Commander of all of those dog robots, by the inventors of big dog.
Monthly Archives: November 2011
I Feel That Ice is Slowly Melting
This has already led to rapid growth in solar installations, but even more change may be just around the corner. If the downward trend continues — and if anything it seems to be accelerating — we’re just a few years from the point at which electricity from solar panels becomes cheaper than electricity generated by burning coal.
And if we priced coal-fired power right, taking into account the huge health and other costs it imposes, it’s likely that we would already have passed that tipping point.
But will our political system delay the energy transformation now within reach?
This Clock Has Stopped
Norman Ramsey Dies at 96; Work Led to the Atomic Clock
In 1949, Dr. Ramsey invented an experimental technique to measure the frequencies of electromagnetic radiation most readily absorbed by atoms and molecules. The technique allowed scientists to investigate their structure with greater accuracy and enabled the development of a new kind of timekeeping device known as the atomic clock. Dr. Ramsey received the Nobel Prize in Physics in 1989 for both achievements.
I had the privilege of meeting him and hearing him at a few talks where he told stories of the old days (I thought perhaps he was working on a book). Here is a picture of us at a conference in Seattle in 2005, where I am showing our nascent clock’s “Ramsey fringes” results to him — an interference pattern from the spectroscopy technique he pioneered — along with the clock stability results.
(photo credit: Tom Van Baak)
I Knew I Could, I Knew I Could
This Model of Stephenson’s Steam Engine was made in 2008 by master glassblower Michal Zahradník.
One nit: at about 1:40 it says to notice the steam exhaust — steam is water vapor and is invisible, so you can’t notice it. That’s one reason that steam line ruptures are so dangerous. If you can see it then the water has begun to condense; what you can see are small water droplets.
Let Me Focus for You
What Good Is The Lytro Light-Field Camera?
The fundamental problem for a light-field revolution, though, is that focus is not the limiting factor for most photographers. Fixing focus issues doesn’t add much to a photographer’s tool kit. Light sensitivity, magnification, dynamic range, stabilization, resolution- these are all areas where technological improvements solve immediate hurdles for different genres of photography. Focusing? Not so much.
Um, really? Focusing is not the limiting factor? I think that the author is not looking from the proper perspective. It may not be an issue for a professional photographer or even the accomplished amateur, but the point-and-shoot crowd probably has issue with autofocus grabbing the wrong target, ruining the shot, or the delay from it making you miss it. And this is a product for that crowd.
The included example is quite interesting, allowing you to focus on the fore-, mid- or background, which changes the emphasis of the photo.
The Magdeburg Thermos Container
A comment from the slacktivist
Sometimes I can’t get the thermos open. This is frustrating because: A) There is coffee in the thermos, and I want coffee; and B) I twisted the thermos lid shut myself, and thus it seems logical to expect that I should also be strong enough to untwist it myself.
…
Oh, and as for the thermos, I find running hot water over the lid for a bit usually does the trick.
Logic? Nay, it is basic thermodynamics is the problem, and solution, here. A thermos is a good insulator — a vacuum is an excellent barrier against conduction and convection, but it’s not perfect — and you still have radiation. So the coffee cools, and since you likely left an air gap in the container, the pressure of that air is going to drop along with the temperature. PV = nRT. The volume is fixed, and we can assume n is not going to vary too much — the air will likely have 100% relative humidity fairly quickly after the thermos is sealed. As the system cools some small amount will condense, but to first order I’d expect it to be a linear relation. Even a small container with a diameter of 7.5 cm (~3 inches) has a surface area of ~44 cm^2 (7 square inches). For each 1ºC drop in temperature of hot water, that’s about a 0.003 (0.3%) drop in pressure, which is about 1.3 N of force, or 1/3 of a pound. So what of the temperature has dropped 10 degrees? This problem is amplified for larger caps, since it depends on surface area — a 4-inch cap will give you a half a pound per ºC.* On a sealed container with less structural integrity and/or sufficiently large surface area, cooling a liquid/gas mixture inside can lead to the container collapsing.
And it gets worse because the coffee is probably making a good seal of the threads — some air might have escaped when it was closing but now it can’t get in, so now you are trying to increase the volume which causes a further drop in pressure. More work that your hands have to do. This actually is more of a problem when you’ve filled the container up, since the relative change in volume is larger. A container that’s mostly filled with air will see only a small increase in the volume, but one filled with coffee might require that the volume double, meaning the pressure has to drop in half (roughly — water will evaporate at the lower pressure to mitigate this). So this might be responsible for a several percent drop in pressure, corresponding to several pounds of force on the cap.
The net result is that you are pulling against a vacuum (poor quality from a lab perspective, but that’s just a matter of magnitude) This is a version of the Magdeburg hemisphere experiment.
Heating does two things: it increases the pressure inside, and if you are heating the container faster than the cap, the differential expansion can allow some air to get inside to equalize the pressure.
* I really shouldn’t mix units like this, but being from the US I still think of weight and force of everyday events in terms of pounds.
Method Acting
What eight years of writing the Bad Science column have taught me
Science isn’t about authority, or white coats, it’s about following a method. That method is built on core principles: precision and transparency; being clear about your methods; being honest about your results; and drawing a clear line between the results, on the one hand, and your judgment calls about how those results support a hypothesis. Anyone blurring these lines is iffy.
Conflict of interest stories – where someone has a vested interest in the results of their study – are important, because they tell you when there’s a risk that something’s wrong in a piece of science. But this is only motive: the gruesome, fascinating mechanism of a crime against science – the methodological flaws – that’s where the action is. People who don’t really understand science can only critique it in terms of motive. Let them have that; we’ll do the details.
How to Focus
I did not know there was a focus assist button on (some) video cameras.
Can We Say So Long to DST?
Why Daylight Saving Time Should Be Abolished
I’m not at all opposed to this; I have an increasingly hard time dealing with the time change — especially in the spring. And the argument about saving energy (in the US) seems to have gone by the wayside with more widespread adoption of air conditioning. I do enjoy the extra evening hour of sunlight in the spring and fall because it extends the time I can go geocaching, but I’d manage if we eliminated the practice.
The Tension is Soooo Thick …
I tried doing a similar demo, but used a beaker and it’s a lot harder to place the objects in so that they will float. Which is why I don’t have a video like this.