58

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?

Cyn
  • 20,358
  • 3
  • 44
  • 89
minseong
  • 2,056
  • 1
  • 15
  • 28
  • 5
    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 - Help Ukraine Sep 05 '19 at 20:25
  • 1
    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 05 '19 at 21:09
  • @Hypnosifl I am interested in the gravitational effects just .... weirdly disappearing. – minseong Sep 05 '19 at 22:07
  • 1
    @elemtilas thanks for the edit, that title's much clearer. – minseong Sep 05 '19 at 22:12
  • If you want the gravitational effects to disappear I think you might have to switch from general relativity, where this is probably just impossible (violates the basic equations), to some approximate theory like Newtonian gravity or the weak-field limit of GR (the latter is more accurate since it has gravitational effects travel at the speed of light). – Hypnosifl Sep 05 '19 at 22:56
  • 7
    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 06 '19 at 07:29
  • 9
    @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 06 '19 at 08:37
  • 1
    Boötes void has left the chat. – user6760 Sep 06 '19 at 09:33
  • @Luaan - I wasn't talking about a problem with when we would see things disappear, I was talking about a problem with the basic idea of matter "disappearing" in the most accurate theory of gravity we have, Einstein's theory of general relativity. This theory models gravity in terms of matter/energy causing spacetime to become curved, and I don't think it allows instantaneous curvature changes as would be implied if a single star "disappeared", see bcrowell's comment here. – Hypnosifl Sep 06 '19 at 14:06
  • (cont.) Also, in general relativity the overall average density of matter/energy in the universe determines the large-scale curvature of space, see here. Right now the density doesn't differ measurably from the "critical" density so space is flat on large scales, but if you suddenly removed most of the non-dark matter, it would become measurably hyperbolic. I can't imagine how an instant transition from one large-scale geom. to another would even work, how would points in flat space map to points in hyperbolic space? – Hypnosifl Sep 06 '19 at 14:15
  • @Hypnosifl Why would dark matter disperse? Isn't gravity the one thing that definately interacts with it? – Michael Richardson Sep 06 '19 at 14:21
  • @Michael Richardson - From what I understand, dark matter can clump somewhat due to gravity, but a cloud of dark matter will only collapse to the point where it becomes virialized, after that any further collapse would result in a decrease in entropy so it can't happen spontaneously. Normal matter can give off radiation and collapse to a hotter, denser state without decreasing entropy...see my answer here for more. – Hypnosifl Sep 06 '19 at 15:09
  • How are you getting rid of this mass? It can't just be 'wiped from existence' in any science based universe. It would have to be converted to energy, which most likely would destroy us. – Kolobdoc Sep 06 '19 at 14:31
  • This is essentially the Big Rip. – Spencer Sep 06 '19 at 19:43
  • Does energy count as mass? – Nonny Moose Sep 07 '19 at 18:08

12 Answers12

86

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.

abestrange
  • 5,598
  • 2
  • 14
  • 24
  • 6
    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 06 '19 at 14:09
  • 1
    @DarrelHoffman Most of the other means are also based on isotope decays though, like O18, so we would also lose them. – Alessandro Sep 06 '19 at 15:00
  • 3
    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 06 '19 at 23:13
  • 3
    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 07 '19 at 01:07
  • 2
    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 07 '19 at 04:22
  • 1
    Exactly. It's already interesting. – Lightness Races in Orbit Sep 07 '19 at 20:49
  • I have a feeling that a universe only populated by the mass of the solar system would be... weird in all aspects. The universe would per definition be the solar system. The density of the solar system is much greater than the universe, so a universe that dense would be interesting - in terms of curvature. – Stian Sep 08 '19 at 07:35
72

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".

