Stuff Is Spinning Everywhere

Shooting stars physics

There are many forces at work in our world and outside of it. Although we do not always realize it, we are constantly moving through space and in contact with numerous other objects and forces at any given moment. First and foremost is Earth’s own position.

When the solar system was first formed, Earth came together from smaller debris that were all caught in the same channel of gravity to the sun. They had been orbiting the sun in the same path, and eventually coagulated with each other to form a large sphere. The force of their orbits, when combined, caused the Earth to spin constantly, rotating on its axis. Scientists theorize that eventually a collision with another large mass threw Earth on its 23 degree tilt as well as speeding up its rotation on said axis.

If you think of something spinning or rolling, you don’t imagine it going on forever. That is because on Earth, there are other forces to counter such motion. Here, we have air resistance and friction. However, up in space there is neither. Force is required to stop force, and there is no force out in space such as those on Earth that could be expected to come and inhibit our rotation. Earth will keep spinning until something large comes our way, since we lack another surface to bump into that will slow us. Not everything on Earth is moving exactly the same, though.

The centrifugal force of individual objects on Earth keeps everything from going completely smoothly. While the Earth is spinning around its axis, the oceans are slightly resistant because they are enacting centrifugal force. They are trying to move in a straight line, and they are large enough to noticeably move before they follow along Earth’s path of rotation. Another force that helps the oceans move away from the primary direction of rotation is the force from the moon. The moon’s gravity pulls them away ever so slightly on the side of the Earth that is closer to it. On the opposite side, its force is not enough to affect the oceans, so there is a push and pull of two high tides and two resulting low tides in the middle.

Now, what is going on around us in space? Well, we have the forces of other planets pulling on us, which affects our orbits. That is how Neptune was discovered; they had found Uranus but simply could not explain why its orbit was so off their predictions. Other objects in space, such as asteroids, meteors, and meteorites, have an impact on Earth.

Meteors that have hit/will hit Earth, and why we don’t worry about all of them:

Some meteors are vaporized in the atmosphere because their surface area is enough that it will come into contact with too many air molecules to burn up the mass of the meteor.

Some are too small for this to happen, but too small to impact us.

Some Equation Stuff:

Delta x- distance

Earth’s atmosphere extends about 16 km from the surface, or 16000m

Vi

Between 11km/s and 72 km/s → solve for it

Vf

The one that struck Arizona was going about 12 km/s^-1 upon impact, so 12000m/s^-1 which is 12000 x 60 = 720000 m/s

Acceleration

Earth’s gravity, roughly 9.8 m/s^2

In this equation, air resistance is also key.

F = force due to air resistance, or drag (N)

k = a constant that collects the effects of density, drag, and area (kg/m)

v = the velocity of the moving object (m/s)

ρ = the density of the air the object moves through (kg/m3)

CD = the drag coefficient, includes hard-to-measure effects (unitless)

A = the area of the object the air presses on (m2)

Using these factors, you could find how fast the object was going when it entered Earth’s atmosphere.

720000^2 = Vi^2 + 2 x 9.8 x 16000

Sq root of 5.18 x 10^11

Comes to 720000 m/s

Then apply air resistance

What can’t be accounted for in this equation is the “crushing point” of asteroids- the altitude at which they explode and their smaller fragments go down and hit Earth.

Another way to look at meteors is when they come into Earth’s orbit.

If the asteroid was going 25km/s, with a radius of about 200m, its centripetal acceleration would be

25000^2 / 200 = 3.125 10^3 m/s^2

*The units necessary to apply the equations have forced the given units to be converted

Sources:

Melosh, H. J., and G. S. Collins. "Planetary science: Meteor Crater formed by low-velocity impact." Nature, vol. 434, no. 7030, 2005, p. 157. Science in Context, link.galegroup.com/apps/doc/A185471700/SCIC?u=prov94491&xid=8b67ef74. Accessed 26 Oct. 2017.

Nelson, M. Rae. "Rotation and Orbits." Experiment Central: Understanding Scientific Principles Through Projects, edited by Kristine Krapp, 2nd ed., UXL, 2010. Science in Context, link.galegroup.com/apps/doc/CV2644200069/SCIC?u=prov94491&xid=0d9580c8. Accessed 26 Oct. 2017.

https://www.wired.com/2013/02/why-does-a-meteor-explode-in-the-air/