View Full Version : What would happen if the sun moved closer to the earth?

08-02-2011, 01:55 PM
What would happen if the sun moved closer to the earth?

Assuming that it is moving close enough to have an effect on the earth and everything that lives there, but not so close that it burns everything to a crisp. I still want some people to survive and continue living there.

So, some questions.

- assuming the heat melts the ice caps, how much of the earth would be covered in water?
- would there be any medical effects on the humans? (cancer, breathing problems, etc.)
- how would the landscape be affected?
- would there be any changes to the weather or moon?
- what possible reason could there be for the sun moving?
- what would be the most common form of death in this kind of world?

Anything else you could tell me would be great.

Obviously this is a hypothetical, so your best guesses are more than welcome.


08-02-2011, 02:13 PM
I think the sun would be more likely to expand than to actually physically move. The next stage of the sun's life will be the Red Giant phase, which I believe will happen in the next few billion years.

I'm no expert, but I think expansion would increase the sun's gravitational pull, so you'd probably find that Mercury would be incinerated.

It depends on how much closer the sun is after it's moved/expanded. Our planet is currently in the habitable zone due to its perfect proximity to the sun - not too cold, not too hot. It would have to move closer by quite a significant distance for that to change.

The Nasa website have a good summation on what they call the Goldilocks Zone: http://science.nasa.gov/science-news/science-at-nasa/2003/02oct_goldilocks/

From this page: http://helios.gsfc.nasa.gov/qa_earth.html

What would happen if the Sun moved closer to the Earth by 1 meter? How much would the temperature increase on Earth?
There would be an increase in temperature if the Earth to Sun distance became much smaller, but 1 meter is insignificant. For example, the Earth is actually closer to the Sun during the northern hemisphere winter.

08-02-2011, 03:56 PM
The distance between the Earth and the Sun is determined by the Earth's orbital velocity. So if the Sun moved, then the orbit would become more elliptical. The orbit is already elliptical and the Sun-Earth distance varies by about 3 million miles. It is shortest in the Northen Hemisphere Winter and that probably answers the question. The seasonal variations due to axis tilt are dominant over these types of distances. It is hard to see how (or why) the distance could be shortened significantly (especially over a short timescale).

When it comes to the red giant phase, it will be 'Bye bye Earth' (even before then). The habitable zone will be much further out (supposedly around the region of Pluto).

08-02-2011, 03:58 PM
This depends on whether the Sun is moving closer to the Earth, or the Earth is moving closer to the Sun. If the Earth moved, then I'd take that to be a change in orbital radius. The effects of this would depend on how far the Earth moved - anywhere from "almost undetectable" to "everyone dies". By the sound of it, you're after somewhere in between - small move, enough to warm the planet a little. Nobody is quite sure what the effects of this would be; it's similar to the global warming debate, and the models are still not reliable enough. A tiny change in the simulation can change it from a desert planet to Day After Tomorrow-style freezing. My guess is that you'd get melting of the ice caps, leading to disruption of all sorts of currents, thereby actually cooling areas closer to the poles, but that'd settle out eventually and the increase in heat received from the Sun would eventually result in an overall warming. Somewhere between the warm band by the equator and the cold poles there would be an area that ended up with about the same climate as it had before, almost. More energy received from the Sun would mean more violent weather though.

If the Sun moved closer to the Earth, that's a different thing entirely. The Sun is at the centre of a slightly squished circle around which the Earth travels. If the Sun moved towards the Earth, then it would be leaving the centre of that orbit, which would mean the Earth would enter a new orbit. The Earth's velocity at that point would be whatever was required to orbit at that distance, and wider orbits are slower, so the Sun moving towards the Earth would result in the Earth lacking speed, so it would fall closer to the Sun, gaining speed as it did so, and then slingshot around and come back to more or less where it started. So, whatever season it was when the Sun moved would become the new winter, and then there would be a summer that's hotter than anything the Earth has had in a loooong time - like, at least since the dinosaurs. The difference between summer and winter would be greater too, because the orbit would be more elliptical, probably - unless of course the Sun moved at the moment that would put it closer to the point midway between the twin focii of the Earth's elliptical orbit, in which case the orbit would get more circular and the weather all year would be similar to whatever it was when the Sun moved.

08-02-2011, 04:36 PM
Remember the inverse square law: The amount of radiation received is proportional to the square root of the distance.

So if we call the amount of sunlight we get now '1,' if the sun (or more likely, the earth) were to move so that the distance was halved, we would get 4 times the amount of sun we do now.

Decide the amount of sunlight you want to fall on the earth, and the math will tell you how much the distance needs to change.

08-02-2011, 05:23 PM
If the sun is the Christmas tree and earth is one of the colourful glass balls, then nothing would happen. We'd move with the sun. Which incidentally is exactly what is happening and has happened continuously since this solar system formed ca 4 billion years ago.

08-02-2011, 07:23 PM
What would happen if the sun moved closer to the earth? -- what possible reason could there be for the sun moving?

Since a reason seems to be necessary for your story, some basic science is required. As the good Swedish doctor implies, the questions are so earth-centric as to defy logical answers.

The sun can't move "closer to the earth." In fact, the sun moves every second of every day of every year in its orbit around the center of the Milky Way galaxy. Our sun is one of many suns way out on one of the spiral arms, sailing at a fair clip.

The earth and all the other planets, asteroids, comets, and sundry stuff orbiting the sun continue in their separate paths all the while that their sun moves.

In your story, the earth will have to move closer than its average distance of 93,000,000 miles. To do so, the earth's orbit will need to be slowed or changed.

One hypothetical cause could be a rogue planet from outside our solar system sweeping close enough to the earth to slow it or pull it from its regular orbit.

The event would be catastrophic, and it's likely most life wouldn't survive. Eventually, the earth in retrograde orbit would spiral into the sun, but before that happens, your story could take place.

There's so much junk science at work here that I'm sure the event may also be blamed on big oil and republicans.

08-02-2011, 07:38 PM
Thanks for all your help guys, I'll dig deeper into the science of the earth changing orbit instead, and the red giant phase. Thanks again.

08-02-2011, 11:32 PM