For tens of thousands of years, humanity barely had an impact on our planet and our environment. With only a few million of us across the world, even the largest fires, wars and waste produced in cities could do no more than poison a tiny portion of our world for a very short amount of time. But as our numbers and our technological capabilities have grown, so has our ability to damage and destroy our biosphere. With more than 7 billion of us now, managing our environment has never been more difficult, or more important. Now that we鈥檙e a spacefaring civilization, couldn鈥檛 we send our most dangerous, long-term pollutants 鈥� nuclear by-products, hazardous waste non-biodegradable plastics, etc. 鈥� into the Sun? That鈥檚 what Roger Carlson wants to know:
I鈥檝e argued for years with people that sending radioactive waste or space junk into the Sun would be hugely expensive and just not feasible. In my layman鈥檚 understanding of orbital mechanics, I know we would have to accelerate it out of Earth orbit, and then slow it down in order to have it 鈥渇all into the Sun鈥� […] I know it can be done because we鈥檝e sent probes to Venus, but I just can鈥檛 visualize it. Can you help?
First off, it absolutely is physically possible. But the question of whether we can is not the same as the question of whether we should. Let鈥檚 start by going over what it takes to make such an endeavor possible.
The reason we don鈥檛 fall off the Earth, or simply find ourselves ejected into space, is because of the Earth鈥檚 gravitational pull on us at our distance from the Earth鈥檚 center. In particular, there鈥檚 a certain amount of energy keeping us bound to our world (gravitational potential energy), and there are two important milestone speeds that we can calculate for where we are: the stable circular orbit speed for our distance from Earth鈥檚 center, which would keep us orbiting Earth without ever touching the ground, and the escape velocity at our location, which would enable us to escape Earth鈥檚 gravitational pull completely, and head out into interplanetary space. For Earth, we鈥檇 have to move at about 7.9 km/s (17,700 mph) to attain orbit and at about 11.2 km/s (25,000 mph) to escape from Earth鈥檚 gravity. By comparison, our planet only rotates at about 0.47 km/s (1,000 mph) at the equator, so we鈥檙e in no danger of escaping.
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