Now, whenever you hear the word "dark" in physics, you should get very suspicious because it probably means we don't know what we're talking about.
06:21
(Laughter)
06:22
We don't know what dark energy is, but the best idea is that it's the energy of empty space itself, the energy of the vacuum. Now, if you use good old quantum mechanics to work out how strong dark energy should be, you get an absolutely astonishing result. You find that dark energy should be 10 to the power of 120 times stronger than the value we observe from astronomy. That's one with 120 zeroes after it. This is a number so mind-bogglingly huge that it's impossible to get your head around. We often use the word "astronomical" when we're talking about big numbers. Well, even that one won't do here. This number is bigger than any number in astronomy. It's a thousand trillion trillion trillion times bigger than the number of atoms in the entire universe.
07:11
So that's a pretty bad prediction. In fact, it's been called the worst prediction in physics, and this is more than just a theoretical curiosity. If dark energy were anywhere near this strong, then the universe would have been torn apart, stars and galaxies could not form, and we would not be here. So this is the second of those dangerous numbers, the strength of dark energy, and explaining it requires an even more fantastic level of fine-tuning than we saw for the Higgs field. But unlike the Higgs field, this number has no known explanation.
07:44
The hope was that a complete combination of Einstein's general theory of relativity, which is the theory of the universe at grand scales, with quantum mechanics, the theory of the universe at small scales, might provide a solution. Einstein himself spent most of his later years on a futile search for a unified theory of physics, and physicists have kept at it ever since.
08:05
One of the most promising candidates for a unified theory is string theory, and the essential idea is, if you could zoom in on the fundamental particles that make up our world, you'd see actually that they're not particles at all, but tiny vibrating strings of energy, with each frequency of vibration corresponding to a different particle, a bit like musical notes on a guitar string.
08:27
So it's a rather elegant, almost poetic way of looking at the world, but it has one catastrophic problem. It turns out that string theory isn't one theory at all, but a whole collection of theories. It's been estimated, in fact, that there are 10 to the 500 different versions of string theory. Each one would describe a different universe with different laws of physics. Now, critics say this makes string theory unscientific. You can't disprove the theory. But others actually turned this on its head and said, well, maybe this apparent failure is string theory's greatest triumph. What if all of these 10 to the 500 different possible universes actually exist out there somewhere in some grand multiverse? Suddenly we can understand the weirdly fine-tuned values of these two dangerous numbers. In most of the multiverse, dark energy is so strong that the universe gets torn apart, or the Higgs field is so weak that no atoms can form. We live in one of the places in the multiverse where the two numbers are just right. We live in a Goldilocks universe.
09:30
Now, this idea is extremely controversial, and it's easy to see why. If we follow this line of thinking, then we will never be able to answer the question, "Why is there something rather than nothing?" In most of the multiverse, there is nothing, and we live in one of the few places where the laws of physics allow there to be something. Even worse, we can't test the idea of the multiverse. We can't access these other universes, so there's no way of knowing whether they're there or not.
10:00
So we're in an extremely frustrating position. That doesn't mean the multiverse doesn't exist. There are other planets, other stars, other galaxies, so why not other universes? The problem is, it's unlikely we'll ever know for sure. Now, the idea of the multiverse has been around for a while, but in the last few years, we've started to get the first solid hints that this line of reasoning may get born out. Despite high hopes for the first run of the LHC, what we were looking for there -- we were looking for new theories of physics: supersymmetry or large extra dimensions that could explain this weirdly fine-tuned value of the Higgs field. But despite high hopes, the LHC revealed a barren subatomic wilderness populated only by a lonely Higgs boson. My experiment published paper after paper where we glumly had to conclude that we saw no signs of new physics.
