| 1901 |
Hugo De Vries's book The Mutation Theory
suggests that changes in species are the result of mutations.
|
| 1902 |
The American biologist Walter Sutton suggests that
chromosomes are paired and may be the carriers of heredity.
In England, William Baylliss and Ernest Starling
demonstrate the importance of hormones in the control and
coordination of the body.
Ernest Rutherford and Frederick Soddy publish
work showing that radioactivity is the result of atomic
disintegration atomic nuclei splitting to form other elements.
|
| 1903 |
The Norwegian chemist Lars Onsager works out a way
of separating uranium-235 and uranium-238 using diffusion.
Antoine-Henri Becquerel with Pierre Curie
and Marie Curie share the Nobel prize for physics
for their work on radioactivity.
|
| 1904 |
The English chemist Sir William
Ramsey wins a Nobel prize for chemistry for his work on
inert gases and their place in the Periodic Table. |
| 1905 |
Clarence McClung shows that female mammals have
2 X chromosomes
and that males have an X
and a Y.
The first direct blood transfusion is performed by George
Crile.
Albert Einstein provides a mathematical explanation
of Brownian motion. Many see this as the first proof that
atoms actually exist. Einstein also publishes his first
and second papers on special relativity, including the famous
equation E = mc2.
|
| 1906 |
Based on his experiments with rats, the English biochemist
Frederick Hopkins suggests that vitamins are ingredients
of food which are essential for life.
Pierre Curie is killed by a brewer's cart, and Marie
Curie becomes the first woman professor at the Sorbonne
in Paris.
|
| 1907 |
In America, Thomas Hunt Morgan
starts working on fruit flies to prove that chromosomes have
a role in heredity and to confirm mutation theory. This work
will lead to a much deeper understanding of the mechanisms
of heredity. |
| 1908 |
The German chemist Fritz Haber
develops his process for extracting nitrogen from the air
and combining it with hydrogen to form ammonia. |
| 1909 |
The terms "gene", "genotype" and "phenotype"
are used for the first time.
Karl Bosch develops an industrial version of the
Haber process.
|
| 1910 |
J J Thomson uses cathode rays to measure the atomic
masses of a number of substances. He shows that neon has
two isotopes - neon-20 and neon-22. This provides the first
proof that isotopes really exist.
In America, Howard Taylor Ricketts shows that Mexican
typhus is transmitted by the human body louse, and then
dies after catching the disease during his research.
|
| 1911 |
The first chromosome maps are developed.
Ernest Rutherford presents his theory of the atom
- a positively charged nucleus surrounded by negative electrons.
|
| 1912 |
The term "vitamin" is used for the first time.
In Germany, Max von Laue shows that X-rays are a
form of electromagnetic radiation.
Alfred Wegener, a German meteorologist, announces
his belief in the idea of continental drift, having noticed
how the coastlines of certain continents seem to fit together
as if they had once been part of a single continent. Most
geologists ridicule his ideas because he is unable to suggest
a way in which the continents might move through the solid
rocks of the Earth's crust.
|
| 1913 |
American biophysicist Britton Chance works with
the enzyme peroxidase and shows that enzymes work by binding
to the substrate.
Vitamins A and B are discovered.
The Danish physicist Niels Bohr publishes work on
the theory of atomic structure in which he sets out his
assumption about the way in which electrons travel around
the nucleus in fixed orbits.
|
| 1914 |
In Germany James Frank and Gustav Hertz carry
out experiments which confirm Niels Bohr's model of the
atom with electrons in different energy levels.
The American Edwin Kendall discovers thyroxine,
the hormone made by the thyroid gland.
|
| 1915 |
The German Richard Willstätter wins a Nobel prize
for Chemistry for his research on chlorophyll in plants.
Albert Einstein completes his general theory of
relativity - he has been working on it since 1911.
|
| 1916 |
In Japan, Kotaro Honda
discovers that adding colbalt to tungsten steel produces a
alloy that produces particularly strong magnets. |
| 1917 |
Heparin, a natural anticoagulant which can be used to stop
blood clotting, is discovered.
Margaret Sanger and Marie Stopes write a
book on birth control.
|
| 1918 |
The first mass spectrometer is
built by English physicist Francis Aston. He uses it
to identify isotopes in a number of different elements. |
| 1919 |
Ernest Rutherford reports that two years earlier
he has artificially split an atom of nitrogen. He describes
the idea that splitting the atom may ever be a source of
energy as "pure moonshine".
American chemist Irving Langmuir develops a theory
of covalent bonding between atoms.
|
| 1920 |
American physicist William
Draper Harkins suggests the existence of the neutron,
a neutral particle in the nucleus. Evidence for the existence
of the neutron will not actually be obtained until 1932. |
| 1921 |
The American chemist Thomas Midgley discovers that
tetraethyl lead prevents "knock" in car engines
- the beginning of lead compounds being added to petrol.
A team of scientists extract insulin from human pancreases
and start experiments on dogs to try and develop a treatment
for diabetes.
|
| 1922 |
Elmer McCollum discovers
vitamin D in cod liver oil and uses it for treating rickets. |
| 1923 |
Johannes Nicolaus Brønstead suggests that
acids produce hydrogen ions in solution, and that bases
accept hydrogen ions in solution.
In France Albert Calmette and Camille Guérin
develop tuberculosis vaccine - the BCG still given in schools
today. (BCG stands for Bacillus Calmette-Guérin.)
|
| 1924 |
Insecticides are used for the
first time. |
| 1925 |
In America Vannevar Bush and his coworkers develop
the first analogue computer, capable of solving differential
equations.
Also in America, George Whipple discovers that iron
is important part of red blood cells.
|
