Our Universe, because it exists in the present day, places us in an extremely privileged place. Had we come into being simply a few billion years earlier, we’d be unable to detect the existence of darkish power, and thus we’d by no means know the true destiny of our Universe. Similarly, had been we born tens of billions of years sooner or later — simply a few occasions the current age of the Universe — our native group could be only one large elliptical galaxy, with no different galaxies seen past our personal for a whole lot of billions of light-years. As far as we are able to inform, our Universe is dying, and a “heat death” awaits us. There could also be no solution to cease it, however may we one way or the other, with a sophisticated sufficient know-how, delay it? That’s the query of Patreon supporter John Kozura, who desires to know:
“After reading your posting about the natural death of the Universe as we passively watch, I got to thinking: what could an extremely advanced, Type III level civilization could proactively do to make a galaxy/local cluster run “efficiently” for longer to their benefit… are there ways we could act as a sort of large scale Maxwell’s demon to manage entropy and efficiently control the energy budget of the galaxy?”
If we do nothing, our destiny is sealed. But even throughout the legal guidelines of physics, we’d be capable of save our galaxy for longer than another one within the Universe. Here’s how.
If you wish to save the Universe, you first have to know what you’re saving it from. Right now, there are some ~400 billion stars within the Milky Way, plus much more in our neighboring galaxy, Andromeda. Both us and our nearest giant neighbor are nonetheless forming stars, however at a a lot decrease price than we did prior to now. In truth, the whole star formation price of the galaxies round in the present day is about a issue of ~20 smaller than it was at its peak, some 11 billion years in the past.
However, each the Milky Way and Andromeda have copious quantities of gasoline left in them, and we’re on a collision course.
- In about ~4 billion years, the 2 of us will merge collectively, resulting in an unbelievable star-forming occasion that ought to both eat or eject many of the gasoline in each galaxies.
- After about one other 2 or 3 billion years, we’ll calm down into a large elliptical galaxy: Milkdromeda.
- Another few billion years after that, the smaller galaxies inside our gravitationally certain Local Group will all fall into Milkdromeda.
Meanwhile all the opposite galaxies, galaxy teams, and galaxy clusters proceed to speed up away from us. At that time, star formation in our future dwelling, Milkdromeda, shall be merely a trickle, however we’ll have extra stars current inside it than ever earlier than, numbering within the trillions.
If we do nothing, the celebs that come into existence will merely burn out as soon as sufficient time passes by. The most large stars solely dwell for a few million years, whereas stars like our Sun may need a lifetime extra like ~10 billion years. But the least large stars — the purple dwarfs that hardly have sufficient mass to ignite nuclear fusion of their cores — may proceed their gradual burning for as many as ~100 trillion (1014) years. So lengthy as there’s gasoline of their cores to burn, or sufficient convection occurring to carry new gasoline into the core, nuclear fusion will proceed.
Given that 4 out of each 5 stars within the Universe is a purple dwarf, we’ll have a lot of stars for a very lengthy period of time. Given that there could also be much more brown dwarfs on the market than stars, the place brown dwarfs are a little bit too low in mass to fuse hydrogen into helium the way in which regular stars do, and that some 50% of all stars are in multi-star programs, we’ll have inspirals and mergers of those objects for even longer intervals of time.
Whenever two brown dwarfs merge collectively to type a large sufficient object — greater than about 7.5% the current mass of our Sun — they’ll ignite nuclear fusion of their cores. This course of shall be accountable for almost all of stars in our galaxy till the Universe is a whole lot of quadrillions (~1017) of years outdated.
But as soon as the Universe reaches that age, one other course of will come to dominate: gravitational interactions between the celebs and stellar remnants in our galaxy. Every as soon as in a whereas, two stars or stellar corpses will go shut by each other. When this happens, they’ll both:
- work together with one another however each stay within the galaxy,
- collide and merge collectively,
- tidally disrupt one or each members, doubtlessly getting torn aside in a cataclysmic tidal disruption occasion,
- or — and that is essentially the most fascinating chance — they may trigger one member to turn out to be extra tightly gravitationally certain to the galactic heart, whereas the opposite member turns into extra loosely certain, and even ejected solely.
That final chance, on lengthy timescales, will dominate the destiny of our galaxy. It may take ~1019 and even ~1020 years, however that’s the purpose the place virtually all the celebs and stellar remnants will both be despatched into secure orbits that may decay by way of gravitational radiation, inspiraling across the galactic heart till every little thing merges into one huge black gap, or ejected into the abyss of intergalactic area.
Beyond that point, orbital decay from gravitational radiation and black gap decay from Hawking radiation are the one two processes that may matter. An Earth-mass planet in an Earth-sized orbit round a stellar remnant with the mass of our Sun will take round ~1025 years to spiral in in order that they merge; essentially the most large black gap in our galaxy, whereas a black gap of the mass of our Sun will take round ~1067 years to evaporate. The most large black gap within the identified Universe may take upwards of ~10100 years to totally evaporate, however that’s just about all we’ll must look ahead to. In a sense, if we take no additional interventions, our destiny is sealed.
But what if we needed to keep away from this destiny, or at the least push it out into the long run so far as doable? Is there something we may do about all or any of those steps? It’s a large query, however the legal guidelines of physics permit for some actually unbelievable potentialities. If we are able to measure and know what the objects within the Universe are doing to an correct sufficient precision, then maybe we are able to manipulate them in some intelligent solution to preserve issues going a little bit longer.
