Now, seriously, what would be a safe distance for an Earth like planet to be from such an unlucky event?
If you were on axis, though, anything "in" the galaxy would be at risk. Given that we see jets in other galaxies that are longer than their radii.
While that wouldn't work for heaps of reasons, I like your idea. I guess the issue would be discerning 'when' such a thing happened, and finding the right item to look back at, which would be a difficult challenge...
It has been suggested that black holes could provide this mirror, but it requires resolving not just something the size of Earth, but something much smaller, at a distance of 30 million light years +. Unfortunately you actually start hitting up against the limits of spacetime's resolution itself fairly quickly. But at least in principle, it is possible that some lucky photon has bounced off a dinosaur, and has traveled all the way out there, and all the way back to Earth, just now, that if you knew where to look in the sky, perhaps such a photon might even enter your eye now. Or perhaps there is some human out there who really has "seen" the dinosaurs. But you'd never really know.
Beyond speculation, I'm not aware of anything showing spacetime to be discrete.
> Beyond speculation, I'm not aware of anything showing spacetime to be discrete.
It is a prediction of loop quantum gravity :
In 1988, Carlo Rovelli, Lee Smolin, and Abhay Ashtekar introduced a theory of quantum gravity called loop quantum gravity. In 1995, Rovelli and Smolin obtained a basis of states of quantum gravity, labelled by Penrose's spin networks, and using this basis they were able to show that the theory predicts that area and volume are quantized. This result indicates the existence of a discrete structure of space at very small scale.
And this in turn is one of the big reasons why FTL is probably impossible: It is in essence time travel.
> The relatively rapid spatial and temporal variability of the X-ray radiation from some molecular clouds near the Galactic center shows that this emission component is due to the reflection of X-rays generated by a source that was luminous in the past, most likely the central supermassive black hole, Sagittarius A[star]. Studying the evolution of the molecular cloud reflection features is therefore a key element to reconstruct Sgr A[star]'s past activity. The aim of the present work is to study this emission on small angular scales in order to characterize the source outburst on short time scales. We use Chandra high-resolution data collected from 1999 to 2011 to study the most rapid variations detected so far, those of clouds between 5' and 20' from Sgr A[star] towards positive longitudes. Our systematic spectral-imaging analysis of the reflection emission, notably of the Fe Kalpha line at 6.4 keV and its associated 4-8 keV continuum, allows us to characterize the variations down to 15" angular scale and 1-year time scale. We reveal for the first time abrupt variations of few years only and in particular a short peaked emission, with a factor of 10 increase followed by a comparable decrease, that propagates along the dense filaments of the Bridge cloud. This 2-year peaked feature contrasts with the slower 10-year linear variations we reveal in all the other molecular structures of the region. Based on column density constraints, we argue that these two different behaviors are unlikely to be due to the same illuminating event. The variations are likely due to a highly variable active phase of Sgr A[star] sometime within the past few hundred years, characterized by at least two luminous outbursts of a few-year time scale and during which the Sgr A[star] luminosity went up to at least 10^39 erg/s.
Edit: Older image: https://www.chandra.harvard.edu/photo/2007/gcle/
But, darn it, now we're going to have to map the cosmic background light pollution. :)
Huge bursts of concentrated energy coming out of black holes are usually tight beams of high energy particles and light (x-rays, gamma rays) moving very fast and aligned with the object's poles. The focused beam of energy is what is deadly to life. If it's not tight and focused and moving fast, the energy dissipates out into space.
The solar system is huge and extends in three dimensions. A burst of energy that hit earth directly could miss Mars (or the moon, or the space around the earth and the moon) entirely. To sterilize a specific planet, the event has to be close (within like 10,000 light years I seem to remember reading) and the poles of the object undergoing the event have to be pointing at the planet.
Compared to interstellar distances, our solar system is tiny.
It seems to me that the long term payoff of colonizing Mars is huge.
The long term payoff of colonizing remote and inhospitable areas on earth is many, many orders of magnitude lower.
I can maybe rationalize that effort if we simply assume that those areas are similar enough to Mars that the experience and technology developed while doing it could be applied effectively.
But I'm not really convinced that most of that experience will transfer - The requirements to make a self-sustaining ocean colony or artic colony are wildly different from the tools and experience we'll need for Mars. At best we gain some general insights, but we'd still have to spend enormous resources developing the right tech and tools for Mars.
Doing these things are still ludicrously ambitious projects, and yet colonizing Mars is at least an order of magnitude more ambitious.
Not true for "is/was there life on other planets in the solar system".
For Antarctica (which is not the Arctic, but I assume what you meant - Scandinavia is quite self sustaining!) you have the Antarctic Treaty System.  The TL/DR there is that pretty much every form of development in Antarctica is illegal, and you're not allowed to leave any waste whatsoever. When an antarctic researcher is on a mission, they're required to bottle up their feces/urine and bring it back to base. The urine is processed and then returned to the sea. Feces are generally returned to the host nation for local removal. Mining and other industry is expressly prohibited.
But something even more interesting is comparing Antarctica to Mars, even ignoring the treaty system. Mars has two big things going against it: radiation, and a negligible atmosphere. That means you need to limit your exposure outside, and when you do go outside it needs to be with appropriate equipment and clothing. Of course the exact same requirements also hold true of Antarctica, though to a lesser degree.
