despite the galactic collision and the dazzling view from Earth, it’s extremely unlikely that any individual stars will collide because of the sheer amount of empty space in galaxies.
Conventional wisdom is that we will have almost zero collisions between celestial bodies due to the vast distances involved; but it seems plausible that the gravity of a massive celestial body could disrupt orbit, enough to alter seasons or even destabilize orbits altogether? https://en.wikipedia.org/wiki/Rogue_planet
I'm sure there are far too many variables to predict with any accuracy, but curious if a better space nerd than I has any guess as to the likelihood of such an event.
Looking at the video, yes. But not in the form of something colliding with the Sun. I would guess the most likely interaction would be perturbations of orbits as the solar system deals with these freight trains going by. That could result in anything from planets changing orbits as they follow the changes in the Sun's orbit around the galactic center, to having the entire solar system ejected on its own path away from the galaxy (that first pass "collision" is going to impart a lot of momentum on different systems. It shows a 'spray' of things going out from the galaxy but those things are stars with their nominally attached planetary bodies!)
The planetary orbits in the solar system are vastly smaller than the typical distance between stars in the combined Milky-Way-Andromeda system. The only difference will be a slightly higher typical speed for Andromeda stars compared to the relative motion of stars in the Milky Way disk. But that's only by like a factor of 10, and I don't have any reason to think that will cause a perturbation that's noticeable above the normal uncertainty from chaos in planetary orbits.
Ok, that is the first thing I've read that makes it sound like fun to be around in 4B years to watch it all happen.
It is also interesting to think about two galactic civilizations coming together over a common need to survive in the post collision Milkdromeda galaxy.
Only thing I can think of at the moment, geologically-speaking and within a short time span could be a Super-volcano eruption that engulfs the atmosphere in smoke, causing another ice-age. Another method of danger could be a meteor impact, though it's time span is unknown until we detect it, and not sure if that fits your geological category.
The fact that humans, much like other species, are geared towards expansion. And once we run out of frontiers to conquer, that expansion energy seems to go towards biting each other's necks instead of solving common problems together. Doesn't seem to be specific to humans [0]
That goes somewhat against Steve Pinker's observation that humanity is becoming increasingly more civilized and less destructive to other humans. Of course, the long-term data isn't there, but the logic is compelling. We may have hit a point where the concept of large-scale war is just too expensive, economically and morally.
The US, currently the greatest military power in history, can't currently even justify a Vietnam-scale conflict, much less a WWII-scale one. Improvements in agriculture have radically reduced food as a resource war motivator, and I think that in a few decades, renewables will have wiped out energy as a resource war motivator as well.
Ideology without serious contention doesn't lead to war, it leads to taunting remarks on the internet.
> We may have hit a point where the concept of large-scale war is just too expensive, economically and morally.
In 1913, "less than a year before the Great War broke out, the Economist reassured its readers with an editorial titled “War Becomes Impossible in Civilized World.”
“The powerful bonds of commercial interest between ourselves and Germany,” the Economist insisted, “have been immensely strengthened in recent years … removing Germany from the list of our possible foes.”"
>"Doomsday Clock timekeepers say risk of global annihilation remains at Cold War highs"
The only reason for that is the misguided decision to include some fuzzy-headed interpretation of catastrophic, anthropogenic global warming (CAGW) in the risk of "doomsday".
The risk of actual nuclear war is far lower today than it was during the Cold War. The risk of an individual nuclear weapon going off in a city is much higher, however.
> The risk of actual nuclear war is far lower today than it was during the Cold War. The risk of an individual nuclear weapon going off in a city is much higher, however.
Please explain why do you think that the systems that are automatically triggered by the nuclear weapon going off in a city would not do what they are designed to do: all respond to the perceived attack with their full power.
Also explain how the humans trained to start the retaliation sequence would all not do what they are trained to do, once a city where their families are gets destroyed.
The future wars, I think will be more civil unrest due to income inequality. Eventually, I see us moving more towards a star-trek like society when we have full-automation. Nobody needs to work, but everyone can contribute in terms of research and scientific studies or art/etc...
Service jobs won't be needed, but we as a civilization can't just sit idle. We still need fulfillment so whether there's money or not at that point we need to encourage future fulfillment else we die out from sheer boredom.
I like to hope we move past all our petty differences, embrace the humanity that we are one single species. Then we drop the super stars, celebrity adoration, and desire to be uber wealthy and 'control' other people and we can focus more on arts and sciences. Arts for people to enjoy life, sciences for people to explore what's out there.
