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Duration:05:53
Uploaded:2016-12-23
Last sync:2018-05-07 22:20
Scientists were able to measure the emission lines of antimatter! And we may have some new clues about how dinosaurs lost their teeth on the way to becoming birds.

Hosted by: Hank Green
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Sources:

Antimatter:
http://www.nature.com/nature/journal/vaap/ncurrent/full/nature21040.html#affil-auth
http://www.sciencealert.com/physicists-have-observed-the-light-spectrum-of-antimatter-for-first-time
http://www.sciencemag.org/news/2016/12/deep-probe-antimatter-puts-einstein-s-special-relativity-test
https://home.cern/about/updates/2016/12/alpha-observes-light-spectrum-antimatter-first-time

Dinosaur:
https://www.eurekalert.org/emb_releases/2016-12/cp-tdl121516.php
http://www.ucmp.berkeley.edu/diapsids/saurischia/ceratosauria.html
http://www.cell.com/current-biology/fulltext/S0960-9822(16)31269-6

Images:
https://commons.wikimedia.org/wiki/File:3D_image_of_Antihydrogen.svg
https://commons.wikimedia.org/wiki/File:Emission_spectrum-H.svg
https://commons.wikimedia.org/wiki/File:Limusaurus_BW.jpg
https://commons.wikimedia.org/wiki/File:Platypus_in_Geelong.jpg
https://commons.wikimedia.org/wiki/File:Limusaurus_inextricabilis_holotype.jpg
[SciShow intro plays]

Hank: You’re probably familiar with the basic parts of an atom: there are positive protons, the uncharged neutrons, and the much tinier, much lighter negative electrons. But there’s a whole set of subatomic particles out there that are the exact opposites of the ones you’ll find in regular matter. These are the particles that make up antimatter. And in a paper published this week in the journal Nature, an international team of more than 50 researchers announced that they’d detected the spectrum of light coming from the antimatter form of a hydrogen atom, aka antihydrogen. Finally. After decades of trying. It’s a pretty big deal.

Antimatter is part of one of the most baffling mysteries in the universe. See, based on what we know about the laws of physics, whenever a particle of antimatter meets up with a corresponding particle of regular matter, they annihilate each other in a huge explosion. And according to the best models we have, the same amounts of matter and antimatter should have existed after the Big Bang.

Which means that everything in the universe should have annihilated itself. But it didn’t... yay! We still have galaxies and stars and planets and humans... and shoes and pop tarts. All the great things that are made of actual regular matter! So physicists around the world are trying to figure out where our models went wrong, and why there was some extra matter left over after the Big Bang.

Measuring the light spectrum of antihydrogen is a key part of solving that mystery. The same laws of physics that predict that there should be no extra matter around also say that antimatter should be an exact mirror image of matter. And a great way to test that idea is by comparing the light coming off hydrogen and antihydrogen.

When you give more energy to the electrons in an atom of regular matter, they jump up an energy level within the atom and then come back down, releasing specific wavelengths of light in the process. The electrons in each element can emit a unique set of wavelengths, forming that atom’s spectrum. The same thing happens in an antimatter atom, except with positrons, the positively-charged, antimatter version of electrons.

And if antimatter really is an exact mirror image of matter, then the positrons in antihydrogen should give off the exact same spectrum as the electrons in plain old regular hydrogen. But scientists were never able to test that prediction... until now.

Working out of the CERN lab in Switzerland, these researchers figured out how to capture about 14 antihydrogen atoms within a 15-minute cycle. Previous research had only managed to capture about 1.2 antihydrogen atoms in a cycle, so the team had a lot more to work with. Then, they used lasers to excite the positrons to higher energy levels, and measured the light the positrons emitted as they came back down.

This is the light coming off of 14 atoms... so there’s not a lot to look at. But what they found was that the antihydrogen emitted the exact same spectrum of light as hydrogen. So basically, exactly what they expected to find.

The results help confirm that our laws of physics are making the right predictions, but they also mean that we still have no idea how to solve the antimatter mystery! Still, at least now we’re better at making antimatter, and we’re able to measure its light. So this experiment will help pave the way for future research into antimatter, and hopefully lead to an answer to the mystery of why anything exists in the universe at all.

Here’s another mystery for you. It’s on a slightly smaller scale, but it’s still weird: Birds as we know them don’t have teeth, but the T. rex sported chompers that looked more like the banana you had for breakfast than any tooth you’ve ever seen. Since birds are descended from dinosaurs, at some point those mouthfuls of steak knives must have evolved into toothless beaks — we just don’t know exactly how that happened.

And in a paper published yesterday in the journal Current Biology, researchers announced that they’d found one clue to how this happened: a dinosaur that loses its baby teeth. When we humans lose our baby teeth, we get another set of teeth. But when this dinosaur loses its baby teeth, it gets a beak instead.

This is the first reptile ever known to completely shed its teeth as it matures. Platypuses do it, along with some fish and an amphibian or two, but this dino is the first tooth-shedding reptile we know of. Other dinosaurs sometimes lose or gain a couple of teeth as they grow, but none are known to lose their teeth completely.

And at first, the team thought the juveniles and adults represented two totally different species. But when they took a closer look, they realized that the fossils looked the same in every way except for the presence of teeth. And when they lined up all the fossils, they looked like a single species growing to maturity. So they realized that they’d found a dinosaur that lost its teeth as it grew up.

Next, the researchers wanted to figure out why the adult dinosaurs didn’t need teeth anymore, so they analyzed traces of carbon and oxygen in the fossils of both juvenile and adult dinos. It turns out different kinds of carbon and oxygen accumulate in plants and animals, so you can tell what an animal ate based on the levels of the different forms of these elements inside the animal. The team found that the shift in toothiness probably corresponded to a shift in diet: these dinosaurs ate anything they wanted as kids, then became strict vegetarians as adults. This change in lifestyle could be one way toothlessness evolves.

Birds still have some of the developmental pathways required to grow teeth -- they’re just switched off. This dinosaur isn’t a direct ancestor of birds, though. It’s more of a distant cousin, which means that this discovery isn’t a direct step on the path from pointy-toothed dinosaurs to toothless birds. But now we have a real-life example of one way toothlessness could have evolved, which will help paleontologists figure out how it happened to birds. Now if only we were as close to figuring out the antimatter mystery.

Thanks for watching this episode of SciShow News. And an extra special thanks to our President of Space, SR Foxley! Thanks SR for your continued support. If you want to help support SciShow, go to Patreon.com/SciShow, and if you just want to keep getting smarter with us, go to YouTube.com/SciShow and subscribe!