The key to creating it occur is to start out early.
Think about a similar drawback: what would we do if we found an asteroid, comet, or different considerably large object had been on a collision course for Earth? You’d ideally wish to deflect it, in order that it might miss our planet.
But what’s the most effective, best method to do that? It’s to “correct” the course of this physique — not the Earth, however the lower-mass object that’s headed in direction of us — as early as doable. A tiny change in momentum early on, which arises from a drive that you just’d exert on this physique over a period of time, will deflect its trajectory by a far more vital quantity than that very same drive will even a tiny bit later. When it involves gravitational dynamics, an oz of prevention is far more efficient than a pound of remedy a little bit later.
This is why, in the case of planetary protection, a very powerful issues we are able to do are:
- determine and observe each object above a sure hazardous measurement as early as doable,
- characterize its orbit as exquisitely exactly as we are able to,
- and perceive which objects it’s going to work together with and go near over time, in order that we are able to mission its trajectory precisely very far into the long run.
This method, if one thing’s going to hit us, we are able to intervene on the earliest phases doable.
There are a number of methods we are able to take to deflect an object by a small quantity over a lengthy time frame. They embrace:
- attaching a “sail” of some type to the item we wish to transfer, reliant on both photo voltaic wind particles or the outward flux of radiation, to alter its trajectory,
- creating a mixture of ultraviolet lasers (to ionize atoms) and a robust magnetic discipline (to funnel these ions in a specific course) to create a thrust, thus altering its trajectory,
- attaching a passive engine of some type to the item in query — like an ion thruster — to slowly speed up a strong physique within the desired course,
- or to easily transfer different, smaller lots close to the neighborhood of the item we wish to deflect, and letting gravity handle the remainder, like a sport of cosmic billiards.
Different methods may be kind of efficient for various objects. The ion thruster may work finest for asteroids, whereas the gravitational resolution may be completely essential for stars. But these are the sorts of applied sciences that may usually be used to deflect large objects, and that’s what we’d wish to do to manage their trajectories in the long term.
What I can envision within the far, far future, is a community of a mixture of those that discover and hunt down strong lots all through the Universe — asteroids, Kuiper belt and Oort cloud objects, planetesimals, moons, and many others. — all of which have their very own atomic clocks on board, and robust sufficient radio indicators to speak with each other over giant distances.
I can envision that they’d measure the matter inside our galaxy — the gasoline within the Milky Way, the celebs and stellar remnants in Milkdromeda, the “failed stars” that may merge to type subsequent stars within the late-time Universe, and many others. — they usually may calculate which trajectories they would wish to take with a view to keep the utmost quantity of baryonic (regular) matter inside our galaxy.
If you possibly can shepherd these objects into secure orbits for longer, in order that the method of violent leisure — the place low-mass objects get kicked out over time whereas higher-mass objects sink to the middle — it might be a solution to keep the matter that we now have for longer, and that may allow our galaxy to outlive, in a sense, for for much longer intervals of time.
You can’t cease entropy from rising, however you possibly can stop entropy from rising in a specific method by performing work in a specific course. So lengthy as there’s power to extract out of your atmosphere, which you are able to do as long as stars and different sources of power are shut by, you should use that power to direct in what methods your entropy will increase. It’s type of like how, while you clear your room, the general entropy of the “you + room” system will increase, however the dysfunction in your room goes down as you place power into it. It was your inputs that modified the scenario of the room, however you paid the value your self.
Similarly, the shepherding probes connected to varied lots would pay the value by way of power, however they may preserve lots in a far more secure long-term configuration. This may result in:
- extra gasoline remaining throughout the Milky Way to take part in future generations of star-formation,
- extra stars and stellar remnants remaining in Milkdromeda and fewer giant lots falling in in direction of the central black gap in our galaxy,
- and longer lifetimes for stars and stellar remnants, rising the period of time that mergers and the ignition of recent stars can happen.
In idea, there’s a solution to maximize the period that we’ll nonetheless have stars (and sources of energy) in no matter’s left of our Local Group very far into the long run. By monitoring and observing these clumps of matter floating by area, we are able to calculate — or have synthetic intelligence calculate — the optimum set of trajectories to deflect them onto, maximizing the quantity of mass, the variety of stars, and/or the power flux of starlight inside our future galaxy. We may be capable of improve the period over which we’ll have usable power, stars with rocky planets round them, and even, doubtlessly, life, by components of 100 and even higher quantities.
You can’t ever defeat the second regulation of thermodynamics, as entropy will at all times improve. But that doesn’t imply you merely have to surrender, and let the Universe run amok in no matter course nature would take it. With the proper know-how, we are able to decrease the speed at which stellar ejections happen and maximize the whole variety of stars that may ever type, in addition to the period that they’ll persist for. If we are able to survive our technological infancy and actually turn out to be a spacefaring, technologically superior civilization, we’d have the opportunity, in a sense, to save lots of our galaxy in a method that no different galaxy is ever saved. If a super-intelligent civilization is on the market, this may be the proof they’d search for to know, even from throughout the now-unreachable Universe, that they honestly weren’t alone.
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