The answer is, no! Let’s assume we only consider the observable universe (it it even bigger than that). So in 2003, astronomers pointed the Hubble telescope in a dark corner of the sky, and took the most accurate picture they were able to obtain.
In the above high definition picture, they were able to count more than 10 000 galaxies. But it covers only a small square of our sky (0.04° to be precise), which means that we should take around 23 million pictures like this one to cover the entire sky. We can reasonably assume that there are 23 million x 10 000 = 230 billion galaxies. Fair enough.
This is the Milky way by the way, our galaxy.
We know for fact that it contains between 200 and 400 billion stars like our Sun. In the entire universe, we therefore have at least 200 billion x 230 billion stars (4 600 0000 000 000 000 000 000), which means as many potential solar systems like ours! Well, conditions for life to appear are very hard to obtain.
Let’s say 1 out of 1 000 000 000 000 systems harbors life. Anyway, it still makes 460 billion populated planets. It has been proved experimentally, and on paper by Einstein’s Special Relativity that we physically can’t travel faster than light: 300 000 km/s. It would take 4.2 years to reach the closest star (Alpha Centauri) at 40 000 billion km from Earth. (With 1 chance out of 1 000 000 000 000 to find life there). At 10 000 km/s we would need 450 000 years…
On the other hand, extraterrestrial beings could reach us only by curvating spacetime (like gravity does) and traveling through a singularity like a wormhole. It requires more dimensions than the four we live in, as the string theory assumes. In fact, it needs a higher spatial dimension to fold our spacetime in, and make a tunnel shortcut.
Which means they did/will come, but we didn’t/won’t see them in our regular 4D spacetime. Maybe they are here, right now, but we can’t see them. They can only see us, from their higher spatial dimension. Who knows…
Napisala: Maria Djerdjaj