#Opposite of helium verification

Similar to Earthly raindrops, they pick up speed as they fall. You can think of them as acting like raindrops falling towards the cloud's center. The atoms in an interstellar cloud are so far apart that they rarely encounter each other during the initial stages of collapse.

In this case, we are in the realm of the ultra-tenuous rather than the ultra-compressed. (See Plate 5 for more information on star-forming clouds.) And as always when discussing the stars, the first question is: how will the clouds behave as they are compressed by gravity? However, 10% of a galaxy is still a lot of gas, enough to make about 30 billion Suns, so there is no lack of newborn stars for us to observe. The Milky Way galaxy consists of perhaps 10% gas and 90% stars at this point. Most of the original hydrogen and helium generated by the Big Bang has long ago collapsed into stars.

#Opposite of helium verification

This essentially proves that the Big Bang could not have produced any elements in quantity other than hydrogen and helium, and it also provides powerful verification for the Big Bang itself. The observed abundances of hydrogen and helium isotopes 2 in interstellar clouds have been carefully compared to calculations of which isotopes should have been created in the few hours following the Big Bang, and the agreement is very impressive. Recent precision work using cosmic microwaves places the Big Bang at 13.7 billion years ago. However, it was so descriptive that it stuck and became the proud name for a whole set of cosmological theories based on the idea that all the mass and energy in the Universe originally exploded out of a quantum fluctuation 10 30 times smaller than a proton. The term 'Big Bang' was originally coined as a term of derision by British astronomer Fred Hoyle, who was not an avid believer in apocalyptic cosmic explosions. The hydrogen and helium are remnants of the Big Bang the 1% of 'dirt' comes from the stars themselves and we will discuss this interesting bit of self-enrichment later. The gas in the spiral arm of the Milky Way galaxy where the Earth is located is composed of about 74% hydrogen, 25% helium, and 1% everything else, thus this is approximately the composition of the Sun and also of most newborn stars in our neighborhood. Interstellar 'clouds' would make a very, very good vacuum on Earth but the space around them would make an even better vacuum, so clouds they are. Stars are formed when enormous clouds of gas (light-years 1 in diameter) collapse under their own gravity.