7 ms·

Surprising magnetic effect of light discovered at University of Michigan (2011)

116 points by Splendor 13y ago

ynniv 13y ago
It must feel good to discover something 8 orders of magnitude stronger than predicted.
mikeleung 13y ago
this is 2 years old
- Zircom 13y ago
  Thank you for helping those of us unable to do basic arithmetic.
kibwen 13y ago
Note that this from 2011. But it's still pretty cool when discoveries occur that weren't predicted by the models.
brisance 13y ago
Does this mean tractor beams can be made real? :)
- akiselev 13y ago
  They can already be made real. A) Make sure your ship is bigger B) Shoot a ton of highly charged electron beams at the enemy space ship to ionize their hull C) Magnetize your hull to the opposite charge and bring in the ship
  - tekromancr 13y ago
    How does one go about decelerating the other ship before it smashes into yours?
    - kaybe 13y ago
      Change your ship's charge so that it's the same as the pulled ship, maybe?
    - OnTheRocks 13y ago
      D) Magnetize your hull to the same charge and bring in the ship
      - tekromancr 13y ago
        The other ship would have momentum in the direction Of you. I suppose you could swap your hulls charge to repell
thornad 13y ago
Hardly surprising. Explanation here: http://www.youtube.com/watch?v=lpI6ikj1G-s http://www.youtube.com/watch?v=lpI6ikj1G-s
gailees 13y ago
How does Michigan consistently have such crazy research going on?
- mikeyouse 13y ago
  It's typically in the top 3 public US colleges and top 20 overall. The average SAT score coming in is 1900 with over 25% of their freshman class arriving with 4.0 GPAs out of high school. So they have a pretty good program by typical measures. Their advantage then over similar schools is the sheer size and funding. A school like Dartmouth probably has 'smarter' students enrolling on average, but Michigan's engineering college has more students (8,000+) than the entirety of Dartmouth (6,100). So take those 8,000 engineering students and add another 32,000 in the non-engineering tracks (many of whom are in sciences, medicine, mathematics, physics, etc.) and you're bound to produce some interesting research. So a ton of smart students, but then there's the money... U of M has the 8th largest endowment ($8 billion) in the US and the 2nd largest research budget at over $1.2 billion per year. They spent $190mm on engineering research last year and over $550mm in the medical school on health / biotech R&D. One could ask why they don't produce more than they do.
  - Locke1689 13y ago
    Realistically, the only things that matter that you mentioned are money (not the endowment, though, just the research budget, AKA grant money) and the facilities. Undergrads are basically worthless (in fact, they may be a detriment because they drain resources from the professors and the grad students).
methehack 13y ago
Does anyone know what happened with this? I googled "magnetic effects of light new type of solar cell" but I only got press from 2011 in the results.
- jpdoctor 13y ago
  The title of the paper is: Optically-induced charge separation and terahertz emission in unbiased dielectrics. The news release is completely out-to-lunch (eg "Light has electric and magnetic components. Until now, scientists thought the effects of the magnetic field were so weak that they could be ignored." Are you kidding? Light doesn't even propagate without the magnetic field) so I'd start by tracking citations of the original paper.
  - shardling 13y ago
    They meant that they thought magnetic effects were weaker than electric in this particular situation, not in general. It's just worded horrendously in the press release.
  - ctdonath 13y ago
    We know it's electromagnetic waves, but as it says we tend to ignore the latter part. Having just studied for (and passed! yay me!) my amateur radio license exam, I've been mulling over this common omission of consideration of propagating magnetics. Phase too: we're so focused on frequency that we overlook phase. Polarization is also underrated, with a study last year suggesting "infinite bandwidth" (so said news reports) when used creatively. Revisiting basics can reveal wonderous things.
    - simcop2387 13y ago
      If you take a look at how QAM works mathematically, it's getting such wonderful results because it's using two carriers with phase differences to do everything. It lets you do some really cool things depending on how well you can recover that phase.
dlhavema 13y ago
so were problems found with the tech so it was abandoned or what? hard to know where it's going if anywhere with no followup...
- akiselev 13y ago
  Welcome to academia.
selimthegrim 13y ago
They goofed, see the comments on their paper (http://prl.aps.org/abstract/PRL/v98/i9/e093901 http://prl.aps.org/abstract/PRL/v98/i9/e093901). namely http://scholar.google.com/scholar?cluster=16908965081581579446&hl=en&as_sdt=0,38 http://scholar.google.com/scholar?cluster=169089650815815794... and http://scholar.google.com/scholar?cluster=2747561718322596551&hl=en&as_sdt=0,38 http://scholar.google.com/scholar?cluster=274756171832259655...
- prawks 13y ago
  Prime example of why storing papers behind paywalls is a bad idea. I can't read anything linked. The authors then invoke Faraday's law H r E= i! 0 and conclude that the integral on the left side of Eq.(2) is identical to the first integral on the right. The theoretical result claimed in the Letter is directly predicated on this conclusion. This conclusion, however, is valid only ... Continued? where m (p) is the peak value of induced magnetic (electric) dipole moment and r (" r) is the ratio of magnetic (electric) permeability (permittivity) of the sphere and the surrounding medium at the given frequency. Equation (9) in [1] is a consequence of Eq.(8): JM º¿ 1= ...
  - selimthegrim 13y ago
    The bottom of the second link (first Google Scholar link) leads to a free copy of the comment from Kent State University's website.
  - pavel_lishin 13y ago
    This rendered very oddly in Chrome on OS X: http://i.imgur.com/xFiNhav.png http://i.imgur.com/xFiNhav.png
    - gus_massa 13y ago
      PDF of first comment: http://muri.lci.kent.edu/Publications/Papers_KSU/PPM_PRL99_2007.pdf http://muri.lci.kent.edu/Publications/Papers_KSU/PPM_PRL99_2... The strange symbols appear because LaTeX use strange fonts with strange encodings, so the formulas look nice in the pdf but if you cut and paste them, and use a standard font to render the symbols then they are mapped to random characters in the standard fonts.
gboudrias 13y ago
I emailed the author of the paper. Hope he gets back to us, this is cool.
mdturnerphys 13y ago
"The light . . . must be focused to an intensity of 10 million watts per square centimeter. Sunlight isn't this intense on its own . . ." Just a bit of an understatement.
- ctdonath 13y ago
  Start with full-on solar intensity of 1000 watts per square meter. 100x100 meters gives the power input needed. Focus that on 1m^2, then focus that in turn to 1cm^2. Sounds doable.
  - bcbrown 13y ago
    It's not that simple. There's a minimum beam size, and passive optics won't let you alter that. https://en.wikipedia.org/wiki/Gaussian_beam#Beam_width_or_spot_size https://en.wikipedia.org/wiki/Gaussian_beam#Beam_width_or_sp...
- VladRussian2 13y ago
  at 10MWt/cm2 how long the exposure is before the material melts/evaporates?

