Questions That Have Definite Answers That We'll Never Know

[Terminal Blue]

If you could travel faster than light, then the event horizon wouldn't be an event horizon properly speaking; you could have faster than light trajectories that travel through and then out of it in a hyperbolic trajectory.

So, I kind of messed up there. I was working on some half-remembered things I'd absorbed from somewhere and which was way outside of my pay grade. For functional purposes, it's probably best to just forget the whole idea of travelling faster than light inside a black hole. I'm not an expert on any of this, I just find it really cool so, you know, I make mistakes.

But the problem is, again, spacetime inside a black hole is completely broken. It's not that the escape velocity of the black hole is faster than light, and it's not like if you go faster than light you could go back the way you came. Spatial dimensions as we understand them no longer exist in the warped space of the black hole. In essence, the direction you came into the hole doesn't exist any more. If you point your awesome FTL spaceship in what you think is that direction, you'll just drive into the singularity because that's what happens if you go in any direction. A black hole is kind of like its own little bubble universe where the only direction is down.

But black holes are incredibly weird. They are literally impossible things that break our understanding of the universe we live in. Although it's extremely likely that a black hole is just an inevitable one-way ticket to crushing death, there are definately weirder things people have speculated. For one, remember how singularities become rings when they spin. Well, if they spin incredibly fast they might stretch out to the point that you could fall through them rather than into them. In that case, you're probably still going to die but you might die in a far more bizarre way.

If you're past the event horizon there is no turning back as light can't escape from a black hole. Going faster than light around a black hole slows down time so I believe for every six months or so a year on earth will have passed.

You wouldn't need to be going faster than light (although in order to orbit a black hole you'd need to be travelling close to the speed of light and even then maintaining a stable orbit would be impossible as space starts to bend in close proximity to the event horizon, it's a region we call the ergosphere where some of the reality-warping properties of the black hole can be felt). By merely being close to the black hole your relative frame of temporal reference would slow down due to the immense gravity. If you got really close to the black hole, you could easily skip millions of years. But, because the black hole operates on the same frame of reference, this fact isn't going to save you. The black hole isn't going to evaporate before you can fall into it.

 

[Seanchaidh]

But the problem is, again, spacetime inside a black hole is completely broken. It's not that the escape velocity of the black hole is faster than light, and it's not like if you go faster than light you could go back the way you came. Spatial dimensions as we understand them no longer exist in the warped space of the black hole. In essence, the direction you came into the hole doesn't exist any more. If you point your awesome FTL spaceship in what you think is that direction, you'll just drive into the singularity because that's what happens if you go in any direction. A black hole is kind of like its own little bubble universe where the only direction is down.

These geometric properties of the universe are derived from a physics which absolutely proscribes FTL travel, and that proscription of FTL travel is interdependent on those geometric properties. The (Einsteinian) physical model as a whole and as a consequence its conclusions about the shape of spacetime in particular don't really say anything about what you can do or where you can go from anywhere if FTL travel is possible, as if FTL travel is possible then that physical model is false.

(although in order to orbit a black hole you'd need to be travelling close to the speed of light and even then maintaining a stable orbit would be impossible as space starts to bend in close proximity to the event horizon, it's a region we call the ergosphere where some of the reality-warping properties of the black hole can be felt

we're actually orbiting a black hole right now-- or at least, orbiting a body (the sun) that is orbiting a supermassive black hole (the center of our galaxy). If we were closer to it, we'd have to move faster in relation to it. It all depends on distance and the mass of the black hole; a smaller black hole, such as one that is 3.8 solar masses we could orbit pretty comfortably (I think?) at the same distance the Earth orbits the sun (albeit with shorter years).

 

[Satinavian]

Ok, as someone who actually did some work on black-hole-neutron-star interaction (though many years ago), i want to explain some things :

- Black holes originally were found as mathematical solutions in general relativity. At the time no one believed that those could exist and thought they showed a flaw in general relativity. Perople still explored the implications of those solutions, one of which is the event horizon. Obviously we know now far more, but a lot of the ideas around black holes were mathematical concepts first which now have been observed or not on actual examples.

