The conversation
Could a human go into a black hole to study it?
A person falling into a black hole and being stretched as he approaches the black hole’s horizon. Leo Rodriguez and Shanshan Rodriguez, CC BY-ND Curious Kids is a series for children of all ages. If you have a question that you would like an expert to answer, send it to [email protected]. Could a human go into a black hole to study it? – Pulkeet, 12, Bahadurgarh, Haryana, India To solve the mysteries of black holes, a human must simply venture into one. However, there is a very complicated problem: a human being can only do this if the respective black hole is supermassive and isolated, and if the person entering the black hole does not expect to report the findings to anyone in the entire universe. We are both physicists who study black holes, although at a very safe distance. Black holes are among the most abundant astrophysical objects in our universe. These intriguing objects seem to be an essential ingredient in the evolution of the universe, from the Big Bang to the present day. They probably had an impact on the formation of human life in our own galaxy. Two types of black holes The universe is filled with a vast zoo of different types of black holes. They can vary in size and be electrically charged, just as electrons or protons are in atoms. Some black holes rotate. There are two types of black holes relevant to our discussion. The first does not rotate, it is electrically neutral – that is, it has no positive or negative charge – and it has the mass of our sun. The second type is a supermassive black hole, with a mass of millions to even billions of times greater than that of our sun. In addition to the difference in mass between these two types of black holes, what also differentiates them is the distance from their center to their “event horizon” – a measure called radial distance. The event horizon of a black hole is the point of no return. Anything beyond this point will be swallowed up by the black hole and disappear forever from our known universe. The distance from the center of mass of a black hole to where the pull of gravity is too strong to overcome is called the event horizon. Leo and Shanshan, CC BY-ND On the event horizon, the black hole’s gravity is so powerful that no amount of mechanical force can overcome or neutralize it. Even light, the fastest moving thing in our universe, cannot escape – hence the term “black hole”. The radial size of the event horizon depends on the mass of the respective black hole and is the key for a person to survive by falling into one. For a black hole with a mass of our Sun (a solar mass), the event horizon will have a radius of just under 2 miles. The supermassive black hole at the center of our galaxy, the Milky Way, in contrast, has a mass of approximately 4 million solar masses and an event horizon with a radius of 7.3 million miles or 17 solar rays. So someone who falls into a stellar-sized black hole will get much, much closer to the center of the black hole before passing the event horizon, instead of falling into a supermassive black hole. This implies, due to the proximity of the center of the black hole, that the attraction of the black hole to a person will be different by a factor of 1,000 billion times between the head and the feet, depending on which is driving the free fall. In other words, if the person is falling with their feet first, as they approach the event horizon of a stellar black hole, the gravitational pull on their feet will be exponentially greater compared to the pull of the black hole in their head. The person would experience spaghetti and most likely would not survive being stretched into a long, thin shape similar to pasta. As a person approaches the event horizon of a sun-sized black hole, the vast difference in the gravitational attraction between the individual’s head and toes causes the person to stretch into a very long noodle, hence the term ‘spaghetti’. Leo and Shanshan Rodriguez, CC BY-ND Now, a person falling into a supermassive black hole would reach the event horizon much further from the central source of gravitational attraction, which means that the difference in gravitational attraction between the head and the feet is almost zero. Thus, the person would pass through the event horizon unaffected, would not be stretched out on a long thin noodle, would survive and float painlessly beyond the horizon of the black hole. A person falling into a supermassive black hole would probably survive. Leo and Shanshan Rodriguez, CC BY-ND Other considerations Most black holes that we observe in the universe are surrounded by very hot disks of material, composed mainly of gas and dust or other objects such as stars and planets that came very close to the horizon and fell in the black hole. These disks are called accretion disks and are very hot and turbulent. They are certainly not hospitable and would make the trip to the black hole extremely dangerous. To get into one safely, you would need to find a supermassive black hole that is completely isolated and not feeding on surrounding material, gas and or even stars. Now, if a person found an isolated supermassive black hole suitable for scientific study and decided to venture into it, everything that was observed or measured inside the black hole would be confined to the black hole’s event horizon. Bearing in mind that nothing can escape the gravitational pull beyond the event horizon, the falling person would not be able to send any information about their discoveries beyond that horizon. His journey and discoveries would be lost to the rest of the universe forever. But they would enjoy the adventure as long as they survived … maybe … Hello, curious children! Do you have any questions you would like an expert to answer? Ask an adult to send your question to [email protected]. Tell us your name, age and city where you live. And as curiosity has no age limit – adults, also tell us what you are asking yourself. We will not be able to answer all questions, but we will do our best. This article was republished from The Conversation, a nonprofit news site dedicated to sharing ideas from academic experts. It was written by: Leo Rodriguez, Grinnell College and Shanshan Rodriguez, Grinnell College. Read more: Supermassive black hole in the center of our galaxy may have a friendThe scariest things in the universe are black holes – and here are 3 reasons why the authors don’t work, consult, hold no shares or receive funding from any company or organizations that would benefit from this article and have not disclosed relevant affiliations other than their academic appointment.