The coolest things about black holes IMO, is that time becomes "heavier" as you approach them. In this regard, I believe that black holes protect us in a simila

The coolest things about black holes IMO, is that time becomes "heavier" as you approach them. In this regard, I believe that black holes protect us in a similar fashion that Jupiter does. Jupiter catches a lot of flak for us - remember the comets that bombarded it years back? What if Jupiter wasn't there and those hit something closer to us, such as Mars? If those comets hit a smaller body that was closer to us the toll on human existence could have been complete. It's a moot point, I know, because if Jupiter didn't exist neither would humans. Back to my point, let's imagine two scenarios: * a massive body flies past the protective system of a black hole, but does not enter that system and so is not subject to serious changes in spacetime * a massive body flies directly into the system of a black hole, and it's destination is a specific planet I will explain how that target planet planet will be protected by the black hole: In the first example, the massive body flies past the black hole very rapidly. From the perspective of the target planet it was likely too rapid to ever hope to observe, because time moves faster where that object passed. Before I move on to the second example I have an important point to make - while the distance that the intruding object needs to travel to reach its destination remains the same as it was when they were outside of the influence of the black hole's system (from the perspective of the target planet the intruding object could have travelled that distance in the blink of an eye when outside of the area of influence), the intruding object can no longer travel that distance in a blink of an eye from the perspective of the target planet once it enters the black hole's system - travel become relatively much slower. This is the primary protective measure that black holes provide us - more time. That's interesting to think about right? Is the intruding object actually moving faster outside of the influencing zone? I would argue that yes, it is, because time flows differently. To visualize this, imagine two cars driving 60mph side by side - and then imagine that for one of those cars, the road also begins to travel forward, quickly propelling the car ahead of the other. While the wheels on the car may not have been spinning faster, make no doubt, it was travelling faster - even though to oberservers who were also on the moving road the car would only appear to be going 60mph. And so how does "slowing down time for intruding objects" protect us? Well, nothing lasts forever (that we know of... maybe there's a cosmic drain somewhere that should be considered a constant, but we're not aware of that right now). The rigors of space travel and time will wear away at the intruding object more and more as it approaches the target planet which lies much closer to the black hole. There's a good chance that the intruding object will not survive to meet its target. Black holes are definitely scary, but if you think about it they might just be our friends.