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Odal
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Let us say we form a circle with stick, just like a sundial. But instead of one stick in the center, we put sticks all around on the circle. Will the shadows all point in the same direction?
I have no way of trying it, and I would prefer to avoid presenting personal theories. I would like to have the "official answer" from established science.berkeman said:What do you think is the answer, and why? And have you tried it?
That's admirable, but in this case we want to know what your thinking is on it. Try sketching it from several angles to try to get an idea.Odal said:I would prefer to avoid presenting personal theories.
Is there no sunshine where you live?Odal said:I have no way of trying it,
Odal said:I have no way of trying it,
Odal said:let us say I am in jail and I am not allowed to have sticks.
You are being unnecessarily rude. You know nothing of my personal circumstances and you do not need to know anything about them. There is something like privacy, maybe you have heard of it. You do not need to answer the question, but I certainly do not need to answer to yours about my personal life.ZapperZ said:Then, next time you get your "playtime" outside, ask a few of the other inmates to stand still, and look at their shadows.
Zz.
Odal said:You are being unnecessarily rude. You know nothing of my personal circumstances and you do not need to know anything about them. There is something like privacy, maybe you have heard of it. You do not need to answer the question, but I certainly do not need to answer to yours about my personal life.
If nobody is willing to answer this question then so be it.
The question is very simple. It has everything to do with the way light propagates. If it propagates in all directions, we should have shadows going in all directions, while if they all point in the same direction that would mean that the sun somehow functions like a directed spotlight. Out of respect for the forum rules I want to avoid any speculation and hear what science has to say on this simple matter. I do not need you to teach me fishing nor to spoonfeed me.ZapperZ said:And you are being unnecessarily presumptuous. I do not care about knowing about your personal life. What I was trying to do was to teach you how to fish, rather than just give you the fish! It was trying to get you to think and give you the ability to get the answer yourself, so that the next time you have a similar question, you will find the satisfaction in knowing that you are capable of thinking things through and arriving at an answer!
But somehow, everyone nowadays simply wants to be spoonfed!
Zz.
Odal said:The question is very simple. It has everything to do with the way light propagates. If it propagates in all directions, we should have shadows going in all directions, while if they all point in the same direction that would mean that the sun somehow functions like a directed spotlight.
It propagates (ignoring diffraction, refraction, reflection and other sorts of scattering) in straight line paths from the source. If the source is in the east, one expects shadows to point westward, not eastward.Odal said:If it propagates in all directions
I have trouble picturing this and I hope you will help further clarify the matter.Drakkith said:Light is emitted from the Sun in all directions, but rays from anyone point on the Sun are extremely close to parallel to each other by the time they arrive on Earth, so the shadows all fall in the same direction.
The sun is that one location. The rays from the sun which reach the Earth are the rays that were emitted in the direction of the earth. They are nearly parallel.Odal said:then it somehow meets at one location from which parallel rays are emitted?
There was a chain of thought between those two conditions. Have you done any other thinking and reading about this, apart from moaning when the answer is not just dropped into your lap?Odal said:First light goes in all directions, then it somehow meets at one location from which parallel rays are emitted?
If that is the case, how come we can see all of the sun? It is after all immense, in fact almost infinitely large relative to the retinal image.jbriggs444 said:The sun is that one location. The rays from the sun which reach the Earth are the rays that were emitted in the direction of the earth. They are nearly parallel.
The rays that go in all other directions do not reach the Earth and are irrelevant to us.
Google "Angle subtended by an object"Odal said:If that is the case, how come we can see all of the sun? It is after all immense, in fact almost infinitely large relative to the retinal image.
It all depends on the location of the light source. Sunlight is from so far away, that it's rays can be considered parallel, in which case the shadows on such relatively small objects like a couple of sticks on a circle all point into the same direction - away from sun.Odal said:The question is very simple. It has everything to do with the way light propagates. If it propagates in all directions, we should have shadows going in all directions, while if they all point in the same direction that would mean that the sun somehow functions like a directed spotlight.
That is not an answer. I know what a subtended angle is. It would refer me back again to the explanations just given.sophiecentaur said:Google "Angle subtended by an object"
You see the bit of the sun on the left because that bit of the sun emitted some rays of light that happen to strike the pupil of your eye. You see the bit of the sun on the right because that bit of the sun also emitted rays of light that happen to strike the pupil of your eye. Those rays are almost parallel, but not quite. They illuminate (and damage) separate points on your retina. So please do not stare at the sun.Odal said:If that is the case, how come we can see all of the sun? It is after all immense, in fact almost infinitely large relative to the retinal image.
This is a very liberal definition of "almost parallel" when you consider the dimensions of the sun and the eye.jbriggs444 said:Those rays are almost parallel, but not quite.
Odal said:I have trouble picturing this and I hope you will help further clarify the matter.
First light goes in all directions, then it somehow meets at one location from which parallel rays are emitted?
Replace the sticks with human observers looking (!) at the sun each from his position. They each see all of the sun. So, every point in space propagates the image of the whole sun?
Odal said:If that is the case, how come we can see all of the sun? It is after all immense, in fact almost infinitely large relative to the retinal image.
sophiecentaur said:Google "Angle subtended by an object"
Odal said:That is not an answer. I know what a subtended angle is. It would refer me back again to the explanations just given.
A matter of taste, certainly. About 1/2 of a degree difference in angle. The dimensions of the eye are insignificant. The distance to the sun and its size are relevant.Odal said:This is a very liberal definition of "almost parallel" when you consider the dimensions of the sun and the eye.
Odal said:let us say I am in jail and I am not allowed to have sticks.
ZapperZ said:Then, next time you get your "playtime" outside, ask a few of the other inmates to stand still, and look at their shadows.
Not at all. You volunteered the information that you are in jail (or at least suggested that we could assume that).Odal said:You are being unnecessarily rude.
This is the attitude that earned you the 10-day timeout.Odal said:You know nothing of my personal circumstances and you do not need to know anything about them. There is something like privacy, maybe you have heard of it. You do not need to answer the question, but I certainly do not need to answer to yours about my personal life.
You have answered your own question. The retinal image is smaller than the sun, so it fits onto the retina.Odal said:If that is the case, how come we can see all of the sun? It is after all immense, in fact almost infinitely large relative to the retinal image.
The purpose of studying the direction of sundial shadows is to understand the movement and patterns of the sun, which can provide valuable information for navigation, timekeeping, and astronomical observations. It can also help us gain insight into the Earth's rotation and its relationship with the sun.
The study involves setting up a sundial in a specific location and recording the direction of the shadow cast by the gnomon (the vertical stick on the sundial) at different times of the day. This data is then analyzed and compared with other factors such as the location's latitude, the Earth's tilt, and the sun's declination to understand the directional changes of the sundial's shadow.
The direction of sundial shadows can be affected by several factors, including the location's latitude, the Earth's tilt, the sun's declination, and the time of the year. Other factors like the topography of the area, the height and angle of the gnomon, and the accuracy of the sundial's markings can also play a role.
The direction of sundial shadows varies at different latitudes due to the Earth's tilt and its relationship with the sun. At the equator, the sun is directly overhead at noon, causing the shadow to point north or south. As you move towards the poles, the angle of the sun decreases, resulting in longer shadows pointing towards the opposite direction. At the North and South poles, the shadows will point towards the east or west, respectively.
The direction of sundial shadows is not always the same as the direction of the sun because of the Earth's tilt and its elliptical orbit around the sun. This results in the sun's apparent movement in the sky, causing the shadows to change direction throughout the day. Additionally, factors like the location's latitude and the sundial's accuracy can also contribute to the differences in direction.