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# Monthly Archives: April 2015

## Prime Number Magnitudes

I am responsible for some of the authentication features in our products and these features use prime numbers. People often have basic questions on prime numbers, such as:

What happens if I choose the same prime number as someone else?

Are there enough prime numbers? Continue reading

Posted in General Mathematics, software
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## Temperature Sensing and a Current Ratio of 17

One of the most common diagnostic functions requested for an electronic system is to measure its own temperature. We want to know the hardware temperature when a problem occurs because many system characteristics are affected by temperature and temperature may give us a clue to the problem's root cause. Continue reading

Posted in Electronics
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## Reasonable Budget Plan for a Young Person

In my role as annoying father, I regularly talk to my sons about financial matters and this post summaries a recent discussion on budgeting. One reasonable goal for a young person's budget is called the "60% solution". Continue reading

Posted in Financial
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## Computing Percent Differences

I have recently been computing a lot of percentage differences – mainly in variance calculations. I have been using the formula that I was taught in 7th grade and recently discovered that this formula fails miserably when dealing with negative quantities – I had never considered what happens when the O variable is negative. Continue reading

Posted in Financial
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## Lighthouse Visual Ranges

Yesterday, I received a question from a reader who was puzzled by a web page written by a flat earther that presented a seemingly rational argument in favor of the flat earth position. In a nutshell, the flat earther's argument says that to see a lighthouse at long distance on spherical Earth would mean that you would have to be able to see around the horizon. Therefore, the Earth must be flat. I may be mischaracterizing their argument, so you may want to visit web sites that go into the details of the flat earth rationale. Of course, I argue that refraction can literally allow you to see "around" the horizon. Continue reading

Posted in optics
17 Comments

## Earth With All the Ice Melted

Last night, one of my sons and I discussed using R to process geographic data. Related to this topic, we also discussed was how to visualize the impact of global sea level rise on certain countries. The video below does a good job showing what would happen if all the ice on Earth melted, which would raise sea level by ~70 meters. Continue reading

Posted in General Science
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## Return Loss of a Glass-Air Interface

I received an email today about a deployment issue that involved the reflection of light from unterminated connectors. When light travels down a fiber and encounters a change in the index of refraction, part of the energy will reflect back toward the transmitter because of a phenomenon called Fresnel reflection, which I define below (source). Continue reading

Posted in Fiber Optics
2 Comments

## Space Station Math

I read an article this morning on a space station proposal concept from United Space Structures (Figure 1). I find it interesting that so many proposals for space station structures are appearing now. These proposal appear to be driven by recent discussions of asteroid capture , sending a married couple on a Mars flyby, and a Mars surface exploration mission. Continue reading

Posted in Astronomy
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## Natural Nuclear Reactors

I read an interesting article today about the natural nuclear reactors of Oklo, Gabon. I had first read about these reactors in a Scientific American article back in 2005. The article I read today was interesting because it did a good job presenting some of the key numbers related to uranium isotope ratios on Earth, how the uranium got here, and how natural nuclear reactors could have formed ~2 billion years ago, but probably not today. Continue reading

Posted in Geology
2 Comments