Why Things Look That Way Under a Blacklight

Fluorescence isn't just a cool effect that turns your white T-shirt neon purple under a black light. Its discovery opened our eyes to a whole new field of science and engineering. And it's all thanks to a crystal called fluorite.

Hosted by: Hank Green (he/him)
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[DragonGirlFire]

Hank getting so excited about the topic that he has something to add off script is probably my favorite part.

[chursius]

Hank, I'm a researcher at Oregon State University developing a diagnostic assay for Agrobactetium tumefaciens (bacteria causing crown gall disease) using a CRISPR-based technique that acts almost exactly how you described in your "off script" bit. It was very cool to hear you talk about that!

[renocence]

Hank looking like he's about to go super Saiyan during that off script moment. You see the energy of knowledge building inside of him, hearken all who enter here.

[jacobekker]

I had a retinal detachment that ended up resulting in having my lens removed. Now I can see in the UV spectrum, which made the dark rides at Disneyland very interesting!

[OMGitshimitis]

For those who are interested the reason Phosphorescent chemicals release light over a longer time is that the different energy levels the electron sits at in a Phosphorescent chemicals also have different angular momentums so to transition between the states requires more random luck.

[annekeener]

Fluorescence is also used for multiple microscopy techniques and molecule labeling tricks. GFP is green fluorescent protein and it is commonly used to label molecules. Fluorescence resonance energy transfer or FRET literally uses the fact that fluorescent molecules release lower wavelengths of light to test if two molecules are interacting by having one molecule with a label that excites a a specific wavelength of light and emits light at a wavelength that will excite a molecule with a second label, creating 2 different colors that can be detected if the molecules are in close proximity or directly interacting.

[troydorr]

Hank is by far my favorite host of SciShow! You rock Hank!

[BanjoGate]

More 'not in the script' stuff! I like the way you present when not reading off the teleprompter! <3

[cassandrakarpinski]

Fluorescence is also useful for analytical chemistry. A fluorospectrophotometer can be used to determine the quantity of a fluorescent molecule within a sample (sometimes with a standard curve for calibration). It differs from standard spectrophotometers by having the detector and source set to different wavelengths (in spectrophotometers, these are set to the same wavelength and the change in intensity gives the absorption, and thus we can calculate the concentration). The sample absorbs the source wavelength and then the detector measures the intensity of the fluorescent wavelength to determine the concentration (which is where the standard curve comes in. By measuring known concentrations of the molecule in question we can plot a graph, then utilise the line and/or formula of the line to convert the fluorescence of the sample into a concentration)

[CrossStCroix]

This episode _rocked_ . A _shining_ example of SciShow content

[zacharydefeciani]

This set is giving Technology Connections

[SmilesBot]

After having an artificial lens put in my eye to address a juvenile cataract (T1 Diabetic), that eye now sees slightly past the normal visible color spectrum. I see more purples and blues in that eye and more than other people, but here’s the really weird part: a black light looks light a normal fluorescent light to me, just with a hint of lavender color. Most things don’t glow the same way either unless I close that eye and look at it with only my natural lensed eye. Makes cosmic bowling really trippy.

[ellieshine]

I use sodium fluorescein on people's eyes.
When stored dry, it's orange.
When hydrated, mixed with the tear layer on a person's eyeball, it looks yellow.
When illuminated with blue light, it glows green.
Very useful for assessing the fit of contact lenses, or for highlighting dry patches on the eye!

[jjmetrejhon]

1:17 I have subtitles so I knew the punchline but Hank's delivery still made me laugh out loud

[Add_Infinitum]

5:59 I thought he was about to say "and THAT'S pretty cool."

[makego]

It's also interesting to note why fluorescent materials "pop" more under sunlight. Other materials are reflecting a certain amount, but a fluorescent surface next to them is both reflecting visible spectrum and radiating _more_ visible light energy that it's grabbing from the UV domain.

[rainbowslinkies]

"glow in the dark stars in your childhood bedroom"

...yes, my childhood bedroom wall only 🤣

[grumblefkitty]

fluorite was already my fav mineral. i knew some of this, but not the medical applications. this is awesome!

[cachecow]

I prefer the soft glow of radium in my watches and dyes

[Adventurealliancekerala]

Fluorite was just minding its business as a crystal, and now it’s a blacklight celebrity. What a flex!