back to article Physicists send supersonic shock waves rippling through a lab

Scientists have managed to create powerful supersonic shock waves – comparable to those generated in space – under laboratory conditions. Shock waves are important in the universe. They drive cosmic rays and spread supernova particles close to the speed of light, kickstarting several physical phenomena such as the Aurora …

  1. John Smith 19 Gold badge
    Thumb Up

    Excellent work.

    M12 work typically involves using shock tubes, giving such flows for less << 1 sec.

    This is intriguing given the very low densities of the gases and plasma involved. In the universe these phenomena cover huge volumes of space so being able to model them in more detail, (like how they grow, what can make them shrink etc) should improve our understanding quite a lot.

  2. Philip Stott

    The Weibel instability ... is that where they wobble but never fall down?

    1. Mr_Pitiful

      The Weibel instability

      <Eyes Wet>

      Oh shit, I'm old enough to recall the adverts from TV in the UK

      Please don't tell anyone!

      </Eyes Wet>

      1. John Brown (no body) Silver badge

        Re: The Weibel instability

        Weebles wobble but they don't fall down

        Yes, also old enough!

      2. Anonymous Coward
        Anonymous Coward

        Re: The Weibel instability

        > Oh shit, I'm old enough to recall the adverts from TV in the UK

        I remember Alberto Balsam - and his Amazing Animal Band.

        1. Anonymous Custard Silver badge

          Re: The Weibel instability

          You'll be recalling the Cadbury's Smash robots next...

  3. allthecoolshortnamesweretaken

    "But the most energetic shocks occur outside of the solar system, making them difficult to study."

    And I'm very much okay with them occurring at a safe distance from our rock, thank you very much.

    Pint is for the boffins; good work.

  4. drewsup

    not to be pedantic, but..

    in the lab, with air, ok to use mach as a speed, but i feel this is strange to use in space as mach is speed through a substance, ( in our case,air). Just seems funny...

    1. Yet Another Anonymous coward Silver badge

      Re: not to be pedantic, but..

      It only applies in a cloud where you can have a shock wave - so think of it as very very low pressure atmosphere.

      In the same way that the speed of sound drops at altitude the example has shocks in space with speeds near the speed of light but only mach 4.

      1. Anonymous Coward
        Anonymous Coward

        Re: not to be pedantic, but..

        In the same way that the speed of sound drops at altitude the example has shocks in space with speeds near the speed of light but only mach 4.

        Does this mean that in space, somebody *can* hear you scream after all?

    2. elDog

      Re: not to be pedantic, but..

      My thoughts, eggsactly.

      What is the mach value in some other media such as water, earth, wind, and fire?

      How about that ethereal ether that we are all supposedly enclosed within? Is it related to the good vibes?

    3. the Jim bloke Silver badge

      Re: not to be pedantic, but..

      First thing I noticed was the splash image.

      "Artist's impression of a shock wave"


      Speed of sound would vary with atmospheric density - so not even the same from sea level to randomly chosen mountain top.

      In terms of relevance its equivalent to cubits per lunchbreak, or double decker buses per long weekend - although that can be a measure of frequency as well as velocity - which makes it more versatile as a standard.

      So using it is an arbitrary term to help explain things to idiots....

      --> icon

      1. Chris G Silver badge

        Re: not to be pedantic, but..

        "Artist's impression of a shock wave"

        I may need to see a psychologist but that impression looks like an enflamed sphincter to me.

        What was the artist thinking?

        I am still wrestling with sonic boom in space, shirley that means the source of the shock wave is moving faster than the wave front?

    4. Anonymous Coward
      Anonymous Coward

      Re: not to be pedantic, but..

      As near as I can work out, the density of air is about 2.4 x 10e19 atoms per cubic centimeter. For comparison, an example of density in space might be that of the solar wind, at perhaps 3-6 ions per cubic centimeter (compare to an estimated "average" density of the interstellar medium of 1 atom / cc). So solar wind, and indeed the interstellar medium, are substances --- just highly rarefied ones.

      Talking about Mach numbers in a plasma makes as much sense as talking about temperature of a plasma (a measure of the kinetic energy of the atoms in a material).

  5. Your alien overlord - fear me

    Yeah, I've done that. Passing wind after a curry night sends shock waves throughout my office !!!

  6. HildyJ Silver badge

    A new unit of measure

    El Reg should measure supersonic shock waves in units of TrumpTweets (TT).

    1. This post has been deleted by its author

  7. Anonymous Coward
  8. Pen-y-gors Silver badge


    Can't be much fun working in the next lab to these bods - mini sonic booms all day. Hope they're not doing sleep research or similar.

  9. james 68

    High Mach?

    Surely it should have been "Big Mach".

    An obvious if relevant unit of measurement for plasma/particle velocity (not to be confused with Big Macs, the unit of measurement for American waistlines).

    1. Meph

      Re: High Mach?

      "not to be confused with Big Macs, the unit of measurement for American waistlines"

      Would that be similar to the "Big Mach Beth" being a unit of measurement for the volume and quality of a cooked Scottish breakfast?

      Okay, okay, I'm going.

      1. Solarflare

        Re: High Mach?

        I believe proper etiquette dictactes that you have to refer to it as the "Big Scottish Play"

  10. Farnet

    Mach Numbers

    Am I missing something here..

    Mach is the speed of sound through a medium, and as far as I'm aware the medium here is still air so that would make it 767mph.

    So 1,000,000mph would equate to 1300+ Mach?

    1. Farnet

      Re: Mach Numbers

      If you are going to thumbs down me, please explain what I have done wrong with my "off the top of my head" calculations.

      I never said my calculations are absolute, and if I'm wrong I would be interested to know where I made the error.

      1. james 68

        Re: Mach Numbers

        Well I'm not the one who downvoted you - but I will answer your question (Knowledge after all should be shared and downvoting someone instead of explaining why they're wrong is just crass).

        The speed of sound varies not only due to the medium (air, nitrogen, helium, you get the idea) but also due to the pressure and density of that medium. Near the ground on Earth for example, air is more dense meaning sound travels more slowly, 5 miles up it is less dense meaning sound travels more quickly. (the sound wave needs less energy to 'move' the less dense medium meaning it can travel more quickly). Even the temperature of the medium changes the speed of sound as a cooler medium is more dense and a hotter medium is less dense.

        Given this, in space (which is not a complete vacuum) the speed of sound can be many, many times faster than the speed of sound at any height within Earths atmosphere.

        Strangely the opposite is true for the speed of sound in liquids and solids, the more dense the liquid or solid, the faster sound travels.

        1. Farnet

          Re: Mach Numbers

          Thanks James for that,

          I appreciated about the different densities, heat and mediums.... it didn't click the opposite would happen in such an extreme with a partial (or almost complete) vacuum.

          Sitting back and thinking about it does make sense. I'm a budding scientist and dabble in everything I can find and also always aware of my ignorance and always keen to correct it and form a firm(er) understanding.

          So pfhhht to the Thumbs down brigade.

  11. Zmodem

    i did that 10 years ago with my EM drive, now BAE Systems are rocking half the speed of light with skylon 8 and the eurofighter 2

    still using the general basics of ring magnets, and compress them to increase the retracting force to get alot more power while using the same amounf of power

    turning them off/on like a maglev train for propulsion

    1. Anonymous Coward
      Anonymous Coward

      I'll have one of whatever he's having.

      Clearly very strong stuff.

POST COMMENT House rules

Not a member of The Register? Create a new account here.

  • Enter your comment

  • Add an icon

Anonymous cowards cannot choose their icon

Biting the hand that feeds IT © 1998–2020