Astrobiology and the Search for Extra Terrestrial Life
The University of Edinburgh
Lecture Summary: Life on Earth
The Basics of Life
What is Life?
We should consider that there is no fixed definition for Life or what constitutes Life entirely.
The definition and understanding of Life were first observed by the Greeks and then during
the European Enlightenment.
How the Greeks saw Life: Materialism
- Life has a soul
- The soul is made up of a certain atomic material
→ Empedocles asserted that the soul was made up of either air/water/Earth/fire
→ He believed that the soul was made up of atoms of fire because Life seems
lively
How the European Enlightenment saw Life: Vitalism
- Life contains a vital force
- When this vital force is added to something non-biological, it becomes biological
- Life has a characteristic making it categorically different
- This led to the idea of spontaneous generation
These early thoughts are important because it shows that right from the beginning of early
definitions, people believed that there was something special about Life; something that
separates us from the non-living.
, Important experiments conducted during the European Enlightenment:
Experiment by Dr. Francesco Redi
Dr. Redi theorized that maggots might not be produced by spontaneous generation, but by
flies buzzing around the meat.
Vitalism is: Non-living + Living = Living
Vitalism is: Meat + Flies = maggots
Conclusion:
The meat didn’t spontaneously give rise to Life, it had to be accessed.
Experiment by Louis Pasteur
Similarly, to Dr. Francesco Redi, Louis Pasteur believed that the non-biological material needs
to be accessed in order to give rise to Life.
- He developed swan-necked flasks
→ The swan-neck prevented any microbes or other Life forms from getting in
- He put broth in both flasks and boiled it to eliminate the presence of bacteria or other
forms of Life
- He left them closed, and after a few days, nothing happened
- He then broke the neck of one of the flasks, exposing it to the outside world
- After a few days, the broth became turbid because micro-organisms were growing in
the broth
Conclusion:
The broth didn’t spontaneously give rise to Life, it had to be accessed first.
The result of these experiments:
- Ended the idea of spontaneous generation
- Also showed that micro-organisms were responsible for Life emerging in different
materials
This is why it is said that Life is a working definition
It’s important to keep an open mind that alien Life may not fit our definition of Life, but the
definitions we do have allows us to search for Life elsewhere and study the structure of Life
we’re familiar with.
The University of Edinburgh
Lecture Summary: Life on Earth
The Basics of Life
What is Life?
We should consider that there is no fixed definition for Life or what constitutes Life entirely.
The definition and understanding of Life were first observed by the Greeks and then during
the European Enlightenment.
How the Greeks saw Life: Materialism
- Life has a soul
- The soul is made up of a certain atomic material
→ Empedocles asserted that the soul was made up of either air/water/Earth/fire
→ He believed that the soul was made up of atoms of fire because Life seems
lively
How the European Enlightenment saw Life: Vitalism
- Life contains a vital force
- When this vital force is added to something non-biological, it becomes biological
- Life has a characteristic making it categorically different
- This led to the idea of spontaneous generation
These early thoughts are important because it shows that right from the beginning of early
definitions, people believed that there was something special about Life; something that
separates us from the non-living.
, Important experiments conducted during the European Enlightenment:
Experiment by Dr. Francesco Redi
Dr. Redi theorized that maggots might not be produced by spontaneous generation, but by
flies buzzing around the meat.
Vitalism is: Non-living + Living = Living
Vitalism is: Meat + Flies = maggots
Conclusion:
The meat didn’t spontaneously give rise to Life, it had to be accessed.
Experiment by Louis Pasteur
Similarly, to Dr. Francesco Redi, Louis Pasteur believed that the non-biological material needs
to be accessed in order to give rise to Life.
- He developed swan-necked flasks
→ The swan-neck prevented any microbes or other Life forms from getting in
- He put broth in both flasks and boiled it to eliminate the presence of bacteria or other
forms of Life
- He left them closed, and after a few days, nothing happened
- He then broke the neck of one of the flasks, exposing it to the outside world
- After a few days, the broth became turbid because micro-organisms were growing in
the broth
Conclusion:
The broth didn’t spontaneously give rise to Life, it had to be accessed first.
The result of these experiments:
- Ended the idea of spontaneous generation
- Also showed that micro-organisms were responsible for Life emerging in different
materials
This is why it is said that Life is a working definition
It’s important to keep an open mind that alien Life may not fit our definition of Life, but the
definitions we do have allows us to search for Life elsewhere and study the structure of Life
we’re familiar with.
