What the Hell is Radiation Measured In?

If you're anything like me, you've been reading about the incident a the Fukushima power plant, then eventually read up a little on Three Mile Island and Chernobyl. I've noticed that whenever they talk about radiation it's always measured in some other way.

From this article:

The National Institute of Radiological Sciences said that 3.9 million becquerels per square centimeter of radiation had been detected in the water that the three workers stepped in — 10,000 times the level normally seen in coolant water at the plant.

The injured workers’ dosimeters suggested exposure to 170 millisieverts of radiation.

They measure it one way in one paragraph, then in the next freaking paragraph they measure it differently!

Well, here are all the ways radiation is measured:

Curie (Ci) / Becquerels (Bq)

Curies/Becquerels are measures of actual radioactive radiation. Curies (obviously named for Marie Curie) are the conventional unit, whereas Becquerels (named for another radiation pioneer, Henri Becquerel) are the SI unit. You know, SI, like kilometers instead of miles.

They are defined as:
1 Ci = 3.7×10¹⁰ decays per second = 37 GBq

Obviously, one Becquerel is one radiatoactive decay per second. So, every time an atom emits one tiny chunk of radiation, it is 1 Bq.

Technically, the "becquerels per square centimeter" the article used isn't really a measure of radiation, but it does provide a measurable reference for radiation.

rad / Gray (Gy)
Rads/Grays are measures of absorbed ionizing radiation. Ionizing radiation is radiation that can detach electrons from atoms or molecules. One Gray (the SI unit) is defined as:

1 Gy = 1 Joule of energy absorbed / 1 kilogram of absorbing medium -- usually human tissue
1 rad = .01 Gy

It was named for Louis Gray, who was a British physicist.

Anyway, if you're exposed to some for of radiation (X-rays, for example) that can knock your electrons loose, the amount of energy you absorb is measured in Grays.

rem / Sievert (Sv)
Okay, now it gets fun. Sieverts (named for Rolf Sievert, a Swedish physicist who apparently exposed all sorts of things to radiation) are an attempt to take the absorbed dose (in Gy) and relate it to the biological effects of the radiation.

1 Sv = (1 Gy)W
1 rem = (1 rad)W

W here is a weighting factor that depends on the type of radiation and the type of tissue being measured. Gamma rays and X-rays are going to have different effects on the same tissue.

As a point of comparison that the article didn't feel the need to provide, 170 mSv (the radiation dose the workers were exposed to) is about half of one entire year's worth of natural radiation (300 mSv). One dental X-ray is up to .15 mSv. One mammogram is .7 mSv. I, for one, wouldn't volunteer for 243 simultaneous mammograms.

Ultra Bonus Extra Radiation Measurement:
Roentgen (R)
This one... hmmm... I'm not even going to try to figure this one out. Why don't you read about it for yourself?

Autostereograms

Want a headache? Read about autostereograms.

To be able to see these images, your eyes have to pretend they're looking far away but focus on a closer object. If you are looking at the image normally, your eyes are focused and converge at the distance the image is from you. To see the autostereogram's 3D image, your eyes are focued at the correct distance, but are converged at a different distance (infinity), making the image hit your eyes at the "wrong" angle. Each eye is looking at a different part of the picture, which is why the edges never look right. Your brain sticks everything together, thinking that you're seeing a 3D image but in reality you're just looking at it all wrong.

In a simple "wallpaper" type of autostereogram, they take a repeating pattern or two to trick your brain into making you perceive them as being on a different plane than the background.

The tiger is repeated every 120 pixels, the shark every 130 pixels, and the person riding the tiger every 140 pixels. So, when your eyes go all crazy, the tiger seems closest, the shark is farther away, then the person riding the tiger is on the background plane.
Then if you mess with size and spacing and such, you can do all sorts of crazy things. For example here is a bunch of tigers at different depths. This image shows you how the spacing of the pattern affects the depth you perceive.

So of course no one wants to sit down and make these, so they made a computer program that builds these images for you. This program takes a grayscale image of the image you will see in 3D and a random dot pattern, then figures out how to adjust each reiteration of the pattern to make you see the 3D image.

And of course, someone figured out how to go too far with this.

