suppose human race all died this very second?

what would happen to this planet?

we're talking 6.5 billion dead bodies rotting. we're talking about factories coming to a stop, planes falling out the sky, traffic chaos, movie theatres full of dead bodies. would there be massive fires from collisions and human machinery and refineries unmanaged? would animals start feeding on humans? what would eat us? rats, cats, dogs?

what would happen to our cities? i know there have been sci-fi movies about this stuff but only as a kind of backdrop for a few survivors. but suppose there were no survivors. would the greenhouse gases stop filling up the atmosphere? would animals multiply and reclaim what they've lost?

for how long would skycrapers remain standing? 5,000 yrs? 10,000 yrs?

after 50,000 yrs, if aliens visited our planet, would they have much to go on to know what we been?