Suppose we detect a stellar black hole passing near the Solar system, and we have technology and time to send a manned mission to study it.

Are there any experiments or observations that would help us learn more, maybe test some of our theories or the whole mission is pointless?

I would like to use this as a setting, if it makes any sense.

Envisioned Story

My "hero" is a physicist suffering from some kind of incurable disease, that won't prevent him from doing his mission. He knows it's a one way trip and that's why he volunteered to be send there. My plan was to do some observations, experiments with probes, and finally enter the black hole. I know it's a cliche but it feels cool.

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    $\begingroup$ Only if you don't like the man. $\endgroup$
    – aslum
    Commented Nov 29, 2016 at 14:16
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    $\begingroup$ ya know, this is the perfect solution for: prison overcrowding, nuclear waste....etc. $\endgroup$ Commented Nov 30, 2016 at 6:35
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    $\begingroup$ Do black holes pass i.e do they move/change location? I think they are static. $\endgroup$
    – Sp0T
    Commented Nov 30, 2016 at 11:22
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    $\begingroup$ @Sp0T They're affected by gravity just like everything else $\endgroup$
    – Pyritie
    Commented Nov 30, 2016 at 13:32
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    $\begingroup$ @Sp0T: in our universe, there is no such thing as “static”. If we can move in relation to the back hole, it also can move in relation to us. $\endgroup$
    – Holger
    Commented Dec 2, 2016 at 14:52

11 Answers 11


What could be learned?

There are so many things you could study by looking at a black hole. There are lots of open or partially unsolved problems that surround them:

  • Does Hawking radiation exist? While it has been predicted theoretically, direct evidence is lacking - well, nonexistent. Stellar-mass black holes aren't the best targets - primordial black holes are better - but you never know. Extreme up-close measurements could yield results.
  • How do astrophysical jets form from accretion disks? Jets are present around many objects, black holes included (if there is an accretion disk present), but the precise mechanism for their formation is unknown. The prevailing hypothesis is the Blandford–Znajek process, but this has yet to be confirmed.
  • Is general relativity accurate? All the evidence is in its favor, but more experiments never hurt. Many tests of general relativity could be repeated near the black hole, where relativistic effects are extremely strong. The tests could include

    We could also test alternative theories of gravity, and maybe rule some of them out.

  • Do black holes even exist? While there is quite a lot of evidence for black holes or black-hole-like objects, alternatives or modifications have been proposed, including

    Many of these ideas are wild, and some cannot be tested by observations of black holes (or "black-hole-like objects").

  • Is information lost inside black holes? The black hole information paradox - a notable problem in general relativity, quantum mechanics, and physics in general - asks whether or not "information" about physical states is lost inside a black hole. This has implications regarding string theory, among other areas.
  • Do naked singularities exist? The cosmic censorship hypothesis states that they don't; observing a rotating (Kerr) black hole could give us more information about this. Gravastars also provide a solution to the paradox; if black holes are actually gravastars, then the paradox could be solved. Whether or not the two are observationally different is a harder question.

Why send humans?

Now, all of this could be done by computers, not humans. So why send humans, who need that pesky air, food, water, waste disposal, life support systems, life insurance, etc.? Good question. Here are my answers:

  • It's good publicity. Would you rather be the first nation/company to send a probe to a black hole, or the first nation/company to send brave, daring human explorers out into the great beyond, champions of our species - to boldly go where no man has gone before? Admit it; the second sounds a lot better. Yes, the astronauts will have to deal with a lot of risk. But there are going to be plenty of people willing to do it.
  • Communication is hard, and humans can make on-the-spot decisions. Light travels at a finite speed, and on astronomical scales, this is pesky. It takes 8 minutes for light to travel to Earth from the Sun (one astronomical unit, or AU). The Solar System is a lot larger - even Neptune is 30 AU away from the Sun. This black hole is likely farther, especially if it's going to cause no disruption to the system (unlikely, unless it's really far away).

