The Earth will end with fire, non-metaphorically. It will be consumed when the sun expands as it runs out of fuel, 5 billion years from now.
Category: Natural World
The History of the Moon
In the early solar system, 4.5 billion years ago, the planets were still coalescing, something enormous hit the Earth.
After it formed, huge impacts shaped the surface of the moon into what we see today. NASA takes up the story:
These videos are awesome introductions to the early history of the Earth, Moon, and solar system.
Why Feburary 29th?
CGP Grey explains why we need leap days to fill in the calender.
Jupiter and Venus in Conjuction
Jupiter and Venus have been sitting near the western horizon, shining so brightly that even I have noticed them. Phil Plait explains with some back-of-the-envelope math, why Venus is brighter even though it’s smaller than Jupiter. It’s a nice example of how a little math can do a great job explaining how the world (and others) works.
Daffodil Pollen Under the Microscope
For the record: Daffodil flowers have both male and female parts, which make them good subjects for dissection. And, it’s pretty easy to collect daffodil pollen samples to look at under the microscope. 1000 times magnification seems necessary to be able to make out structures.
Since prehistoric pollen, collected from places like the bottom of lakes, are one of the easiest ways of finding past climates, a study of more recent samples might make for a good student research project in biology or environmental science. They’d need to design the study so they could avoid having to use nasty acids (hydrochloric or hydrofluoric) to concentrate the pollen grains, but that should be possible. Perhaps an ongoing survey using pollen traps, akin to the European Pollen Monitoring Program.
The Geology of St. Albans, Missouri
The area around the Fulton School has just two types of geology: young, floodplain sediments; and old limestone bedrock.
- Missouri River Flood Plain Sediments:
- Bedrock. Mostly limestone:
Geologic History
The continents form
To reconstruct the geologic history, we can start a bit deeper, with the fact that we’re sitting in the middle of a continent, which means that if you drill deep enough you’ll get to some of the original, granitic rocks that formed just after the crust of the Earth cooled — about four and a half billion years ago.
The continental crust is a bit like the froth that forms on moving water (or the top of boiling jam), and just like froth it tends not to want to sink. So there’s some pretty old continental crust beneath the continents.
However, also just like froth on water, the continental crust is pushed around on the surface of the Earth. This is called continental drift (which is part of the theory of plate tectonics). Sometimes, the continental crust can split apart, making space for seas and oceans between the drifting continents, and causing parts of the continent to subside beneath the oceans.
At other times, such as when two continents collide, they can push each other up to mountains out of areas that were once seas.
And that’s how we ended up with limestone rocks in the middle of Missouri.
Forming Limestone Rocks (Ordovician)
Five hundred million years ago (500,000,000 years ago) the continents were in different places, and Missouri was under a shallow part of the Iapetus Ocean.
Many of the micro-organisms that lived in that ocean made shells out of calcium carbonate.
When you accumulate billions of these shells over the course of millions of years, and then bury them, compress them, and even heat them up a bit, you’ll end up with a rock made of calcium carbonate. We call that type of rock: limestone.
Emerging from the Oceans: The Formation of Pangea.
The Mississippian limestone rocks formed in the same way, but about 360 million years ago. Why is there a gap between the Ordovician rocks (450 million years ago) and the Mississippian ones? Good question. You should look it up (I haven’t). There may have been rocks formed between the two times but they may have been eroded away.
I can make a good guess as to why there are no limestone rocks younger than about 300 million years old, however. At that time the continents, which had been slowly sidling toward each other, finally collided to form a super-continent called Pangea.
What would become North America (called Laurentia), ran into the combined South America/Africa continent (called Gondwana) pushing up the region, and creating the Ozarks and Appalachian Mountains.
And that’s the story the geology can tell.
References
The USGS has good, detailed, interactive maps of the geology of the states in the US.
A nice geologic map of St. Louis County can be found here.
A geologic time scale from the USGS.
The Physics of Flight: World Bird Sanctuary in St. Louis
A discussion of the physics of flight, interspersed with birds of prey swooping just centimeters from the tops of your head, made for a captivating presentation on avian aerodynamics by the people at the World Bird Sanctuary that’s just west of St. Louis.
Lift
The presentation started with the forces involved in flight (thrust, lift, drag and gravity). In particular, they focused on lift, talking about the shape of the wings and how airfoils work: the air moves faster over the top of the wind, reducing the air pressure at the top, generating lift.
Then we had a demonstration of wings in flight.
We met a kestrel, one of the fastest birds, and one of the few birds of prey that can hover.
Next was a barn owl. They’re getting pretty rare in the mid-continent because we’re losing all the barns.
Interestingly, barn owls’ excellent night vision comes from very good optics of their eyes, but does not extend into the infrared wavelenghts.
Finally, we met a vulture, and learned: why they have no feathers on their heads (internal organs, like hearts and livers, are tasty); about their ability to projectile vomit (for defense); and their use of thermal convection for flying.
The Sanctuary does a great presentation, that really worth the visit.
Gravitational and Electric Fields
Astronaut Don Pettit makes water droplets orbit a knitting needle. Instead of gravity, the attractive force that holds the water droplets in orbit is generated by the static electric charge on the knitting needle and on the water droplet. This works because gravity and electromagnetic forces follow similar rules (inverse square laws).
See more of his space-based experiments on Science off the Sphere on Physics Central.