How Does Gravity Escape A Black Hole?

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Fact: in a black hole, all of the mass is concentrated at the singularity at the very center. Fact: every black hole singularity is surrounded by an event horizon. Nothing can escape from within the event horizon unless it can travel faster than light. Fact: gravity travels at the speed of light. So how does a black hole manage to communicate its gravitational force to the outside universe? How does gravity escape a black hole?

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Hosted by Matt O'Dowd
Written by Matt O'Dowd
Post Production by Leonardo Scholzer, Yago Ballarini, Pedro Osinski, Adriano Leal & Stephanie Faria
GFX Visualizations: Ajay Manuel
Directed by Andrew Kornhaber
Assistant Producer: Setare Gholipour
Executive Producers: Eric Brown & Andrew Kornhaber
Executives in Charge (PBS): Adam Dylewski, Maribel Lopez
Director of Programming (PBS): Gabrielle Ewing

Spacetime is produced by Kornhaber Brown for PBS Digital Studios.
This program is produced by Kornhaber Brown, which is solely responsible for its content.
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[TheBuzzBen]

Question. What happens if a gravitational wave passes through a black hole? Would we have gravitational lensing of gravity? If so, can gravity be focused on a single point making a virtual black hole without mass?

[dannymac]

Fact: PBS Space Time is a black hole I’m always happy to fall into. Captivating, radiating information constantly…it fits.

This just made this whole "imprinted on the surface of the event horizon" thing click for me. I simply hadn't connected the dots between that, and the infinitely stretched light. Great video 💡

[Themaniacis_back]

I have the utmost respect for any channel that is willing to admit when they made a mistake and correct themselves. It seems like so many are terrified to admit when they are wrong these days. It's okay to be wrong sometimes. We are human. Anyways, keep up the great work.

[siahenderson]

I wanna take a moment to appreciate Matt .he has unknowingly been my teacher since I was 15...I'm 22 now and a grad student..
Videos like this teach more than schools

[syntaera]

For SR/GR, it's more helpful to view 'c' not as a speed, but as a geometric *conversion* factor between distances and times in a four-dimensional space-time. The 'speed' of light is an emergent phenomenon of treating different speeds as merely relative rotations of an object into spatial directions and away from the time-oriented observer/rest frame. A 90 degree rotation away from travelling 1 second per second through time results in an apparent motion of 299792458m per second in space - while simultaneously extruding the observed travel-direction length backwards into the time direction, resulting in observed length contraction. Treating 'c' as a mere speed is easier mentally, but ultimately makes SR/GR harder to understand.

[j.d.]

How does gravity escape a black hole? Very, very carefully.

[Cucui]

I play a game with these videos: how far into it can I get before I can feel my brain leaking out my ears. I made it almost 7 minutes with this one. To be clear I LOVE these videos and I learn a lot and Mr narrator guy does an excellent job explaining profoundly complex topics. It's just that a lot of these topics are simply mind-puddling.

[ananya.a]

This video blew out half of my brains, and the other half was blown away after reading the comments. People who can make sense of this and then produce more speculations and theories are geniuses. Thank you PBS Space Time for making this video! :)

[DrZedDrZedDrZed]

I've got this pet theory I keep knocking around my head that gravity is the geometric "buffering capacity" of 3 dimensional space. As in, the background that all quantum fields depend on and exist within, can only communicate their overlapping contents so quickly to neighbouring regions of space, like bottlenecks in transmission speeds. Black holes are simply what you get when the informational content of a 3D region of space exceeds that limit. Transmission fails, and that critical quantity of mass/energy gets "stuck" in relation itself (what I find most fascinating about black holes is that they can MOVE. Implying that they aren't tears in the fabric of space, but tears in the relationships between the mass/energy that fills it).

I find this "buffering capacity" view a compelling analogy because with it, you get causal asymmetries that see different regions of space experience communicability at different rates, which creates the time gradient that is the "force" of gravity in GR. You also get the inverse square law of gravity's influence, if you consider, like an infinitely branching network, communication bottlenecks dilute the further out from the source you get, which itself answers some of the mystery of gravity's relative weakness. It also perfectly encapsulates the equivalence of gravity and acceleration, if, when picturing an accelerating reference frame, you imagine an asymmetrical and exponential compounding of information accumulating in the direction of the source of the thrust. The equivalence between the speed of light and gravitational waves fits in just as well, when you consider that that speed simply IS the ability of a region of space to communicate to any other regions of space, its constitution. Just feels like it fits together so succinctly. Especially in conjunction with some of the more philosophical implications of QM, mainly that any component pieces within the universe need to communicate their existence to neighbouring component pieces in order to become determinately "real". That's my 2 cents!

[qazxswedcish]

For me, it helps to think of the gravitational effect of getting pulled by spacetime into a black hole as being similar to getting pulled by a chain. Only the first link interacts with the pull source, in this case the singulaity, and only the last link interacts with yourself, but by each link interacting with the ones next to it you still feel the effect.

[mickelodiansurname]

This is something I wondered when I was a kid and my physics teacher at the time stated it was compelling evidence of why gravity permeates instantly. He was wrong but you can't really fault his logic... it made sense to me at the time.

[evasilvertant]

I cannot find his account any longer, but I followed a physicist named Harry McLaughlin if I remember correctly, who studies black holes, and he has always argued against physical singularities, and explained how the black hole mass density is distributed over the volume of a black hole. He always made a lot of sense to me, but I am not a physicist nor do I have enough mathematical insight to conclude for myself whether a singularity or distributed mass density makes more sense. Either way, I was a bit surprised when you stated a singularity as fact at the beginning of the video. As far as I can gather, there isn’t necessarily consensus on that in the physics community.

[christianczekalla]

I like the way you guys handle mistakes in past episodes. A good example for feedback being taken seriously.

[sebastiendumais]

I keep wondering, wouldn't it be "simpler" to consider that gravity is actually not mediated by a particle and the rest of the forces are actually manifestations of space time being modulated in different ways (eg: electromagnetism is a manifestation of how space time is affected by charged particles)?

[DanHarkless_Halloween_YTPs_etc]

8:06 - "Interactions between particles result from the sum of all virtual particle interactions, possible and impossible, and the speed of light limit actually emerges in a sort of statistical way." 🤯 This really is the best channel on YouTube (according to my information-theoretical measurements, anyhow)!

[sid]

This episode blew me away.. Black holes are simply collapsing stars relatavistically frozen in time forever, exerting the gravity field it had the instant before it went past our current theories. Fascinating how information emerges from "simple" math equations!

[RC]

If the gravity we feel from a black hole is actually from past interactions with the mass, then does that mean that a black hole can have an asymmetric gravitational field? For instance, suppose we kept throwing moons at the left side of a non-rotating black hole. Would the black hole seem to be heavier on the left side since the past mass was added there?

[pesilaratnayake]

Question: If an outside observer sees an object slow as it approaches the event horizon of a black hole, and the radius of the black hole event horizon grows as mass falls into it, what happens to the object? Does it disappear as the black hole expands, or does it move outwards with the event horizon? Or do we never observe black hole expansion since we never see anything enter the black hole?

[GarrettJohnson]

Kudos to the simulation of the star collapsing into a black hole and the slowing of space time at each reduction till it finally slows so much that we never see it. Truly amazing stuff and it really helped to understand that the space-time warp could itself cause the fact that nothing comes back from the even horizon because it would simply take infinite time...