So why did my flinch? Because the laws of science differ fundamentally from those of... Dear Science, I thought that eclipse had happening in August. I heard that the shadow is moving from west to east. But how can that be possible since the moon moves from east to west? Hi, I'm Sarah Kaplan and I'll be answering for science today. On August 21st something really exciting is going to happen in the US. A total solar eclipse. This is what happens when the moon passes in front of the sun and it's going to cast a shadow that travels across the United States all the way from the Oregon coast to South Carolina. But wait. The moon rises in the east and sets in the west. Why is the shadow moving from west to east? This is actually a really big question and even astrophysicists sometimes have trouble answering it. Let's see if any of my colleagues can help. So we're trying to figure out why is it that the eclipse goes from west to east if the moon rises in the east and sets in the west. If we're on the planet and we're looking up, shouldn't they be traveling the same direction? Yeah, I think so. Well, it has to do with rotation and revolution. Yes. And do you know the earth is spinning this way. So in the moon is spinning the same way that the earth is orbiting. I see. But the earth is spinning faster than the moon is orbiting. See, this is why I said biology. I, OK. Andalusia. So I'm spinning this way, right? I'm, but you're running really faster. Yeah, exactly. Clearly, we need to consult an expert on this. So we went to NASA's Goddard Space Flight Center in Maryland to talk to Alex Young, a NASA scientist, and ask for his best explanation. To try to make it as simple as possible, it really boils down to how fast the earth is spinning and how fast the moon is orbiting around it. The moon is orbiting about twice as fast as the earth is spinning. So if we're looking down on the earth and we're at the moon, we see the earth spinning, but the moon is moving faster. So that shadow is moving across the earth this way, which is west to east. Simple, right? Don't worry. Over the next few months, we'll be answering a lot of questions about the eclipse. Just send an email to Dear Science and maybe we'll answer yours.