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Crookes Radiometer

Updated on April 22, 2014
BlossomSB profile image

Bronwen and her family have enjoyed collecting many things, including fans, clocks, books and shells.

What is inside?
What is inside? | Source

What is it?

Among my grandfather's things I found an interesting black tube. It seemed familiar, as if I had seen it before; perhaps he had shown it to me when I was a small child. I was intrigued. What was it?

On the lid there was an address. He had begun to send it to himself and got as far as 'Mr. Thom' but had then changed the name to one I did not know. More mystery.

I opened the tube and found something made of glass that was obviously quite fragile.

It's made of glass and looks fragile
It's made of glass and looks fragile | Source

The Mystery Continued

I took it out. Oh, yes! I remembered him showing me this. In a dull light the little metal sails were still, but in the sunlight they began to move. Interesting.

I wondered why he had bought it. Was it a novelty to show friends, or did it have a purpose. I did not know and returned it to its tube and onto the top shelf of the wardrobe. Long ago I showed it to my children; later to my grandchildren.

Recently I needed my printer fixed and there on the counter was a small glass globe that was obviously similar to mine, except that it was shaped more like an electric light globe and it was a single one. Beside it was a card: Crookes Radiometer.

Crookes Radometer

There was quite a bit about it on the web:

  • it was referred to as a 'strange apparatus.' I knew that!
  • if you shine a light on it, the tiny plates revolve. I knew that, too.

I thought it was probably from the later 1800s, as that was when Grandfather migrated. He married in 1889, so probably bought it before then.

I also thought it would have been forgotten in this age of computers and advanced technology, but no! It remains a novelty.

In 2008 it was featured as 'Le radiomètre de Crookes' at a Fête de la Science in the Village des Sciences at the Université de Nice. Très interessant! So it was connected with the discipline of physics. There was more.

The upper globe showing the decorative knob.
The upper globe showing the decorative knob. | Source

Experimental Science

The following description of a radiometer is taken from a book, 'Experimental Science' by George M. Hopkins published in 1889:

The radiometer is a heat engine of remarkable delicacy as well as great simplicity. It illustrates a class of phenomena discovered by Crookes which are difficult to explain in a brief and popular way. The instrument consists of a very slight spider of aluminium supporting on the end of each of its four arms a very thin mica plate blackened on one side and silvered on the other. The aluminium spider is provided with a jewel, which rests upon a delicate needle point supported at the center of the glass globe. The spider is retained on its pivot by a small tube extending downward from the top of the globe. When placed in sunlight or near a gas or lamp flame, the vanes revolve rapidly. An alum cell interposed between the radiometer and the source of light and heat allows the light to pass, but intercepts the heat rays. Under these conditions the vane will not rotate. An iodine cell, which is opaque to light, when arranged in the same way allows the heat rays to go through, and these cause the rotation of the vane.

The lower globe showing the lamp black
The lower globe showing the lamp black | Source

Lamp Black

On looking more closely at my radiometer, I discovered that the vanes were covered with lamp black on one side and over the years some had flaked off; tiny fragments were scattered inside the globe. That the lamp black would have been better than black paint, as it would absorb the light better. However, I don't think that the one at the print shop has lamp black, perhaps it has a non-glossy more modern paint.

According to the 1889 article, the instrument also needs heat to make it work. I tried putting my hands on it, but it did not move, so it needs the light as well.

Did you know about Crookes radiometer?

See results

Sir William Crookes

  • The inventor was English physicist Sir William Crookes, 1832-1919. Eldest of sixteen children, he attended the Royal College of Chemistry in London. Later he was meteorologist, lecturer, independent researcher, author of academic papers, was involved in many areas of physics and chemistry and received both public and academic honours. He married and had four children.
  • He founded the science journal, Chemical News.
  • Discovered the element thallium.
  • Was pioneer of vacuum tubes.
  • Invented the Crookes tube.
  • Invented Crookes radiometer.
  • 1895: Identified the first known sample of helium.
  • 1897: Was knighted.
  • Investigated radioactivity, achieving separation of uranium-X from uranium.
  • 1909: Wrote a book on diamonds.
  • 1910: Received the Order of Merit.

Crookes' Radiometer
Crookes' Radiometer | Source


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    • BlossomSB profile image

      Bronwen Scott-Branagan 2 years ago from Victoria, Australia

      GusTheRedneck: Thank you, that's interesting information. Thank you for translating the Dutch, too. I was about to delete it. I know a little Dutch but not enough to understand the comment.

