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← How we explore unanswered questions in physics | James Beacham | TEDxBerlin

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  1. There is something about physics
  2. that has been really bothering me
    since I was a little kid.
  3. And it's related to a question
  4. that scientists have been asking
    for almost 100 years,
  5. with no answer.
  6. How do the smallest things in nature,
  7. the particles of the quantum world,
  8. match up with the largest
    things in nature --
  9. planets and stars and galaxies
    held together by gravity?
  10. As a kid, I would puzzle
    over questions just like this.
  11. I would fiddle around
    with microscopes and electromagnets,
  12. and I would read
    about the forces of the small
  13. and about quantum mechanics
  14. and I would marvel at how well
    that description matched up
  15. to our observation.
  16. Then I would look at the stars,
  17. and I would read about how well
    we understand gravity,
  18. and I would think surely,
    there must be some elegant way
  19. that these two systems match up.
  20. But there's not.
  21. And the books would say,
  22. yeah, we understand a lot
    about these two realms separately,
  23. but when we try to link
    them mathematically,
  24. everything breaks.
  25. And for 100 years,
  26. none of our ideas as to how to solve
    this basically physics disaster,
  27. has ever been supported by evidence.
  28. And to little old me --
  29. little, curious, skeptical James --
  30. this was a supremely unsatisfying answer.
  31. So, I'm still a skeptical little kid.
  32. Flash-forward now
    to December of 2015,
  33. when I found myself smack in the middle
  34. of the physics world
    being flipped on its head.
  35. It all started when we at CERN
    saw something intriguing in our data:
  36. a hint of a new particle,
  37. an inkling of a possibly extraordinary
    answer to this question.
  38. So I'm still a skeptical
    little kid, I think,
  39. but I'm also now a particle hunter.
  40. I am a physicist at CERN's
    Large Hadron Collider,
  41. the largest science
    experiment ever mounted.
  42. It's a 27-kilometer tunnel
    on the border of France and Switzerland
  43. buried 100 meters underground.
  44. And in this tunnel,
  45. we use superconducting magnets
    colder than outer space
  46. to accelerate protons
    to almost the speed of light
  47. and slam them into each other
    millions of times per second,
  48. collecting the debris of these collisions
  49. to search for new, undiscovered
    fundamental particles.
  50. Its design and construction
    took decades of work
  51. by thousands of physicists
    from around the globe,
  52. and in the summer of 2015,
  53. we had been working tirelessly
    to switch on the LHC
  54. at the highest energy that humans
    have ever used in a collider experiment.
  55. Now, higher energy is important
  56. because for particles,
    there is an equivalence
  57. between energy and particle mass,
  58. and mass is just a number
    put there by nature.
  59. To discover new particles,
  60. we need to reach these bigger numbers.
  61. And to do that, we have to build
    a bigger, higher energy collider,
  62. and the biggest, highest
    energy collider in the world
  63. is the Large Hadron Collider.
  64. And then, we collide protons
    quadrillions of times,
  65. and we collect this data very slowly,
    over months and months.
  66. And then new particles might show up
    in our data as bumps --
  67. slight deviations from what you expect,
  68. little clusters of data points
    that make a smooth line not so smooth.
  69. For example, this bump,
  70. after months of data-taking in 2012,
  71. led to the discovery
    of the Higgs particle --
  72. the Higgs boson --
  73. and to a Nobel Prize
    for the confirmation of its existence.
  74. This jump up in energy in 2015
  75. represented the best chance
    that we as a species had ever had
  76. of discovering new particles --
  77. new answers to these
    long-standing questions,
  78. because it was almost
    twice as much energy as we used
  79. when we discovered the Higgs boson.
  80. Many of my colleagues had been working
    their entire careers for this moment,
  81. and frankly, to little curious me,
  82. this was the moment
    I'd been waiting for my entire life.
  83. So 2015 was go time.
  84. So June 2015,
  85. the LHC is switched back on.
  86. My colleagues and I held our breath
    and bit our fingernails,
  87. and then finally we saw
    the first proton collisions
  88. at this highest energy ever.
  89. Applause, champagne, celebration.
  90. This was a milestone for science,
  91. and we had no idea what we would find
    in this brand-new data.
  92. And then a few weeks later,
    we found a bump.
  93. It wasn't a very big bump,
  94. but it was big enough to make
    you raise your eyebrow.
  95. But on a scale of one to 10
    for eyebrow raises,
  96. if 10 indicates that you've
    discovered a new particle,
  97. this eyebrow raise is about a four.
  98. (Laughter)
  99. I spent hours, days, weeks
    in secret meetings,
  100. arguing with my colleagues
    over this little bump,
  101. poking and prodding it with our most
    ruthless experimental sticks
  102. to see if it would withstand scrutiny.
