Coming to Our Senses

Natural History Magazine

by Neil deGrasse Tyson

From Natural History Magazine, March 2001

Equipped with his five senses, man explores the universe around him and calls the adventure science.

— Edwin P. Hubble 1948

Our eyes are special detectors. They allows us to register information not only from across the room but from across the universe. Without vision, the science of astronomy would never have been born and our capacity to measure our place in the universe would have been hopelessly stunted. Think of bats. Whatever bat secrets gets passed from one generation to the next, you can bet that none of them are based on the appearance of the night sky.

When thought of as an ensemble of experimental tools, our collective senses enjoy an astonishing acuity and range of sensitivity. Our ears can register the thunderous launch of the space shuttle, yet they can also hear a mosquito buzzing a foot away from our head. Our sense of touch allows us to feel the magnitude of a bowling ball dropped on our big toe, just as we can tell when a one-milligram bug crawls along our arm. Some people enjoy munching on habanero peppers while sensitive tongues can identify the presence of food flavors on the level of parts per million. And our eyes can register the bright sandy terrain on a sunny beach, yet these same eyes have no trouble spotting a lone match, freshly lit, hundreds of feet across a darkened auditorium.

Before we get carried away in praise of ourselves, note that what we gain in breadth, we lose in precision because we register the world's stimuli in logarithmic rather than linear increments. For example, if you increase the energy of a sound's volume by a factor of ten, your ears will judge this change to be rather small. Increase it by a factor of two and you will barely take notice. The same holds for our capacity to measure light. If you have ever viewed a total solar eclipse you may have noticed that the Sun's disk must be at least ninety percent covered by the Moon before anybody comments that the sky has darkened. The stellar magnitude scale of brightness, the well-known acoustic decibel scale, and the seismic scale for earthquake severity are each logarithmic in part because of our biological propensity to see, hear, and feel the world that way.

What, if anything, lies beyond our senses? Does there exist a way of knowing that transcends our biological interfaces with the environment?

Consider that the human machine, while good at decoding the basics of our immediate environment—like when it's day or night or when a creature is about to eat you—has very little talent for decoding how the rest of nature works without the tools of science. If we want to know what's out there then we require detectors other than the one's we are born with. In nearly every case, the job of a scientific apparatus is to transcend the breadth and depth of our senses.

Some people boast of having a sixth sense, where they profess to know or see things that others cannot. Fortunetellers, mind readers, and mystics are at the top of this list of those who lay claim to mysterious powers. Insodoing, they instill widespread fascination in others, especially book publishers and television producers. The questionable field of parapsychology is founded on the expectation that at least some people actually harbor this talent. To me, the biggest mystery of them all is why so many fortune-telling psychics chose to work the phones on TV hotlines instead of becoming insanely wealthy trading futures contracts on Wall Street. Quite independent of this profound mystery, the persistent failures of controlled, double blind experiments to support the claims of parapsychology suggest that what's going on is non-sense rather than sixth-sense.

On the other hand, modern science wields dozens of senses. And scientists do not claim these to be the expression of special powers, just special hardware. In the end, of course, the hardware converts the information gleaned from these extra senses into simple tables, charts, diagrams, or images that our inborn senses can interpret. In the original Star Trek sci-fi series, the crew that beamed down from their starship to the uncharted planet always brought with them a tricorder, which was a hand-held device that could analyze anything they encountered, living or inanimate, for its basic properties. As you waved the tricorder over the object-in-question it made an audible spacey sound that was interpreted by the user.

Suppose a glowing blob of some unknown substance were parked right in front of you. Without some diagnostic tool like a tricorder to help, humans would be clueless of the blob's chemical or nuclear composition. Nor could we know whether it has an electromagnetic field, or whether it emits strongly in gamma rays, x-rays, ultraviolet, microwaves or radio waves. Nor could we determine the blob's cellular or crystalline structure. If the blob were far out in space, appearing as an unresolved point of light in the sky, our five senses would offer us no insight to its distance, velocity though space, or its rate of rotation. We further would have no capacity to see the spectrum of colors that compose its emitted light, nor could we know whether the light is polarized.

