Ranking the Brightness of light bulbs, in basic resistor circuit

 This was a collaborative problem for the seniors. They had a network of 13 resistors, which represented identical light bulbs, and had to determine the currents through each one and rank the bulbs from brightest to dimmest. But how can you find the relative fractions of the total current in each bulb? 

This video shows how to think it through, using our usual 5 rules for resistor circuits: how to do series and parallel resistances; Ohm's law, V = IR; and Kirchhoff's two rules: In series voltages of the resistors add to the battery's voltage, and in parallel the currents in the branches add to the total current. 

We use each of these rules to figure this out. If you can understand this, then you likely have a really good conceptual understanding of resistor circuits!! 

6 Questions Physicists ask when evaluating if a claim is correct

To many, science is the process of discovery and trying to find the 'facts' of how the world works. It is supposed to be unbiased, nonpartisan, and pure. But don't ever forget that science is done and practiced by human beings, all of whom are imperfect, have biases, and make mistakes, just like everyone else. We are not 'all knowing' and have all the answers, and we never will. 

Having said this, what is the real story for how scientists go about their work? How do we know whether or not to believe a scientific claim by others? How and why should we evaluate others' work to justify their conclusions, especially when it is something important in the field or something never seen or claimed by anyone before? 

Check out this nice piece, from Symmetry magazine (this is very good if you like particle physics), which uses examples from particle physics to demonstrate how science is actually a little messy, but most importantly human - and 'facts' in science do change! Scientists are willing to change their minds over time as new results, often the result of new technologies and methods and data sets, because discovering real truth is a long, difficult process. There always is and should be debate and skepticism, but also open minds that are willing to accept new results that contradict old ones. There needs to be an open process or peer reviewed publications and presentations at conferences, so other experts can review a colleague's work openly and completely to check for mistakes or misinterpretations of the data. This is why it takes time to do science the 'right way.' 

Non-scientists sometimes are confused by this process, and the fact that 'facts' change in science. Perhaps the flipside of this is religion, where a particular doctrine or religious text states what is and is not, and that is not open for debate. Personally, I avoid using the term 'fact' in general because it implies absolute correctness - if we are talking about something in Nature, or something in human nature, these are both SO complex and dynamic, I'm not convinced we will ever find an absolute truth in anything! But that's OK, this is what makes science and life interesting, for me, at least!  

Excellent message from former NASA astronaut - how STEM skills, mindset and training relate to fixing humanity's problems

 Check out this post related to the UN Peace Week session Greek student Marios was part of. Former NASA astronaut and sister of Ms. Curry (maiden name is Metcalf) in the ETHS Math Dept, Dottie Metcalf-Lindenburger, is a former teacher and astronaut who had a mission to the International Space Station. She gives replies to the important questions of how being trained as a scientist and having that sort of mindset, values and skills, overlap those that are needed by all students who want to make a difference and help solve the big problems facing humanity. Very cool stuff! 

Mind blowing size for our Milky Way galaxy!

 If you had asked me yesterday about how wide is the diameter of our Milky Way galaxy, or most galaxies since ours is pretty 'average' and typical, I would have said something like 200,000-250,000 light-years. That has been the number astronomers have been thinking for some time. 

But new research, technology and tools have greatly changed this value. The Milky Way is now measured to be 1.9 MILLION light-years in diameter! Wow! For just one galaxy. Check it out.