Wow! I was curious about how they measure the fat content in milk while I was writing this and found something similarly baroque haha, food science seems to require detailed custom protocols for basically anything you can think to measure
Further reading
www.mcgill.ca/oss/article/...
wesscience.site.wesleyan.edu/chemistry/
References
journals.aps.org/pri/abstract...
archive.org/details/desc...
So the next time you’re out camping and get your marshmallow a little too close to your fire, make sure you have a calorimeter nearby so it’s not a total waste!
7/7
I’ve written about fire before—it is, after all, ultimately the product of a chemical reaction, not unlike the bond-breaking reactions your body uses to liberate energy from your food.
bsky.app/profile/idon...
6/7
Diagram of a calorimeter setup illustrating components used to measure temperature changes in a sample. Key elements include a water bath in a container with a thermometer, bomb cell holding the sample, stirrer connected to a stirring motor, and an ignition box linked by fuse wires, with temperature reader displaying 23.00. By Lisdavid89 - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=22537546
One food “Calorie” is literally defined as the amount of energy needed to raise a liter of water from 14.5°C to 15.5°C. So what better way to measure Calories than burning your food? Calories in digestible components of food—fat, protein, non-fibrous carbohydrates—can all be measured this way
5/7
Photograph of a digital bomb calorimeter setup used for measuring heat of combustion in materials. Key components include a stainless steel combustion chamber, pressure gauge, ignition wires, and a digital control unit with display and buttons. By Akshat Goel - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=18702902
He found agreement with the laws of thermodynamics to 1%. With this question settled, food scientists could fall back to the so-called “bomb calorimeter” values to measure calories—which, yes, involves lighting food on fire to see how much energy is released.
4/7
A schematic of Atwater's respiration chamber. The caption reads, "Fig 2--Interior of the respiration chamber. This is the view which would be secured by breaking away a portion of one side and end of the interior copper wall of the respiration chamber. The ventilating air enters the chamber through the bottom of W, leaving from the rear of the chamber through the long tube connected with the upper end of W. The copper tubes H, H, strung with copper disks I, I, constitute the absorbers through which flows the water current which carries away the heat generated in the chamber. J, J are the copper troughs for collecting the drip from the absorbers. M, M, M are electrical thermometers which show the temperature of the air in the chamber; N, N those which show the temperature of the copper wall." From "Description of a new respiration calorimeter and experiments on the conservation of energy in the human body," Atwater, Wilbur and Rosa, Edward B.
That changed in the late 1890s, when Wilbur Atwater and collaborators decided to lock up some undergraduates at Wesleyan in a “respiration chamber”. In this small chamber they could carefully measure how much energy went into and out of the room, and therefore their test subjects.
3/7
The story of metabolism research is kind of crazy because for a long time people weren’t sure whether the first law of thermodynamics even applied to people. So-called “vitalists” argued that living beings were instead governed by laws outside physics.
2/7
a really stupid graphic of a nutrition label in front of some explosion clipart. Nutrition label by Jaidan899 - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=47602598
How do they figure out how many calories to put on the nutrition label in your food?
If you’re savvy, you know this involves lighting your food on fire.
If you’re extra savvy, you know they figured it out by **locking human beings in sealed rooms**.
1/7 ⚛️🧪
thousands of person-hours wasted across the country today with these four lines of text. I couldn't create better obstacles for scientists trying to do their jobs if I tried ⚛️🧪
Further reading:
www.nhm.ac.uk/discover/how...
References:
epub.uni-regensburg.de/124/4/epub_1...
deepblue.lib.umich.edu/items/7e7983...
An electric eel, peering at you with tiny eyes. Oleksandr (Alex) Zakletsky, CC BY 4.0 https://creativecommons.org/licenses/by/4.0, via Wikimedia Commons
By contrast, the torpedo ray has ~1,000 parallel stacks of electrocytes, generating low voltage and high current for power transfer in low-resistance surroundings. That’s the magic of impedance matching—wiring a circuit to account for resistance at an interface—and fish do it better than I can!
7/7
Cross section of an eel, showing its main organ, which contains many stacks of cells that extend about 80% of the length of the eel's body. Adapted from work by National Institute of Standards and Technology - Biotechnology, systems biology, artificial cells, Public Domain, https://commons.wikimedia.org/w/index.php?curid=51195648
So they “wire” their “circuit” in series—that is, they stack about 6,000 of the cells they use to generate electrical impulses (called “electrocytes”) one after another. This creates a huge voltage—exactly what’s needed to transmit power into a medium with high resistance!
