Archive for October 12, 2018

Vector Calculus Weather

Posted in mathematics, The Universe and Stuff with tags , , on October 12, 2018 by telescoper

As it happens I did a lecture today about vector fields as part of my module on vector calculus. Whenever I did similar lectures in the past I used the day’s weather map as an illustration, so this morning I downloaded what turned out to be a particularly dramatic example. The curl of the velocity field around the weather system off the west coast of Ireland this morning was definitely non-zero…

Storm Callum turned out to be not as damaging as feared. Apparently it was rather windy in Maynooth overnight, but I slept right through it.

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Hubble Problems

Posted in Cute Problems, The Universe and Stuff with tags , on October 12, 2018 by telescoper

Here I am, only connecting again.

Almost every day I get a spam message from a certain person who thinks he can determine the Hubble constant from first principles using  biblical references. The preceding link takes you to an ebook. I was thinking of buying it, but at 99c* I considered it prohibitively expensive.

*I am informed that it has now gone up to £1.30.

My correspondent also alleges that in writing this blog I am doing the Devil’s work. That may be the case, of course, but I can’t help thinking that there must be more effective ways for him to get his work done. Either that or he’s remarkably unambitious.

Anyway, to satisfy my correspondent here is one for the problems folder:

Using  the information provided in Isaiah Chapter 40 verse 22, show that the value of the Hubble constant is precisely 70.98047 km s-1 Mpc-1.

You may quote the relevant biblical verse without proof. In the King James version it reads:

40.22. It is he that sitteth upon the circle of the earth, and the inhabitants thereof are as grasshoppers; that stretcheth out the heavens as a curtain, and spreadeth them out as a tent to dwell in.

By the way, please note that the inverse of the Hubble constant has dimensions of time, not distance.

Answers into my spam folder please (via the comments box).

 

While I am on the subject of Hubble, I will mention the news that the Hubble Space Telescope is having a few technical problems as a result of a failure of one of its gyros. In fact a few days ago it went into `safe mode’ to help engineers diagnose and fix the problem, during which time no observations are being taken. I’m told by people who know about such things that the spacecraft can actually operate on only one gyro if necessary, using information from other systems for attitude control, so this problem is not going to be terminal, but it will slow down the pointing quite a bit thus make it less efficient. With a bit of luck HST will be back in operation soon.