    Therefore, you can either pre-program the itinerary beforehand, or send people who can make on-the-spot decisions. Mission Control isn't going to be there to hand-hold the ship's computers through this thing, and humans do have a certain knack for solving problems when things don't go as planned.

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    $\begingroup$ I don't see how you could test the second last point with a probe. If you send something into a black hole it will be hard to determine anything about its physical state after it passes the event horizon. $\endgroup$
    – kingledion
    Commented Nov 29, 2016 at 1:25
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    $\begingroup$ @ohwilleke Where did you get the figure of 3000 light-years? The question assumes a black hole passes close to the Solar System. $\endgroup$
    – HDE 226868
    Commented Nov 29, 2016 at 2:00
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    $\begingroup$ @ohwilleke I'm aware, but the black hole in the question is far, far closer. $\endgroup$
    – HDE 226868
    Commented Nov 29, 2016 at 2:04
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    $\begingroup$ I disagree that sending people to cruel and unusual graves is "good publicity" $\endgroup$
    – Zxyrra
    Commented Nov 29, 2016 at 2:39
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    $\begingroup$ @Zxyrra As to whether it is good publicity or not depends on how you "spin" it. ^^ Besides, it is basically his last wish, and what more appropriate grave for an astrophysicist than a significant stellar object? $\endgroup$
    – nijineko
    Commented Nov 29, 2016 at 20:17

There is no point in sending a manned mission!

As @HDE22686 noted, there are many interesting phenomena associated with black holes. Given the opportunity to study one up close, it is likely that missions will be sent. However, describing all the cool phenomena associated with black holes only means they will be studied - not that humans will be there to see them

So why on Earth would you send a human to a black hole?

  • Human error influences data: This is a once-in-a species (potentially) chance. There is no point sending humans capable of error on board this probe when a considerable amount of money is at stake.
  • Black holes are deadly: Any miscalculation in the trajectory of the probe may risk ending human lives, millions of miles away from home - is that really worth it? Additionally, exotic radiation is associated with black holes. It's safest not to play with that.
  • We can send other organisms instead: If the point is seeing the effects black holes have on living tissue, why not send rats? Or dogs? Or chimpanzees? Or a sample of human flesh kept alive by life support?
  • Multiple unmanned probes decrease chances of inaccuracy: While machines are capable of failure - see the recently crashed Mars rover which was brought down by a glitch - many agencies capable of sending probes will do so, meaning data collected will generally reflect the truth. Compare this to multiple probes with humans on board.
  • Missions are flybys: When we send spacecraft out of the solar system to observe distant objects, we never intend to get them back - and even if we wanted to, it's extremely expensive! The first few generations of Mars colonists will be stuck on Mars forever because we aren't willing to pay for ships capable of escaping Mars after landing. With that in mind, why would we send people out of the Solar System and then attempt to get them back?
  • Machines are competent and won't need to make major decisions: While humans can make on-the-spot decisions, a probe with basic sensors, locomotion, and apparatus is capable of steering itself. No situation will arise where only a human could decide what to do.

In conclusion, we'll be killing people - who could mess up the missions - in strange and potentially cruel ways, millions of miles away from home, with no chance of retrieval - when machines can do the job even better. Missions? Yes! People? No.

