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As the moon now passes its last quarter, the angle between the moon and sun continues to get smaller.
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It is approaching the New Moon phase, when the angle between them shrinks to zero, that is, it would become zero under a particular condition which occurs every so often, called an eclipse of the sun.
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If there is no eclipse at the New Moon, then the angle between the sun and moon gets very small, down to just a few degrees, or one degree or even less. There can only be a total solar eclipse at the moment of the New Moon.
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With the "flat" earth model, none of this is happening, but we can literally see that it in fact DOES happen. Therefore the "flat" earth model is a myth.
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