Chapter
22. Falling into a Black Hole
22.1 Introduction
AstroTutorials
true
To advance to the next page of the tutorial you need to submit every question; currently you have not finished all the questions on this page. Leaving a tutorial page without submitting all the questions results in you receiving no grade in the gradebook.
true
Author: Scott Miller, Penn State University
Editor: Grace L. Deming, University of Maryland
What would it be like to fall into a black hole?
The goals of this module: After completing this exercise, you should be able to:
- Explain what would happen to an object as it fell into a black hole.
- Explain what an outside observer would see happen to the falling object.
In this module you will explore:
- The effects of tidal stresses on an object falling into a black hole.
- The gravitational redshifting of light as it moves away from a black hole.
- The dilation of time for a falling object, as detected by an outside observer.
Why you are doing it: Black holes are strange and exotic objects which excite the imagination of science fiction lovers. But how accurate are the television and movie depictions of spaceships heading toward a black hole? Haven't you ever wondered what it would be like to fall into a black hole? In this activity, we will explore what would happen if you did.
22.2 Background
As an astronaut approached a black hole, his or her feet would be stretched more than the head due to tidal forces.
Black holes are extremely dense objects in space, so dense, in fact, that not even light can escape from their gravitational pull. The farther away you are from a black hole, though, the easier it is to escape from its pull. There is a boundary surrounding a black hole called the event horizon where, if outside of it, it is possible for objects to escape from the black hole's gravitational pull, if moving fast enough. Inside of the event horizon, nothing can escape from the black hole.
Question
22.1
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
3
Try again. As you might expect, the closer two objects are, the stronger they pull on each other, but how much stronger?
Correct. According to Newton's law of universal gravitation, gravity obeys an inverse square law. As objects move farther apart, their gravitational attraction becomes much weaker.
Incorrect. According to Newton's law of universal gravitation, gravity obeys an inverse square law. As objects move farther apart, their gravitational attraction becomes much weaker.
Summary
As an object begins to fall toward a black hole, the black hole's gravitational pull on the object becomes stronger and stronger. The gravitational pull of the black hole depends on the square of the distance of an object away from the black hole. Since objects are not points in space, but have a volume, there is a side of the object which is closer to the black hole, and a side which is farther away. Because of this, the closer side feels a stronger gravitational pull than the farther side, which leads to tidal stresses. As an object falls closer and closer to the black hole, the tidal stress becomes stronger and stronger, until it overcomes the object's own self-gravity which keeps it together, causing the object to be ultimately ripped apart.
But what if an object could withstand this tidal stress? What if an object could maintain its integrity as it fell towards a black hole? What would we, as an outside observer, see?
Just because our object falling towards a black hole won't be ripped apart by tidal stresses, doesn't mean that it won't be affected by them. Because the near side of the object feels a greater gravitational pull from the black hole than the far side, the object will be stretched in the direction towards the black hole, as the astronaut in the picture above. As the object falls closer to the black hole, the tidal forces become stronger, and the object would become stretched further. This effect has become known as spaghettification based on Stephen Hawking's description of the effect as being "stretched like spaghetti" in his book, "A Brief History of Time".
22.3 Gravitational Redshift
As light moves away from a black hole, it is gravitationally redshifted.
As we watch an object fall towards a black hole, we would notice another effect. First, consider what happens when you throw a ball up in their air. It starts with a given amount of energy, but as the Earth pulls back down on it, it loses that energy, slowing down until it ultimately stops, and then falls back down to the Earth. The more energy you give to the ball, the higher it will rise, but eventually it loses all of its energy, stops, and falls back to the Earth. If you could give the ball enough energy, it would free itself from the Earth's pull, never falling back down, but it would lose some energy in the process, moving slower than it did when you first threw it.
Now let's look at our object falling towards a black hole. If it is giving off light, that light is trying to escape from the black hole as well. If the object is outside of the event horizon, then the light can move fast enough to escape from the black hole, but as it does so it loses energy.
