What are other scientific theories that has changed?

Answer 1

Einstein's Static UniversePrior to scientists embracing the notion that the universe was created as the result of the Big Bang, it was commonly believed that the size of the universe was an unchanging constant-it had always been the size it was, and always would be. The idea stated that that the total volume of the universe was effectively fixed, and that the whole construct operated as a closed system. The theory found its biggest adherent in Albert Einstein-the Static Universe is often known as "Einstein's Universe"-who argued in favor of it and even calculated it into his theory of general relativity.

How it was Proven Wrong:

The theory of a static universe was problematic from the start. First of all, a finite universe could theoretically become so dense that it would collapse into a giant black hole, a problem Einstein compensated for with his principle of the "cosmological constant." Still, the final nail in the coffin for the idea was Edwin Hubble's discovery of the relationship between red shift-the way the color of heavenly bodies change as they move away from us-and distance, which showed that the universe was indeed expanding. Einstein would subsequently abandon his model, and would later refer to it as the "biggest blunder" of his career. Still, like all cosmological ideas, the expanding universe is just a theory, and a small group of scientists today still subscribe to the old static model.

The Expanding EarthOur modern understanding of the interior and behaviors of the Earth is strongly based around plate tectonics and the concept of subduction. But before this idea was widely accepted in the late 20th century, a good number of scientists subscribed to the much more fantastical theory that the Earth was forever increasing in volume. The expanding Earth hypothesis stated that phenomena like underwater mountain ranges and continental drift could be explained by the fact that the planet was gradually growing larger. As the globe's size grew, proponents argued, the distances between continents would increase, as would the Earth's crust, which would have explained the creation of new mountains. The theory has a long and storied past, beginning with Darwin, who briefly tinkered with it before casting it aside, and Nikola Tesla, who compared the process to that of the expansion of a dying star.

How it was Proven Wrong:

The expanding Earth hypothesis has never been proven wrong exactly, but it has been widely replaced with the much more sophisticated theory of plate tectonics. While the expanding Earth theory holds that all land masses were once connected, and that oceans and mountains were only created as a result of the planet's growing volume, plate tectonics explains the same phenomena by way of plates in the lithosphere that move and converge beneath the Earth's surface.