- The Event horizon is the surface beyond which nothing that is not faster than light can ever escape. But that is a consequence born from the original math mentioned above. General Relativity also demands that anything carrying information can't travel faster than light. Combined that would mean "No information can ever leave a black hole". It is not difficult to see how that is equivalent to "We can't know what actually is beyond the event horizon".

- And it turns out that is true. Anything we ever have observed in regards to Black holes happens on the outside. Everything we can measure, happens on the outside. We don't really know if there is a singularity in there. In fact, other mathematical options that look exactly the same from the outside have been found as well. And that is even without considering that our theories might not be valid inside.

- And that is how we treat black holes in practice. We can't really know what is inside, but we sure know it behaves (on the outside) as if it had a pretty straithforward singularity inside that can be described with a couple of numbers, so we calculate it as if that were true. But we don't ever say that this is really true. Every prediction, every experiment, every observation is only for outside the event horizon and every theory is only applicable there and concerned with it.

- time slowing down : Yes, happens when you move faster and near great masses. When you reach light speed, time stands already still for you. But practically you can't do that anyway, because moving faster also increases your mass whch would approach infinity when you reach lightspeed. That is, if you have any rest mass. Which is why massless particles like photons can do that.

- "What happens when travelling faster than light" is not something physics makes any proper predictions for. Relativity says you just can't. If you assume it to explore the possibility as a thought experiment, the math gets soon so wonky and selfcontradictory that you still don't get any useful answers for anything. Everyone saying anything about what yould happen with FTL travel is always ignoring most of its implications and concentrating on just a few and the next person would get you a different answer. (Though variations of "You travel backward in time" or "time flows backward for you" are quite popular). Also Warp drives, wormholes ect. are technically not FTL travel as far as general relativity is concerned. Extrapolating those is fine and gets reasonable results.

- fun things happening around black holes : If you are near black holes, time slowes down. There will also be shear/tidal forces ripping everything apart so it is not something people would ever really want to do. This is one of the reasons why the question whether you die when you cross the event horizon or are inside is a tad pointless as you will likely be long dead before you get there. Furthermose, the flow of time becoming strange can make the question if someone is dead or alive quite difficult to answer. Now to the fun stuff. Rotating black holes have not just the event horizon but a region outside, where things already geht quite strange but which can be oserved, entered and also left, the so called ergosphere. Among other things, if you are really near to a rotating black hole, spacetime will not consist of one time and three space coordinates, but two time and two space coordinates. Also negative mass/energy is suddenly a thing. Keep in mind though that those are both model predictions as of now, our black hole observations are not good enough to test those yet, but in principle these things are observable and testable for us.

- There is also a lot stuff going on with quantum mechanics and black holes, entropy and black holes and how all of this works together. It is actually quite interestig as quantum mechanics and general relativity do contradict each other in some things, but the effect and their interactions are so minor that it is incredibly hard to measure what really happens in such cases. Black holes, which tend to blow up relativistic effect to an absurd degree are therefore quite interesting to study with this in mind.

 

[stroopwafel]

There is also a lot stuff going on with quantum mechanics and black holes, entropy and black holes and how all of this works together. It is actually quite interestig as quantum mechanics and general relativity do contradict each other in some things, but the effect and their interactions are so minor that it is incredibly hard to measure what really happens in such cases. Black holes, which tend to blow up relativistic effect to an absurd degree are therefore quite interesting to study with this in mind.

It always surprised me that if you break down the essential elements that enabled life like quarks ie the building blocks of subatomic particles that originated since the big bang and higgsbosons that give particles their mass and is part of the higgsfield present in all of the known universe that you start to have the same kind of contradictions in existing models as celestial bodies which scope and scale defies belief. We are truly made of stardust!

 

[BrawlMan]

How many licks does it take to get to the center of a Tootsie-Pop?

 

[XsjadoBlayde]

Great to see discussion of black holes, fascinating horrors that they are!

