Gamma-ray bursts are a threat to life

http://cerncourier.com/cws/article/cern/59937

by curtis • 11 years ago

135 86 11 years ago

tectonic• 11 years ago

Is this the Great Filter?

benbreen• 11 years ago

Certainly seems like one of them, if this claim is true: "The Milky Way would therefore be among only 10% of all galaxies in the universe – the larger ones – that can sustain complex life in the long-term."

fiatmoney• 11 years ago

Actually, filters that select on galaxy scale are unlikely to be the "great filter", because we don't seem to see any artificially generated signals coming from within our own galaxy. This particular filter does strike within our own galaxy though, just to a lesser degree.

So maybe.

moyix• 11 years ago

I thought the Fermi Paradox (and hence the Great Filter) was about the absence of life originating in our own galaxy? I don't think anyone has suggested that any species is likely be able to cross intergalactic distances.

jjoonathan2• 11 years ago

Probably not. <JeffGoldblum> Life will find a way! </JeffGoldblum>

The bacterium Deinococcus radiodurans is the best known extremophile among the few organisms that can survive extremely high exposures to desiccation and ionizing radiation, which shatter its genome into hundreds of short DNA fragments2, 3, 4, 5. Remarkably, these fragments are readily reassembled into a functional 3.28-megabase genome. Here we describe the relevant two-stage DNA repair process... figure [1]

Direct radiation exposure is not the only threatening aspect of a GRB and even Deinococcus Radiodurans can't withstand the full onslaught of a nearby GRB [2], but I do believe that D.R. is a good enough proof of concept to argue that adaptation is not only feasible but probable. GRBs would set life back a few hundred million years (whether here or in a remote galaxy), but I doubt they would put an end to it.

[1] http://www.nature.com/nature/journal/v443/n7111/fig_tab/natu...

[2] http://www.world-science.net/exclusives/070226_grb-life.htm

eloff• 11 years ago

It's tough to imagine a similar process in a complex lifeform. So it could well be the great filter. Evolution doesn't work well with things that happen rarely over geological timescales. This is one reason why life on earth is very sensitive to climate change, even although the climate has gone through many major changes in the past.

lucaspiller• 11 years ago

Let's assume this happened tomorrow, and it took another 500 million for life to evolve to what we would consider intelligent. Would anything of our civilisation be left? What would be the best way to leave a record that we existed?

pacala• 11 years ago

Just keep going business as usual. Given that we have plenty of trilobite fossils from the Cambrian, might even expect future paleontologists to find some fossilized skulls.

http://www.fossilmuseum.net/Paleobiology/CambrianFossils.htm

TheDauthi2• 11 years ago

The only problem with this is that we might not have long enough for multi-cellular life to recover. While the red giant phase is a long way off, some scientists think that the carbon cycle could shut down as little as 500 million years from now, either due to oceanic evaporation or due to a failure in the weathering process.

sneak• 11 years ago

http://en.wikipedia.org/wiki/Rosetta_Project

mc808• 11 years ago

We could launch 10,000 time capsules into space on trajectories that bring one of them back to Earth every 50,000 years or so. They would have to be designed in a way that makes re-entry spectacularly visible so they would be noticed and it would be possible to track them down. Not perfect, but at least there is some chance that one would arrive while an intelligent species is thriving.

sshumaker• 11 years ago

I think we might be earth's last chance at an advanced civilization. We've depleted all of the readily available energy sources necessary for an emerging civilization (easily-accessible fossil fuels). It will take at least 500 million years for them to be replenished. And in one billion years, the increased luminosity from the sun will wipe out most advanced life due to runaway greenhouse effects. So there's a pretty narrow window in-between.

lxe• 11 years ago

This makes a lot of assumptions about extra-terrestrial life. This article assumes that all "life" depends on a protective ozone layer and that it's similar to life on Earth.

colordrops• 11 years ago

The article doesn't assume that all life depends on a protective ozone layer. The article states several times that life like that on earth depends on a protective ozone layer.

viggity• 11 years ago

can someone comment on the legitimacy/reliablity of the "Cern Courier". The article seems legit (no tin foil hats), but that font. woof, it makes it look super amateur.

Devthrowaway80• 11 years ago

http://en.wikipedia.org/wiki/CERN_Courier

indrax• 11 years ago

Produced for CERN by IOP Publishing
©COPYRIGHT CERN 2007 for the content of CERN Courier and images and logos identifying CERN.
©COPYRIGHT IOP 2007 for the design, format and typography of the CERN Courier Web Pages, ...

The author appears to be an astrophysicist, and you may know CERN from such products as the Large Hadron Collider and the World Wide Web.

saboot• 11 years ago

I know what you mean by 'that font', you must be using chrome on windows.

