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How do they come to the world? One of my friends who is a flat earther told me about how the rays seem to gather at one point, which sort of proves that the sun is close to us and not very big, in his opinion. He thinks that the rays should come parallel, as the sun is much bigger than the world. We were also taught that they come parallel, as shown in the image.

enter image description here

However, what had me thinking is that the sun isn't that big from our point of view. When we look at it, it just seems like a small marble, and this makes it a small spherical light source. It being small makes it act like a point light source in my opinion, and this means the light rays do not come to the world as in the image, but with different angles. I also think that to see a spherical light source's light rays coming parallel toward us, the source must cover all of our horizon, but this is not the case for the sun since it seems just like a marble from the earth.

Can anyone please explain this to me? Is the image not the correct way to teach this?

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  • $\begingroup$ Bring your friend to a long road and ask him if the sides look to converge. After he says yes ask him if they are parallel.... $\endgroup$
    – Alchimista
    Oct 12 '20 at 10:51
  • $\begingroup$ @CarlWitthoft OP asks "Can anyone please explain this to me?" That's exactly what SE is for. Your quips might seem cute but no need to block all users from the opportunity to post an answer and for future readers to see them in order to make a joke. voting to leave open $\endgroup$
    – uhoh
    Oct 13 '20 at 17:07
  • $\begingroup$ Please see Why do sunbeams diverge even though the sun is much more than a few kilometers away? from the Physics site. Nathaniel's answer is excellent, and there are useful images and other info (on or linked) on that page. $\endgroup$
    – PM 2Ring
    Oct 14 '20 at 19:24
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The are parallel. The picture is way off scale. Here is a scale picture of the sun and Earth

enter image description here

Oh dear! the Earth is too small to be seen! Even the Earth and moon look to be in the same place. Rays of light that are hitting your neighbourhood are coming in parallel. The light from the top of the sun and the bottom of the sun are not quite parallel (the lines in the diagram slightly converge) but light from on point on the sun will hit the all the places in your neighbourhood in exactly the same direction.

Let's zoom in

enter image description here

There's the Earth, and two rays from the sun. Are they parallel? No there is an angle of 0.00052 degrees between them. The angle is only so large because the distance between the ends of the rays is a lot (about the distance from Mexico to Canada). If I'd put the ends of the rays closer together the angle would have been much less. To all intents and purposes the rays are parallel.

What you describe is an optical illusion. When the sun shines through gaps in the cloud you will see several parallel rays coming towards you. Because they are coming towards you, they will appear to diverge, just like railway track appear to diverge as they come towards you. But with railway tracks we can see that they are coming towards us, because they are on the the ground. With the parallel rays of sunlight, there are no clues, and we see them as shining down, and so being non-parallel. Its an optical illusion.

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