Solid Helium: Why No Images? | Feynman Lectures Vol.1

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    Helium Pictures Solid
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Discussion Overview

The discussion revolves around the phenomenon of solid helium, particularly its formation under high pressure and low temperature conditions, as mentioned in the Feynman Lectures Vol.1. Participants explore the availability of images depicting solid helium and the challenges associated with capturing such images in laboratory settings.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant expresses curiosity about the lack of images of solid helium and questions whether it can only be produced in lab conditions and in small amounts.
  • Another participant emphasizes that the inability to find images online does not imply their non-existence and points out that solid helium can only be produced under specific laboratory conditions, such as temperatures around 2K and pressures of 25 bar.
  • A different participant notes that solid helium requires significant pressure to solidify, mentioning that at room temperature, the pressure exceeds 100 kbar, reinforcing the idea that solid helium is not found outside of laboratory environments.
  • One participant shares a link to an image of solid helium and mentions the difficulty in photographing solid helium due to the small difference in refractive indices between solid and liquid helium.
  • Another participant observes an anomaly in the solidification process of helium depicted in an image, questioning whether they are interpreting the crystallization correctly.
  • A participant explains that the observed "drops" are solid helium surrounded by liquid helium, and describes the transitions in crystal shape that occur as temperature decreases.
  • One participant acknowledges their initial lack of depth in questioning and expresses gratitude for the clarifications provided by others, while also inquiring about the existence of larger samples of solid helium.

Areas of Agreement / Disagreement

Participants generally agree that solid helium can only be produced in laboratory conditions due to the extreme pressures and low temperatures required. However, there is no consensus on the specifics of the crystallization process or the interpretation of the images shared.

Contextual Notes

Participants mention the challenges of capturing images of solid helium and the specific conditions required for its formation, indicating limitations in observational capabilities and the dependence on experimental setups.

tridianprime
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I was not sure exactly where to put this but it involves images so I thought it was no too inappropriate here.

I was reading the Feynman Lectures Vol.1 and he says that Helium, although not solid at absolute zero normally, can be so in high pressures. I then googled this for images but none turned up. Why is this? Can it only be done in lab conditions? Is it only done in small amounts?

Thanks, it is just a light query but I am interested to know why.
 
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A few points.
  • Before asking us why something should be so, you should find out if it should be so.
  • The fact that you can't find something on Google in a few minutes does not mean it does not exist.
  • If you Google "Solid Helium" you get the image below, which is, not surprisingly, a picture of solid helium.
  • Of course it can only be produced in the lab. Where on Earth would you naturally find temperatures of 2K and pressures of 25 bar? And what difference does it make? Cameras work in the lab too.

F2.small.gif
 
As Vanadium 50 already pointed out, even in the zero temperature limit helium requires about 25 bar pressure to solidify. At room temperature the pressure is over 100 kbar. So we cannot observe solid helium outside laboratory conditions.

I've always liked these images of solid helium:

http://www.lps.ens.fr/~balibar/photo.crist.jpg

BTW photographing solid helium is not easy, since the difference in the refractive indices of solid and liquid He is quite small.

Here are some nice videos of growing solid He etc:

http://www.lps.ens.fr/~balibar/indexang.html#A few videos
 
In QuasiParticle's image: http://www.lps.ens.fr/~balibar/photo.crist.jpg, the Helium drop seems to solidify from 1.4K to 0.5K, but from 0.5 to 0.1k it appears to be fusing again.. not crystallising.. the one in the 0.5K picture appears to be a perfect crystal. Why this anomaly? Or am I observing it wrong?
 
All those "drops" are solid helium, surrounded by liquid He. As the temperature is lowered, solid He goes through various transitions in the crystal shape. It forms smooth surfaces, facets, with particular surface orientations.
 
Oh I get it now. Thanks.
 
Vanadium 50 said:
A few points.
  • Before asking us why something should be so, you should find out if it should be so.
  • The fact that you can't find something on Google in a few minutes does not mean it does not exist.
  • If you Google "Solid Helium" you get the image below, which is, not surprisingly, a picture of solid helium.
  • Of course it can only be produced in the lab. Where on Earth would you naturally find temperatures of 2K and pressures of 25 bar? And what difference does it make? Cameras work in the lab too.

F2.small.gif

Thanks for you response. I apologise for not being in depth in my post and for sounding naive. I will try to amend this in the future and bear your points in mind. I did find those images but I was wondering if there were any larger samples of solid helium, that sounds ridiculous sorry. In hindsight, the question was 'troubled' at best so I appreciate the tips. I was not exactly sure what I meant and I tried to explain it in the best way I could. All of your answers have clarified it though.
 

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