6/7
Puns aside, electric eels are freshwater fish. Despite what your parents told you about lakes and lightning, the resistance of freshwater is pretty high, especially compared to that of seawater. If eels are to maximize power transferred to prey, they need to account for this high resistance.
5/7
A torpedo ray, flattened on the seafloor. It somewhat resembles a stingray, but has no long stinger--this hunter's weapons are better concealed. By Roberto Pillon - http://fishbase.org/photos/thumbnailssummary.php?ID=2062#, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=14804545
Electric eels aren’t the only electric fish in the sea. The torpedo ray is a saltwater fish that also manages to deliver a shock—just as effective for stunning prey, but at a much lower voltage than the electric eel.
So why do electric eels generate such high voltage?
4/7
More details Impedance matching in strongly electric fishes. Since freshwater is a poor conductor, limiting the electric current, electric eels need to operate at high voltage to deliver a stunning shock. They achieve this by stacking a large number of electrocytes, each producing a small voltage, in series. By Chiswick Chap - Own work, based on Kramer, Bernd (2008) "Electric Organ; Electric Organ Discharge" in Marc D. Binder, ed. Encyclopedia of Neuroscience, Berlin, Heidelberg: Springer, pp. 1,050–1,056 ISBN: 978-3-540-23735-8., CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=117835201
But the COOLEST thing I learned about eels today is that they manage to pull off a feat so impressive that physics undergraduates routinely struggle with it.
It’s called impedance matching, and electric eels’ mastery over it is key to their success as hunters.
3/7
Illustration of cells and other components of an electric eel, with various charts drawn above (aided in the discovery of the Sachs organ, one of the three organs eels use to generate electrical impulses). By Karl Sachs - https://digitalesammlungen.uni-weimar.de/viewer/object/lit1058/29/, Public Domain, https://commons.wikimedia.org/w/index.php?curid=120496717
First, there’s a ton of cool stuff I learned about electric eels today that I would be remiss if I did not share: did you know they breathe air? Or that they grow forever and just add more vertebrae to their spinal columns?? And that their study contributed to the invention of the battery???
2/7
Electric eels! Childhood nightmare! Cartoon weapon! Able to generate shocks of nearly 900 volts to stun prey and ward off predators!
But that’s an INSANE voltage, actually—why does it need to be so large?
1/7 ⚛️🧪
It's not impossible to break this pattern---some models can change Hubble a lot and only change the well-measured parameters a little bit! But I don't know of any model that totally decouples Hubble from parameters we measure well, and so model building the Hubble tension just got a lot harder.
6/6
Some of these parameters are just fine to shift. But others are not, **because we have other measurements that tell us what their values should be**. That's the big statement of this paper: changing Hubble requires changing one of these parameters that we measure well.
5/6
I found... this doesn't work very well. To get Hubble to agree and to otherwise stay consistent with our measurements of the early universe, you can't just change the value of the Hubble constant--all of your other parameter values need to shift around to stay consistent with data.
4/6
This is a pretty big problem for the standard cosmological model, since that model says those two measurements should give the same number. So some physicists try to solve this problem by building new cosmological models that can get these measurements to agree on the value of this constant.
3/6
If you're not familiar, the Hubble constant is a parameter of cosmology that indicates how fast the universe expands. If you measure the Hubble constant by looking at the universe close by, you get a very different number than what you get looking much further away with a different technique.
2/6
If you're wondering why I've been so quiet for the past 5 weeks, it's because I was writing this paper:
arxiv.org/abs/2604.05095
An epoch of cosmology apparently unrelated to the Hubble tension puts pressure on *all* early-time solutions to the Hubble tension--background provided below 👇
1/6 ⚛️🧪
HERE TO DO PRECISION COSMOLOGY 💪💪💪💪💪
they stole an hour from women
scrolled past this and thought someone was publishing a posthumous sequel to Hyperion
A gray shorthair cat at the moment of release upside down, with its tongue out looking derpy
A new paper on falling cat science came out and I just have to draw people's attention to this image
References
link.springer.com/chapter/10.1...
www.edp-open.org/images/stori...
escweb.wr.usgs.gov/share/mooney...
Further reading:
You can read a firsthand account of the 1887 earthquake here: archive.org/details/sim_...
It’s beautiful and I wish scientists still wrote like this.
A (paywalled :/ ) account of what happened in the mines during this earthquake is at pubs.geoscienceworld.org/ssa/bssa/art...
