Dino's Demise

No, I’m not talking about Dean Martin. I’m referring to the extinction of dinosaurs and what we can infer from this event about our climate, past and present. As I have previously posted in this blog, Robert Rohde of the University of California at Berkeley offers the following chart of carbon dioxide levels in our atmosphere --

http://en.wikipedia.org/wiki/Image:Phanerozoic_Carbon_Dioxide.png

I believe that this seems a thoroughly researched attempt to track carbon dioxide levels in our atmosphere over the last 600 million years. In viewing this chart (you may want to print it out to better follow the following discussion), I got to thinking about how this might correspond to the waxing and waning of the Earth’s flora and fauna. So back to Google I went and came up with the following rough biota chronology which I would like here to relate to Rohde’s chart:

4.5 billion years ago -- The Earth was thought to be formed.

3.5-3.9 billion years ago -- First primitive life forms inhabited the Earth’s seas.

450 million years ago -- First land plants appeared on Earth. These plants, through their acquired ability to carry on photosynthesis, could absorb carbon dioxide and water and produce hydrocarbons and emit oxygen. Please note that the Rohde chart has carbon dioxide volume levels at this point at about 6,000 parts per million (about 0.6%)

230 million years ago (during the Triassic period) – Dinosaurs first appeared. Please note that the Rohde chart has carbon dioxide volume levels at this point at about 1,000 parts per million (about 0.1%). This says then that, over the previous 220 million years, plants, through photosynthesis, had seemingly reduced atmospheric carbon dioxide to one-sixth the level that it was when land plants first appeared. This can begin to explain the surfeit of hydrocarbons buried in the earth in form of oil, gas, coal, etc. The chart also shows a dip in carbon dioxide levels to a nadir of around 500 parts per million (0.05%) at around 320 million years ago which suggests to me that this is when the Earth’s salad bar was most plentiful. It was also during this period that Pangaea had started to separate itself into our present continents.

150 million years ago (Jurassic period) – Many species of dinosaur had already gone extinct and many others had taken their place. There were two primary types of dinosaurs: plant-eaters (rhoetosaurus, acrocanthosaurus, brachiosaurus, etc.) which were often gigantic (often weighing more than 80 tons) slow-moving creatures … and plant-eater eaters (often fast-moving raptors). Back at about 320 million years ago a plant-eating population probably began to appear (possibly including proto dinosaurs) which reduced the flora cover and allowed carbon dioxide levels to resurge and peak at around 2,500 parts per million (0.25%) during the Jurassic period.

70 million years ago (Cretaceous period) – Dinosaurs were thought to have gone extinct during this period. Note that carbon dioxide levels started to drop precipitously at about 100 million years ago to about 700 parts per million (0.07%) which suggests that plant life was resurging and plant-eaters diminishing most likely due to raptors holding sway. And as the plant-eating dinosaurs food supply of these raptors was reduced, the raptors began to go hungry (since they were unable to munch on plants.) Many scientists believe that it took almost 10 million years for this extinction event to occur. However, a stressed population of dinosaurs might have been dealt a coup de grace with an event like a comet strike or a massive caldera explosion. With these plant-eating machines of dinosaurs gone, plants once again had an open field and continued to reduce carbon dioxide.

5 million years ago – proto man first appeared on earth. Obviously man has, over the millennia, nurtured plants with his agriculture and exploited them for shelter and fuel. But carbon dioxide levels have not fluctuated that much during man’s sway on earth … not nearly to the magnitude as before he arrived. Obviously, because of drastically reduced carbon dioxide levels, our Earth seems to have become more susceptible to periodic ice ages (probably caused by other exogenous factors). These ice ages, in turn, have caused short-term increases in carbon dioxide levels as much of the world’s flora was buried under huge glaciers. These increases in carbon dioxide levels may have been the feedback that eventually raised the Earth’s temperature and melted much of the ice. Today carbon dioxide levels hover around 370 parts per million (0.037%) after possible recent lows of 310 parts per million (0.031%) about 40 years ago.

The Dark Side

Astrophysicists recently have been mapping the presence of “dark matter” in the universe. Dark matter had been postulated to exist because all the gravitational effects demonstrated in the universe cannot be explained by all the observable matter. Thus, it was concluded that there is matter, composed perhaps of exotic fundamental particles, that is invisibly affecting things. Scientists speculate that dark matter might comprise 2/3rds of the entire universe’s mass. This mapping of this dark matter has been recently accomplished by measuring, with the Hubble telescope, the gravitational deflection that dark matter is causing the light from distant galaxies (ala Einstein’s theory that gravity can bend light). This is called a “gravitational lens” and the amount of dark matter (with its gravity) is measured by the size of these deflections. The more dark matter in a particular section of the sky, the more bending has been observed to occur. Also this dark matter apparently can also be located three-dimensionally by how the various light wave lengths are affected – the redder the deflected light, the further away the dark matter is (ala the “red shift”). The interesting new result of this exhaustive work is that dark matter seems to be mainly co-located with visible matter.

Also “dark energy” has be scientifically surmised because, given all the universe’s matter and dark matter, its expansion should be slowing down. In fact, the edge of the universe is speeding up. Therefore, scientists feel there must be some unknown energy source that is pushing against all this gravity to cause this unexplained universe’s expansion acceleration. They are currently devising experiments to try to measure this dark energy and it location.

Now gravity is a force … and force is defined by “mass x acceleration”. Obviously gravity has more to it than just being a force and saying that gravity as we know it (canonic gravity) exists for dark matter (whose mass is undefined) is somewhat suspect. I would like to speculate there might be something called “virtual gravity”. That would be a form of gravity that exists without any discernable mass. This could exist if, during the Big Bang, gravity was created (gravitons?) along with other fundamental particles (matter), energy, etc. Quickly thereafter virtual gravity attached itself to matter (mass) and became canonic gravity … but there was still a surfeit of virtual gravity after the entire universe’s mass had been so sated. And since it seems relatively rare to create new matter out of energy, there still should exist a large excess of virtual gravity in the universe. (I have speculated in the past about how any new matter, when created, acquires gravity.) This extra virtual gravity could, in fact, be what we know as dark matter.

A more interesting speculation is that, since virtual gravity has no discernable mass, astrophysicists’ calculations requiring the existence of “dark energy” may well be greatly overstated. In fact, if one removes “mass” from the equation for virtual gravity’s force, one is left with only “acceleration” … which is exactly what the edge of the universe is supposedly doing.