Wednesday, May 19, 2010

Times and Seasons Unit 2 - Telling time

A day is 24 hours long. It takes our side of the earth 24 hours to make one full rotation and then rotate to face the sun again.  Each time our earth faces the sun we have day time.  It takes 24 hours for each day to complete.

When we learned about the creation it took seven days of creation to make the earth.  In the scripture story it says that "Jesus made the earth in six days. The days were much longer than our days."  In Abraham 3: 4 we read.  "one revolution was a day unto the Lord, after his manner of reckoning, it being one thousand years according to the time appointed unto that whereon thou standest."  This means that one of the Lords days is 1000 years long compared to our days.  When you think of how long the creation days could have been, you can see that the Lord had allot of time to make such glorious things.  Click on the picture below to print out the How Long is a Day worksheet.  Color this picture in.  We will use this worksheet later in our lesson.

    A sundial is  like a clock.  Since there are 24 hours in a day, a sundial could end up having as many as 24 rocks.  A long time ago people would use sundials like clocks.  They would place the first rock when the first lights of the sun hit the dial.  They would place the last rock when the last lights of the day hit the sundial.  The would place the middle rock at high noon.  Then they would divide the space between the first and last rock into 12 equal spaces.  Thus the daytime was divided into 12 parts.  They would do this again at night, and divide the night into 12 parts.  Because the length of the days and of the nights changes as the year passes the time it took for the sun to move from one marker would vary depending on what time of day it was.  When the days were longer and the nights were shorter the distance between the rocks in the daytime were greater, and smaller in the night.

    Now a days we have mechanical clocks, this means we can divide the day into 24 exactly equal parts.  We still have our clock divided into two sets of 12, but the length of the day and length of the night do not change how long the divides are.  An hour is always 60 Min's long which is always 60 seconds long.

    Here you see a 24 hour wall clock, this is what it would look like if our clocks counted up to 24 instead of counting to 12 twice.

    Most clocks you see will be the standard 12 hour clock you see here.  Looking at the face of the clock you will see that it has three hands on it.  The shortest hand tells us what hour it is.  The next hand on the clock gets a little bit longer so we can more closely see where it is pointing, this medium size hand tells us what minute it is in the hour.  The final hand, usually the thinnest, fastest, longest hand is the tells us what second of the minute it is.  As each hand gets longer it is pointing to a smaller amount of time.  It is longer so we can see closer and more accurately where it is pointing.

    The shadow your stick casts is like the short hand on the clock.  It tells you what hour it is.  The minute hand can not be made by the sun.  The minute hand tells you how much of the hour has passed.  It goes around the clock in one hour, when it is half way around the hour is half way over.  When it has made it all the way around and back up to the top one hour is done and a new hour is beginning.

    A sundial is used to watch the shadow pattern that the sun casts.  
    • To start out with we need a stick.  Find a small stick.  This stick needs to be standing up so we can watch its shadow.  
    • You can get the stick to stand up by pressing a ball of playdough around its base and then pressing it against the ground.  Or you could put some dirt or sand in a paper cup and use the cup to help it stand.  
    • Once your stick is standing you will see its shadow.  Since the shadow of the stick is always falls opposite the sun, the shadow will move slowly as the sun slowly moves through the sky.  
    • Now set an alarm for the next hour mark comming up on your clock.  When the alarm goes off run outside and see where the shadow is.  Place a rock at the end of the sticks shadow.  
    • Set the alarm again, for another hour away.  Repeat this activity until you have all the hours you want marked on your sundial.  
    Need a photo  

    Lets play the sundial game, where you will pretend you are parts of the sundial.  You will need.
    • A large open are clear from objects
    • 1 person who represents the sun
    • 1 person who represents the sticks shadow
    • 1 person or chair that represents the stick

    To Play.  The "shadow" always hides behind the stick away from the sun.  Or the "shadow" always keeps the stick between him and the sun.
    • The "sun" walks slowly in a circle or half circle around the "stick"
    • The "stick" stands still.
    • The shadow watches the sun move and also moves so that the stick is always between the sun and him.  The shadow can either stand behind the stick.  Or the shadow can lay down on the ground and roll, slither, or move around the base of the stick as the sun moves around the stick.  Always trying to stay in line with the stick and the sun.
    In this game you can act out quickly what will happen with your sundial over the long time of the day.  You can see how the shadow will move.

    O'Clock.  As mentioned before the minute hand goes around the clock to tell you how much of the hour has passed.  When the minute hand is pointing stright up at the 12 this means one hour has just ended and a new is just beginning.  We call this time "o'clock".  When telling the time, the first part of the time is determined by the hour hand.  Look at the hour hand and see what time it is pointing to on the clock.  That tells you what hour it is.  If both hands are pointing to the 12 then we say it is twelve o'clock.  We write 12 o'clock with numbers like this 12:00.  This means it is the 12th hour and 00 minutes of the hour have passed by.

    If the short hand is pointing at 10 and the long hand is still pointing at the 12 we say it is eleven o'clock.  We write 10 o'clock like this 11:00  This means that it is the 10th hour and 00 minutes of the hour have passed by.

    Again if the short hand is pointing at the 9 and the long hand is pointing at the 12, then we say it is 9 o'clock.

    What time is it on the clock below?

    What time is it on this clock?

    Lets play a domino time game.  In this game you will match the face of the clock to the written digital time .
    • Print out each of these pages. Domino set 1, Domino set 2, Domino set 3, Domino set 4.
    • Cut around the outside of the dark black lines, but not the thin black lines.  
    • Now you can play dominoes.  Connect the matching digital time to the matching clock face to make a chain of dominoes.
    Worksheet: Now that you know how to tell the hour answer the questions on the second page of your How Long is a Day worksheet.
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