Around 100 million years ago, the Solar System was instantaneously encased in a massless, magical sphere centered about the Sun. The boundary is about 10,000 AU (.158 ly) in radius and behaves abnormally: matter and energy from outside the boundary may enter into the Solar System unaffected, while matter and energy trying to exit is essentially erased (if you were to reach your hand beyond the boundary, you'd retract a gory stump).

Question: Assuming that everything else proceeded as usual with the dinosaurs' extinction and humanity's uprising... With such a structure just thrown up like that in the distant past, could there be any astronomically glaring signs or repercussions of it that would tip us (present-day "modern" astronomers with our space telescopes and space probes) off to its existence?

I am searching for any consequential phenomena that results from the boundary's introduction that also signals to modern astronomers that something is at least not right with outer space at that distance (keep in mind, the alien sphere itself is massless, essentially transparent, and not a blackbody (matter and energy erased is not absorbed and re-emitted)). I feel like this question is better posed under the yes-or-no format. So, if the side-effects of such an alien boundary are too little for modern (can be any era up to modern, really) astronomers to detect, or there are no side-effects, then showing that with a science-based analysis constitutes a "no" answer. Showing that some form of resultant phenomena exists that also falls under astronomers' threshold of detection constitutes a "yes" answer.

Potential pointers:

(These are just some things I've contemplated during my research.)

Of course, astronomers won't be able to see the boundary directly, as light from the outside simply passes through it unaffected in any way, though, they may be able to infer its existence somehow.

Not many striking things seem to orbit 10,000 AU from the Sun. The farthest object we've currently discovered, Farout, orbits about 120 AU out. The Oort Cloud, however, is a different story. The Oort Cloud is a hypothetical structure which defines the Sun's cosmographical Hill sphere, the region within which objects have the potential to orbit the Sun. Its radius ranges from 2,000 to 200,000 AU, so the alien boundary would have intersected and partitioned it. 100 million years is quite a few Earth-orbits, even for those super-distant objects with multi-thousand-year years, so perhaps modern astronomers would see a deficit of long-period comets with aphelia greater than 10,000 AU. (Perhaps a detectable discrepancy?)

Scholz's Star, WISE designation WISE 0720−0846, is a red dwarf that has been modeled to have passed through the Oort Cloud of the Solar System at a distance of around 52,000 AU, around 70,000 years ago. Similarly, Gliese 710 or HIP 89825 is predicted to have a close approach with the Sun at a distance as near as 13,300 AU (just outside the alien boundary) within the next 15 million years. The Wiki's source states that there is a 1 in 10,000 chance that the star penetrates less than 1,000 AU, significantly perturbing Kuiper belt objects. According to this paper, stellar approaches closer than around 50,000 AU happen about every 9 million years, with probabilities of even closer approaches.

Exoasteroids and exocomets, such as 'Oumuamua, will have entered the Solar System, though, in the ~1,800 years it will take to reach the boundary (1.496e+12 km / 26.3 km-per-sec / 60 seconds-per-min / 60 minutes-per-hour / 24 hours-per-day / 365.25 days-per-year = 1,802 years), we won't see it or others like it leave. (We may, however, see captured exosolar bodies.) Any future endeavors to send probes or spacecraft to other star systems, like Breakthrough Starshot or Project Daedalus, will not work because they simply cannot penetrate the boundary, so, after the first few of these attempts, we will begin to at least suspect something.

Physical & Quantum mechanical aspects of matter-boundary interaction:

The alien boundary has 1-dimensional thickness and is mathematically smooth. It is massless. Its mathematical center is fixated on the exact gravitational barycenter of all the matter within it. Gravitational propagation is allowed through the barrier (though the boundary is unaffected by external gravitation), though not out of it. Because of this, the Solar System continues its orbit about the Milky Way (with the distinction that the Sun and all Solar System matter does not influence the galactic barycenter) and as mentioned the boundary tracks the exact barycenter within.

