[Hank Green] posted an interesting video about the first liquid mirror telescope from back in the 1850s. At the time, scientists were not impressed. But, these days, people are revisiting the idea. The big problem with the early telescope is that it used mercury. Mercury is really bad for people and the environment.
The good thing about a liquid scope is that you can pretty easily make a large mirror. You just need a shallow pool of liquid and a way to spin it. However, there are downsides. You need to isolate the liquid from vibrations and dust. Another downside is that since gravity makes the shape of the mirror, these telescopes only go one way — straight up.
Of all known metals, mercury is probably one of the most famous, if only for its lustrous, liquid form at room temperature. Over the centuries, it has been commonly used in a wide variety of applications, including industrial chemical processes, in cosmetics, for telescope mirrors, thermometers, fluorescent lamps, dental fillings, bearings, batteries, switches and most recently in atomic clocks.
Though hardly free from the controversy often surrounding a toxic heavy metal, it’s hard to argue the myriad ways in which mercury has played a positive role in humanity’s technological progress and scientific discoveries. This article will focus both on its historical, current, and possible future uses, as well as the darker side of this fascinating metal.
[Cole Price] describes himself as a photographer and a space nerd. We’ll give that to him since his web site clearly shows a love of cameras and a love of the NASA programs from the 1960s. [Cole] has painstakingly made replicas of cameras used in the space program including a Hasselblad 500C used on a Mercury flight and another Hasselblad used during Apollo 11. His work is on display in several venues — for example, the 500C is in the Carl Zeiss headquarters building.
[Cole’s] only made a detailed post about 500C and a teaser about the Apollo 11 camera. However, there’s a lot of detail about what NASA — and an RCA technician named [Red Williams] — did to get the camera space-ready.
Star Trek — as much as we love it — was guilty sometimes of a bit of hyperbole and more than its share of inconsistency. In some episodes, ion drives were advanced technology and in others they were obsolete. Make up your mind!
The ESA-JAXA BepiColombo probe is on its way to Mercury riding on four ion thrusters developed by a company called QinetiQ. But unlike the ion drive featured in the infamous “Spock’s Brain” episode, BepiColombo will take over seven years to get to Mercury. That’s because these ion drives are real.
The craft is actually two spacecraft in one with two different Mercury missions. The Mercury planetary orbiter will study the surface while the magnetosphere orbiter will study the little planet’s magnetic field. Check out a video about the mission, below. The second video shows [Neil Wallace] talking about how the ion propulsion — also known as solar electric engines — differ from traditional chemical thrusters.
In his continuing bid to have his YouTube channel demonetized, [Cody] has decided to share how he makes chlorine gas in his lab. Because nothing could go wrong with something that uses five pounds of liquid mercury and electricity to make chlorine, hydrogen, and lye.
We’ll be the first to admit that we don’t fully understand how the Chlorine Machine works. The electrochemistry end of it is pretty straightforward – it uses electrolysis to liberate the chlorine from a brine solution. One side of the electrochemical cell generates chlorine, and one side gives off hydrogen as a byproduct. We even get the purpose of the mercury cathode, which captures the sodium metal as an amalgam. What baffles us is how [Cody] is pumping the five pounds of mercury between the two halves of the cell. Moving such a dense liquid would seem challenging, and after toying with more traditional approaches like a peristaltic pump, [Cody] leveraged the conductivity of mercury to pump it using a couple of neodymium magnets. He doesn’t really explain the idea other than describing it as a “rail-gun for mercury,” but it appears to work well enough to gently circulate the mercury. Check out the video below for the build, which was able to produce enough chlorine to dissolve gold and to bleach cloth.
We need to offer the usual warnings about how playing with corrosive, reactive, and toxic materials is probably not for everyone. His past videos, from turning urine into gunpowder to mining platinum from the side of the road, show that [Cody] is clearly very knowledgeable in the ways of chemistry and that he takes to proper precautions. So if you’ve got a jug of mercury and you want to try this out, just be careful.
If you haven’t heard of it, the Mooshimeter is a two channel multimeter that uses your smartphone as a display over Bluetooth 4.0. The ability to simultaneously monitor voltage and current is rather unique, and the fact that you aren’t physically tethered to the thing makes it ideal for use in hard to reach or even dangerous locations. The promotional material for the Mooshimeter shows users doing things like leaving the device inside the engine compartment of a car while they drive around and take readings about the vehicle’s electrical system.
Note the vertical orientation
All that sounds well and good, but at the end of the day, the Mooshimeter is probably not going to be your primary multimeter. It’s going to stay on a shelf until a task befitting its unique abilities comes along. Unfortunately, as [nop head] found, that can be a problem. Like many modern devices, the Mooshimeter doesn’t actually turn off. It just sits there draining its battery until you’re ready to use it. Which of course means that when you’re finally ready to pull the thing out and put it to use, you get a low battery warning and need to put new AAs in it. First World problems.
The fix for this thoroughly modern problem is delightfully old school: a mercury tilt switch.
Using a small spacer made of Kapton tape, [nop head] was able to isolate the battery contacts from the PCB itself. He then soldered the mercury switch in place between them, making sure to position the bulb vertically. When the Mooshimeter is right side up, the mercury flows down and bridges the contacts; but when the device is inverted the contact is broken and the batteries stop draining. He still has to remember to put the Mooshimeter face down when he’s done with it, but it’s better than dealing with constant dead batteries.
Before the Saturn V rocket carried men to the moon, a number of smaller rockets carried men on suborbital and orbital flights around the Earth. These rockets weren’t purpose-built for this task, though. In fact, the first rockets that carried people into outer space were repurposed ballistic missiles, originally designed to carry weapons.
While it might seem like an arduous task to make a ballistic missile safe enough to carry a human, the path from a weapons delivery system to passenger vehicle was remarkably quick. Although there was enough safety engineering and redundancy to disqualify the space program as a hack, it certainly was a clever repurposing of the available technology. Read on for the full story.
