The only Universe we can really measure and describe is the one we are experiencing now.
But, is that mean that there is only one Universe? A few hundred years ago, people believed that there is only one Solar system and that the Milky Way is the only galaxy. People were convinced that there are no outer worlds and that Earth is the center of the Universe. Now we know that there could be billions of planets similar to Earth. Moreover, we know that billions of other space objects exist, like stars, planets, asteroids, satellites, and galaxies. Our Milky Way is not the only galaxy in the Universe. Today, it seems crystal clears. Still, hundreds of years ago, most people had doubts that there are other galaxies in the Universe.
Sometimes I wonder, do we ever find evidence that there are billions of other universes and dimensions? We call it Multiverse.
For today, it seems like science-fiction theory. Nevertheless, no one found any evidence that other universes and dimensions could not exist. I know that if we cannot see something or experience it, for us, this thing seems not to exist.
Nevertheless, there is such thing in the cosmos a dark matter and dark energy. We do not see them. Probably we cannot even experience them. Still, shreds of hypotheses (e.g., connected with gravitation) say that such things exist. As far as I know, we can somehow measure both dark matter and energy. What do I want to stress today? I want to say that I believe that there are many things unmeasurable for us. Probably many of them will never be both measured and experienced. Still, it does not mean that this thing does not exist if we cannot see something. I hope that there will be many more groundbreaking scientific discoveries during my lifetime, thanks to which our knowledge about the Universe will only increase.