The second most abundant element in the solar system is
A) silicon. B) helium. C) oxygen. D) hydrogen. E) carbon.
Question 2
How do we know the expansion of the universe is accelerating?
A) We're really not that sure the expansion is accelerating; it's all just a theory.
B) The rotation curves of galaxies indicate the universe is speeding up.
C) White dwarf supernova in distant galaxies are fainter than they would be if the expansion were not accelerating.
D) Redshifts of distant galaxies are increasing with time, so when we repeat the measurements, the redshifts are larger.
E) We see more of the universe every night, as the observable universe grows in size.
Circulatory System
respiratory system
Ivanpah Solar Electric Generating System
Metals reacting with oxidized oxygen
The two skills of the element Evaluation
Female Reproductive System "الجهاز التناسلي للأنثى"