What are examples of how scientific knowledge is open to change ?

Scientific knowledge is inherently open to change because it is based on new observations, experiments, and the development of better theories. Here are a few examples demonstrating how scientific knowledge is subject to change:

1. The Structure of the Atom: The early Greek model of an atom was a solid, indivisible object. This idea changed with Dalton’s solid sphere model. Later, once electrons were discovered by J.J. Thomson, the plum pudding model was proposed. As experiments evolved, Rutherford proposed a nuclear model with a dense center after his gold foil experiment. Finally, Bohr introduced his planetary model with electrons in orbit, leading to the Quantum Mechanical Model, which is the most accepted one today.

2. Germ Theory of Disease: Prior to the germ theory, people believed in the miasma theory, thinking diseases were caused by bad air. This changed with the work of scientists like Louis Pasteur and Robert Koch who demonstrated that microorganisms cause disease. As a result, modern medicine has shifted towards understanding and treating infections.

3. Plate Tectonics: The theory of plate tectonics, which describes the movement of the Earth's lithosphere, is relatively new. Up until the mid-20th century, the theory of continental drift proposed by Alfred Wegener was widely dismissed. It wasn’t until the concept was combined with sea-floor spreading and evidence for tectonic activity became clear that the theory was broadly supported.

4. Newtonian Physics to Relativity and Quantum Mechanics: For centuries, Newtonian physics with its laws of motion and universal gravitation were considered the gold standard. However, observations that could not be explained by Newton's laws, like the orbit of Mercury and the behavior of light and energy at an atomic level, led to the development of Einstein's Theory of Relativity and Quantum Mechanics.

5. Evolution: The understanding of the process of evolution is always expanding. Charles Darwin's Theory of Natural Selection fundamentally changed the way we understand the diversity of life. Since then, with the discovery of genetics, scientists like Gregor Mendel and later the modern synthesis with population genetics have refined evolutionary theory to a more detailed and comprehensive level.

These examples reflect how scientific ideas can be refined, altered, or even discarded in light of new evidence and better explanations of natural phenomena.