How small are we?

In 1995, during the winter season, scientists directed the Hubble Telescope towards a specific region in the sky close to the Big Dipper. This area was chosen because it was dark and free from light pollution caused by nearby stars. The decision to focus on this location was quite daring, as there was uncertainty about what would be discovered, if anything at all. Over a period of ten consecutive days, the telescope diligently captured approximately 150 hours of exposure of the same area. The outcome of this endeavor was nothing short of extraordinary: an awe-inspiring image of more than 1,500 distinct galaxies shimmering within a small portion of the vast universe

Now, let's take a step back to understand the scale of this image. If you were to take a ballpoint pen and hold it at arm's length in front of the night sky, focusing on its very tip, that is what the Hubble Telescope captured in its first Deep Field image. In other words, those 3,000 galaxies were seen in just a tiny speck of the universe, approximately one two-millionth of the night sky. To put all this in perspective, the average human measures about 1.7 meters. With Earth's diameter at 12,700 kilometers, that's nearly 7.5 million humans lined up head to toe. The Apollo 8 astronauts flew a distance of 380,000 kilometers to the moon. And our relatively small Sun has a diameter of about 1.4 million kilometers, or 110 times the Earth's diameter.

A step further, The Milky Way contains a range of 100 to 400 billion stars, including our Sun. Each galaxy seen in the Deep Field image consists of billions of stars, at the very least. Scientists made adjustments to the Hubble Telescope's optics almost ten years after capturing the Deep Field image. They then conducted another long exposure lasting approximately four months, resulting in the observation of 10,000 galaxies. Out of these, half have been examined more clearly in the eXtreme Deep Field image (XDF). By combining over ten years of photographs, the XDF shows galaxies so distant that they're only one ten-billionth the brightness that the human eye can perceive. So, what can we learn about the universe from the Deep Field images?

In a study of the universe, space and time are inextricably linked. That's because of the finite speed of light. So the Deep Field images are like time machines to the ancient universe. They reach so far into space and time that we can observe galaxies that existed over 13 billion years ago. This means we're looking at the universe as it was less than a billion years after the Big Bang, and it allows scientists to research galaxies in their infancy. The Deep Field images have also shown that the universe is homogeneous. That is, images taken at different spots in the sky look similar. That's incredible when we think about how vast the universe is.

Why would we expect it to be the same across such huge distances? On the scale of a galaxy, let alone the universe, we're smaller than we can readily comprehend, but we do have the capacity to wonder, to question, to explore, to investigate, and to imagine. So the next time you stand gazing up at the night sky, take a moment to think about the enormity of what is beyond your vision, out in the dark spaces between the stars.