116 points by Splendor 13y ago

ynniv 13y ago

It must feel good to discover something 8 orders of magnitude stronger than predicted.

mikeleung 13y ago

this is 2 years old

Zircom 13y ago
Thank you for helping those of us unable to do basic arithmetic.

kibwen 13y ago

Note that this from 2011. But it's still pretty cool when discoveries occur that weren't predicted by the models.

brisance 13y ago

Does this mean tractor beams can be made real? :)

akiselev 13y ago
They can already be made real. A) Make sure your ship is bigger B) Shoot a ton of highly charged electron beams at the enemy space ship to ionize their hull C) Magnetize your hull to the opposite charge and bring in the ship
- tekromancr 13y ago
  How does one go about decelerating the other ship before it smashes into yours?
  - kaybe 13y ago
    Change your ship's charge so that it's the same as the pulled ship, maybe?
  - OnTheRocks 13y ago
    D) Magnetize your hull to the same charge and bring in the ship
    - tekromancr 13y ago
      The other ship would have momentum in the direction Of you. I suppose you could swap your hulls charge to repell

thornad 13y ago

Hardly surprising. Explanation here: http://www.youtube.com/watch?v=lpI6ikj1G-s http://www.youtube.com/watch?v=lpI6ikj1G-s

gailees 13y ago

How does Michigan consistently have such crazy research going on?

mikeyouse 13y ago
It's typically in the top 3 public US colleges and top 20 overall. The average SAT score coming in is 1900 with over 25% of their freshman class arriving with 4.0 GPAs out of high school. So they have a pretty good program by typical measures. Their advantage then over similar schools is the sheer size and funding. A school like Dartmouth probably has 'smarter' students enrolling on average, but Michigan's engineering college has more students (8,000+) than the entirety of Dartmouth (6,100). So take those 8,000 engineering students and add another 32,000 in the non-engineering tracks (many of whom are in sciences, medicine, mathematics, physics, etc.) and you're bound to produce some interesting research. So a ton of smart students, but then there's the money... U of M has the 8th largest endowment ($8 billion) in the US and the 2nd largest research budget at over $1.2 billion per year. They spent $190mm on engineering research last year and over $550mm in the medical school on health / biotech R&D. One could ask why they don't produce more than they do.
- Locke1689 13y ago
  Realistically, the only things that matter that you mentioned are money (not the endowment, though, just the research budget, AKA grant money) and the facilities. Undergrads are basically worthless (in fact, they may be a detriment because they drain resources from the professors and the grad students).

