Science Daily altered one sentence from the originally regurgitated PR, and I think it thoughtlessly corrupted its entire meaning.
SD: "The blast generates two jets of gamma rays which travel out..."
PR: "The blast generates two jets which travel out ... The jets emit gamma rays,..."
Implication from their creative edit is that the blast itself shot out gamma rays (photons) at light speed, whereas the paper's authors actually described something else, a decades-long process of ejecta compressing and interacting to create gamma emissions. "The long time baseline of this event offers the best available constraint in afterglow evolution as the bulk of shock-accelerated electrons become non-relativistic."
My understanding is that the famous '91 OMG particle (proton?) was theorized to have been generated by an expanding shock wave, except unlike here the scientific community then spent some time doubting their readings and being unable to re-verify the phenomenon. Conversely this new study observed such an event spanning from 1975-2017 using 7 different instruments.
Since then, over 70 more like it have been seen; most seem to arrive from the Ursa Major direction, "from a distinct source near our galaxy and not from sources spread all over the universe." https://www.sciencemag.org/news/2014/07/physicists-spot-pote...
It's a shock wave. Physically it really is the same thing. You can reasonably discuss the idea of "pressure" and a speed of "sound" in the interstellar medium, and what happens when a discontinuity like rapidly heated gas from a GRB starts to propagate.
It's not the term astronomers would use, but honestly it's not wrong. My quibble would be that despite it being a common term, "sonic boom" doesn't really convey much information to a novice reader. Most people are just going to hear that as "big boom" and not understand that a shock wave is something distinct from a regular noise.
I sometimes think that they answer to the Fermi paradox is that the universe is an exceptionally dangerous place. Even when intelligence evolves, it has to dodge a whole bunch of bullets from the universe randomly sterilizing chunks with GRBs.
>I sometimes think that they answer to the Fermi paradox is that the universe is an exceptionally dangerous place. Even when intelligence evolves, it has to dodge a whole bunch of bullets from the universe randomly sterilizing chunks with GRBs.
Or maybe since all this started with the big bang, there's some other civilization at a similar level of development at the opposite end of the universe - so far away we'll never cross paths?
Or maybe there's only 1 intelligent form of life per universe, but many universes?
If you have read Fermi's paradox you know that it deals with only the visible stars in our own galaxy. The question he posed is why hasn't one of those planets orbiting one of those stars already created a galactic civilization that colonized the Milky Way.
It could be that we're the first/only group to achieve sentience in the galaxy but the probability of that being true is astonishingly small. (Hence the paradox) The conjecture is essentially a "negative space illuminator" which is to say it suggests there is some piece of information that exists but is not currently known that would resolve this apparent paradox.
If we were to discover that events happened every 'n' million years or so that sterilized stars in a 'm' thousand light year radius, a function of these two components would tell us for what values of n and m that would cancel out the survival and thus emergence of intelligent species.
The other resolution to Fermi's paradox is much simpler and much less interesting. Maybe interstellar travel is as difficult as all our scientists tell us it is. No civilization has colonized the Galaxy because it's simply too difficult. Maybe FTL travel really is impossible. Maybe SETI hasn't detected anything because generating a signal loud enough for us to detect is a stupendous amount of energy, and it's simply too much energy for a single planet civilization to justify using on a radio transmission that's going to travel at most a quarter of the way across their star system.
Maybe all the science fiction we love so much really is just fiction.
Even without FTL travel, on galactic timelines, we could presume to see colonization spread very rapidly through the galaxy. For example, this answer on quora shows with some pretty conservative timelines, the galaxy should still be riddled with life: https://www.quora.com/Could-the-answer-to-the-Fermi-paradox-...
Those timelines don't seem very conservative. 1% sounds like a nice, small number, but 1% of the speed of light is insanely fast. It's about 200 times faster than our fastest craft to date. We might envision launching a probe 200 times faster in the future, but a colonization ship would also weigh millions of times more and have to slow down somehow.
