Many other physicists get a little blasé about the vastness of the cosmos and forces too powerful to comprehend. You can reduce it all to mathematics, tweak some equations, and get on with your day. But the shock and vertigo of the recognition of the fragility of everything, and my own powerlessness in it, has left its mark on me. There’s something about taking the opportunity to wade into that cosmic perspective that is both terrifying and hopeful, like holding a newborn infant and feeling the delicate balance of the tenuousness of life and the potential for not-yet-imagined greatness. It is said that astronauts returning from space carry with them a changed perspective on the world, the “overview effect,” in which, having seen the Earth from above, they can fully perceive how fragile our little oasis is and how unified we ought to be as a species, as perhaps the only thinking beings in the cosmos.
by Katie Mack
From one of the most dynamic rising stars in astrophysics, an accessible and eye-opening look at five ways the universe could end, and the mind-blowing lessons each scenario reveals about the most important concepts in cosmology.
We know the universe had a beginning. With the Big Bang, it expanded from a state of unimaginable density to an all-encompassing cosmic fireball to a simmering fluid of matter and energy, laying down the seeds for everything from black holes to one rocky planet orbiting a star near the edge of a spiral galaxy that happened to develop life as we know it. But what happens to the universe at the end of the story? And what does it mean for us now?
Dr. Katie Mack has been contemplating these questions since she was a young student, when her astronomy professor informed her the universe could end at any moment, in an instant. This revelation set her on the path toward theoretical astrophysics. Now, with lively wit and humor, she takes us on a mind-bending tour through five of the cosmos’s possible finales: the Big Crunch, Heat Death, the Big Rip, Vacuum Decay (the one that could happen at any moment!), and the Bounce. Guiding us through cutting-edge science and major concepts in quantum mechanics, cosmology, string theory, and much more, The End of Everything is a wildly fun, surprisingly upbeat ride to the farthest reaches of all that we know.
多くの物理学者が、宇宙の広大さと、強大すぎて理解できない力とに、少し無感覚になってしまう。すべてを数学に帰してしまい、方程式をいくつかこねくりまわして、日々の仕事をこなしてもいいわけだ。しかし、万物の脆弱さと、そのなかで自分がいかに無力であるかを認識したときの、ショックとめまいに似た感覚は、私の心に深い印象を残した。
恐ろしいと同時に希望にあふれてもいる、その宇宙的な視点へと努力して進んでいくことには、一種特別なものがある。それは、生まれたばかりの赤ん坊をだいたときに、命の危うさと、そこに潜在的に存在する、まだ想像されたことすらない偉大さとの微妙な均衡を感じることにも似ている。宇宙から帰還する宇宙飛行士は、それまでとはまったく違う世界観をもって戻ってくるといわれている。いわゆり「概観効果」だが、上空から地球を見るという経験をした彼らは、私たちの小さなオアシスがいかに壊れやすいものか、そして、私たちは一つの種として、おそらくは宇宙で唯一の思考する存在として、いかに一つにまとまらねばならないかを強く認識するのだという。
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by ケイティ・マック
translated by 吉田三知世
この宇宙は必ず終わる。──いつ、どうやって!?
「万物が究極的に破壊される」瞬間を描く5つのシナリオとは?
〈最新理論が予言する「5つの終末シナリオ」〉
1: ビッグクランチ──急激な収縮を起こし、潰れて終わる
2: 熱的死──膨張の末に、あらゆる活動が停止する
3: ビッグリップ──ファントムエネルギーによって急膨張し、ズタズタに引き裂かれる
4: 真空崩壊──「真空の泡」に包まれて完全消滅する突然死
5: ビッグバウンス──「特異点」で跳ね返り、収縮と膨張を何度も繰り返す
KATIE MACK, ASTROPHYSICIST
https://www.astrokatie.com/research
DARK MATTER
The vast majority of the matter in the Universe appears to be entirely invisible to us. This mysterious substance, dubbed dark matter, has mass and a gravitational pull, but doesn’t seem to interact in any significant way via any of the other forces. We don’t yet know what dark matter is made of, but there’s a lot of very good evidence that it is real and is out there (and possibly passing through us right now!).
I study a lot of different aspects of dark matter, including finding new ways to rule out or confirm various ideas about what it might be. In some of my most recent work, I study models of dark matter in which it has some very rare interactions with itself or with other kinds of matter, and could even annihilate with itself when enough is collected together. These interactions could have had an impact on the growth of the first stars and galaxies in the Universe.
VACUUM DECAY
With the discovery of the Higgs boson, particle physicists found out something disconcerting about our Universe: it might not be entirely stable. The basic idea is that the mathematical structure that determines the laws of physics — what we call the “vacuum state” — might not be the one that the Universe, in some sense, “prefers.” If this is true, then there’s a chance that someday our Universe will suddenly transition to the preferred state, destroying everything in the Universe. The chances of this happening any time soon are astronomically low, but it’s a dramatic enough possibility that physicists are taking it seriously and trying to understand if it’s actually possible, or if it is, instead, giving us a hint about some new physics that could change the picture entirely.
COSMIC DAWN AND REIONIZATION
In the beginning, there was the Hot Big Bang. This is a term cosmologists use to talk about the time when the cosmos was hotter, denser, and in some sense, smaller than it is today. We see evidence of this hot dense state by looking at the cosmic microwave background — the afterglow of the Big Bang. But once the primordial plasma cooled, the Universe was mostly rapidly diffusing neutral hydrogen, with the denser pockets slowly being pulled together by dark matter to form the first stars and galaxies. During these “cosmic dark ages,” before the stars, the cosmos was dark and opaque to visible light. The era when stars first ignited is known as the “cosmic dawn,” and when there were enough of them burning to cut through the haze of the neutral gas and ionize everything, the Universe underwent a process called “reionization.”
Understanding reionization would give us insights into the very first structures in the Universe, and could even help us answer some of the most challenging questions about dark matter and the evolution of the cosmos.