Quantum tunneling to exit the boundary is impossible. Quantum tunneling in is okay. Entangled particles entering remain entangled to their counterparts, even if exterior to the boundary. Atoms and molecules are shaved off at the quark level and the boundary interacts only with particles that interact with it. (One can asymptomatically approach the boundary, but not cross it.) (Particles cannot move at more than a Planck length in a Planck time.) For instance, a molecule of diatomic oxygen trying to exit: electrons in the electron cloud are first to go, they are known with exact certainty; then, as the atom travels farther, the intermittent quarks and mediating gluons within the nucleus' protons and neutrons are done away with (the traversing atom would become unstable and nuclear forces would dominate it); after the first electrons vanish, the chemical covalent bond is broken (if there is excess energy in the other atom, it may be released Solar System-ward); the process continues for the next atom of oxygen, should it continue to maintain the velocity needed to cross the boundary. No energy from the destruction of particles themselves is released (the particles are not converted to energy that is released). It is a similar story for photons and all other irreducible particles. The clean and instantaneous deletion of matter would result in gravitational waves.

  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$
    – L.Dutch
    Mar 12, 2019 at 16:46
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    $\begingroup$ Jupiter may save you. See page 274 on books.google.co.nz/… $\endgroup$ Mar 12, 2019 at 21:56
  • $\begingroup$ The shell already exists - see addition to my answer. $\endgroup$ Mar 12, 2019 at 22:08
  • $\begingroup$ If nothing escapes from inside the sphere, then the Outsiders cannot observe Inside. In which case, how are they maintaining the centering of the sphere on the sun. I can see two possibilities. (1) They are 'steering' from Outside based on the course they plotted for the Sun before locking it up or (2) the sphere is 'steered' from inside. Anything responsible or related to the sphere that is inside could be a giveaway..(I'm assuming the massless sphere wouldn't 'naturally' move at the same speed/direction as the solar system). $\endgroup$
    – Gary Myers
    Mar 13, 2019 at 3:34
  • $\begingroup$ @GaryMyers For all intents and purposes, the boundary is fully autonomous in its abilities. $\endgroup$
    – BMF
    Mar 13, 2019 at 11:44

8 Answers 8


The local interstellar cloud (LIC) has a temperature of 7000 K and density of 0.3 atoms/cc.

RMS velocity is thus $V_{rms} = \frac{3RT}{M}^\frac{1}{2}$, or 13 km/s, for Hydrogen.

At 0.3 atoms/cm^3 we have about 4 billion atoms crossing each cm^2 of the barrier every second (in each direction).

Most of the atoms are hydrogen atoms. Outgoing hydrogen atoms experience a moment when the proton is torn apart; one of the quarks is destroyed, while the others remain.

As 99%+ of the mass of a hydrogen atom is in its binding energy, and the two remaining quarks are no longer chromatically balanced, this will generate an insanely powerful explosion (at microscopic scales) as they jet apart trying to ground themselves chromatically.

Atoms entering will also experience this, as once one quark crosses the gluon exchange with the quarks outside no longer occurs. Both the inner and outer quarks will go haywire, trying to chromatically ground themselves and finding no partners.

This process will occur much, much faster than the quarks cross the barrier; the energy scales of the hydrogen moving at 13 km/s are insanely lower than the energy scales binding the nucleus together.

While high energy density, the total energy will also scale with the thinness of the interstellar medium. Each hydrogen atom weighs $1.67 x 10^{-27} kg$. 9 billion of these has a weight of about $10^{-17} kg$, which when converted to energy is about 0.9 J.

So the barrier emits on the order of 1 J per second per cm^2.

This surface has a temperature of 374 C or 647 K. Far hotter than the CMB cosmic microwave background radiation.

Now, emissions scale with the 4th power of temperature. Solving for 1K (where it might be cold enough not to be noticed?) we get 5 * 10^-12 W/cm^2; you'd have to avoid all but 1 part in 10^12 of this proton disintegration from emitting energy.

The basic problem is that discontinuities are explosive in physics.

It probably will even be worse than this, because Hawking radiation scales with the sharpness of the event horizon; your event horizon is infinitely sharp, so you'll probably get something at least approximeting infinite energy emission from the surface. But that math is harder, while quark binding energy math is easy, and sufficient to make the barrier really obvious.

This also neglects that almost certainly lower-order contribution of destroying the electron first. An atom is electrically neutral; destroying the electron first makes it positive, then the proton goes and it is negative.

