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Author Topic: Question of the Week - Old Version  (Read 179087 times)

Offline neilep

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Re: Question of the Week - Old Version
« Reply #125 on: 09/02/2004 15:57:25 »
As a kid, I used to think the wind was caused by the Earth spinning faster that day !!!!....

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Offline Quantumcat

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Re: Question of the Week - Old Version
« Reply #126 on: 11/02/2004 15:21:43 »
Lol!! That's so cute! I remember thinking it was caused by convection before I learnt about pressure and stuff.

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Offline NakedScientist

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Re: Question of the Week - Old Version
« Reply #127 on: 21/02/2004 07:33:38 »
Answer to HOW FAST IS THE EARTH SPINNING ? IS THE RATE CHANGING ?

The earth completes 1 revolution per day (24 hours). The distance that it effectively travels (at the equator) in completing 1 revolution is equal to the planet's circumference or girth.

You can calculate the circumference of a circle using the formula 2x pi x radius of the circle.

The radius of the earth is 3963 miles (6378 kilometres). The circumference is therefore 2 x 3963 x 3.141 (approx. value of pi) = 24900 miles (40,000 km)

The speed of the earth is therefore 24900 / 24 = about 1000 miles per hour (1600 km per hour).

The rate of rotation is indeed slowing down. About 65 million years ago, at the time of the dinosaurs, the earth span much more quickly meaning that a day was correspondingly shorter, lasting only about 16 hours.

It is worth bearing in mind, however, that the calculation above applies at the equator - the actual speed you would be travelling at varies according to where you stand on the planet surface - at the north pole, for instance, your speed would be zero. In the UK and north US your speed is closer to 700 - 900 miles per hour (1125-1450 kilometres per hour).

sorry this took a little while to come out - I've been a bit busy !

TNS
 

Offline NakedScientist

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Re: Question of the Week - Old Version
« Reply #128 on: 21/02/2004 09:01:49 »
Here's this week's QOTW :

"WHAT IS A SUNSPOT ? WHAT CAUSES THEM AND WHAT EFFECTS CAN THEY HAVE UPON EARTH ?"

TNS
 

Offline cuso4

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Re: Question of the Week - Old Version
« Reply #129 on: 24/02/2004 08:39:11 »
Astronomy is never my strong point. I'll have to do some research for this.

Angel

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Offline CsManiacDan

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Re: Question of the Week - Old Version
« Reply #130 on: 29/02/2004 20:32:37 »
I'm pretty sure a sun spot is an area on the sun that's cooler than the rest of it, that's why it's darker, though why it's cooler i have know idea nor do I know whats causing it

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Offline neilep

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Re: Question of the Week - Old Version
« Reply #131 on: 29/02/2004 21:17:28 »
Yep...Im with you on that one Dan, I'm sure magnetism comes into the equation too somewhere along the line, as well as the eleven year cycle, where they pop up the most and last about a week or so. Not too sure what effects they have upon the earth apart from manifestations arising from magnetic disruptions ? perhaps electrical disruption and interference with satellite communications, and birds/sealife/animals that depend on the earths magnetic field for navigation.

Or is it just something that adolescent stars get as they go through puberty ? :-)


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Offline Donnah

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Re: Question of the Week - Old Version
« Reply #132 on: 02/03/2004 04:07:20 »
I vaguely remember hearing something about sun spots and radioactivity.
 

Offline NakedScientist

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Re: Question of the Week - Old Version
« Reply #133 on: 02/03/2004 05:48:55 »
ANSWER TO LAST WEEK'S QOTW "WHAT ARE SUNSPOTS AND HOW DO THEY AFFECT THE EARTH ?"

Sunspots are dark spots, up to 50,000 miles in diameter, that move across the surface of the sun, expanding and contracting as they go. They usually last for several days, although very large ones can persist for several weeks.

A typical sunspot comprises a dark region called the umbra, surrounded by a lighter region known as the penumbra. They appear relatively dark because the surrounding surface of the Sun (called the photosphere) is about 5500 degrees C., while the umbra is a chillier 3480 degrees C.

Sunspots are surrounded by an intense magnetic field over 2,500 times stronger than Earth's, which is much higher than anywhere else on the Sun. This powerful magnetic field slows down the flow of hot gases from the Sun's interior to the surface, which is why sunspots are relatively cooler than the rest of the sun's surface. They usually occur in pairs which have their magnetic fields pointing in opposite directions

People have been watching sun spots since Galileo Galilei first described them in the early 1600s, and we probably knew about them even before that. There are reports of ancient peoples noticing the sun's blemished appearence, particularly on cloudy days and during dust storms.