Without hardware to help our analysis, and without a particular urge to lick the stuff, all you can report back to the starship is, Captain, it's a blob. Apologies to Edwin P. Hubble, but his opening remark, while poignant and poetic, should have instead been

Equipped with our five senses, along with telescopes and microscopes and mass spectrometers and seismographs and magnetometers and particle accelerators and detectors across the electromagnetic spectrum, we explore the universe around us and call the adventure science.

Think of how much richer the world would appear to us and how much earlier the nature of the universe would have been discovered if we were born with high-precision, tunable eyeballs. Dial up the radio wave part of the spectrum and the daytime sky falls as dark as night, except for some choice locations. Our galaxy's center is one of the brightest spots on the sky and is located behind some of the principal stars of the constellation Sagittarius. Tune into microwaves and the entire universe is aglow with a remnant from the early universe, a wall of light set forth 300,000 years after the big bang. Tune into x-rays and the locations of black holes, with matter spiraling into them, are spotted immediately. Tune into gamma rays and see titanic explosions scattered throughout the universe at a rate of about one pert day. Watch the effect of the explosion on the surrounding material is it heats up and glows in other bands of light.

If we were born with magnetic detectors, the compass would never have been invented because we wouldn't ever need one. Just tune into Earth's magnetic field lines and the direction of magnetic North looms like Oz beyond the horizon. If we had spectrum analyzers within our retinas, we would not have to wonder what was in the air we were breathing. We could just look at it and know whether or not it contained sufficient oxygen to sustain human life. And we would have learned thousands of years ago that the stars and nebulae in the galaxy contain the same chemical elements found here on Earth.

And if we were born with big eyes and built-in Doppler motion detectors, we would have seen immediately, even as grunting troglodytes, that the entire universe is expanding—all distant galaxies are receding from us.

If our eyes had the resolution of high-performance microscopes, nobody would have ever blamed the plague and other sicknesses on divine wrath. The bacteria and viruses that made you sick would be in plain view as they crawled on your food or as they slid through open wounds in your skin. With simple experiments, you could easily tell which these bugs were bad and which were good. And of course post-operative infection problems would have been identified and solved hundreds of years earlier.

If we could detect high-energy particles, we would spot radioactive substances from great distances. No Geiger counters necessary. You could even watch radon gas seep through the basement floor of your home and not have to pay somebody to tell you about it.

The honing of our senses from birth through childhood allows us as adults to pass judgment on events and phenomena in our lives, declaring whether or not they make sense. Problem is, hardly any scientific discoveries of the past century flowed from the direct application of our five senses. They flowed instead from the direct application of sense-transcendent mathematics and hardware. This simple fact is entirely responsible for why, to the average person, relativity, particle physics, and ten-dimensional string theory make no sense. Include in the list black holes, wormholes, and the big bang. Actually, these ideas don't make much sense to scientists either, until we have explored the universe for a long time with all senses that are technologically available. What emerges, eventually, is a newer and higher level of common sense that enables a scientist think creatively and to pass judgment in the unfamiliar underworld of the atom or in the mind-bending domain of higher dimensional space. The twentieth-century German physicist Max Planck made a similar observation about discovery of quantum mechanics:

Modern Physics impresses us particularly with the truth of the old doctrine which teaches that there are realities existing apart from our sense-perceptions, and that there are problems and conflicts where these realities are of greater value for us than the richest treasures of the world of experience.

Our five senses even interfere with sensible answers to stupid metaphysical questions like, If a tree falls in the forest and nobody is around to hear it, did it make a sound? My best answer is, How do you know it fell? But that just gets people angry. So I offer a senseless analogy, Q: If you can't smell the carbon monoxide, then how do you know it's there? A: You drop dead. (Natural gas is also odorless to the human nose. For our protection, a pungent smell is added so that gas leaks can be safely identified and located.) In modern times, if the sole measure of what's out there flows from your senses then a precarious life awaits you.

Discovering new ways of knowing has always heralded new windows on the universe—new detectors we can add to our growing list of non-biological senses. Whenever this happens, a new level of majesty and complexity in the universe reveals itself to us, as though we were technologically evolving into super-sentient beings, always coming to our senses.

Neil deGrasse Tyson is the Frederick P. Rose Director of New York City's Hayden Planetarium. This semester he is teaching astrophysics at Princeton University.