When did hydrogen combine with oxygen

[wolram]

This maybe a silly question but I do not know the answer.
Did hydrogen combine with oxygen to form water in geological times or did they combine before that

 

[DrDu]

If at all, it is rather that hydrogen separated from oxygen rather than combining. Water was already omnipresent when the Earth formed. However, the UV light from the sun constantly splits up water into hydrogen and oxygen. As hydrogen is lighter, more and more of it dissapears into space. Hence our Earth is slowly oxidized.

 

[256bits]

Hence our Earth is slowly oxidized

Can you explain that concept more thoroughly please..
Are you referring to a redox chemical reaction?

 

[256bits]

This maybe a silly question but I do not know the answer.
Did hydrogen combine with oxygen to form water in geological times or did they combine before that

Hardly silly.
There is still a debate of whether or not comets/asteroids delivered the water to the earth, or if it was already present. Then again, isotope comparisons between the two, ( Earth's water and that of extraterrestrial ) do not compare, suggesting that the comet theory is not viable.

Although not a verifiable site, ( I will have to see if there is one ), this comment is worthy of discussion.
Throughout its history, Earth's water has increased in volume due to biological processes. In the early seas of Earth, hydrogen sulfide would have been in great supply, which, when reacted with carbon dioxide from the atmosphere during photosynthesis in sulfide-reducing bacteria, would have produced hydrogen, sulfur, and water. Many geologists believe that the majority of Earth's water generated through this process.

http://www.wisegeek.com/where-did-the-Earth's-water-come-from.htm

 

[256bits]

Perhaps this is better.
https://www.newscientist.com/articl...ts-own-water-from-scratch-deep-in-the-mantle/

 

[DrClaude]

Perhaps this is better.
https://www.newscientist.com/articl...ts-own-water-from-scratch-deep-in-the-mantle/

The publication being referred to is:
Z. Futera et al., Formation and properties of water from quartz and hydrogen at high pressure and temperature, Earth Planet. Sci. Lett. 461 (2017) 54–60

The above numerical work follows from experimental results:
A. Shinozaki et al., Formation of SiH₄ and H₂O by the dissolution of quartz in H₂ fluid under high pressure and temperature, Am. Mineral., 99 (2014), 1265-1269

 

[wolram]

Thank you for the replies, I now have a better understanding of the subject.