      Adriano: Veel Dank.

    • GusTheRedneck profile image

      Gustave Kilthau 2 years ago from USA

      Hi Bronwen (Blossom SB on HubPages) -

      I remember watching one of these radiometers in action in a shop window back when I was a youngster. It may be of interest to remember that the "Crookes Tube" was the gadget that Roentgen was playing with when he "discovered" X-Rays.

      As commenter, Adriano, pointed out in the above comment, the radiometer worked (in part) because the radiometer glass envelope had been evacuated of air. That was also true for the "Crookes Tube" in its using electricity (electron bombardment) to generate those mysterious penetrating photons that Roentgen termed "X-Rays."


    • profile image

      Adriano 3 years ago

      Juist, heeft met warmte en rcelfetie the maken. En ook het feit dat er een lage luchtdruk in de bol is.De zon is er vandaag, je kan het ding testen.

    • BlossomSB profile image

      Bronwen Scott-Branagan 3 years ago from Victoria, Australia

      midget38: It is intriguing and it used to fascinate me as a child. Thank you for your comment.

      csmiravite-blogs: Yes, I was surprised when I looked on the internet and found that they could still be purchased, but they are interesting. So glad you enjoyed reading about it. Thanks.

    • csmiravite-blogs profile image

      Consolacion Miravite 3 years ago from Philippines

      Interesting! First time I've heard of it. I am surprised that such a thing exist. Nice hub! I enjoyed reading it! Thumbs up! :)


    • midget38 profile image

      Michelle Liew 3 years ago from Singapore

      Intriguing! Lesser known but a cool object!! What fun!

    • BlossomSB profile image

      Bronwen Scott-Branagan 3 years ago from Victoria, Australia

      Dim Flaxenwick: It's fun to share such an interesting object. Yes, I just looked at the vote and was surprised to find that result as there seems to be quite a bit on the internet about it. Thank you for your comment.

    • Dim Flaxenwick profile image

      Dim Flaxenwick 3 years ago from Great Britain

      How fascinating to find something so unusual in your possession.

      It's great that you took the time to share it with us.

      I noticed by the vote that most people had never heard of this.

    • BlossomSB profile image

      Bronwen Scott-Branagan 4 years ago from Victoria, Australia

      aviannovice: Did you? How lovely! Do you still have it? I find mine fascinating, even now. Thank you for your comment.

    • aviannovice profile image

      Deb Hirt 4 years ago from Stillwater, OK

      I had one of these as a kid, that was given to me by my father. It was the most fascinating possession that I ever had.

    • BlossomSB profile image

      Bronwen Scott-Branagan 4 years ago from Victoria, Australia

      Vellur: I'm so glad that you found it interesting, as I do, too. Thank you.

      LadyFiddler: It's fun to write, the problem is to find the time! I'm well and truly retired, so there should be plenty of time, but it just seems to vanish! Thank you for your good wishes and may God bless you, too.

    • LadyFiddler profile image

      Joanna Chandler 4 years ago from On planet Earth

      INTERESTING thanks Blossom for taking the time to write this for us :)

      Hope you are having a swelled week.

      God Bless You

    • Vellur profile image

      Nithya Venkat 4 years ago from Dubai

      Very interesting! It is really cool!! Enjoyed reading.

    • BlossomSB profile image

      Bronwen Scott-Branagan 4 years ago from Victoria, Australia

      teaches12345: It is fun to watch, in fact it can be a great time-waster! Thank you for your comments, it's good to hear from you.

    • teaches12345 profile image

      Dianna Mendez 4 years ago

      Thank you for the introduction to this novel item. I would love to see it in person. How fascinating it would be to watch.

    • BlossomSB profile image

      Bronwen Scott-Branagan 4 years ago from Victoria, Australia

      I was delighted to find out about it, as I've had it for a very long time, but I did not have a name for it before, so I couldn't find out anything about it. Now I know. I hope you're have a lovely weekend. Mine is cold and wet, as we get closer to winter. My little dog refused to go further than the end of the street this morning. She hates the rain - should have been a cat!

    • Eiddwen profile image

      Eiddwen 4 years ago from Wales

      How very interesting Blossom.

      Thanks for sharing and wishing you a wonderful weekend.


    • BlossomSB profile image

      Bronwen Scott-Branagan 4 years ago from Victoria, Australia

      jhamann: Lovely! Thanks Jamie.

      chef-de-jour: Yes, it was such fun finding out about it and its clever inventor. They were indeed intrepid, although I guess people now are still the same only in different fields.

