# Is it possible for the earth to come off orbit and crash into the sun?

1. Oct 28, 2013

### andyM1998

Or get so close that human life will be destroyed

2. Oct 28, 2013

### gplayle

Yes, but it would have to take something significant for it to do so, and is not as likely as this question might be hinting towards.

3. Oct 28, 2013

### OmCheeto

Yes. If a rogue black hole were to sweep though our solar system, the earth might get caught in its gravitational field and fling us right into the sun.

They should make a movie.

4. Oct 28, 2013

### Chronos

It is also possible the earth may drift away from the sun and become a rogue planet.

5. Oct 28, 2013

### Staff: Mentor

To be clear, it is entirely possible for this to happen but there must be a cause. The Earth isn't simply going to start spiraling inward and be eaten up by the Sun for no reason. As to how LIKELY it is... well, let's just say that the chances of a rogue black hole getting close to us is pretty remote. Space is REALLY REALLY big.

6. Oct 29, 2013

### BobG

It's remotely (very, very remotely) possible.

It's far more likely that the Sun would expand large enough that all human life will be destroyed. In fact, the only thing that makes it unlikely is the chances of any species currently on Earth (including us) surviving long enough to still be around when the Sun does expand.

7. Oct 30, 2013

### mathman

That won't happen until several billion years from now. I suspect that intelligent life (if it survives global warming) will have figured out how to deal with it.

8. Oct 30, 2013

### ModusPwnd

I think that its less than a billion until the sun manages to evaporate away the oceans (~700 million IIRC). That could kill human life on earth before the sun engulfs the earth.

9. Oct 31, 2013

### mathman

I can't dispute your time estimate. However, the point I am making is that homo sapiens has be around for around 200,000 years. Current technology has been around on the order of about one or two centuries. A few hundred million years is enough time to plan for the demise of the earth.

10. Nov 1, 2013

### BobG

While calculating average species lifetime is an inexact science, the average lifetime for any species is about 5 to 10 million years. The average lifetime for mammalian species is around 1 million years.

Humans probably won't be around. But if there is some other intelligent species around, they'd either have to rely on knowledge being passed across species somehow, or would have much less than a few hundred million years to develop their plans.

(The problem of how to pass knowledge down the years through multiple species or at least would be available and likely discovered by a future species would be kind of interesting.)

11. Nov 2, 2013

### mathman

Human beings are unique among species in that we can write things down. Whatever intelligent life exists a few hundred millions years from now will presumably have available everything written down since writing was invented.

12. Nov 5, 2013

### bahamagreen

I read something a long time ago that suggested the Earth could be temporarily moved out of and back into orbit in order to avoid an asteroid by igniting the equatorial region of a continent or maybe an ocean for about 12 hours (using much of the worlds' nuclear arsenal to do so).

The idea is that the fire (kind of tricky on the ocean) would do the pushing with "radiation pressure" or something, and the 12 hours or so would make the push out of orbit and then back in as the Earth rotated... kind of a delicate maneuver if done deliberately... might have to stagger the detonations and have a quick and sure way to extinguish it all after... very bad idea if the result of an accident, war, or error.

I'm not even sure if the principle is mechanically sound. It would be a shame if that was the best idea anyone could come up with.

In the long run, with enough foreknowledge and technology, maybe the way to make a correction to the Earth's orbit would involve messing with the Moon rather than the Earth itself... to focus on moving the barycenter?

13. Nov 5, 2013

### ModusPwnd

But some species go extinct because they continue to evolve, not because they die off. I wish the wikipedia went into this distinction because I would like to know more about it. Considering that human can thrive in just about every climate there is on earth and that we are evolving faster than ever I think its a real possibility that when we go extinct its because we evolve into other animals rather than just dying off.

14. Nov 6, 2013

### Ken G

Given how much smaller the asteroid would likely be, and the fewer consequences it would have to life on Earth, it probably makes more sense to concentrate our attention on moving the asteroid rather than the Earth.

15. Nov 6, 2013

### Ken G

Not to mention the possibility of intelligently designed evolution. By that I mean, if we ever have the technology to deal with the Sun changing, we would almost certainly have the technology to drastically effect the human genome, most likely to the extent that whatever existed by then might not be considered "human" by our present standards.

16. Nov 6, 2013

### Staff: Mentor

Humans are certainly not an average species. We are so different from all other species that it is pointless to look at other species in terms of the expected lifetime.

The effect would be completely negligible. I would be surprised if you would gain a millimeter or even a meter.

