if we were all to vanish overnight, how long would it take for all traces of humanity to disappear?

Answer 1

"Traces" of humanity would remain for several billion years, until some event eventually destroyed the planet. Even then our deep space probes may exist for much longer as dead peieces of human technology floating in space.

There are traces of living animals (fossils) that are half a billion years old, and "traces" of life from more simple organisms that are up to 3-4 billion years old.

Humans make all sorts of things that are quite long lasting, many of our metal, glass and ceramic items will last as long as the rocks. For example a major freeway may still exist in "patches" for tens of millions of years since it is essentally rock. Traces and bits that could be identified as "cement" or other hard building materieals may be preserved much longer, especially if they get burried and unburried much later.

It may take some effort looking but some traces of mankind in deep space may exist until the end of time when the stars all collapse back into some giant black hole 20 billion years from now depending on when that happens.

Answer 2

The answer lies in plate tectonics. Speed up time and the land masses of the Earth are no more than a boiling cauldron, even the highest mountain on Earth, eroding by just 1mm per year, will be gone in just 9,000,000 years. All orbiting man-made artifacts will quite quickly fall into the boiling cauldron, those that are wending their way into the nether regions of the Universe are so small and insignificant that there is zero chance of them ever being found by anyone or thing. Most proof of our existence will decay quite rapidly in Cosmic terms, like the builders of the incredible, massive megalithic stone monuments placed around the world by the last intelligent species that owned the Earth before us, all that will be left when Homo Sapiens shuffles off this mortal coil will belie the technological heights we reach. Most materials decay into other unrecognizable forms quite rapidly, it is only materials such as stone that last significantly longer. As for our tenure , I don t give us more than 500,000 years and that s generous given where we are right now, and we ve already squandered 200,000 of them. So, to answer the question, ‘for all traces to disappear’, the tectonic plates move at an average speed of 4.5 cm per year, moving in both directions from the creation point. The circumference of the Earth is 40,057Km, so one complete ‘boiling cauldron’ cycle would take: 20,028 [half the circumference of the Earth in Kms] x 100,000 [cms in 1 Km] / 4.5 [Tectonic plate speed, cms per year] = 445 million years, [max, probably a lot less in reality]. There have been life forms on Earth for 3.5 billion years.

Answer 3

I would say the answer is in your question... overnight.
Anyway, a 12.0 scale earthquake that jostles the whole planet for three minutes followed by tsunamis in all major oceans would ensure a swift depature for mankind.
On December 26, 2004, Indonesia etc lost more than 250,000 people in a matter of minutes; if the scale was higher and global, it would not take long to take out 7 billion.
Cheers.

Answer 4

they wouldnt...
if everyone was gone overnight there would be no one left to hide the traces!

only if what does hide the traces is natural phenomena like earthquakes and stuff.. that would take forever!

Answer 5

About a billion years: you said traces

Answer 6

8,245 years 254 days 14 hours 24 minutes 14.4859485 seconds