Imagine if the only careers were in entertainment and science/research what we could accomplish and imagine if everyone had equal footing to go into their chosen path. If we had 10x the scientists or 100x the scientists working on global problems and even intergalactic ones. We might actually make it to the stars.
But before we get there --there will be unrest and wars, just more middle class vs elites. Also potential wars for water as it becomes more scarce if we don't fix global warming soon.
Civil unrest that gets expressed via stable democratic institutions is just fine. My concern is wars and violent revolutions, which (hopefully) are on their way out.
I dream of a day when wage labor is looked back on as almost as oppressive and horrible as chattel slavery. We're a long way from that, though. The technology is almost here, but the political will is not.
The trick, then, is fulfillment. How do we give our lives meaning, if not through our labor? And how do we fight the brutal addictions of social media and passive consumption in order to achieve individual meaning? I fear a future where we don't have to work, but rather spend all our time sharing memes about how lonely and depressed we are.
That hypothesis made sense in 1947, after the most destructive war the world had ever seen. The 72 years since have been the most peaceful and prosperous in recorded history.
It's crazy just how little of the Earth we are crammed into though. I'd imagine we could branch out a little more, giving people more space, if it were properly managed. More settlements, but make all the space in between untouchable reserve.
Precisely. And (I know the average map makes it look even bigger than it is but still) just look at Siberia. It's hard not to be cynical and conclude that the land owning class deliberately seek to keep the population corralled.
I don't think it's the land owning class that is keeping people in big cities. I think people tend to naturally congregate in bigger and bigger cities, easier transportation is bringing more people in rather than distributing them.
I read that Taleb wrote something about this recently.
Agreed, I'm speculating. I'm just coming more and more to the conclusion that very few phenomena that disbenefit the rich are allowed to persist for very long.
Awesome bit of trivia hidden in that very interesting Wiki page:
> Calhoun's work with rats inspired the 1971 children's book, Mrs. Frisby and the Rats of NIMH, by Robert C. O'Brien, which was adapted into a 1982 animated film, The Secret of NIMH.
Calhoun did his work on rats/mice at the National Institute of Mental Health (NIMH).
I was similarly thinking of other civilizations. It seems incredible that you could scan your eyes over a few degrees of sky and see a hundred billion other stars, of which some must have life-supportable planets [1].
So my thought process was: have their scientists realized that the Milky Way is going to collide with them in 4B years? Are they already sharing pictures of what it will look like?
If that were true the night sky would be glowing like the surface of a star. In fact the overwhelming majority of rays cast intersect only the cosmic background, which was the primordial plasma at the time of recombination[1], long before any stars formed.
[1] That is, when the hot gas cooled down enough to convert from free electrons and protons (and some helium nucleii) that scatter photons into neutral atoms that don't.
Yes, it was mind blowing to me to learn that, because the night sky is dark, the universe can’t be both infinitely old and infinitely sized. I’ve heard some nuances there too... we could be living in a finite pocket of an infinite universe.
Most photons emitted from within our solar system are liable to collide with dust or gas eventually, most likely in the interstellar medium of our galaxy. Only a tiny fraction will collide with stars in our galaxy. The rest of our galaxy cluster covers a small solid angle of the skies of any of the bodies in our solar system. Finally, the small minority of photons that escape our galaxy cluster without being absorbed are most likely to stretch to arbitrarily long wavelengths and vanish from practical physical detectability well before the infinite future. It is vanishingly unlikely for an individual photon to couple to a lightlike geodesic that intersects a star at more than a few billion light-years.
Even so, elsewhere on this thread someone pointed out that space is almost entirely empty space, and so, with the exception of hitting the moon or the sun, the chance of any arbitrary infinite straight line projected from Earth actually hitting something is vanishingly small.
Out of curiosity, I looked it up, and it seems like there's less than a billion years left for life as we know it on Earth before the Sun sterilizes the planet. That doesn't mean some of our descendants won't figure out ways to move farther out in the Solar System (or to other planetary systems), to survive it.
We are a long way from being able to sterilize the Earth. Heck, I don't think we could even wipe out humanity - or even civilization - much less all the myriad forms of life out there that thrive in conditions that would kill humans instantly. (Go to Yellowstone, see the brightly colored pools of boiling volcanic mud, realize those pools are brightly colored because they're full of living beings...)
