"Do you believe there is extra-terrestrial life in the universe? And if these so called 'Greys' are real then what do you think their current civilization status is? We are currently a type 0 civilization so we are far off any good space travel." - Mawderz

"This is a question with only one answer for those of us who study astronomy, cosmology, astrophysics etc.

Yes, there is no doubt in mind that there is Extra-terrestrial life in the Universe, very likely even intelligent life.

You see, there are over 50 billion galaxies in the visible Universe, however estimates of how many galaxies there are in the entire Universe go as high as 500 billion, and some people even believe infinite amounts.

However, for arguments sake, we'll say there are just the 50 billion galaxies in the universe, the one's we can see. On average, there are around 400-500 million stars per galaxy, but we'll call it a flat 500 million to keep the maths round.

So that's 500 million multiplied by 50 billion to get an estimation for how many stars there are in the Universe. This gives 2.5*10^19, or 25,000,000,000,000,000,000, that's an estimation of 25 quintillion stars, a rather unfathomable number.

Now lets move onto planets, you see it is very very hard to detect planets, because of how small they are compared to the star they are orbiting, but it is extremely likely for there to be at the very least 1 star per planet, probably more, due to the nature in which stars are formed, which I will not go into detail to.
To give you a perspective of how hard it is to detect planets, it's like getting a huge floodlight, 2x2m, standing 100m away from it with it on, and trying to see, with the naked eye, a dot the size of a pin head, which is why the only planets we have detected are by majority, gaseous giants similar to Jupiter.

So, assuming there are just one planet per star, even though there are likely to be more, like our star, we have over 25 quintillion potential planets. Now if you can tell me, that with this many potential planets, that on just another one of those planets, the blocks fall in the right place to end up with life.

Most people believe there are hundreds, if not thousands or more, other planets with developed life out there.

As for the "greys", I am skeptical, if the Universe is as vast as it is estimated, there is a probably chance that it just so happens that somewhere out there, life develops in such a way to give humanoid life, i.e the greys.

Some people believe the greys, or other aliens of this type, watch over our planet, and controlled our evolution, hence why we look so like them, but of course I am very skeptical of these theories.

But I personally don't see why there couldn't be other intelligent, developed, life out there, but as for aliens visiting Earth? I am skeptical, I would like to believe that aliens have visited Earth, but due to the vastness of the Universe, it may be unlikely that they have.

Hope this helps."

"Why dont we build a massive cannon in space and fire a rocket with people on it out into deep space? instead of firing it from earth?" - interest

"A cannon haha? I see what you mean, but because that idea is flawed. It's all well and good having this cannon in space, but we would still have to get people into space to be fired from it. This type of machine would also probably need round the clock engineers working on it, which is less than convenient.

Also, as we would have to put people in a rocket to get them to space, it would probably be more effective just to leave them in the pod they are already in, with a fuel source to start accelerating them once they are free of air resistance.

It is probably just easier to keep space travel as we do at the moment, as we have used the same source for getting people, or satellites, into space, has been the same for the last 50 years, give or take."

"How many atoms are there in our universe?" - joeisjoe5

"Now that is a question. Unfortunately, as you will probably know, an unanswerable question! A number we cannot possibly imagine!

However it might be interest for me to note the history of all the matter in our Universe!

You see, when the Big Bang happened, or as some prefer to call it nowadays, the Big Inflation, there were very almost equal amounts of Matter and Anti-Matter!

Now when matter and anti-matter come into contact, they annihilate each other, in a very very energetic "explosion"! So therefore, the very early Universe, was simply a sea of sub atomic particles, the building blocks of atoms, and there anti-counterparts, annihilating each other, producing unholy amounts of energy!

However, it is estimated that for every billion anti-matter particles, there were one more particles of matter, so one billion and one. And these one in every billion particles of matter that survived, is what makes up our Universe today!

Pretty crazy if you ask me."