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Comment: Re:Looking Down the Barrel (Score 1) 284

by mbone (#48462437) Attached to: Complex Life May Be Possible In Only 10% of All Galaxies

As I understand it in order to sustain catastrophic, life eradicating damage from a GRB you need to be looking directly down the "barrel of the gun" so to speak, or rather directly in the line of fire emanating from the star's poles. This forms a fairly narrow beam of intense energy that decreases with distance. It doesn't seem that likely to me that 90% of life supporting planets in the universe would find themselves in just this predicament.

Yes, but all of the GRB we see are "looking down the barrel" and so the statistics already take that into account. (In other words, if each GRB irradiates 1% of the sky, and 100 go off "near" you, you are still likely to be in deep trouble.)

Comment: Re:I am dubious (Score 1) 284

by mbone (#48462425) Attached to: Complex Life May Be Possible In Only 10% of All Galaxies

The point is really that we don't nearly know enough to answer any of these questions. We can provide "best current thinking," but with only 1 actual sample (Earth) and no experience with GRBs, these are just guessitmates at best.

I can not answer about the deadliness of GRBs, but I think you will find those answers in Phil Plaits book "Death from the Skies!".

- How many civilizations might form on bodies with very thick atmospheres, far from their Suns? (Venus does not need a ozone layer to keep the UV out, and might be very habitable a few AU out.)

Yes, insulation is a good idea. But the planet will always radiate as a black body and loose energy, which has to be re-supplied by the suns radiation. The radiation drops with the square of the distance, so rather quickly. These considerations (make-up and size of planets) go into calculations for the habitable zone.

I can also imagine that a GRB comes with considerable photon pressure and might strip the entire atmosphere off a planet, or heat it to a point where it dissipates into space.

The threat model is ozone, not atmospheric stripping. With the hypothesized existence of Steppenwolf planets, I don't even think that the notion of a habitable zone is necessarily that useful, except as a guide as to where exobiologists should look first. The real question is, how many civilizations might arise on "Earth's" at 1 AU from their (G type) star, versus "warm Venus's" at, say, 2 AU. (Scale distances as necessary if you want to include other type stars, such as M dwarfs.) If this ratio is anywhere near unity, the "GRB==doom" hypothesis falls to the ground.

- How many planets might have very long rotation periods (years), so that the night hemisphere never is subjected to the daytime UV?

I think the rotation of planets around their own axis (spin) is not known outside the solar system. Generally, the spin is generated from formation of planets in the rotating protostellar disk, but interactions and changing orbits may modify the spin (Venus, Uranus).

Of course, but the real question is, how many life-bearing planets have a very long rotation period? My guess is, this is pretty rare, but pretty rare is still enough to invalidate the GRB==doom hypothesis.

- Are there rotation axis directions and orbital precession constants for planets that would keep GRB radiation mostly in one hemisphere, leaving the other to develop?

If you do not have the problem of heating and evaporation of the atmosphere I mentioned above, then yes, that is probably possible. For example if the GRB goes off from the direction of the spin axis ("below/above the solar system"). This may safe you from one GRB, but since GRBs come randomly from all directions it is not failsafe across many billion years.

- How many planets might have other special circumstances that protect their ozone (such as a lack of N2 in their atmosphere, or an ozone generating biology in their stratosphere, etc.)

Not sure. I think it is possible to come up with such scenarios as you stated, but it has to be shown that they are frequent occurrences to be relevant for changing the survival rate of complex life.

Exactly. To say that GRB==doom means that all of these possibilities must be very infrequent indeed, and I just don't see how we can say that at present. That makes me dubious about the hypothesis.

Comment: I am dubious (Score 5, Interesting) 284

by mbone (#48452303) Attached to: Complex Life May Be Possible In Only 10% of All Galaxies

I am dubious that gamma ray bursts are invariably a sentence of doom. The actual mechanism is due to the destruction of the ozone layer due to nitrogen molecules formed in the upper atmosphere; these molecules would "eat" the ozone for maybe 4 - 5 years after a GRB event, but would not (in that sort of lifetime) go from one hemisphere to another. Questions I would have include

- How many civilizations might form on bodies with very thick atmospheres, far from their Suns? (Venus does not need a ozone layer to keep the UV out, and might be very habitable a few AU out.)
- How many planets might have very long rotation periods (years), so that the night hemisphere never is subjected to the daytime UV?
- Are there rotation axis directions and orbital precession constants for planets that would keep GRB radiation mostly in one hemisphere, leaving the other to develop?
- How many planets might have other special circumstances that protect their ozone (such as a lack of N2 in their atmosphere, or an ozone generating biology in their stratosphere, etc.)

