How would you go about determining absolute zero? Intuitively, it seems like you’d need some complicated physics setup with lasers and maybe some liquid helium. But as it turns out, all you need is some simple lab glassware and a heat gun. And a laser, of course.

To be clear, the method that [Markus Bindhammer] describes in the video below is only an estimation of absolute zero via Charles’s Law, which describes how gases expand when heated. To gather the needed data, [Marb] used a 50-ml glass syringe mounted horizontally on a stand and fitted with a thermocouple. Across from the plunger of the syringe he placed a VL6180 laser time-of-flight sensor, to measure the displacement of the plunger as the air within it expands.

Data from the TOF sensor and the thermocouple were recorded by a microcontroller as the air inside the syringe was gently heated. Plotting the volume of the gas versus the temperature results shows a nicely linear relationship, and the linear regression can be used to calculate the temperature at which the volume of the gas would be zero. The result: -268.82°C, or only about four degrees off from the accepted value of -273.15°. Not too shabby.

[Marb] has been on a tear lately with science projects like these; check out his open-source blood glucose measurement method or his all-in-one electrochemistry lab.

There are a whole bunch of different ways to create 3D scans of objects these days. Researchers at the [UW Graphics Lab] have demonstrated how to use a small, cheap time-of-flight sensor to generate scans effectively.

The key is in how time-of-flight sensors work. They shoot out a distinct pulse of light, and then determine how long that pulse takes to bounce back. This allows them to perform a simple ranging calculation to determine how far they are from a surface or object.

However, in truth, these sensors aren’t measuring distance to a single point. They’re measuring the intensity of the received return pulse over time, called the “transient histogram”, and then processing it. If you use the full mathematical information in the histogram, rather than just the range figures, it’s possible to recreate 3D geometry as seen by the sensor, through the use of some neat mathematics and a neural network. It’s all explained in great detail in the research paper.

The technique isn’t perfect; there are some inconsistencies with what it captures and the true geometry of the objects its looking at. Still, the technique is young, and more work could refine its outputs further.

If you don’t mind getting messy, there are other neat scanning techniques out there—like using a camera and some milk.