In the same vein of curiosity, been wondering for a while, as black holes are pulling in light so strongly to appear as they are, if hypothetically we could find a way of observing and recording even just 10 seconds of footage of the - for lack of a better word - "sky" from beneath the event horizon with the clarity of the human eye, what would it look like? I can only assume it won't be black like the outside, but would it be just the night's sky? Or would the natural intensity of the pull as it is present an incredibly ominous bright white/haze or psychedelic mix of curling colours downward, or something visually far more unimaginable?

Could gravity and light be intrinsically linked through ways we are yet to begin to understand?

Also, gravitational waves and black holes colliding in general are incredibly fascinating and thought provoking events which should be explored far more in sci-fi than I have yet to see. There's like a million questions to be had in this area and I don't know where to start.

How many licks does it take to get to the center of a Tootsie-Pop?

Now hey, is there anything stopping you from performing the tests yourself to find out this one? For science of course!

And for your Biggie/Tupac question, a recent documentary may be of interest to you perhaps;

Watch the trailer for Nick Broomfield's new Suge Knight documentary, 'Last Man Standing'

The first trailer has been released for new documentary 'Last Man Standing: Suge Knight And The Murders Of Biggie & Tupac' - watch it here.

www.nme.com

 

[BrawlMan]

Great to see discussion of black holes, fascinating horrors that they are!

In the same vein of curiosity, been wondering for a while, as black holes are pulling in light so strongly to appear as they are, if hypothetically we could find a way of observing and recording even just 10 seconds of footage of the - for lack of a better word - "sky" from beneath the event horizon with the clarity of the human eye, what would it look like? I can only assume it won't be black like the outside, but would it be just the night's sky? Or would the natural intensity of the pull as it is present an incredibly ominous bright white/haze or psychedelic mix of curling colours downward, or something visually far more unimaginable?

Could gravity and light be intrinsically linked through ways we are yet to begin to understand?

Also, gravitational waves and black holes colliding in general are incredibly fascinating and thought provoking events which should be explored far more in sci-fi than I have yet to see. There's like a million questions to be had in this area and I don't know where to start.



Now hey, is there anything stopping you from performing the tests yourself to find out this one? For science of course!

And for your Biggie/Tupac question, a recent documentary may be of interest to you perhaps;

Watch the trailer for Nick Broomfield's new Suge Knight documentary, 'Last Man Standing'

The first trailer has been released for new documentary 'Last Man Standing: Suge Knight And The Murders Of Biggie & Tupac' - watch it here.

www.nme.com

I appreciate the video, I will look at it later. As for the tootsie pop, I've tried several times, but never held the attention span or got bored. I would usually get bored and stop between 15 to 20 minutes afterward.

 

[Drathnoxis]

How many licks does it take to get to the center of a Tootsie-Pop?

Between 144 and 411 according to several different studies.

 

[SckizoBoy]

What is the origin of the first widely used spoken language and how did it come about?

 

[BrawlMan]

Between 144 and 411 according to several different studies.

Okay then.

 

[Offworlder]

Not to come off as depressing, but who shot Biggie and 2Pac?

I can't remember where I read/saw it, but I'm pretty sure they narrowed who shot 2Pac down to one guy. It was a Bloods gang member who had beef with 2Pac and was on the Vegas strip at the same time 2Pac was. I'll see if I can find it.

Biggie on the other hand could have been anyone. He was leaving a massive party in LA, enemy turf, and was driving through a huge crowd of people when he got shot. Sad thing is, it's widely believed the hit was for Diddy, not Biggie.

 

[OblongYellow]

This is probably weird and not so traditional, as well as pretty vague but here's one:

The question of whether there are life forms in other galaxies and what life is like. I mean, a square to us is a square but what is its equivalent there? Will it be objects we recognize or objects totally new (just like in those movies where people are locked away and don't know the things on earth are and its functions). We know how a pair of eyes look, but do they have the same?

Dark Matter might also have definite answers that we'll never know for now.