When The Big Bang Theory first premiered, I watched it with a lot of hope.
It had science script checkers and sought to bring the nerdy culture of physics into the mainstream. My wife (then girlfriend) and I started watching it while we were both undergrads – me in engineering physics and she in physics. While it’s predominantly male cast and token ditzy blonde was problematic from the start, it was relatable for us and our friends. Even if none of us were a Leonard, Sheldon, Raj, or Howard, we saw bits of each of those characters in each of us. Even Penny started to develop into a rounded character and slowly they introduced a couple female scientists. Overall, it was good.
But it’s moved so far from that. Many of our friends gave up on it years ago as the show drifted toward the lowest common denominator. The physics jokes are almost entirely gone and the humour is more about laughing at the gang for being nerdy and socially awkward than the humour in the situations they get into.
This latest episode – the ninth season premier at that – reached an incredible new low though. Amy’s escape from her joyless relationship with Sheldon was seen by Sheldon as an indictment on half the population. The script writers then chose to run with that “gag” through the entire episode. In one scene Sheldon is creeping in a window because he wanted to pressure Amy into getting back together with him. By the end he’s saying that the only good woman is scientist Marie Curie but she was “an honorary man because she had a penis made of science.”
Not to be outdone on the creep-factor, comic book store owner Stuart’s gag was to instantly prey on every female character as soon as he had a hint that she might be single. Meanwhile Leonard follows up his elopement to Penny by revealing that he works with a woman he cheated on Penny with and then offers sex as a means to distract her.
Given the deep systemic issues faced by women in science, there’s no forgiveness for this show to stoop to this level. What could be a way to make science cool, fun, and engaging has instead just become offensive for its misogyny, its disservice to the incredible women in science, and for perpetuating cruel stereotypes about men in science.
Back in August I was invited to join Don McLenaghen on Radio Freethinker, the skeptical podcast of CiTR radio (the UBC radio station). Ethan was away that week, so we spent the entire hour talking about Humanism.
You can listen to that interview here (mp3).
Last week, I took a road trip to Edmonton, via Kamloops.
While in Kamloops I dropped by a meeting of the Kamloops Centre for Rational Thought and gave a (somewhat impromptu) short speech on Humanism before going into an extended discussion. I posted my brief presentation on YouTube:
Then, in Edmonton I gave my speech on communicating evidence for the Big Bang, entitled 13.7 Billion Years in 90 Seconds for my old group, the University of Alberta Atheists and Agnostics.
This afternoon I defend my masters thesis, after which I will hopefully have only a few minor corrections and then I will have earned my masters in physics. I also hope to be done school for a while, so if you know of any good job openings…
But the busy life won’t end this afternoon.
This weekend I will be one of the Vancouver-Point Grey delegates to the BC NDP’s 50th Anniversary Convention. I won’t be live-blogging it, but I will try to tweet updates. There’s a federal leadership townhall on Saturday from 4:30-6 PM, so those tweets will be under #ndpldr while general convention tweets will be under #bcndp50. I’ll try to make it to one of Brian Topp’s meet-and-greets at The Lion’s Pub (either Friday or Saturday night) and we’ll see if I can find any other leaders.
After the convention I will have my corrections and then holiday parties begin. Then I head to Alberta for Christmas, but will be back in Vancouver by New Years.
In other words, I will try to get some blogging in next week, but otherwise it might be quiet around here until January.
I finally got a half-decent video of myself giving a talk. Of course the projector still failed to work with my laptop, so I went slide-less (but it still works I think).
I gave this talk this morning for the BC Humanists at Oakridge Seniors Centre. The TalkOrigins article I referenced can be found here.
Here’s the video, on presenting evidence for the Big Bang in clear and succinct terms.
After reading a Built on Facts post on a recent Mythbusters episode that tackled one of the classic first year physics problems (that I happen to be TAing right now), and posting the video on my Facebook, one of my more analytic friends pointed out the shoddiness of the 10% error in their precise experiment.
First, here’s both parts of the video, the first contains all the numbers you need to run the physics estimates and the second has the results:
Here’s the summary of the important values:
Horizontal distance (fired outside): 360 ft = 110 m
Vertical drop: 36” = 0.914 m
So let’s run through the calculations and see where some error can accumulate.
First source: They measured the horizontal distance outside and then moved the gun inside and never re-measured the horizontal distance. While the calculations don’t tend to care where the gun is fired (since we ignore air resistance), the actual bullet is potentially affected by the wind/weather/etc. outside. Humidity actually decreases the density of air, creating less drag and friction than drier air. Total error (estimated): ~0.5%
Second source: I’m not sure if this is a source of error, since information was omitted, but they never guaranteed that the gun was fired level outside when they shot it to find the horizontal distance. Since the bullet needs to leave the barrel with zero vertical velocity, it is imperative that the gun be fire horizontally. However, this ranging exercise was more to place the dropped ball at the same spot as the bullet for the camera, so I’m going to take this error as negligible (however, this distance becomes important for my later calculations, but we’ll assume it’s within ~5%, or about 5 m of the reported distance).
How long should the drop take until the bullet (or ball bearing) take to hit the ground?
(1)
with g=9.81m/s2, the acceleration due to gravity near the surface of Earth, we get a drop time of 0.432s. Just under half a second, or about the time your mind takes /to comprehend a simple picture.
Since we know the time to drop (or at least the theoretical value since they didn’t tell us the experimental time), we can calculate the horizontal velocity.
(2)
where x is the total distance of the bullet, measured outside. This gives a velocity of 255 m/s leaving the barrel, or 3/4 the speed of sound.
Third source: I’m not too familiar with fluid dynamics, but suffice it to say that we can assume some difference in downward drag between the bullet and the ball bearing, although unlikely to account for much more than a 1% error.