I am sure that there are others, but even these I think show that, while GRB might be bad for habitability, they need not be fatal. Note, too, that if I was running a Kardashev Type III civilization, one of my action items would be to find any possible GRB progenitors and disarm them. So, in a KIII galaxy, GRB would likely no longer be a problem; maybe that would be a good way to determine the number of KIII galaxies in the universe.

Comment: Re:Huge Change (Score 1) 41

by mbone (#48438713) Attached to: CERN Releases LHC Data

I was told, at a NSF meeting not many months ago, that CERN never makes its data openly available and never would and that US scientists should just plan on getting European collaborators if they want to work on it.

Now, if we just get ESA to start releasing the Rosetta data...

Most of the instruments (e.g. electronics) have a large US contribution. CERN operates the ring, but the instruments are "clients", which are international research teams. That was the vision of CERN after the second world war -- bring leading science to Europe, and make research in Europe attractive. Particle physics was chosen back then.

Yes, that is what I meant (and, even, what I said). To get the data you had to join one of the teams and collaborate with the other scientists in the team. Now, apparently, you don't.

Comment: Re:How about we beta test on Venus? (Score 1) 360

I ran some numbers on this, and concluded it would take a good while to cool Venus - you would have to get rid of the clouds somehow to make the cool-down reasonable, and that means an intervention beyond just the shade. There will be plenty of opportunity for note taking and even PhD theses during the process.

Comment: Re:How about we beta test on Venus? (Score 1) 360

You're forgetting one important thing: any shade large enough to provide sufficient cover for either planet will also effectively be a giant solar sail. Reaching a given location in space would be relatively cheap and easy compared to keeping it there in a useful orientation.

There are two proposed solutions to that

- have a swarm instead of a shade - i.e., lots of little shades, which makes the orbital dynamics (and probably the manufacture) of the system much easier to manage.
or
- put the shade not at the Lagrange point, but a little bit sunwards, where the solar gravity, planet gravity and the shade radiation pressure give an orbit period matching that of the planet. There, the shade can be pushed by the Sun's radiation pressure and still be in static equilibrium.

Comment: Re:How about we beta test on Venus? (Score 3, Interesting) 360

Well, an Earth sun-shade would need to block at most a few % of the sunshine falling on the Earh, while for Venus (if we want to cool the planet off this millennium) we will need to block all of the Sun's rays for a while, so the engineering is a bit more difficult. Add to this the detail that the Venus Lagrange point 1 is quite a bit further away than the Earth's, and energetically harder to reach, and I think a more reasonable conclusion is that the Earth would be training wheels for Venus, and not vice versa.

Comment: Who Knew? (Score 1) 62

by mbone (#48426171) Attached to: Google Maps Crunches Data, Tells You When To Drive On Thanksgiving

The Wednesday before Thanksgiving is a busy travel day?!? How did that ever escape our attention? I mean, aside from every DJ on every radio station, and every traffic reporter on every TV station, telling us that every year, how could we possibly find such things out if Google didn't do the heavy lifting?

Comment: Re:I see why the boson is a "God Particle" (Score 3, Insightful) 67

by mbone (#48415095) Attached to: Elusive Dark Matter May Be Detected With GPS Satellites

tt can be baryonic matter, if it is encapsulated in some fashion. I believe your two conditions refer to BBN (not a particularly extreme energy density, BTW) and the Lyman Alpha constraints on Warm Dark Matter (which means it had to drop out of the radiation fluid v ~ c / sqrt(3) pretty early).

Both of these are fulfilled by, e.g., quark nugget dark matter (these would form well before BBN and drop out of the radiation fluid well before needed to fulfill the WDM constraints), as maybe also the recently proposed "macros".

Comment: Not even wrong. (Score 4, Interesting) 243

by mbone (#48402881) Attached to: Big Talk About Small Samples

Poisson statistics. I have to wonder if Mr. Haselton has ever heard of the term.

If by some weird alignment of forces I were to become a Judge, and Mr. Haselton presented this to me in a brief, I would try and have him disbarred for abuse of statistical process. I know that the actual legal profession is soft about such abuses, but by God they wouldn't be in my courtroom.

What this country needs is a dime that will buy a good five-cent bagel.

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