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    $\begingroup$ He has removed Black holes are deadly as a reason to not send. $\endgroup$
    – Joshua
    Commented Nov 29, 2016 at 17:59
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    $\begingroup$ Increasing knowledge carries risk, and sometimes sacrifice. The lives of a few, any a many few, would be worth the potential knowledge gain. Those that went should be volunteers, and automated test can still run and not be messed up by the humans. And no, machines cannot think better than humans -- at least, not yet. $\endgroup$ Commented Nov 29, 2016 at 19:06
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    $\begingroup$ I disagree on the human error argument. Why send an unthinking machine up when you can send a thinking human and an unthinking machine? As someone who programs the unthinking machines, I can tell you how valuable having a thinking human nearby can be! $\endgroup$
    – Cort Ammon
    Commented Nov 29, 2016 at 20:41
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    $\begingroup$ This is a bad argument. Name a spacecraft that has failed in space due to error of the human pilots. Now let me tell you about Galileo's main antenna and Mars Climate Orbiter and many more. Lets also talk about how error prone humans saved the day on Mir, and Apollo 13. $\endgroup$
    – kingledion
    Commented Nov 29, 2016 at 21:09
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    $\begingroup$ @Zxyrra Our "autonomous" devices are very good at what they do, as long as everything happens exactly as they expect it to happen. They are not very good at recovering from surprises. This is why our "autonomous" rovers on Mars are constantly being sent updates from the humans on Earth. We still have not made a machine which can deal with the unknown quite as well as a human mind. And I guarantee you that there will be unknowns in such an extreme environment. $\endgroup$
    – Cort Ammon
    Commented Nov 29, 2016 at 21:57

For science!

At present we have two main theories of physics:

  • General relativity, which is about very heavy things and gravity.
  • Quantum mechanics, which is about very small things.

We have not been able to fit these two together. One of the reasons for this is that we have not been able do experiments that test both at once. Objects that are small enough to have quantum effects are not noticeably affected by gravity. At least not strongly enough that we can distinguish between different theories of gravity.

Our other theories (eg. electromagnetism) can be fit with one or the other, but not both at once.

Black holes changes things. Here gravity is very strong and even electrons will feel the pull.

If we would be able to bring along both a neutrino source and a neutrino detector, we would learn much about these mysterious particles. However, at current or near-future tech levels neutrino detectors are very massive and not something you can move off-Earth.

Even without that I am sure there are numerous experiments we could do with a humble electron ray that will be very useful.

The main experiment I see done is sending a laser or a ray of electrons in very close to the event horizon, and putting a detector where it comes out.

Useful results would be angle of deflection and time taken for the journey. Maybe also how spread out the beam has become.

If the hole is rotating, sending beams both with and against the rotation will be interesting.

Why humans?

This is about science, which means we won't know in advance what experiments we want to perform. Results of the one experiment will suggest new physics theories. These will suggest new experiments to perform.

A machine cannot do this. (Unless you have powerful AI) If there are no humans on the spot, the results will have to be sent to Earth and new commands sent back. This will take too much time and the black hole will move away before we are done.

I suggest a crew consisting of a mixture of astronauts and physicists. Both will need to have a good understanding of the other side, but in the end they are different in their goals. The astronauts will want to keep everybody alive and return home in one piece. The physicists will want to perform more experiments. More! MORE!!

Other answers have suggested sending several unmanned probes instead of a manned one. I suggest a manned ship carrying many unmanned probes. The ship stays prudently far away from the radiation, the probes go closer, not close enough for tidal effects to destroy them, but definitely into hard radiation areas.

Parting gift.

The time comes when the hole moves away and we have to go home to Earth. Leave something behind for aliens to discover, maybe something like the Pioneer Plaques and Voyager Golden Discs.

The hole will be a scientist magnet from every civilization it passes nearby and a good meeting spot.

Maybe we will find an alien artifact already there...


Don't send humans!

There are two basic reasons to send humans to space:

1) To cope with the unexpected. When your mission goes off the rails it's much more likely to succeed if you have a very flexible system on board: a human. Think of Apollo 11, coming down into the rock garden. The tech of the time would have crashed the rocket, even modern tech would be hard pressed to land it safely. A human pilot was capable of analyzing the problem and dealing with it, thus saving the mission.

2) When there is an analysis problem that can't reasonably be handled by tech. Apollo era tech couldn't do a reasonable job of gathering moon rocks. If we wanted to bring home samples other than whatever happened to be right under the scoop we had to send humans. (And note that the landing problem in #1 is also an example of this.)

