The Relativity of Information

…or how fast is that comet really going?

Comet 3I/Atlas Trajectory — Wikimedia Commons

I am no astrophysicist, as you will soon see, and I normally try to conceal my ignorance as best that I can. But a nagging family of related questions has been brought to my attention by the 3I/Atlas comet hurtling through space. How fast is everything really moving?

We all know that speed is the rate at which an object covers distance. Here on earth, a driver going more than 65 miles per hour will be watching for blinking lights in the mirror. No problem. That is speed over ground.

But wait. How fast is the surface of earth rotating? It depends upon latitude, but approximately 1,037 miles per hour at the equator (I looked it up). No problem. I get that our speed over ground can be deducted from that figure if we are heading west toward the sunset and added if we are traveling eastward away from it. I’ve witnessed how rapidly the earth turns when flying fast in a jet and still unable to outpace the nightfall.

But think again. The earth is also orbiting the sun at 67,100 miles per hour, so they say. Therefore, our actual speed is the sum of this rate of motion around the sun, plus or minus the rotational speed during the day or night, adjusted for our speed over ground, depending on if we are heading east or west (I’ve seen the math, and it all makes sense).

Still, this is nowhere close to a measure of our total speed through space. The entire solar system is also orbiting the center of our galaxy at a rate of 447,000 miles per hour, rumor has it, then in comes this comet named 3I/Atlas at 130,000 miles per hour. It is one of the fastest ever observed and only the 3rd to have originated beyond our solar system.

Now we have all these different kinds of objects whirling around and are measuring their velocities relative to one another. But it seems like there is another factor to consider, the rate of expansion of the universe. Surely, we have lost touch with the comprehensible, as miles are no longer an adequate measure of distance and we must now talk in light years.

I remember once being told that light travels at 186,000 miles per second, so much faster than the objects in space we have so far discussed. A light-year, then, is the distance light travels in a year (186,000 miles X 31,536,000 seconds = too many zeroes to note). The thing is, the whole universe is expanding from the original ‘Big Bang’ at a rate they have resorted to calling the Hubble constant.

Would you like to know what that is? Approximately 67 kilometers per second per megaparsec (oh, a megaparsec is 3.26 million light-years, by the way)! The exact speed of the Hubble constant is somewhat debatable, as recent observations by the James Webb telescope indicate an average up to 73 km/s/Mpc. Nevertheless, the universe is expanding at a colossal rate that makes the relative speeds of objects within our own galaxy exceedingly sedate, by comparison.

Now here comes this 3I/Atlas comet, from who knows where, catching and flying through our solar system very rapidly. Shouldn’t its speed through the void also account for the Hubble constant and be measured in megaparsecs (which sounds just a little bit like warp speed to me)?

Well, this was my intuitive way of thinking about it until I was discretely corrected. It turns out that the Hubble constant only applies to vast intergalactic distances. Essentially, the further away an object is, the faster it is receding. Within the close confines of our own galaxy, about 100,000 light years across, this inflation rate is not really a factor (wish this were true in economics).

While the 3I/Atlas comet is very interesting, and this investigation into velocities endlessly arresting, I end up humbly admitting the limits to my knowledge of physics or cosmology and discovering the depth of my own naiveté. This has always been true in most every field of inquiry I attempt to pursue, always learning from other specialists with greater expertise. Just when I become confident at some level of understanding, a novel enlightenment always bursts forth.

I think the information habitat to which we are all now accustomed promotes a false cognitive bias that inflates subjective judgement, just like the Hubble constant. It's as though the further distant we are from a truth, the more we are inclined to believe our personal opinion. To put it another way, the relative speed at which curiosity is satisfied is inversely correlated to reality. Too much access to information without context leads to excessive certainty and overconfidence (as exhibited by non-specialized department heads and media influencers alike). Universally, “wisdom is knowing you don’t know”, as Socrates once said it best.