# What if our solar system were isolated? **URL:** \ **Category:** Factual Questions\ **Created:** [March 18, 2017, 2:42am UTC](https://boards.straightdope.com/t/what-if-our-solar-system-were-isolated/782462 "2017-03-18T02:42:50Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![tullsterx](https://avatars.discourse-cdn.com/v4/letter/t/e9bcb4/32.png) [@tullsterx](https://boards.straightdope.com/u/tullsterx)\ **Post date:** [March 18, 2017, 2:42am UTC](https://boards.straightdope.com/t/what-if-our-solar-system-were-isolated/782462/1 "2017-03-18T02:42:50Z")
If the rest of the universe. . . disappeared FOR SOME UNKNOWN REASON. Would we feel the effects? If there were no more stars, how would it affect our solar system? ---
**Author:** ![Little\_Nemo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/little_nemo/32/3120_2.png) [@Little\_Nemo](https://boards.straightdope.com/u/Little_Nemo)\ **Post date:** [March 18, 2017, 2:44am UTC](https://boards.straightdope.com/t/what-if-our-solar-system-were-isolated/782462/2 "2017-03-18T02:44:45Z")
We’d lose a lot of our ability to navigate without instruments. ---
**Author:** ![Debillw3](https://avatars.discourse-cdn.com/v4/letter/d/3bc359/32.png) [@Debillw3](https://boards.straightdope.com/u/Debillw3)\ **Post date:** [March 18, 2017, 2:51am UTC](https://boards.straightdope.com/t/what-if-our-solar-system-were-isolated/782462/3 "2017-03-18T02:51:30Z")
It’d ultimately depend on what “disappeared” means. Put simply, if the rest of the galaxy disappeared, leaving just our solar system, the effect would be comparable to what would happen if the rest of the solar system (including the Earth) disappeared, leaving just the Moon. Just as the Moon orbits the Earth and the Earth orbits the Sun, the Sun orbits within the galaxy. It’s an oversimplification, but I’m sure you can understand the havoc that would play with regard to the orbital mechanics. The extent of that havoc would be determined by where it went and how it got there. ---
**Author:** ![tullsterx](https://avatars.discourse-cdn.com/v4/letter/t/e9bcb4/32.png) [@tullsterx](https://boards.straightdope.com/u/tullsterx)\ **Post date:** [March 18, 2017, 3:06am UTC](https://boards.straightdope.com/t/what-if-our-solar-system-were-isolated/782462/4 "2017-03-18T03:06:57Z")
> [@Debillw3](#): > > It’d ultimately depend on what “disappeared” means. > > Put simply, if the rest of the galaxy disappeared, leaving just our solar system, the effect would be comparable to what would happen if the rest of the solar system (including the Earth) disappeared, leaving just the Moon. > > Just as the Moon orbits the Earth and the Earth orbits the Sun, the Sun orbits within the galaxy. > > It’s an oversimplification, but I’m sure you can understand the havoc that would play with regard to the orbital mechanics. The extent of that havoc would be determined by where it went and how it got there. Well, yeah, but how would that take? I mean, we’re currently on the long highway-to-hell with our Sun. Seems like it could take a while to feel those effects. In my scenario we still have mass and gravity and physics and all of the principals that make our solar system “function.” ---
**Author:** ![Debillw3](https://avatars.discourse-cdn.com/v4/letter/d/3bc359/32.png) [@Debillw3](https://boards.straightdope.com/u/Debillw3)\ **Post date:** [March 18, 2017, 3:15am UTC](https://boards.straightdope.com/t/what-if-our-solar-system-were-isolated/782462/5 "2017-03-18T03:15:06Z")
> [@tullsterx](#): > > Well, yeah, but how would that take? I mean, we’re currently on the long highway-to-hell with our Sun. Seems like it could take a while to feel those effects. In my scenario we still have mass and gravity and physics and all of the principals that make our solar system “function.” But from your post, we aren’t talking about a gradual thing–we’re talking about something that just suddenly disappears. The Sun (and, likewise, the solar system in general) orbits a center of gravity within the galaxy. If that were to suddenly disappear, it can be comparable to the Earth disappearing on the Moon. The solar system, though a system in & of itself, is also part of a larger system within the galaxy, which is, itself, part of a larger system. While the solar system would likely continue to function within itself, the larger systems that the solar system is part of would cease to exist, which wouldn’t be good. As I said, this is an oversimplification, but I think it works for the purposes of discussion. ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [March 18, 2017, 3:50am UTC](https://boards.straightdope.com/t/what-if-our-solar-system-were-isolated/782462/6 "2017-03-18T03:50:57Z")