    • chef-de-jour profile image

      Andrew Spacey 4 years ago from Near Huddersfield, West Yorkshire,UK

      Fascinating discovery! Crookes the scientist must have been one of those intrepid Victorian chaps forever pioneering. And he obviously inspired your grandfather. Thank you for the write up. Glad you solved the mystery!

    • jhamann profile image

      Jamie Lee Hamann 4 years ago from Reno NV

      Great hub BlossomSB I love it!! Jamie

    • BlossomSB profile image

      Bronwen Scott-Branagan 4 years ago from Victoria, Australia

      FlourishAnyway: It really does fascinate me, and yes, so often things that are left are broken and can't be repaired. Thank you for your comment.

    • FlourishAnyway profile image

      FlourishAnyway 4 years ago from USA

      What a fascinating piece of history! How fortunate you are to have been left this and have it remain intact.

    • BlossomSB profile image

      Bronwen Scott-Branagan 4 years ago from Victoria, Australia

      Jackie Lynnley: It is fun. I've just given a granddaughter my mother's 'writing desk.' It is like a box with a lock and tiny key. Inside there's a rest for writing letters, containers for envelopes, a glass ink bottle with a brass lid and a leather lid lining, a polished wood ruler with one concave side - she was surprised that there was a ruler with no inches or centimetres on it, some old coins and photos, a box of different sized nibs and a box of tiny paper fasteners. It was also one of my 'treasures' and I know that it will now be hers, too.

    • Jackie Lynnley profile image

      Jackie Lynnley 4 years ago from The Beautiful South

      Such a fun share, thank you so much. I love treasure hunts for the unusual and this reminded me of one! ^

    • BlossomSB profile image

      Bronwen Scott-Branagan 4 years ago from Victoria, Australia

      Frank Atanacio: It's an interesting and entertaining instrument .. and thank you for your comment.

      sujaya venkatesh: Thank you.

    • sujaya venkatesh profile image

      sujaya venkatesh 4 years ago

      nice share blo

    • Frank Atanacio profile image

      Frank Atanacio 4 years ago from Shelton

      educational. interesting and an entertaining hub blossoms..thank you for sharing

    • BlossomSB profile image

      Bronwen Scott-Branagan 4 years ago from Victoria, Australia

      always exploring: I'm not sure it's worth a lot monetarily, but you're right, it is priceless for me. It's lovely to share with you and thank you for your comments.

    • always exploring profile image

      Ruby Jean Richert 4 years ago from Southern Illinois

      This is very interesting. I would say that it's priceless. Thank's for sharing with us.

    • BlossomSB profile image

      Bronwen Scott-Branagan 4 years ago from Victoria, Australia

      Ericdierker: Glad you enjoyed it.

      MsDora: Yes, he really did, and it's so much fun learning about things that are really outside my normal ken. Thank you.

      pstraubie48: They are treasure, and great fun. It's good to have vintage things like this to be able to share. Thank you for the angels.

      Genna East: I was never very good with things like maths, physics and Chem., but fortunately that hasn't deterred some of my children. The only problem will be who to give it to!

      Audrey Howitt: Yes, I love rummaging around and finding things I'd forgotten about. I think I should have been born a bower bird.

      travmaj: It is intriguing and now I know more about it, I'll be able to share that information with my children and grandchildren, too.

    • travmaj profile image

      travmaj 4 years ago from australia

      What a wonderful piece of history your grandfather left you and how intriguing as you investigate. Most interesting and I'm sure there's much more to discover.

    • AudreyHowitt profile image

      Audrey Howitt 4 years ago from California

      Well this was a very cool find and a wonderful gift to you!

    • Genna East profile image

      Genna East 4 years ago from Massachusetts, USA

      I agree with Dora...what a wonderful heritage you have shared with us. Very interesting. :-)

    • pstraubie48 profile image

      Patricia Scott 4 years ago from sunny Florida

      How cool is that.....finding things like this is a treasure trove of memories and information and investigation waiting to unfold.

      So glad you have it to share.

      Angels are on the way to you ps

    • MsDora profile image

      Dora Weithers 4 years ago from The Caribbean

      Now this is what I call heritage. Your grandfather left you a piece of himself. From that radiometer, you have learned some history, some science, some culture and you are able to share it. Awesome!

    • Ericdierker profile image

      Eric Dierker 4 years ago from Spring Valley, CA. U.S.A.

      Very interesting, thank you.


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