10:55
The stakes now could not be higher. This summer, the LHC began its second phase of operation with an energy almost double what we achieved in the first run. What particle physicists are all desperately hoping for are signs of new particles, micro black holes, or maybe something totally unexpecte
ตอนนี้ เมื่อคุณได้ยินคำว่า "เข้ม" ในฟิสิกส์ คุณควรได้สงสัยมาก เพราะมันอาจหมายถึง เราไม่รู้ว่าเรากำลังพูดถึง06:21(หัวเราะ)06:22เราไม่ทราบว่าพลังงานมืด แต่เป็นความคิดที่ดีที่สุดที่เป็นพลังงานของพื้นที่ว่างของตัวเอง พลังงานดูด ตอนนี้ ถ้าคุณใช้ควอนตัมเก่าดีการทำงานจากพลังงานความแข็งแกร่งเข้มควร คุณได้รับผลลัพธ์น่าอัศจรรย์จริง ๆ คุณพบว่า พลังงานมืดควร 10 อำนาจ 120 ครั้งที่แข็งกว่าค่าที่เราสังเกตจากดาราศาสตร์ ที่เป็นหนึ่งกับศูนย์ 120 หลังจากนั้น นี้เป็นตัวเลขดังนั้น mind-bogglingly มากว่า เป็นไปไม่ได้จะเดินหัวของคุณ เรามักจะใช้คำว่า "ดาราศาสตร์" เมื่อเรากำลังพูดถึงตัวเลขขนาดใหญ่ ดี แม้ว่าหนึ่งไม่ทำที่นี่ หมายเลขนี้เป็นเลขใด ๆ ในทางดาราศาสตร์มากกว่า พันล้านล้านล้านล้านล้านล้านครั้งมากกว่าจำนวนอะตอมในจักรวาลทั้งหมดได้07:11เพื่อที่จะทำนายได้ไม่ดีนัก ในความเป็นจริง มันมีการเรียกการคาดเดาที่เลวร้ายที่สุดในฟิสิกส์ และเป็นมากกว่าเพียงแค่ความอยากรู้ทฤษฎี พลังงานมืดได้สะอาด นี้แข็งแกร่ง แล้วจักรวาลจะถูกขาดอพาร์ท ดาวและชื่อดาราจักรอาจได้ และเราจะไม่ได้ที่นี่ เพื่อเป็นหมายเลขดังกล่าวอันตราย ความแข็งแรงของพลังงานมืด และอธิบายว่า ต้องเป็นระดับยอดเยี่ยมยิ่งเพื่อให้เกิดกว่าที่เราเห็นในฟิลด์ Higgs แต่แตกต่างจากฟิลด์ Higgs หมายเลขนี้มีคำอธิบายที่ไม่รู้จัก07:44The hope was that a complete combination of Einstein's general theory of relativity, which is the theory of the universe at grand scales, with quantum mechanics, the theory of the universe at small scales, might provide a solution. Einstein himself spent most of his later years on a futile search for a unified theory of physics, and physicists have kept at it ever since.08:05One of the most promising candidates for a unified theory is string theory, and the essential idea is, if you could zoom in on the fundamental particles that make up our world, you'd see actually that they're not particles at all, but tiny vibrating strings of energy, with each frequency of vibration corresponding to a different particle, a bit like musical notes on a guitar string.08:27So it's a rather elegant, almost poetic way of looking at the world, but it has one catastrophic problem. It turns out that string theory isn't one theory at all, but a whole collection of theories. It's been estimated, in fact, that there are 10 to the 500 different versions of string theory. Each one would describe a different universe with different laws of physics. Now, critics say this makes string theory unscientific. You can't disprove the theory. But others actually turned this on its head and said, well, maybe this apparent failure is string theory's greatest triumph. What if all of these 10 to the 500 different possible universes actually exist out there somewhere in some grand multiverse? Suddenly we can understand the weirdly fine-tuned values of these two dangerous numbers. In most of the multiverse, dark energy is so strong that the universe gets torn apart, or the Higgs field is so weak that no atoms can form. We live in one of the places in the multiverse where the two numbers are just right. We live in a Goldilocks universe.09:30Now, this idea is extremely controversial, and it's easy to see why. If we follow this line of thinking, then we will never be able to answer the question, "Why is there something rather than nothing?" In most of the multiverse, there is nothing, and we live in one of the few places where the laws of physics allow there to be something. Even worse, we can't test the idea of the multiverse. We can't access these other universes, so there's no way of knowing whether they're there or not.10:00
So we're in an extremely frustrating position. That doesn't mean the multiverse doesn't exist. There are other planets, other stars, other galaxies, so why not other universes? The problem is, it's unlikely we'll ever know for sure. Now, the idea of the multiverse has been around for a while, but in the last few years, we've started to get the first solid hints that this line of reasoning may get born out. Despite high hopes for the first run of the LHC, what we were looking for there -- we were looking for new theories of physics: supersymmetry or large extra dimensions that could explain this weirdly fine-tuned value of the Higgs field. But despite high hopes, the LHC revealed a barren subatomic wilderness populated only by a lonely Higgs boson. My experiment published paper after paper where we glumly had to conclude that we saw no signs of new physics.
10:55
The stakes now could not be higher. This summer, the LHC began its second phase of operation with an energy almost double what we achieved in the first run. What particle physicists are all desperately hoping for are signs of new particles, micro black holes, or maybe something totally unexpecte
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