# If every star in the universe except the Sun were destroyed, would we die?

If every star and planetary system and blackhole—all mass (not sure whether to include dark matter or not) except what directly makes up our solar system—in the Universe except the Sun were wiped from existence (not explosively destroyed) would the existence of life on Earth be immediately (~within a few years of us noticing they'd disappeared) threatened?

• This question is meaningless in the context of the Big Bang and the expansion of the universe (as per FLRW ). For everything to vanish, some of it would essentially have to had never existed at all - we see galaxies that were formed in the first period of star and galaxy formation because of that speed of light issue. – StephenG Sep 5 '19 at 20:25
• In addition to what StephenG said, even a single star disappearing is probably impossible in the context of general relativity, since GR has local conservation of mass/energy, and its sudden disappearance it would seem to imply an instantaneous change in the curvature of spacetime which I don't think is allowed. Might be better to imagine all the stars being transformed into dark matter or something, so their gravitational effects wouldn't change instantaneously (though in time the dark matter would disperse over a larger region) but they would cease to emit electromagnetic radiation. – Hypnosifl Sep 5 '19 at 21:09
• @elemtilas thanks for the edit, that title's much clearer. – theonlygusti Sep 5 '19 at 22:12
• If your intent is for the rest of the universe to suddenly "disappear" from the viewpoint of observers on Earth, having the solar system somehow transported into a pocket dimension might be a cleaner way to achieve that (as it sidesteps the "we see light from millions of years ago" issue, along with many of the other physics questions people have raised). Something of this sort was part of the backstory for Prof. M.A.R. Barker's Tekumel setting (best-known for the RPG, but he also wrote novels set there) if you want an example of how others handled it. – Dave Sherohman Sep 6 '19 at 7:29
• @Hypnosifl Not really, you just have to assume the universe didn't disappear everywhere in an instant, but rather started disappearing from the most distant parts (relative to Earth) to the closest parts at the speed of light. To us, that would look as if the rest of the universe just blinked out of existence, even though it would be something that started billions of years ago, and only just reached us now. Gravity also propagates at the speed of light, so there's no observable conflict (beyond the "energy just vanishes" thing :). – Luaan Sep 6 '19 at 8:37

No. Life on Earth and our solar system in general would not be harmed by this sudden universal destruction.

Everything outside of the Solar system affects us via electromagnetic radiation, gravity, and "matter transfer".

The EM radiation flux is too weak to really do much, other than marvel at through telescopes. With the rest of the universe gone we'd actually be safe from the potential of a nearby Gamma Ray Burst.

The gravitational influence of our stellar neighborhood is far too weak to majorly change anything like planetary orbits. Same goes for the galactic center we orbit around. So probably no kicking asteroids or comets on a collision course with us.

The final chance for an influence is through "matter exchange". There's no longer the chance for big rocks to come sailing through our solar system from beyond, so again we're safer here. No more worrying about rogue black holes or ejected exo-planets disrupting local orbits.

We do lose Cosmic Rays in this ordeal, though. Cosmic rays produce most of the Carbon 14 we could use for radio-carbon dating, but we've already messed that balance up through weapons testing.

I don't know enough about biochemistry to attest to the importance of the isotopes produced by cosmic rays, but at a casual glace and google they don't seem to be terribly impactful or necessary.

So without cosmic rays our background radiation levels would decrease and electronics would become slightly more reliable. Once again we are made even safer.

Ultimately we will perish as a species when the sun goes through its stellar life-cycle and the solar system (now entire universe) cools... but that'll probably happen anyways on a longer time scale if the Heat Death of the Universe holds true.

• C14 is only good to about 50,000 years ago anyhow, no big loss there. We've got other means of dating older stuff. – Darrel Hoffman Sep 6 '19 at 14:09
• @DarrelHoffman Most of the other means are also based on isotope decays though, like O18, so we would also lose them. – Alessandro Sep 6 '19 at 15:00
• It's interesting to think that even if all that mass disappearing had enough gravitational influence to send our solar system hurtling through space at high speed, we'd never know because we'd have no reference point by which to judge that we were moving. – bta Sep 6 '19 at 23:13
• We are already hurtling through space at a high speed, and the gravity of the galaxy just keeps us going in a circle at that speed. If you remove the rest of the galaxy our speed wouldn't change, just become meaningless without reference, like you said. – abestrange Sep 7 '19 at 1:07
• Don't we technically have no reference right now? How do we know anything we measure against isn't already going super fast? – Nelson Sep 7 '19 at 4:22

We wouldn't even notice for several years.

The closest star to us (aside from the Sun) is Alpha Centauri, which is just over 4 light-years away. That means that whenever we look at Alpha Centauri from earth, we are seeing light that left the star over 4 years ago. If Alpha Centauri were extinguished today, we wouldn't even realize it until 4 years from now! For most stars, it will take decades, centuries, or longer before we see them wink out of existence - whatever effect that might have, it will definitely not be "immediate".

