizziks text did you get that from??

According to Halliday and Resnick, "Physics", Wiley 1966, p387
"
The force between any two particles having masses m1 and m2 separated by a distance r is an attraction acting along the line joining the particles and has the magnitude

F = G * (m1*m2) / r^^2 ,

where G is a universal constant having the same value for all pairs of particles. This is Newton's law of universal gravitation. "

The rate of rotation on an axis by one or other or both particles does not enter the equation. Hmmmpphhh.

[V Williamson]

So, a statement like this; the next train might arrive at 15 minutes past 145 grams, is a little silly....

wot about "a hair past a freckle" ??

[jfoldbar]

v williamson, i think shann low just likes to show everyone how smart he isnt.

heres one, why do we clever humans go to greats lengths to water and fertilize grass/lawn, just so we then have to go to great lengths to cut it and get rid of it?

if a pair of jeans is $50, and in the keeping of the trendy fashion,the jeans that already have the knees worn out of them are $80, then how much would a pair of jeans be that has been used as an oil rag for 6 months or been dragged behind a log truck? would they be priceless? i must be sitting on a goldmine then.

[V Williamson]

^^^ mumble, mumble.... that might be a bit harsh about our old mate...

Everyone is entitled to a crash and burn every so often. I think the important thing is that we all learn something, even if by mistakes. And even after learning, I find I am still quite capable of a crash and burn. Like the old story, I often feel that the only time I take my foot out of my mouth is so as to put the other one in.... Ok, maybe not that bad.... I don't want to see the thread turn into a useless grovelling session.

One rather curious feature of the spin of the Earth on its axis is that the rate of spin is slowing down. I refer to Malin and Frew, "Hartung's Astronomical Objects for Southern Telescopes", Melbourne University Press 1995 page 9

"When very accurate quartz crystal clocks were introduced into observatories just before and during World War II, they were able to confirm what had long been suspected: that the Earth's rotation was not constant. By 1973, with the aid of even better atomic clocks, it was found that the rotation was slowing down by about a second a year,...."

Ok, so my question:- How old is the Earth? Because if a year consists of about 365 (days) X 24 (hours per day) X 60 (minutes per hour) X 60 (seconds per minute) = 31 536 000 seconds per year, when do we run out of seconds if we are currently losing 1 second a year as per the reference above? That is, counting backwards in time, wots the go??

Can't help with the fashion trend (and seriously, does a set of jeans torn at the knee look good anyway??).