Cosmic Queries: The Random Edition

Credit: Ben Ratner.

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About This Episode

It’s time for another episode of Cosmic Queries, where your own personal astrophysicist Neil deGrasse Tyson answers, sight unseen, fan submitted questions chosen by his co-host. This week, Chuck Nice asks Neil questions on a wide variety of topics that we couldn’t answer in other episodes, from alien plant life, to colonizing Mars, to whether velocity could be considered a dimension. You’ll find out if the constellations would look different when seen from Saturn, whether there’s a north pole to our universe, and why astronomers got the Milky Way’s north pole wrong in the first place. Discover why a stable black hole can’t exist inside a star, and how the expansion of our Sun will affect the Earth. You’ll learn how scientists knew to leave gaps in the periodic table of the elements, and why the moon is spiraling away from the Earth at 5 inches a year. Neil speculates on what the bright spot on the dwarf planet Ceres might be, whether we’ll explore Jupiter’s moon Europa in our lifetimes, and if we’ll find life in its subsurface ocean. You’ll also hear how NASA inventions led to grooved highway pavement and safer, cheaper LASIK surgery. On the lighter side, Neil and Chuck talk about Neil’s famous vests, the Ship of the Imagination from COSMOS: A Spacetime Odyssey, YouTube’s famous “Double Rainbow Guy,” and the wrestling move Neil always wanted to invent which he calls the “Double Tidal Lock.”

NOTE: All-Access subscribers can listen to this entire episode commercial-free here: Cosmic Queries: The Random Edition.

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  • jackkessler

    Since the moon is receding at 5 inches a year, why can’t we project backward to when it was closer and closer to earth until it and earth were touching or even parts of the same body. That is how we derive the Big Bang from current expansion. Why not the moon-earth system as well? It seems a far less cumbersome and unlikely scenario than the Thea notion. If there was a Thea why would it have struck the earth exactly on the equator to produce a moon orbit within a few degrees of the ecliptic? What are the chances of that happening?

    • starfyre

      We can project backward to find the moon 17 times closer than it is now, earth’s rotation at 6 hours, and tides hundreds of feet high going
      inland for many miles, all contributing to stirring up the “soup” needed to get life and evolution started. And, yes, the probability of the “perfect strike” is indeed low, and I think that seriously reduces the odds of finding the right conditions for life elsewhere. Without that collision, earth would be smaller, lose it’s atmosphere like Mars did, and there would not be a larger iron core to produce the magnetic field that wards off the deadly solar rays. So it’s not enough to be in the “Goldilocks” zone with water, you gotta have whole lot of improbable luck on your side as well.

      • jackkessler

        Why only 17 times?

  • Chris Hankins

    whats the song at 20 mins in just before the break ends ?

  • starfyre

    Thank you for your excellent reply and info. I can’t escape a nagging feeling that I read somewhere that, amazingly, the moon coalesced in only a hundred years or so. Maybe, maybe not.

  • MusicFiend

    Great #Throwback to April. I had missed this one. I love Cosmic Quries

  • jackkessler

    @lizzyjessie If the earth and moon were once parts of the same body that would explain the similarity in composition between their crusts, would it not?

    My understanding of the Roche Limit is that it is the nearest a moon can be to its planet without being torn to pieces by tidal forces. The familiar example is the rings of Saturn. Saturn has a number of large moons, all of which are further than the Roche Limit. It also has a number of large rings all of which are closer than the Roche Limit.

    Which suggests that the rubble from the supposed Earth – Theia collision that was closer than the Roche limit would form rings which would eventually decay and fall to earth. Only material further than the Roche Limit could coalesce into the moon.

    Since the moon would have to have formed further away than the Roche limit to have formed at all, the material it would have to have formed from would have been distributed over quite a large volume of space. That material so widely and thinly distributed in space could coalesce into the moon in a few centuries strains credulity. And it would have to have formed one and only one body from material initially randomly distributed over an enormous volume of space.

    We see from other planets that multiple moon in roughly concentric orbits are stable indefinitely. How only one body should have formed from the supposed Earth – Theia collision debris is hard to fathom.

    That the collision should have been within a few degrees of the ecliptic in the vast volume of space is also hard to believe. If it were anywhere else the angular momentum would have put the moon in an orbit highly inclined to the ecliptic. Lots of evidence can be lost in a violent collision but angular momentum does not go away.

    I have a strong feeling that the Theia hypothesis is proposed not because it is indicated by evidence but because so many other theories have been contradicted by evidence. It seems to be asserted only because there is not yet evidence proving it wrong in spite of its inherent unlikeliness. That is not much of a basis for a positive assertion that it is right.

    The Theia hypothesis is an act of desperation, not of analysis of evidence.

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