Over the course of the week I was considering what constitutes as sufficient evidence when it comes to science and I think I came up with a good example to demonstrate this. The theory of continental drift originally suggested by Alfred Wegener in 1912. The evidence for this theory is as follows:
- The continents appear to fit together like pieces of a jigsaw puzzle (not the most convincing but at least a good basis to go on). This is made slightly more persuasive when rocks deep underground are looked at as they fit together more precisely.
- Earthquakes can really only be explained through the action of plates and their fault zones and so continental drift is tangentially shown through earthquakes.
- Fossils such as that of the mesosaurus are found specifically in the south of South America and south portion of Africa. This is explained by the fact once these continents were connected and so animals living their died, were fossilised and the fossils were separated by continental drift.
- On a semi related point ammonites being found atop Mount Everest along with grey limestone implies that the top of Everest must have been the bottom of the Indian ocean at some point in the past.
- Britain’s large coal deposits could only have been developed by a rainforest existing for some time in the region, yet there is also evidence of glacial carving. Both of these are unexpected for Britain’s current distance from the equator.
- Evidence for glaciers in India, Africa and Australia would imply the ice sheet covered half the planet if they had always been in their current positions. The grooves bored by these ice sheets show they radiated from a single point meaning the land masses must have huddled around the Antarctic.
- Polarisation of magnetic rocks on the seabed forming bands. This is explained by the fact that the rock is being pushed out of an underwater fissure and when it cools it lines its polarity up with the Earth’s magnetic field. About every 200,000 years the Earth’s polarity switches and so the bands of alternating magnetic rock are formed.
- Finally laser satellites and GPS systems can be used to record the small movement of the continents as direct evidence for the drift.
And despite all this evidence there is still another theory in which the Earth was once much smaller and when it expanded the land on the crust was pulled apart. For a theory to be fully accepted above is the amount of evidence required and even then there will always be a backup theory in the works.
Until tomorrow, goodnight.