Question on the Moon Creation Theory

[Cugel]

Gentlemen,

I have the following question, for which I couldn't find an answer on the internet sofar.

According to main-stream theory the Moon came into being after a Mars-sized proto-planet struck the Earth. Now, before this event the orbit of our planet was very likely an ellipse with very small eccentricity. (Almost circular). Nowadays the orbit is also almost circular. My conlcusion is (correct or not?) that the Moon creation event didn't change the orbit of the Earth very much. Hardly at all, I would say. How can this be?

I mean, a collision with a mass the size of Mars surely would have changed the orbit of Earth into an ellipse with much bigger eccentricity. At least the theory claiming to describe this event should somehow explain why the orbit of Earth did NOT change. Maybe it does explain this and I am missing something here?

[AstroSmurf]

My conlcusion is (correct or not?) that the Moon creation event didn't change the orbit of the Earth very much. Hardly at all, I would say. How can this be?

A collision could change the eccentricity in any direction, depending on the exact parameters. For example, an impact from "ahead" at perihelion, or from "behind" at aphelion would reduce eccentricity, while the reverse would increase it.

The velocities involved also deserve some thought. I have no figures to base my analysis on, but since the Earth wasn't shattered all over the place, but instead merged with the impactor, I'd say the velocities involved weren't all that large. The most likely scenario is that Earth and the other planet had very similar orbits, so they more or less bumped into each other just enough to create the moon-creating event. More of a nudge than a big wallop, at least as far as the orbit is concerned.

[Zero Signal]

I decided to try out this type of collision at the Earth Impact Effects Program (I love this program). I used an impactor slightly larger in diameter (8000 km) than Mars. Assuming it follows the standard mass-radius relationship as the other inner planets (excluding Mercury but including Earth's moon), it should have a density of about 4.25 g/cm**³. This yields a mass of about 1.14 x 10^24 kg, or about 1.775 times the mass of Mars. This is within the parameters of the size that Theia (aka Orpheus or the Giant Impactor) is thought to have been (1 to 3 Mars masses). Most sources state that Theia impacted at a speed of 20 km/s. It impacted at an oblique angle, which for the sake of arguement I will place at a shallow 15°.

Plugging in these parameter in the EIEP calculator gave me the following results:

Your Inputs:

Distance from Impact: 20000.00 km = 12420.00 miles
Projectile Diameter: 8000000.00 m = 26240000.00 ft = 4968.00 miles
Projectile Density: 4250 kg/m^3
Impact Velocity: 20.00 km/s = 12.42 miles/s
Impact Angle: 15 degrees
Target Density: 2500 kg/m^3
Target Type: Sedimentary Rock


Energy:

Energy before atmospheric entry: 2.28 x 10^32 Joules = 5.44 x 10^16 MegaTons TNT
The average interval between impacts of this size is longer than the Earth's age.
Such impacts could only occur during the accumulation of the Earth, between 4.5 and 4 billion years ago.


Major Global Changes:

The Earth is strongly disturbed by the impact, but loses little mass.
47.72 percent of the Earth is melted
The impact makes a noticeable change in the Earth's rotation period and tilt of its axis.
The impact does not shift the Earth's orbit noticeably.


Crater Dimensions:

Transient Crater Diameter: 10100 km = 6280 miles
Transient Crater Depth: 3580 km = 2220 miles

Final Crater Diameter: 33700 km = 20900 miles
Final Crater Depth: 6.83 km = 4.24 miles
The final crater is replaced by a large, circular melt province.
At this impact velocity ( < 12 km/s), little shock melting of the target occurs.
Melt volume = 3.88 times the crater volume
At this size, the crater forms in its own melt pool.


Thermal Radiation:

Time for maximum radiation: 6110 seconds after impact

Your position is inside the fireball.
The fireball appears 1240 times larger than the sun
Thermal Exposure: 2.36 x 10^13 Joules/m2
Duration of Irradiation: 159000 seconds
Radiant flux (relative to the sun): 149000


Effects of Thermal Radiation:


Clothing ignites

Much of the body suffers third degree burns

Newspaper ignites

Plywood flames

Deciduous trees ignite

Grass ignites



Seismic Effects:

The major seismic shaking will arrive at approximately 4000 seconds.
Richter Scale Magnitude: 15.8 (This is greater than any earthquake in recorded history)
Mercalli Scale Intensity at a distance of 20000 km:

X. Most masonry and frame structures destroyed with their foundations. Some well-built wooden structures and bridges destroyed. Serious damage to dams, dikes, embankments. Large landslides. Water thrown on banks of canals, rivers, lakes, etc. Sand and mud shifted horizontally on beaches and flat land. Rails bent slightly.

XI. As X. Rails bent greatly. Underground pipelines completely out of service.


Ejecta:

Your position is in the region which collapses into the final crater.


Air Blast:

The air blast will arrive at approximately 60600 seconds.
Peak Overpressure: 5.66e+08 Pa = 5660 bars = 80400 psi
Max wind velocity: 19200 m/s = 42800 mph
Sound Intensity: 175 dB (Dangerously Loud)
Damage Description:


Multistory wall-bearing buildings will collapse.

Wood frame buildings will almost completely collapse.

Multistory steel-framed office-type buildings will suffer extreme frame distortion, incipient collapse.

Highway truss bridges will collapse.

Highway girder bridges will collapse.

Glass windows will shatter.

Cars and trucks will be largely displaced and grossly distorted and will require rebuilding before use.

Up to 90 percent of trees blown down; remainder stripped of branches and leaves

Major global changes have been highlighted. According to the EIEP, Earth's orbit will not be affected significantly, but it will experience other major changes.

Hope this helps.

[Cugel]

Thanks! It seems that most of the kinetic energy of the impactor went into melting the Earth. And not in changing its orbit. That is if I correctly interpret the 'Earth Impact Effects Program' results.

[anonymousman]

You got a good point there, it is impossible for the moon creation theory to work. This goes also to these other big bang theories. Go to this site you will find some real scientific evidence how the moon was created redacted YEC URL

[pzkpfw]

You got a good point there, it is impossible for the moon creation theory to work. This goes also to these other big bang theories. Go to this site you will find some real scientific evidence how the moon was created redacted YEC URL

No, you do not present non-mainstream theories outside of the ATM (against the mainstream) sub-forum. Asking questions is one thing, pushing fringe theories is another.

[Van Rijn]

You got a good point there, it is impossible for the moon creation theory to work. This goes also to these other big bang theories.

A couple things puzzle me about this statement . . . I don't see anyone in this thread, other than you, claiming the "moon creation theory" (and by that, I'm guessing you mean the "giant impact hypothesis"?) is impossible/can't work, so I'm curious what "good point" you're referring to. Also, I don't see any mention of "big bang theory" (or "other big bang theories") in this thread before your post, so I'm having trouble understanding the relevance there. Still, if you're so inclined, I would be curious to see what argument you would make in the ATM forum about the "moon creation theory," assuming, of course, there were some level of mathematical rigor and careful research. After all, everyone understands that argument by hand-waving is pointless, right?

[Tog]

Also worth noting is the 6+ year gap between posts 4 and 5.

[Frog march]

I thought one of the theories was that a small planet formed in a Lagrange point near the Pre Earth object, and its orbit became unstable, and crashed into the pre Earth, so there would be no change in orbit if that were true, would there?