But thanks to Galileo's work we now know that the sun follows an 11 year cycle - the Solar Cycle - during which the number of sunspots steadily increases to a maximum, then decreases again at the end of the cycle. Towards the maximum the sunspots occur closer to the equator of the Sun. Plotting the area covered by sunspots at a given latitude versus time produces an interesting butterfly shaped distribution of unknown significance.

Some studies have suggested that the average ocean temperature increases and decreases, world-wide, by 0.5 degrees C in phase with the sun spot cycle, but the mechanism is not understood.

So how do sunspots affect the earth ?

This is not known for certain. During periods of maximum sunspot activity scientists have recorded a very slight increase in the energy output from the sun, and ultraviolet (UV) radiation increases dramatically which can affect our atmosphere. Also, a period known as known as the Maunder Minimum, during which there were very few sunspots, coincided with a number of long winters and severe cold temperatures (called the Little Ice Age) in Western Europe.

Furthermore, sunspots are also associated with phenomena called CME - Coronal Mass Ejections or solar flares. These stellar convulsions produce as much energy as a billion megatons of TNT and occur near to sunspots on the dividing line between the pair of oppositely directed magnetic fields. Solar plasma interacting with the strong magnetic field is ejected away from the sun's surface and out into space forming the flare which bathe the earth in cosmic radiation leading to an increase in geomagnetic storms which can affect satellites, power grids and radio transmissions. They also produce a more pleasant side effect - the beautiful northern and southern lights - where the charged particles interact with the earth's magnetic field...

Some sunspots :

 

Offline NakedScientist

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Re: Question of the Week - Old Version
« Reply #134 on: 03/03/2004 02:13:05 »
Here is this week's question of the week :

"CAN YOU EXPLAIN 'WIND CHILL FACTOR'" ?

TNS
 

Offline Quantumcat

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Re: Question of the Week - Old Version
« Reply #135 on: 03/03/2004 09:17:59 »
I think so. Wind chill factor is when lots of bits of moisture in the air go past your skin fast, taking heat as they go. Or maybe it's not moisture it's air. Oh well, doesn't matter. That's why you're cold when you get out of the bath too, because the water becomes a thin layer and the abundant heat in your skin goes into the water and it evaporates. All the heat moving out of you makes you feel cold. Also why fans that push air around make you lose heat and feel cooler.

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Re: Question of the Week - Old Version
« Reply #136 on: 11/03/2004 19:40:29 »
I think I have to agree with Quantumcat, but I'm not sure if it's moisture in the air, or air molecules themselves, that cause the decrease in temperature, because (I think) it's possible to have a windchill when there's very little moisture in the air.

Just my 2 cents.
 

Offline tweener

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Re: Question of the Week - Old Version
« Reply #137 on: 11/03/2004 20:35:42 »
Moisture in the air (aka relative humidity) affects the wind chill factor by making the air capable of holding more heat for a given volume.  At the boundary between skin and air, there is a layer of still air that warms up and serves to insulate the skin from losing more heat.  When wind moves the air, this layer is thinned and cooled, thus increasing the rate  of heat loss.  The faster the wind blows the faster the heat is lost, thus the wind chill temp. is lower.  The higher the relative humidity, the more efficiently the air removes heat from the skin, and the lower the wind chill temp.

Sounds good anyway.

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Offline NakedScientist

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Re: Question of the Week - Old Version
« Reply #138 on: 14/03/2004 02:00:21 »
ANSWER TO LAST WEEK'S QOTW "CAN YOU EXPLAIN 'WIND CHILL FACTOR'"

You have all pretty much hit the nail on the head. Heat leaves our bodies, which are much warmer than the surroundings, by following a thermal gradient (hot to cold). The cooler the surroundings relative to body temperature, the steeper the gradient and hence the greater the rate of heat loss.

When you stand in still air, heat leaving your body warms the air around you so that it acts like a layer of insulation. This effectively reduces the thermal gradient, slowing down heat loss. But when you are out in a high wind the air around your body is continuously being replaced with fresh cold air. Under these circumstances the thermal gradient becomes much steeper and you lose heat much more rapidly, at a rate equivalent to the surrounding temperature being much colder than it really is. Hence the term "wind chill factor".

TNS
« Last Edit: 14/03/2004 02:12:00 by NakedScientist »
 

Offline NakedScientist

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Re: Question of the Week - Old Version
« Reply #139 on: 14/03/2004 02:01:34 »
This week's QOTW is much more challenging and might require a bit of research on your part, but has a satisfying answer. Have a go at :

"WHY ARE THERE 7 DAYS IN A WEEK, AND WHY DOES THE WEEK BEGIN ON A MONDAY ?"