Now, apply these standards to a black hole mission:

1) The unexpected, sure. It's always useful to send a human. However, that means an awful lot of life support equipment, you can send multiple unmanned missions for the price of one manned one.

2) Jobs that need a human. What jobs? There are no samples to go pick up or the like, it's going to be an extremely lethal environment outside the hull. What can the humans do??? Basically nothing!

Also, consider that the most interesting observations will be made as low as possible:

1) Delta-v requirements mean that you can get lower if you can burn all your fuel on going down and not save any for coming home.

2) The deeper you go the more dangerous the environment becomes. If you can get close I would expect lost probes as there will be lots of fast-moving debris.

Note: If the black hole is far enough out you might send a manned mission as a mothership. A lagtime of minutes or hours could be of considerable value over a lag of months from Earth.

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    $\begingroup$ Plus one from me for the manned mothership. It makes more sense to send multiple vehicles and/or probes to investigate the environment around a black hole and any of its properties. $\endgroup$
    – a4android
    Commented Nov 29, 2016 at 7:36
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    $\begingroup$ Apollo 11 is actually a good example for another reason, which is the computer problems late during the landing process. Those pesky 1201 and 1202 alarms, in a fully automated probe, might well have been enough all on their own to give an automated mission serious trouble, possibly leading to a mission failure; but the astronauts were able to look out the windows, verify that the controls still worked, and continue the landing largely unhindered. And let's not even discuss the oxygen tank explosion and near total loss of electrical power on Apollo 13. $\endgroup$
    – user
    Commented Nov 29, 2016 at 12:30
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    $\begingroup$ Having a mothership with humans means sending humans. $\endgroup$ Commented Nov 29, 2016 at 19:08
  • $\begingroup$ @EthanFurman But not to actually study the black hole, that would be done with unmanned probes. $\endgroup$ Commented Dec 1, 2016 at 22:38
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    $\begingroup$ The question is "Is it worth sending a manned mission to a black-hole" -- if humans go at all then it's a manned mission. The only way it would not be a manned mission is if humans already had an inhabited base/colony/etc. in the area. $\endgroup$ Commented Dec 2, 2016 at 20:42

The expense of sending a manned mission vs. many unmanned probes is going to make the latter very enticing. Certainly humans can adapt to situations better, but technology has gotten to the point that most of the situations they could adapt to are unlikely enough to occur that you'd make up for those occurrences by the redundancy of the probes.

The other argument for sending people may be to explore/check out something so totally unexpected that we'd have no way of accounting for it in the probe's programming. But - and this may just be the cynic in me - I think that's extremely unlikely. In a far enough future that this is feasible at all (though granted, if we were OK with the probe taking 10000 years to make it, and another 3000 to get the data, we could do it with today's technology!) tech is (hopefully) going to be so cheap and small that it'll be easy enough to make the probes just collect all the data they can. We think there might be objects orbiting the black hole, right? So a couple dozen of those probes will be set to divert course and orbit those instead, and collect data from them. I'm going to assume that they all have advanced physics processing units and would be able to calculate those orbits on the fly. And still some of them might crash (or just veer off into the void), but again, you can send a dozen probes for the cost of one manned mission.

I could potentially see live humans as ambassadors in the event that extraterrestrial intelligence is met, but the cynic in me doubly doubts that we'll ever find extraterrestrial life, let alone intelligent life. (It believes such exists - the universe is too vast not to - but it's also too vast to feasibly encounter any.) The probes collecting all that data, petabytes upon petabytes of it, will see any evidence for life that might be out there. They won't recognize it, of course, but the human scientists on earth 15000 years later (after receiving a mysterious signal from space that they decode to find that they can decode it perfectly to ancient English, and after consulting historians who kept the records of ancient, quaint technology are able to realize that a forgotten civilization of a bygone era sent it) might glean some evidence that there could be some kind of potential for the conditions of life on one of those bodies. But anyway, the probes aren't really there for that. They're gathering all the data they can because it was cheap at the time, but mostly they were looking at the black hole. Some of that information could provide insights to the current civilization, if they can translate it from a language that died thousands of years ago. But then again, 15000 years into the future of this already future point they may have built a miniature black hole and replicated most of the experiments anyway.

