Dinosaurs, units

When I was young dinosaurs hardly figured in history or in  my imagination. Things have changed so much that children seem fascinated by them. In the past 20-30 years there has been a plethora of dinosaur themed film and TV. The first Jurassic Park film and a TV series devoted to them not to mention other film and TV works. The original Jurassic Park film, by far the best in my opinion, was based on the idea that dinosaur DNA was preserved and used to recreate some dinosaur species who lived within a giant park on an island. Although plenty of hokum in a dino chasing humans plot the scenes of these pre historic creatures roaming around were truly breath-taking.

It isn’t only in popular media that dinosaurs have become important but many , many species have now been identified by science. These identifications are based on fossil remains.  A minute proportion have died in suitable conditions that their bones have become turned into stone. An even smaller number have had other tissue similarly preserved. Of some 1500 dinosaur species thought to have existed nearly a 1000 have been identified. It must be emphasised that we are looking a tiny percentage fossilised of whom only a small proportion have been found.

It appears that dinosaurs emerged after a great mass extinction about 250 million years ago. They emerged then because their predators, crocodile type creatures were nearly wiped out.  They then evolved through the Triassic and Jurassic ages until 66 million years ago. At that time an asteroid struck the earth in modern day Mexico. This was so massive that the blast, dust and climate change wiped out almost all life but some small feathered dinosaurs survived and evolved into birds we see today. Generically large meat eating birds are called raptors.

While all the publicity has been about gigantic animals such as brontosaurus, triceratops and tyrannosaurus rex in fact there were many types of dinosaur; many small and medium sized. Some were definitely feathered and some are thought to be flying species. They were an egg laying species so not unlike some modern reptiles. All of the ground dwelling types are thought to be wiped out in the asteroid impact.

Much about dinosaurs is still controversial. We guess they were scaly but maybe they were feathered. Generally soft tissue is not  fossilised and it only fairly recently that feathers have been on some species.

DNA is not preserved in fossils. The original premise of Jurassic park is that some is preserved in an insect itself trapped in amber. It may be possible to recreate some much more modern animals that have disappeared only recently. An example is the woolly mammoth . Samples have been found trapped in ice about 10,000 years old. It may be possible to extract viable DNA from these corpses and scientists are trying to do just that. It would be necessary for a modern day elephant to carry any potential mammoth to birth. There has been some effort to reconstruct a dinosaur like DNA from modern animals

In principle all cells carry the full DNA coding of the animal. DNA, which is a gigantic molecule, will undoubtedly have been broken up but reconstituting DNA from small parts is a known technology.

I’ve been slightly puzzled by the interest shown by small children. Part of the attraction is the truly gigantic scale of some dinosaurs. Sauropods could be 130 feet long and 60 feet high ( roughly 40x20m ) As mentioned above while these are more readily found as large fossils are more readily discovered some dinosaurs were small down to 18 inches ( 0.5m ) in length. The typical body type has big rear legs and small front ones while most seem to had frills, horns or spikes. They were not necessarily meat eaters

Units

I don’t whether to laugh or cry on the news that new minister Jacob Rees-Mogg has ordered his civil servants to use imperial units. Unconsciously it gives away his fierce Brexit stance. It is not motivated by thoughts of a new economic future but rather nostalgia for a lost era.

Yes the metric system was a product of the French revolution but it is now almost universal. That needs some qualification. Only American engineers still decreasingly use non metric units. When I was a schoolboy I was taught in a strange hotch-potch. It was common in science then to use the cgs system ( Centimetre-gram-second ) or its close cousin the mks system ( metre-kilogram- second ). There were peculiar units such as dyne for force and angstrom for small distances.. Essentially you had to remember what these were.

In the late 60’s a more coherent SI ( systeme international) ( yes in French , Jacob ) was introduced into science and is now universal.  When I became a research student my supervisor insisted I use SI units. I am grateful even though it was a slightly painful transition. For example surface tension, with which I was much concerned, became millijoules per square metre rather than the rather bizarre dynes per centimetre I had used until then. In this case the transition was easy because the numerical value is the same. One slight difficulty is that units can be very small, thus a joule is a very small unit of energy so kJ and MJ fit more commercial purposes.

SI introduced new units all based on the names of famous scientists. Thus the new unit of force was the Newton with all the usual centi, milli etc prefixes.  Over the past years we have become used to temperatures in degrees Celcious( this is centigrade renamed, numbers stay the same ). Again America is the holdout still using Fahrenheit along with some Caribbean counties. It is surprising that while many imperial units are in common use today they often have SI underpinnings thus the pound is 454 grams, and a 3x2 wood section is really 75x50mm. It is surprising how the units we are used to as children stay with us for life. Nearly 50 years after decimalisation when I picked up a fallen 5p coin I exclaimed there is sixpence. This isn’t even a correct conversion as the 2.5p coin disappeared years ago.