And if you really want to get technical with a discussion of fluid dynamics, drag and models of bullet ballistics, check out the overly-in-depth Wikipedia article on ballistics as a start.
Now, in part 1, Adam uses a laser to make a line, level with the gun, at a sheet 20’ from the barrel. He then claims that the bullet’s drop between the gun and the sheet will be negligible. It’s worth noting that we expect this to be false since the distance between the sheet is roughly 1/20th of the total distance travelled, or 5%.
Since we know the horizontal velocity (or at least have a calculated estimate of it), we can find the distance dropped in that distance via the time. Rearranging equation (2) to find the time, we get 0.0239s to hit the 20’ target and rearranging equation (1) to find the drop, y, we get a drop of 2.39 cm, or almost 1”.
Fourth source: Adam assumed that in the first 20’ of horizontal travel that the bullet’s drop was negligible when in fact it represented 1/36 of the total drop of the bullet. This introduces an error of roughly 3%, not huge, but it’s beginning to add up.
Now, Jamie show’s off his impressive timing device and demonstrates that the release is timed to 1/3 of a millisecond, or 300 microseconds.
Fifth source: The timing difference introduces an absolute error of less than 1%.
However, to demonstrate his device, Jamie places the dropper and the gun next to one another and lets the high-speed camera capture the release difference. He then moves the dropper to the end of the course for the actual test. I have to assume for safety that they coiled the long cord up when they had the two devices next to one another. A coiled wire will have some inductance, and hence an associated time constant, which will delay the signal. This would mean that the ball might drop sooner when the wire is straightened out.
Let’s figure out an order of magnitude for this time constant.
The inductance of a coiled wire is given by:
(3)
Where L is the inductance, is the permeability of free space, N is the number of loops, A is the area of a loop and l is the length of the coil (assume this to be 10cm for a tight packed coil, note this is not the length of the wire). The wire has to be at least 360’ long, and they likely coiled the majority of it, and if it is coiled into loops with area of 0.785m2 (assuming loops of 1m diameter) we therefore have 32 loops. Using all of this we get an inductance, L of 10.1 mH. If we assume resistance of the wire to be 0.1 Ohms, then we get an RL time constant of up to 0.1 s.
Sixth source: If Jamie coiled the wire of his dropper when he measured the two devices next to one another, he may have introduced a significantly large time constant into the system – on the order of the time it took to drop the ball! Since I don’t know whether or not this happened, or to what extent, I can’t quantify this error any better than to say it could be negligible if it was controlled for, or it could have screwed the experiment. Of course, with properly shielded cable this may not even be a concern.
I have just a couple more issues:
Seventh source: The shutter speed of a high-speed camera is finite, so they have an upper limit on measurements taken by the camera. The best guess I have for this is the 300 microsecond measurement that they gave for the measured difference in the drop times, assuming that measurement was limited by the camera. Knowing Mythbusters, I can see them having some of the fastest high-speed cameras that are commercially available, so this error is likely negligible.
Eighth source: I almost forgot this one, but it’s a huge no-no in science. They got cocky and ran their experiment only once! Their trigger device still worked, so the least the could have done was performed a couple times and averaged them out (perhaps they did and it didn’t make the cut). This is just sloppy and it’s hard to really quantify any error with this though.
Taking all of these various sources, especially the incorrect drop assumption (fourth source of error) and potentially the cord inductance (sixth source), it is not unreasonable that the difference could be upwards of 10% in this experiment.
Of course this is Mythbusters and not a class on error analysis. The show is more valuable by remaining entertaining and employing the rough tools of science, with the nitty-gritty details to be filled in later.
I haven’t done a Photonics Briefs for a while, and I can’t promise to do one for the next while, but this latest Nature Photonics issue had an interview that’s too cool not to share.
Phil Plait of Bad Astronomy is having some issues with squirrels attempting to defeat quantum mechanics.
But I think this requires a closer look and a bit more physics.
In his first picture (Squirrel Wavelength), we see the squirrels would travel with approximately 1/4 a fence-length wavelength. We’ll call this a wavelength of 0.25.
In the newer picture, taken at a lower temperature, we can estimate a wavelength of roughly 0.1 (it’s a little shorter but that’s not too much of an issue).
Phil’s concern is that quantum mechanics predicts that as temperature decreases, wavelengths increase. However, by demonstrating this relationship, these squirrel’s have disproved quantum mechanics!
Now, one commenter suggests that this could be due to multiple squirrels superimposing their tracks, or even one squirrel that crossed the fence multiple times, however, this explanation is just not fun enough for these sorts of exercises.
The general relationship for energy and wavelength is given by E = hc/?, where E is the energy, h is Planck’s constant, c is the speed of light and ? is the wavelength. Energy is proportional to temperature, so wavelength is inversely proportional to temperature.
But there’s a problem here: the squirrel’s aren’t moving at c (roughly 300 000 km/s), they aren’t even moving at a constant velocity!
If we assume that the frequency of the squirrels, f=v/? where v is the velocity of the squirrel, is constant (a safe assumption for most waves), then we can figure out a relationship for the squirrels velocity with respect to temperature.
So since the squirrel’s wavelength decreases with temperature, to maintain the constant frequency relationship, we must infer that the velocity increases with decreasing temperature!
Basically, the little buggers move faster because it’s really cold.
This relationship will have to be further developed as it only takes into account non-relativistic squirrels, and the relationship would seem to imply that as the temperature continually dropped, the squirrels would approach near infinite speeds!
There’s a caveat here though: at a finite temperature the body functions of the squirrel will shut down and kill the vermin, thereby preserving the laws of physics for us all.
