Black Holes

[thekeanmoses]

2:17 if it aint white it aint righ.lol I <3 Khan Academy

[jonjonjon1370]

if black holes can suck in light, wouldnt that mean gravity is faster then light?

[eirh]

@jonjonjon1370 not faster, but the force of the gravity can bend the way that the photons "fly", so if the gravity is high enough it gets bended so far, that it gets "sucked" in by the black hole. Maybe you can visualize it by thinking of a magnet and a rolling metal ball. It is pretty awesome if you think about it.

[jonjonjon1370]

@eirh thanks! made perfect sense!

[OregonCoastGhost]

I think I could get more out of these videos if I wasn't constantly watching and waiting for him to go back and cross his T's! haha

[KillaNCDealer]

-FUCKING HEAD EXPLODES-

[elfstomper4444]

awesome

[ozzycriss]

So what your saying is a black hole is just a mathematical equation on a piece of paper .

[Deicidead]

@ozzycriss It was in the beginning but in the recent years we have observation that confirms it.

[ozzycriss]

@Deicidead i would say its still an Interpretation of energetic activity , these things are so far away that observation almost zero

[GreatAgentD]

I go to KhanAcademy to check some subjects I'm struggling with and then I simply get caught by these much more interesting videos... whatdo?

[RyomaE28]

@GreatAgentD i noe the same thing happens to me...

[LiberalJerseyman]

@GreatAgentD Ha same here. Whenever I do astronomy homework it takes me hours just because I start reading/watching interesting things about science.

[tuzobarca]

what i don't get is that in "fabric of the cosmos" the author brian greene, says that black holes don't actually exist because there is not enough time for one to form, it takes an infinite amount of time for it to form so technically they don't exist?

[INMATE2468]

@rmhism. Your really really stupid, do you even know what a black hole is??? It theoretically falls victim to its own gravity and with no force to keep it stable, it can infact have infinite dense.

[rmhism]

Black holes don't have "infinite density". A black hole with mass a hundred million suns will have about the same density as water.

[mistaSIRA]

this dude is so fuckin smart. its really ridiculous

[MrMonCinnamon]

My science teacher told me one tablespoon of neutron star matter weighs as much as or more than all the vehicles in North America. Is that true?

[Randomsurprise2]

@MrMonCinnamon! I think that a golf-ball sized piece of a neutron star weighs as much as 1 billion elephants. You do the math.

[hahs4]

i decided to spend my summer learning from sal,I wanna become a well-rounded individual before college and Sal has topics about everything

[hedonism13]

Speaking of Black Holes, how do you get the badges?

[MrTechnoAlex]

@hedonism13

That's for YOU to discover ;-D

[randomwindowsstuffz]

@hedonism13 You can complete all the exercises or you can get a billion energy. (Good luck...)

[KnaberArtist]

gah. Neutron Stars are City-Sized!? That's TINY! :-P

[satch1011]

what program is this?

[tIs4gatorbait]

In other words, the escape velocity beyond the event horizon is greater than the speed of light.

Don't know if he says this at any point, but it's generally believed that there's a supermassive black hole at the center of most if not all galaxies, including our own.

If you get caught in one you get "spagettified". Youtube search it for a depiction

[xXSparky117Xx]

If you find this interesting, look up the "black hole information loss paradox."

[crumcon]

finally i have the understanding of black hole beside my girlfriend's

[ShaheemA13]

in future videos, if you have the time, can you please post the links to where you got the pictures from? because you always seem to get great graphics and i would like to be able to view/save them afterwards. thanks!

[ashfaq0606014]

jose 

[ashfaq0606014]

jose

[jiberish001]

You should make it clear that when you say "infinite density" you don't mean never ending. Scientist use the word 'infinite' to describe something that is incalculable.

[Sconz32]

I just don't understand how the singularity can have infinite mass. if it's made up of the mass of a star then that is a huge amount of mass, but it sure as hell isn't infinite.

[GammahooX]

@Sconz32 it doesn' have an infinite amount of mass. A black hole has the same gravitation as the star that it came from. But the mass is at an infinitely small place. The densitiy is infinitely small.

[dalcde]

Thanks to Sal, I am becoming a knowledge black hole.

[0HellBlaze0]

these videos are so pointless for me but soo awesome =D

[barneysixx]

@0HellBlaze0 no it isnt

it essential to our understanding of the universe

[LiberalJerseyman]

@0HellBlaze0 Why are they pointless?