I think what we're looking at right now is making life a little more uncomfortable and expensive for part of humanity. That's as bad as we can manage right now. The fact that we treat it like the end of the world says more about us than the damage itself does.
> Heck, I don't think we could even wipe out humanity - or even civilization
You are talking about global warming and the like, right? There's another possibility, and it involves nuclear weapons. THOSE can sterilize the planet many times over.
While we MIGHT be able to wipe humanity off the planet with nuclear weapons [0] and would certainly create a mass extinction event, it is extremely unlikely we would be able to sterilize the earth. Even if we somehow manage to wipe out all multi-cellular life (which would, at a minimum, require completely vaporizing our oceans to expose deep ocean vents), it would take massively more destruction to wipe out all single celled life on the planet (which would likely require removing the entire planet's crust.)
Yes, I'm talking about global warming and other environmental damage, not nuclear war. But we're a long, long ways off from nuclear war being able to sterilize the planet. I don't think nuclear war could even end civilization - there are too many countries not in the nuclear club who probably wouldn't be targets in a nuclear war. Would someone bother to nuke, say, Copenhagen? Or Cairo? Or Bangkok? Or the entire South American continent? I can't even think of nuclear targets in the southern hemisphere, which would be somewhat isolated from fallout etc as well thanks to distance and equatorial weather patterns.
The vast majority of the stars will pass through each other; what I'm curious about is what happens at the galactic cores, and how many solar systems will end up being swallowed by the super-massive black holes at the center of each galaxy. Also, what are the side effects of two black holes merging? Have we ever observed such a thing?
The distances are so vast, that essentially, yes. Think about two sailors in small boats, crossing an ocean in opposite directions, and how unlikely it would be that their boats collide. Now multiply that by several orders of magnitude.
One of my favorite factoids: if you fire a laser from the surface of the earth (and the beam magically stayed perfectly straight), you have a small but significant chance of hitting the sun or the moon, but anything beyond that, the scale is so enormous, the odds that your laser would ever hit a celestial body anywhere in the universe are effectively zero.
Anywhere in the observable universe. If it is truly infinite and we pretend the laser instantly reaches wherever we point it then the chance is pretty much 100%.
Yes, otherwise even a laser beam that diverges slightly from being perfectly collimated would subtend a fraction of the night sky and thus contain a large number of galaxies.
You're confusing me more. Stars passing through each other like you said before to me implies collision. Would you say these sailors are going to pass through each other?
Effectively they'll all miss each other. There is so much empty space in between stars that even when two galaxies collide the stars will interact gravitationally, but likely none will physically collide.
Think of two clouds of gas colliding. The clouds as a whole collide, yes, but there's no molecular fusion happening. The molecules themselves don't collide.
"Pass through each other" is not the clearest wording.
"practically no difference ... gravitationally, provided one is at a very large distance compared to the outer surface of an astrophysical black hole." would be more accurate.
Up close to a real black hole additional shear and tension becomes obvious, although you will generally be in the region that would be close to the surface of a star of comparable mass.
Astrophysical black holes are more complicated objects than the theoretical Vaidya-Bonnor-Kerr (VBK) black holes, especially when they are not isolated. VBK black holes absorb radiation and emit Hawking radiation (V part), including self-interacting matter (B part, although that is mostly dealing with classical electromagnetism), and they also rotate (K part). VBK breaks several symmetries: the exterior spacetime is not static, not stationary, and spherical symmetry goes to axial symmetry, including all the incoming and outgoing radiation. Real rotating black holes would break axial symmetry because real matter tends to clump (in particular theoretical VBK exterior matter does not look like accretion discs).
Small perturbations of the axial symmetry of VBK black holes tend to cause black holes to spin up as matter falls onto them. There is observational support to suggest that most real black holes are likely spinning extremely rapidly. The Kerr vacuum around a VBK is equipped with regions in which objects are dragged around in the direction of the VBK black hole's rotation. As the original angular momentum of the star may be increased by infalling material, a real black hole likely has a strong region extending well outside of where the surface of a star of comparable mass would be. While the dragging effect falls off quickly with distance outside the outermost surface of the outermost of these regions, if we replaced the sun with a real black hole which rotates at extremely high rates, all eight planets' orbits would precess compared to their orbits around the sun. Given enough observation time, this would be especially noticeable for objects on high-inclination, low-ellipticity orbits, even if they are near the outer edge of the Oort cloud. Reducing the angular momentum dramatically increases the observation time needed to distinguish gravitationally between a (growing!) solar-mass black hole and a (shrinking!) solar-mass star.