In the period between the first and second, you have a changing electromagnetic field. Such changes are experienced as photons.

The frequency of said photons will be distributed based on the time difference between the electron and proton being destroyed, aka 5.29177 x 10^-11 meters. Photons of that wavelength are called gamma rays.

  • $\begingroup$ I suppose that this is the be-all-end-all answer. In the spirit of the original question, things crossing inward were to remain intact. Though when I attempted a quantum mechanical interpretation of those processes, I shattered that magical property—and it makes sense that that be shattered. Your answer is very well thought out, thank you! $\endgroup$
    – BMF
    Mar 12, 2019 at 20:16
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    $\begingroup$ This is the direction I was heading in, when I asked for clarification on the atomic and quantum level, A barrier with thickness would have allowed for a transition area between the molecule entry and exit boundary, where molecules could selectively be destroyed or allowed to pass in their entirety. I assume the gamma radiation or whatever would be distributed across the entire sphere. It begs the next question be asked: when could the people of earth reasonably establish that this radiation was coming from the sphere, and not from deep space? How could they tell? It has no point origin. $\endgroup$ Mar 13, 2019 at 0:29
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    $\begingroup$ But I still have a question about the electron. Not being made of any smaller particle, could the electron be slowly shaved away? What would that look like? Or would the entire electron disappear when any part of it hit the barrier? Infinitely hard rock meets irresistible shearing force. $\endgroup$ Mar 13, 2019 at 0:36
  • $\begingroup$ Would larger objects create enough of a energy release to be noticeable, or would they be launched away from the barrier before it got that large? $\endgroup$
    – jaxad0127
    Mar 13, 2019 at 7:12
  • $\begingroup$ @jaxad0127 I imagine the latter. A big enough object might absorb enough energy to fully vaporize before crossing the boundary completely. $\endgroup$
    – BMF
    Mar 13, 2019 at 11:48

Yes. Astronomers could see the barrier directly because the barrier would emit Hawking radiation.

Pairs of particles and antiparticles are constantly appearing and disappearing all over the place throughout space. This is called quantum fluctuation. It's usually hard to detect quantum fluctuation because the particle pairs annihilate each other soon after forming. If one of them is is removed by, say, falling into a black hole or getting annihilated by your barrier, and the sister particle doesn't get annihilated then the sister particle gets to do something else like becoming visible to astronomers. In the case of black holes these escaping particles are called Hawking radiation.

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    $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$
    – L.Dutch
    Mar 12, 2019 at 12:43
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    $\begingroup$ Can you calculate the amount of Hawking Radiation it would emit? $\endgroup$
    – Yakk
    Mar 12, 2019 at 18:51
  • $\begingroup$ If this is all that they'd ever known and seen, being everywhere that astronomers look, how long would it take to figure this out? $\endgroup$
    – RonJohn
    Mar 12, 2019 at 22:21
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    $\begingroup$ What would differentiate this from the cosmic background radiation? $\endgroup$
    – jpmc26
    Mar 12, 2019 at 23:03
  • $\begingroup$ @RonJohn Radiation from outside still travels in, so if this Hawking radiation does manage to wash out stars, then astronomers likely won't suspect anything until the next biggest supernova. $\endgroup$
    – BMF
    Mar 13, 2019 at 11:46

You'll have a statistical bias in orbital shapes and properties.

Any comets or other bodies which are gravitationally trapped by Sol and which cross the barrier 'going out' will vanish. Overall distributions of body energies will be skewed even for bodies that do not ever enter the inner system. .

Bodies which travel into the inner system and out to near the barrier will have a sharp limit to their energies. We may not currently analyse comet energies (or may) but a sharp truncation of the tail is an effect waiting to be noticed.

Jupiter may "save" you. Peturbation of cometary orbits by Jupiter is significant and while the skew in a known orbit can be measured, it may be that the magnitude of the Jupiter effect is such that it swamps the statistical variations caused by the 'cosmic vacuum cleaner'. Page 274 on in the book preview of "From Ordered To Chaotic Motion In Celestial Mechanics" may be useful.


