MovieChat Forums > Impact (2009) Discussion > Biggest blunder?

Biggest blunder?

posted 15 years ago by TxMike
4 replies | jump to latest

To understand my following comment first you have to realize that the Moon doesn't actually revolve around the Earth. Both the Earth and the Moon revolve around the center of mass of the Earth/Moon couple, which happens to be inside the Earth's crust but not near its center.

In this movie, the Brown Dwarf fragment embedded inside the Moon makes it suddenly more massive than the Earth. If the Moon remains in an orbit after the collision, the Laws of Physics would dictate that both the Earth and the Moon would immediately begin to revolve around a new center of mass, this one much closer to the Moon than to the Earth. In essence the Earth would now be almost revolving around the Moon.

This isn't intended to be a harsh criticism of the movie, moreso because over the years our schools have "dumbed down" science and everyone should realize this. It is just a realistic way of looking at the world around us, to understand a bit of the Science and Physics involved.

However there may be an even bigger blunder. If a fast-moving object more massive than the Earth embeds itself in the Moon, I suspect it would not remain in any kind of semi-stable orbit.

TxMike
Make a choice, to take a chance, to make a difference.

[–] Bladerunner 15 years ago

This may have happened in time, but you are forgetting about another powerful aspect of physics - momentum. The Moon is moving at incredible speeds, rotating the earth at approximately 1 km/s (1 kilometer per second) which works out to be 2282 miles per hour. The speed of the orbit and the attraction of the Moon and Earth together means that it probably would do pretty much exactly what the movie showed. However, it's all theoretical. No one knows for sure what would happen.

As I touched on in the previous paragraph, are also forgetting about the pull between the Earth and the Moon. Their pull together would dictate that they would remain revolving around each other. In time, the relationship would shift as you say, the Earth would begin to orbit around the Moon. However, as stated in the movie, the closeness of the Earth and the Moon together is a more powerful force than it's attraction to the Sun. Because of the powerful pull, and the elipical orbit, they most probably would collide. After they collided, then they would (in time) move into a stable orbit around the Sun - that is if both weren't destroyed by the collision.

I don't think our schools have "dumbed down science", but then that probably depends on where you live. My sons are in advanced classes and are learning things and have standards that far exceed what I had in school, and I was in a private, college prep academy.

"...nothing is left of me, each time I see her..." - Catullus

[–] joebridge 14 years ago

Rotation is a body on its own axis. Revolution is a object going around another object.

From there, things are a little more complex. Science is our friend. This movie has none.

[–] a_heathen_conceivably 14 years ago

If there was a brown dwarf inside the moon (assuming we are to accept this) then surely the super dense almost-a-star must have pulled the moon around itself... and the earth would then orbit the moon if it's not drawn toward it? No-one ever poke fun out of "Space: 1999" ever again, OK (at least not the great first series)?

"Oh look - a lovely spider! And it's eating a butterfly!"
'' ,,

[–] michaelexarkun 13 years ago

However there may be an even bigger blunder. If a fast-moving object more massive than the Earth embeds itself in the Moon, I suspect it would not remain in any kind of semi-stable orbit.

By performing basic kinetic energy calculations of an asteroid twice as massive as the Earth and assuming a velocity equal to that of Halley's Comet, the energy imparted to the Moon would be:

K.E= 2.88 x 10E34 Joules.
For comparison, the 87 warheads that the military detonated into the moon released only:
Energy = 7.2 x 10E18 Joules. Thus the energy imparted to the moon fron the brown dwarf fragment was: 4 x10E15 greater.

Or, 4000 trillion times greater. A little more energy than the Sun releases in a year.

Even assuming a smaller velocity of the fragment ( assume 1/4 the velocity of Halley's Comet) the Kinetic energy is still 250 trillion times greater than the 87 warheads, or 20 trillion times greater than the 1100 20 megaton warheads the scientists were planning on detonating near the Moon on it's farthest axis point moving away from the Earth.

Needless to say, the Moon would have been obliterated, sending debris flying into the Earth with enough force and energy to sterilize Earth, at the very least.