• I don't like this answer, it's just a wordplay on what immediate means. Immediate could just as well mean immediate from our perspective, meaning the stars would disappear all at once. The real order at which it happened is not important, the question was hypothetical anyway. – Tomáš Zato - Reinstate Monica Sep 6 '19 at 10:01
• @theonlygusti Changing a question entirely after an answer has been given (with high upvotes) is very bad form across all SE sites. – Cloud Sep 6 '19 at 11:53
• @Cloud I disagree that I changed the question entirely. The meaning of the question should have been obvious form the get-go anyway, please have a look at the original form of the question. This answer is just nit-picking the vocabulary used in the original phrasing of the question, not actually containing any interesting insights. And I specified the question within half an hour of this answer being posted, which was hours before this question got onto the Hot Network Questions list (which is what I assumed happened based on current upvotes) – theonlygusti Sep 6 '19 at 14:52
• @theonlygusti The fact that I didn't correctly guess your intended meaning doesn't mean I'm nitpicking. This is a science-based answer that focuses on the immediacy of the effects, which are nil. I don't see why it's more reasonable to assume a special universe-wide scheduling of stellar blackouts that appear simultaneous from earth, rather than to assume a single universe-wide "lights out" event. The original question provided precious few nits to pick at, just an under-defined scenario open to interpretation. I feel as if you ordered a soda and are miffed you got Pepsi instead of Coke. – Nuclear Wang Sep 6 '19 at 18:36

### Frame challenge: It was not them who disappeared, it was us.

What is more plausible (but still a twist in the laws of physics), that an entire universe vanished or that a single solar system in the outer rim of a galaxy vanished? (Occam's razor)

It was not the Sol System that remained, it was the Sol System that was shifted to another, empty, reality. Maybe a huge wormhole opening passed over us, or we were inentionally dislodged to build a hyperspace lane.

This theory has the added bonus of zero wait to witness the entire starry sky become pitch black.

It is like the anecdote when a storm blocked all forms of travel across the English Channel and the british newspapers headlined:

Storm isolates the continent.

With that in mind, we can answer the question:

would the existence of life on Earth be immediately (~within a few years of us noticing they'd disappeared) threatened?

A: Probably no, if the pocket dimension we were sent to is stable. Should be, shouldn't it?

• And that’s exactly the plot of Quarantine by Greg Egan. – Mike Scott Sep 6 '19 at 13:40
• @mikescott Thank you very much for the reference. Should be a very nice read. – Mindwin Sep 6 '19 at 16:32
• Good lateral thinking. – Peter - Reinstate Monica Sep 7 '19 at 8:41
• Also see: The society, a Netflix series – ghosts_in_the_code Sep 14 '19 at 15:03

There would be basically no effect.

First off, even gravitation is governed by the speed of light, so we would not notice for thousands of years (well, we'd notice Alpha Centauri after about 4 years). By the currently understood laws of physics, no information about a remote object can travel faster than the speed of light. We theoretically will see some hilariously small quantum fluctuation differences, but we wouldn't actually be able to prove anything from them until information traveling at the speed of light catches up.

However, this can be taken in another way. Since you're looking at gravitation, we can compute the effects. Distance is a major player in this equation, so lets pick the closest star, Alpha Centauri. It is 4.3 light years away. that's $$4.132\cdot 10^{16}\ \mathrm m$$ away. Its mass is roughly 0.123 solar masses, or $$2.446\cdot 10^{29}\ \mathrm{kg}$$. Throwing them into $$a_\mathrm{grav}=\frac{GM}{r^2}$$ we get an acceleration of $$9.5\cdot10^{-15}\ \frac{\mathrm m}{\mathrm s^2}$$ ($$G$$ is $$6.674\cdot10^{−11}\ \frac{\mathrm{m}^3}{\mathrm{kg\cdot s^2}}$$, if you want to run those numbers). So while the earth is pulling on us at $$9.8\ \frac{\mathrm m}{\mathrm s^2}$$, A. centauri is pulling with a whopping $$0.0000000000000095\ \frac{\mathrm m}{\mathrm s^2}$$

Now note the $$r$$-squared term. That's why the gravity of Earth is such a big deal and A. centauri, as big as it is, isn't a big deal. The gravitational effects of far away objects is pretty negligible. If there was something that kept emitting light where A. centauri was, we wouldn't even detect it.

In the long run, these small things would matter. If the galaxy vanished, we would stop orbiting the galaxy. Our orbit around the center of the galaxy has a period of about 200 million years, so you'd start to notice the loss of that mass after a million or so years.

