Re: who are the ten most important scientists of all time?

This is a question that has no answer. It is like asking someone to pick 
the all time great football team, only worse. How do we compare the 
achievements and influence of people who worked in so many very different 
areas of science, in so many different cultural contexts, over a period of 
more than 2000 years?

If I have a go at it, you must remember that the list I come up with will 
be a personal and controversial choice. I am a child of the twentieth 
century. I am a chemist and a physicist. I am an Australian. I speak and 
read English. Any or all of these things may influence the list in quite 
subtle ways.

So here we go. When you say "most important" in your question, I will take 
that to mean "most influential", which is not necessarily the same thing as 
"greatest" or "most brilliant" or "most insightful". I will also take a 
very broad view of science. Some of the "scientists" in my list did not use 
an approach that would be seen today as good scientific method. But I will 
only consider those whose main contribution was to "natural sciences", not 
"social sciences".

There are, in my view, five great scientists who would be likely to figure 
on any such list. 

(1) Aristotle wrote speculations around 400 BC that completely dominated 
European thought about nature for the next 1500 years, and remain 
influential even today. He wrote about physics, astronomy, medicine, and 
biology, trying to find underlying principles. His method was contemplation 
and commonsense knowledge. He deliberately avoided detailed observation and 
experimentation. Surprisingly, he had a good reason. He wanted to 
investigate nature, and as far as he was concerned, any intrusive or 
manipulative investigation would produce artificial or unnatural behaviour 
in the objects being studied.

(2) Galileo's main claim to fame was in his confrontation of the religious 
authorities that he saw as blocking the development of new insights in 
astronomy. He was a champion of direct obsevation, and the authority of 
observational evidence. He made a major contribution to a new attitude to 
experimental science in the renaissance period.

(3) Sir Isaac Newton was able to produce a systematic mathematical 
formulation of mechanics, that gave a precise quantitative basis for 
understanding the motions of earthly objects as well as heavenly bodies. He 
also made major contributions to optics (study of light), and other areas 
of physics.

(4) Sir Charles Darwin, with his idea of evolution by natural selection, 
completely revolutionised attitudes and understandings in biology.

(5) Albert Einstein almost single-handedly developed the theories of 
relativity, that corrected some problems with Newton's mechanics, provided 
most of our modern understanding of gravitation, and gave us completely new 
insights into such fundamental ideas as time and mass.

After that, it gets very hard. I will opt for 

(6) Niels Bohr (quantum theory)
(7) Dmitri Mendeleev (systematization of inorganic chemistry)
(8) Harvey (circulation of the blood)
(9) Leeuwenhoek (development of the microscope and direct observation of 
biological specimens)
(10) J.J. Thomson (collecting experimental evidence about the structure of 
the atom).

I suspect that if you asked a lot of other scientists, they would match me 
on an average of about four of the first five, and one of the last five.

John.