Question
22.2
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
3
Try again. Think about which property distinguishes a specific photon...
Correct. The speed at which all light travels is constant, but the energy of a photon is directly related to its frequency, and inversely related to its wavelength. Lower energy photons have longer wavelengths (or lower frequencies) than higher energy photons.
Incorrect. The speed at which all light travels is constant, but the energy of a photon is directly related to its frequency, and inversely related to its wavelength. Lower energy photons have longer wavelengths (or lower frequencies) than higher energy photons.
Summary
Since all forms of light travel at the speed of light in a vacuum, as the light loses energy it doesn't slow down, but instead its wavelength is shifted. The wavelength of light is inversely proportional to its energy; longer wavelength light has less energy than shorter wavelength light. Therefore, as the light emitted from the object moves away from the black hole, its wavelength becomes shifted towards longer and longer wavelengths, as shown in the figure above. We see this as a redshifting of its light. Because this is not due to the motion of the object, we do not call this a Doppler Redshift, but rather a Gravitational Redshift.
22.4 Time Dilation
There is another effect that we, as outside observers, would notice occurring with the object. According to special relativity, as objects move faster and faster, time associated with that object appears to run slower and slower. This is known as time dilation.
Albert Einstein used a thought experiment to demonstrate time dilation. Let's measure the amount of time it takes for a beam of light to travel from the floor of a train, up to a mirror on the ceiling, and back down again. In the animation below, click Play to see what an observer riding on the train would experience.
For a person standing on the train, the distance the light travels is simply straight up and down. Now, let's see what a person outside of the train would see. In the animation below, click Play to watch the beam of light from an external perspective.
Question
22.3
WNV2X+JUC3iJRzt41jZGRHHNYFVm1/ehtsJhbtW9wnl44VXJlCx6HJNMnZKinYJTKq3yxFar1yFbEMCva0XpGwjWSSx87JpWl+jU56EGdimyhn6TOkpnYKnSzhUF9fLl9CkHRbXx51wm6qysfpFEhJjqcTzwTUp625KeilxLpHhW5MEUaLGPqqo/QtSwXAhTXFC9g+yxoSOvLW1ty8ADFsV17ojSG43BgpADrhaQJ6BOfpX8ZjcN1Uj9qZ5KT+HDi58+zRR/3MzJD7sZ25VhOjpLqDuPj6v0XvRUgOr7v3o=
3
Try again. Watch the animation again and compare the lengths the light travels in each case.
Correct. For a person standing outside of the train, she will see the beam of light move upward towards the mirror, but if the train is moving, the beam of light and the mirror will have moved sideways by the time the light reaches the mirror, and moves farther sideways by the time the light reaches the floor again.
Incorrect. For a person standing outside of the train, she will see the beam of light move upward towards the mirror, but if the train is moving, the beam of light and the mirror will have moved sideways by the time the light reaches the mirror, and moves farther sideways by the time the light reaches the floor again.
Summary
According to an outside observer, the light has traveled a farther distance than observed by a person on the train. Since light travels at the same speed for both observers (the speed of light), the outside observer measures the event as having taken longer than measured by the observer on the train. In general, stationary observers will always measure the time of a moving clock to move slower than that of a stationary clock.
What does this mean for our observations of the object falling towards the black hole? As the object falls closer and closer towards the black hole, it would appear as if its time were moving slower and slower. The source of this slowing of time is gravitational time dilation.
22.5 Reaching the Event Horizon
We've talked about three main events which would occur with an object falling towards a black hole: spaghettification, gravitational redshift, and time dilation. With each of these, as the object moves closer to the event horizon, the effect becomes greater and greater. What happens as the object reaches the event horizon?
First, tidal stresses depend on the inverse cube of the distance of an object from the gravitational body. As the object falls closer to the black hole, tidal stresses increase dramatically, and the object gets pulled out longer and longer as shown in the picture above. Tidal stresses don't become infinitely strong, though, until the object is right next to the point singularity of the black hole, so while spaghettification would become more pronounced as the object approaches the event horizon, it does not become infinitely so.
