91download.com supports a wide range of platforms, including YouTube, Facebook, Twitter, TikTok, Instagram, Dailymotion, Reddit, Bilibili, Douyin, Xiaohongshu and Zhihu, etc. Click the download button below to parse and download the current video
Have you ever gazed up at the night sky and wondered about the distances to the stars and galaxies? Imagine a galaxy so far away that its light took 25,000 years to reach us. How far do you think it is? 25,000 light years? That's what you might expect. But what if I told you that the galaxy is actually 32 billion light years away? Confused? Let's dive into the fascinating world of cosmic expansion.
When we talk about distances in space, we often use light years as a measure. A light year is the distance light travels in one year, which is about 9.46 trillion kilometers. So, if a galaxy's light takes 13.4 billion years to reach us, you'd logically assume it's 13.4 billion light years away. However, that's not the case for GNZ11, a galaxy discovered in 2016.
GNZ11 is so far away that its light took 13.4 billion years to reach us, but its current distance is a staggering 32 billion light years. How is this possible? The answer lies in the expansion of the universe. As light travels across space, the space itself is expanding, making the distance between us and the galaxy larger over time.
The universe was once thought to be a stagnant entity, with everything in its place. However, we now know that space is not static; it's dynamic and expanding. This expansion means that as light travels from one point to another, the space between those points grows, making the journey longer than expected.
This expansion is not uniform across the universe. Galaxies are receding from us, and the further away they are, the faster they're moving. This phenomenon was first observed by Edwin Hubble and is known as Hubble's Law. It states that the velocity of a galaxy is proportional to its distance from us. This means that some galaxies are moving away from us at speeds approaching the speed of light.
Now, you might be wondering, can we see galaxies that are moving away from us faster than the speed of light? The answer is both yes and no. We can see the light that was emitted from these galaxies when they were much closer to us, but we won't see their current state because the light from their current position will never reach us. This is due to the expansion of space carrying the light away from us before it can reach us.
The boundary of this visibility is known as the Hubble Sphere. Beyond this sphere, everything is moving away from us faster than the speed of light. However, within this sphere, we can still observe the light from galaxies, even if they are currently beyond our reach.
So, what does this mean for our understanding of the universe? It means that the observable universe is much larger than we once thought. It's a mind-bending concept to consider that we can see light from galaxies that are no longer there, and there are galaxies we'll never see because they are moving away from us at speeds exceeding the speed of light.
This cosmic expansion challenges our understanding of space and time. It's a journey that takes us beyond the speed of light, into a universe that is both vast and mysterious. And as we continue to explore and learn, we come to appreciate the beauty and complexity of the cosmos we call home.
Share on Twitter Share on Facebook