back to article Galileo in spaaace: France's 'equivalence principle' satellite

Earlier this week, France's snappily-named "Micro-Satellite à traînée Compensée pour l'Observation du Principe d'Equivalence", aka Microscope, rode a Soyuz lifter to orbit on a mission to " test the equivalence principle, which postulates the equality between gravitational mass and inertial mass". Legend has it that in around …

  1. alferdpacker

    "Microsoft's Payload Block" sounds more like a well known bug/feature than part of a satellite.

    1. Anonymous Coward
      Anonymous Coward

      Typo, surely?

      Microscope's payload block? Microsoft isn't mentioned in the text

      1. Mark 85 Silver badge

        Re: Typo, surely?

        Let's give Mr. Packer a break. He's probably hungry and mis-read things.

  2. Hans Neeson-Bumpsadese


    So, Galileo's theories form one of the foundations of physics? That's quite an achievement for someone who was just a poor boy from a poor family.

    1. Lars Silver badge

      Re: Magnifico!

      Just goes to show that educating "a poor boy from a poor family" can be worth it. (Can you hear me Americans).

    2. This post has been deleted by its author

      1. FrogsAndChips

        Re: any way the wind blows

        Obviously, Freddie didn't take into account the solar wind: "ensure the satellite is kept stable against [...] the solar pressure forces due to photon impacts"

    3. Anonymous Coward
      Anonymous Coward

      Re: Magnifico!

      It wasn't too much work. You know, easy come easy go.

    4. Joefish

      Re: Magnifico!

      It would be great if there was found to be a variation. I'd hate to think there's no escape from reality.

      1. Lester Haines (Written by Reg staff) Gold badge

        Re: Re: Magnifico!

        Well for the possible answer, open your eyes, look up to the skies and see...

        1. DropBear

          Re: Magnifico!

 what was the launch vehicle thinking on its way up? "I've got to break free...?"

      2. FrogsAndChips

        Re: Magnifico!

        @joefish: as long as you're ready to leave all behind and face the truth...

  3. This post has been deleted by its author

  4. Doctor Syntax Silver badge

    "all objects ... should fall at the same speed"

    Exhibit the same acceleration?

  5. Stratman

    Hairnet but no beardnet?


    "The experiment was invalidated by some alphabetti spaghetti discovered in the chamber"

  6. captain veg Silver badge


    If you went to the top of the leaning tower of Pisa and dropped two spheres of different weight over the edge, you would be arrested on terrorism charges.


    1. Gordon 10 Silver badge

      Re: apparently

      Didn't the Church waterboard Galileo for heresy?

    2. Jan 0 Silver badge

      Re: apparently

      > you would be arrested on terrorism charges.

      Thankfully, Italy isn't americanized* to that extent yet.

      *(<pedant>US americanized</pedant>.)

  7. Daniele Procida

    No experimentation required

    "Galileo's suspicion was that all objects (in the same gravitational field) should fall at the same speed, irrespective of their mass, and he was eventually able to conclude that in a vacuum this would indeed be indeed be the case."

    It wasn't really a suspicion that required observation to confirm or confute. It was based on reasoning alone, based on what would happen if a lighter (supposedly slower-falling) object were connected to a heavier (supposedly faster-falling) object.

    The lighter object would retard the fall of the heavier object, so the speed of the pair would be a bit slower than that of the heavier. Yet by the same principle, the two connected objects would now constitute a single heavier object, so would be faster than both.

    It's clearly impossible for both conclusions to be true, so the principle ("heavier objects fall faster") that leads us to them can't possibly be true.

    1. TobyD

      Re: No experimentation required

      But... As far as I can remember from school, the mutual attraction of two masses has the mass of both as factors. -G(m1m2)/r^2

      So... Technically a "heavier" (larger mass) object would be pulled towards the Earth with a larger force than a smaller mass, yes?

      1. Major N

        Re: No experimentation required

        Technically, no, since what you would be doing would be accelerating the earth towards the second mass, although this would lead to a larger combinrded.velocity. also, if the mass was large enough to exhibit this in any meaningful way, you'd have a much bigger problem on your hands, that I'm not sure even Bruce Willis could save us from with nukes...

      2. Doctor Syntax Silver badge

        Re: No experimentation required

        "So... Technically a "heavier" (larger mass) object would be pulled towards the Earth with a larger force than a smaller mass, yes?"


        But the theory goes on to say that the inertia of the heavier mass is also greater and needs a larger force to experience the same acceleration as the smaller mass with its smaller force and smaller inertia. According to theory the difference in inertia exactly counters the increase in force, hence the large and small mass have the same acceleration. But is the theory true? So far all experiments have produced results consistent with the theory. The purpose of this experiment is to see if the theory holds with a more sensitive method.

      3. Anonymous Coward
        Anonymous Coward

        Re: No experimentation required


        Just as it should: F=ma (as I think someone might have pointed out before)

        1. Jos V

          Re: No experimentation required

          Yes, quite. As we have F=m.a, and "a" (in this case g) is constant (for objects at the same height, and the same place*), F/m always is a constant.

          So am I correct that they are trying to find if v(t)=v(0)+a.t, or substituted like v(t)=v(0)+(F/m).t is not holding at the extremes of mass (either way) where it becomes v(t)=v(0)+c.(F/m).t, where they would now have to find out where c is coming from?

          *as we know that gravity is inversely proportional to distance from earth, composure of the mass it's moving over, etc.

    2. This post has been deleted by its author

  8. Joe Werner Silver badge

    Force is not acceleration....

    Force is mass times acceleration. While the force is smaller for a lighter object (correctly remembered), the inertia that has to be overcome is also smaller by the same amount. The mass of the accelerated small (compared to earth) object cancels out on both sides of the equation. This means the acceleration is the same for a heavy and a light object. The equivalence of heavy mass (causing the pull) and inert (correct word?) mass to be accelerated is the question we need to test here.

    That's what I gather from this after a few pints...

    Mine's the one with the slide rule

    1. DropBear

      Re: Force is not acceleration....

      Well, if we are studying a heavier and a lighter body in the Earth's gravitational field, then it's already a three-body problem, and one should not attempt to tackle problems that don't even have analytical solutions on a Friday afternoon!

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