f' = f + fv/c !?!?

This morning I witnessed something I have never seen in my almost 23 years, a pastor using mathematical equations and graphs in his sermon. Now it really wasn't all that intense, and there were lots of pictures, but the fact remains. The subject matter was the Doppler Effect, so here’s a quick review.

When the source of wave is moving, the wavelength and frequency of that wave are observed differently from when it is not. Modeling a wave as a sine curve, the wavelength is the distance between the successive peaks of a wave, and the frequency is the amount of peaks per second. Now for any wave, the wavelength multiplied by the frequency gives the speed. Therefore if the wave source is moving towards you, the wavelength is going to be less, because in the time it takes between 2 peaks to be emitted, the source has moved a distance. Now this drop in wavelength causes a perceived, but not actual, rise in frequency by an observer that the source is moving relative to. In terms of sound waves, a rise in frequency is associated with a rise in pitch. The reverse also holds, a wave whose source is moving away from you will have a lower frequency. You experience this everyday when any vehicle passes by. You hear a higher pitch as it is approaching and a lower pitch as it races off.

So in the case of electromagnetic radiation, including light, an object moving away from you would be what we called red-shifted. That term arises because red is on the lower end of the wavelength scale of visible light. The most famous red-shifted objects are most galaxies, which Hubble discovered to be moving away from Earth, giving evidence that the universe is expanding.

So this was all an image of the spread of the Gospel. We were encouraged to be ‘redshift’ Christians, those taking part in the expansion of the Good News. So what do I think of all this? Interestingly enough, my mother had made a comment the last week on how the pastor had mentioned one’s position might be in a research lab. She said that she doubted the pastor of Dewberry, the small church in a rural area of Indiana that she grew up in, would have mentioned that. And she’s right. He we are smack in the middle of UNC, Duke, and the Triangle Research Park. The congregation of Chapel Hill Bible Church is likely significantly more interested in science than that of Dewberry. So this analogy of a red shift is simply making an allusion that the audience would understand. Jesus told parables about farming and banquets to better connect with the people. This is an example of the same thing, and it’s a pretty good example. I’ll probably remember his red shift parallel for a long time. Although I must admit I’m sure there were people who had no idea what he was talking about.

Following up the last post, brominated vegetable oil is used as an emulsifier in citrus-flavored drinks. It’s needed to prevent the citrus flavors from separating and forming a separate layer, which I’ll admit sounds disgusting. The fact that citrus drinks are emulsions is their reason for being cloudy, the many interfaces between the citrus flavors and the rest of the drink scatter light. Other examples of emulsifiers are egg yolks, used to emulsify mayonnaise, and also detergent, and soap. So given the option, I guess I’ll stick with brominated vegetable oil.