We will never visit all of the Universe

Just like we can not control time or travel at Light Speed

Absence of Evidence is not Evidence of Absence

If we are alone in the Universe, it would be a shamefull waste of space

To Quote Carl Sagan

I wish I had a $ for every time this question has been asked.

The simple answers is we simply don't know.

However in the words of the late great Carl Sagan:

“The universe is a pretty big place. If it's just us, seems like an awful waste of space.”

Personally in my opinion the Universe is absolutely teeming with life in differing stages of evolution from tiny Amoeba just thinking about crawling out of the Primordial Soup as we once did to those with intelligence and technology far, far greater than we mere humans.

I cannot believe that we have, or are being visited by life from another world, either from our Galaxy, the Milky Way or elsewhere in the Universe.

For us to find a planet, or moon, with life is like finding the proverbial needle in a trillion haystacks and the same applies to any other beings.

Added to this they would need the technology to be able to traverse 100s or 1000s of light years to reach us and if they have found us and do have the technology and they do decide to come here we had better pray that they are benevolent and not malevolent because if they are malevolent they will undoubtedly have the technology and firepower to crush us like we crush an ant.

No one knows any of these answers, speculation

No we're not alone, but we haven't been visited. Here we go.

There are a very large number of sun-like stars in this galaxy, most of which have planets. There are also a very large number of galaxies in the Universe. Life started on this planet almost as soon as it could, and substances found in deep space can form the building blocks of life like us. Therefore the chances of there being no life other than life here are tiny. It's practically certain that there is life elsewhere.

However, complex life might be very rare. Multicellular organisms only evolved about 800 million years ago, so over the majority of this planet's history life was simple, single-celled and microscopic. It's easily possible that this planet is a freak occurrence because it was stable for long enough for life to evolve into more complex forms and the length of time it took before complex life developed suggests that the probability of it happening is low, perhaps very low. Therefore it could well be that almost all planets with life actually just have things like bacteria living on them.

We almost certainly haven't been visited. If we had been, the beings who came here would not have been able to clear all the microorganisms from it and there would be traces of unrelated genetic code. This is not present, therefore no life anything like us has ever come here. All known life on this planet is related. The only thing which could have happened is for the first life to arrive here to have come from somewhere else, which some people do believe.

Are we alone

Most likely we are not alone. But we are yet to see any evidence of other life forms.

The best piece of evidence (the only piece) is that we exist.

So it aught to possible for life to occur elsewhere.

Have we been visited.

Probably not.

There is no evidence at all to suggest we have.

eg no derelict spaceship anywhere. And certainly no spaceship currently orbiting the Earth.

The problem with being visited is distance

It would take hundreds even thousands of years to travel from the nearer stars.

Plus we have not yet found a single earth-like planet within 50 light years - and travel time beyond that exceeds 10,000 years

Most likely not and almost certainly not. But, no one on this earth knows or sure.

1) Most likely not.

2) How would ET even know that we even exist? Let alone have the means, or even the will to travel here.

For all we currently know, we could be the most intelligent lifeforms in the neighborhood, if not the galaxy.

Are we alone in the Universe? My opinion = No . The Universes is huge, there has to be some form of life out there somewhere.

Has ET visited Earth? No. Why? Distance and the fact that the speed of light can not be exceeded.

Considering the vastness of the universe I think it's almost certain that we are not alone.

But if life exists elsewhere, it would have to be at least dozens of light years away. Meaning it would be impossible for us to know about them, to communicate with them, let alone visit. Even at the speed of light it would take a lifetime, or centuries, or millennia to get there.

If it's possible to 'fold space' or go through a wormhole or travel at many times the speed of light, we could not even imagine how it would be done. That's not to say we'll never figure it out. I mean, try explaining a microprocessor to someone from the 10th century. But it will take us centuries or longer.

If some alien civilization is visiting us, they have to have figured it out. If so, they are far advanced from our level of science and technology. If they're that far advanced, we probably don't want to meet them. More technological civilizations tend to enslave less-technological ones.

Not alone in the universe. The probability that any extraterrestrial species has visited the earth is very close to zero, but we can never know for sure.