The 'shell' already exists

A "cometary fading effect" that operates much as you have described already exists. While 'we' have detected it, the mechanism is unknowm.

See section 2.3 of this book preview from "Comets II".

Next question please.

  • $\begingroup$ Statistical bias is a good point, but may not result in a direct inference. Worry not! I'm not keeping blind eyes on answers which dare to speculate that modern astronomers may not detect such a structure, contrary to what others may believe. Great answer! Can you elaborate on the last point about the truncation of cometary tails? $\endgroup$
    – BMF
    Mar 12, 2019 at 12:39
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    $\begingroup$ @BMF Not the tail of the Comet, rather the tail of the Orbital Distribution. Measuring how fast a Comet approaches the Sun allows you to calculate how far out its orbit goes. Unrestricted, you would expect this to form a Bell Curve - however, if this has a sudden drop to 0 from one point (i.e. where the orbit would intersect the barrier) then it is an indication that there is some form of restriction - the tail of the Bell Curve has been truncated $\endgroup$ Mar 12, 2019 at 12:46
  • $\begingroup$ @Chronocidal I see. My first estimation of your answer was wrong. That is a good point, thank you! As an aside question, do you have any suggestions for where I might learn more about comets and their distributions? $\endgroup$
    – BMF
    Mar 12, 2019 at 13:30
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    $\begingroup$ @Chronocidal there won't be a drop to exactly 0, because Oort cloud continuously gets disturbed, generating new comets, but sharp drop in distribution nevertheless. $\endgroup$
    – Alexander
    Mar 12, 2019 at 16:22
  • $\begingroup$ If I understand what I've just read, then the cometary fade works somewhat in reverse to what we'd expect from the astronomic structure in question. Comets that are less tightly bound to the Solar System tend to group up asymptotically near E=0 (aphelia several hundred AU from the Sun) while the "fade" occurs when moving away from E=0 toward the more tightly bound region (closing nearer 40 AU). $\endgroup$
    – BMF
    Mar 12, 2019 at 22:50

The shield would act as a vacuum cleaner as the solar system moves through space (both in orbit around the galactic center and as the galaxy itself moves). Any interstellar dust would enter the shield but be erased on exit, which should leave detectable disturbance as we would leave a void in our wake that would slowly be refilled by surrounding dust. The void and the dust itself would not be visible so much as its affect on any light approaching from behind.

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    $\begingroup$ That's a good point. Now, my question is, can modern astronomers make measurements of interstellar dust densities at >10,000 AU? $\endgroup$
    – BMF
    Mar 12, 2019 at 16:34
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    $\begingroup$ That's a good question. Anything we're observing is much farther away than 10k AU, so that gap is just a small fraction of the total distance light would have travelled to reach us. One thing I was thinking about was that it's not the density of dust, but the "turbulence" caused by dust rushing in to fill the void. That should add a noticeable difference between objects visible behind us and objects visible in front of or to either side of us. (Not sure if "rushing" is the right word to describe that process given the low starting density.) $\endgroup$
    – chepner
    Mar 12, 2019 at 16:50
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    $\begingroup$ I'm not sure if we'd be able to see a disturbance as fine-grained as this. Astronomers only recently discovered that the Solar System and other nearby stars were in a "bubble" of lower-than-average hydrogen levels, and thus Bussard ramjets can't work. $\endgroup$
    – Mark
    Mar 12, 2019 at 21:01

Possibly, but far from certain

The proposed distance to the barrier - 10,000 AU dissects right through the Oort cloud. Currently, the detected object with most distant orbit around the Sun is "The Goblin", with the aphelion of 1955 AU, which is well short of 10,000. This means that we are not ready yet to see periodic objects which travel that far from the Sun. Maybe in another 10-20 years we'll see something with aphelion over 10,000 AU, but we haven't seen anything like that yet.

However, during the lifetime of the barrier (100 million years), Oort cloud would be depleted. This means that inner solar system would see a gradual decline in long period comets during that period. The Earth, Moon and other planetary bodies would be bombarded somewhat less. How much less and whether astronomers would be able to actually measure this decline, is difficult to tell. Oort cloud is not the only source of comets, and inner part of the cloud (close than 10,000 AU) would still be unperturbed.

