cause they just do
because there is no erosion on the moon because it does not rain
The footprints will stay on the moon because there is no weather or atmosphere on the moon! That means that if there is no weather there will be no wind to carry it away or sand to top over the footprints!
No atmosphere So no rain or wind to remove them A moonquake might lessen them
In 7,000 years
Well it probably depends on the space boots are heavy, but about millions of years.
Styrofoam cups last in the landfill for hundreds of years. Paper cups break down much faster. Paper would only last for a month.
nonbiodegradable waste can last for hundreds even thousands of years.
Until something disturbs it, like a future meteor impact, or a future moon landing. The footprints left by the astronauts may last millions of years.
There were hundreds of things that were invented within the last ten years. A common invention is the IPod. IPhone's are another common invention.
You might mean on the moon. There is no wind or rain to erode the footprint on the moon, that's why it can last up to billions of years.
I expect that the figure you provide is wild speculation on someone's part, but footprints would most likely be destroyed either by an asteroid or comet striking the moon or a moonquake.