Apparently it's a 'bug' in their CSS, they are aware of the issue but haven't fixed it yet, http://www.reddit.com/r/Physics/comments/2l2ijj/the_brookhav...

Steuard• 11 years ago

Speaking as a high energy physicist, they're absolutely a legitimate publication. I don't read it regularly, but the CERN Courier has been part of particle physics culture for a very long time (maybe since CERN was founded).

JumpCrisscross• 11 years ago

The authors found previously that GRBs are more frequent in low-mass galaxies such as the Small Magellanic Cloud with a small fraction of elements heavier than hydrogen and helium. This reduces the GRB hazard in the Milky Way by a factor of 10 compared with the overall rate.

Smaller galaxies are deadlier, got it. Is this because GRBs tend to emanate from the galactic centre? And larger galaxies, having more stars further from the centre, have more "habitable" space? Or does it have to do with the higher frequency of heavy elements in large galaxies? If the latter, how do heavy element concentrations cause or moderate GRB activity?

dsqrt• 11 years ago

I am not an expert, but my understanding is that long GRBs are expected as the result of the collapse of very massive stars. These stars are short lived (few million years) and very luminous. Metals (in astrophysics anything heavier than Helium) in the envelope of such a massive star would drive strong radiation-pressure driven mass losses (because of the increased opacity). Only very metal poor stars are able to remain sufficiently compact and massive at the onset of collapse to be able to trigger a GRB.

nerfhammer2• 11 years ago

They're not completely sure, but:

There are at least two different types of progenitors (sources) of GRBs: one responsible for the long-duration, soft-spectrum bursts and one (or possibly more) responsible for short-duration, hard-spectrum bursts. The progenitors of long GRBs are believed to be massive, low-metallicity stars exploding due to the collapse of their cores. The progenitors of short GRBs are still unknown but mergers of neutron stars is probably the most popular model as of 2007.

http://en.wikipedia.org/wiki/Gamma-ray_burst_progenitors

cubano• 11 years ago

I know I may get dinged for this observation, but it is something that really bothers me about certain types of forecasts...be it weather or things of this sort...

That would be the "50% forecast", which, when examined with a bit of thought, really is saying "well, maybe it did, and maybe it didn't...we don't really know but hey, doesn't 50% sound scientific!"

For sure, GRBs are scary, potentially life-wiping events, but, really..don't we deserve better than a coin-flip?

acadien2• 11 years ago

It's just statistics. You look at how often we see GRBs, how long they last (on average), how intense they are (on average) then do a big time integral and figure out the odds of a big one hitting earth over such and such a period of time. There is no better than a coin-flip, the coin flip is the odds of it having happened (by the author's approximations). If I can help explain any further please let me know.

austinz2• 11 years ago

Is the gamma-ray burst a spherical field, or is it a narrow, directed cone? If the latter, I wonder how the burst spreads/diffuses as it travels and what sort of equation governs the energy flux with respect to distance and initial conditions.

pixl97• 11 years ago

Beams from my understanding

https://en.wikipedia.org/wiki/Gamma-ray_burst#Energetics_and...

acadien2• 11 years ago

Great question! Since they're emanated in jets, the GRBs travel in a conical shape that spreads out as it travels. Check out page 19 of this paper, it has a histogram of the jet opening angle; http://arxiv.org/pdf/1101.2458.pdf

Then you can figure out the flux from the area of a circle on a sphere, which is something like 2πr^2(1−cosθ) Where theta is the opening angle and r is the distance from point of emanation of the GRB.

austinz2• 11 years ago

Thanks for the paper link! I'll check it out. (The histogram legend seems to indicate two distributions of observed GRBs, the larger centered around 8 degree cones.)

jbert• 11 years ago

Do you know if there is any bias to the orientation of the jets?

e.g. in a spiral galaxy, do they tend to align with the axis of rotation and so do less damage locally (spray out "up and down" from the galaxy)?

gmoes• 11 years ago

I think there are multiple types of GRBs and some can be spherical. Two that I have read about are neutron stars colliding and large solar mass > 100 exploding and leaving no remnant. I've read that these types of bursts can blow the atmosphere off of a planet. http://en.wikipedia.org/wiki/Hypernova

crystaln2• 11 years ago

Is this really an explanation for the Fermi paradox? Would a factor of 0.1 or even 0.01 really change the import of the Fermi paradox?

cshimmin2• 11 years ago

It is complicated by the fact that this implies intelligent civilizations have a very finite window of opportunity in order to communicate. 500 Myr is a pretty short on cosmic timescale; so the odds that:

1) our civilization comes to exist in some 500Myr window

2) another civilization comes to exist in another 500Myr window

3) Signals sent from that other civilization arrive at the right time for ours to observe them

are considerably lower than just the odds that two civilizations develop that are advanced enough to communicate with each other.

