Hypothetically, if we launch a probe with a camera towards a black hole which will transmit a video signal in real-time to us at a safe distance, what will we see?
As the camera approaches the black hole, gravity will increase, and as a result, the time for a spacecraft with a camera will slow down as it approaches the black hole. You could see such an effect, for example, in the movie Interstellar.
As a result of this, an interesting effect will arise: if the camera transmits, say, 25 frames per second under normal conditions, then as we approach the black hole, we will receive fewer and fewer frames per second from the camera.
This animation of a black hole by NASA shows how gravity warps spacetime.
In other words, the signal from the camera will experience a gravitational redshift: the wavelength of the signal from the camera will increase, and the closer the camera is to the black hole, the faster the displacement will occur.
If there was an observer on the spacecraft with a camera, then from his point of view the camera would continue to shoot 25 frames per second but will receive footage slower due to the gravitational time dilation of one second. But in the frame of reference of an observer located far from the black hole, time will flow much differently.
The number of frames per second that we will receive from such a camera will first begin to decrease, and then the time interval between individual frames will increase to hours, days, years, centuries, millennia, and so on.
To fix such a signal shifting into the region of long waves, we will need specialized equipment, in addition, we will also need to solve the problem of interference created by matter falling onto the black hole. However, these are purely technical problems that can be solved with the help of specially designed receiving equipment, as well as the use of noise-immune signal coding.
The final image transmitted by the camera depends on the mass of the black hole on which it falls. If the camera falls on a black hole of stellar mass (the masses of such black holes usually vary from 5 to several tens of solar masses), then the tidal forces of the black hole will rupture the spacecraft along with the camera on approach.
This is due to the fact that the inhomogeneity of the gravitational field of such a black hole greatly increases as it approaches it. As a result, tidal forces arise inside the solid, caused by this inhomogeneity, and at some point in time, the body (in our case, this is an apparatus with a camera) will simply be torn apart into atoms.
In this case, all that we will see in the video is a black hole accretion disk consisting of a red-hot matter rotating in a circle of a black hole and a completely black ball in the middle – the event horizon.
A more interesting picture will be shown by a camera falling into a supermassive black hole. At first glance, this may seem strange, but the gravitational field of supermassive black holes is much more uniform and therefore a spacecraft with a camera has every chance of reaching the event horizon safe and sound.
As the camera falls into the black hole’s gravity well, its angle of view will begin to decrease until all the light from the universe degenerates into a small blue dot, at the moment of passing the event horizon even this point will disappear and complete darkness will come.
After the camera crosses the event horizon, it will apparently continue shooting, but the signal transmitted by it will never reach us. And it’s also unlikely to wait for the camera to cross the event horizon: it will take billions of years.
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Sources:
• Cheong, R. (2015, November 20). What happens when you throw a camera into a black hole? Retrieved November 30, 2020, from http://www.hopesandfears.com/hopes/now/question/215747-camera-black-hole
