20 Incredible Photos of a World Too Tiny to See which are awesome. But it’s a slideshow.
Archive for October, 2014
Thought experiments are common in theoretical physics today. Physicists use them to examine the consequences of a theory beyond that what is measureable with existing technology, but still within the realm of that what is in principle measureable. A thought experiments pushes a theory to its limit and thereby can reveal inconsistencies or novel effects. The rules of the game are that a) relevant is only that what is measureable and b) do not fool yourself. This isn’t as easy as it sounds.
Something I run across often is someone with a “great new theory” (at best one of those descriptions is true) or a scenario that supposedly tears down a pillar of physics (usually relativity), who doesn’t realize that a thought experiment doesn’t (dis)prove anything, because absent any comparison with experiment, all a contradiction shows is that your thought process has some problem — it’s pretty easy to assume contradictory things, which wreak havoc on thought experiments. (For the relativity folks, it’s usually a subtle assumption of absolute simultaneity)
One thing glossed over: Joe mentions that the muons are undergoing time dilation by some factor, which allows a fraction of them to live long enough to reach earth, but in their own frame their clocks run normally. How can that work? The missing piece is that the muons see their travel as length contracted by the same factor. They don’t decay because they didn’t travel very far, (or for very long) as seen in their frame.
The link to make a cloud chamber
Reminiscent of yesterday’s video — our chief scientist saying similar things, mostly as a proxy for the efforts of my hard-working colleagues (and me). You get a nice view of our wonderful library, though our wonderful librarians are out of view.
I should point out that when Chris Wallace talks about cesium clocks, what the camera is pointing to (that big black box) is a hydrogen maser. Shhh. That’ll be our little secret.
There’s a bonus! An ad at the beginning. The kind you’d expect at Fox news. Sorry.
My travel caused me to miss the original airing of this, and the site says it’s only active until the 30th. There’s a bit on the Naval Observatory and our (my) Rubidium Fountain Clocks at somewhere around the 45-minute mark, featuring our chief scientist.
A nit/peeve (from the intro to atomic timekeeping): atomic physics and nuclear physics are separate things. Even though we call it atomic power or an atomic bomb, it’s all nuclear processes. The physics behind atomic clocks is not really tied, except at a fairly superficial level, to that of bombs.
This kind of cheap, lazy elitism ticks me off. It says nothing about why science is hard to understand, and it doesn’t even get the frustrations of the job right. I mean, “collecting data”? “Dense research articles”? Neither of those necessarily implies tedium or drudgery. Shockingly, not everything which requires patience and concentration is unpleasant.
I’ve heard the remark from a colleague that 80% of what we do is mundane, but we do that because 20% is really, really neat. (YMMV). One needs to acknowledge that science is not alone in this — professional (or other top-level) athletes, for example, spend more time practicing than they do playing the game. It’s all part of the larger picture. And, as Blake points out, who’s to say what is tedium or drudgery?
Admin note: Been on the road. It’ll be a while before I’m caught up.
The narrative is good, the art is good, but I think the depiction of electrons with classical trajectories, both in the double slit and orbiting as in Bohr atoms detracts from this; it arguably sends the wrong message about what’s going on and may reinforce misconceptions. I don’t know if this is simply a problem of illustration, since trajectories are relatively simple, and depicting QM is trickier. It’s not like I have a simple fix for doing the depiction better, though.
US North and South had different rail track gauges. They fixed it pretty much all at once.
I’m glad I ran across this after the update, as this interesting observation was added (quoting from one of the links)
As things turned out, having different gauges was advantageous to the South, since the North could not easily use railroad to move its troops to battle in southern territory during the Civil War. Noting this example, the Finns were careful to ensure that their railroads used a gauge different from the Russian railroads! The rest of Europe adopted a standard gauge, which made things easy for Hitler during World War II: a significant fraction of German troop movements in Europe were accomplished by rail.
Also the note about how the standard gauge was adopted after secession, so there was no opposition from the South. Adoption of standards is usually contains a large dose of politics. If the dissenters aren’t in the room, consensus is easier.
Going back to the original idea of relativity — simply looking at the relative motion between objects, and the idea that you are allowed to look at the physics in the reference frame that makes the analysis the easiest.
The other thing [besides analyzing momentum] you can do is to invoke relativity a la Galileo. The problem where both bat and ball are moving is still kind of a pain, mathematically, but if one of the two is stationary, then your life gets a whole lot easier. And we know what happens when a light moving object like a baseball hits a heavier object like a bat that isn’t moving: the ball bounces back at a fair fraction of the speed it came in at, and the bat only moves a little bit.
I’m hunting astwonomical objects
Scientists who use some of the world’s most advanced instruments can’t use a microwave oven to heat their lunch. And then there was the time astronomers were baffled by a mysterious distortion of their data. They had a laugh when they discovered that the errant energy waves were coming from battery-operated fans sold in the facility’s gift shop.
Gren Bank was also the target for a facility to house an alternate master clock for the Navy/DoD, because Robert Byrd wanted it, but that was shot down in the early 90’s.