P.S. "The Goblin" is potentially the most distant object that is a minor planet (with supposedly stable orbit), but not the most distant among all objects (particularly comets). A few of the near-parabolic comets apparently travel beyond the 10,000 AU limit, with semimajor axes as high as a whopping 446485 AU. So, today's astronomers DO have a way to detect this limit. However, the caveat here is that we don't know if those comets' orbits are stable. They may be on the very first rotation that comes close to the Sun, and once they go beyond 10,000 AU, they might disappear forever.

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    $\begingroup$ Seems to me that after 100 million years, we'd see a clear line where any oort objects left are either inside or outside the barrier and never cross it. Because any objects that used to have paths that crossed the barrier are now gone. We'd be see this as a characteristic lack of wobbly orbits but probably wouldn't see much unusual about it. All the elliptical orbits would be long gone before humanity had the technology to notice the difference. $\endgroup$
    – Ruadhan
    Mar 12, 2019 at 9:49
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    $\begingroup$ @Ruadhan That would still look 'odd' though, because it would be a fairly hard line beyond which nothing orbited - something we wouldn't have seen anywhere else in the observable galaxy. $\endgroup$ Mar 12, 2019 at 10:02
  • $\begingroup$ @DaveMongoose unless of course the same kind of structure exists around every other star, in which case we'd likely be able to detect them existing around those other stars and infer there's probably one here as well :) $\endgroup$
    – jwenting
    Mar 12, 2019 at 11:12
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    $\begingroup$ The oort cloud orbits between 5k and 100k AU. essentially we'd see a small number of objects orbiting inside the globe that don't intersect the boundary at 10k, (because any that did are long gone) and a hell of a lot that are outside and also don't intersect the boundary. So there'd be a band where only a few objects with strictly circular orbits could be found, no objects cross that band in either direction, and a hell of a lot of otherwise normal oort-cloud. Considering the band in question would be only as thick as the barrier itself, we might not notice anything. very few comets though. $\endgroup$
    – Ruadhan
    Mar 12, 2019 at 15:10
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    $\begingroup$ Further reading, the Oort cloud oscillates and shifts with a variety of different factors pulling on it during its lifetime, we'd certainly see the band of empty space where no oort objects might be found expand over its lifetime, by the present day it'd certainly be many AU across and quite obvious to any casual observer. $\endgroup$
    – Ruadhan
    Mar 12, 2019 at 15:23

I would argue that the answer to you question about whether or not we would be able to detect it is no. Obviously, such a device violates the laws of thermodynamics. Firstly, you have a conservation of energy problem. Any energy or matter simply vanishing or being destroyed violates this. There are two ways I can think of that being solved for it to not violate this: 1. The structure heats up with the equivalent amount of energy 2. Material is teleported elsewhere. The first one would likely result in detection. It would give off radiation if the structure heats up. If it were to radiate inwards, Earth would likely see some very strange signals coming in that wouldn't fit with astronomical models. That being said, it kind of depends on the temperature and emissivity of the structure because it could end up being lower energy than the astronomical "noise" so to speak (see Cosmic microwave background). If it were much hotter than this though, there would be an inconsistent amount of energy when compared with the expected star spectrum and would show up as a spike in energy density of the correlating emission spectrum across all stars. For the second case, this would absolutely result in a gravitational lensing effect that at best would show up some chromatic aberration resulting in different wavelengths hitting your camera differently. All of the images taken off objects outside of the solar system would be different in terms of colors lining up to objects inside.