Honestly, with the time lag, I'm not sure I see the use of even sending unmanned missions. If I were to even do that it'd just be a probe that has "Kilroy was here" spray-painted on it, just for giggles.

Sending a manned mission that distance - no matter how dangerous a black hole is - is a death sentence. (Even if they could come back, everyone and everything they've ever known will have been dead for ages.) That is not a problem for the hero in your story, though, and is in fact kind of a selling point.

I have a simple proposition for why they'd send a manned mission - he wants to go. "I am going to die anyway, but I'd be the only human in all of human history to see a black hole up close." Sounds like motivation enough for me. In my view, he's not able to convince any government's space agency to let him do that, but a private aerospace firm finds the earnestness in his mission and undertakes (...pun intended) the project. He isn't actually necessary to gather or interpret the data, but he's able to make sense of it when his craft reports it to him. He gets to make all those conclusions and realize that he's the first person in history to not only see a black hole up close, but also finally understand Hawking radiation/information loss/general relativity. He passes away to a peaceful death, as the camera zooms out revealing the cartoon of the fellow with the big nose peeking over the wall, spray-painted onto his ship.


Send Humans!

Why? Because of archaeology...

As others have stated, computers can handle the mission, running a bunch of experiments and sending us back the results. Those automated experiments are, by definition, limited to studying the expected characteristics of the black hole. They can test for minute variances in established theories and provide detailed measurements of the black hole's physical characteristics.

But automated experiments cannot study the unexpected. That black hole may have a solar system of its own, spinning around it in slowly decreasing orbits. The planets of that solar system will vary in origin, having been stolen from different solar systems which the black hole passed through. Studying those planets and their surrounding dust clouds, is our opportunity to sample matter from farther away than we could ever travel.

And some of those adopted worlds may even have once harbored intelligent life.

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    $\begingroup$ I think the idea is that the black hole will approach close enough that radio communication is possible, so we can send commands to a probe to get it to take photos of interesting things. This will have maybe several hours round-trip time, but that's probably ok. If we can receive data from the probe, we can send signals strong enough for it to receive. $\endgroup$ Commented Nov 30, 2016 at 9:01

There's a few pitfalls to trying to study a black hole up close

  1. Not much is coming out to study. Mostly black holes emit x-rays. No matter, no light, no nothing.
  2. Once, say, a probe goes in, it's not coming back out. Nor is it likely going to be able to send data back past the event horizon.
  3. Time dilation. The closer things get to the black hole, the slower they appear in real time. So let's say you sent a team to the black hole. They would return thousands or millions of years later. So whomever sent them would be long gone by the time they got back.
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    $\begingroup$ #2: It can't possibly send any data, actually. The event horizon distorts geometry so that no direction is outward. $\endgroup$
    – Devsman
    Commented Nov 29, 2016 at 20:35
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    $\begingroup$ Well.......we won't know for 100% sure until we get there and toss something in now will we? Long range measurements and data are cool and all.....but sometimes you need to poke things, just to make sure. $\endgroup$ Commented Nov 30, 2016 at 6:39
  • $\begingroup$ Fair. We don't know for sure anything about them. And that's the reason for the expedition in the first place. $\endgroup$
    – Devsman
    Commented Nov 30, 2016 at 16:14
  • $\begingroup$ "Millions years later" oh noes it's Interstellar physics again! In the boring reality you spend one hour just 10 meters apart from a typical Schwarzschild radius of 30 km and the Earth will see this dilated to... wait for it... 55 hours. The calculation is easy enough. $\endgroup$
    – kubanczyk
    Commented Dec 2, 2016 at 10:12

My favorite scifi author Greg Egan wrote a short story about just this. It's available free online if you're curious: The Planck Dive.

