2025年11月23日
The Observable Universe
Illustration Credit & Licence: Wikipedia, Pablo Carlos Budassi
Explanation: How far can you see? Everything you can see, and everything you could possibly see, right now, assuming your eyes could detect all types of radiations around you — is the observable universe. In light, the farthest we can see comes from the cosmic microwave background, a time 13.8 billion years ago when the universe was opaque like thick fog. Some neutrinos and gravitational waves that surround us come from even farther out, but humanity does not yet have the technology to detect them. The featured image illustrates the observable universe on an increasingly compact scale, with the Earth and Sun at the center surrounded by our Solar System, nearby stars, nearby galaxies, distant galaxies, filaments of early matter, and the cosmic microwave background. Cosmologists typically assume that our observable universe is just the nearby part of a greater entity known as “the universe” where the same physics applies. However, there are several lines of popular but speculative reasoning that assert that even our universe is part of a greater multiverse where either different physical constants occur, different physical laws apply, higher dimensions operate, or slightly different-by-chance versions of our standard universe exist.
Explore the Observable Universe: Random APOD Generator
Tomorrow’s picture: stellar shell game
可观测宇宙
插图版权及授权: Wikipedia, Pablo Carlos Budassi
说明: 你能看到多远？你现在所能看到的一切，以及你现在可能看到的一切（假设你的眼睛能够探测到周围所有类型的辐射），这就是可观测宇宙。在光的范畴内，我们所能看到的最远距离来自宇宙微波背景辐射，那是138亿年前前宇宙如同浓雾般不透明的时期。环绕着我们的一些微中子和重力波来自更遥远的宇宙，但人类目前还没有技术探测到它们。这张影像以逐渐紧凑的尺度展示了可观测宇宙，地球和太阳位于中心，周围环绕着我们的太阳系、邻近的恒星、邻近的星系、遥远的星系、早期物质的丝状结构以及宇宙微波背景辐射。宇宙学家通常假设我们的可观测宇宙只是一个被称为“宇宙”的更大实体中的一部分，在这个更大的实体中，同样的物理定律仍然适用。然而，一些流行的推测性论证断言，即使是我们的宇宙也是更广阔的多重宇宙的一部分，在这个多重宇宙中，可能存在不同的物理常数、不同的物理定律、更高的维度，或者存在与我们的标准宇宙略有不同的版本（纯属偶然）。
探索可观测宇宙: 随机APOD生成器
明日的图片: stellar shell game
