What happens when you fall into a black hole?

Falling into a black hole is a science fiction favorite. In this video, Fermilab’s Dr. Don Lincoln tells you what it’s really like, telling the facts and dispelling fiction. (Hint: avoid it if at all possible.)

What are black holes?

Test of relativity

Fermilab physics 101:

Fermilab home page:

[talkingmudcrab]

It depends on the black hole. For instance I fell into a Black Hole called "Indiana" and outside observers saw me build a family and buy a pickup truck.

[TerryBollinger]

4:07 "As the object gets very close to the event horizon, a distant observer can see the time between blinks take a thousand years, then a million, and eventually longer than the lifetime of the universe." Five other fun effects often overlooked when falling into a black hole are (1) tunnel vision, (2) UV obliteration, (3) quantum orbiting, (4) watching the universe end, and (5) watching the black hole evaporate before you.

(1) Tunnel vision: As you approach the event horizon, your line of sight is warped by the bending of light into parabolas, like baseballs tossed into the air. Parabolic light makes the black hole's horizon appear to rise as your line of sight bends more and more sharply back towards the surface of the black hole. Consequently, your view of the outside world becomes an ever-shrinking tunnel that ends in a pinprick of intense light.

(2) UV obliteration: Just as _rising_ light increases in wavelength and fades in intensity, _falling_ light does the opposite. It increases in frequency and amplitude until the light your distant friend helpfully shines toward you escalates not just into the ultraviolet but into the extreme gamma range. First, it obliterates you chemically. Next, it induces nuclear fusion. But those nuclei don't last since ever-higher gammas break down your nuclei into a neutron-proton plasma. Finally, even your protons and neutrons collapse into a quark-gluon plasma. You may want to ask your friend not to bother with the helpful light!

(3) Quantum orbiting: You might think higher gravity would overcome any "off-target" aiming. Not so! Angular momentum is a stubbornly conserved quantity that gets more, not less, extreme as you approach a target. Think instead of ice skaters pulling in their arms to spin ever faster. A particle with the slightest deviation from "straight down" must, eventually, transfer all that angular momentum into the black hole's rotation. It becomes a quantum issue for individual particles: How can the particle fall in if doing so removes its angular momentum from the universe? A more likely outcome for such a particle is to enter into an event horizon momentum state akin to ones Gerard 't Hooft has proposed in recent years. Even under such extreme conditions, the most minute units of sideways-moving angular momentum must quantize. For particles, the result is akin to an enormously scaled-up, gravity-bound version of an atomic _p_ (or higher) orbital.

(4) Watching the universe end: Just as your outside friend sees your time slow down, you observe your friend's time speed up by symmetry. Near the event horizon, this gets extreme in both directions. In fact, in the split instant before hitting the event horizon, you see the end of the universe! Now, if you are a fan of paradoxes, think about that for a moment: How, precisely, does one "observe" the end of the universe if the black hole into which you are falling is, by definition, part of that universe? The counter to this — a good one — is that you, the infalling person _must_ conserve linear momentum in your frame. Thus you cannot stop at the event horizon and wait for the end of the universe. Relativity says you _must_ plow through the event horizon smoothly from your perspective. The momentum-conserving smoothness argument is valid and brings up the final point, which is…

(5) Watching the black hole evaporate before you: Assuming all your particles are headed straight down — the black-hole equivalent of atomic _s_ orbitals — you need not worry about slowing down to watch the universe end. That's because, due to Hawking radiation, even the most gigantic black evaporates at incredible speed just in front of you, doing so quickly enough not to slow you down. Your gravitational time dilation keeps increasing until it reaches a balancing point for preserving your inbound linear motion. You don't need to know how much you slowed down since it's a self-correcting loop: Slower evaporation means slower time flow for you, and faster evaporation means faster time flow. To you, it's all smooth: The black hole, no matter how big, goes _poof_ just before you pass through its event horizon, removing any chance of you observing its interior. Singularities need not apply!


Terry Bollinger CC BY 4.0
2022-10-03.22.30 EDT Mon

[abelfonseca]

if objects take longer than the age of the universe to fall into a black hole from the perspective of an outside observer, then why do black holes exist from our perspective?

[Condor]

Thanks Dr. Don, for another great, informative, and 'fun' video. I don't know how you do it, but please don't stop. Your physics videos make my week 👍.

[braddixon]

Hmmm, learned a couple things here, 1) larger black holes don't tear you apart as you enter, and 2) there is energy lost as you approach the black hole, which changes the perceived wavelength of light of the object as it nears the black hole. Great stuff, keep them coming. I'm subscribed and always enjoy your content!

[prabha]

I greatly appreciate your videos that you make and is very helpful and so I thank you for spending your valuable time for improving our knowledge Sir.

[justmyopinion]

Great lesson on black holes. I found myself saying “WOW! That is so cool!”, way too many times.

Thank you very much for your lessons.

[duggydo]

Good to have the context along with the explanation.

[tcarr]

This guy is my favorite nerd from Fermilab!!

[mohitsoni]

Spaghettification makes you look thinner, which eating Spaghetti doesn't.. 😁😜

[ThomasJr]

What this means is that the gravitational acceleration g of 9.8m/s^2 near the surface of the Earth is just simplification. The g is a function that is not constant. But for most purposes that assumption is good, as the real g is a function of the altitude.

[SatyamSharma-spnk]

Sir, can we measure the speed of gravity spread of newly developed star or planet. After which time its gravity starts attracting objects.(measure of gravity spread per unit time) .😊🙃

[lightdark]

Should I watch this? If it turns out what I saw on the show Andromeda wasn't true I don't think I could cope. 😳

[TunaFreeDolphinMeat]

The galaxies further away from us accelerating away at a greater speed could be a type of flying spaghettification indicating we are in a black hole

[sethapex]

Doesn't the person falling into the black hole see the light from the outside world get blue shifted as it falls into the black hole such that they would essentially get cooked with gamma rays before they pass the event horizon.

[Pkshah]

Hey man....you are doing a great job
Atleast for me

[funpinkgnome]

This guy's gotta be one of my favorite human beings. I love these videos.

[peterdamen]

I really like the videos of Don Linclon. Including his sometimes somewhat nerdy humor. But in this video I have to set the record straight! At the beginning of the video, around 1:20 min, Lincoln criticizes the answers seen in books and videos. Unfortunately, he is also wrong in stating that an object approaching a black hole becomes seemingly frozen in time (around 4:35 min). That is simply not true. Matter does not become suspended forever, just outside the event horizon of a black hole. As that it is not true that time comes to a standstill at the event horizon. Look e.g. at the article by Pounds et al. (An ultrafast inflow in the luminous Seyfert PG1211+143. Mon Not R Astron Soc (2018) 481, 1832-8). In it they describe that an object falls into a black hole. "We were able to follow an Earth-sized clump of matter for about a day, as it was pulled towards the black hole, accelerating to a third of the velocity of light before being swallowed up by the hole". Apparently, Lincoln has to redo his

[d_mosimann]

Thank you for part I: From an outside perspective. Looking forward to part II: From the falling object's perspective, until it's inside the Black Hole and even beyond that.

[johngrey]

If I knew this info when I was in school, I would've raised the classroom clock higher. At least a foot!