Happy hunting

TNS
« Last Edit: 14/03/2004 02:10:41 by NakedScientist »
 

Offline nilmot

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Re: Question of the Week - Old Version
« Reply #140 on: 15/03/2004 08:27:56 »
I'm not so sure this is a scientific question. More of a philosophical question.

Tom
 

Offline NakedScientist

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Re: Question of the Week - Old Version
« Reply #141 on: 15/03/2004 23:04:58 »
No, it is definitely a scientific question, with a scientific answer, though some of the answer has its origins in philosophy.

TNS
 

Offline cuso4

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Re: Question of the Week - Old Version
« Reply #142 on: 17/03/2004 13:40:39 »
I found something on the Internet which might be what we're looking for.

Why are there 7 days in a week?

One month is roughly the time taken for the Moon to rotate the Earth once. One year is 365 days and divide this by 12, we get 30.416 days per month. One week is the time taken for the Moon the a quarter of the Earth. So divide 30.416 by 4, we get a value around 7.

I'm not sure anout the second question but I'll have a go.
Monday is named after the Moon and since ancient people use the movement of the Moon to measure time (Chinese Calender is based on this), Monday is set to be the first day of the week.

Angel
 

Offline NakedScientist

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Re: Question of the Week - Old Version
« Reply #143 on: 19/03/2004 05:19:39 »
Well done Angel, you are on the right lines. Keep going.

TNS
 

Offline neilep

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Re: Question of the Week - Old Version
« Reply #144 on: 19/03/2004 13:32:48 »
Here is something I have blatantly 'borrowed' from a website I found which I think part explains why Monday is the first day of the week.

MONDAY
There are some countries which have Monday as the first day of the week. This is in accordance with the International Standard
"ISO 8601:1988 (E)"
Which states under item:
5.4 Combinations of date and time of day representations
3.0 Terms and Definitions
3.17 Week Calendar
"A seven day period within a calendar year,
starting on Monday and identified
by the ordinal number with in a year....."

There are countries in Europe, such as Denmark, Norway and Sweden that have Monday as the first day of the week.
In the USA documents ANSI (X3.30) and NIST (FIPS 4-1) adopted ISO 8601 and list Monday as the first day of the week.
However, the calendar in USA has
Sunday as the first day of the week


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Offline neilep

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Re: Question of the Week - Old Version
« Reply #145 on: 19/03/2004 13:37:32 »
Here is something else i have borrowed, regarding the number of days in the week.
Known as an interval between Market Days. In central Asia five days was used, Egyptians used ten days and the Babylonians like the multiple of seven because of the lunations of the moon. In Rome the eight day cycle was used for market. The orgin of the seven day week seems to be related to the four (about) seven day phases of the moon. Also the seven colors in the rainbow, and in the Babylonian times, the seven planets. By the time of the first century BC the Jewish seven-day week seems to have been put into place throughout Rome.


The calendar in the USA has Sunday as the first day of the week. The word week comes from Latin "vicis" meaning change. The week is a period of seven days and is now used throughout the world as a division of time. History seems to favor the Hebrew or Chaldean origin and the week is mentioned as a unit of time in the Bible, see the Old Testament book of Genesis 29:27.
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Offline tweener

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Re: Question of the Week - Old Version
« Reply #146 on: 19/03/2004 16:13:09 »
If you're going to insist that Monday is the first day of the week despite every calendar in the known universe, then I say Monday is the first day of the week so that everyone can get off to a really rough start every seven days. :)

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Offline neilep

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Re: Question of the Week - Old Version
« Reply #147 on: 19/03/2004 17:06:54 »
Personally..I think Mondays should be cancelled :D

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Offline Donnah

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Re: Question of the Week - Old Version
« Reply #148 on: 19/03/2004 21:16:12 »
I've got it!  It's divine intervention that caused the 7 day week and the week to begin with Monday.  We're told that God made the world in six days and took the 7th day to rest, calling it the sabath.  How do you like that?  He takes the 7th day to rest but expects us to get up on that day to go to church.  *tongue in cheek*
 

Offline nilmot

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Re: Question of the Week - Old Version
« Reply #149 on: 20/03/2004 08:45:27 »
But isn't that a religious explaination not a scientific explaination?

Tom
 

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Re: Question of the Week - Old Version
« Reply #149 on: 20/03/2004 08:45:27 »

 

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