What We See Isn’t Everything

Humans have remarkably developed civilizations up to the title of the “most intelligent species.” However, we have a big weakness that overshadows us in terms of being “on top” on this planet. This big weakness is that we understand the world through our imperfect sense organs. In other words, the level of our awareness of the world is determined by our sense organs, and we can perceive the world as much as our sense organs allow.

We understand the world by using our five senses: vision, audition, olfaction, gustation, and somatosensation. We tend to trust our vision more than any other senses, just as the saying goes: “It’s better to see something once than to hear about it a thousand times.” It is because vision plays a big role in perceiving objects.

The sense organ of vision collects a large amount of information and sends it to the brain. However, human vision has more limitations than we think.

How much can we trust what we see?

The human eye is very sensitive to distance and size of an object. We cannot see the objects that are a certain distance away, and we cannot perceive the things that are smaller than a certain size, either. Which of the two—things we can see and things we cannot see—do you think are larger in number?

Our hands carry tens of thousands of germs. However, we cannot see the germs no matter how closely we look into our hands. It is because the size that we can observe is around one millimeter.

Humans have invented the microscope to see such tiny, invisible things. The most typical one is the optical microscope which uses visible light and a system of objective lens and eyepiece lens to magnify the images of small samples. Since the optical microscope uses visible light, it cannot observe objects smaller than the wavelength of visible light. The optical microscope can only magnify objects up to 2,000 times because its maximum possible resolution is approximately 0.2 micrometers (μm), which is enough to see cell-size objects.

The electron microscope has been developed to make up for the disadvantages of the optical microscope. The electron microscope has a higher resolving power¹ as it uses electrons with much shorter wavelengths. Microorganisms like viruses that are even smaller than cells can be seen through the electron microscope, which is capable of magnifying objects millions of times and determining the positions of atoms within materials. However, the microscopic world, which is a world smaller than atoms, still remains unseen and unknown; it is only assumed to exist.

1. Resolving power is the minimum distance between two distinguishable objects.

Mosquitoes, which bother us on hot summer nights, appear and disappear quickly. It is because they can flap their wings about 600 times per second. We cannot see their wings flapping. Then what can we see for a second and how closely can we observe it?

We cannot see the beauty of falling water droplets. Instead, high-speed video cameras record the moments that the human eye cannot capture. This suggests that countless things we can hardly perceive are happening all around us right now.

We cannot know what the universe really looks like

Look at the stars twinkling in the night sky. Among the numerous stars, we can see only a few stars with the naked eye. Human eyes can only see the stars that have an apparent magnitude of six or brighter; no more than 2,000 stars are visible in the sky to the naked eye even on a clear night. Although countless stars are shining in the night sky, most of them are too dim to be seen.

It is the telescope that has been invented to overcome these imperfections of the human eye.

The most common type is the optical telescope that uses lenses or mirrors to collect light from distant celestial objects for us to see it. The telescope Galileo made in 1609 had a very narrow field of view, about half the apparent diameter of the Moon, with which he couldn’t see the entire surface of the Moon at once. Now, however, large optical telescopes that are eight to ten meters in diameter have been built, which can gather even the faint light from celestial objects more than ten billion light years away. When the light collected by the telescope is accumulated for a long period of time, we can take photos of beautiful astronomical objects that our eyes cannot see. The invention of the telescope has allowed humans to see farther.

Space looks dark and empty when it is observed with the optical telescope. However, while looking at the pictures of the same place in space taken with various types of electromagnetic waves, we come to realize the limitations of our vision again. In space which looks black and empty to the human eye, there are actually countless celestial materials and objects.

Until the early 20th century, astronomical observations were made within the range of visible light. Now, however, even invisible electromagnetic waves can be detected. We’ve been able to observe things in space that we couldn’t see before, by capturing various types of electromagnetic radiation and analyzing them. Until Karl Jansky, an American physicist and radio engineer, discovered radio waves coming from space, people believed that there were no other objects in space except the ones visible with the optical telescope. However, the universe is full of objects invisible to the human eye.

Whereas the optical telescope gathers visible light from celestial objects, the radio telescope detects radio waves from space, which the optical telescope cannot detect. The images of radio waves we observe are computer-generated images based on the information obtained by the antenna via radio waves.

Most radio waves that can be detected on Earth enable us to see things made up of information from atoms and molecules.

The atmosphere does not filter electromagnetic radiation completely. Visible light, too, bends as it passes through the atmosphere, which results in distorted images of astronomical objects. The wavelengths except visible light and radio waves are either absorbed or reflected by the Earth’s atmosphere. So in order to observe electromagnetic radiation, we need to launch a telescope into space. The Hubble Space Telescope [HST] is the first major optical telescope to be placed in space. The HST mainly observes ultraviolet and visible light. Through the space telescopes, humans can witness the birth of stars not only in visible light but also in infrared radiation emanating from protostars, and also observe the active galaxies that form stars in ultraviolet light. X-rays and gamma rays reveal the violent activity of the cosmos like supernova explosions.

When looking at stars, we are actually looking into the past. The universe is so vast that not even light which travels at a tremendous speed is fast enough to show us the entire universe. If a star observed from Earth is 100 million light years away, it emitted its light 100 million years ago, and the star might not exist now. According to modern science, the size of the observable universe is about 13.7 billion light years. Even now stars and galaxies are born and die in the universe, but humans can barely observe them in the far future. The universe is too far away to be seen; it cannot be perceived by human speed and distance.

Ever since ancient times, humans have been longing for the invisible world. Now that science has developed, let’s think if the world our eyes see is really everything. Today, we can observe the universe which was too far away to see, the world which was too small to see, and the moments that were too quick to see. Then can we say that the world we see through science is everything?

Just as a frog in the well does not know about the outside world, and just as a dragonfly nymph in the water does not know that it will fly in the sky with transparent wings, we may be living with a fixed idea. There are more things we cannot see than the things we can see with our imperfect eyes. Therefore, it is only humans’ conceit to believe only what is seen.

We need to believe that the world we do not see definitely exists. This is the mindset we need to have at this present time when science has developed.