27 Historical Science Experiments You Should KnowCracked put together a pictofact list of science experiments they label as "crucial or completely random." I would have labeled them as "weird or unethical," except for one entry about David Koch funding cancer research which may have been included because of Koch's political reputation. Still, most of them are things anyone interested in science should be aware of. Some of the biggest medical breakthroughs have come at the expense of people or animals who gave no consent and were sometimes treated horribly. Some gave us enduring ideas that have since been debunked. Others are just plain weird.
Soft Tissue in Fossil Turns Out to Be Black PaintA fossil of a reptile was discovered in the Italian Alps in 1931. It was identified as being 280 million years old, a new species of a new genus named Tridentinosaurus antiquus. The fossil, described in 1959, was unique in that the soft tissue was preserved as carbonized skin or flesh. That could have happened if the animal died from the pyroclastic flash of a volcanic eruption, which would have burnt its exterior before it was buried. It was altogether considered an outstanding specimen.Fast forward to the 21st century, and the fossil was revisited with modern tools for chemical analysis that are minimally invasive. The reptile fossil was compared to plant fossils found in the same area, and found to be quite different. The carbonized flesh was determined to be "a manufactured carbon-based pigment mixed with an organic binder," or the kind of black paint used in the early 20th century. The actual fossil appears to consist of only the long bones of the hind legs. Was it a hoax? Not necessarily. Fossils were treated very differently in 1931, and the alterations are consistent with some practices of the day. Adding lacquer or varnish to a fossil was thought to help preserve them, but actually caused damage. The paint may have been to illustrate what scientists thought the complete animal would have looked like. But there's no evidence that it was all that accurate. Read the history of Tridentinosaurus antiquus and how the modern analysis changed it at Ars Technica. -via Strange Company ​(Image credit: Valentina Rossi) 
Blue Eyes May Have an Advantage in Low LightWhether a person has blue eyes or brown eyes depend on whether the iris contains melanin. Scientists believe that irises lacking melanin began as a mutation in one person that passed along well enough that 10% of the world's population now has blue eyes. Did the mutation provide some kind of benefit that encouraged its propagation? A team from Liverpool John Moores University conducted an experiment with 39 volunteers, 25 with blue eyes and 14 with brown eyes. They found that those with blue eyes could read under dimmer light than those with brown eyes. The blue-eyed subjects could read under light down to only 0.7 lux on average, as compared with an average of 0.82 lux for the brown-eyed subjects. That may seem like a small difference, but it is statistically significant. However, the sample size was small. If being able to see under dimmer light is an advantage conferred by blue eyes, it's no wonder that the mutation propagated most successfully in Europe, particularly northern Europe, where the sun hits the earth at a fairly extreme angle in the winter. No one knows where the mutation began, but it may have held an advantage only for those working under less sunlight. -via Real Clear Science​(Image credit: Rob Unreall) 
The Dinosaur That Had a Belly ButtonNavels, or belly buttons, are a scar that remains from our time before birth when we received nutrients from our mothers through the placenta and umbilical cord. Most placental mammals have navels, although they can be hard to find. You might be surprised to learn that birds and reptiles have a similar type of scar called an umbilicus from their attachment to a yolk sac inside their egg, although in many species that scar completely disappears over time. What's really amazing is that in 2022, scientists identified an umbilicus in a 130 million-year-old non-avian dinosaur fossil! What's more, it was an adult specimen, which means dinosaurs may have had belly buttons that lasted their whole lives. Sci Show explains how they found this surprising scar and why it might be particularly fascinating for kids to learn about.
The Earth May Carry Remnants of an Ancient CollisionAround four billion years ago, earth gained its moon, but it came at a great cost. The leading theory is that another planet we now call Theia slammed into the earth, and the debris that this collision spewed around in space eventually amassed into what is now our moon. We know the earth survived this collision, but what happened to Theia? Some of it ended up in the moon, of course, but that's only a fraction. Some of it was expelled into space. But anomalies in our measurements of the earth and its behavior indicate that there are masses underneath the earth's surface that don't make sense. It could be that large parts of Theia ended up melded with the earth's mantle, and have been with us all along. Hank Green explains what gave us that idea in this episode of Sci Show.
Prehistoric Tree Looked Like a Dr. Seuss DrawingFossils unearthed in Canada remind us that millions of years ago, life took forms that seem quite alien to us, as explosions of different plants adapted to changing conditions on earth. An example is the tree in the illlustration above. The people in the image above are only there for scale. The tree they are standing under lived 35 million years ago, and was unlike anything humans ever saw. The tree left an impression in a lake bed that became a fossil in New Brunswick. Scientists have designated it as Sanfordiacaulis densifolia, although they aren't clear whether it is related to any other known tree from the period. This tree had leaves that were six feet long and extended out from a non-woody trunk only six inches thick! The overall shape is like that of a bottle brush. The upper canopy would have extended far from the trunk and intercepted light as best as it could underneath taller trees. You have to wonder how much all that foliage weighed and how such a spindly trunk could hold it up. Read what we know about Sanfordiacaulis densifolia from its fossil evidence at Gizmodo.(Image credit: Tim Stonesifer)