The bigger issue would be the worldbuilding problem. Something just broke all of our known laws of physics, and did it in a blink of an eye. What was that thing? How does it work?

And is it still hungry?

These are important questions for the denizens of the last surviving solar system in the universe.

• If “it” ate everything but for unexplained reasons chose to spare our entire solar system, it would behoove us to try to figure out what those reasons are. – WGroleau Sep 6 '19 at 4:04
• i guess "it" could pick out earth and neatly place it in an empty universe for quarantine and observation purposes, (or just for lols) :D which for earth would mean the whole rest of the universe was obliterated – brett Sep 6 '19 at 5:05
• It's not the acceleration due to gravity that you should be interested in. You should be looking at the tidal pull. Ie the difference in the earths acceleration and the suns acceleration. It scales with the inverse of distance cubed. – Taemyr Sep 6 '19 at 12:56
• @Taemyr That would make it even less of an effect than straight up gravitational attraction. Tidal pulls really only start being a substantial player at close distances (such as from our moon to our oceans) and/or absurdly high gravitational fields (spaghettification comes to mind) – Cort Ammon - Reinstate Monica Sep 6 '19 at 14:43
• Agreed. Cubed grow faster than squared. – Taemyr Sep 6 '19 at 15:50

It depends how the stars go out.

If every other star somehow went supernova, we would be fine for about 4 years. Then, the radiation from Alpha Centauri would hit us, most likely killing everyone on the planet. The safe distance for a supernova is about 100 light years.

On the other hand, if the stars just winked out quietly as you suggested, we'd pretty much be fine, as other answers have stated.

As mentioned in the comments, it would seem that the closest star capable of going supernova is the IK Pegasi binary system, 150 light years from Earth. The closer stars just aren't big enough to blow up in the same way.

Looks like we're safe for now!

• Alpha Centauri (A or B) is much too small to go supernova. If it went like a regular nova, it would be a spectacular sight, but it wouldn’t hurt us. – Mike Scott Sep 6 '19 at 7:10
• @MikeScott We aren't really in the realm of known physics. A+B Centauri are both going super-nova... would the radiation kill us or not? – J. Chris Compton Sep 6 '19 at 12:53
• @J.ChrisCompton They’re not going supernova at all; they can’t. If they’re blowing up in some spectacular fashion unknown to current physics, then of course we don’t know enough to know if it will kill us or not. – Mike Scott Sep 6 '19 at 13:39
• @MikeScott do you happen to know what's the closest star that could go supernova, so that the answerer could update the time bit? – John Dvorak Sep 6 '19 at 18:02
• @JohnDvorak There’s a list here: en.m.wikipedia.org/wiki/Near-Earth_supernova. But the closest ones that might go in the near future (i.e. the next million years) are Antares and Betelgeuse, I believe. – Mike Scott Sep 6 '19 at 18:42

We might individually die in the upsurge of doubt, despair and religious-inspired unrest, since this would pretty much constitute proof of the existence of some kind of divine being who is not consistent with any existing religion. Greg Egan’s novel Quarantine is about a similar scenario, although it plays out faster since the stars all disappear over a matter of minutes rather than having to wait thousands of years for the speed of light. But there would be no significant physical effect on the solar system — all the problems would be psychological.

• "this would pretty much constitute proof of the existence of some kind of divine being who is not consistent with any existing religion" Why? – user76284 Sep 6 '19 at 18:56
• Yeah, this is pretty much what I thought... the results of folk noticing “ Aack, all the stars are going out!” Is likely to be quite dangerous even if the phenomena itself doesn’t physically touch us. – Megha Sep 6 '19 at 22:27
• @user76284 - it would constitute proof inasmuch as we can’t figure out any other potential cause, so we must believe it (proof being, I think, a word about certainty more so than absolute truth). Or proof since we’re on the wold building so if this happens in our world we must be at the mercy of an author, which is a being both powerful and merciless ( and not a deity named in most religions), oh no! – Megha Sep 6 '19 at 22:41
• @Megha "It would constitute proof" I'm not sure I understand you. Proof of what? "a being both powerful and merciless" Being powerful doesn't make you a deity. – user76284 Sep 6 '19 at 23:12
• @Megha And killing the whole universe except the solar system is not necessarily merciless. Maybe there was no other life out there (anymore) and this was the only way to preserve the only (or last) life in the universe. Seems like a thing a good god would do. – Graipher Sep 7 '19 at 20:51

within a few years of us noticing they'd disappeared

Absolutely.

Of the few thousand we see in the night sky the internet suggests to me that there are only 76 stars within 100LY of us. At the point where those have all been seen to have gone out, you'll be dead. Climate change may have done for large parts of human coastal construction.