Dylan16807• 11 years ago

Those windows are pretty big. These aren't life-scouring cosmic rays, just mass extinctions. Complex life is still there, and can develop a civilization in a couple million years.

The reshuffling of life could even increase the chances of a civilization occurring. And a smart species has pretty good odds of surviving a mass extinction.

nerfhammer2• 11 years ago

Yes, because these events may have been much more frequent in the early universe

http://www.nature.com/scitable/blog/postcards-from-the-unive...

http://arxiv.org/abs/astro-ph/9901322

onion2k• 11 years ago

It's possible that gamma bursts are an example of a "great filter" - an event the stops life that Fermi Paradox and Drake equation can't really account for: http://en.m.wikipedia.org/wiki/Great_Filter

Udo6• 11 years ago

Probably not. Implicitly, the Fermi paradox looks at life in our own galaxy, which has apparently been quite lucky overall cosmologically. Many galaxies out there are hostile to life (GRBs are just one factor, I would argue that being a metal-poor galaxy with no active star formation is an even worse problem for life), but that doesn't have any bearing on life in our own galaxy - of which we have a sample size of one.

That said, even the friendly corners of the universe aren't a pony farm. It's more than likely for any given planet to find itself staring down the barrel of a stellar particle accelerator at some point during its time. Earth probably did, too, and we're still here. Whether it's a complete sterilization event depends on the amount of energy deposited. Depleting the ozone layer isn't enough. A planet would have to be pretty close to the event in order to get annihilated completely, so glancing blows with some limited impact on the ecosystem are probably more common in our cosmic neighborhood.

VLM• 11 years ago

"Depleting the ozone layer isn't enough."

Unfortunately mixing is good enough that the increased UV will sterilize everything that does photosynthesis for quite awhile, including in the oceans. So yeah its enough.

One interesting part little discussed is that in typical physics fashion, there's many orders of magnitude from weakest (barely detectable, about once a day) to kills everything on the surface not just ozone disruption (Could happen?) and as a rough guess maybe a tenth the strength happens ten times as often.

So the disaster oriented contingent wonders about wiping out all non-ocean vent life on a planet, but its more likely that as a species we'll have way more "fun" with glancing blows or near misses leading to reduced crop yields.

Sometimes I wonder about unexplained civilization collapses and GRBs. All you need to is screw up crop yields to 99% of minimum and the mayans or whatever are all done. Don't need to kill everything green or kill everything living from radiation burns, just a glancing blow bad enough to tip an already tottering civilization over... Maybe there's enough spare capacity in europe / asia that nobody noticed or recorded a 1% hit but it was enough to do the Mayans in.

edgarvm• 11 years ago

It's just an idea but I think any advanced civilization aware of threats of GRB would try to transmute from its organic form to avoid extinction.

thesz• 11 years ago

As I read New Cosmogony by Stanislaw Lem, I cannot help but think that older civilizations (gods), hated organic life very much and tried to erase it everywhere.

e0m• 11 years ago

There is a hypothesis that the Ordovician–Silurian mass extinction 450 million years ago was caused by a Gamma-ray burst!

http://en.wikipedia.org/wiki/Ordovician%E2%80%93Silurian_ext...

It stripped the Earth's ozone and killed all the surface-dwelling organisms.

analog31• 11 years ago

I wonder if 500 million years is long enough for an intelligent civilization to come up with some sort of early warning system such as figuring out which stars might be turning dangerous. The article doesn't say how long the bursts last.

has2k1• 11 years ago

The burst lasts as long as it takes the stuff (radiation) get past the planet. That is only a few seconds. That radiation is travelling at light speed so given our present knowledge an early warning system is unthinkable. However for a star big enough to go supernova, expected life expectancy and spectral analysis can give you some estimate rounded to the 10s or 100s of millions of years.

crystaln2• 11 years ago

If the Universe is too dangerous for life to exist elsewhere, what are the chances that it's not too dangerous to exist here? Not very high.

Either there is an abundance of life out there, or we are most likely just experiencing a brief period of lucky safety in a tiny corner of the Universe.

cLeEOGPw• 11 years ago

Or life is rare and can be found here and there.

I don't get it why so many people either want life to be basically on every second star or not exist outside Earth at all.

Let's just accept that Fermi and all others hugely overestimated the chances and roll with it, will be far more productive imo.

So with the GRBs in mind, we can safely narrow livable space to outskirts of Milky Way and focus our search there.

HCIdivision172• 11 years ago

I think it's generally because the balance point isn't a stable equillibrium. There's no force that encourages balance - it would have to be serendipitous. That's unlike the extremes, where a thriving interstellar civilization likely leads to mass colonization or that life is hard and typically goes extinct before then.

