Praseodymium - Periodic Table of Videos

[BelieveIt7]

Is it Acylicate(Asilicate, I don't know) or Acrylate that slows down the speed of light?

[AgentCROCODILE]

So it lowers the speed of light by 299,492,458 m/s?

[molfluon]

It's also present in lighter flints. Apparently. Although the actual Wikipedia article didn't actually say it was deliberately added to the recipe for modern artificial flints to improve their properties.

Maybe that's why it wasn't mentioned. Anybody care to enlighten?

[dajwilkinson]

@molfluon I suspect because on striking any of the earlier lanthanides - or attacking them with the grinding wheel found in most disposable lighters - you get a spark (any of these metals as a powder will be pyrophoric) and in this application it is not important to separate/purify them to any great extent, hence the presence of praseodymium.

[schmidtbag]

holy crap 300m/s? isn't that slower than sound?

[Creepyseven]

@schmidtbag

following rule of thumb speed of light is 333 m/s fast so you are right it is slower ( i was amazed too)

[liam7morris]

@Creepyseven I think you mean speed of sound is 333m/s?

[Creepyseven]

@liam7morris

oh of course i mean speed of sound ^^ thanks for correcting me !

[Bjo15]

@liam7morris 340.29 is the speed if sound

[liam7morris]

@Bjo15 You cannot have an exact figure it varies on a number of variables, atmospheric pressure for example.

[Bjo15]

@liam7morris thats tha zoundz in vacuuum

[liam7morris]

@Bjo15 you cannot hear anything in a vacuum and you cannot get sound as there are no particles in a vacuum

[Bjo15]

@liam7morris i was just joking liam ;)

miss

[KameronID]

Sick!

[CrAzYcArNiE08]

oh and this video is a tad old, compared to the ever changing science world. The speed I believe was 1/2 a mile an hour. The light is slowed down by passing it through a cloud a super cooled NA. Then speed back up by hitting it with a laser. They are talking about ways to make microchips and such obsolete in computers ways of processing information, and using a series of pulses to the computing. Idk much though.

[derickhaywood]

@CrAzYcArNiE08 1/2 a mile an hour seems sort of... retarded ? 30 mph seems more likely

[CrAzYcArNiE08]

@derickhaywood well to me 30 mph hour sounds retarted, it was in a tube not a freaking street.

[1993gandy]

i thought scientists slowed light down to about 30 MPH

[CrAzYcArNiE08]

@1993gandy less actually

[1993gandy]

@CrAzYcArNiE08 last i heard was 30 MPH :P

[T0mNZ]

Id like to see the silicate, there would be some serious refraction.

[ersilcoff]

i did my 1st reaction with terbium on monday and my 1st reaction with praseodymium today. as someone who's entire history is pretty much limited to the 2p elements, i would have been pretty nonchalant about using these compounds. because of this series i actually found these reactions a exciting!

ytterbium next week!!!

[broadwaygirl0307]

Thank You so much!! I have this element for a project and now i have everything i need

[TheCaptainLulz]

they have actually used sodium vapour for the light experement and have been able to get photons to almost completely stop (5mm/minute).

[Drag0nfoxx]

300 m/s? That slower than sound in the air!

[Fisherdec]

light has already been completely stopped

[Onyxwolf3]

yeah by super cold sodium atoms and also a mixture of rubidium/helium gas. the sodium stopped all the light, but the rubidium/helium only got half (but the rubidium/helium experiment didn't need a vacuum and atoms that are withing one billionth of 0K).

[ValiantArrow]

What does frozen light look like?

[666MONKEYPORN]

it doesn't look like anything. the only reason you can see anything is because of light traveling into your eye and exciting photoreceptive cells in your retina. if the light isn't moving, you can't see it.

[ValiantArrow]

Good point...

[Chi7es]

light frozen for a fraction of a fraction of a second looks like light coming from the light source a tad later than you would have expected it. With common sense thats how thye found they were successful.

[dharmafreak]

wow, only 300m/s?! cool

[TallaFerro14]

but I never new it could be slowed that much !

thats close to the speed of sound !!!!!!!!!!!

[caiosnif]

Wikipedia says some people stopped it.

[liam7morris]

wikipedia lies then

[666MONKEYPORN]

no, people have. it's just been for a fraction of a second, and requires some hardcore facilities.

