On the one hand, not very. The universe is massive. A single light year is 5.8 trillion miles long. The closest solar system to our own is 4 light years away (~23 trillion miles). The observable universe—everything we can see from Earth—has a diameter of about 93,000,000,000 light years (~5.5×1023 miles).
The human mind isn’t equipped to comprehend numbers this large. They’re confusingly huge. They dwarf us.
But the vast majority of the universe is a vacuum where the density of atoms is less than one per cubic meter. Most of those atoms are either hydrogen or helium. From a basic physical perspective, concentrations of matter as dense and heterogeneous as humans are exceedingly rare.
Then there’s what we do. Again, strictly from a physical perspective, we’re unusual. Most of space is about 2.7 degrees kelvin (-455 degrees fahrenheit). Nothing is known to be colder than about 1 degree kelvin, save a few special laboratories on Earth, where matter has been cooled to one-millionth a degree of absolute zero.
In David Deutsch’s words, “It may well be that the interiors of refrigerators constructed by physicists are by far the coldest and darkest places in the universe.”
How special are we (and by extension, Earth1)? Given space and time, inconsequentially small. Perhaps, also, incomparably rare.