Beyond the Oort cloud things aren't gravitationally bound to our solar system anyway, so by the time you're a couple hundred thousand astronomical units away, you are on safe territory with practical gravitational indistinguishability.
On the off-chance that humans are around in a billion years, I would hope we'd have learned to manage a planet-sized climate by then, so preventing Earth from turning into Venus should be manageable. Certainly more manageable than surviving another billion years, at least.
If there are descendants of humans in a billion years, their capabilities might only be limited by the laws of physics - and I would not even be surprised if this time is off by quite a few orders or magnitude (up to like ... six? Edit: that would mean as early as 1000 years from now. It's a bold guess, I know).
>If there are descendants of humans in a billion years, their capabilities might only be limited by the laws of physics
Or, something few consider, they might have plateaud way earlier, after most low hanging fruits have been achieved (fire, steam engine, electricity, nuclear power, computing, telecommunications) and the rest are diminishing returns...
If humans will learn how this 'genetics' thing works, it might be a total gamechanger. Once we understand how to create a life that works like we want it to, all bets are off, and lots of things will be possible: indefinite lifespans, lifeforms alteration, hybernation, etc.
>Isn't that what the "limited by the laws of physics" mean? Worldwide climate engineering is within that envelope.
"Limited by the laws of physicals" implies only physical laws are the limitation.
Whereas my response was more about being more limited (due to complexity, lack of resources, etc). So response was about a possible way lower envelope. I.e. not necessarily much more advanced than we are today, with diminishing advances in various areas.
So no "worldwide climate engineering" (except the clumsy stuff we already have), and no personal robot assistance of sci-fi style...
Meh, the sun will grow warmer but won't enter it's red giant phase until about 5 billion years from now. Placing reflectors in a lagrange point to control the amount of solar energy reaching Earth with be child's play. Even once it enters the red giant phase, it'll be several hundred million years before it consumes Earth.
This is almost as long as the Earth has existed since its formation. It is an extremely long length of time. Suffice it to say humans will not be around anywhere close to that time. Nor will any currently recognisable life. All current species and families would've drastically changed and evolved into other forms, with the exception of simple, unicellular life. And of course around this time our Sun will be on its way to a red giant so the Earth would be becoming well nigh inhospitable for life (as it exists now). As for intelligent life, I don't think intelligence can remain stable for such lengths of time.
The Earth will be inhospitable for life (as we know it) within the next 800 million years, in fact. It’s a bit sobering to think that we’ve progressed through about 75% of the time life has on this planet.
Yeah, but this is astrophotography _and_ it's from Nasa, so it's what it would look like with ultra-long exposure, lots of photoshop, and false color. If we extrapolate the naked eye view, it'd be a grayish smudge at best.
The first couple of images show the milky way pretty much as it actually appears from a suitably dark location. Maybe just a bit brighter and more contrasty than I recall, but I'm sure there are many here who see it almost nightly and can speak to that better. Just saying, it doesn't look grossly exaggerated to me.
I was moved by the images. It reminded me about how selfish I am the way I grab at things. At these time scales would it matter if I had more prestige or material possessions. I want to become kinder but I don’t know how or if I ever can. The more immediate instincts of anger and jealousy hold far more sway.
At these time scales does kindness matter any more or less than prestige or possessions? The only behaviors that might matter are those that could lead to our interstellar diaspora. It's not clear that kindness is or isn't a greater motivator for that than pride.
From a logarithmic standpoint, around 1 billion years is when geologically interesting things happen to the earth as it's no longer to sustain life an have the oceans boil over as well.
We could have adjustable rings of reflective shielding orbiting the Sun and throughout the entire Solar System - well before then. Potentially even be capable of slowly moderating the Suns evolution. A billion years has unfathomable potential for technological development.
My favorite datum from this page is that the days will be 1 hour
longer in 180 million years. If the year lengths are constant, by
linear interpolation some time around 63 million years from now the
years will be exactly 360 days, just like the ancient Babylonian
calendar. What a great time that will be to be alive and to be a
programmer, with exactly 30 days every month.
It should be noted that these views will require long time exposure photographs.
The surface brightness of Andromeda and the Milky Way are both around 22 mag/arcsec2. As andromeda grows closer, the surface areas spreads out in our sky, so even as it gets closer it’s not really going to get brighter.
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