hi Michael,
thank you,
I understand the mechanics of what is going on,
the equasions are the tricky ones, and I shall be trying to
work it out, still studying,
regards,
Peter.
I, on the other hand, understood the equations but not the mechanics (at least until I read the Wikipedia page) . There's always something more to learn, isn't there?
I'm slowly working my way thru Nick Strobels online notes as recommended and have gotten stuck on the problem of howto work out on solar day on Mars.
I understand and can follow the calculations used in relation to earth.(Well i think I do). I used Excel to create the various little formulas to check and get correct answers. but when I try substituting in the Martion figures I come out with 24h45m instead of 24h39m.
i have included my workings so maybe someone out there can point out my errors and/or explain why my thinking is wrong.
Nick Strobel states " The extra angle any planet must rotate on its axis to get the Sun back to the meridian equals the angle amount the planet moved in its orbit in one sidereal day."
So therefore if Mars has a Solar Year of 686.98 Earth Solar Days it would move 360deg/686.98 = 1.908278 deg so should have to spin 1.91 deg more to complete a Martian solar day.
If mars spins at a rate of 14.62048 deg/hr or 1deg/4.103833min
so that would mean mars would have to spin for an extra 7m 50s
therefore solar day = 24h37m + 7m50s = 24h 45m.
I have attached a copy of my workings in excel which may/maynot help.
in earth1 I use 1deg as the value for the extra angle earth travels for a solar day and Earth 2 uses
I hope I have explained myself and you can follow my above assumptions and my calcs as per attached.
I have spent lots of hrs working on this so before I go total stir crazy i thought I would ask.
So therefore if Mars has a Solar Year of 686.98 Earth Solar Days it would move 360deg/686.98 = 1.908278 deg so should have to spin 1.91 deg more to complete a Martian solar day.
It looks like that's your problem John. 360/686.98 is 0.524032722 so you need to add 2.150542777 minutes or 2' 9"
Thanks for pointing that out, much appreciated, but its a typo and it should read 686.98/360 which does give me 1.91
Unfortunatly your answer of 0.5240 does give the correct answer but just confusses me even more as to why it would be 360/686.98 instead of 686.98/360.
686.98/360 should be the deg amount mars would move in its rotation around the sun which should be the extra amount mars would need to spin to complete a solar day, according to the statement "The extra angle any planet must rotate on its axis to get the Sun back to the meridian equals the angle amount the planet moved in its orbit in one sidereal day."
I will need to sit and contemplate that for a bit more I think.
I see the error of my ways now, and I hope every one else reading my last post can stop laughing at my dumbness.
Unfortunatly that was a typo that Andrew pointed out and it was supposed to read 696.98/360 which I for some reason, which has escaped my for the moment, was thinking that was how to work out the angle.
Andrews post only confussed me even more by giving my the correct answer using, what at the time seemed to me to be the wrong formula.
Finally last night I saw the flaw in my logic and alls good.
I'm pretty happy so far. Been trying to get the algebra back on track, I seem to be getting there.
Going through http://www.astronomynotes.com/ slowly. A couple of nights ago I decided to try and work out the parameters of a simplified Hohmann orbit from Earth to Mars. I got close enough in my predictions to the flight times of the MSL to conclude that I got my calculations right!
I guess the proof will be in the pudding, but I'm hoping that by the time the course starts I might be almost ready.
Just signed up . Was umming and uhhing about doing this as I already have a lot of study for work. But I know I'll regret it if I don't take the opportunity.
I have just signed up for this course (Intro to astronomy); I am looking forwards to learning some great science. Of course we should keep this thread up and help each other.
I have also signed up for a course at edX (Introduction to solid state chemistry) which starts next week and have have enrolled at another Coursera couse that looks interesting, The science of gastromony
I am interested in joining this course but I'm unsure exactly how Coursera works. Is it flexible in the way that if I was to join but then a couple of weeks later I was unable to continue, I am able to just stop submitting work?
I don't want to join and then later on start stressing about completing the work in time
I would imagine that the course has to be completed in the 9 weeks alotted, but I've never done a coursera course before.
Do they have a 'contact us' page where you can pose this question?
You could always start this course, not complete it but get all the course material - study at your leisure and then apply again for a subsequent set of dates to finish it - you won't lose any money
Did everyone else receive the following introductory email?
Quote:
Hello, and welcome to Introduction to Astronomy. Our class starts in only one more week, and we are all excited here at Duke. As we count down the days to our launch, I wanted to thank you for undertaking this journey with me and share a few things.
This class is intended for students with little or no prior knowledge of astronomy, and we assume only a familiarity with high school level algebra. If you are not comfortable with algebra or it has been a while since you last did any math, you may want to consult one of the math reviews listed below. We will try to introduce all of the physics concepts we use but these introductions will be brief. Some sources for a review of physics topics are listed separately. In general, the more you know the more you will get out of this class, but if you are able to put some work in you should be able to follow the lectures, and do the homework, without much prior experience.
We will not be following a particular textbook, nor will we produce detailed notes for the class. The PowerPoint slides are written to serve as skeleton notes - equations written by hand into the slide on the video will be reproduced in the next slide so you have a record, for example - and we encourage you to produce your own more expansive notes. There are many standard textbooks in many languages that cover roughly the same material we will cover, and you are encouraged to read any of these along with our class. The online Wikibook General Astronomy covers much of the material we cover although the treatment of gravitation, for example, is not as rigorous as what we will do.
In the early weeks of our class we will make heavy use of a simulation tool called “Starry Night.” You can purchase a version of this software that turns your computer into a planetarium at starrynight.com or you can find a similar, free simulation tool at stellarium.org. These simulations are fun and can help you understand the motions of the sky as well as identify what you see in the sky.
There will be weekly homework sets, designed to help you deepen your understanding of the concepts we are covering. Your grades on these will be the basis for the final course grade; there will not be any exams in this class. Even if you are not interested in a grade, we encourage you to work on the problems. At least half the fun of science is doing it, and this is your opportunity. Collaborating with others on these problems is encouraged: that is how science is done. The weekly forums provide a way to do this. If you simply copy down answers from the forums, however, you will not achieve the kind of understanding that comes from thinking through a problem on your own before and after discussing it with others.
The forums are your way to communicate with other students about the class. Having thousands of colleagues worldwide is one of the exciting aspects of taking this new kind of online class. They are also your way to communicate with course staff. Please do not try to contact us directly. Although the opportunity to hear from over 48,000 of you the world over is one of the exciting part of the class for us, the sheer number makes direct communication impractical.
We would like to know some things about our students, so we can better adapt this class, as well as further offerings, to the audience we attract. To this end we ask that you fill out the survey at https://duke.qualtrics.com/SE/?SID=SV_eRJeXDURv5as26F. This is not required, should not take more than 5 minutes, and the information you provide will be used only in aggregate ways that do not identify you personally. In particular, your answers will have no bearing on this or any other Coursera class you might take.
Thanks again, and I really hope you enjoy this class!
ronen
For those who are a bit worried about the math, there are links attached at the end of the email to pdf documents that review some of the basic math concepts used in Astronomy.
. There's always something more to learn, isn't there?
. Was umming and uhhing about doing this as I already have a lot of study for work. But I know I'll regret it if I don't take the opportunity.
