1. Would ocean tides exist if the gravitational pull of the moon (and sun) were somehow equal on all parts of the world? I know it's no but why?
2. With respect to spring and neap ocean tides, when are the lowest tides? That is, when is it best for digging clams?
3. The human body is composed of mostly water. Why does the gravitational pull of the moon overhead cause appreciably less biological tides in the fluid compartment of the body than the gravitational pull of a 1 kg melon held over your head?
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1. No, ocean tides would not exist if the gravitational pull of the moon (and sun) were equal on all parts of the world. This is because tides are primarily caused by the gravitational interaction between the moon and the Earth's oceans. The moon's gravitational pull causes a tidal bulge on the side of the Earth facing the moon, and another tidal bulge on the opposite side of the Earth. This creates two high tides and two low tides each day as the Earth rotates. If the gravitational pull were equal everywhere, there would be no variation in the tidal forces and hence no tides.
To understand this, you need to be familiar with the concept of gravitational forces and how they vary with distance. The gravitational force between two objects decreases as the distance between them increases. The moon's gravitational pull is stronger on the side of the Earth nearer to it, while it is weaker on the opposite side. This difference in gravitational forces is what creates the tidal bulges and thus the tides.
2. The lowest tides, which are ideal for digging clams, occur during neap tides. Neap tides happen when the gravitational pull of the moon and the sun act at right angles, causing them to partially cancel each other out. This results in lower tidal range, meaning the difference between high tide and low tide is smaller compared to other times.
Neap tides occur during the first and third quarter moon phases, when the moon is at a right angle to the Earth and the sun. During these times, you would typically find lower tides, exposing more of the shoreline and making it easier to access areas where clams are found.
3. The human body is indeed composed mostly of water, and like the Earth's oceans, it experiences the gravitational pull of the moon. However, the gravitational pull of the moon on the human body is so weak compared to other forces acting on our bodies that it does not cause appreciable biological tides in the fluid compartment.
The gravitational force between two objects depends on their masses and the distance between them. The mass of the moon is much smaller compared to a 1 kg melon held over your head, and the distance between the moon and your body is much larger compared to the distance between your head and the melon. These factors result in a significantly weaker gravitational force from the moon on your body.
Additionally, the human body is well-adapted to counteract external forces, including gravity. Our circulatory and lymphatic systems, as well as our muscles, play a role in maintaining fluid balance within our bodies despite the weak gravitational pull of the moon.