If Mach’s principle is correct, losing the rest of the universe might really screw up inertia. As in, it might take on a really small coupling constant or disappear completely. Mach’s principle is the idea that inertia (linear and rotational) only come about because of the global distribution of matter–that somehow they influence spacetime in a way that gives us inertia. Take away the matter and this influence goes away, along with inertia itself (there might be some left over from local influences, but not a lot). Mach’s principle is probably wrong, and certainly unproven. But it also hasn’t been ruled out completely. ---
**Author:** ![buddha\_david](https://avatars.discourse-cdn.com/v4/letter/b/ee7513/32.png) [@buddha\_david](https://boards.straightdope.com/u/buddha_david)\ **Post date:** [March 18, 2017, 3:57am UTC](https://boards.straightdope.com/t/what-if-our-solar-system-were-isolated/782462/7 "2017-03-18T03:57:18Z")
When it comes time to evacuate the solar system in 4½ billion years as the sun goes nova, our options will be severely limited. ---
**Author:** ![eschereal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eschereal/32/18939_2.png) [@eschereal](https://boards.straightdope.com/u/eschereal)\ **Post date:** [March 18, 2017, 4:00am UTC](https://boards.straightdope.com/t/what-if-our-solar-system-were-isolated/782462/8 "2017-03-18T04:00:24Z")
The earth would have a lot less boron. ---
**Author:** ![markn\_1](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@markn\_1](https://boards.straightdope.com/u/markn_1)\ **Post date:** [March 18, 2017, 4:54am UTC](https://boards.straightdope.com/t/what-if-our-solar-system-were-isolated/782462/9 "2017-03-18T04:54:53Z")
> [@Debillw3](#): > > Just as the Moon orbits the Earth and the Earth orbits the Sun, the Sun orbits within the galaxy. > > It’s an oversimplification, but I’m sure you can understand the havoc that would play with regard to the orbital mechanics. You’re suggesting that the orbital mechanics of the solar system are affected by the gravitation of the rest of the galaxy? This seems very unlikely to me. I don’t think the orbits of the planets would be affected at all if the rest of the galaxy disappeared. As a first order approximation, based on the fact that the solar system orbits the galactic center every 230 million years, and is 27,000 light years from the center, I use Kepler’s Third Law to calculate that the galaxy as a whole exerts a gravitational force equivalent to a mass of 3x10[sup]40[/sup] kilograms at the distance of the galactic center. (Details of calculation on request.) This is equivalent to a mass of 1x10[sup]22[/sup] kg at one astronomical unit. In other words, it’s the same as the pull of a body 1/7 the size of the moon at the distance of the sun. This is very small. Furthermore, it’s essentially uniform across the whole solar system. I don’t think it affects the planets’ orbits in any significant way. ---
**Author:** ![Debillw3](https://avatars.discourse-cdn.com/v4/letter/d/3bc359/32.png) [@Debillw3](https://boards.straightdope.com/u/Debillw3)\ **Post date:** [March 18, 2017, 5:11am UTC](https://boards.straightdope.com/t/what-if-our-solar-system-were-isolated/782462/10 "2017-03-18T05:11:54Z")
> [@markn\_1](#): > > You’re suggesting that the orbital mechanics of the solar system are affected by the gravitation of the rest of the galaxy? This seems very unlikely to me. I don’t think the orbits of the planets would be affected at all if the rest of the galaxy disappeared. No, I’m suggesting that the orbital mechanics of the solar system as a system (not the individual entities that make it up themselves) are affected by the gravitation of the galaxy–which is why it orbits in the first place. I’m then further suggesting that a sudden cessation of those forces would have an effect on the solar system as a system. The extent of that effect, as I further suggested, would have a great deal to do with the reason for that cessation. Obviously something like a black hole would have a greater impact than a sudden “poof” (which could well be negligible). As I acknowledged, my analogy was an oversimplification, as I didn’t feel like doing the math (kudos to you on that, by the way) or getting into the nitty gritty of how orbits actually work, but I felt it worked as a sample what type of thing we’re talking about. I never intended to discuss the effect (which, again, could be negligible) on the Earth itself, as that would depend on a number of factors not specified, but, rather, the solar system as a systematic whole. ---