17. Nov 7, 2013

### QuantumPion

According to the Doomsday Argument humans will be extinct in about 10,000 years. It is based on the statistical postulate that the world population today is not amongst the first 5% or last 5% of humans to exist (w/ 95% probability), and extrapolates the total human population and timeline for which it occurs. Of course this doesn't taken into account the possibility of immortality, transcendence, etc.

18. Nov 7, 2013

### Ken G

The Doomsday Argument is a logical fallacy. It is the same fallacy that says, if I show you two envelopes, and one has twice the money in it as the other, and you select one at random and see there is $100 in it, then the expectation value of the other envelope is 1/2*50 + 1/2*200 =$125. Clearly, the correct answer for the expectation of the other envelope is also $100, regardless of the probabilities or rules for stuffing the envelopes, because neither envelope has any reason to have more money than the other. This becomes even more obvious if I say one envelope has 100 times the amount of the other, and I calculate the expectation of the other envelope as 1/2*1 + 1/2*10,000 =$5,001. The result of a calculation like this can be completely spurious, depending on the nature of the probability distribution.

So what went wrong in the seemingly innocuous calculation that the expectation should be $125? It is the implicit assumption that the number in the chosen envelope does not correlate with the amount of money in the envelope. The fact that we don't know what the correlation is does not allow us to assume there is no correlation. It is the same with the Doomsday Argument-- we have no idea what is the correlation between our own appearance in the order of born humans, and the total number of humans that will be born. Not knowing that correlation does not allow us to assume we appear at a "generic" time, any more than the amount in that envelope can be assumed to be a "generic" amount in regard to the stuffing algorithm. 19. Nov 7, 2013 ### bahamagreen Hold on, I may be confused about the calculation of expectation value, or probability, or both... On the one hand, after opening one envelop and finding$100, the initial possible configurations of money in the envelops might be interpreted to have must been:

($50,$100) or ($100,$200)

based on the phrase, "...one has twice the money in it as the other..."

then the expectation value of the first is ($50+$100)/2 = $75 and the second is ($100+$200)/2 =$150

so if choosing either one had a p=.5 then the expectation value of having chosen either envelop was:

($75=$150)/2 = $112.50 If this was a game in which after each selection one was allowed to "buy" the other envelop with the money you got from your selection, your strategy would be to always do so... kind of a paradox if you see the initial selection as random. One the other hand, there may be a problem with assuming too much about the phrase "one has twice the money in it as the other"... That relationship applies between two real extant values of which only one is known. That relationship does not necessarily extend between the known value and a third hypothetical value based on a counterfactual hypothesis... For example, if the initial condition was this: ($100, $200) that satisfies the "one has twice the money in it as the other" stipulation. But when one reveals the$100, one does not know if the $100 is the lower or higher value. Extending the possibility to the case to ($50, $100) or ($100, $200) seems unjustified using the "twice" stipulation because the same initial condition might have been stipulated that: "one has$100 more money in it as the other"

in which the ($100,$200) case satisfies the stipulation, but one of the hypothetical cases would be:

($0,$100) which is different from ($50,$100).

The "twice" stipulation may be replaced by others that the initial condition satisfies but which would generate a whole host of different hypothetical cases.

I guess what I'm thinking is that if a particular stipulation is only one of many that achieve the same relation, what is the basis for extending that particular relation to yield the hypothetical case values?

20. Nov 7, 2013

### Ken G

Exactly, that's why we know the expectation value must be \$100, so any calculation that gets a different result is incorrect.
The statement may be taken to be true. However, you are certainly right that an important part of the story are unseen correlations. In other words, we cannot hold that this is the only relevant information-- but all other relevant information is withheld from us. The same is true of the "Doomsday Argument"-- just because relevant information is unavailable to us, it does not mean we can assume it does not exist. One cannot always get away with that assumption when doing probability calculations, such as the claim that there is a 95% chance that we are not in the first 5% of all humans, given that we know our birth number is about 10 billion or so.
Right, one does not know how to do that, which is why one gets an incorrect calculation of an expectation value if one makes certain unjustifiable assumptions. The only justifiable assumption is the symmetry principle that neither envelope is more likely to be worth more, so the other envelope must have a statistical value equal to what is revealed in the first. If you would buy the second envelope for any more than that, you will always lose money in the long run, no matter what system is used to stuff the envelopes.

The connection with the Doomsday Argument is that we cannot assume we have a 95% chance of being in the last 95% of humans, if we also know that our birth number is about 10 billion. There is unknown information about how long intelligent civilizations last that can introduce correlations between birth number and probability of being in the last 95%, and simply not knowing those correlations does not justify asserting we will get a correct result by assuming there are none.