Almost 15 billion years ago - in an explosion like no other - the Universe was created. Within three minutes of the Big Bang, all the Hydrogen and almost all the Helium that we observe today were produced. The Universe, for the most part, was homogeneous and isotropic. Yet, some minute fluctuations, recently detected by the COBE satellite, became seeds for galaxy formation. Around these "galactic seeds" matter started to clump; first slowly and then faster and faster, because of their large gravitational attraction. In this way the first generation of stars and galaxies were born 1 billion years after the Big Bang. Some of these first-generation stars were so massive that they lived for only one million years. Yet, these were incredibly-efficient  nuclear furnaces - arranging protons and neutrons in new partnerships that resulted in heavier elements, such as Carbon, Nitrogen, Oxygen, and many others. Moreover, these massive stars did not die quietly. Rather, they died in spectacular supernova explosions that scattered all the heavy elements into space. These new elements got incorporated into the interstellar medium, leading to new galaxies and stars. Within three billion years of the Big Bang, a galaxy forms in a part of the Universe like many others. This newly-formed spiral galaxy, containing 100 billion of stars and extending for about 100,000 light years, is our galaxy: The Milky Way. Suddenly, in one of the spiral arms of the galaxy, a star, not too large not too small, with a mass of 2x10³⁰ kilograms is born. After some time, our Sun, becomes hot enough to fuse hydrogen and blows away most of the gas and dust cocoon. Nine planets are born. One of  them - our planet Earth - starts to revolve around the Sun in an orbit that is neither to far nor too close, but just right. Right and ripe enough for the formation of LIFE.

Stars must die ... So we can live
So we are back were we started at the beginning of the semester: taking a cosmic journey. Now, however, we are all wiser and know that the journey should have started with the last, rather than with the first, frame.

1802 -- William Paley  published a forcefully argued treatise entitled: "Natural Theology or Evidences of the Existence and Attributes of the Deity Collected from the Appearances of  Nature". This is perhaps the best-known work that uses the 'Argument from Design' thesis to argue for the existence of a creator. The Design Argument suggest that living systems are so well-adapted to their purpose, and so incredibly complex, that they couldn't have arisen by chance. Rather, they appear to have been designed by a: Supreme Designer.

For example, take the molecule of hemoglobin (the blood transporter of Oxygen) which consists of 4 chains of amino acids twisted together. Each chain contains 146 amino acids. Life on Earth is based on 20 different kinds of amino acid. Therefore, the number of different ways of making a chain of 146 amino acids from 20 different building blocks is 20 multiplied by itself 146 times, since at each position in the chain one can place any one of 20 amino acids. That number is 20¹⁴⁶or about 10¹⁹⁰ ! Now suppose that you take the fastest ever built Teraflop (trillion operations per second) computer and start constructing combinations at random for as long as the Universe has existed, which is 10¹⁸ seconds. This will let you construct only 10³⁰ combinations. Chance alone cannot lead to LIFE. Thus, the argument in favor of a Supreme Designer (or Creator) seems utterly compelling. Indeed, for more than fifty years Paley's argument was never questioned. Shortly after that, however, a purely natural way to achieve adapted complexity was discovered.

1859 -- Charles Darwin published The Origin of Species. This is arguably the most revolutionary work in the history of science. Darwin's basic idea is very simple. So simple, in fact, that it is frequently misunderstood. He recognized a purely natural way to obtain highly adapted complex organisms through:

Complexity - which can arise as a result of the cumulative effect of small random mutations;

Adaptation - as the result of a selection effect. Namely, if the mutations confer advantage to the chance of an organism to survive, the mutation will be adopted and will be passed on to the next generation. If, however, a mutation reduces the chance of survival, then that mutation is less likely to be passed on to the next generation because the organism may perish before it reproduces. Thus, over many generations the survivors will obviously be those organisms that are best able to adapt and survive. This selection effect is called Natural Selection.

It is important to understand that,  unlike evolution by artificial selection, evolution by natural selection, is undirected and goal-free. There is no aim: what survives is what works best at the moment on that environment. If evolution by natural selection has, indeed, occurred on Earth, then can it occur elsewhere.

