Re: Guest Post - Irreversibility

1

That's such a short paper. How did it count for his tenure file?


Posted by: Moby Hick | Link to this comment | 06-25-15 5:51 AM
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What if there are coherently converging waves but they killed the dinosaurs?


Posted by: Moby Hick | Link to this comment | 06-25-15 6:15 AM
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A coherently converging wave (OK, a shock really) is what I'm going to be trying to create come August 1st. By "I" I mean a big team of people most of whom are smarter than I. The fun part is that I'll be committed to 250% of full time due to working on 3 separate grants. August through December (first major deliverable milestone) is going to be interesting.


Posted by: togolosh | Link to this comment | 06-25-15 7:00 AM
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I am contractually obligated to recommend my friend's book about symmetry in this thread. I mean, it's also very good. It has a great chapter on Emmy Noether, because you're a feminist.


Posted by: k-sky | Link to this comment | 06-25-15 7:48 AM
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3: you're building a bomb? https://en.wikipedia.org/wiki/Nuclear_weapon_design#Implosion-type_weapon


Posted by: ajay | Link to this comment | 06-25-15 7:57 AM
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5 was exactly my first thought.


Posted by: nattarGcM ttaM | Link to this comment | 06-25-15 8:01 AM
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3. Taylor's blast wave paper is amazing. Reading his work or Chandrasekhar or Landau or Kolmogorov is something else.
http://www3.nd.edu/~powers/ame.90931/taylor.blast.wave.I.pdf

Good luck with the fusion, any great-grandchildren will thank you.

When I was still in physics, I got the advice to read papers by pre-computer thinkers that failed to rtesolve the problem they approached in order to get a useful identification and framing of analytically intractable problems that would benefit from numerical approaches.


Posted by: lw | Link to this comment | 06-25-15 8:30 AM
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I am a bear of very little brain and I lose the plot here:

While Einstein thought that the irreversibility of radiation processes could be explained probabilistically

How does such an explanation work? Can you point me at something that will clarify it for me?


Posted by: chris y | Link to this comment | 06-25-15 9:02 AM
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5-7 Coincidentally I was just reading this fascinating post on Alex Wellerstein's great blog the other day (got there from this tweet of his showing Von Neuman's diagrams of the reflection from the blast wave.


Posted by: Barry Freed | Link to this comment | 06-25-15 9:29 AM
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3: It does make a big bang and occasionally bits of the lab get damaged, so sort of. I had fun doing blast damage calculations for the vacuum vessel.


Posted by: togolosh | Link to this comment | 06-25-15 9:36 AM
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9: sort of related. In 1947 some photographs of the first atomic bomb detonation at Los Alamos were published in Life magazine. From the pictures, one can read off the radius of the shock wave as a function of time. From this one can estimate the yield of the blast, which was of course highly classified.

This is used as a homework problem in this book.


Posted by: AcademicLurker | Link to this comment | 06-25-15 10:03 AM
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8. Most of reversible classical physics describes a continuum, smooth indivisible stuff, often time-reversibly as with the wave equation. The continuum is a mathematically convenient fiction. In fact, a small number of particles move coherently to originate an outbound wave. A very large number of particles far from each other would have to cooperate in order to produce an inbound one. This cooperation is improbable.

When we use the convenient continuum description, the apparent reversibility that results is an illusion, present in the description but almost never the underlying physical system. Maybe take fragile reversible counterexamples and consider how they differ from typical physical situations.

Not sure if this helps, hope so.


Posted by: lw | Link to this comment | 06-25-15 12:01 PM
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I can't help but read this as a subtle commentary on today's Supreme Court ACA ruling.

Perhaps too subtle.


Posted by: DaveLMA | Link to this comment | 06-25-15 4:51 PM
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12. Thanks, very helpful.


Posted by: chris y | Link to this comment | 06-26-15 2:24 AM
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Also, I'm impressed by the mature debate in comments at your link.


Posted by: chris y | Link to this comment | 06-26-15 2:28 AM
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Assuming that I am right about what togolosh is building, this is particularly unsettling:

The fun part is that I'll be committed to 250% of full time due to working on 3 separate grants.

Iran, Saudi Arabia, North Korea? Iran, North Korea, Facebook? Iran, Facebook, Texas?

And this is even more unsettling:
August through December (first major deliverable milestone) is going to be interesting.

Must remember to be upwind of major metropolitan areas over the Christmas holiday.


Posted by: ajay | Link to this comment | 06-26-15 3:28 AM
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"Deliverable" in this context is especially worrying.


Posted by: Alex | Link to this comment | 06-26-15 3:39 AM
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Quite. Castle Bravo, rather than Ivy Mike.


Posted by: ajay | Link to this comment | 06-26-15 3:51 AM
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We must encourage togolosh to liveblog the delivery. (Presidentially might be a good idea.)


Posted by: torrey pine | Link to this comment | 06-26-15 6:34 AM
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19 Should I evacuate Arrakis?


Posted by: Barry Freed | Link to this comment | 06-26-15 6:43 AM
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Also, which of togolosh's clients only hired him part-time? Cheapskates.


Posted by: torrey pine | Link to this comment | 06-26-15 6:48 AM
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Because he was part time, togolosh figured he could skip the targeting mechanism. The client would find out soon enough.


Posted by: Alex | Link to this comment | 06-26-15 7:21 AM
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That said it would be hilarious if someone from unfogged got a fusion reactor working. "'Sup?" "Not much. Fusin'" "rly?" "yeah, ignition was so last week" "


Posted by: Alex | Link to this comment | 06-26-15 7:23 AM
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16: Unfortunately I don't do anything as dramatic as that. It would be fun to make something like the Tsar Bomba, though. What I do is Magneto-Inertial Confinement . There's some funny politics around the name, since the guys who are furthest along want to call it Magnetized Target Fusion, which everyone else thinks sounds a little too much like a weapon. They are also the ones who most heavily edit the relevant Wikipedia pages.


Posted by: togolosh | Link to this comment | 06-26-15 8:01 AM
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