North Korea's nuclear bomb test

I'm not a big fan of politics, but part of the story about North Korea's second nuclear bomb test caught my eye.

North Korea announced its underground nuclear test a little more than an hour after the U.S. Geological Survey reported a magnitude 4.7 seismic disturbance at the site of North Korea's first nuclear test. --CNN

And sure enough, here's the earthquake data from the USGS.

C-14 anomalies and solar fluctuation

So you know how you learned in high school about carbon dating be a super reliable way of measuring the age of things, since the amount of C-14 in organic material decreases at a steady rate?

They lied.

The amount of (mildly) radioactive Carbon-14 in organic materials does slowly decrease. But exactly how slowly or quickly depends upon two additional factors: how much C-14 is present in the atmosphere around that sample, and how much the C-14 is also triggered to decay. And fascinatingly, it turns out that the Sun of all things influences both of those!

Specifically the Sun's neutrino output. Neutrinos are high energy but low mass particles that the Sun creates in the process of nuclear fusion. When these particles collide with Nitrogen-14 in the atmosphere, they cause the N-14 to convert to C-14. Therefore if there's more neutrinos coming out from the Sun than usual, we'll have more C-14 than usual, so C-14 will appear to decay more slowly than usual, so in order to get a large amount of decay we'd need a super-large amount of time, so (if we assumed it was decaying at the same rate as usual) we would be estimating times too short.

On the other hand, there's a competing effect too. C-14 naturally decays, however it can be stimulated to decay faster, and in fact neutrinos can do this too. So if htere's more neutrinos coming from the Sun, C-14 will be decaying faster than usual, so to get a large amount of decay we'd need only a small amount of time, so (if we assumed it was decaying at the same rate as usual) we would be estimating times too long.

Now here's what's interesting. If we compare the ages of trees based upon carbon dating to their ages based upon tree rings, we can try and calibrate the rate of C-14 decay to what's really happening. While the authors of the linked paper didn't specify which of the two effects dominated (that is, it's unclear to me if excess neutrinos would result in MORE or LESS C-14 overall, and thus over- or underestimate the ages of trees using C-14), they did say that there's a 200-year period to the "anomalies" in carbon-dating results as compared to tree rings. So if the anomalies are caused by the Sun's neutrino output, that means that the Sun's nuclear fusion (which creates the neutrinos) is varying on a 200-year cycle.

Why hello, Mr. Variable Star!

Pop Quiz!

I heard someone's cellphone go off, so it's time for a pop quiz. Or if you prefer, think of it as a thought experiment. It's two questions. Answer me the best that you can, and explain your reasoning.

1) A tunnel is drilled straight through the Earth, straight from one side to the other and through the core. Let's suppose the tunnel is given strong enough walls that it doesn't collapse, and that it's well insulated so it isn't too boiling inside. A tourist sees this gigantic hole and decides "hey, there's no bottom to hit, so it's gotta be safe to jump into it," and follows word with deed. (a) Where does he end up? (b) If he could stop at the middle, what would be his weight there (as compared to his weight standing on the surface)?

2) Same tunnel through the Earth, this time you can walk along it with a barometer, reading air pressure throughout the tunnel. When you get to the center, will the air pressure be greater than that at the surface, the same, less than the surface, or entirely zero?

Greenhouse calculator

Made by the Aussies, it's a greenhouse gas calculator - it determines how much CO_2 you produce in a year (3 tonnes per year per person is the sustainable amount, 24 is the average Aussie), and therefore when you should kill yourself so you don't use more than your fair share.



I produce 15.0 tonnes of CO_2 per year (according to their calculator), and therefore I should die at age 15.4. At least I'm better than average! :-P

ID and religion

I know there's a few readers of this blog who believe differently from how I do on "hot topic" issues such as global warming, Intelligent Design, and conspiracy theories. For those of you who believe in Intelligent Design, I'm curious, do you feel that ID is creationism and is a religious belief, or do you think it is a scientific theory with tangible proof to support it?

Earth-like Planets commonly form, says Spitzer study

Spitzer (the "IR Hubble") scientists have recently put out an interesting paper implying that the majority of Sun-like stars may form Earth-like planets. (Hat tip to the Bad Astronomer for the head's up.) They studied a set of 300 Sun-like stars and the dust around them - dust glows in the infrared, so Spitzer easily sees it.

