How do i combine hydrogen and oxygen?

ixing hydrogen and oxygen equals water, but at room temperature and normal pressure this happens extremely slowly; an energy source, a catalyst, is needed to start the chemical reaction. However, hydrogen is extremely flammable and explodes even in the presence of a lighted match or a spark, so attempting this is not advised.

metric time was an attempt to create a standard unit of time based off of 10, but it never took off an is not included in the metric system (si)