[nintendowns]

you can. the speed of light constant assumes a perfect vacuum, so light travels slower in a non vacuum.

[etraise2]

@nintendowns Slow down the speed of light? Why would you want to do that?

[taeke18]

@etraise2 Well it can be interesting if you want to analyse some data what came from a collision with a specific particle. This might effect the light and if you slow th elight down its easyer to analyse i suppose?

[elflordbob1]

@nintendowns

it doesnt travel slower

speed of light is a constant

in a non vacume it bounces off many particles taking it longer to reach its destination

[ArsonistInUrFirewall]

@nintendowns

It still travels with the same speed in different media, but not is a straight line.

[Pikhand]

Of course lenses do only function because of the fact that light slows down in an optical denser medium (c1/c2=n1/n2).

[PaxTorumin]

You are correct. I was wrong. I spoke too soon and didn't check my answer.

D'OH!

[Anamonopeia]

I am sure that with "lower the speed of light to 300 m/s", he meant to say lower the speed at which light is percieved, just that. A slight problem of phrasing.

[PaxTorumin]

Furthermore, lenses of ANY kind do not function by slowing the speed of light, but by refracting it; changing the angle at which is exits the other side of the lense.

Eye glasses work by essentially deforming the lightwave to compensate for the deformed lense in your eye, thus cancelling out the distortion and improving visual accuity.

The speed of light has, as far as I know, nothing at all to do with the way a lense works. They would function exactly the same if light traveled at 0.3 m/s.

[BirdValiant]

Indexes of refraction are found by comparing the speed of light in the medium in question and a vacuum. That is, n = c/v. If either c changes (which it isn't going to) or v, then n will.

...

[PaxTorumin]

I'm afraid I don't know what n and v mean, but I'm assuming that it refutes my claim of the speed of light in a medium not having anything to do with the lenses work.

After looking up lenses just a couple days after posting I realized I was totally wrong, but forgot to admit my error.

Thank you for addressing my mistake. Sometimes people need to be told "WAIT A SECOND, YOU'RE AN IDIOT!"

Especially people like me, who are sometimes too confident in themselves too double check their answers.

[BirdValiant]

IF YOUTUBE WILL ALLOW ME TO COMMENT... :(

Thanks for admitting your mistake. I try not to just call people idiots or whatever, since that rarely accomplishes anything.

Anyway, if you check out Snell's law (I really don't want to type this out for the third time and not have it get posted successfully), then you will notice that the only thing that matters is the ratio of the velocities on both sides of the medium.

[PaxTorumin]

In matters of philosophy, sociology, politics, morality, and Star Trek vs Star Wars I will not readily admit a mistake.

However, any question about these subjects can have multiple answers. With science it's different. You're either right, or you're wrong. Like math. No middle ground.

There is no point in attempting to defend one's position when the answer is already known and can be looked up.

I asked science the answer. It told me to wait a second because I was an idiot.

[PaxTorumin]

I also learned a trick that usually gets youtube to post all my comments.

After you hit "Post Comment" wait for button to say Comment Posted," then count to five (slowly).

It seems youtube doesn't like it when people hit refresh too quickly after posting.

[PaxTorumin]

Ee, no. WRONG. The speed of light is NOT variable. Light always travels at 299,792,458 meters per second.

Rather, the illusion of slowing the speed of light is achieved because it bounces around inside the medium so much that it's overall progression is slowed.

However, if you were measuring the speed of any given photon/light wave passing through any given medium it's speed would never drop below 299,792,458 m/s. Ever.

[DuskY1991]

Changing the speed of light? Lol i never knew that was possible

[jtoksa]

> Changing the speed of light? Lol i never

> knew that was possible

Every time you see light refracting, it is because the speed of light changes as it enters from one medium to another, and the change in the speed of light changes the direction of the wavefront.

Eye glasses and cameras would not work if the speed of light was constant.

[DuskY1991]

Thanks for explaining this man. I didn't realise it really lowered the speed of light. I just thought it changed the direction or something.

[saxoman1]

300 m/s?????? that's pretty ridiculous considering it once was about 300,000,000 m/s!!!

I never knew it could be slowed that much (slower than sound for pete's sake!)

I can imagine, "you hear the thunder THEN you see the lightning" xD. anywayz 5 stars

[robotwarsfan03]

kool