It's not clear that we'd be able to do that in 10,000 years (or ever) with "shoot stuff out the butt" propulsion, so we'd probably need propulsion based on different physics which may or may not actually exist. We'd definitely need new physics for constant 1g acceleration into relativistic speeds.
Maybe we could hitchhike on progressively faster interstellar asteroids or something, but that would void the assumption of having the ability to reach all parts of the galaxy.
You have to travel with a massive amount of mass. Space is really dangerous. There are high energy particles that want to mess up your 'ship'. Even worse things like neutral hydrogen are hard to block with energy style shields. Then you have the issues of long times without high gravity. Then you have to carry enough 'stuff' and energy to recycle absolutely everything you need, ever.
>Maybe SETI hasn't detected anything because generating a signal loud enough for us to detect is a stupendous amount of energy, and it's simply too much energy for a single planet civilization to justify using on a radio transmission that's going to travel at most a quarter of the way across their star system.
Plus even if you can do something doesn't mean you should
>It could be that we're the first/only group to achieve sentience in the galaxy but the probability of that being true is astonishingly small.
If life is extremely rare, then that doesn't seem so unlikely. If life were so rare than on average, after 15 billion years, only one out of every trillion galaxies has life evolve, then every instance of intelligent life should see itself as being alone.
I think people are too quick to write off the possibility that life really is this rare. I think people reason "if life were so rare, then I wouldn't be here to exist to think about it", but I don't think that's a correct way of thinking about it. If life is really that rare, then the rare instances of life could all think that same thought process too, and they'd clearly be wrong.
Maybe if life is super rare, we should expect to find ourselves in a much older universe, but maybe this current age of the universe is actually more suitable for life than other times. (Some crazy hypothesizing: If you accept the many-worlds interpretation, maybe periods early in the history of the universe, before the universe has branched so many times, in some sense have more "measure", and so observers are more likely to find themselves here. This is definitely a more "out there" idea; I'm not hingeing anything off of this idea, but I think it's worth mentioning while thinking about the anthropic principle and fermi paradox. I'm also hesitant to give it too much weight since if branching happens uncountably many times every moment, then if this effect does apply, then I'd expect it to overwhelm almost everything else and we should expect to find ourselves at the absolutely earliest possible moment. Arguments about when we should find ourselves in history seem to always go weird -- see the Doomsday Argument.)
How about: The physical laws of the universe just don't allow a practical way for us to interact. "Space is big."
Science fiction authors can imagine all sorts of ways we could communicate or travel across interstellar distances, but really we have no idea how to build them. Maybe there just isn't some new discovery to be had.
Traveling across interstellar distances is not sci fi, at least not the act itself. What is sci-fi is an engine capable of accelerating for a sufficiently long period of time. Something people often mistake is that the speed of light is a hard cap on travel rates. It's more complex. More educated individuals tend to think that as objects approach the speed of light, their mass approaches infinity - that is correct from the perspective of an observer. But from the perspective of something continually approaching the speed of light, there is no effect on your mass. This is where time dilation and space contraction come into the picture.
Anyhow, setting aside all of that stuff the important thing is that if we can manage to generate engines capable of creating fairly modest acceleration (e.g. 1g) then interstellar travel is completely possible within a single human lifetime. There is a calculator here [1]. The relativistic effects are exponential but to give some examples:
- 100 light years of travel = 9 years of 1g acceleration
- 1000 light years of travel = 13 years of 1g acceleration
- 1 million light years of travel = 26 years of 1g acceleration
- 15 billion light years of travel = 45 years of 1g acceleration
To be clear this gets into the fun time games of relativity though. Though you may be able to travel 15 billion light years in one human lifetime, from the perspective of an at rest observer (such as everybody back on Earth) - 45 billion years of time will indeed pass during your 45 year journey. So, for instance, the sun will have long since turned into a red giant by the time you arrive. This leads to really interesting 'paradoxes'. You could leave Earth on your relativistic starship towards some system billions of light years away. And when you get there you find that the system is completely colonized and hyper modern. Earthlings that left a million years after you got there first and colonized the system millions of years ago. They traveled at 2g acceleration... Reality is much stranger than any sort of fiction.