The time scales in these sorts of estimates are enormous, often tens or hundreds of times the span we needed to rise up. So if we even have an inkling to be expansionary (and we do), and aliens are like us in wanting to thrive comfortably (with enough space per unit being), then it's likely they too would have at least a mild drive to expand. Over mnay millions of years, even a very mild push out would fill a galaxy.

JonnieCache2• 11 years ago

Greg Egan's fantastic Disaspora begins with a GRB hitting earth. It isn't pretty. Hence the title. Best scifi I've ever read.

theoh• 11 years ago

Actually the title is "Diaspora"... Nothing to do with disasters.

JonnieCache2• 11 years ago

Admittedly I did make a typo there but the diaspora is motivated/necessitated by the disaster.

deft0nes• 11 years ago

the font on this site is a threat to life

JulianMorrison• 11 years ago

Is there any way to rapidly repopulate the ozone layer? Assume unlimited funding.

swombat• 11 years ago

So, assuming we don't also all die of burns or cancer or natural disasters caused by the sudden influx of energy into the atmosphere immediately...

According to http://www.epa.gov/ozonedesignations/faq.htm , ground ozone tends to be produced by pollutants, i.e. we are ourselves producing this ozone, mostly by burning fossil fuels.

From http://www.ozonelayer.noaa.gov/science/basics.htm , we find that 90% of that is in the upper layer, so 10% is lower layers.

So we have actually already produced at least 10% of the ozone we'd need to repopulate the upper atmosphere, we're just producing it in the wrong place...

From reading these links, it sounds like ground-level ozone is often a seasonal effect, so it could well be that a lot of this ozone is being produced on a regular basis and then dissipates in some fashion.

So... my back of the envelope calculation would be that yes, if we had unlimited funding and a bit of time, we should be able to produce enough ozone just by burning organic matter. The key question would be, can we get that ozone in the right place?

With unlimited funding, and with a deliberate effort to burn fossil fuels at high altitudes, my gut feeling would be yes... I think the key question would be would we be able to do this in time, before we all burn to a crisp along with most of the plant and animal life on Earth...

johnchristopher• 11 years ago

It's really hard to recommend one of my favourite novel this article reminds me of without spoiling the whole story :(.

jchrisa• 11 years ago

How far along the Kardashev scale do we need to before we can build a shield?

HCIdivision172• 11 years ago

At least Type I, but easily at Type II [0].

Here the trick is that a planet-scale barrier is needed, since we need to defend against tipping our ecosystem into chaos. If we're Type II, then we could theoretically just let the earth get whacked and restart using nearby systems to seed it. Kinda funny how a disaster stops being as terrible once you have backups:

Type 0: extinction

Type 1: mega-scale engineering effort to block GRB

Type 2: start over from scratch easily

[0] http://en.wikipedia.org/wiki/Kardashev_scale#Theoretical_exa...

neaanopri• 11 years ago

Does anybody know if a gamma-ray burst is preceded by an increased neutrino flux? I've heard that neutrinos will actually arrive at earth several hours before the light from a supernova. When the core of a star collapses, the light is physically prevented from coming outwards until the collapse is complete. Since the neutrinos move right through the gas, they are emitted as soon as the explosion occurs. Would detecting neutrinos be sufficient to give up ~4 hours of warning before a gamma-ray burst?

Udo6• 11 years ago

Neutrino detection in correlation with GRBs is problematic at best, because the events tend to be so far away and neutrino emissions are not expected to be focused into cones the same way EM and charged particles are, by virtue of not interacting with electromagnetic processes they'll be emitted in all directions. (There is some hypothetical neutrino/antineutrino emission within the GRB cone, but it's likely a weak signal and hasn't been measured in practice.)

We expect GRB neutrino flux to weaken far below the detection threshold by the time it gets here. Across these vast distances, neutrinos should also lag behind photons because they're not technically as fast as light.

The other question is what would we do with that advance warning if it existed? We can't do anything about the fact that our atmosphere is going to absorb these gamma rays, and chances are the event wouldn't be energetic enough to kill us directly as we're walking around so there is no point in taking cover either. The damage to our ecosystem is going to be what kills us, not radiation exposure.

saiya-jin• 11 years ago

now, nothing. In future, possibly raise some sort of (EM) shield? Of course nothing to for us/our kids, but I am sure within few millenia this would be perfectly feasible (at least my imagination wishing so :)

hanoz• 11 years ago

How useful a barrier is the earth itself for the initial burst? Would there be any benefit in arranging to be on the opposite side of it for the duration?

chrisreichel• 11 years ago

Cern Courrier are a threat to eyes.

dcre• 11 years ago

Does this mean we could look for extraterrestrial civilizations by looking for signs of planet-scale radiation shielding?

jcoffland• 11 years ago

The article lost a lot of credibility for me with it's, "thousands of millions." Apparently they think their readers are really dumb.

Gamma-ray bursts are a threat to life

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