… but … the organization’s decided to make a change.
I’m here to not apologize for my recent absence. I started blogging a little over 7 years ago; tried it, liked it, and kept going. I had no really clear plan other than I’d do it as long as I was enjoying it.
Lately, I’m not enjoying it. (I think the technical term for it is “being in a funk”). So I’m taking a break. (It’s not you, it’s me. Continue to see other blogs. We were never exclusive)
This isn’t the first time in a funk — motivation wanes and waxes. Each time I eventually found something interesting to blog about, and posting links filled the gaps. Even as things slowed down over time — I went from multiple posts pretty much every day to eventually one post on most weekdays. In the past several years I had a pick-me-up this time of year in the form of the Science Online conference. Getting to see friends and meeting new people was a lot of fun, and there were always new things discussed in the sessions that rejuvenated me. But the organization folded last year, which is a long story, but the result is that there is no conference (which should have been happening this very week). No salvation there. It’s gotten tiresome slogging through feeds and lists looking for interesting things, and my normal fallback — ranting about bad physics reporting — just feels like it’s all been done.
There are bloggers out there who have done this longer, but I think most have not (heavily skewed by a large infant mortality rate). I expect I’ll return — someday — but if and when that happens there are no guarantees as to the frequency of my posting. We will see.
All of these are electromagnetic waves and they all travel at the same speed (the speed of light). However, they have different interactions with matter. If you are inside, your mobile phone can still get data from a cell tower since these radio waves pass through most walls. Can you see through the walls? No. Visible light does not pass through most walls. X-rays mostly go through your skin, but you can’t see (with visible light) through skin – that would just be weird.
Technically the interaction with light and matter depends on the frequency of light – but since frequency and wavelength are related, we can just talk about the wavelength.
Real scientific controversies play out in the scientific literature, through papers drawing on many other sources of data.
Phony controversies tend to play out in the media, through press releases, stump speeches, and polemical writing reshared via social media.
Somewhat related: something I wrote a while back. Each step along the way of doing the science increases your confidence, but ultimately what you need in any scientific finding is confirmation of a result.
Once the weight of experimental result hits a certain critical mass, the expectations swing away from needing data to confirm a theory to needing exceptional data to disprove it.
The Harriss spiral is constructed from rectangles in the ratio of the plastic number (1.3247…), in a similar way to how a Fibonacci spiral is created from rectangles in the related golden ratio (1.6180…). These plastic rectangles can be split into two smaller plastic rectangles, leaving a square. Recursively splitting the rectangles, and drawing curves in the squares gives this fractal spiral.
When you say we should work harder, I hear two things: 1) we aren’t working hard, and 2) we don’t think we have to. Professors seem like an easy target. We have good job security, we’re paid well, we often come from privileged backgrounds. We appear to have little to do but teach a class for a few hours a week, and we have extended vacations. It’s easy to see us as cloistered in the Ivory Tower, without much experience with the “real world” and the concerns of average folks.
The picture I’ve painted for you is incomplete, though.
The whiteness of newly fallen snow is, of course, one of its primary defining characteristics, so it’s tempting to just say that, you know, that’s the way snow is. But it’s actually a pretty good question, because snow is really just frozen water, and frozen water tends to be transparent
In each case the rolling coin has made one complete rotation. But the red arc at the top is half the length of the red line at the bottom. Why?
I have a more physics-y than a formal math-y explanation of why, which I will post soon.
OK, here’s my answer.
In the rolling case, all you have is rotation. On rotation gives you 2*pi, so it rolls one circumference.
But in the other case you have rotation and revolution (spin and also orbital motion). Going halfway around the coin gives you an equal contribution of each, so the amount of spin only requires pi rotation, and it rolls half of the circumference. If the coin’s point of contact never changed, it would still do a rotation over the course of its revolution. If the orientation stayed fixed, the point of contact would make a complete trip around the coin.
A related example of this is the moon. If viewed from an external inertial frame (where the distant stars appear to be fixed), the moon rotates around the earth every ~4 weeks. But since it’s tidally locked and always has the same part facing the earth, it also rotates once about its axis.