There are a few hundred billion stars in the Milky Way, which is around 150,000 LY across, in that time we should have had at least another ice age. It's the entire duration of human history.

The nearest major galaxy to us is Andromeda, it's around 2.5 million LY away. That's over 10 times as long as humans have existed before the light gets to us. 2.5 Million years before we know anything is up with it.

So yes, by the time we notice the rest of the universe is gone, all life on Earth will be long gone as well.

• Cheeky. Almost certainly not what OP meant, but this was funny. My +1 is entirely for making me laugh. – Loduwijk Sep 6 '19 at 17:15

Nothing would happen. Solar system is self-sufficient enough. It would be only little influenced if rest of universe somehow ceased to exist.

That said, anything that would preserve our little bubble intact and simultaneously destroyed everything else, is almost certainly unimaginable to science.

• Mmm this is my first inclination also. Do you have citations/proof as to why though? – theonlygusti Sep 5 '19 at 22:10
• There's no proof for a negative. We can only say that all the 4 forces known to physics (electromagnetic, gravity, strong and weak interaction) are too weak -have too little field strength - at interstellar distances to have effect on terrestrial life. It can be calculated. So it makes no difference when all fields produced by deep space sources become zero. – Juraj Sep 7 '19 at 20:06

If the Mach's principle is actually valid (and it cannot be quite ruled out), then local properties of matter (inertia in the "original" formulation) depend on the distribution of mass in the rest of the universe.

The exact effects depend on the details, but at the very least the planetary orbits will be disturbed, if not destroyed outright.

But it is likely the interactions are still governed by the speed of light limit, so apart from the stars going gradually out we won't even notice in billions of years. Unless the deity responsible for this timed the disappearance in such a way that its light cone converges on us right now.

• This is an important point (change of G, change of momenta) that the other answers missed. – amI Sep 8 '19 at 18:33
• @aml They haven't missed it, this would happen only if some variant of Mach's principl holds - and that's in itself rather controversial, to put it mildly.... but cannot be ruled out. – Radovan Garabík Sep 8 '19 at 18:56
• If they didn't miss it then they ignored it? Einstein wouldn't if asked about an emptied universe -- but he was busy with GR explaining the universe as we see it. What does a gyroscope point to if not the distant universe? (it points to the local vacuum as determined by radiations from the distant universe) – amI Sep 8 '19 at 21:50

Given your unlikely scenario, it IS possible that our star IS the ONLY star in the universe RIGHT NOW since the light from distant stars takes so much time to reach us.

If the closest star is several light years (the distance light travels in a year) away, we may not find out for several years.

Distant stars have near-zero impact on us, with even a close supernova or cataclysmic stellar death having almost no effect on us.

THAT is how big the universe is. It is VERY BIG and the gaps between stars are large!

The only concern I would have is that the back-pressure from the Solar wind at the Heliopause would be removed, as there wouldn't be other star's matter to contend with. This would eventually speed up the Solar wind around Earth, which might be enough to rip off our atmosphere. Note that I have no specific evidence of this.

 NASA found that some of the Solar wind particles bounce backwards, slowing down the Solar wind directly. This was detected on Earth: "once the solar wind hits the termination shock it creates a pressure wave. That pressure wave continues on to the edge of the heliosphere and partially rebounds backwards, forcing particles to collide within the (now much denser) heliosheath environment that it just passed through. That’s where the energetic neutral atoms that IBEX observed were born." https://www.nasa.gov/feature/goddard/2018/as-solar-wind-blows-our-heliosphere-balloons

• Hi Jim, and welcome to Worldbuilding! Given that the orbits of all the major planets, including Earth's, lie well within the heliopause, I'm struggling to imagine a way that its removal would impact the speed of the solar wind on Earth. – Dubukay Sep 6 '19 at 17:57
• @Jim, +1. I see nothing wrong with your answer since you are postulating a possible effect of an event which cannot be studied scientifically. For all of perceivable time, the rest of the universe has existed so we have no history of variance in the one attribute we are asked to study. The universe has never even been 0.001% missing from our point of view, so we cannot scientifically predict what a 100% missing state would look like. Your contributions of solar wind effects is a worthy addition to the conversation and not deserving of the down votes it received. I have negated what I can – Henry Taylor Sep 7 '19 at 2:00
• Dubukay, It's actually worse than I postulated, as shown in my edit to my answer. – Jim Sep 8 '19 at 14:01

Others have posited a sudden teleportation of our solar system to a pocket dimension. However, teleporting our solar system to the middle of the Bootes void has one less objection (i.e., we know that the Bootes void actually exists, whereas pocket dimensions are still the stuff of conjecture and fiction), and would have the same effect.

As I understand it, if our solar system were in the middle of the Bootes void, we would not have learned that other stars even existed until modern times, when telescopes were invented.