NSCI 314 LIFE IN THE COSMOS 11 - WHERE TO SEARCH FOR LIFE OUTSIDE OUR SOLAR SYSTEM: EXOTIC LIFE Dr. Karen Kolehmainen Department of Physics, CSUSB

ADVANTAGES OF PLANETS AND LARGE MOONS FOR LIFE CONDUCIVE TO CHEMISTRY (ATOMS COMBINING AND RECOMBINING TO FORM MOLECULES)‏ PROVIDE A RELATIVELY STABLE AND PROTECTED ENVIRONMENT (AT LEAST IN MANY CASES)‏ SMALL VARIATIONS IN ENVIRONMENT VARIETY OF INTERFACES BETWEEN LAND, OCEANS, AND ATMOSPHERE

LIFE IN LOCATIONS OTHER THAN PLANETS OR LARGE MOONS? SMALL MOONS, ASTEROIDS, ETC. –NO ATMOSPHERE - THEREFORE NO LIQUIDS, EXTREME TEMPERATURE VARIATIONS, AND NO PROTECTION AGAINST ULTRAVIOLET RADIATION STARS –TOO HOT FOR COMPLEX MOLECULES TO FORM NEBULAE (CLOUDS IN THE INTERSTELLAR MEDIUM)‏ –LOW TEMPERATURE AND DENSITY  CHEMICAL REACTIONS PROCEED VERY SLOWLY  HARD TO IMAGINE COMPLEX MOLECULES FORMING NEUTRON STARS??

LIFE ELSEWHERE COULD HAVE: Very similar proteins and DNA sequences to us (if so, a common origin is likely)‏ Same amino acids and genetic bases as us, but combined into different proteins and DNA sequences (common origin?)‏ Amino acids and genetic bases, but not the same 20 amino acids and 4 or 5 bases as us Different monomers, (i.e., not amino acids and genetic bases), but still carbon-based polymers of some sort Different chemistry (silicon-based?)‏ No chemistry at all! (exotic matter, or interactions other than electromagnetic)‏

CHEMISTRY INVOLVES COMBINING ATOMS TO MAKE MOLECULES (INCLUDING MOLECULES BEING BROKEN APART INTO ATOMS, THEN ATOMS REARRANGING AND COMBINING INTO NEW MOLECULES)‏ BASIS OF ALL LIFE ON EARTH BASIS OF ALL CARBON-BASED LIFE BASIS OF SILICON-BASED LIFE (IF POSSIBLE)‏ HAPPENS BECAUSE OF ELECTROMAGNETIC FORCES

FUNDAMENTAL FORCES MANY FORCES ARE ELECTROMAGNETIC FORCES. –ELECTRICAL FORCES HOLD ATOMS TOGETHER (ATTRACTION BETWEEN POSITIVELY CHARGED NUCLEUS AND NEGATIVELY CHARGED ELECTRONS). –ELECTRICAL FORCES HOLD ATOMS TOGETHER TO FORM MOLECULES. (ELECTRONS ARE TRANSFERRED OR SHARED BETWEEN ATOMS.)‏ –“CONTACT” FORCES ARE ELECTRICAL WHEN EXAMINED ON A MICROSCOPIC LEVEL. –ELECTRICITY AND MAGNETISM ARE CLOSELY RELATED - MAGNETISM IS CAUSED BY MOVING ELECTRIC CHARGES. GRAVITY IS A FUNDAMENTALLY DIFFERENT KIND OF FORCE HOW MANY KINDS OF “FUNDAMENTAL” FORCES ARE THERE? WE THINK THERE ARE ONLY FOUR TYPES OF FUNDAMENTAL FORCES.

FUNDAMENTAL FORCES (IN ORDER FROM STRONGEST TO WEAKEST)‏ NAMERANGECOUPLES TO STRONGSHORT“COLOR” ELECTROMAGNETICLONGELECTRIC CHARGE WEAKSHORT“FLAVOR” GRAVITYLONGMASS NOTES: (1) “SHORT RANGE” MEANS THAT THE PARTICLES MUST BE WITHIN m ( m) OF EACH OTHER TO FEEL THE FORCE. “LONG RANGE” MEANS THAT THE PARTICLES WILL FEEL THE FORCE EVEN IF THEY ARE VERY FAR APART (ALTHOUGH THE FORCE MAY BE WEAKER IF THE PARTICLES ARE FARTHER APART). (2) “COUPLES TO” MEANS THAT THIS IS THE PROPERTY THE PARTICLES MUST HAVE IN ORDER TO FEEL THE FORCE OR EXERT THE FORCE ON OTHER PARTICLES.

