Holometer: Holographic Noise

This summer I am working at [Fermi National Accelerator Laboratory](http://fnal.gov/) as a Teacher Research Associate as part of the [TRAC program](http://ed.fnal.gov/interns/programs/trac/). I plan on writing a series of posts about my experiences and, specifically, about the experiment with which I’m involved: [the holometer](http://holometer.fnal.gov/). Before describing my specific contributions to the experiment, I think I should start with the theory that led to holometer experiment. One of my goals this summer is to be able to explain this experiment and the theory that it is testing in a way that can be understood by my students. This will take several revisions and this post is my first draft.

The theorist involved with this experiment is [Craig Hogan](http://astro.fnal.gov/people/Hogan/) and the holometer is designed to test the the holographic principle. What is the holographic principle? Some describe this theory as claiming that the reality that we perceive is actually a three-dimensional projection from the two-dimensional reality at the edge of the universe. While that sounds cool and sci-fi, I have no idea what it means.

An analogy that I think helps explain the holographic principle is that of graphics on a computer screen. When you play Angry Birds, the bird flies across the screen in an apparently smooth path:

Angry Birds

However, if you zoom in and look more closely, you’ll see that the bird cannot follow an arbitrarily smooth path since the screen is made of pixels. As the bird flies across the screen, it must move in discrete intervals horizontally and vertically. That is, its location on the screen is quantized. What appears to be smooth movement, is actually the bird jumping from one pixel to the next. The minimum distance the bird can move is the width of one pixel. A pixel’s width is sufficiently small that we don’t notice these jumps as we play the game.


How does this analogy apply to the holographic principle? Space-time is the screen; we are the Angry Birds; and the Planck length is the width of a pixel. To elaborate, as we move through space-time, our movement is not perfectly smooth but, rather, jumpy because the smallest distance we can move is the Planck length (1.6 x 10-35 m)1. Similarly to how, if we zoom in on the computer screen, we can observe the jumpiness of the Angry Bird, through an analogous magnification we should be able to observe the jumpiness, or jitter, of our movement through space-time. This jitter is the focus of Hogan’s research and is called holographic noise. The holometer experiment is designed to measure this phenomenon. How can we build an apparatus that can measure this holographic noise when the Planck length is so incredibly small? Stay tuned for the next post in this series!

Does this make any sense? Feedback is most welcome!

This post is one in a series about The Holometer experiment and my work at Fermilab in the Summer of 2011:

* Holometer: Holographic Noise
* [Holometer: Interferometer](https://pedagoguepadawan.net/68/holometerinterferometer/)
* [Holometer: Spectral Analysis](https://pedagoguepadawan.net/81/holometerspectralanalysis/)
* [Holometer: Transverse Jitter](https://pedagoguepadawan.net/83/holometertransversejitter/)
* [Holometer: Correlated Interferometers](https://pedagoguepadawan.net/94/holometercorrelatedinterferometers/)
* [Holometer: Computer-Based Measurements](https://pedagoguepadawan.net/111/holometercomputerbasedmeasurements/)

1 The [Planck length](http://en.wikipedia.org/wiki/Planck_length) was derived from fundamental physical constants (speed of light, gravitational constant, and Planck constant) by Max Planck.

6 thoughts on “Holometer: Holographic Noise

  1. John Burk

    This is a great post—the connection to AB is an excellent one, and I remember when I took a course on computer graphs, how hard it was to draw a straight line across a grid of pixels. I’m looking forward to the rest of your posts and especially curious to know who the holometer can measure plank level jitters.

  2. Erwin van den Heuvel

    To my understanding the holographic principles states that the amount of information
    That can be stored in a part of space time is Proportional to the area of that piece of space time
    And not to its volume. What it means is indeed quite unclear but to my opinion it’s not well explained
    By just quantizing space in planck pixels. Recent results, I believe, indicate that if space is indeed quantised
    It’s much finer grained than the planck length.

    I would love to discuss about this with you!

    1. geoff Post author

      Your explanation sounds familiar. I think this is where the idea of the information stored in black holes being proportional to the surface area rather than the volume is related. I’m not sure yet of the connection between this and the Planck length. My limited understanding is that there is not consensus about the meaning of the results recently reported. I hope to have many of these questions answered next week when I will have the opportunity to meet with Craig Hogan.

  3. Kim

    Let me see: As I understand it, the core of the holographic principle is that the shortest distance anything can move is the Planck length (or a similarly small value). Therefore, continuous motion does not exist; everything must move in quantum jumps.
    This is a nice explanation. I think I understood it very well. Your writing style is friendly – I’m reminded of what-if.xkcd.
    I do have some questions, though. How does this work in the real world? It makes sense in one dimension, but in two, must we move in tiny increments in one of two directions on some arbitrary grid? Or can we move to any spot on a circle of a tiny radius? It only gets more complicated in three dimensions. Also, I’m having trouble making a connection between your pixel analogy and what others are saying about the two-dimensional nature of space-time.
    One more helpful addition to this post might be a comparison of the Planck length to something “familiar,” like the diameter of a proton or electron.
    I can’t wait to read about your experiment!


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