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Qingu's avatar

Could we knock Earth out of its own orbit?

Asked by Qingu (21160points) October 17th, 2010

Is it physically possible to use current technology to knock Earth out of its own orbit?

I guess another way of phrasing this is: is there enough kinetic energy stored in Earth’s capacity for thermonuclear weapons to actually disrupt Earth’s orbit enough to change it? (I imagine, in principle, this wouldn’t be different than how satellites correct their orbits with rocket fire.)

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14 Answers

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Blondesjon's avatar

I don’t think so. I imagine there have been volcanic eruptions in our geological history that would make all of the world’s nuclear arsenal seem like a pop gun. So far as I know, none of these have shaken us from our course.

Plucky's avatar

I think it’s possible ..anything is really. The earth will not last forever.

If we could knock our planet out of orbit, I wonder what would happen if it was sudden. Would we all just die instantly ..or would it take awhile ..what kinds of things would we experience?

I remember looking into this years ago ..and of course I can’t remember anything from my personal search other than seeing the earth fall through a graph

earthduzt's avatar

@PluckyDog well depending on which way we were headed we would either experience a big freeze (heading away from the Sun) or deep fry (heading into the Sun). It would not be instant at all, it would take a couple thousand years for this to happen if we got knocked out of orbit…but I guess in Universe time that is pretty instant.

Vortico's avatar

In a closed system, the center of gravity is held in a fixed position. In order to “disrupt” the usual orbit path, we must throw something with a large mass off the earth at a high velocity.

For example, the Saturn V rocket was roughly 3.0e6 kg and left the earth’s atmosphere at a velocity close to 7,000 m/s. By the momentum definition, the change of Earth’s velocity is V = m v / M, where V is velocity and M is mass. Capital letters represent Earth while lowercase letters represent the rocket. Since the earth’s mass is 5.97e24 kg, it can be calculated that the launch of Saturn V caused the earth to move at 3.5e-15 m/s (7.9e-15 mph) in the opposite direction.

The law of conservation of momentum can lead to an interesting theorem. If an object is propelled away from Earth somehow and later returns, the Earth will return to exactly the same point as it was before the object left. Thus, if everyone in Europe gathers together and jumps at exactly the same time, the earth will move about 5e-15 m (0.000005 nanometers) but will return to its original position after the Europeans have returned to the ground.

Qingu's avatar

@Vortico, that’s cool… orbital mechanics are really sort of beautiful in that way, I think.

I am not smart enough to make the calculation needed to determine how much energy would be required, though.

JLeslie's avatar

Maybe if we set off a bunch of nuclear weapons on the moon. Or, does the moons gravitational pull only keep us on our axis, and not effect our orbit around the sun?

CyanoticWasp's avatar

I don’t think so, without a tremendous concentration of “that or something like it” in a deliberate attempt to do as you suggest.

Consider the asteroid hits that Earth has taken in its history, which may have had some effect, but the planet seems to have been hospitable to “life as we know it” before the hit (without the employment prospects, that is), and was again afterward.

My understanding is that the planet acts similarly to a gyroscope, where forces that act against its continued spin and trajectory are met with the inertia of the entire planet (in its regular orbit) and changes due to outside forces (and massive earthquakes, such as the undersea quake that caused the Boxing Day tsunami—and the tsunami itself) merely cause temporary wobbles that are soon absorbed as the planet does what it has done for billions of years: it spins and revolves around the Sun, pretty much the same as it has for all those years.

Joybird's avatar

March 3, 2010, Chili experienced an earthquake that knocked the earth off its axis by micro seconds. It has to make you wonder whether the same occured during the bombing of Japan. That’s not something I think we would have been able to measure back then. But if a volcanoe eruption could do that…then certainly several natural disasters or natural disasters set off by man made ones might be able to have that effect. Even seconds change our orbit from what I understand. Could that bring us into closer contact with an asteroid that previously would have missed us? But yes we were knocked seconds off our axis last year and that has resulted in minutely shorter days in the rotation of the earth.

IchtheosaurusRex's avatar

You would not do this by blowing up something on the Earth. You’d have to steer an asteroid or a group of asteroids near the Earth in such a way that the gravitational pull would alter the Earth’s orbit. In order to alter the trajectory of an asteroid, you do the same thing to it, using a smaller asteroid. You see where this is going – ultimately, you steer asteroids by the micro gravity of passing spacecraft. In theory you could do this with current technology, but it would take tens of thousands of years, perhaps hundreds of thousands, and I wouldn’t want to be the one to work out the orbital mechanics.

We do need to think about this – eventually. In around 500,000,000 to 1 Billion years, the gradual increase in radiance from the sun will make the Earth uninhabitable, unless we can figure out a way to move it into a higher orbit. When the sun ultimately becomes a red giant, the Earth will be consumed unless we can move it out even farther.

mattbrowne's avatar

Excellent question, @Qingu. In addition to what @Vortico said about Saturn V rocket I’d like to mention the effect of gravity assists, see

which does have a small influence on the planet. For example to gain

“interplanetary momentum while already in flight, the trajectory of the Cassini mission included several gravitational slingshot maneuvers: two fly-by passes of Venus, one more of the Earth, and then one of the planet Jupiter.”

So in 2050 for example we might be able to construct a large, massive “spacecraft” in space, perhaps a small near earth object (attach rockets to it) and send it on a trajectory around Earth several time to slow it down just a little (“knock it” out of its orbit).

If humanity is faced with dramatic climate change because of global warming and all political solutions fail and all the geoengineering proposals don’t work either, this approach might cool down our planet just a little, pushing it away from the sun. Just a little.

Vortico's avatar

One fact I’d like to point out is that the earth does not lie in a perfect orbit, neither does it rotate on a perfectly constant axis. Planets orbit without any trouble in elliptical paths, so if for some reason we “knocked it off its orbit”, we would simply transform its orbit path to a more elliptical shape.

@Joybird: Though I don’t doubt the earthquake had an effect on geological cycles, you must realize how unbelievably small microseconds are. In a circle of 360 degrees there are about 1.3 billion microseconds. When you look up at the sky at night, you are seeing half of these, and each visible star is a few hundred thousand microseconds.

CyanoticWasp's avatar

@Vortico correct me if I’m wrong, but if each circle contains 360°, and each 1° contains 60 minutes, and each minute contains 60 seconds, and each minute contains a million microseconds, then:
360 * 60 * 60 * 60 * 1,000,000 = 216,000,000,000 microseconds in a circle, correct?

So you’re right as far as “billions of microseconds in a circle”, but even if we had only a single one-microsecond event in each of the 6 billion years of Earth’s history, then that would still be a change of about 36 seconds, wouldn’t it?

And according to the Bloomberg article I’m looking at, the Indian Ocean tsunami changed the rotation by about 6.8 microseconds. So these things will add up.

Vortico's avatar

Whoops! I believe we are both wrong on the number of microseconds in a circle. The correct amount is 360° × 60 arcminutes/degree × 60 arcseconds/arcminute × 1,000,000 microseconds/arcsecond = 1.3 trillion.

In this context, I think that the change of axis does not multiply given time. A lot of information in the media is pseudoscience if you ask me. The purpose is to entertain, after all.

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