FUNDAMENTAL FORCES (IN ORDER FROM STRONGEST TO WEAKEST)‏ NAMEEFFECTS STRONGHOLDS NUCLEI OF ATOMS TOGETHER, CAUSES CERTAIN TYPES OF REACTIONS BETWEEN PARTICLES ELECTROMAGNETICHOLDS ATOMS AND MOLECULES TOGETHER, CAUSES CERTAIN TYPES OF REACTIONS BETWEEN PARTICLES WEAKCAUSES BETA DECAY (TYPE OF RADIOACTIVE DECAY)) AND CERTAIN TYPES OF REACTIONS BETWEEN PARTICLES GRAVITYHOLDS PLANETS, STARS, AND GALAXIES TOGETHER

HOW ARE THE FUNDAMENTAL FORCES RELATED TO LIFE? ANY FORM OF LIFE THAT INVOLVES CHEMISTRY (ATOMS AND MOLECULES) IS BASED ON THE ELECTROMAGNETIC FORCE, BECAUSE THE ELECTROMAGNETIC FORCE IS RESPONSIBLE FOR HOLDING ATOMS AND MOLECULES TOGETHER. COULD LIFE BE BASED ON ONE OF THE OTHER FUNDAMENTAL FORCES INSTEAD? FOR THIS TO BE POSSIBLE, ONE OF THE OTHER FORCES WOULD HAVE TO BE ABLE TO HOLD TOGETHER MATTER IN SOME SORT OF COMPLEX (LOW ENTROPY) ARRANGEMENT. IF SO, LIFE WOULD BE VERY DIFFERENT FROM TERRESTRIAL LIFE.

HOW ARE THE FUNDAMENTAL FORCES RELATED TO LIFE? COULD LIFE BE BASED ON ONE OF THE OTHER FUNDAMENTAL FORCES (NOT ELECTROMAGNETIC)? –PROBABLY NOT THE WEAK FORCE, BECAUSE IT DOESN’T HOLD ANYTHING TOGETHER. –PROBABLY NOT THE GRAVITATIONAL FORCE BECAUSE IT IS SO WEAK THAT IT CAN ONLY HOLD TOGETHER VERY LARGE OBJECTS LIKE PLANETS AND STARS. THESE OBJECTS AREN'T PARTICULARLY COMPLEX OR ORGANIZED. (THEY DON'T HAVE A PARTICULARLY LOW ENTROPY.) FOR INTERACTIONS BETWEEN SMALLER AMOUNTS OF MATTER, GRAVITY IS SO WEAK THAT WE CAN IGNORE IT. –HOW ABOUT THE STRONG FORCE?

STRONG INTERACTION LIFE? STRONG INTERACTIONS HOLDS PROTONS AND NEUTRONS TOGETHER IN ATOMIC NUCLEI ORDINARY NUCLEI AREN’T VERY COMPLEX OR ORDERED, BUT… NEUTRONS CAN FORM COMPLEX ARRANGEMENTS (HELD TOGETHER BY STRONG FORCE) ON THE SURFACE OF A NEUTRON STAR. COULD THESE BE COMPLEX ENOUGH TO BE CONSIDERED LIFE?? WE DON’T KNOW, BUT IF SO, –SIZE ~ CM –STRONG INTERACTIONS OCCUR VERY QUICKLY (VERY SHORT TIMESCALES) – THEREFORE LIFETIME OF INDIVIDUAL ORGANISM IS ~ SEC –COMMUNICATION VIA GAMMA RAYS? –HIGHLY RECOMMENDED SCIENCE FICTION: “THE DRAGON’S EGG” BY ROBERT FORWARD

SEARCHING FOR LIFE IN OTHER SOLAR SYSTEMS WE WILL TAKE A CONSERVATIVE APPROACH. WE WILL CONSIDER ONLY LIFE THAT IS BASED ON THE ELECTROMAGNETIC INTERACTION, i.e., ATOMS AND MOLECULES. FURTHERMORE, WE WILL ONLY CONSIDER LIFE THAT USES CARBON-BASED CHEMISTRY AND USES WATER AS ITS LIQUID SOLVENT. IGNORE POSSIBILITY OF “EXOTIC LIFE,” SUCH AS LIFE THAT USES A LIQUID SOLVENT OTHER THAN WATER, SILICON-BASED LIFE, OR LIFE BASED ON THE STRONG FORCE. THEREFORE CONSIDER ONLY “EARTH-LIKE” PLANETS (OR LARGE MOONS) WITH LIQUID WATER.

SEARCHING FOR LIFE IN OTHER SOLAR SYSTEMS WE WILL BE MAKING ESTIMATES OF HOW COMMON OR RARE LIFE MIGHT BE. IF EXOTIC LIFE CAN EXIST, THEN LIFE MAY EXIST IN A LARGER RANGE OF LOCATIONS AND BE MORE COMMON THAN WHAT WE WILL ESTIMATE.