The four dimensions of spacetime can be hard to get your head around.

So forget about your head for now and let's try to get our minds around it.

I've already proposed that we might want to think of our minds as existing outside of time and space, more as parts of a web-work of thought, of ideas, a network of related instances of existence.

I've also observed that ideas about spacetime in the cosmic sense are not commonly a big part of our personal mental web-work. Most of us are happy to leave those thoughts to people like Einstein, and others who may think of themselves as professional cosmologists.

But this doesn't mean that cosmology has no relevance to our existence. In fact we may be inclined to take it as a given that our particular personal universe is contained in that big one. We may be more or less trusting those cosmologists to be on their game and have the right of things.

That's where it could get dicey.

There is good evidence that many professional cosmologists are humbled by the sheer magnitude of their field of study. They know perfectly well that there is more going on out there than they can personally encompass. But the contingencies of life have a way of persuading most of them to not let such emotions sway their professionally proclaimed opinions. People do not like to be publicly humbled in that way.

Here's what's going on.

There are two types of scientists, those who investigate the way things are, and those who try to make sense of the findings. Scientists are fond of proclaiming that every theory devised to explain observations, no matter how seemingly successful, remains open to being tested by new observations. But a scientist who has based a career on expounding the excellence of a widely accepted theory will not easily be swayed by new observations that appear to contradict it.

Once upon a time, any shepherd on a hill guarding a flock by night could gaze at the stars above and try to understand them. In those days it was easy to suppose that the fixed stars were somehow fastened to the inside of a celestial sphere.

It is only very recently that such star-gazing has come to require sophisticated technical equipment. So it is has only very recently been revealed that space has depth, and history.

The success of modern cosmology is based on a miracle. That miracle is the discovery that the universe is expanding. The old shepherd couldn't have known this. Most of us still can't know it directly. The knowledge depends on some rather recent realizations. 

One is that light has a speed limit. This can be shown experimentally.

The other is that we aren't particularly special. This is more philosophical. It derives from the realization that every star in the sky is a sun much like our own, many much bigger. So it is no longer believable that our world, or even our sun, is at the center of creation.

Instead, we might want to think that the universe is an infinite expanse. But if it was wouldn't light as bright as the sun be arriving equally from every direction? 

It turns out that light actually is arriving pretty much equally from every direction. But the farther away it appears to be coming from, the lower on the spectrum it is. The best explanation for this is that with the universe expanding, light waves get stretched as they travel. And the longer they travel the more they are stretched, into what astronomers detect as longer wavelengths.

The farthest source of light astronomers can detect is stretched all the way down into the microwave band.

And this is the miracle. Once starlight is old enough to be stretched below the red band, we can't see it any more. The old sky is dark to us. Because the universe is expanding.

Because of this so-called red shift in the light waves, we can tell how long ago they were emitted. Because our astronomical instruments can see this red shift, our astronomers can read the history of the universe in the images they extract from the light waves their instruments detect. Layer by layer, they can look back in time. Spacetime is like a reel of movie film that our astronomers have learned how to watch.

Using radio telescopes, astronomers have scanned the whole sky for radio microwaves. They call it the microwave background. A map displaying these waves shows that this background is quite uniform, with only very small variations. This is explained be saying that the universe was very small when these waves were emitted, small enough that every part could affect every other part, so they all tended to become similar. 

But mapping the whole sky that way requires a lot of data gathering. A lot of fine detail has to be omitted. To learn what those details are like, astronomers focus on small areas. This allows them to gather much better data about what they are looking at. Which they can turn into new frames for the movie.

The latest prequel they are watching this way comes from the new James Webb space telescope. And it turns out to be full of surprises. It seems to be telling our oldest astronomers some things they find very hard to believe. 

The new James Webb prequel has already delivered a lot of new data. It will take a while to sort it all out. And chances are that job will fall to many of the youngest, newest astronomers. When they are done, they will be able to tell us a clearer story of a young new universe.

When they do, we will all get a chance to find out how hard it really is to get our minds around that bit of early spacetime.