What theories in science have changed?

Answer 1

It would probably be safe to say that there isn't a single theory more than 4 or 5 years old that has NOT changed. It is probably safe to say that not a single theory is beyond the possibility of change in the future. This is in the nature of scientific exploration. This is exciting, and should not be discouraging. Even though our understanding of things changes over time, there is progress. This is not suggesting that every current theory WILL change in time; it is possible that some of our theoretical formulations are solid enough to continue for centuries without significant change. Some of the better known examples of changing theories: It was widely believed in antiquity that the earth was flat; it was later believed that earth was at the center of the solar system. It was believed that the universe was basically a static structure consisting of one galaxy. Most of Newtonian mechanics has been re-framed by Einstein's relativity, and there is a possibility that Einstein will be supplanted by Quantum Theory. It was firmly believed for a very long time that mass and time were absolute physical constants, and we now know that they are not. At one time, people routinely believed in 'spontaneous generation', the idea that some forms of live simply spring into being (like growth on nutrient fluids or food left out for several days). There were popular beliefs that included animal young springing out of certain kinds of plants. Many people believed that escaping the gravity of earth was simply impossible to do. It was believed by many around the dawning of the industrial revolution that earth's atmosphere was so vast, it could never possibly be affected by emissions from machines. Much of the art work from those days portrays colorful, sparkling and powerful images of mills and factories pouring huge billows of smoke into an otherwise brilliant blue and sunlit sky. There are many other f ing examples.

Answer 2

The theory of continental drift, proposed by Alfred Wegener, has evolved into the theory of plate tectonics. The geocentric model of the universe gave way to the heliocentric model with the work of Copernicus and Galileo. The theory of evolution has seen modifications and expansions since it was first proposed by Charles Darwin.