Question
22.4
8LRyalvgGxVWUhcTQCfB77hSnuRGZcIZuTauxC9hAdoq6l+C2U4DdVSuaIyfeWC2AuChGTbmf2bLA62LshoKYjhkvMR4i+CwmlPd/5kvr+iHmt1RrPjThOtY93odZGrAJPZ8OPyRk63lId3J/hdzUj8KP5RFAOxGqKv3ct4PJ+XA6Wc36v3XsKvY8CsEoe3n/ucbfPNtnhY2qF83YEhvAumvu11o4bpwm8AXUvQadFtw0HxxuvkxZCy30ylGKIdThdVAZqvufzG/68XztBpj3aNk/LS/c1tWoVt/gyGJE0RO5BViiudwkUqKPmsoJAfd
3
Try again. If the energy of light is equal to zero, what is the inverse of zero? As the energy gets smaller and approaches zero, what happens to the wavelength?
Correct. If energy and wavelength are inversely related to each other, then as the energy decreases, the wavelength must increase. As the energy reaches zero, the wavelength approaches infinity.
Incorrect. If energy and wavelength are inversely related to each other, then as the energy decreases, the wavelength must increase. As the energy reaches zero, the wavelength approaches infinity.
Summary
The gravitational redshift of light given off by an object near a black hole becomes more pronounced as the object falls closer and closer to the event horizon. Since the event horizon represents the distance from a black hole at which light can just barely escape from its pull, it will take all of the light's energy to escape at this point. Light that does escape from the black hole will be infinitely redshifted, losing all of its energy yet escaping from the black hole's gravitational pull.
According to general relativity, time dilation becomes more pronounced the faster an object moves. Let's go back to the train. As the train moves faster and faster, the beam of light and the mirror will appear to move farther and farther sideways as the beam travels up and back down, causing the light to travel a farther distance. If the train could travel at the speed of light, the beam of light would take infinitely long to travel the distance. The same is true for the object falling towards the black hole. As it reaches the event horizon, the duration of its events as viewed by us, a stationary outside observer, would appear to take infinitely long. In other words, as the object approaches the event horizon, its time would slow so much that it would appear to stop, and we would never see it cross through the event horizon.
22.6 A Different Point of View
What would it be like to cross the event horizon of a black hole?
Throughout this entire activity, we've talked about what we, as outside observers, would see if we watched an object fall towards the event horizon of a black hole. But what would we observe if we were that object, falling toward the black hole? Spaghettification would still occur. As we fell toward the black hole, we would be stretched longer and longer. At what point we would be stretched so much that we were ripped apart would depend on how big we are (assuming we are in a spaceship of some sort), and how massive the black hole is. It could happen either inside or outside of the event horizon, but eventually it would happen.
But what about the other two effects?
Question
22.5
RYZrS+8fRCNXKig+rpfRh1jPXhf7gSR6A1rwaEKS7fNdwi5ilOsbyx92FWZr3CQcU8PBUIHuTjhUPP8FuKubTnp7Caz0NPsdIBxAMxC7Gc60lOYpHgeiVPymhoJRY2JpvKmy/raCSl7fQetrbVJ0I/J1BWCJYNFLLFbWxhy8rFAkCcKaua1FKT6nA3sr2QJY1hSOI3lqByLohhm4yOInRugNItWt4xCO590IOFwqMLwpa4snltujG5PDhm66VbdpKuMmR0NfQtI=
3
Try again. Think back to our discussion of each phenomenon. Who observes a gravitational redshift of light? Who observes time dilation?
Correct. As an observer on the falling object, we would observe any light given off by the object as being at the wavelength at which it was emitted. We would not detect any gravitational redshift from our perspective. Even as we reached the event horizon, we would still measure the object giving off the same wavelength of light. As for time, it would run perfectly normal for us. Time dilation is an effect observed by stationary observers when looking at moving objects. Since we would be moving along with the falling object, we would be stationary in relation to it, and therefore would not notice any dilation of time.
