Physics: Life, Diversity and the Stars

Connections Through Time,   Issue 5: October - December 1999

Life exists almost everywhere on/near the surface of our planet.   Life is not easy to define exactly - plants and animals have it, the mineral world does not.   Basically, an entity is alive if it has a reproductive system and an active metabolism (i.e., is biochemically active as characterized by ingestion of nutrients, the storage and use of energy, and the excretion of wastes).  

About 3.5 billion years ago life existed on earth - a photosynthetic bacteria that lives in the water, called cyanobacteria has been found in "fossilized colonies" that old.   The picture at the left is a short chain of fossilized cyanobacterial cells, from the Bitter Springs Chert of northern Australia (about 1 billion years old).   Cyanobacteria still exist today and are an important group of bacteria.   The large amount of oxygen in our atmosphere was first generated from the growth of many many cyanobacteria.   These cyanobacteria were also involved in the origin of plants - yes plants.   Here is a quote from a page in the online exhibit of the UC Berkeley Museum of Paleontology:
The chloroplast with which plants make food for themselves is actually a cyanobacterium living within the plant's cells. ... Because they are photosynthetic and aquatic, cyanobacteria are often called 'blue-green algae'. This name is convenient for talking about organisms in the water that make their own food, but does not reflect any relationship between the cyanobacteria and other organisms called algae.   Cyanobacteria are relatives of the bacteria

Surprisingly, scientists have a better understanding of how many stars there are in the galaxy than how many species there are on Earth.   Estimates of global species diversity have varied from 2 million to 100 million species, with a best estimate of somewhere near 10 million, and only 1.4 million have actually been named.

We may have provided more details above than you want, however, the point is that life developed, diversified and flourished in an awesome fashion.   One mostly non-technical book, with great graphics and descriptions, that delves into the details concerning the development, diversity, robustness, and interactivity of life with non-life is "A Walk Through Time : From Stardust to Us : The Evolution of Life on Earth".  Here are extended quotes from this highly recommended book concerning how we are indeed made of stardust:

The universe has a bias for complexity. The universe began as elementary particles, then began constellation into galactic structures. The creativity of the universe accomplishes all this through its own intrinsic self-assembling or self-organizing dynamics. ... After 500 million years a new threshold of organization was reached, and the amorphous clouds of hydrogen and helium began to assemble themselves into elliptical and spiral galaxies, one of which will eventually be called the Milky Way Galaxy, our home.

...when we come to a system as complex as a star, we find a complexity so vulnerable to destruction that it is only with a constant supply of energy that it is able to maintain its structure. ... The food of hydrogen is transformed by nuclear fusion into the waste of helium, and in the process the star gets the energy it needs ...When it uses up the plentiful hydrogen, the star compresses itself and heats up further and begins consuming its helium and in the process creates carbon. If even this helium is used up, the star responds by collapsing down further and heating up until it can consume carbon in its quest to hold off gravitational collapse and survive yet another day.

If the star is of a privileged size, it continues to consume its elements, and then to consume the elements it has constructed, all the way up to iron itself. ... No longer obstructed by the radiant energies of the stellar nuclear fusion, the star's matter rushes madly toward its common center of attraction and creates a concentration of heat unlike any moment since the very birth of the universe, a concentration into a single supremely dense point that then blasts apart in every direction in a display of energy that is among the most spectacular in the entire universe. Its end is sheer brilliance, an intensity matching 100 billion stars. And this explosion of the supernova is an end that is, surprisingly, not really an end.

The first supernova explosion utterly destroys the star itself, but in the destruction all the remaining elements of the universe are synthesized for the first time. ... Before the first supernova explosion there is no carbon, no nitrogen, no oxygen, no phosphorus, no sulfur anywhere in the galaxy. suddenly enriched with these cosmic treasures, the Milky Way is able to bring forth entirely new stellar systems. Five billion years ago our galaxy ignites yet another cloud ... As this cloud collapses and evokes its fusion reactions and becomes our Sun, a remnant of the cloud continues spinning around the new star. This remnant breaks into ten bands of matter that cool and accrete into Mercury, Venus, Earth, Mars, the asteroids, Jupiter, Saturn, Uranus, Neptune and Pluto. The supernova that reached its end has now become a new beginning--a planetary system composed of all the elements and their dazzling possibilities. Rising up into existence, the Sun and Earth together are poised to give birth to a new kind of beauty, one that grows out of all the universe has given birth to thus far.

So, our physical bodies are truly made of stardust.   An example of a supernova explosion is visible to us today in the Crab Nebula, located about 6,000 light-years from Earth in the constellation Taurus.   Below is the view using X-rays; click on the photo to see how this looks in normal (optical) light as well when using infrared and radio waves.

The Crab Nebula, the spectacular remains of a cosmic explosion nearly a thousand years ago, revealed a new feature in images released Sept 28, 1999: a glowing ring of X-rays around its heart. The fresh images were captured by the Chandra orbiting observatory, launched two months earlier to observe the X-rays emitted by various heavenly bodies. The Crab's ring may help astronomers understand what keeps the nebula glowing. (NASA via Reuters)

Life is indeed connected to the stars and the big bang and all that is.