{"id":5206,"date":"2014-06-13T19:23:42","date_gmt":"2014-06-13T16:23:42","guid":{"rendered":"https:\/\/uni-mag.gr\/captain-gg-solar-clock\/"},"modified":"2025-04-01T01:16:42","modified_gmt":"2025-03-31T22:16:42","slug":"captain-gg-solar-clock","status":"publish","type":"post","link":"https:\/\/www.uni-mag.gr\/en\/captain-gg-solar-clock\/","title":{"rendered":"CAPTAIN GG: Sundial"},"content":{"rendered":"
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CAPTAIN GG: Sundial<\/h3>\n\n

Mr A: <\/b>What’s for dinner today? Shall I call my friend Daphne and we’ll have dinner? <\/span><\/p>\n\n

Mom: <\/b>Broccoli. <\/span> <\/p>\n\n

Mr A: <\/b>Mum, I told you I want my friend to come and make a sundial with me in our garden. I want us to eat something tasty, beautiful to look at and play afterwards. You, without being able to understand me, say we have broccoli to eat! You say it with such satisfaction and triumph. I can’t understand you. <\/span><\/p>\n\n

Mom: Of course I feel tremendous satisfaction! I managed to find purple broccoli and I’m looking forward to cooking it, and eating it of course. Isn’t it beautiful? <\/span><\/b>I think your friend, Daphne, will be impressed with these purple flowers you’re going to offer her. It’s not your ordinary green broccoli. <\/span><\/p>\n\n

Small A: <\/b>Adrian, come quickly. Your friend Daphne’s here. Run. <\/span><\/p>\n\n

Daphne: <\/b>Good morning Mr. A. Good morning to all.<\/span><\/p>\n\n

Dad:<\/strong> Good morning Daphne. I heard you came here today to make a sundial with Mr. A. <\/span><\/b><\/p>\n\n

Mom:<\/strong> What a terrible idea. It sounds difficult though.<\/span><\/b><\/p>\n\n

Mr. A:<\/strong> We will also have the help of Captain GG, who is a captain and an expert in astronautics.<\/span><\/b><\/p>\n\n

We have all noticed that during the day the position of the Sun changes in the sky: it starts in the morning at dawn in the East, crosses the whole sky and sets in the evening in the West, which is opposite to the East. The position and length of the shadow of a tree or a PPC pole changes during the day. <\/span><\/p>\n\n

We want to observe and record the properties of this shadow during the day.<\/span><\/p>\n\n

Daphne: <\/b>We also need to measure some properties of the place where we put the clock.<\/span><\/p>\n\n

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The sundial in the National Garden in Athens.<\/span><\/figcaption><\/figure>\n
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The metal triangle is called a gnomon. The shadow of the gnomon falls on the white base and shows every moment the time of day<\/figcaption><\/figure><\/div>\n

Small A: <\/b>I’ve seen a sundial in the National Garden.<\/span><\/p>\n\n

Mr A: <\/b>We want to make a similar clock ourselves.<\/span><\/p>\n\n

To make the clock, we need to measure the angle of the clock <\/span>\n \u03c6<\/span>\n<\/i>. We will see that it is equal to the latitude of the location of the clock. We will also find out what the orientation of the gnomon needs to be. <\/span> <\/p>\n\n

Dad: <\/b>You are very lucky to have chosen today to do your construction. The weather forecast for today is very good. Truly, I am full of anticipation to see the results.<\/span><\/p>\n\n

Now Daphne takes the lead and tells little A to bring a stick that looks like the gnomon in the picture. You have to pin it to the earth so that it is parallel to the axis of the earth. So, they need to find the north pole of the Earth and the angle f<\/i><\/span><\/p>\n\n

Mom: <\/b>But how do we find the north pole from where we are? <\/span> <\/p>\n\n

Mr A<\/b>: This is very easy. Mom, make us sandwiches, put some juice on them and leave them on the kitchen table. Tomorrow morning Daphne and I will tell you exactly where the north pole is. <\/span><\/p>\n\n

Mom<\/b>: I know very well that there is a geographic and a magnetic pole of the Earth. They do not coincide. Do you know which one you have to find for the sundial? Is it better to wait for Captain GG to return from his trip to help;which forms the axis of the Earth with the ground.<\/span><\/p>\n\n

Daphne<\/b>: I asked my dad, who is an astronomer, and he told me that since the stick we are going to stick into the Earth must be parallel to the Earth’s axis, we have to find the geographic north pole. <\/span> <\/p>\n

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The Earth’s magnetic field.<\/figcaption><\/figure><\/div>
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Mr A<\/b>: So we did well to ask for the sandwiches. We’ll stay the night and find the polar star. <\/span>Mr. A and Daphne’s goal is to find the polar star in the night sky. The polar star shows where the north pole is. The two of them are going to stay up all night eating the sandwiches their mom made for them so they can find the polar star.<\/span><\/p>\n\n

Night. Mr. A and Daphne are enthusiastically preparing for the job they have taken on. <\/span><\/p>\n\n