But anyhow of course the issue is just discovering a technology to enable years of 1g acceleration. And while that may be far away, I think few would argue it's something that will ultimately prove to be impossible.
But anyhow of course the issue is just discovering a technology to enable years of 1g acceleration. And while that may be far away, I think few would argue it's something that will ultimately prove to be impossible.
Why do you think this is possible?
The argument in favor seems to be something along the lines of "well we can sustain 1G for a few hours, we just need to extend that". But right now there's not even a roadmap to building such a device... and when you factor in all the other issues (life support, materials longevity), it seems to be constructed of pure optimism.
"It's not possible" seems like a perfectly plausible explanation for Fermi's paradox. The alternative seems less plausible - that's why it's called a paradox.
A paradox is most commonly just a self refuting but otherwise logical and sound statement that seems to be true. So there are problems whether you 'accept' or 'deny' the statement. This statement is false. is a good example. It being false or true poses problems. Everything we know leads us to believe that there should be extraterrestrial civilizations everywhere. That's a paradox because again whether true or false, it poses problems. If false, then where is the mistake we have made? If true, then why do we see no evidence of such civilizations?
Interstellar travel is nothing particularly special. The voyager probes, launched using 70s era tech that was not designed to last anywhere near this long, are making it to interstellar space with no problem and still happily transmitting on top of it. Those probes will end up eventually being trapped in the orbit of some other body, and orbit it. They're not just going to disintegrate. This means we've already left a calling card in interstellar space. And that card was sent from less than 20 years after we learned how to put anything into space. Think about how much more we will put into space, and interstellar space, over the next 100 years. Now imagine the next million years. And these timescales are all still just blinks of an eye on astronomic scale.
The only issue is increasing acceleration. And there are already countless near tech 'roadmaps' to that. Laser propulsion, anti matter drives, fusion drives, etc. For instance we could do an entire manned Mars mission on a tiny fraction of a gram of anti matter reactant if we could start to control the lovely side effects like gamma ray radiation. And then when you start to imagine what we don't know...
And that card was sent from less than 20 years after we learned how to put anything into space. Think about how much more
"Think about how much faster CPUs will be in 2018!" -- late 1990s
Laser propulsion, anti matter drives, fusion drives
All of which require significant breakthroughs in physics or materials engineering that may not come. There is no fundamental law of the universe that says we can have these things, or that they will ever be of practical use. You can't extrapolate from 50 years of modest success with chemical rockets.
even if such travel became possible, what could motivate anyone to actually do it at scale? if they're anything like humans, there would probably be a few crazy beings who would do it just to do something extreme, but aside from escaping a dying world, i can't see any reason why such a journey would be attempted at scale. what's the point of having a galaxy spanning civilization when the origin system would be destroyed every time you made a roundtrip?
I've had this conversation before and something interesting is that I think there may be a genetic component here, which can make empathy, in either direction, somewhat difficult. From my perspective, the question is who wouldn't go on such a voyage? Are you not curious what the universe really looks like? What unknown phenomena or other curiosities are out there? To me this is literally the meaning of life. Intellectual curiosity, challenging yourself, adventure. Not to mention that finding a place where your vessel could settle would mean being able to start an entirely new branch of our species created with the wisdom of and knowledge of a species' existence of efforts beforehand. I think all of these urges played a critical role both in our evolution and our global expansion.
Beyond this there are also more material motivations as well. Of course there will be people simply seeking a better life, and a demographic that's yet to be created is those seeking immortality. Relativistic travel enables the possibility of traveling 'into the future'. People throughout time have engaged in all sorts of behavior to try to extend their lives. Relativistic travel is perhaps the most likely to achieve such ends since it would enable access to future technologies. In the future I'd expect to see many of the wealthiest on Earth directing a disproportionate amount of their funds to space technology to this end. This could even be happening in the present, but that'd be beyond the realm of even wild speculation.
> if they're anything like humans, there would probably be a few crazy beings who would do it just to do something extreme, but aside from escaping a dying world, i can't see any reason why such a journey would be attempted at scale.
