Tidal Misconceptions

You may have heard that oceanic tides are dependent on the phases of the Moon, but this is a common misconception. In reality, oceanic tides do not even physically rise or fall!

Tidal Waves are only

Consider the Sun-Earth-Moon system. From the below diagram we can see that the Earth is surrounded by two bulges of water on either side, caused by the gravitational pull of both the Sun and the Moon. The Earth simply rotates inside this bulge, causing the water levels to fluctuate depending on its location from the bulge! Therefore, the tides themselves don’t change, rather they go high and low with respect to our location on the surface of the Earth, which in turn rotates inside this bulge.

Similarly, we tend to associate a full/new Moon with higher tides, but this is not true. The 2 bulges mentioned above are respectively created by the gravitational forces exerted by the Moon AND the Sun. Although it is partially true to associate full Moons with high tides, it in fact occurs due to the alignment of the Sun-Earth-Moon system. The tides the Moon raises are the same regardless of its phase. During a full moon, the Moon and the Sun are in line and opposite to the Earth. The cumulative effect of the gravitational forces exerted by both the Sun and the Moon causes the opposite bulges to bulge ever further, giving rise to higher tides! This phenomenon is termed Syzygy.

The lowest tides are recorded when the Sun-Earth-Moon system is at a right angle. The reason is, the forces exerted by the Sun and the Moon would cause the overall magnitude of the tides to decrease as they pull at a 90o angle. This phenomenon is called a Neap Tide. Oh, and did you know that the rotation of the Earth is slowing down because of the tidal forces exerted by the Moon? This happens due to Earth dragging the bulge away from the line of the Moon while it rotates. The Moon however wants to realign the bulge to face towards it, and tugs on the moving bulge against the direction of the Earth’s rotation. This causes the Earth’s rate of rotation to slow down. This is also why we introduced the concept of leap seconds so that our perception of time doesn’t alter. Hence, the slowing down of Earth’s rotation increases the length of a day by 1.8 milliseconds per 100 years. This means that the duration of a day 600 million years ago was only 21 Hours! However, the rotational energy has to be conserved, so where does it go? The rotational energy is transferred onto the Moon, causing its orbit to elongate, making it drift further away from the Earth by about 1.5 inches every year!

You may have heard superstitious folks talking about how the phases of the Moon affects us humans on Earth. Now one may consider this as a superstition, but instead, it is a vastly exaggerated ideology of a real phenomenon. The Moon creates a tidal force across everything, including us humans. The side of your body closer to the Moon is pulled slightly more than the side of your body away from the Moon. So, there is some truth to the superstition, as the Moon does indeed ‘affect’ human beings, but not in the way we believe it to be. The difference in gravitational forces exerted on the 2 sides of your body, one closer and one further away from the Moon is a TRILLION times weaker than the force your pillow exerts on your head when you lie down! Therefore, if the forces exerted by a pillow are not able to completely distort your head, then the tidal forces exerted during a full moon, or any other phase does not even stand a chance.