Incorrect. As an observer on the falling object, we would observe any light given off by the object as being at the wavelength at which it was emitted. We would not detect any gravitational redshift from our perspective. Even as we reached the event horizon, we would still measure the object giving off the same wavelength of light. As for time, it would run perfectly normal for us. Time dilation is an effect observed by stationary observers when looking at moving objects. Since we would be moving along with the falling object, we would be stationary in relation to it, and therefore would not notice any dilation of time.
Summary
What would we experience as we reached the event horizon? Assuming that we were still alive (and not ripped apart by the tidal stresses), we would not notice anything. The event horizon is not a physical barrier surrounding the black hole. It is simply a distance defined by astronomers as the point at which light can escape from the black hole's gravitational pull. As you cross over the event horizon, everything would continue to proceed as normal. There would only be one difference. Once you cross over the event horizon of a black hole, there's no turning back. No matter how fast you travel, at this point there is no escape from the black hole. What is space like inside of a black hole? While some scientists have a few theories, in reality we have no idea. Since nothing can escape from inside the event horizon of a black hole, we have no way of finding out what its like inside.
22.7 Quick Check
Indepth Activity: Falling into a Black Hole
Question
22.6
RuKH4QXs+Kt8VGjX5bVv11m0RLTVKrAKxm/LEg4Qjq3HEZf+/jmsixIsZCNasFMLeCHqTNolm1yQFiIPV77zo07TCOdRYtN6NrP4rvyyAgOpwk9ecZZG4oPBL464qVHqH2uKhJfs4nsj7m3bJe8WyMCTaLbGi3FTogXSwln9xxMiWVkK+1/NSQFuAD8sfSFUVyjhXM2ZL25MKIbbhP24kxj/xQ+ukyOcKHA8/nXcOGkZ2hVXLgLArw6+FxnzNBM1YXLfAHEgkKhs4KB49E5Vw0NRaI1QQQIj2I1J2ttjFDqdMwPLafa1kRy2jVT+Fdteor67n1KYlf1kHUXp8xfBV97sOYI2nMCJ3NSi+MGwQlkvjuRU+vQJL06nFx1nhr1vgpIJJdUBOcZcH7PGs+VmbjcMmflpHh43n5Csa6im6/cxWCmVPS7gI3YcaHFt1i5e7+IEg5DmeMFXxYjhHnxrvp6mGfMqHFV160PZb4N7hp2oTYB++6P9E3n8TMpiMCL1hdD/ALe9Mzi9pzw4ByhuMXp/138gdMQIi0wbBtmsVhvcMYfOwjjNkvVbml4MVh/w2j8Vl3/2rsjVn/SVpMXCpoOxhVAa5gPqEV1fuawMlrg+p9NDveHF7LWAnnEsWXGcKLenEQ==
Question
22.7
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
Correct. According to time dilation, it only occurs when a stationary person measures an event occurring on a moving object. Since both astronauts are stationary relative to their ipods, they will both measure the length of the song as being the same.
Incorrect. According to time dilation, it only occurs when a stationary person measures an event occurring on a moving object. Since both astronauts are stationary relative to their ipods, they will both measure the length of the song as being the same.
Question
22.8
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
Correct. According to time dilation, as the object approaches the event horizon, it will appear to take an infinitely long time to enter it. Therefore, an outside observer will never see the object enter the event horizon.
Incorrect. According to time dilation, as the object approaches the event horizon, it will appear to take an infinitely long time to enter it. Therefore, an outside observer will never see the object enter the event horizon.
Question
22.9
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
Correct. While gravitational redshifting and time dilation are phenomena detected by stationary observers outside of the influence of the black hole, spaghettification due to tidal stress would be observed by both.
