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Ep. 28, Page 18
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Comic 2068 - Ep. 28, Page 18

27th Jan 2016, 9:26 PM in Episode 28 :: Save My Place | Load My Place
Average Rating: 5 (2 votes)

Author Notes:

smbhax 27th Jan 2016, 9:26 PM edit delete
Stephen Hawking, the guy who actually did write the book on black holes, is giving two lectures through the BBC's Reith Lectures series, and the BBC has a transcript of the first one (the second is next week), which is all about...black holes! : )

It's a good distillation of our understand of black holes as it has evolved over the past century. One thing I didn't know is that prior to John Wheeler's introduction of the term "black hole" in 1967, they were known as "frozen stars."

And that term is still in use—but for something else! Wikipedia says (this is their Frozen star article in its entirety):

In astronomy, a Frozen star, besides a disused term for a black hole, is a hypothetical type of star that, according to the astronomers Fred Adams and Gregory P. Laughlin, may appear in the future of the Universe when the metallicity of the interstellar medium is several times the solar value.

Due to opacity effects, as metallicity of the interstellar gas increases both the maximum and minimum masses a star can have will decrease. For the latter case, it's expected that an object with a mass of 0.04 solar masses (40 times the mass of Jupiter), that currently would become a brown dwarf unable to fuse hydrogen, could do so ending in the main sequence with a surface temperature of 0 °C (273 K, thus frozen), much cooler than the dimmest red dwarfs of today, and water ice clouds forming in its atmosphere. The luminosity of these objects would be more than a thousand times smaller than the faintest stars currently existing and their lifetimes would be also sensibly longer.

Adams and Laughlin's research paper the article refers to, A Dying Universe: The Long Term Fate and Evolution of Astrophysical Objects, makes for a pretty interesting read! There's a lot of math—which I mostly can't follow : P—but they still predict a lot of things in fairly straight English; for instance, talking about the eventual fate of the stars in our galaxy (which by this advanced future time, somewhere around 10 septillion (10 with 25 zeroes after it) years after the beginning of the universe (if I got that right...), consist pretty much of half brown dwarfs and half white dwarfs (the vast majority of the mass being in the white dwarfs), with a sprinkling of neutron stars and black holes) and its central supermassive black hole, Sgr A*, they write: "we expect ~ 1 - 10% of the stars to fall to the central black hole and the remainder to be evaporated [into intergalactic space]; the final mass of the central black hole will thus be [1 to 10 billion solar masses.]"

Far beyond the fate of the galaxy, protons themselves will decay; this will lead to white dwarf stars, which last a very very long time, losing their super-dense degenerate matter and plumping up into cold balls of neutral hydrogen of approximately Jupiter size and density. That mass continues to dwindle away until the star is no longer really a star, but merely a 1 meter "rock-like object," which is the ultimate end point of its evolution. : o

After the stars go, even huge black holes that form from the naked supermassive black holes in a very old galactic cluster joining together will eventually evaporate via Hawking radiation, ie quantum particles fizzing away at the edge of their event horizon. So, in the far far far future, " a large fraction of the universe will be in the form of radiation, electrons, positrons, and other decay products."

The paper was written (1996) before more precise measurements led scientists to conclude that the universe appears to be "open"—that is, it will continue to expand forever—so it spends a lot of time exploring scenarios of what would happen if the universe is "closed" (doomed to collapse) or "flat" (static, I guess). It talks about exotic things that would form, like electrons and their antiparticles, positrons, forming into unstable atoms called positronium (any atom of a particle and its antiparticle is an "-onium"), although not much of this would happen in an open universe.

Of the fate of the open universe, they point out that we may simply be in an open "bubble" in a large universe than we can observe, that could itself later reverse and collapse; there is even the possibility that the universe is in a false vacuum state—which is to say that a lower energy state than our current vacuum exists—and could spontaneously switch to the true vacuum state via quantum tunneling, in which case known physical laws could change, or the universe could even in effect be destroyed and remade as something wholly different.

That's getting a little far out, though; far more likely is that it will just keep expanding, and matter and energy as we know it will all end up as "mostly photons of colossal wavelength, neutrinos, electrons, and positrons." I suppose that sounds a little depressing, but they do point out that "the seeming poverty of this distant epoch is perhaps more due to the difficulties inherent in extrapolating far enough into the future, rather than an actual dearth of physical processes."


Speaking of difficulties, I was so out of it today that I forgot to push the "Start Streaming" button before painting today's page—so if you were waiting around for my Twitch stream to come back online, sorry about that, I screwed up and didn't actually record it!


moizmad 28th Jan 2016, 11:32 AM edit delete reply
Good, that way our beers will keep nice and cold!
smbhax 28th Jan 2016, 7:57 PM edit delete reply
cattservant 28th Jan 2016, 3:11 PM edit delete reply
But who backs up the back up?
smbhax 28th Jan 2016, 7:57 PM edit delete reply
The guards with their flashlights, I guess : o