It's come to my attention that I asked my original question all kinds of wrong. I gave a bad example and I didn't give enough important story details. I've also realized I didn't even ask the question I'm really looking for the answer to anyway. I apologize for all of the above.

What I'm really looking for is how possible/plausible it is that any space agency could spot some truly massive object that doesn't reflect light heading towards us in time to give us somewhere around 50 years or so to come up with a solution while in no way alerting civilians to our impending doom. I'd also like to know how close this "thing" could get to Earth before amateur astronomers would notice it.

Another important detail: Gravity has no effect on this thing. Its path isn't affected by the gravitational pull of other objects and it doesn't pull anything towards it.

I hope this edit makes it fit this site better. And thanks to everyone who answered my original question.

  • $\begingroup$ Massive black hole, or regions of space are being folded into another dimension. $\endgroup$
    – Len
    Mar 29, 2018 at 13:53
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    $\begingroup$ These are basic math and astronomy questions ("how far is Pluto from Earth" and "how fast does light travel"), which aren't WorldBuilding. $\endgroup$
    – RonJohn
    Mar 29, 2018 at 14:32
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    $\begingroup$ A more on-topic question than just asking us about the distance of Pluto from Earth in light-hours would be to ask if anyone would actually look. Pluto is, after all, just an unimportant kuiper belt object. The only thing special about it is that it's the first we found. $\endgroup$
    – Philipp
    Mar 29, 2018 at 14:34
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    $\begingroup$ It may be worth starting a new question with the real question that you are wanting answered, instead of editing this question, mostly because by changing the question you are invalidating existing answers that answered the original question. It may be that this question will get reopened with the edit, and it's also possible that people who have answered the original question will come back and edit their answers to answer the new question, but you're much more likely to get new answers that better fit your new question if you ask it as a brand new question. $\endgroup$
    – AndyD273
    Mar 29, 2018 at 16:19
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    $\begingroup$ Not really, but I would suggest dropping the word "massive". Otherwise you would have a long explaining to do as to which laws of nature apply to your object and which don't. $\endgroup$
    – Alexander
    Mar 29, 2018 at 17:19

3 Answers 3


Well, a simple answer to your question is that if we observe Pluto being eaten by your planet-eater on Earth, it would have happened 5.5 hours ago, that being the time taken by light to travel from Pluto.


For Earth to notice something quietly happening to Pluto, it would take anywhere from some days to some weeks, as astronomers more and more frantically focus their telescopes where Pluto ought to be and find themselves unable to find it.

The step between "I can't find it, it's my fault, I'm not good enough" and "Pluto is not there" is actually a huge step and very few would have the chutzpah of announcing they've lost Pluto - or found Mars. It's not something you want to be happening to you.

On the other hand, if the collision or whatever happened spectacularly enough - say a large flash of light, Charon spiraling out of control, a cloud of broken planetesimals where Pluto used to be - then it would be 5 hours and a half, more or less (but relativistically speaking, it would be "instantly" - since nothing could happen on Earth with information about Pluto before those 5.5 hours). Then it would take some time to understand exactly what had happened to Pluto.

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    $\begingroup$ I think this is more what OP is looking for; how often are people looking at Pluto, and how long would it take them to realize their instruments weren't off and it was actually gone. $\endgroup$ Mar 29, 2018 at 14:52

Light from Pluto is about five and a half hours from the Sun. The Earth is about eight light minutes from the Sun. So the answer to your question is about five and a half hours, give or take.

Source: NASA

Redoing their math, they are rounding up slightly. They are using a time of 19680 seconds, which is 5.466... hours. So at most 5.6 hours (and some seconds) and possibly as little as 5.3.


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