by In 1974 Science Fiction Author Larry Niven wrote a murder mystery with an interesting starting point: could you kill a man with a small black hole?
I will not spoil the story, although I am willing to bet that most people would claim that the answer is clear yes. Intense gravity, tidal forces and the horizon of the event would certainly lead to a messy end.
But it turns out that the scientific answer is a bit more interesting.
On the one hand it is clear that a black hole could kill you big enough. On the other hand, a black hole with the mass of a single hydrogen atom is clearly too small to notice.
The real question is the critical mass. On what minimal size would a black hole become fatal? That is the focus of a new article about the Arxiv.
The study starts with primordial black holes. These are theoretical bodies that have formed at the earliest moments of the universe and would be much smaller than black holes with stellar mass.
Everywhere from atomicated to a mass several times that of the earth. Although astronomers have never found very black holes, observations exclude different mass reaches. For example, every primordial black hole smaller than 1012 KG would have already evaporated thanks to Hawking radiation.
Everything bigger than 1020 KG would be gravitators in the milky way. Because we have not detected these lens effects, they must at least be extremely rare. If they exist at all.
Some theoretical models claim that primordial black holes can be the source of dark matter. If that is the case, observation limits limit their masses to 1013 – 1019 KG range, which is comparable to the mass range for asteroids.
That is why the study focuses on this reach and looks at two effects: tidal forces and shock waves.
Tides forces occur because the closer you get to a mass, the stronger his gravity. This means that a black hole exercises a difference in strength on you when it gets close. So the question is whether this strength difference is strong enough to tear meat.
Asteroid-mass black holes are less than a micrometer left, so even the tidal forces would cover a small area. If someone has gone through your belly or one of your limbs, there might be some local damage, but nothing fatal. It would be similar to a needle that goes through you.
But if the black hole went through your head, it would be a different story. Tides forces can tear brain cells apart, which would be much more serious. Because brain cells are delicate, even a strength difference of 10 – 100 nanonewtons can kill you. But that would take a black hole at the highest end of our mass range.
Shock waves would be much more dangerous. In this case, if a black hole entered your body, it would create a density wave that would wrinkle through you. These shock waves would physically damage cells and convey heat energy that would cause further damage. To create a shock wave of energy similar to that of a 22-caliber ball, the black hole would only need a mass of 1.4 x 1014 KG, which is well within the range of possible original black holes.
So yes, you could kill an original black hole.
Although that creates a great story, it would never happen in real life. Even if asteroid-mass-primordial black holes exist, the number of them in comparison with the vastness of the space means that the chance that someone will happen to someone in their lives is less than one in 10 trillion.
This article was originally published by Universe Today. Read the original article.
