Chemical & non-chemical life

FYOS 1001

Lecture 2

Various Alien Life Forms

Because of our limited perception, we may be quite biased as… a person in a small local Chinese village may convince that only the Chinese language exists in the world (since it is the only one spoken by all the people around!)…

Life can take place in a wide variety of environments very different from Earth their life forms can be quite different from us, in harmony with their local

conditions. a life can arise from repeated interactions among its constituent subunits…

Barnard 68 : Dark Cloud

Non-chemical Life? • “Black cloud”In the science fiction written by a British

astronomer, Fred Hoyle…

Giant interstellar cloud Can think and move Networks of molecules brain Indefinite lifetime Thoughts radio message from one part to

another Starlight = energy source

approached to Earth to replenish its energy…discovered human and make a communication!

? Very low density and very low temperature very slow chemical reaction really long time for evolution…

Non-chemical Life?• Entire galaxy as a living organism

• Life based on gravitational force• Stars are the subunit as atoms in our body• Stars interact on a time scale of many

millions of years.

• If we think that a life can be arisen from repeated interactions among stars…

millions of such interactions are needed for life to begin at the molecular level.

Universe is far too young to have such life forms!

Non-chemical Life?Life on Neutron Stars

• Strong force based life… • Surface temperature ~ 1million degrees,

enormous gravity… no molecules (not even atom) can survive.

• Nuclei would last for only 10-15 second, however this can be equivalent to a lifetime!

evolution (or change in life) happens fasterEntire civilizations could rise and fall a million

times while a human eye can wink.

If true, no meaningful way to communicate with them.

Frank Drake…

• Human (170cm) with a speed of about 1m/sec with 70 years of lifetime 1 billion times of its body size…

• Nuclei of size 10-13 cm with speed of 1000 km/sec and lifetime of 10-15 second travel distance = 10-15 sec*1000 km/sec = 10-12 km = 1 million times of its body size!

Let’s Focus on life forms that we can perceive and possibly communicate

Chemical Life Forms

Predestinists• Key chemicals in our Earth biochemistry are

inevitable results of random chemical synthesis throughout the Universe!

organic syntheses in the Universe have a direction that favors the production of amino acids (i.e., building blocks of proteins and nucleic acids).

(with cosmic abundance of light elements,) this suggests that life everywhere will be based not only on carbon chemistry, but the one similar to our own!

CarbaquistsLife elsewhere in the Universe must resemble

that present on Earth, because no other basis for life can exist!

…Life everywhere must be based primarily upon

C, H, N, & O and it can arise only in water…

Learn your biochemistry here on Earth, then you will understand the Life of the Universe!

• Carb (Carbon) + Aqua (Water):

C and H2O are inevitable for life not only on Earth but everywhere in the Universe!

There are 103 elements known to exist.

Why not a life form with an iron skeleton and using methanol?

Earth Life is Carbon-Based• Life on Earth is made from more

than 20 chemical elements, but four elements make up about 96% of the mass.

(right figure) chemical composition of the human body by weight.

Oxygen mostly in H2O

Cell structures and their functions are due to Carbon Carbon-based life!

Any chemical compounds contain C “organic compound”

Relative abundance of chemical elements in the Universe• Cosmic Abundance

How?

via Nuclearsynthesis

Examples of Good pairs areH + F Hydrogen FlorideNa + Cl Sodium Chloride (salt)or 2H + O H2O

Chemical bonding• Elements want to have electrons in certain numbers! 2, 10, 18, etc. • Thus an element with 11 electrons wants to get rid of one electron while an

element with 7 electrons wants to accept one more electron from somewhere

Chemical reactions

Ionic bond : Example of a chemical bonding that makes up salt

covalent bond : sharing an electron (s)

Why Carbon-based?

Any other base element?

Requirements for the base element:o Abundant elemento Combine easily with itself and others

• Advantages of Carbon!Let’s consider all different ways of combining with

Hydrogen…1. Oxygen : H2O and H2O2

2. Nitrogen : NH3 (ammonia) and N2H2 (hydrazine)

3. Carbon : so many different ways… E.g., C90H84 or C167H336, …# of possible isomers for C167H336 = 9×1083

? Can this may be due to the difference in the maximum number of bondings for C (No=4), O (No=2), N (No=3)?

• C60 (Bucky-balls)

Entirely made of Carbon. (superconductor material, etc.)

Silicon-based Life?• Then why not Si-based life?

For example, CH4 (methane), SiH4 (silane).o Si-Si bond strength is ½ of the C-C bondo C-C, C-H, and C-O bond strengths are ~same,

but Si-H and S-O bonds are stronger than Si-Si hard to make a large complex structures (chain, rings, etc.)

o At low temperature, nearly all Si atoms will form SiO2 (quartz!) and this rock-forming material are very difficult to dissociate!

Although life based on silicon may be possible, it will be extremely uncommon at best!

Life based on carbon seems favored as the dominant kind of life in the Universe!

• Si has four “bonds” similar to Carbon.

Carbaquists…no alternative?

Convincing argument…But there are other alternatives for solvent!

• Carbon + water may be the most efficient basis of life in the Universe, but not the only!

• Less efficient bases can be used…Information Storage as an example: o In English :

26 capital, 26 small letters, plus few punctuation marks (~60 “symbols”)

o In computer: 01001001 01101110 00100000 01000101 01101110 01100111 01101100 01101001 01110011 01101000 00100000 00111010 00100000 00110010 00110110 00100000 01100011 01100001 01110000 01101001 01110100 01100001 01101100 00101100 00100000 00110010 00110110 00100000 01110011 01101101 01100001 01101100 01101100 00100000 01101100 01100101 01110100 01110100 01100101 01110010 01110011 00101100 00100000 01110000 01101100 01110101 01110011 00100000 01100110 01100101 01110111 00100000 01110000 01110101 01101110 01100011 01110100 01110101 01100001 01110100 01101001 01101111 01101110 00100000 01101101 01100001 01110010 01101011 01110011 00100000 00101000 01111110 00110110 00110000 00100000 10010011 01110011 01111001 01101101 01100010 01101111 01101100 01110011 10010100 00101001

o In Korean : 26 모음 , 26 자음 , 몇가지 부호 ( 약 60 개 심볼 )

• Cannot be convinced (or refuted) purely based on reasoning and analogy.

A discovery of non-carbon based alien life form quickly solves the issue.

Or a series of discoveries of alien life forms that are all carbon+water…

C

Assign or volunteer?!

• Next Week’s presentationso Nuclearsynthesis (Big Bang, Stellar, and Supernova)o Habitability of Planetso Unique characteristics of Water