methehack 13y ago

Does anyone know what happened with this? I googled "magnetic effects of light new type of solar cell" but I only got press from 2011 in the results.

jpdoctor 13y ago
The title of the paper is: Optically-induced charge separation and terahertz emission in unbiased dielectrics. The news release is completely out-to-lunch (eg "Light has electric and magnetic components. Until now, scientists thought the effects of the magnetic field were so weak that they could be ignored." Are you kidding? Light doesn't even propagate without the magnetic field) so I'd start by tracking citations of the original paper.
- shardling 13y ago
  They meant that they thought magnetic effects were weaker than electric in this particular situation, not in general. It's just worded horrendously in the press release.
- ctdonath 13y ago
  We know it's electromagnetic waves, but as it says we tend to ignore the latter part. Having just studied for (and passed! yay me!) my amateur radio license exam, I've been mulling over this common omission of consideration of propagating magnetics. Phase too: we're so focused on frequency that we overlook phase. Polarization is also underrated, with a study last year suggesting "infinite bandwidth" (so said news reports) when used creatively. Revisiting basics can reveal wonderous things.
  - simcop2387 13y ago
    If you take a look at how QAM works mathematically, it's getting such wonderful results because it's using two carriers with phase differences to do everything. It lets you do some really cool things depending on how well you can recover that phase.

dlhavema 13y ago

so were problems found with the tech so it was abandoned or what? hard to know where it's going if anywhere with no followup...

akiselev 13y ago
Welcome to academia.

selimthegrim 13y ago

They goofed, see the comments on their paper (http://prl.aps.org/abstract/PRL/v98/i9/e093901 http://prl.aps.org/abstract/PRL/v98/i9/e093901). namely http://scholar.google.com/scholar?cluster=16908965081581579446&hl=en&as_sdt=0,38 http://scholar.google.com/scholar?cluster=169089650815815794... and http://scholar.google.com/scholar?cluster=2747561718322596551&hl=en&as_sdt=0,38 http://scholar.google.com/scholar?cluster=274756171832259655...

prawks 13y ago
Prime example of why storing papers behind paywalls is a bad idea. I can't read anything linked. The authors then invoke Faraday's law H r E= i! 0 and conclude that the integral on the left side of Eq.(2) is identical to the first integral on the right. The theoretical result claimed in the Letter is directly predicated on this conclusion. This conclusion, however, is valid only ... Continued? where m (p) is the peak value of induced magnetic (electric) dipole moment and r (" r) is the ratio of magnetic (electric) permeability (permittivity) of the sphere and the surrounding medium at the given frequency. Equation (9) in [1] is a consequence of Eq.(8): JM º¿ 1= ...
- selimthegrim 13y ago
  The bottom of the second link (first Google Scholar link) leads to a free copy of the comment from Kent State University's website.
- pavel_lishin 13y ago
  This rendered very oddly in Chrome on OS X: http://i.imgur.com/xFiNhav.png http://i.imgur.com/xFiNhav.png
  - gus_massa 13y ago
    PDF of first comment: http://muri.lci.kent.edu/Publications/Papers_KSU/PPM_PRL99_2007.pdf http://muri.lci.kent.edu/Publications/Papers_KSU/PPM_PRL99_2... The strange symbols appear because LaTeX use strange fonts with strange encodings, so the formulas look nice in the pdf but if you cut and paste them, and use a standard font to render the symbols then they are mapped to random characters in the standard fonts.

gboudrias 13y ago

I emailed the author of the paper. Hope he gets back to us, this is cool.

mdturnerphys 13y ago

"The light . . . must be focused to an intensity of 10 million watts per square centimeter. Sunlight isn't this intense on its own . . ." Just a bit of an understatement.

ctdonath 13y ago
Start with full-on solar intensity of 1000 watts per square meter. 100x100 meters gives the power input needed. Focus that on 1m^2, then focus that in turn to 1cm^2. Sounds doable.
- bcbrown 13y ago
  It's not that simple. There's a minimum beam size, and passive optics won't let you alter that. https://en.wikipedia.org/wiki/Gaussian_beam#Beam_width_or_spot_size https://en.wikipedia.org/wiki/Gaussian_beam#Beam_width_or_sp...
VladRussian2 13y ago
at 10MWt/cm2 how long the exposure is before the material melts/evaporates?