Here are some things we know (or at least think we do):
Our universe of space and time is something like 13.8 billion years old, and getting older every day.
By contrast, average human lifespan is ~70 years.
Humanity, our species, is only ~200,000 years old.
Life itself, beginning with single celled organisms, is approximately 4 billion years old.
In other words, it took over 9 billion years for life on earth to emerge, and another ~3.8 billion years for our species to evolve.
Though we have good, albeit circumstantial, evidence of the beginnings of life and the universe, we have no clear idea when—or even if—our universe and even life itself will end, how many more billions of years it will continue to exist.
The difference between billions and tens or hundreds or thousands of years is difficult for us to grasp. It's easy to foreshorten these time frames.
There are hundreds of billions of stars in our galaxy.
There are likewise estimated to be two trillion galaxies in the universe, each filled with hundreds of billions of stars, many like our own with multiple planets orbiting them.
The universe itself is thought to be some 93 billion light years in diameter.
These numbers are so vast, our minds can hardly calculate them.
Yet, somehow we are capable of making reasonably accurate estimates of the age and size of the universe and its number of heavenly bodies.
Particles are nebulous, cloud-like, that is, until they are observed.
Through our instrumentation and experimentation, we can make some reasonable observations of their probable locations or velocities.
Yet, they exist in the smallest conceivable unit of physical space, something called a Planck length. One way to visualize how small this might be is the following: Imagine "a particle or dot about 0.1 mm in size (the diameter of human hair, which is at or near the smallest the unaided human eye can see) were magnified in size to be as large as the observable universe [i.e., 93 billion light years in diameter], then inside that universe-sized 'dot', the Planck length would be roughly the size of an actual 0.1 mm dot."
The speed of light is 299,792,458 meters per second; or ~186,282 miles per second. We've managed to approximate this as well. A light year, of course, is the distance a beam of light, or a photon, would travel in a year at this rate of acceleration.
Our planet is about 25,000 miles around the equator. A photon of light could circle the earth more than 7 times in a second.
A photon will travel at this constant rate in a straight line forever until it interacts with another particle, though its path may be diverted by gravitational pull.
At absolute zero, or zero kelvins, or -273.15 degrees Celsius, or -459.67 Fahrenheit, matter reaches it foundational state.
The scale of human perspective exists in a state in-between all these phenomena: the instantaneous and the near-eternal, the very, very large and the very, very small, energy and matter, the speed of light and absolute zero.
How is it that we are privileged to have this vantage on all these phenomena? How is it that we can make some reasonable guesses about the nature of these things? This is a philosophical question.
The human scale is characterized by brevity, uncertainty, relativity, and incompleteness.
We have, of course, and have to rely on the evidence of our senses: sight, hearing, smell, touch, and taste.
But we also have extensions of many of these—prostheses, if you will—such as: mathematics and logic, atomic microscopes and particle accelerators, x-ray and infrared telescopes and arrays of radio antennas, gravitational wave observatories and electromagnetic spectroscopes, among many others.
These provide access, but they also limit us. It is important to understand these limitations.
Imagine if we were creatures who could at once perceive things that were ~93 billion light years large all the way down to the Planck length.
Imagine if we were creatures who experienced the lifespan of a galaxy the same way we humans experienced a single burst of fireworks.
Imagine if we were creatures who experienced the entire universe of space and time the way we now experience a wave on the shore, or even as a single bubble of spindrift in the foam of a breaking wave.
Imagine if we were creatures who could code a virtual computer program to run on its own in four dimensions according to certain preset logical conditions.
Or, imagine if we were creatures made up of pure, unbounded energy (or, alternatively, information) who never experienced entropy or succumbed to the dimensions of space and time, at once both greater than and somehow beneath physical reality.
Are such imaginary beings or creatures or things possible? Could they exist? Who knows?
And, if so, would it even be correct to call them beings (or creatures or things) or say that they exist?
We may never be able to say, not least because we suffer from the structural limitations of our language (and thus the human mind) which, ultimately, breaks down to following formula: THING —> HAPPEN.
I suspect the Ancient Greek philosopher/sophist Protagoras was righter than he ever could have imagined when he said: "Man is the measure of all things, of the things that are, that they are, of the things that are not, that they are not."
It is at once a statement of great hubris (or vanity) and profound humility.