**Author:** ![mikecurtis](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mikecurtis/32/3284_2.png) [@mikecurtis](https://boards.straightdope.com/u/mikecurtis)\ **Post date:** [March 18, 2017, 5:32am UTC](https://boards.straightdope.com/t/what-if-our-solar-system-were-isolated/782462/11 "2017-03-18T05:32:04Z")
> [@tullsterx](#): > > Well, yeah, but how would that take? I mean, we’re currently on the long highway-to-hell with our Sun. Seems like it could take a while to feel those effects. In my scenario we still have mass and gravity and physics and all of the principals that make our solar system “function.” well, if you still had the entire space/time of the universe, since gravity “travels” at c; we probably wouldnt even notice for over 4 yrs, as thats how far the closest object of any significance is. and it would take another 27,000 yrs for all of the gravitational effects of our own galaxy to disappear. then another 2.5 million yrs for the gravity from andromeda to start to disappear…etc. i’m not sure what the effects would be, but it would happen very slowly (in human terms) mc ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [March 18, 2017, 6:10am UTC](https://boards.straightdope.com/t/what-if-our-solar-system-were-isolated/782462/12 "2017-03-18T06:10:34Z")
> [@mikecurtis](#): > > well, if you still had the entire space/time of the universe, since gravity “travels” at c; we probably wouldnt even notice for over 4 yrs, as thats how far the closest object of any significance is. and it would take another 27,000 yrs for all of the gravitational effects of our own galaxy to disappear. then another 2.5 million yrs for the gravity from andromeda to start to disappear…etc. i’m not sure what the effects would be, but it would happen very slowly (in human terms) > > mc Stars would wink out one-by-one … that would be cool … ---
**Author:** ![Derleth](https://avatars.discourse-cdn.com/v4/letter/d/b9e5f3/32.png) [@Derleth](https://boards.straightdope.com/u/Derleth)\ **Post date:** [March 18, 2017, 7:14am UTC](https://boards.straightdope.com/t/what-if-our-solar-system-were-isolated/782462/13 "2017-03-18T07:14:02Z")
> [@Dr.Strangelove](#): > > If Mach’s principle is correct, losing the rest of the universe might really screw up inertia. As in, it might take on a really small coupling constant or disappear completely. > > Mach’s principle is the idea that inertia (linear and rotational) only come about because of the global distribution of matter–that somehow they influence spacetime in a way that gives us inertia. Take away the matter and this influence goes away, along with inertia itself (there might be some left over from local influences, but not a lot). > > Mach’s principle is probably wrong, and certainly unproven. But it also hasn’t been ruled out completely. [Here’s a more mathematical development of the concept, with some interesting analogies to electromagnetism](https://physics.fullerton.edu/~jimw/general/inertia/) not in the sense of _unifying_ EM and gravity, but in the sense of applying the same concepts and machinery to both: > [@](#): > > Now if gravity behaves like electromagnetism, we can simply hijack the mathematical formalism of electromagnetism in order to calculate gravitational effects. This isn’t always true. But for the simple case we’re going to consider it is. We look at a “test particle”, a massive object that’s so small that it doesn’t disturb any of the stuff it finds itself in. It’s located in a universe much like ours, but to keep things simple we assume that everything in the universe, other than the test particle, is smeared out smoothly throughout space. We now let our test particle move along a straight line in this stuff and ask: What is the force of gravity on the test particle due to the rest of the stuff? In general, both “gravito-electric” and “gravito-magnetic” fields, the gravitational counterparts of electric and magnetic fields, may act. In this case, however, the gravito-magnetic field itself doesn’t act, so we can ignore it. The reason why is that the rest of the stuff out there doesn’t “circulate”, so the “curl” of the vector potential vanishes. > > [snip] > > Well, all of this is fine, but maybe we don’t have to take the effects of gravito-magnetism and the vector potential seriously. Perhaps they’re so minute they can be ignored. Turns out that that’s not true. As Ken Nordtvedt pointed out in 1988 [_International Journal of