Concept explainers
Surviving the Plunge. The tidal forces near a black hole with a mass similar to that of a star would tear a person apart before that person could fall through the event horizon. Black hole researchers have pointed out that a fanciful “black hole life preserver" could help counteract those tidal forces. The life preserver would need to have a mass similar to that of an asteroid and would need to be shaped like a flattened hoop and placed around the person’s waist. In what direction would the gravitational force from the hoop pull on the person's head? In what direction would it pull on the person's feet? Based on your answers, explain in general terms how the gravitational forces from the “life preserver" would help to counteract the black hole’s tidal forces.
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Essential Cosmic Perspective
- A black hole is an object with mass, but no spatial extent. It truly is a particle. A black hole may form from a dead star. Such a black hole has a mass several times the mass of the Sun. Imagine a black hole whose mass is ten times the mass of the Sun. a. Would you expect the period of an object orbiting the black hole with a semimajor axis of 1 AU to have a period greater than, less than, or equal to 1 yr? Explain your reasoning. b. Use Equation 7.6 to calculate this period.arrow_forwardAs an object falls into a black hole, tidal forces increase. Will these tidal forces always tear the object apart as it approaches the Schwarzschild radius? How does the mass of the black hole and size of the object affect your answer?arrow_forwardA stellar black hole may form when a massive star dies. The mass of the star collapses down to a single point. Imagine an astronaut orbiting a black hole having eight times the mass of the Sun. Assume the orbit is circular. a. Find the speed of the astronaut if his orbital radius is r = 1 AU. b. Find his speed if his orbital radius is r = 11.8 km. c. CHECK and THINK: Compare your answers to the speed of light in a vacuum. What would the astronauts orbital speed be if his orbital radius were smaller than 11.8 km?arrow_forward
- What would be the Schwarzschild radius, in light years, if our Milky Way galaxy of 100 billion stars collapsed into a black hole? Compare this to our distance from the center, about 13,000 light years.arrow_forwardAs a person approaches the Schwarzschild radius fo a black hole, outside observers see all the processes of that person (their clocks, their heart rate, etc.) slowing down, and coming to a halst as they reach the Schwarzschild radius. (The person falling into the black hole sees their own processes unaffected.) But the speed of light is the same everywhere for all observers. What does this say about space as you approach the black hole?arrow_forwardWhat is the Schwarzschild radius for the black hole at the center of our galaxy if it has the mass of 4 million solar masses?arrow_forward
- A student becomes so excited by the whole idea of black holes that he decides to jump into one. It has a mass 10 times the mass of our Sun. What is the trip like for him? What is it like for the rest of the class, watching from afar?arrow_forwardThe escape velocity at the event horizon of a black hole is 3×108 m/s, i.e., the velocity of light. What is the mass of the black hole if the distance from its centre to the event horizon is 18km? a) 12.15 x 10-30 kg b) 12.15 x 1030 kg c) Infinity d) Cannot be determinedarrow_forward1. Let’s say we have a black hole with a mass 10 times that of the Sun (the Sun’s mass is 2 x 1030kg so the mass of the black hole is then 2 x1031 kg) Using the definitions for G and c what Schwarzschild radius of this black hole be? g=6.67 x 10-11 m3 kg-1 s-2 c=3 x 108 m s-1arrow_forward
- What is the Schwarzschild radius (in km) of a 6Msun black hole? What fraction of the Earth's radius is this? What percent of the speed of light (2.998 x 108 m/s) is the escape velocity at the Schwarzschild radius? Part 1 of 3 The Schwarzschild radius of a black hole is given by: 2GM Rs = c2 so for the given mass, 2G(6)(Msun) Rs c2 where M. Sun = 1.99 x 1030 kg. Then convert this into kilometers using 1 km = 1,000 m. Rs kmarrow_forwardSuppose you drop a clock toward a black hole. As you look at the clock from a high orbit, what will you notice? Time on the clock will run faster as it approaches the black hole, and light from the clock A. will be increasingly blueshifted. B. The clock will fall toward the black hole at a steady rate, so that you'll see it plunge through the event horizon within just a few minutes. C. The clock will fall faster and faster, reaching the speed of light as it crosses the event horizon. D. Time on the clock will run slower as it approaches the black hole, and light from the clock will be increasingly redshifted.arrow_forwardNow look at the two images labeled "At a distance of 2.5M" and "At a distance of 2.1M". These show what happens as you move towards the black hole, looking away from it. What happens to your field of view of everything outside the black hole?arrow_forward
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