Mysteries of tides and what they mean to us

Tides are a fascinating subject, especially in Port Alfred and the Sunshine Coast where people live close to the sea and tidal rivers and feel their rhythms.

Foragers looking for mussels and other wild delicacies, and fishermen, are especially keen tide watchers.

Port Alfred tide watchers have a great advantage with the presence of Prof Don Kurz, who entertained the Friends of Waters Meeting recently with a talk at the Ploughman’s Pub at the Agricultural Showground in Bathurst, titled “Tides: From the Bay of Fundy to Black Holes ”.

Kurz is a renowned astrophysicist who retired in Port Alfred in 2020.

He is best known for his contributions to the study of supernovae, black holes, and dark matter. He has published more than 200 prestigious journals and lectured at various universities, including as a professor for 25 years at the University of Cape Town.

Kurtz is a passionate educator. He captivated the audience of some 80 people who bombarded him with questions.

Perhaps the rare occurrence of the recent Blue Moon garnered interest.

Tides are the periodic rise and fall of the sea level caused by the gravitational forces of the moon and the sun on the Earth and other celestial bodies.

But how much do we know about tides? How do they affect our planet and beyond?

Kurz showed some examples of extreme tides, such as the Bay of Fundy in Canada, which has the highest tidal range in the world, reaching up to 16m.

But tides are not only limited to the oceans. Kurtz also discussed how tides affect other bodies of water, such as lakes and rivers, and even the atmosphere.

He also revealed how tides can influence the Earth’s rotation, shape, and climate, as well as cause earthquakes and volcanoes. He also explained how tides can create some fascinating phenomena, such as tidal bores, which are waves that travel upstream in a river due to the incoming tide, and tidal locking, which is when one side of a celestial body always faces another celestial body due to tidal forces.

For example, the moon is tidally locked to the Earth, meaning we always see the same side of it.

But perhaps the most intriguing part of his talk was when he explored how tides can affect objects in space, such as planets, moons, stars, and even black holes.

He explained how tides can heat up planets and moons by friction caused by tidal forces. For example, Jupiter’s moon Io is tidally heated by its interaction with Jupiter and other moons, making it volcanically active.

He also explained how tides can tear apart objects that come too close to a massive body. For example, a satellite that comes within the Roche limit of a planet will be ripped apart by tidal forces.

Tides can create black holes by collapsing massive stars that rotate very fast.

Some of the applications and implications of tides for science and humanity include how they can be used as a source of renewable energy by harnessing the kinetic energy of moving water.

And best of all, tides can shed light on the origin and evolution of life on Earth.