The color and brightness of the glowing indicate the temperature of the dust. The temperature of the dust is only (essentially) affected by the light from the parent star, so the temperature depends on the distance from the star. So by looking at each star, even though they can't actually resolve the disks they can from the *color* of the disk determine how the dust is distributed around the star.

Next thing they did is determined the age of the stars. I'm less clear on how that was done, since Never mind, I read the actual article (PDF), and they say "Ages for these stars were estimated from pre-main sequence evolutionary tracks, as well as kinematic association with groups of known age (e.g. Mama jek et al. 2002)." I'm actually a little skeptical about this, since those methods also rely on the color and brightness of the star/disk (since we cannot resolve the two separately), so it seems like circular reasoning to me. I ended up posting a question about this on the Bad Astronomy blog to see if I can get any response.

One thing I'm skeptical about is the method they used to determine the age of the stars. For the most part the stars and the disks cannot be resolved. They get information about the disk from the IR spectrum of the star/disk combination. They get the age of the stars (according to the actual paper) from evolutionary tracks on the HR diagram - which rely upon the spectrum of the star/disk combination. Isn't there some circular reasoning there? Or are the evolutionary tracks based upon the visual spectrum and we're able to assume the visual wavelengths are entirely uncontaminated by the disk?

However, let's move on. Assuming they know the disk description, and assuming they know the age of the star, and they selected stars that are all like the Sun, they can then track how the disk changes with the age of the star. They clearly find that the disk thins out at an Earth-like orbital radius as the star ages. One possible explanation of this is that an Earth-like planet formed and cleared out the dust (by accreting it). It's also possible that the dust was just blown out by the stellar wind, but I am under the impression that the study ruled this out - that dust around and Earth orbit is preferentially dissipating as the star ages, not that all dust is dissipating which would be the result of a stellar wind.

So the conclusion: nearly all Sun-like stars form Earth-like planets. Very interesting. We have yet to *see* these planets, but there's evidence they may exist.

Why to Take Action

Summary: We can't ever know for sure what the future holds. What we can know is the worst case scenario. If that scenario is bad enough, then we MUST take action to reduce that risk, regardless of what the chances are.



Let's say you're handed a gun with six chambers. You have no clue how many bullets are in the chambers. You are told we have to put the gun to your head and pull the trigger. You have the choice to either (A) do it now, or (B) first pull the trigger once while pointing at the wall, then spin the chamber and point the gun at your head. Which do you do? Of course you should fire at the wall first - if it was an empty chamber you spin it and then point it at yourself, losing nothing; if it was a full chamber you have emptied it, spin it, and then point it at yourself and have gained one additional empty chamber.

What if you were told you could either (A) pull the trigger now, or (B) take 10 lashes, empty one chamber, and then point it at your head? I would still take choice (B). 10 lashes will not kill me. I have no clue how many bullets are in those six chambers, it could be that they're ALL full and my only chance of survival is emptying one of them in exchange for the lashes. It's not worth that risk of my life, so long as the cost (10 lashes) is not enough to kill me either.

That's what this guy is arguing about climate change - even if we had no clue about whether it was happening, the cost of trying to reduce it just in case is so much less than the potential consequences, that we must take that choice.

And there's his various replies here.

How to Destroy the Earth

In case the title doesn't say it all, here's a little quote:

Destroying the Earth is harder than you may have been led to believe.

You've seen the action movies where the bad guy threatens to destroy the Earth. You've heard people on the news claiming that the next nuclear war or cutting down rainforests or persisting in releasing hideous quantities of pollution into the atmosphere threatens to end the world.

Fools.

The Earth is built to last...

This is not a guide for wusses whose aim is merely to wipe out humanity...

This is a guide for those who do not want the Earth to be there anymore.

Best of all, the author has taken into account the new definitions of planet and dwarf planet! Go check it out.

Earthquakes

In case you haven't heard, a spate of earthquakes have hit the Sumatra region of Indonesia in the last 24 hours - more than 60 of them according to CNN. For the scientifically/geographically minded, here's a map of the region from the USGS in which color indicates how recent the quake was (red is most recent), and size of the box indicates magnitude. It's a little nuts how many of the >7 boxes there are.

FWIW, the biggest nuclear bomb ever exploded had as much energy as a 7th magnitude quake, and ever additional magnitude is more than 30 times more energy.

No significant tsunami as of yet thankfully - a 0.6m (2ft) one was confirmed yesterday, and there's rumors of a 1-3m (3-9ft) one but unconfirmed.