What will happen if all the crude oil over in the world

Conventionally reservoired crude oil resources comprise all crude oil that is technically producible from reservoirs through a well bore using any primary, secondary, improved, enhanced, or tertiary method. Not included are liquids from mined deposits (tar sands; oil shales) or created liquids (gas-to-liquids; coal oil). Earth's endowment of conventionally reservoired crude oil is a large but finite volume. Production from it may well peak within this century. All or very nearly all of Earth's prolific petroleum basins are believed identified and most are partially to near-fully explored. All or nearly all of the largest oil fields in them have already been discovered and are being produced. Production is indeed clearly past its peak in some of the most prolific basins.
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Coal, Natural Gas, and all types of solar energy are options that should keep our civilization from reverting to the "dark ages".
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I hope this is helpful.

The oil reserves of the entire world will last us a decent amount of time. By decent, I mean production will decline around 2035, but we will still have oil for at least a few decades afterwards. And even when oil is gone, we still have coal.

One of the most researched fields these days is energy. We will find replacements for oil; hydrogen, solar, wind, nuclear, biofuel, etc... New York City is powered mostly by hydroelectric and nuclear these days (that says a lot, in my opinion). Did you think hybrid cars were just for show? If you want to push carts around when oil is gone, by all means.

There will probably be some solar-hydrogen hybrid car of some sort... I have confidence that the world will not return to ancient times simply because our knowledge will never die away.

I heard somewhere we only have about 40yrs left until we run out of oil. Other means will have to be found, or yes, we will return to ancient times.

Exactly what is your question junior?

Ever heard of a little thing called the "bicycle"?