How to reconcile maximum density versus big bang baseball 'material' I have an incredibly curious 6 yr old who watches Secrets of the Universe constantly and so far I can answer most of his questions but I am struggling on one now.  When watching a show about the very first moments of the universe, there was a part that said all the matter we have in the whole universe was at one point the size of a baseball.  To have fun with the idea, we put a hand towel in a ziplock bag and vacuumed it until it got much smaller.  He asked if we kept going would it eventually have fusion.  I will leave that for another question unless someone wants to throw me a bone lol, but it got me thinking about something else.
These shows always use examples like if you could have one spoonful of this super dense baseball, it would weigh more than our galaxy, etc....
So my question is, what 'matter' can be that dense?  I tried to Google some stuff and found a saying that if you could remove the empty space from atoms, the entire human race would be the size of a sugar cube.  Now if that is anywhere near correct math then there must be some state of matter that is 10 to the zillions of times denser.  The entire mass of the human race is insignificant even compared to the mass of our planet, so what was the nature of the state of matter at this entire mass of the universe-baseball moment?  
Any insight greatly appreciated!  
 A: To be sure, the state of "matter" (I'm not even sure you could call it matter, perhaps someone could help out here) that you're referring to during the first moments of the universe is drastically different from the scenario of superdense matter that you've Googled. So, let us separate the analogies of a teaspoon of the baseball-stuff and a sugar cube of the entire human race.
Multiple online sources give an estimate of the mass of the entire human race to be somewhere between $285-350$ billion kilogrammes. You are right in stating that this is essentially insignificant compared to the mass of Earth, which Google gives to be around $5.972\times10^{24}$ killogrammes. Just for scale, that's
Earth - 5 972 000 000 000 000 000 000 000 kg
Humans - 350 000 000 000 kg
In fact, all of humanity doesn't even weigh more than Mt. Everest (~1 000 000 000 000 kg) and if you find that funny, remember that we are essentially water and that the density of rock tends to be around 3-5 times that of water. If you approximate all of humanity's mass as roughly equal to that of Mt. Everest and compress it into that sugar cube, you more or less get neutron star matter. Neutron stars are 1.5-3 times our Sun's mass (also called a solar mass) compressed into a really small sphere (much, much smaller than the moon).
You are also right that that type of matter is essentially atoms minus the empty space. This is because ~99.94% of all of an atom's mass is concentrated in the nucleus, which is about 10,000 times smaller than the size of the entire atom. There is an excellent video by Kurzgesagt on neutron stars that I do not doubt will be of interest to you and your son. 
Oh, and even if you kept going with that vacuum, you would never get to fusion. Remember, the bag is not being "sucked" smaller by the vacuum cleaner, it is being "pressed" smaller by atmospheric pressure (the air all around and above you). This pressure could never come close to the requirements needed for nuclear fusion (temperature, energy, pressure, etc.). All the best with your son's education in Physics, maybe we'll even see him on here in the future.
