Q4. How did the early earth lose its hydrogen and gain an ozone layer, according to NCERT?
UV rays from the sun broke water into hydrogen and oxygen; the lighter hydrogen escaped, and oxygen combined with ammonia and methane to form water, CO2 and other compounds; the ozone layer formed (NCERT page 111).
Q5. Besides amino acids, what did similar experiments after Miller’s produce, and what did meteorites show?
Sugars, nitrogen bases, pigments and fats; analysis of meteorites revealed similar compounds, suggesting such processes occur elsewhere in space too (NCERT page 111).
Q6. What were the conditions on the early earth, according to NCERT?
High temperature, volcanic storms and a reducing atmosphere containing CH4, NH3 and other gases (NCERT page 111).
Q7. The universe is about 13.8 billion years old and the earth about 4.5 billion. For roughly what fraction of the universe’s age has the earth existed?
4.5 ÷ 13.8 ≈ 0.33, about one-third (our arithmetic from NCERT page 111).
Q8. Why does NCERT say that looking at stars is looking into the past?
Light takes time to travel, so we see the stars as they were when their light left them; stellar distances are measured in light years (NCERT page 110). NCERT says the light started millions of years back; for the stars we see with our eyes it is years to thousands of years (see the NCERT slip on the page).