What s Beyond The Observable Universe

If a tree falls in a forest and no one's around to hear it, does it actually make a sound? Does it even exist? Is sound only sound if a person hears it? These are the kinds of questions probing the very nature of our reality and observation. It's puzzled philosophers and physicists for centuries and they lead us to an even bigger question. What's beyond the observable universe? It might sound like a science fiction, but it's a legitimate question. Think about it. We can only see a portion of the universe. Actually, even Einstein wrestled with similar concepts. On one of many daily lunchtime walks with his fellow physicist, Abraham Peirce, Einstein suddenly stopped and turned to Peirce and asked, do you really believe that the moon only exists if you look at it? You see, Einstein had a realist view of the universe. He believed that physical objects like the moon have definite properties that exist independently of whether or not they're being observed. He observed in an objective reality that exists regardless of our measurement or observation of it. And it was recorded on the first page of Subtle is the Lord, Peirce's biography of Einstein, that Peirce responded with the 20th century physicist does not, of course, claim to have a definitive answer to this question. And this is because the dominant interpretation of quantum mechanics suggests that quantum systems exist in a superposition of states until measured. I did make a video about that, so check it out if you haven't already up here. Hey space cats, I'm Dr Maggie Lu and in this week's video, we're looking at a similar question. Does the universe beyond what we can see even exist? And if it does, then what's out there? Now, before we dive into the mind bending possibilities of what lies beyond, we have to understand what we mean by the observable universe. It's not a physical barrier like a wall. It's hard to say this is where space ends. It's more like a horizon. So imagine like being on a ship at sea. You can only see so far as to the horizon, but that doesn't mean that the ocean suddenly stops where you can't see any further. There's still sea beyond that. It just means that your perspective is limited. Similarly, the observable universe is the limit of our current cosmic perspective. But as far as we can tell, the universe just keeps going. The furthest that we can see is about 46 billion light years away. Now, you might be thinking, hold on a second, but the universe is only 13.8 billion years old. How is it possible that we can see things that are 46 billion light years away? There's just not been enough time. Well, that's a great question. It's not that we're seeing light that's traveled for 46 billion years. It's more subtle than that. You see, the universe isn't just sitting still. It's expanding. Space itself is stretching like a balloon being blown up. As the universe expands, the distance between galaxies increases. So while the light from a distant galaxy might have only traveled for 13.8 billion years, the space that light has traveled through, whilst it's been stretching the whole time, has increased. And because of this expansion, the current distance to that galaxy can be much greater than the distance that the light has traveled. That's why we can see objects that even though the universe is only 13.8 billion years old. But what about beyond that? Is it just more galaxies, more stars, more space? Or is there something else entirely? One possibility is that the universe is infinite. It just goes on forever in every direction. Beyond the observable horizon lies more of the same thing. Galaxies, stars, planets, cosmic structures stretching endlessly in all directions. Now this idea is both awe-inspiring and humbling because it suggests that the universe is unimaginably vast and that our observable portion is just a speck in this infinite sea. But if it's true, there's no beyond space because space is everything. Even if the universe is finite and it does have a definite edge, finding it would be incredibly difficult. Think about our own planet earth. We live on earth's surface, which is essentially a two-dimensional sphere. And if you walked in a straight line, you would never be able to reach the edge. You would just loop back on yourself. But we know that earth does have a finite surface area. To see the whole earth, to understand its global shape, you have to go up into the third dimension, into space, outside of this 2D sphere into 3D. Now some scientists think that the universe might be similar. We're trapped on its surface, so to speak, which could be some higher dimensional space that we can't directly perceive. Maybe the universe does have an edge, but it's an edge that we can't reach by simply traveling through our familiar three dimensions. It would be like trying to find the edge of the earth by only walking on its surface, which is impossible. We might need to venture into some higher dimensional space to even see the edge, let alone reach it. Now this is where things get incredibly speculative, but also incredibly exciting. Just like we needed to understand the shape of the earth to understand its edge, we need to understand the shape of the universe to understand its boundaries, if it has any. And astronomers are working on that right now using incredibly sophisticated tools and theories to try and piece together this cosmic puzzle. They're studying the cosmic microwave background radiation, the afterglow of the big bang, looking for subtle patterns that might reveal the universe's true shape, and also mapping out dark matter and galaxies in our universe. One of the most intriguing ideas is the concept of a multiverse. The theory of cosmic inflation suggests that our universe underwent a rapid expansion in its earliest times. Some versions of inflation propose that this expansion never truly stops, but just continues in other regions of space, creating bubble universes with different physical constants and different physical laws. Maybe our universe isn't the only one out there. Maybe there are countless other universes out there, squashed up close to one another or even overlapping. Now this would mean that there's no real edge at all, but universes blending into one another. And that's something that's often stated in string theory too. Now here's another twist. The universe is expanding and it's expanding very fast. That means that space between us and distant galaxies is growing. It's like they're all moving further and further away. Eventually they'll be so far away that light won't even be able to reach us anymore. The night sky will get darker and darker and finding the edge of the universe, if it exists, will become even harder. So what's beyond the observable universe? The truth is that we really don't know. We're just scratching the surface of understanding the universe. There's so much more to learn. What lies beyond this is a question that will likely continue to fascinate us and challenge us for centuries to come. Anyway, that's all I have time for this week. Thank you to my YouTube perks members for supporting this video. If you enjoyed it, please don't forget to leave me a like, share, and subscribe.