If we cannot see them with the naked eye? Let me explain in the simplest possible manner....
SCI-TECH
With the advent of the 21st century technology, astrophotography cameras have been introduced, capturing the high-quality pictures of astronomical bodies—including those of the planets, stars, galaxies, and a lot more.
Here's a picture of the Milky Way galaxy, captured using an advanced camera from a spot where it is not easily visible to the naked eye of a human being. But, now you might be wondering how such images are captured from a scientific point of view, if we cannot see them with the naked eye? Let me explain in the simplest possible manner.
Basically, this is a long exposure shot, which means that cameras’ lens was open for around 10 seconds to collect as much light as possible. In that way, the captured image became bright enough to illuminate faint details. Hence, that's why you feel like the sky is bright although it was much darker to the naked eye in reality. In contrast to the long exposure shots by the camera lenses, our eyes cannot do the long exposure; which means that whatever light falls on our eyes is quickly processed by our brain, unlike most of the modern cameras of all types.
Additionally, we need to adjust camera settings and processing to get even better photos. So, cameras and eyes have a shutter which is like a window: you open it and it lets the light in. And inside of it there's a film—called retina in the eyes—to receive light and convert it into an image. Now, with eyes, you can keep the shutter open but as soon as the light falls on the retina, it converts it into an image (or sends it to our brains for image processing)—which means that it cannot accumulate light to convert a dark image into a brighter one. However, with cameras it is different, since you can keep the shutter open for a much longer and customizable time, and it will keep collecting light during all this time. Once you think that it has collected enough light, you can ask it to process it into an image. The more the time given, the brighter the image obtained, whereas the lesser the time given, the darker the image comparatively. Also, the light from the distant galaxies is extremely faint, so cameras’ shutters must be opened for hours to collect enough light for capturing their images.
Now, here's a simple experiment you can do. Look at your eyes in a mirror. The brown or black (or green or blue, in some people) round thing in the middle is called iris. You see another circle in the middle of the iris, which is called ‘’pupil’’ and it is always black.
The size of the pupil is not fixed and adjusts automatically in relation to the light it is being exposed to. If it is dark outside, the pupil is dilated. On the other hand, if it is in case bright outside, the pupil is constricted. Therefore, for this experiment, you need to do the following things step-by-step:
Take a torch.
Put someone you know in a dark room; be it any one of your siblings, your friend, or anyone you know.
Turn on the torch, and place it on this person’s shoulders so that their eyes are still in the dark.
Now, bring the torch forward and shine the light into the person’s eyes from a few inches.
Finally, observe the pupils’ size of the person.
With all the aforementioned things done, you will see a reaction. Basically, the size of the pupil will gradually decrease as you shine light onto it. That will be the result of this experiment. Why does this happen? It is because the iris of our eyes relaxes when the light is more, but when there is dim light, it contracts, thereby making the pupil increase its size.
But, another question arises here: is the brain ultimately the reason why we cannot see far distances, despite its usefulness in various other aspects of life?
So basically, it’s not the fault of our brain entirely, but the structure of our eyes. Eyes have evolved to adapt for a hunter forager lifestyle, where you are prey and/or hunter and not far away from your own land. Therefore, you don't need good acuity and distant vision for that. However, birds like hawks have evolved extremely sharp vision over the course of time because they must detect their prey from a far distance.
Nonetheless, our evolution story is still in its infancy phase and it will continue for centuries to come. However, the difference between the other species and human beings is that they had to rely on natural selection and evolution to survive in the harsher conditions of environment and competition; whereas, we were able to use our brains to good effect. Moreover, we have not only survived as a species but have thrived to overcome the shortcomings given to us by the nature. One example of our advancement is the processing of our world by our own eyes but enhancing our abilities through HD cameras and astrophotography telescopes. Indeed, we can now process our world at both ends; from hunter-gatherer perspectives as well as the species which is planning to colonize other astronomical bodies, utilizing the technology we have developed using our brains.
Acknowledgment: The author is grateful of Dr. Talha for providing the Milky Way galaxy’s image.