However, I'm guessing these scenarios aren't what you have in mind. Based on your question and responses, it seems as though we should assume an ideal situation where by some effectively magic makes it work. Here, the issue is that the device would violate almost every conceivable law of physics, without producing a trace short of being very close to the device and watching something approach it. As far as I'm aware, there is no way that we can currently see an object with that precision from Earth. Any probe sent through would suddenly just stop sending signals. This would mean that the assumption would have to be from scientists that stuff just broke. Over a long period of time, eventually you would build up a case that there is something out there because your probes always fail at about the same distance but that could take at least 5-10 deep space probes. As far as I'm aware, there are only three probes we've sent out so far that will or would have already crossed that line. If we assume we just happened to have sent out a sufficient number of probes, it would indicate that something is up but not what. The probable cause by physicists would be a radiation belt we weren't aware of in the magnetosphere of the sun. Any proposal that such a device would exist would be instantly shot down as there was no certifiable evidence. It would take a long time before any sort of mission would ever be sent with the chance of detecting such a device since probes would just keep failing. Manned missions would likely be not allowed by current space launch culture and the unmanned missions would have to get lucky and see an object vanish or try to reflect a beam off an object on the other side. And keep in mind that across millions of years there would likely be a range of orbitals with no objects. This again would probably be chalked up to be some gravitational event in the solar system formation we don't know about. Ultimately all of these observations would result as a "dead zone" on our map of the solar system but we wouldn't uncover the true cause.

In summary, the device would likely result in a weird spot in astronomical data simply by virtue of losing probes at the same spot. However, the device itself likely would not be detected based on our current technology and the way space research is performed.

  • $\begingroup$ I had mentioned in the question that the boundary is invisible and is not a blackbody (emits no radiation). How the boundary works should not be a concern when determining its influences on the Solar System and its own internal interactions (which is essentially what you'd need to look at because that's what we look at; that is what would point the boundary's existence out to us). $\endgroup$
    – BMF
    Mar 12, 2019 at 13:39
  • $\begingroup$ However, you make a better point in the second body of your answer. As far as I'm aware, no probes (to-date) have crossed the 10,000 AU mark, though, you're correct in that there isn't much out at that distance to see, or at least, not much that immediately strikes us. $\endgroup$
    – BMF
    Mar 12, 2019 at 13:41

This is going to be a combination extended comment/answer.

The final answer, really, seems to be reduced to 'what your plot demands'.

Since the entire construct is hand waved, then you are free to choose. There are an abundance of answers that demonstrate the ability for it to be detected, but every one of these can be hand waved away so as to make it undetected.

The ultimate answer depends on exactly why the aliens encircled our system in the first place. To contain us, or for some other purpose? If they intended to contain us, methinks they would have allowed for some mechanism for information to escape, so they could monitor us. How would they know what we are doing, if no information could escape? If it was for some other reason, what is the purpose of making the sphere undetectable from within? As a starting point for conjecture, suppose the aliens encased star systems randomly, in order to obtain every bit of radiated energy that cane from them? A mega-huge power plant? That is, a 100% efficient energy capture system. Any energy that was reflected back into the solar system would reduce the efficiency (although it would conceivably be captured at some point). But why would it also not increase the efficiency by capturing all energy coming from BOTH sides? Again, it can be posited that all energy entering the system would eventually be captured upon its eventual exit, so allowing it in is simply using the system as storage. I am thinking, perhaps, that it might need control signals to reach and exit the sphere? Sensors to detect how much energy was still left in the system?

The Law of Unintended and Unknown Consequences can certainly have variable results in this scenario, in whatever direction and to whatever effect you want.

But to absolutely constrain these spurious effects, I would suggest not one, but two spheres, one inside the other. Anything entering the outer sphere from the outside (even if transversed the outer sphere several times) would be allowed to exit the inner sphere into the solar system, but if it went from the inside of the system through the inner sphere first, again even if it oscillated across the inner sphere boundary, it would be 'captured' and not allowed to escape the outer sphere. Thus, any products of decomposition from anything entering through the inner sphere would not be allowed back out, either through the inner or outer sphere. (This hand wavium rule allows for modification so some limited reflection back into the solar system can happen if desired). The particles would not have first come in through the outer sphere, to gain them immunity from capture.

That is, the inner sphere is completely transparent to anything coming in in one direction from the inside, and is completely transparent from the other direction to anything that came in through the outer sphere. It is opaque in this direction to anything that originated inside the sphere and did NOT come in from the outer sphere. The outer sphere is completely transparent to anything that came in from outside of the system, but in the other direction is 100% opaque to anything that came in through the inner sphere.

What happens between the spheres is far game for whatever hand wavium rules you wish to apply, what happens outside of the spheres is subject to all laws of physics.