Theoretical Physics_, 27, 1395-1404], gravito-magnetic effects must be taken into account in even the simplest planetary orbit calculations. Only a moment’s reflection is needed to see that this must be right. From Newtonian mechanics we know that the gravitational force acting on a planet must act along the instantaneous line of centers of the planet and the Sun if an elliptical orbit is to be recovered. (That is, the force exerted by the Sun must propagate to the planet instantaneously. This fact is the reason why Newtonian gravitation is called an “action-at-a-distance” force. Newton privately thought this preposterous; but he never found a way around it.) If relativity is right, then the gravito-electric field (i.e., Newtonian gravity) must propagate at the speed of light, and the corresponding gravitational force on the planet wouldn’t point along the instantaneous line of centers. So, if the gravito-magnetic contribution to the total force weren’t included, the force of the Sun on the Earth, for example, would point in the wrong direction and its orbit wouldn’t be elliptical. (Nordtvedt arrives at this conclusion by a variant of this argument. He shows that the motion of a test particle around the Sun is elliptical for an observer at rest with respect to the Sun. In this frame of reference the field is stationary and everywhere points toward the Sun at all times, so the force is always along the instantaneous line of centers. If the observer moves with respect to the Sun [for example, with the planet], however, and doesn’t take into account the gravito-magnetic vector potential, the predicted orbit “blows up”. [This example is a neat illustration of the fact that “coordinate transformations” in general relativity theory are equivalent to “gauge” transformations in electrodynamics. The observer at rest with respect to the Sun is effectively in the Coulomb gauge, and the one moving with the planet in the Lorentz gauge.]) This web page is from the Stupid Age of Text Encoding, so all the inline equations are images, and sometimes hard to read. I can transcribe into a PDF form if anyone really has a problem with them. ---
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [March 18, 2017, 10:49am UTC](https://boards.straightdope.com/t/what-if-our-solar-system-were-isolated/782462/14 "2017-03-18T10:49:18Z")
Something similar might actually happen in a billion years or so. The Andromeda galaxy will collide with the Milky Way and the Sun with the solar system could be ejected as a result. ---
**Author:** ![John\_DiFool](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_difool/32/19543_2.png) [@John\_DiFool](https://boards.straightdope.com/u/John_DiFool)\ **Post date:** [March 18, 2017, 11:56am UTC](https://boards.straightdope.com/t/what-if-our-solar-system-were-isolated/782462/15 "2017-03-18T11:56:07Z")
I heard something similar will happen in 40-50 billion years, thanks to expansion (all other stars and objects will recede beyond our visual horizon). ---
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [March 18, 2017, 12:47pm UTC](https://boards.straightdope.com/t/what-if-our-solar-system-were-isolated/782462/16 "2017-03-18T12:47:37Z")
> [@John\_DiFool](#): > > I heard something similar will happen in 40-50 billion years, thanks to expansion (all other stars and objects will recede beyond our visual horizon). You may be thinking of Wikipedia’s [Timeline of the Far Future](https://en.wikipedia.org/wiki/Timeline_of_the_far_future), wherein that figure refers to galaxies beyond the Local Group. The timescale for that particular event is given as 100 billion years, and the Local Group will coalesce into a single galaxy in around 450 billion years. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [March 18, 2017, 12:51pm UTC](https://boards.straightdope.com/t/what-if-our-solar-system-were-isolated/782462/17 "2017-03-18T12:51:05Z")
The rest of the Galaxy disappearing would wreak havoc with the orbital mechanics _of the Galaxy_. It would have almost no effect on the orbital mechanics _of the Solar System_. The Sun with its entourage of planets would fly off on a tangent to its current path, but there’s no reason we would care about that. > [@](#): > > Quoth **John DiFool** : > > I heard something similar will happen in 40-50 billion years, thanks to expansion (all other stars and objects will recede beyond our visual horizon). Not under most models of cosmological expansion. Objects as small as galaxies or even galaxy clusters have more than enough gravity to hold themselves together against the cosmological expansion. The only way to rip apart a galaxy would be if the dark energy dramatically increases in strength. While there are some plausible models that predict that, they usually go much further: Not long after the point where galaxies would be dispersed, so would solar systems, planets, and individual atoms. ---
