Seeing the Unseeable
This past week I’ve been slowly making my way through Ed Yong’s “An Immense World”. The subtitle is “How animal senses reveal the hidden realms around us.” The first three chapters are “Leaking sacks of chemicals”, about smells and tastes, “Endless ways of seeing”, about light, and “Rurple, Grurple, Yurple”, about colour.
It was Chapter 3 in particular that fascinated me. Most humans, and all male humans, are trichromats - we have receptors for 3 light frequencies, which we interpret as Red, Green, Blue. A very few female humans have a 4th receptor for a shade most of us see as green. As Yong points out though, these few women don’t have super-human vision. For them, it is just the way the world is.
That’s because it may be the eye that intercepts the light, but it is the brain that turns those signals into vision. It’s a case of “we don’t know what we don’t know”. There are also cases, particularly people who have had their eye’s lens removed, who can see into the ultraviolet. They report that it looks like “blue-white”. Claude Monet is one example, his later works, after the surgery, feature more and brighter blues. The brain doesn’t know what to do with the new information, so interprets it using known parameters.
Animals have different visual capabilities. Dogs are a famous example, being dichromats. Their “Umwelt”, as Yong calls the sensory experience, is missing red and blue. Some animals have far more, and more finely tuned, visual sensors. The Mantis shrimp (registration on site) is the classic example - it has 12 differently tuned receptors. However, recent research shows that they actually distinguish fewer gradations of colour than can humans. That’s because each type of sensor has a specific task - motion detection, seeing above, seeing below, seeing straight ahead. Few animals have our capability of seeing “everything at once”. And even that is an illusion created by our brains.
What does that have to do with the picture at the top of this post? Everything.
That image is from the JWST - James Webb Space Telescope. It is a mapping from infra-red (which humans can’t see) to an arbitrary human-visible range. From the JWST website: “Since infrared light is invisible to the human eye, the light has been mapped onto the visible spectrum.”
The JWST doesn’t “see” in the range humans do. It was specifically designed to “see” in the infra-red. Why? Because of the expansion of the Universe. It’s the doppler effect applied to light - the “red shift”. The more distant an astronomical object from us, the faster it is fleeing our location, and the more red it appears. In order to probe back to near the Big Bang, we must gather “light” at lower and lower frequencies. Radio telescopes cover a huge range of even lower frequencies, particularly the CMB. That’s the Cosmic Microwave Background that proved that our Universe started with the Big Bang - or at least something that looks like it.
But radio waves, because they are long, have low resolution. The lower the frequency, the longer the wavelength, and the less resolution we can extract. Infra-red fills a gap that we can’t normally see. The Earth’s atmosphere filters much of the infra-red. So a space-based telescope that senses infra-red was necessary in order for us to probe deeper into the Universe’s past with high enough resolution to learn anything new. Hence the JWST.
But it creates PR problems. A common complaint in online discussion forums is that “it’s all just Photoshop anyway”. Those same people are what I call the “we shouldn’t have left the caves” crowd. They decry any investments in research or exploration. They use the results of historical and present R&D (chemistry, physics, quantum mechanics; making modern electronics and the Internet possible) to say we shouldn’t “waste money” on looking outside our current knowledge base. Most of them commit egregious logic errors as well. I suspect most of them lead lonely lives in a dark, dank place.
One of the most significant successes of human civilisation is using our intelligence, knowledge, and skills to expand our capabilities. Whether it was an atlatl or the JWST, the concept is the same. We are who and what we are due to our inquisitive nature. Unique among all of Earth’s creatures, we have the capability to go beyond our planet of birth. For now, it’s via our emissaries, the telescopes and robots. We will either follow them in the flesh, or die trying. But we must try. The alternative is extinction.