Nuclear Hoagie
  • 14,068
  • 2
  • 32
  • 53
  • Good point, I'll reword the question—forgot to think about distance and speed of light, thanks for pointing it out – minseong Sep 05 '19 at 20:04
  • 1
    The re-phrased question is what's interesting to me, can you answer that instead? The current answer is not an answer to the question. – minseong Sep 05 '19 at 22:08
  • Example: The light reaching us from rather ordinary galaxy NGC907 started it's journey over a million years before the dinosaurs died off, and many millions of years before our ancestors began climbing in trees. – user535733 Sep 06 '19 at 02:34
  • 1
    Depending on the definition of "immediate" - even if the Sun disappeared, we won't notice anything at all for the entire ~8 minutes! (and I mean - not just us humans, but also the Earth - because gravitation propagates at the speed of light, so our planet would "think" the Sun is still there for those 8 minutes) – Alma Do Sep 06 '19 at 07:47
  • 16
    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 Sep 06 '19 at 10:01
  • 2
    Just the effect of stars disappearing according to their distance (Alpha Centauri first in 4 years, but then most of the constellations and bright stars gone in a century, and mostly dark sky 500 years later) would make such a cool setting for a novel! – Tomáš Kafka Sep 06 '19 at 10:33
  • 6
    @theonlygusti Changing a question entirely after an answer has been given (with high upvotes) is very bad form across all SE sites. – Cloud Sep 06 '19 at 11:53
  • You could imagine the "eating up" of everything outside the solar system starting at some radius out from the sun and moving outward, blocking/reflecting/trapping light as it goes. In that case the sky would go dark nearly instantly rather than stars disappearing over long time spans according to their distance, but there would be no observable difference from our side between their light just having been blocked, and them having ceased to exist, until the time span corresponding to their distance had elapsed. – R.. GitHub STOP HELPING ICE Sep 06 '19 at 12:42
  • 6
    @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) – minseong Sep 06 '19 at 14:52
  • @R.. You said "moving outward" instead of "moving inward." I assume it was accidental. For everything to appear to have disappeared all at once, it would have to start farther away and work its way toward us. I.e: if it started approximately 100,000 light years away and worked toward us at light speed, then all of Milky Way would appear to vanish at the same time. – Loduwijk Sep 06 '19 at 17:03
  • 12
    @theonlygusti This answer has no nit-picking in it, and it certainly does contain interesting insights. It is true that it does not answer the primary part of your question about dangerous effects and if we would die, but your other comments about this answer are not accurate. – Loduwijk Sep 06 '19 at 17:05
  • @Loduwijk: No, I meant what I said. Instantly materialize a spherical black wall around the solar system, then start deleting everything outside it in whatever order you like; working outward is fine but it doesn't matter. Your variant works too; it's just different from what I said and starts in the distant past. – R.. GitHub STOP HELPING ICE Sep 06 '19 at 17:13
  • 3
    Ah, I think I understand now. Because you're suggesting everything within a certain volume it "eaten," including the light, yes? So it would all vanish from our point of view even if still there because the light no longer reaches us. And, in that case, the entire rest of the universe could even remain there and not vanish at all as long as some magic barrier blocks everything even light and gravity... we wouldn't know the difference, and from our point of view it would be equivalent. @R.. – Loduwijk Sep 06 '19 at 17:30
  • @Loduwijk: Yep, exactly. Interaction with gravitational waves might be troublesome though. I haven't thought that throught yet. Shouldn't matter if the "wall" can "eat" them too though. – R.. GitHub STOP HELPING ICE Sep 06 '19 at 17:32
  • 8
    @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 Hoagie Sep 06 '19 at 18:36
  • 2
    But would the disappearing matter include photons en route from distant stars? – Davislor Sep 07 '19 at 04:35
43

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?

Please be.

Mindwin Remember Monica
  • 14,591
  • 6
  • 50
  • 103
19

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.

Cort Ammon
  • 132,031
  • 20
  • 258
  • 452
  • 1
    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 06 '19 at 04:04
  • 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 06 '19 at 05:05
  • 1
    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 06 '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 Sep 06 '19 at 14:43
  • Agreed. Cubed grow faster than squared. – Taemyr Sep 06 '19 at 15:50
  • Q: Why didn’t it eat Earth? A: A good farmer would never eats her/his seed corn. – SRM Sep 08 '19 at 02:20
12

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!

Roland Heath
  • 491
  • 2
  • 6
8

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.

Separatrix
  • 117,733
  • 38
  • 261
  • 445
  • 3
    Cheeky. Almost certainly not what OP meant, but this was funny. My +1 is entirely for making me laugh. – Loduwijk Sep 06 '19 at 17:15
7

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.

Mike Scott
  • 20,186
  • 3
  • 41
  • 81
  • 4
    "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 06 '19 at 18:56
  • 1
    @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 06 '19 at 22:41
  • 1
    @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 06 '19 at 23:12
  • 1
    @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 07 '19 at 20:51
4

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.

Juraj
  • 2,889
  • 7
  • 7
  • Mmm this is my first inclination also. Do you have citations/proof as to why though? – minseong Sep 05 '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 07 '19 at 20:06
4

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.

Radovan Garabík
  • 14,297
  • 2
  • 25
  • 55
  • This is an important point (change of G, change of momenta) that the other answers missed. – amI Sep 08 '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 08 '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 08 '19 at 21:50
2

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!

David H Parry
  • 205
  • 1
  • 3
2

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.

[Edit] 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

Jim
  • 155
  • 3
  • 2
    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 06 '19 at 17:57
  • 1
    @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 07 '19 at 02:00
  • Dubukay, It's actually worse than I postulated, as shown in my edit to my answer. – Jim Sep 08 '19 at 14:01
1

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.

EvilSnack
  • 2,398
  • 9
  • 14