This allows for the modification of the hand wavium zone to allow for whatever results you need. If the aliens need specific information to pass, there can be specific rules inside the hand wavium zone that allow for it. If the plot requires the sphere to be detected in some way, the rules in the hand wavium zone can allow for some reflection. If the plot calls for the spheres to be completely undetected, then the rules of the zone can say such things as 'if it came in originally through the outer sphere, it is remembered and can be tagged as external, so it will be allowed back out at any subsequent time (even though it is allowed into the system through the inner sphere, it will time-limited be considered 'external') or 'if it entered at anything less than a specific velocity or angle (meaning it was probably local to the Ort cloud) it would be immune from capture'.

Though it is up to the author to explain or not explain why these hand wavium rules are applied by the spheres, given the nature of why they were created in the first place.

  • $\begingroup$ When formatting my question, I intentionally left out plot details as they are rather distracting and uninvolved with the actual question. Why do you assume I want the alien boundary to go undetected? Truth be told, for the narrative of my story, it can go either way, detected or not. The boundary is the only handwaved thing I intend for my story. $\endgroup$
    – BMF
    Mar 13, 2019 at 17:18
  • $\begingroup$ I would NOT like to handwave away its consequences on the Solar System to sway the narrative this way or that—that's the meat and potatoes of a good science fiction story, consolidating and communicating the reality of it; throw all the weirdness into one big thing and keep the rest real and oddly familiar. I do like your idea of the shelled kind of structure. It works rather nicely into the plot in ways I hadn't anticipated. $\endgroup$
    – BMF
    Mar 13, 2019 at 17:19
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    $\begingroup$ I did not assume that you either wanted or did not want the sphere to be detected. I just gave a scenario in which the plot could go EITHER way, depending on requirements. There are two ways to write sci-fi - one way, in which the plot is completely outlined from start to finish, and the writing just fleshes everything out. That is, the author knows where the story line is going to end up, right from the get-go. The second, much more common in space opera, is for the author to just start writing and 'let the story go where it wants'. $\endgroup$ Mar 13, 2019 at 17:26
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    $\begingroup$ In the first, the only thing that sways the narrative is the original plot outline. Everything else falls into place. Under the second, the narrative can be swayed by what the author had for breakfast that morning, or whether the dog barked all night. $\endgroup$ Mar 13, 2019 at 17:28
  • $\begingroup$ I assumed you made such an assumption from your 4th sentence. Yes, I totally agree with those interpretations. I believe I've practiced them both. This is kind of off-topic, but in planning I normally leave the final several chapters of a story grey because I know I'll change and develop it further down the road. $\endgroup$
    – BMF
    Mar 13, 2019 at 17:33

Objects with rotation will pass through the barrier with a section sheared off, or they will have flat surfaces because of sections that attempted to leave while the barrier was intersecting the object.

If the object is big enough, slow moving enough and has a fast enough rotation then this feature may be noticeable.

You also need to think about what happens to angular momentum in this case. Since you've responded to other answers with "yeah but magic!" I can't tell you how this would work but in the real world there would be an issue with the moment of inertia suddenly changing and the object's trajectory suddenly changing without any force being applied to it. Which is another problem you're going to have to "magic away".

  • $\begingroup$ I don't understand your reasoning of the first sentence. Think of what's going on at the atomic level: as soon as the fundamental particles of an object intersect the boundary, they are deleted. The object on the macroscopic scale would lose mass and probably radiate some energy due to the breakage of atomic and chemical bonds, but the boundary itself is not a surface with which friction can be made against. A rotating object beginning to cross the boundary would essentially peel itself until it is gone. $\endgroup$
    – BMF
    Mar 12, 2019 at 18:29
  • $\begingroup$ Whatever momentum those particles contained while part of the macroscopic object is not transferred because of the boundary's nature. $\endgroup$
    – BMF
    Mar 12, 2019 at 18:34
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    $\begingroup$ A spherical object passing through the barrier would look like pac-man. $\endgroup$
    – JDrumm
    Mar 12, 2019 at 19:38
  • $\begingroup$ I see your point now. Unless the spherical object traces out some kind of cycloid or less, a fast enough one should make it through intact (tracing a sinusoidal). $\endgroup$
    – BMF
    Mar 12, 2019 at 20:10

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