[ApocDevTeam]

@0HellBlaze0

self education is never worthless

[stevenballa1]

@ApocDevTeam True except this isn't self education he is teaching us

[ozzycriss]

A black hole = mathematical equation on paper , no one has ever seen what you call a black hole . This mathematical equation is to try explain what we think may be happening . Theory does not = fact . These theorems of singularity ect are based on the assumption of gravitational forces . Plasma cosmology by contrast, acknowledges the electrodynamic nature of the universe . Gravity and inertia are NOT the only forces at work . WE know nothing but the very basics

[Plutoniummatt]

@ozzycriss

A black hole = has been observed indirectly, no one can see one directly cuz you literally cant.

[Metropolitian]

@Plutoniummatt I have to second Plutoniummatt. Ozzycriss's argument is written as if it's hard facts he's telling, but he is kind of wrong.

Black holes have been observed already, by staring at stars in the night sky for several to hundreds of days, in a case of which a black hole is present, these stars will orbit around a point in the sky where there's no light being emitted from. This means that there's a superdense/heavy body out there. We call it a black hole.

[ozzycriss]

@Plutoniummatt A black hole = an interpretation of a source of energetic activity

Theory does not = fact . The existence (according to most physicists) of a black hole is part of a valid theory. But a scientific theory must exclude solutions that violate basic physical principles or yield inconsistent mathematics .

[Plutoniummatt]

@ozzycriss

I don't need a lecture on physics thanks, im perfectly happy with receiving that from my university

[ozzycriss]

@Plutoniummatt And what university would that be , if you don't mind me asking . As a side note a lecture is an oral presentation .

[smicha7]

Great video Sal. Guys, see this: watch?v=cW7BvabYnn8

[iGary]

Space is utterly fascinating. This is probably one of my favourite playlists you've made, Sal. 

[eljpayne]

Have been waiting for this topic xD

[Rivoluzzjoni]

im digging this new playlist your making

ive said it before and ill say it again

you are god

[Mal1234567]

I don't see how three solar masses, even compressed down to a point called a singularity, has the ability to swallow light.

[rafaravioli]

@Mal1234567

Well, if you consider that light is at least partly a particle, it makes perfect sense that with strong enough gravity, you could pull particles of light toward or away from something.

[Mal1234567]

@rafaravioli 3 solar masses only make for that much gravitational pull, density does not affect the amount of gravitational pull, only the localization of the pull.

[rafaravioli]

@Mal1234567

Mass, however, does increase gravitational pull. And three solar masses combined is a huge amount of mass, regardless of its density.

[Mal1234567]

@rafaravioli Just outside the event horizon, the black hole in my example has the same gravitational pull as 3 solar masses.

[monkeydanny123]

@Mal1234567

the only black hole that sounds reasonable is the one up my ass.

[superdau]

@Mal1234567

That's wrong. At this close distances the shape of the mass has to be taken into account. While at long range a 3 solar masses star and a 3 solar masses black hole have the same "pull", this is not true up close. A star is huge compared to a black hole, so there's always a "far" side of the star, which means part of the matter (and thereby mass) is much farther away. As gravitational pull decreases with the square of the distance, this makes a huge difference!

[Mal1234567]

@superdau I see what you're saying, although for Newton the center of the mass is considered the center of attraction. Maybe that's why Newton was wrong?

[superdau]

@Mal1234567

Too, late. Now there's already a video on it ;-)

[Mal1234567]

@rafaravioli Yes, with strong enough gravity, but 3 solar masses does not possess that much gravitational attraction.

[xcelpast]

oh my he said quantum...which i have no understanding..maybe explain it in another video?

[MaNeSh15]

so basically based on the singularity thing, it means even the laws of physics will not work in black holes if that makes sense

[JayDee98765]

Into the abyss of the unimaginable gravity, warping time and space. Into blackness. Into nothing.

Black holes.

[bacamd]

One request:

QUASARS QUASARS QUASARS QUASARS QUASARS.

Thanks!!!

[odaymustdie]

@bacamd quasars are a supermassive blackhole "feeding" on ISM prior to galaxy formation.

[Menegoth]

I can't wait for the quasar vid!

[FreemanFighter94]

Best playlist evar.

[lonnyleogcalex94lol]

Amazing O__O

[Haradin32]

what happens when a black hole meets a black hole?

[theinquisitor]

@Haradin32, as I understand it, they will orbit each other in an ever decreasing spiral until they collide and form a single black hole with the combined mass of them both.