Carbon-based Life forms:
The basic building blocks of Carbon-based life as we know it are organic molecules. Such molecules are spread throughout the Universe. An immediate question is: how easy is it to go from these simple organic molecules to the building blocks of life? This question was answered in a classic experiment performed in 1952 by the American chemists Stanley Miller and Harold Urey. They showed that simple molecules can combine to form the molecular building blocks of carbon-based life forms under conditions that are believed to have existed on the Earth in its early history.

A diagram of the Miller-Urey Experiment, where simple compounds are shocked to produce four amino acids, fatty acids, and urea.

Of course, this success is only the first step towards life forms. Somehow we have to get from the amino acids to self-replicating molecules. This is where natural selection proves crucial: although the chance of producing the right combination of amino acids to create a viable replicating molecule is essentially zero, it is possible, through natural selection, to get to such a molecule by the cumulative effect of small random changes in a large pool of randomly created molecules. Over time, the population of the more stable, better adapted, molecules would grow at the expense of less stable, less well adapted molecules.

The Best Candidate to Date: ALH 84001
Meteorite ALH 84001 (for Allan Hills) was found on the Antarctic ice in 1984 and only recently recognized as one of 12 meteorites believed to have come from Mars. How do we know it is from Mars? Because we are very lucky! ALH 84001 contains gases trapped in small glassy "bubbles". A careful analysis of these gases revealed that they have the same composition and abundance as the gases in the Martian atmosphere measured by the two Viking explorers that landed in 1976. The chemical abundances are like fingerprints and they match exactly. It now seems likely that ALH 84001 was blasted off the surface of Mars when a comet or asteroid struck the planet (and killed all the martian dinosaurs, just kidding!) Chemical, mineral, and fossil evidence suggest that ALH 84001 once contained LIFE. Traces of amino acids were found in the meteorite which supports the idea that the building blocks for life  are common in the Universe.  It doesn't prove, however, that there was past life on Mars; it doesn't prove that there was not either.

Allan H. Treiman, Lunar and Planetary Institute
August 21, 1996

Astronomer Frank Drake launched in 1960 the first modern search for alien radio signals. Using the radio telescope at the Radio Astronomy Observatory in West Virginia, Drake analyzed the signal coming from two stars - Tau Ceti and Epsilon Eridani - for beacons at 21 cm. His effort - called Project Ozma, marked the birth of a new scientific field: The Search for ExtraTerrestrial Intelligence. Since then many people have been scanning the Universe for signs of intelligent life, so far without success. However, the recent discovery of extrasolar planets enhances the probability that we are not alone, because if solar systems are commonplace then it is more probable that a planet like the Earth can exist elsewhere. However, we should not expect the species on these other worlds, if they exist, to be necessarily C-based life forms like those on Earth. Let's use the Drake equation to compute the probability of ETI.

Flying Toasters vs SETI:
We all can join together in the quest for SETI. SETI research consists primarily of radio astronomers searching for narrow-bandwidth radio signals (radio waves are able to penetrate interstellar medium). SETI@home is a scientific experiment that will harness the power of hundreds of thousands of Internet-connected computer. You can participate by running a program that downloads and analyzes radio telescope data. There's a small but captivating possibility that your computer will detect the faint murmur of a civilization beyond Earth. To participate in SETI@HOME, you'll need a computer with at least 32 MB of RAM, 10 MB of disk space, and an Internet connection (dialup is OK). There are plans to support Win95, Win98, WinNT, Mac, and many versions of UNIX, including Linux on various CPUs. It doesn't matter where in the world you live. For more information read the article in the April 1999 issue of Discover Magazine.

 

The Arecibo Message:
This message was sent on November 16, 1974 from the Arecibo Observatory in Puerto Rico, consisted of 1,679 bits of information, which is only divisible by two prime numbers - 73 and 23 - which suggests laying out the message in those dimensions, revealing this image. The picture shows our chemical makeup, our population, our height, our planetary system, and the telescope transmitting the message. The message was aimed at the M13 globular cluster; it will reach its destination in about 25,000 years.

SO, ARE WE ALONE? WE DON'T KNOW THE ANSWER TO THAT QUESTION YET. BUT IF IT IS ONLY JUST US .... IT SEEMS LIKE AN AWFUL WASTE OF SPACE.
 

 

 

Let's go and see the Stars
The Milky Way or even Mars
Where it could just be ours
Let's fade into the Sun
Let your spirit fly