Recent Scientific Developments

DEVELOPMENTS IN THE CORONAVIRUS

The emergence of the Delta Variant of the Coronavirus fits perfectly with what we saw last year in the posting, "The Natural History Of The Flu".

Natural selection dictates that, as variations in a contagious virus emerge, the favored variations will be those that are more contagious but, on a case by case basis, less deadly. Remember that, while it is in the interest of the virus to spread, it is not in it's interest to either kill it's hosts or make them so sick that they don't go out and spread the virus.

Here is a link to "The Natural History Of The Flu":

https://www.markmeeksideas.blogspot.com/2020/08/the-natural-history-of-flu.html?m=0

THE INTERNAL STRUCTURE OF MARS

With equipment landed on Mars attempts are being made to discern the internal structure of the planet by waiting for quakes, the same as was done on earth by analyzing the sound waves from earthquakes. But there is another way to accomplish this.

We can measure the volume of a planet and then it's mass by the gravitational effect that it has. But this only tells us the average density of the planet. All planets in our Solar System are composed of layers, with the core of the planet being of the most dense and the layers outside that successively less dense. Iron is plentiful in the inner Solar System and the four innermost planets, including earth, have prominent iron cores.

Remember my principle of "The Effective Center Of Gravity". We might think of a planet's center of mass and it's center of gravity as the same thing, but they aren't. The center of mass is constant but the center of gravity is relative, depending on the observer's position.

The force of gravity decreases with distance from the source according to the Inverse Square Law. At twice the distance the force of gravity would be one-quarter. A planet exerts gravity on it's surroundings but the planet is not an infinitesimal point, it has a certain diameter.

What this means is that the half of the planet that is closer to us has a greater gravitational effect on us than the half that is further from us. This means that the effective center of gravity of the planet is closer to us than the center of mass. The closer we are to the planet the more difference there is between the center of mass and the effective center of gravity. It is only when we are an infinite distance from the planet that the center of mass and the effective center of gravity become one and the same.

We know that there is energy in an orbit, such as in a satellite in orbit around the earth. The higher the orbit the higher the orbital energy, just as an object higher on a building would have more potential energy if it should fall. Like gravity orbital energy operates by the Inverse Square Law. If we give a moon or satellite three times the orbital energy it would go to an orbit at nine times the altitude but would then orbit at only one-third the velocity.

Because the satellite is a finite distance from the planet the focal point of it's orbit is actually the effective center of gravity of the planet, rather than it's center of mass. This doesn't seem to make a difference because the effective center of gravity is always on a line between the satellite and the center of mass, so that the effective center of gravity moves around the center of mass as the satellite orbits the planet.

The effective center of gravity of the planet, relative to the satellite, is furthest from the center of mass of the planet when the satellite is on the surface of the planet, before it is launched. As the satellite gains altitude the effective center of gravity moves closer to the center of mass, although it would only reach the center of mass when the satellite was an infinite distance from the planet.

This movement of the effective center of gravity within the planet makes the concept very useful for discerning the internal structure of the planet. If the planet was of uniform density throughout then a graph of altitude against orbital energy would form a straight line. But if there are layers of differing density within the planet then the plot of altitude against orbital energy would no longer form a straight line as the effective center of gravity crosses boundaries of differing densities as the satellite gains or loses altitude.

A planet will naturally have the more dense layers toward it's center. The earth has a heavy iron core, with a rocky mantle above that, and finally the lighter rock of the crust above that. As the satellite gains altitude, and it's effective center of gravity crosses a density layer boundary, the graph of altitude against orbital energy will slope upward. 

This is because the average density of the gravitational half of the planet will increase and thus a given altitude will encompass higher orbital energy. A "gravitational half" of the planet means that, at whatever altitude the satellite may be, the boundary between the two gravitational halves is such that the gravitational effect on the satellite by both gravitational halves will be equal.

The boundary between the two gravitational halves will, of course, pass through the effective center of gravity. The further gravitational half will naturally be heavier than the near gravitational half because distance from the satellite will increase the effect of the nearer half and decrease that of the further half. 

The boundary between the nearer and further gravitational halves is relative, and from the perspective of the satellite. The further from the planet the satellite is the closer it's gravitational halves will be in mass. At an infinite distance from the planet the satellite's two gravitational halves will be exactly equal.

This same principle of "The Effective Center Of Gravity" also explains something that has never otherwise been explained. This is the gaps in the rings of Saturn. Here is a link to that posting:

https://www.markmeeksideas.blogspot.com/2020/12/the-gaps-in-saturns-rings.html?m=0