  103. But even after months
    of working feverishly --
  104. sleeping in our offices
    and not going home,
  105. candy bars for dinner,
  106. coffee by the bucketful --
  107. physicists are machines
    for turning coffee into diagrams --
  108. (Laughter)
  109. This little bump would not go away.
  110. So after a few months,
  111. we presented our little bump to the world
    with a very clear message:
  112. this little bump is interesting
    but it's not definitive,
  113. so let's keep an eye on it
    as we take more data.
  114. So we were trying to be
    extremely cool about it.
  115. And the world ran with it anyway.
  116. The news loved it.
  117. People said it reminded
    them of the little bump
  118. that was shown on the way
    toward the Higgs boson discovery.
  119. Better than that,
    my theorist colleagues --
  120. I love my theorist colleagues --
  121. my theorist colleagues wrote
    500 papers about this little bump.
  122. (Laughter)
  123. The world of particle physics
    had been flipped on its head.
  124. But what was it about this particular bump
  125. that caused thousands of physicists
    to collectively lose their cool?
  126. This little bump was unique.
  127. This little bump indicated
  128. that we were seeing an unexpectedly
    large number of collisions
  129. whose debris consisted
    of only two photons,
  130. two particles of light.
  131. And that's rare.
  132. Particle collisions are not
    like automobile collisions.
  133. They have different rules.
  134. When two particles collide
    at almost the speed of light,
  135. the quantum world takes over.
  136. And in the quantum world,
  137. these two particles
    can briefly create a new particle
  138. that lives for a tiny fraction of a second
  139. before splitting into other particles
    that hit our detector.
  140. Imagine a car collision
    where the two cars vanish upon impact,
  141. a bicycle appears in their place --
  142. (Laughter)
  143. And then that bicycle explodes
    into two skateboards,
  144. which hit our detector.
  145. (Laughter)
  146. Hopefully, not literally.
  147. They're very expensive.
  148. Events where only two photons
    hit out detector are very rare.
  149. And because of the special
    quantum properties of photons,
  150. there's a very small number
    of possible new particles --
  151. these mythical bicycles --
  152. that can give birth to only two photons.
  153. But one of these options is huge,
  154. and it has to do with
    that long-standing question
  155. that bothered me as a tiny little kid,
  156. about gravity.
  157. Gravity may seem super strong to you,
  158. but it's actually crazily weak
    compared to the other forces of nature.
  159. I can briefly beat gravity when I jump,
  160. but I can't pick a proton out of my hand.
  161. The strength of gravity compared
    to the other forces of nature?
  162. It's 10 to the minus 39.
  163. That's a decimal with 39 zeros after it.
  164. Worse than that,
  165. all of the other known forces of nature
    are perfectly described
  166. by this thing we call the Standard Model,
  167. which is our current best description
    of nature at its smallest scales,
  168. and quite frankly,
  169. one of the most successful
    achievements of humankind --
  170. except for gravity, which is absent
    from the Standard Model.
  171. It's crazy.
  172. It's almost as though most
    of gravity has gone missing.
  173. We feel a little bit of it,
  174. but where's the rest of it?
  175. No one knows.
  176. But one theoretical explanation
    proposes a wild solution.
  177. You and I --
  178. even you in the back --
  179. we live in three dimensions of space.
  180. I hope that's a
    non-controversial statement.
  181. (Laughter)
  182. All of the known particles also live
    in three dimensions of space.
  183. In fact, a particle is just another name
  184. for an excitation
    in a three-dimensional field;
  185. a localized wobbling in space.
  186. More importantly, all the math
    that we use to describe all this stuff
  187. assumes that there are only
    three dimensions of space.
  188. But math is math, and we can play
    around with our math however we want.
  189. And people have been playing around
    with extra dimensions of space
  190. for a very long time,
  191. but it's always been an abstract
    mathematical concept.
  192. I mean, just look around you --
    you at the back, look around --
  193. there's clearly only
    three dimensions of space.
  194. But what if that's not true?
  195. What if the missing gravity is leaking
    into an extra-spatial dimension
  196. that's invisible to you and I?
  197. What if gravity is just as strong
    as the other forces
  198. if you were to view it in this
    extra-spatial dimension,
  199. and what you and I experience
    is a tiny slice of gravity
  200. make it seem very weak?
  201. If this were true,
  202. we would have to expand
    our Standard Model of particles
  203. to include an extra particle,
    a hyperdimensional particle of gravity,
  204. a special graviton that lives
    in extra-spatial dimensions.
  205. I see the looks on your faces.
  206. You should be asking me the question,
  207. "How in the world are we going to test
    this crazy, science fiction idea,
  208. stuck as we are in three dimensions?"
  209. The way we always do,
  210. by slamming together two protons --
  211. (Laughter)
  212. Hard enough that
    the collision reverberates
  213. into any extra-spatial dimensions
    that might be there,
  214. momentarily creating
    this hyperdimensional graviton
  215. that then snaps back
    into the three dimensions of the LHC
  216. and spits off two photons,
  217. two particles of light.
