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We just had our first interstellar visitor...and it's weird.

2018-11-30 · explainer · Hank · 10:17 · watch on YouTube

Topic: Science & nature · mode: Personal essay · tags: timely hook, civic or action cta, calendar ritual

Hank lays out what is known about Oumuamua, the first observed interstellar object, weighs the comet against the alien solar-sail hypothesis, and argues that because he wants it to be a spaceship he cannot trust himself on it: the universe being weird is perhaps the best argument against aliens.

What is said

The parts of the video and what is said in each (★ — how much it matters to the video).

00:00:00 — What is known about Oumuamua: speed, shape, brightness, velocity change, comet versus solar sail, Spitzer and Pan-STARRS data

  • ★★★ Hank says a little over a year ago we first observed an object from another star system: pieces of other systems can visit us, and Oumuamua is not what we expected. — 00:00:05
  • ★★★ Hank says Oumuamua entered the solar system at about 25 km per second and varied tenfold in brightness, suggesting a long, skinny, tumbling shape. — 00:00:33
  • ★★★ Hank says Oumuamua has a length-to-width ratio of 10 to 1, while barely any solar-system objects reach 5 to 1. — 00:01:03
  • ★★★ Hank says it passed surprisingly close to Earth into the sun's habitable zone, and its velocity changed in ways gravitation alone cannot explain. — 00:01:03 · Earth
  • ★★★ Hank says there are only two explanations: a comet that off-gassed 10% of its mass, or a 50-meter square of shiny foil under a millimeter thick, a solar sail. (hedged) — 00:01:32
  • ★★ Hank explains that photons have no mass but do have momentum, so a big reflective, lightweight sheet can use them for propulsion, which humans have experimented with. — 00:02:01
  • ★★ Hank says a comet is obviously more likely, but before the velocity change Oumuamua seemed not to be one: a long skinny shape needs rigidity, and loose comets would break apart. — 00:02:01
  • ★★ Hank says the brightness change might instead come from one side being much darker, like Saturn's moon Iapetus, so the shape may not be so weird. (hedged) — 00:02:32
  • ★★ Hank says it was also thought not to be a comet because it had no tail, though comet-like objects from other systems might out-gas differently and be harder to detect. — 00:02:32
  • ★★ Hank says scientists think off-gassing would have changed the object's rotation, which it appears not to have done. — 00:03:02
  • ★★★ Hank says the Spitzer Space Telescope detected no infrared from it, so it probably reflected most of the sun's heat: it must be shinier than solar-system asteroids or comets. (hedged) — 00:03:31
  • ★★★ Hank says the Pan-STARRS whole-sky survey caught it, past peak brightness, in its first 10 years, implying such objects are probably common, though models of solar-system formation say they should not be. (hedged) — 00:03:56
  • ★★ Hank says that if such objects are natural and common, the models were off by orders of magnitude, which is wonderful news because there will be more chances to study them. — 00:04:26
  • ★★★ Hank says jumping from 'this is confusing and weird' to 'it's aliens' has tended to be a bad way to answer questions. — 00:04:26

00:04:56 — Arguments against an alien light sail (tumbling, slow), the wreckage idea and Hank's own 'greeting card' conjecture

  • ★★★ Hank cites Carl Sagan: extraordinary claims require extraordinary evidence, which we do not have and never will as Oumuamua speeds away. — 00:04:56

    “extraordinary claims require extraordinary evidence”

  • ★★ Hank says one argument against an alien-made light sail is the tumbling: a probe meant to study a planet would be kept stable to point instruments. (hedged) — 00:04:56

  • ★★ Hank says the second argument is speed: 25 km per second is slow for interstellar travel, about 12,000 years to Alpha Centauri. — 00:05:26
  • ★★ Hank rejects the idea that it is dead wreckage of a broken or attacked craft: unless such events are rare, that debris would have to be far too common. — 00:05:55
  • ★★ Hank offers his own conjecture: maybe it tumbles slowly because its senders wanted it seen and chased, an interstellar greeting card going unreceived. (hypothetical, speculative) — 00:05:55

00:06:35 — Credibility, wanting it to be a spaceship, distrusting himself, the coming telescope, and the universe being weird

  • ★★ Hank retracts: he shouldn't have said that, it was pure conjecture, and he probably shouldn't even be making this video. — 00:06:35
  • ★★ Hank says that as a science-show host with a master's degree who looks like this, he is credible, and wants to keep and use that credibility wisely. (playful) — 00:06:35 · SciShow
  • ★★★ Hank says an interstellar object is huge news on its own, meaning such objects are commoner and weirder than thought, but the captivating story would be that someone else made it. — 00:06:35
  • ★★★ Hank says how captivating an idea is should not affect how scientists weigh it, but it does shape how we perceive it: headlines, videos and what we click. — 00:07:04 · sensationalism
  • ★★ As a science communicator, Hank knows raising the alien hypothesis will draw people to that part of the story over the other explanations; readers see 'probably' more than 'is not'. — 00:07:33 · sensationalism
  • ★★ Hank admits he wants it to be a spaceship: he wants a new story, a big-news event everyone remembers. — 00:07:33
  • ★★★ Hank says he cannot trust himself on this one, and tries to see more things that way: some things he can't trust himself with because he wants them a certain way. — 00:08:02
  • ★★ Hank says only one telescope could currently have spotted Oumuamua; another, orders of magnitude better, comes online in a few years. — 00:08:31
  • ★★ Hank says if the new telescope sees such objects often, we may identify a new class of object to study and even visit; if they are rare, we saw something special. (hedged) — 00:08:31
  • ★★★ Hank says maybe the best argument against the alien hypothesis is that the universe is weird: unexplained sights were often taken for 'the others' until science caught up. (hedged) — 00:08:58

00:09:24 — Sources, thanks to scientists, the four-minute-rule exemption and the P4A video call

  • ★ Hank notes that educational videos are exempt from the four-minute rule, and thanks the exemption for letting him ramble. (playful) — 00:09:24 · Four-minute rule
  • ★★★ Hank says the Project for Awesome is next weekend and asks viewers thinking of making a video for their charity to get it ready; the community will vote on Foundation grants. — 00:09:53 · Project for Awesome, Foundation to Decrease World Suck

In the description and comments

  • ★★★ The description says that sometimes accepting a lack of knowledge is far more valuable than conjecture, but Oumuamua is very weird regardless. — video description
  • ★★ The description recommends sources Hank used: Rob Reid's Ars Technica piece and its companion podcast, and PBS Space Time on Oumuamua. — video description
  • ★★ The description also points to Bad Astronomy and Scientific American on Oumuamua, an overview of how it was discovered, and the published paper arguing that a solar sail could explain the observations. — video description

Threads in this video

Mentioned

Central: comet · extraterrestrial life · solar sail · ʻOumuamua

Also: People: Carl Sagan

Projects: Foundation to Decrease World Suck · Project for Awesome · SciShow

Rituals: Four-minute rule

Concepts: motivated reasoning · photon · Sagan standard · science fiction · sensationalism · Telescope · wonder (emotion)

Places: Alpha Centauri · Earth · Iapetus · Saturn · Solar System · Sun (star)

Products: Pan-STARRS · Spitzer Space Telescope

Only in the description or credits: Ars Technica · Bad Astronomy · Intellectual humility · PBS Space Time · Rob Reid · Scientific American

Also centred on extraterrestrial life: Where are the Space Aliens?! · They Say it Gets Colder · Aliens · Is it Good or Bad that we Haven't Met Aliens? · Fine, I'll Talk About the Drones… · This Might Actually be Happening

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