There is a high probability that we are alone in the Universe. This is because, as far as we know, Earth is the only planet that supports life. And, even though there are billions of stars and planets in the Universe, the chances that another planet supports life are very low. In all of that vastness, it is highly unlikely that there is another planet like Earth with intelligent life.
First, a planet would need to be the right distance from its star. If it is too close, the planet would be too hot and all the water would evaporate. If it is too far, the planet would be too cold and all the water would freeze. Second, the planet would need to have the right amount of water. If there is too much water, the planet would be too hot. If there is not enough water, the planet would be too cold. Third, the planet would need the right kind of atmosphere. If the atmosphere is too thick, the planet would be too hot. If the atmosphere is too thin, the planet would be too cold.
There are other factors that suggest we are alone in the Universe. The vastness of the Universe makes it very unlikely that we would ever be able to find another planet like Earth. Even if there were other intelligent civilizations out there, the chances of us ever making contact with them are very very slim. We may never know for sure, but the evidence suggests that we are the only intelligent life in all of the billions of galaxies in the Universe.
We are alone in the Universe.