Quick TLDR: It's set in a very farflung transhuman society, and they do it out of pure scientific curiosity by forking their personalities.

As others have said, there's not really any reason to send a person in on a one way trip except for the experience of it. As you say, a sort of elegant way for a scientifically minded person to die.


How to find it?

Black holes are by definition invisible the only way to find one is to look around to see stars being blocked out by them.

How to get data?

To get data from a black hole you would have to study the effects on what it does to the surrounding area and not the black hole itself.

Sizes of black holes:

A "small" black hole is an instant death due to spaghettification of the human and the probe.

A supermassive black hole's estimated inside view:

A large black hole's estimated view from the inside.

A large black hole is a slow death because the event horizon spans much further out where the gravity is still "survivable". This would probably be the most amazing way to die because you would see the universe slowly fading away. On earth maybe 100+ years might pass because of time dilation while for you only 10 minutes might have passed.

Event horizon:

It's very simple: You pass it and there is no way to get you or your data out of it. A black hole by is by definition black because it sucks in everything. X-Rays, radio frequency waves, entire stars and also light. This means that once you're in you'll have to play cards with yourself until you and the shuttle disappear from existence.

Time dilation:

A black hole is so heavy that time itself behaves differently. This is because we dont merely live in space or in time but in spacetime. Spacetime can stretch depending on how "heavy" something is. For example, every 60 years our satellites need to add 1 second to their own clock because on earth time goes a tiny bit slower. This is exactly the same near a black hole as on earth except that it is magnified so much that once you pass the event horizon someone flying outside it would see you falling forever.


Spaghettification happens when gravity on the close end of an object is higher than the further end. (On earth this would be your feet.) Because a black hole is much more powerful than earth it will stretch you from the closest end to the furthest until you are basically one long string of human.

Gravitational Lensing

A black hole's gravitational lens
A black hole is so heavy that it will warp the space around it like a magnifying glass.

Pro's of a human

  • Amazing view.
  • Time travel (only future).

Cons of a human

  • Bodily harm due to gravity, spaghettification etc.
  • Can accidently mess up the data.

Bonus points

  • Stand near a supermassive black hole to travel into the future (still outside event horizon but close enough to experience the effects)
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    $\begingroup$ *A black hole sometimes emits gamma radiation/x-rays so you might be able to get your data out through that. $\endgroup$ Commented Nov 30, 2016 at 8:56
  • $\begingroup$ @JoostBlock That radiation is actually emitted by infalling matter before it reaches the event horizon. $\endgroup$
    – Michael
    Commented Dec 1, 2016 at 4:39

There's no point sending someone into a black hole in and of itself, because once they're in they have no way of sending any findings back.

However, sending someone near a black hole could allow them to study the various features mentioned in other answers.

For the purposes of your story, the mission could be one that goes near a black hole to study it, but with no way to prevent the eventual crossing of the event horizon. That part wouldn't be the actual intent of the mission, but an unavoidable end to a mission focused on what could be done prior to that.


As someone with less of a scientific background as many of the contributors on this question, my gut reaction is that part of the case for humans exploring black holes can be made simply by considering human nature and it's role in history.

We are, by nature, adventurous creatures who inevitably grow used to our surroundings and seek to expand our horizons. The fact that we are curious, and want to know more about our surroundings (be they terrestrial or extraterrestrial) suggests to me that, while perhaps millions of years down the road, we will inevitably attempt to explore these phenomena ourselves anyway.

Some of the most empowering, inspiring and audacious ventures undertaken by mankind have been marked by certain death/injury/loss, even by those embarking upon them. The promise of our species is that, despite these factors we will always want to explore further.

If there are individuals willing and wanting to take that kind of leap, why not allow them to do so, even if only to entertain our nature.

(Philosophical-ish response conjectured from an assumption of economic, technological and legal viability of the project)


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