Scientific Philosophy : Popper’s Falsificationism

Now I want to talk about some theories about scientific philosophy. I want to introduce a great scientific philosopher Karl Popper(1902-1994) and his theory.

Popper’s theory is called “Falsificationism”(否證論), which means the nature of science is to prove a theory to be false. Every single theory is facing the challenge of experiment. We should derive propositions from theories or hypothesizes waiting to be tested. A scientific theory should have the ability to give a testable statement or prediction. This property is called “Falsifiability”(可證偽性). Therefore we can do experiments to test this theory. These experiments are called “crucial experiment”(決斷實驗). If a theory doesn’t satisfy the demand of falsifiability, it is not a “scientific” theory.

Does a theory pass the test of crucial experiment a correct theory? No! Crucial experiment only prove other theories are wrong. For example, the tests of Einstein’s theory of relativity didn’t prove relativity is correct, but prove Newton’s mechanics are wrong! Relativity is corroborated(被認可) temporarily.

Falsifiability as a definition of science is widely accepted by scientific community. But I cannot totally agree the original definition of falsifiability. In that case, mathematics and string theory are no longer science because they couldn’t give crucial experiment! Maybe we can expand the definition or falsifiability.

Next week I want to introduce another great philosopher Kuhn and his theory. 

We are living in a 11-dimensional world?-String theory and M-theory

　　

　　We are all composed of particles,quarks(夸克) and electrons,which we called elementary particles. In physical theories, we always think these particles as points. Is this idea true? Although this idea had made great contributions, it still has limitation.(Because general relativity cannot combined with quantum mechanics)

　　String theory(弦論)thought all elementary particles are strings. The vibration modes(震動模式) form different kind of particles. In order to make string theory possible, it demand the world has 10 dimensions! We know that we have 3 space dimensions and 1 time dimensions. String theory contains another 6 space dimensions.

　　Where are the 6 space dimensions? They all curled up like small circle(called Calabi-Yau manifold(卡拉比-丘流形)). They are so small that we couldn’t see them.

 

　

　  There are five different string theories before 1995.(In fact,six,the other one called Supergravity(超重力)) Great physicist and mathematician Edward Witten(I think he is the greatest physicist nowadays!) connect these theories by a great idea called duality(對偶性). The five theories are all bases of a bigger theory called M-theory. The theory promote string to brane(膜,2-d),which means the world has 11 dimensions!

　String theory is a very beautiful and difficult physical theory.(perhaps the most difficult one) The ideas are abstract but simple. My introduction is oversimplified, but I hope you will like it. In fact, I want to dedicate my life to study string theory.

Schrödinger's Cat and Many-Worlds Interpretation

　　One of the founder of quantum mechanics, Schrödinger didn’t believe Bohr’s Copenhagen interpretation(哥本哈根詮釋). He issued a thought experiment(思想實驗) called Schrödinger's Cat(薛丁格的貓) in 1935.

　　The details of this experiment are as below:we put a cat, a flask with hydrogen cyanide(氰化氫,毒氣) and a radioactive matter into a box. Within one hour, the decay probablity of the matter is 50％. Once the decay happen, the detector will break the flask and then the cat will die. 

 

　　

　　According to Copenhagen interpretation, after an hour the cat will be in superposition states(疊加態), alive and dead. This is ridiculous because cat cannot be alive and dead simultaneously! If you open the box then the state of cat will collapse to a single state, alive or dead.

　　Another alternative interpretation is Many-worlds interpretation(多世界詮釋), which is well-known as parallel universes(平行宇宙). It is actually a physical theory! The cat is both alive and dead before the observation, but the alive and dead cats are in different branches of universes.

　　MWI indicates that every time we make a decision, there is another “me” in parallel universe chooseing another choice! But the point I want to say is “cat is wretched(可憐的).”, maybe rabbit is a good alternative!