  218. And this hypothetical,
    extra-dimensional graviton
  219. is one of the only possible,
    hypothetical new particles
  220. that has the special quantum properties
  221. that could give birth to our little,
    two-photon bump.
  222. So, the possibility of explaining
    the mysteries of gravity
  223. and of discovering extra
    dimensions of space --
  224. perhaps now you get a sense
  225. as to why thousands of physics geeks
    collectively lost their cool
  226. over our little, two-photon bump.
  227. A discovery of this type
    would rewrite the textbooks.
  228. But remember,
  229. the message from us experimentalists
  230. that actually were doing
    this work at the time,
  231. was very clear:
  232. we need more data.
  233. With more data,
  234. the little bump will either turn into
    a nice, crisp Nobel Prize --
  235. (Laughter)
  236. Or the extra data will fill in
    the space around the bump
  237. and turn it into a nice, smooth line.
  238. So we took more data,
  239. and with five times the data,
    several months later,
  240. our little bump
  241. turned into a smooth line.
  242. The news reported on a "huge
    disappointment," on "faded hopes,"
  243. and on particle physicists "being sad."
  244. Given the tone of the coverage,
  245. you'd think that we had decided
    to shut down the LHC and go home.
  246. (Laughter)
  247. But that's not what we did.
  248. But why not?
  249. I mean, if I didn't discover
    a particle -- and I didn't --
  250. if I didn't discover a particle,
    why am I here talking to you?
  251. Why didn't I just hang my head in shame
  252. and go home?
  253. Particle physicists are explorers.
  254. And very much of what we do
    is cartography.
  255. Let me put it this way: forget
    about the LHC for a second.
  256. Imagine you are a space explorer
    arriving at a distant planet,
  257. searching for aliens.
  258. What is your first task?
  259. To immediately orbit the planet,
    land, take a quick look around
  260. for any big, obvious signs of life,
  261. and report back to home base.
  262. That's the stage we're at now.
  263. We took a first look at the LHC
  264. for any new, big,
    obvious-to-spot particles,
  265. and we can report that there are none.
  266. We saw a weird-looking alien bump
    on a distant mountain,
  267. but once we got closer,
    we saw it was a rock.
  268. But then what do we do?
    Do we just give up and fly away?
  269. Absolutely not;
  270. we would be terrible scientists if we did.
  271. No, we spend the next couple
    of decades exploring,
  272. mapping out the territory,
  273. sifting through the sand
    with a fine instrument,
  274. peeking under every stone,
  275. drilling under the surface.
  276. New particles can either
    show up immediately
  277. as big, obvious-to-spot bumps,
  278. or they can only reveal themselves
    after years of data taking.
  279. Humanity has just begun its exploration
    at the LHC at this big high energy,
  280. and we have much searching to do.
  281. But what if, even after 10 or 20 years,
    we still find no new particles?
  282. We build a bigger machine.
  283. (Laughter)
  284. We search at higher energies.
  285. We search at higher energies.
  286. Planning is already underway
    for a 100-kilometer tunnel
  287. that will collide particles
    at 10 times the energy of the LHC.
  288. We don't decide where
    nature places new particles.
  289. We only decide to keep exploring.
  290. But what if, even after
    a 100-kilometer tunnel
  291. or a 500-kilometer tunnel
  292. or a 10,000-kilometer
    collider floating in space
  293. between the Earth and the Moon,
  294. we still find no new particles?
  295. Then perhaps we're doing
    particle physics wrong.
  296. (Laughter)
  297. Perhaps we need to rethink things.
  298. Maybe we need more resources,
    technology, expertise
  299. than what we currently have.
  300. We already use artificial intelligence
    and machine learning techniques
  301. in parts of the LHC,
  302. but imagine designing
    a particle physics experiment
  303. using such sophisticated algorithms
  304. that it could teach itself to discover
    a hyperdimensional graviton.
  305. But what if?
  306. What if the ultimate question:
  307. What if even artificial intelligence
    can't help us answer our questions?
  308. What if these open questions,
    for centuries,
  309. are destined to be unanswered
    for the foreseeable future?
  310. What if the stuff that's bothered me
    since I was a little kid
  311. is destined to be unanswered
    in my lifetime?
  312. Then that ...
  313. will be even more fascinating.
  314. We will be forced to think
    in completely new ways.
  315. We'll have to go back to our assumptions,
  316. and determine if there was
    a flaw somewhere.
  317. And we'll need to encourage more people
    to join us in studying science
  318. since we need fresh eyes
    on these century-old problems.
  319. I don't have the answers,
    and I'm still searching for them.
  320. But someone -- maybe
    she's in school right now,
  321. maybe she's not even born yet --
  322. could eventually guide us to see physics
    in a completely new way,
  323. and to point out that perhaps
    we're just asking the wrong questions.
  324. Which would not be the end of physics,
  325. but a novel beginning.
  326. Thank you.
  327. (Applause)