Incorrect. While gravitational redshifting and time dilation are phenomena detected by stationary observers outside of the influence of the black hole, spaghettification due to tidal stress would be observed by both.
Question
22.10
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
Correct. The event horizon is not a physical barrier, but simply represents the distance from a black hole at which light can barely escape from the gravitational pull of the black hole. As an observer crossed over this region, nothing would change. The only difference is that he would now be unable to escape from the black hole, no matter what he did.
Incorrect. The event horizon is not a physical barrier, but simply represents the distance from a black hole at which light can barely escape from the gravitational pull of the black hole. As an observer crossed over this region, nothing would change. The only difference is that he would now be unable to escape from the black hole, no matter what he did.
Question
22.11
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
Correct. If light is emitted from an object near a black hole, its wavelength becomes shifted toward longer and longer wavelengths. This redshifting of light is not due to the motion of the object but by the gravitational field around the black hole. This effect is called Gravitational Redshift.
Incorrect. If light is emitted from an object near a black hole, its wavelength becomes shifted toward longer and longer wavelengths. This redshifting of light is not due to the motion of the object but by the gravitational field around the black hole. This effect is called Gravitational Redshift.
Question
22.12
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
Correct. As an object gets closer to a black hole, the object gets more stretched out by the tidal forces. This effect has become known as spaghettification based on Stephen Hawking's description of the effect as being "stretched like spaghetti" in his book, A Brief History of Time.
Incorrect. As an object gets closer to a black hole, the object gets more stretched out by the tidal forces. This effect has become known as spaghettification based on Stephen Hawking's description of the effect as being "stretched like spaghetti" in his book, A Brief History of Time.
Question
22.13
l74Lru0aoPMLkP1H8urMKzUS1rq/7LeHd8y2hKN52cBs2Z9Fj+6NpkXLn62be/GSnlUmt3WEjfeAW70pF9Dyu68B5cq6F5E/xZW/Cj+CPcvM4f6cp9nzO3iSIJEWM26vbNZiQ4R03Ik5ZGlAcjC25iIdSqVOe7Ksat2MTjzEZ2PzHxE0N9mX+FbCzgM7tJHSvOycOY7pFddW+op6FoZ1TT6girWlSOuPEfl0DBKV04Jnd3LoO4Oz3ImcTmxd3fJxkfaAP/DLaIJGm1qfRoHdDNpohrmufkT+4yTgI20uMeiONLW5mTsujzt07PWf22WttiYZLsFf+qGYX9A/FbWbs66Bs2E91ycpxwdONV064hVUdA1J6chuRmQvXdxkqGLl3CcRz1t/RMSqGa/waTlEyOwwo56CCodbY7fNp9ZglbMKJq/2AL0iS0froovNG9F07hrhRynQYwZpgOBwW90Uk3go1qJY3fZb/HDiEdveEdKE5dVe
Correct. There is a boundary surrounding a black hole called the event horizon where, if outside of it, it is possible for objects to escape from the black hole's gravitational pull, if moving fast enough. Inside of the event horizon, nothing can escape from the black hole.
Incorrect. There is a boundary surrounding a black hole called the event horizon where, if outside of it, it is possible for objects to escape from the black hole's gravitational pull, if moving fast enough. Inside of the event horizon, nothing can escape from the black hole.
Question
22.14
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
Correct. According to special relativity, as objects move faster and faster, time associated with that object appears to run slower and slower. The same effect happens when an object falls closer and closer toward the black hole because it would appear as if its time were moving slower and slower.
Incorrect. According to special relativity, as objects move faster and faster, time associated with that object appears to run slower and slower. The same effect happens when an object falls closer and closer toward the black hole because it would appear as if its time were moving slower and slower.
Question
22.15
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
Correct. Black holes are extremely dense objects in space, so dense, in fact, that not even light can escape from their gravitational pull.
Incorrect. Black holes are extremely dense objects in space, so dense, in fact, that not even light can escape from their gravitational pull.
