Black Holes

Jillian's Guide to Black Holes: Forming - Types - Outside - Inside - Finding - References - Websites

Braking hard in the attempt to prolong what little time is left

Ooops! Not the best choice! Not like it matters, but now you'll be crushed by the acceleration of your rocket and the tidal forces of the black hole. Briefly, tidal force is what happens when your feet are accelerating faster than your head --- you get stretched! Normally, we deal with gravitational fields weak enough that this doesn't happen on a small scale (small meaning the size of humans and rockets). It does happen on the scale of the Earth in response to the gravity of the Moon. That's why it's called 'tidal,' as in 'pertaining to tides.' The gravitational attraction of the Moon on the Earth's water deforms the water into an oval so that the water bulges out from the rock in two places: one at the side that is closest to the Moon, and one on the side that is furthest from the Moon. As the different parts of the Earth pass through this water bulge, they experience higher water, or high tide.

Next to a black hole the tidal force on something the size of a human or a rocket is no longer weak at all. That deformation is happening to you and your rocket. It gets worse as as you fall further. In fact the effect is so strong that, eventually, your body will be stretched like an image on silly putty until it breaks. Since you chose to brake by firing your engines at full speed, you not only experience this uncomfortable fatal tidal force but also experience the crushing force of the accelerating your rockets are attempting to provide (just like when a car suddenly accelerates and you get pushed into the seat).

As if this isn't bad enough, there is one more relativistic effect of falling past the horizon that I have yet to mention: the blue sheet. I explain it in depth in the section about the insides of black holes, but I'll also give a brief description here. Recall how I told you that light redshifts due to gravity? Well, the opposite happens inside the event horizon --- the light blueshifts. It's just like redshifting except it's in the opposite direction. Redshifting decreases the frequency of a light ray, blueshifting increases it. Inside the event horizon, a light ray blueshifts until it becomes what scientists call a gamma ray, the most high-energy form of light there is. Gamma rays are much more powerful than ultra-violet light, which most folks consider nasty because it raises the chances of getting cancer due to its high energy. Imagine what gamma rays would do to ya!

Heh, so, not only are you crushed by the acceleration of your rocket, and stretched by the tidal forces, you are also irradiated by gamma rays! It's a good thing that the time you have left is only about the same time it would take a light ray to cross 2Rs. While trying very hard not to think about the pain, you suddenly wonder --- wait a minute, that "blue sheet" of gamma rays irradiating you came from another universe!


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