Atom

[Matheous-2]

How did scientists determine that the very first atom did not form until 300,000 years after the 'Big Bang'?

[Count-A-Strong]

Because the universe was too hot for the nuclei to attract electrons until it was 300,000 years old. Look up 'cosmic microwave background'

[jake-the-peg]

That's pretty much it

If you "heat" an atom it will start to lose it's electrons and form an ionised gas called a plasma.

We know how big the Universe is and how hot it is Cosmic microwave Background mentioned above.

Run the expansion of the Universe back and that energy is compressed inro a smaller and smaller space and you reach a temperature about 300,000 years or so after where it is too hot for atoms to be stable

[Matheous-2]

Thank you for a good simple explanation - Otherwise I would have been easily lost!

[Brisayshi]

What is the universe expanding into?

[jake-the-peg]

Not that gets complex Brisayshi because our Universe isn't necessarilly just the 4 dimensions that we experience.

There are a set of equations called the Einstein Field equations that describe the shape of the Universe and how it is expanding.

These have a number of possible solutions many involving several dimensions.

One particularly interesting possibility is that if you could shoot off in one direction you'd get back to where you started - a bit like the Asteroids game if you remember that only in 3 dimensions.

In two dimensions for that behaviour you need a 3 dimensional sphere like the Earth.

In three dimensions you need a 4 dimensional torus (or doughnut shape).

It's very difficult to imagine higher dimensions if you are willing to risk a headache you might just manage a 4D shape

However that doesn't stop maths being able to handle it.

If you want to know the distance between two points in 2D you just use pythagorus

x²+y²=distance² (easy)

3D it's just the same x²+y²+z²=distance²

Lets work out the distance between 2 points in 6 dimensions

a²+b²+c²+d²+e²+f²=distance²

You're now doing multi-dimensional mathematics - take a bow!

[flobadob]

The universe is expanding into the universe.

[JonnyBoy12]

Not sure about all this, but we all know what the most interesting website in the Universe is. AnswerBank, of course!

[jezter]

what is the universe expanding into? thats a damn fine question and one makes my mind twitch. The universe isnt - and stop me if you reckon different- isnt actually expanding, its stretching. so the question actually is 'whats it stretching into'? Seeings as wecant detect anything beyond the universe we are a bit stuck. I like the stretching into another dimension concept - a framework of dimensions being a 'mathamatically possible way of stretching' as opposed to a space into which it stretches. As one chap said once the universe is like i massive equation, and the answer is 42.