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The Question

(Submitted July 10, 2009)

This is a simple queston. everything is made in stars from mostly hydrogen and helium becuase of gravity. but then where did the hydrogen come from? Please do not say the big bang did it that is what the teacher says and then that everything comes from nothing. that is silly. only nothing comes from nothing. and I am here and I'm not nothing

The Answer

We hate to tell you this, but your teacher is pretty close. All the hydrogen in the Universe was created in the Big Bang. But we wouldn't say that it came from "nothing." Right after the Big Bang (which wasn't really an explosion, but rather the start of the expansion of the Universe), the Universe was in a very hot, dense state. In fact, it was entirely dominated by radiation (no matter!). Now, you may have heard that matter can be converted into energy, but the reverse is also true.

Energy can be converted into matter. In the early Universe (we're talking the very first second!), this is exactly what happened. The radiation was converted into the first protons (hydrogen). A few minutes later, there was a short period where some of the hydrogen fused into helium and a teensy bit of lithium. The very first stars formed from this material. The fusion that takes place in their own cores gave us all the heavier elements that we see today.

Now, where the radiation that was converted into the hydrogen came from and what came "before" the Big Bang, these are questions astronomers don't know the answer to right now and may never know.

For more check out these links:
http://en.wikipedia.org/wiki/Timeline_of_the_Big_Bang
http://www.astro.ucla.edu/~wright/cosmology_faq.html

Amy C. Fredericks and Michael Loewenstein
for Ask an Astrophysicist

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