Daphne: <\/b>I’m sure, Mr. A, that you know how to find the Big Dipper in the night sky. Right? <\/span><\/p>\n\n

Mr A: <\/b>This is too easy, Daphne. Who doesn’t know how to find the big pot? It’s so easy. But I always have trouble finding the Little Dipper. <\/span><\/p>\n\n

Daphne: <\/b>Look carefully at the photo of the two pots and pans. You just extend one side of the big <\/span>Bear five times and you fall on the polar star that is at the edge of the little bear’s hand.<\/span><\/p>\n\n

Mr A: <\/b>It’s getting dark for good. Tonight is an extremely clean night. Not a cloud hides the sky. It’s hot, too. It’s very pleasant to sit outside, eat sandwiches and look up at the sky looking for the polar star. I found the Big Dipper! What did you say, Daphne, that I have to do to find the North Star? <\/span><\/p>\n\n

Daphne: <\/b>You extend five times on the far side of the Big Dipper and fall on the polar star. <\/span> <\/p>\n\n

Daphne: <\/b>We found where the north is: where the village is across the road. <\/span> <\/p>\n\n

Mom<\/b>: ‘Good for you. You two are a great team! You also ate all the sandwiches I made last night. Were they tasty? <\/span><\/p>\n\n

Mr A<\/b>: You always say nice things! A thousand thanks. The truth is that we are having a great time together. We both like to explore and learn new things.<\/span><\/p>\n\n

Mr A: <\/b>Mom, you said Captain GG was coming tonight, didn’t you? <\/span> <\/p>\n\n

Daphne: <\/b>Now we need his help to find the angle that the stick we are going to poke into the Earth should be at with the plane of the Earth. If he’s a captain, he should know. My dad told me that the angle we are looking for is equal to the latitude of the place where we want to make the sundial. Captain GG must be able to calculate the latitude and longitude of any point on Earth.<\/span><\/p>\n\n

Mom: <\/b>Captain GG came last night from Crete where he was. He also brought two cheeses from there. I’ll cut you a few pieces of the Cretan gruyere he brought. I’m going to save the myzithra to make myzithro pies, which I love. He also brought a strange instrument.<\/span> He told me to tell you that he would come at dusk to explain what it is and how we can use it to find the latitude(f<\/em>) of a place. <\/p>\n

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The Exodus<\/strong> <\/span><\/h3>\n\n

Dad<\/b>: Tonight is a lovely, warm August evening. I say we grill something to eat with the purple broccoli. <\/span><\/p>\n\n

Captain GG<\/b>: Good evening. Did you like the cheeses I brought from Crete? I hear you want to make a sundial using astronautics. Well, to make the construction you want, you need to know where north is and the latitude of the place where you are going to make the clock. Look carefully at the shape. <\/span>\u03c6 <\/span><\/i>is the angle you want to measure. Look carefully at the shape with the corners. Remember some very simple corner relationships you learned in school. You will discover that latitude(\u03c6<\/i>) is equal to the angle formed by the horizon of place A with the line pointing in the direction of the polar star.<\/span><\/p>\n\n

Mom<\/b>: Could you explain the shape first?<\/span><\/p>\n\n

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The figure shows the spherical Earth. The latitude and longitude of a place are respectively \u03c6 and \u03bb.<\/figcaption><\/figure>\n

Captain GG<\/b>: Of course, my pleasure. S.P. and N.P. are the south and north poles respectively, M is the center of the Earth, A is the place on the Earth on which we want to calculate the <\/span>latitude (<\/span>\n \u03c6<\/span>\n<\/i>), for example your garden. HH is the horizon of place A. <\/span><\/p>\n\n

Suppose the polar star is just above the north pole and its light is coming towards Earth as shown in the figure. <\/span><\/p>\n\n

Our goal is to measure the angle <\/span>\n \u03c6. <\/span>\n<\/i> <\/p>\n\n

Daphne<\/b>: Exactly, this is the angle we need to make the sundial. <\/span> <\/span><\/p>\n\n

Mr A<\/b>: So, if I understand correctly, we have to measure the angle that the horizon makes with the rays from the polar star. <\/span> <\/p>\n\n

Captain GG: <\/b>The instrument we use to make this measurement is the extractor. This is the instrument I brought you and we’re going to use it to do the measurement. Of course, there are now modern ways to calculate exactly where we are on Earth. <\/span><\/p>\n\n

Daphne: <\/b>GPS is called. Global Positioning System (GPS). This system uses the data we get from satellites orbiting the Earth.<\/span><\/p>\n\n

Mr A: <\/b>I can find that with the <\/span>\n smart phone. <\/span>\n<\/i>I have. <\/span> <\/p>\n\n

Daphne: <\/b>But in case this system stops working for whatever reason, we won’t be able to go home, eat and sleep.<\/span><\/p>\n\n

Mr A: <\/b>That’s why we must always have another way to find out where we are. <\/span> <\/p>\n\n

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