We Should Have More States

We haven't admitted a new state into the Union since 1959! We were on a roll since the late 1700s. By the 20th century we got lazy (which is a trend for Americans it seems) and barely added any more states for quite a while. I say we should pick up the pace of the 1800s again so we can have 100 states by 2100, damnit! But first we need to make up for lost time. Dividing Texas into 8 states (none of which may be named Texas) and adding DC and Puerto Rico would be a good start.

Is Nitrogen Larger than Oxygen?

I was reading some gas saving myths/tips on the Consumerist when I came across this:

Fill your tires with Nitrogen. Nitrogen helps tires maintain the right pressure for a longer period of time as opposed to oxygen, this because nitrogen molecules are larger than oxygen molecules. So the next time you need to add air to your tires, add nitrogen.

Immediately I was skeptical. Oxygen is the 8th element on the periodic table, whereas nitrogen is the 7th; oxygen has a higher atomic mass than nitrogen. So can an O₂ molecule really be smaller than an N₂ molecule?

I had Google help me out and I found this paper. If you ask me, this guy is trying too hard to sound smart, like when people say "I" instead of "me." I mean come on, he didn't bother to subscript his 2s when writing O₂! ...Not to mention the paper is hosted on getnitrogen.org, which is the website for the Get Nitrogen Institute. (Institute?! Really??) Their whole idea is to get you to put nitrogen in your tires. I'm sure they're in some way financed by nitrogen people.

I found this on Answers.com (just as dubious as the nitrogen people):

Molecular size a bit tricky. As a quick comparison, we can use the covalent radius defined as 1/2 the distance between to identical covalently bonding nuclei. This is measured in picometers (1 pm= 1x 10^-12 m). Nitrogen's covalent radius is 75pm so the length of a nitrogen (N₂) molecule ought to be 4 X 75pm or 300 pm. A molecule of oxygen (O₂) ought to be just a shade smaller 4 X 73pm or 292pm. So an oxygen molecule is a little less than 3% smaller than a nitrogen molecule.

So, I did some more searching and came across this.

As you can see, covalent radii generally decrease across periods in the Periodic Table. And now all that high school chemistry is coming back to me.

Oh, yeah! Chemistry sucks!

So anyway, with some assumptions, I can agree that yes, N₂ molecules are smaller than O₂ molecules.

But let's back up! The whole point of this was what to fill your tires with! Who is filling their tires with oxygen?! If a tire caught fire in a wreck IT WOULD EXPLODE if it were filled with oxygen! They're filled with AIR, which is 78% nitrogen! I find it extremely hard to believe that using pure nitrogen to get that last 22% of non-nitrogen out of the air in the tires is going to be worth the time, effort, and money. Just check your tire pressure regularly, damnit.

Most of the other tips check out, but some of that original article is crap. For example, "Shopping around for cheaper gas DOES NOT burn more than you’ll end up saving." That depends on how far you need to drive to shop around, doesn't it? "Gas is NOT cheaper mid-week." Depends on the gas station, doesn't it? "Opening the windows instead of using the air conditioner has no measurable effect." No measureable effect?? Then what did the MythBusters measure?! (I'll save you the Google search: It is more fuel efficient to use air conditioning when the car is traveling approximately 50mph or more. Otherwise, windows are more fuel efficient.)

Earthquakes!

Mike O'Meara believes the Earth is crumbling as we speak, due  to all the earthquakes (and now volcano).

I decided to see what the USGS had to say. They have publicly available databases, so I plotted the amount of earthquakes greater than 5.0 on the Richter scale by year:

As you can see, 2007 had the most earthquakes since the beginning of the available USGS data. However, since this year is only one-third over, I multiplied this year's earthquakes by 3, producing the Projected result: more earthquakes than ever! This works on the assumption that earthquakes in the rest of the year are as often as they were in the first third.

But are they getting more severe?

Here, we have the magnitude of the earthquakes over 5.0 from 1973 to 2010. I made a rolling average to smooth out the data a little. It doesn't seem like the earthquakes are getting worse over time, fortunately.

So there's my cursory scientific analysis of earthquakes: we may have more this year, but they're not getting worse.