**Author:** ![rbroome](https://avatars.discourse-cdn.com/v4/letter/r/838e76/32.png) [@rbroome](https://boards.straightdope.com/u/rbroome)\ **Post date:** [March 18, 2017, 1:43pm UTC](https://boards.straightdope.com/t/what-if-our-solar-system-were-isolated/782462/18 "2017-03-18T13:43:10Z")
> [@Derleth](#): > > [Here’s a more mathematical development of the concept, with some interesting analogies to electromagnetism](https://physics.fullerton.edu/~jimw/general/inertia/) not in the sense of _unifying_ EM and gravity, but in the sense of applying the same concepts and machinery to both:This web page is from the Stupid Age of Text Encoding, so all the inline equations are images, and sometimes hard to read. I can transcribe into a PDF form if anyone really has a problem with them. Thanks for the link! fascinating read. ---
**Author:** ![Hari\_Seldon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hari_seldon/32/5173_2.png) [@Hari\_Seldon](https://boards.straightdope.com/u/Hari_Seldon)\ **Post date:** [March 18, 2017, 6:00pm UTC](https://boards.straightdope.com/t/what-if-our-solar-system-were-isolated/782462/19 "2017-03-18T18:00:30Z")
A lot of speculation for GQ, but my first (and last impression) is Chronos’s. I cannot see why the gravity of the rest of the universe would have any discernible influence on the solar system. Unless Mach’s principle is correct. ---
**Author:** ![joema](https://avatars.discourse-cdn.com/v4/letter/j/a9adbd/32.png) [@joema](https://boards.straightdope.com/u/joema)\ **Post date:** [March 18, 2017, 7:36pm UTC](https://boards.straightdope.com/t/what-if-our-solar-system-were-isolated/782462/20 "2017-03-18T19:36:23Z")
> [@Debillw3](#): > > No, I’m suggesting that the orbital mechanics of the solar system as a system (not the individual entities that make it up themselves) are affected by the gravitation of the galaxy–which is why it orbits in the first place… If the rest of the universe vanished, the practical effect on our solar system would be microscopic. We know this for two reasons: (1) Even though gravity has infinite range, it drops off in inverse proportion to the square of distance. E.g, double the distance and gravity is 1/4 as much, triple the distance and it’s 1/9th as much quadruple the distance and it’s 1/16th as much, etc. The inverse square law coupled with the gigantic interstellar and intergalactic distances means the gravitational effect of the rest of the universe on our solar system is very small. We can easily calculate this using the sun which contains 99.86% of the mass of the entire solar system. The sun’s mass is 1.99E30 kg. The combined mass of the closest star system, Alpha Centauri, is 2.1 times this, or 4.18E30 kg. The physical force between the entire Alpha Centauri star system and the sun is given from the equation for gravitational attraction. Fortunately there’s an on-line calculator which allows entry in solar masses and light years: [Newton's Law Gravity Equations Formulas Calculator - Force Between Objects](http://www.ajdesigner.com/phpgravity/newtons_law_gravity_equation_force.php#ajscroll) The resultant force is 6.45E17 newtons or 6.58E13 metric tons of force. This sounds like a lot but it’s roughly the water mass of the Caspian Sea: [Google Maps](https://goo.gl/maps/aMazWBGeoX12) Relative to the mass of the sun (99.86% of the solar system), this is microscopic. We can even calculate how much the presence or absence of this force would accelerate the sun from F=ma. The sun’s mass is 1.99E30 kg. This would accelerate the sun (or our solar system) at 3.24E-13 meters per sec^2, or less than the diameter of a single hydrogen atom per second. The effect would be so slight it could not be measured with the most sensitive instruments. And that is from the _closest_ star system. Due to the gravitational inverse square law, more distant bodies (even if far more massive) would have even less effect. (2) Gravity moves at the speed of light. Most of the mass of our galaxy (much less the universe) is vastly far away. Even if it vanished instantly, it would take eons of time for most of that tiny force difference to reach earth. [Next page](https://boards.straightdope.com/t/what-if-our-solar-system-were-isolated/782462.md?page=2)