Monday, November 07, 2011

What are natural units?

I noticed that I confused some readers by referring to temperatures in GeV and distances as the inverse of an energy. 15 years ago, when I first learned about natural units, it seemed really fishy to me. Now Stefan has to remind me on occasion that a second is not a distance, and an entropy is not dimensionless. Since I've experimented lately with some new software, I put together a few slides on the use of natural units and youtubed them.



At 3:20min it should be 5000K, not 500K, sorry about that. At 3:30min, Lara tried to eat the keyboard.
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13 comments:

  1. Uncle Al10:16 AM, November 07, 2011

    "temperatures in GeV and distances as the inverse of an energy."

    Spectroscopists use cm^(-1). Non-SI units fit magnitude to task and are easy to check for trivial errors. Nobody grasps kg/m^3 for density. Sieverts, grays... try evading Fukishima truth with curies. A $billion NASA Mars mission failed in space because idiot management mixed Imperial and metric units. Do the job, verify it, then dress it up in formal attire. Check that, too.

    Teething keyboards! Yer gonna be temps in GeV rich!

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  2. Anonymous11:41 AM, November 07, 2011

    Thanks, Bee. This is much appreciated. :-)

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  3. GMP1:19 PM, November 07, 2011

    This was fun! :-)

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  4. PlatoHagel12:29 AM, November 08, 2011

    Hi Bee,

    Appreciated the Youtube....good job. Also enjoyed the little one in the background.:)

    Since I've experimented lately with some new software,

    What were you using?

    Best,

    ReplyDelete
  5. Sabine Hossenfelder12:43 AM, November 08, 2011

    Hi Navneethc,

    Well, you were not the first one to ask, so I thought I'll make this once and then I can link to it whenever needed. Sorry I was so unfriendly when you asked. Best,

    B.

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  6. Sabine Hossenfelder12:50 AM, November 08, 2011

    Hi Plato,

    I made the slides with Powerpoint. They have much improved the equation editor. One can also record the audio with Powerpoint and set a timing for the text to appear. You can then export it as some windows movie or so. I imported that movie with with Corel's Videostudio, edited it somewhat and exported as mpg. It was really straight forward. I first tried to make it all with the Videostudio, but the equations I would have to either write by hand or include as an image, so I would have needed another software anyway. Best,

    B.

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  7. Giotis2:32 AM, November 08, 2011

    Nice and nice voice too...

    What about the dimensions of a field? A scalar field or a spinor field for example. You could include these too.

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  8. Sabine Hossenfelder3:15 AM, November 08, 2011

    Hi Giotis,

    Excellent question :o) I first wanted to include derivatives, fields, mass dimensions of operators etc. But then it got too long and also more technical. Maybe I make a follow-up video at some point. Best,

    B.

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  9. Phil Warnell6:46 AM, November 09, 2011

    Hi Bee,

    Certainly a clear explanation regarding natural units as one is brought to understand they allow for examination of the qualifiers without need of being distracted by the quantifiers and thus how can anyone not consider qualities as something objectively analyzable. It’s also nice to discover that Lara is so interested to as to be literally cutting the teeth on it.

    Best,

    Phil


    P.S. So very nice to hear from you.

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  10. Sabine Hossenfelder11:55 AM, November 09, 2011

    Hi Phil,

    Glad you liked it. The dimensional estimates is something that we weren't taught in any of our classes, yet it is so vital to physics, it is difficult for me to see how to do without it. Best,

    B.

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  11. Neil Bates8:19 PM, November 09, 2011

    This comment has been removed by the author.

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  12. Neil Bates8:28 PM, November 09, 2011

    Cool, first time to hear your voice, Bee. Note that the program of converting to completely natural units of the Planck scale need not always use G. The natural charge is constructed from h and c (and is inexplicably around 11.7 times actual charge quantum e.)

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  13. Sabine Hossenfelder1:02 AM, November 10, 2011

    Hi Neil,

    Planck units go farther than natural units by omitting even the mass scale. Eg in natural units, the Schwarzschildradius is 2M/m_p^2. In Planck units it's 2M. Planck Units are frequently used in the gr-qc community and I find them terribly confusing. Best,

    B.

    ReplyDelete

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