How Would Affect The Global Temperature Going Away From The Sun?

[AdrianG]

How would affect the global temperature going away from the Sun?

 

Hello,

 

I’m new on this forum and not quite a very smart person. I hope somebody will be able to give me an answer to my question.

 

I saw some documentaries about an asteroid hitting Earth and taking our planet out of the Sun’s orbit. This happened gradually year by year. The Earth’s temperature became colder and colder until the Earth left the Sun’s orbit. I’d like to know if somebody could tell me how far from the Sun should the Earth go to have a significant average temperature drop. I know now the average distance of the Earth from the sun is ~150 000 000 km.

 

Thank you!

[Eclogite]

Hi Adrian, welcome to the forum.

 

First, it sounds as if the documentary was using a rather bizarre example to illustrate a different point. Any asteroid large enough to make a major change in the Earth's orbit would, upon impact, destroy all life on Earth - with the possible exception of microorganisms living deep in the Earth's crust.

 

Now your principle question relates to what is sometimes called the Goldilocks Zone: that region within which a planet could sustain liquid water and which might therefore be capable of supporting life. The trouble is that it is not a simple matter of distance: Venus and Mars are both within the Goldilocks zone, but neither is capable of supporting life - one is too hot, the other too cold.

 

That is, however, not just a matter of distance, but other factors. In the case of Venus there is no plate tectonics and so carbon dioxide built up in the atmosphere rather than being absorbed in carbonate rocks and cycled into the mantle. This caused a runaway greenhouse event, so that the surface temperatures there are hot enough to melt led. (Greenhouse gases in our atmosphere also keep it equable - without them I think the average temperature would be below freezing.)

 

Mars, is too small to have retained a significant atmosphere and so it is both cold and devoid of the necessary atmospheric pressure at least for complex life forms.

 

If we moved the Earth to Mar's orbit there would be massive changes, the world would enter an ice age, but the equatorial and mid-latitudes would likely remain livable.

 

I hope that goes some way to answering your question, if somewhat indirectly.

[AdrianG]

Hello Eclogite,

 

 

Thank you for your answer, yes your answer is quite clear to me, I understand your point of view and I guess you are wright, I'm not an astronomer but I think I don't have problems to understand that a large asteroid, large enough to move Earth from it's orbit would kill all life on Earth, but this was the case in this documentary. I didn't saw it from the beginning, but the action was 1 year from impact, 10 years from impact and so on.

 

 

Anyway, what could be the reason for Earth to exit the current orbit around the Sun? Could a large asteroid or a comet coming close to Earth have a large enough gravitational attraction to pull away the Earth from it's orbit? Or increase the Earth's speed causing our planet to further itself from the Sun?

 

 

I saw this documentary last year, and it troubled me a bit. And with your help, maybe I could understand what can cause such a phenomenon.

 

[CraigD]

Welcome to hypography, AdrianG! :) Please feel free to start a topic in the introductions forum to tell us something about yourself.

I saw some documentaries about an asteroid hitting Earth and taking our planet out of the Sun’s orbit.

I don’t find this a plausible scenario, for 2 main reasons:

• To change a planet from one nearly circular orbit to another requires at least 2 “push” changes in velocity (delta Vs), one at its original orbital radius, one at its new one. A single push, no matter how large, would cause the Earth to enter a less circular elliptical orbit. For example, if you changed the Earth’s velocity in the direction of its orbit by about 2945 m/s, its new orbit would be an ellipse with perihelion (closest to the Sun) of its current orbit (1 AU), aphelion (furthest) of Mar’s orbit (1.5237 AU). To make it have a circular orbit the same as Mars, it would need a delta V of 2648 m/s at aphelion.
• There’s no asteroid massive enough to do this. The largest asteroid, Ceres, has mass about 943000000000000000000 kg, Aphelion about 2.9765 AUs. If Ceres’ orbit was somehow suddenly changes to collide with earth, it would hit at a relative speed of about 6658 m/s. If its momentum could somehow be perfectly (elastically, like 2 ideal billiard balls) transferred to Earth, it would change Earth’s velocity by about 2.1 m/s, less than 1/1000th that needed to put Earth on a transfer-to-Mars orbit.

Whether done by many small asteroids over many years or by a the single, perfectly efficient collision with the biggest one I example above, there just isn’t enough momentum in the asteroids to much effect Earth’s orbit.

 

I’m don’t know the documentaries you’re talking about, Adrian, but suspect they were just using a change of Earth’s orbit as a dramatic plot device to show how different Earth would be were it at a much greater distance from the Sun, not imply that this could happen.