But it also has quite a lot of things going for it. Mars day/night cycle is identical to Earth and it even has near identical seasons owing to a near identical tilt. Antarctica, by contrast, has what is basically a 6 month long day/night cycle. And the weather is absolutely vicious. There are genuinely violent snowstorms, as well as temperatures that average -30F, and much lower on the inner areas away from the coasts. By contrast temperatures on Mars (depending on what part of the planet you're on, and when) can get right balmy. Summer on the equator? It gets up to about 70F, though the nights are still extremely cold owing to no atmosphere.
But the snow storm part is one of the more interesting comparisons. Maybe the biggest thing is "The Martian." The key plot event there was a terrible sand storm on Mars ravaged their base and setup the plot for the rest of the film/movie. The Martian itself is a hard sci-fi book. This is one of the very few things that was intentionally faked. The worst sandstorm on Mars would feel like a slight breeze owing to the negligible atmospheric pressure. Think about that - a hard sci-fi book had to resort to fantasy to create a meaningful disaster!
There's a lot more to say/compare as well, but this is already getting a bit too long. Suffice to say, these issues are extremely counter-intuitive, but also extremely interesting to explore!
 - https://en.wikipedia.org/wiki/Antarctic_Treaty_System
I think of Biosphere 2, where trees fell down because we didn't know that we didn't know that wind is required to make trees strong enough to support their own weight. I'm sure there's a lot more we dont know that we dont know.
But I mean more of a self-propagating civilization, a group of people learning to draw on the resources throughout the solar system to stay alive and raise the next generation. More about building a dynamic growing system than a perfectly balanced one. To raise a solar-system sized super-organism of humans. The space termite mound.
One can imagine a Mars that's been terraformed and grown to a population of 1 billion people in the very distant future. But at that point I expect most of the mechanism of technological civilization to live inside AIs rather than human heads.
If you imagine a colony of just 1 million people on Mars that's pretty doable in the medium term. But it's only a very narrow range of disasters that would reduce Earth's population to less than a million and not also spill over to wipe out Mars's more fragile civilization as well.
We have no idea what Type II or III adversarial civilization will be able to do to us, and how fast.
Every time somebody says that, I remember of this:
The devastation won't reach 'Known Space' for thousands of years, but the alien Puppeteers that funded the trip are paranoid herbivores. They immediately start a mass exodus of their whole species out of the galaxy, causing a massive economic crash along with many effects on other plot lines.
Niven's Known Space future (and past) history is an amazing and incredibly influential achievement. Highly recommended. Most of it consists of collections of short stories and novellas written over decades, so it's very digestible.
If only Spiro T. Agnew would have made it.
I suspect that Niven and Fillmore have roughly equal name recognition, though, simply by the nature that Niven is still alive, and appears to be more consequential long term.
(It would be interesting if he ever wrote the story set in this universe, after the modern times, in which humanity gets out to space, and, uh, hey guyz, magic kinda... works out here... what the heck? It wouldn't necessarily take long to figure out what the deal is with Earth being a dead zone, but it would cause some interesting political upheaval as suddenly the sparse space colonies that nobody thought were worth anything and barely even worth the effort became industrial powerhouses as the only place where magic works... and not just the tame, dying magic of Niven's stories, but the original wild, abundant magic the stories claimed Earth initially had.)
Being outside the US I never covered past US presidents in school.
"Jerry Pournelle named Bureaucracy as his game of the month for October 1987, stating that he and Larry Niven became "engrossed""
It's a fun little romp.
The book is good, of course, but it doesn't approach the brilliance of the movie.
Rendezvous with Rama would be an AMAZING movie. I only hope SyFy doesn't get to do to it what it did with Childhood's End.
37 years * 365 days = 13,500 days
universe has existed for 13.5 billion years
So each day in a middle aged life is 1 million of the universe's years.
I like it ! :-)
* This flare: Last Friday
* Dinosaur extinction: 3rd of August
* Pangea breaks apart: about Valentines day
* Earth formed: June 2007
* Universe Born: 1982
Of course this means the Universe would have listened to Flock Of Seagulls as a kid, and loved Knight Rider.
* 1982: 3.2 seconds ago.
So: earlier this week, more or less.
Also if there was any form of life orbiting a star in the path of this flair, is it safe to assume that said life is no longer alive? At least if that life resembles us in its tolerance (or lack thereof) for radiation.
Based upon a couple other articles I read  , it sounds unlikely there were other galaxies or smaller structures in the path of this flare. I only see references to a very directional cone at the poles of the Milky Way, and the cone only intersects a trail of gases left behind by the Magellanic Stream.
Were there somehow orphaned planets, solar systems or smaller galaxies in the path of those cones not mentioned in the articles however, then the gamma rays, X-rays and highly ionizing gases in those cones of energy would certainly strip away most if not all of the atmosphere of any Earth-like planet, and kill all forms of life as we know it unless it was in some kind of weird, tidally-locked configuration that kept one side always facing the originating, ejecting side of the cone.
These flares would make a great plot device setup for a story in the Xeelee Sequence or /r/HFY. We find out the flares are deployed as weapons, used as a kind of galactic-scale sawed-off shotgun against another galaxy. Or the flares are galactic-grade energy reactor experiments gone horribly awry, and are the cause of one Great Filter at the Kardashev Type-III scale.
Possibly as a) some kind of bet to hide from other civilizations and b) to delay the heat death as long as possible.
Now if we could only restructure our implementation of capitalism to be pinned to advancements towards resolving physics questions to survive those kinds of timescales and challenges instead of locked down to a single planet's worth of baryonic matter and cognitive capacity...
The exact numbers are not quite exact, although they are usually in the right ballpark. "We are 30,000 light-years from Galactic central point." But I found it so useful knowing that song over the years.
26000 light years