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

  • Gravitational lensing, the bending of light by a massive object.
  • Gravitational redshift, the change in wavelength/frequency of light near a massive object.
  • Frame-dragging, which is important near rotating massive objects.

  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

  • Eternally collapsing objects
  • Magnetospheric eternally collapsing objects
  • Black stars
  • Fuzzballs
  • Dark energy stars
  • Gravastars

  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.

posted almost 8 years ago

HDE 226868‭

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