How about the promise of future prosperity for whatever your group was, having a whole planets resources at your disposal? If we look at human history it's full of mass migrations, the colonization of the new world (original and 16th century) and the migration period (https://en.wikipedia.org/wiki/Migration_Period) come to mind. These weren't just a few thrill seekers but hundreds of thousands/millions of people.
Even if technological life is very uncommon, even if civilizations which colonizes the galaxy are uncommon among technological civilizations, even if galactic colonization is extremely slow and limited, on astronomical timescales it would still be trivial to colonize essentially every star in our own galaxy. From this we can conclude that there have been no colonizing civilizations in existence in the Milky Way at least prior to a few hundred million years ago because otherwise they would be everywhere including here (Earth, our Solar System). So either long-lived colonizing technological civilizations are vastly uncommon to an incredible degree (due to some internal or external factor limiting their longevity, perhaps), technological civilizations are far more alien than we could imagine, or humans happen to be one of the earliest technological civilizations in the Milky Way.
Nothing in Fermi's paradox requires technology or physics that doesn't exist yet, it primarily relies on time. A million years is a long time for a technologically advanced species, ten million, 100 million, or a billion years is an unimaginable eternity. Even at slow travel times and very "half-assed" levels of colonization (taking thousands of years between founding a colony and sending out only a handful of new colony ships) the sheer amount of time in play allows for quite thorough colonization of the entire Milky Way.
even if civilizations which colonizes the galaxy are uncommon
Colonizing the galaxy requires technology that does not exist yet. Even putting a single live human temporarily on Mars requires technology that does not exist yet.
Pressure vessels, life support systems, rockets, what exactly doesn't exist yet that is needed, technologically?
If you want to be a pedant and say that any specific tool that doesn't exist yet represents technology that doesn't exist then sure, that's the case, but there's nothing especially beyond state of the art that is required to live in space or colonize other planets. Technological advancements are mainly advantageous in increasing the success rate and cost efficiency of doing so. But we could have sent people to Mars in the 1970s. We had the rockets, we had the know-how to build the vehicles.
This makes me wonder about the details of such a sterilizing event. How would it actually work? Say the Earth was in range of a supernova explosion, or in the path of a GRB. How would we go out? Would the planet be thrown off its orbit and wander away from the warmth of the Sun, letting us die a slow, freezing death? Would the planet simply be vaporised? Would the atmosphere be incinerated, and anything below it suffocated for lack of oxigen, or maybe burnt by unfiltered solar radiations? Would it leave the planet mostly there, and just destroy anything organic on it?
Would it be an instantaneous event? One moment we are there, and one nanosecond after that us and every trace that we ever even existed will be vanished. Or will it take longer? Will we feel it, feel pain, or recognize that it's over, that's it?
Probably a grb would only nuke a bit more than half the planet,though. There would be diffusive, reactive conversion of the atmosphere to some nasty stuff with lots of acid rain, but that is likely to be survivable over the long term.
It is really astounding how much we can "see" what's going on out there by combining our models of the universe with our recordings of the electromagnetic waves arriving at earth.
SD: "The blast generates two jets of gamma rays which travel out..."
PR: "The blast generates two jets which travel out ... The jets emit gamma rays,..."
Implication from their creative edit is that the blast itself shot out gamma rays (photons) at light speed, whereas the paper's authors actually described something else, a decades-long process of ejecta compressing and interacting to create gamma emissions. "The long time baseline of this event offers the best available constraint in afterglow evolution as the bulk of shock-accelerated electrons become non-relativistic."
My understanding is that the famous '91 OMG particle (proton?) was theorized to have been generated by an expanding shock wave, except unlike here the scientific community then spent some time doubting their readings and being unable to re-verify the phenomenon. Conversely this new study observed such an event spanning from 1975-2017 using 7 different instruments.
Original PR: https://www.dunlap.utoronto.ca/astronomers-discover-sonic-bo...
Paper: https://arxiv.org/abs/1808.08964