[odaymustdie]

@theinquisitor The mass will be less than the combined two masses. E=mc2

[UniversumExNihilo]

@Haradin32

They typically either orbit each other (like a binary star system), or they combine into a black hole with a mass equal to the sum of the previous two masses, emitting huge gamma burst all the way.

[Haradin32]

@UniversumExNihilo that second bit sounds quite dangerous! I hope that never happens near earth.

[51674]

@Haradin32 they have sex and make 3 baby black holes.

[silencedfable]

@Haradin32 becomes a super massive black hole or they do the black hole waltz (I think)

[Zappyguy111]

I never tire listing people talk about black holes

[TheScottKirk]

@Zappyguy111 Eh, super-gravity. . . not very interesting to me. Although I would listen to Sal explain how paint dries on the wall.

[Zappyguy111]

@TheScottKirk

You probably work with black holes everyday. Would that be a correct assumption?

[TheScottKirk]

@Zappyguy111 Just because I think the subject itself is somewhat boring, doesn't mean that you have to try to imply anything.

[Zappyguy111]

@TheScottKirk

Now implying is too strong of a word to what I was suggesting.

It was a mere assumption. By the way, if this bores you why are you watching it?

[TheScottKirk]

@Zappyguy111 I was watching the cosmological playlist on Sal's channel. I was waiting for quasars at the time (which I found out wasn't uploaded until recently) and this came up.

Now I've seen the quasar video and I'm happy.

[odaymustdie]

@Zappyguy111 How about people 1000 years ago predicted blackholes, would you believe that?

[Zappyguy111]

@odaymustdie

With a grain of salt

[Zappyguy111]

@odaymustdie

Well to say predict, means that they knew almost for certain. Theorise I think would be a more accurate term.

[Mal1234567]

how can something with 3-4 times the mass of the sun end up with infinite mass?

[floopsie666]

@Mal1234567 Infinite density...it has finite mass.....

[kaczurda]

@Mal1234567 there's no such thing as infinite mass. mass is always finite because it cannot be created nor destroyed.

[Cepacol2]

@kaczurda Mass can be destroyed - rather, converted into energy. E = MC^2 is the relationship between energy and mass. Although mass can be destroyed, it is conserved, simply through another mean (in this case, energy).

[Mal1234567]

@kaczurda 3:54 "infinite mass density."

[kaczurda]

@Mal1234567 Oh. This is because a black hole has an extremely large mass and zero volume. Density = mass/volume, which is undefined, therefore infinite. Also, since Newton's Law states that the force of gravity between 2 masses is G(Mm)/r^2, when you set the radius = zero, the result is undefined (cannot divide by zero). This is why black holes have infinite curvature in the space-time continuum. As Khan mentioned, this is the singularity. Known math equations break down at the singularity.

[weweallthewayhome]

@kaczurda you can't use newtonian mechanics when you study black holes, you have to use general relativity. the problem arises because the metric assumes a form similar to that of newton's where you end up dividing by zero.

[ultimatebas]

@Mal1234567 because it is infinitly small?

[Mal1234567]

@ultimatebas Yes, it is infinitely small because it has infinite density. But how does infinite mass come into this?

[bacamd]

@Mal1234567 He says "infinite mass density" meaning that the density of the mass is infinite. The mass itself is unknown, because it is unknown what exactly happens to anything which is sucked into the black hole. The mass could be infinite theoretically.

[ThatGuyTheyareAfter]

@bacamd Using the formula for gravitational energy: Fg= G*(m1*m2)/r^2 if the black hole is in orbit with another object of known mass one could approximate a mass for the black hole. since mass is directly related to gravitational pull that seems pretty accurate

[blueshift314]

@bacamd the mass isn't infinite. All blackholes would be one size if this were the case and/or the blackhole would consume the entire universe. however there are blackholes of varying sizes which indicates that the mass is finite (i would think this is obvious). I also recently read somewhere that scientists figured out that the volume isn't at one single point, rather just a very, very tiny area.

[weweallthewayhome]

@blueshift314 that scientist was later proven wrong, general relativity requires it to be a singularity (no volume)

[bacamd]

@Mal1234567 The gravitational pressure will force the neutrons to degenerate (essentially, just combine into a single point) at which point a black hole will form, which has an infinite mass density, meaning that the density of its mass is infinite, which is possible because the singularity is infinitely small.