Friday's science question for spindizzy Page 2

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  • Dirtbox 1 Feb 2013 11:21:54 78,135 posts
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    If light had mass, it wouldn't travel at the speed of light.

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  • sport 1 Feb 2013 11:24:18 12,710 posts
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    Dirtbox wrote:
    If light had mass, it wouldn't travel at the speed of light.
    So you're saying that if mass had light, it couldn't travel at the speed of mass?
  • Dirtbox 1 Feb 2013 11:27:06 78,135 posts
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    Well it definitely wouldn't be as light any more.

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  • Fake_Blood 1 Feb 2013 11:28:59 4,206 posts
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    Then how do you explain the bending of light by gravity?
  • Dirtbox 1 Feb 2013 11:30:12 78,135 posts
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    Energy bends gravity as well. And time.

    Do you mean with black holes? Light travels through space and space is bent by mass, amoungst other things.

    Edited by Dirtbox at 11:31:53 01-02-2013

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  • MrTomFTW Moderator 1 Feb 2013 11:32:58 38,132 posts
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    Light is always moving, therefore generating energy, therefore mass, therefore you wouldn't divide by 0?

    Follow me on Twitter: @MrTom
    Voted by the community "Best mod" 2011, 2012 and 2013.

  • Dirtbox 1 Feb 2013 11:33:48 78,135 posts
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    Who's dividing by zero now? If you're talking about E=MC^2, that's multiplying.

    Photons are the product of energy and have 0 mass.

    Edited by Dirtbox at 11:40:08 01-02-2013

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  • Salaman 1 Feb 2013 11:37:01 19,036 posts
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    LeoliansBro wrote:
    Less than spindizzy, which is why I made this thread :)
    It'd be helpful if he'd come in here and clear a few things up actually. All the armchair physicists are muddying the waters somewhat in his continued absence.

    I can't believe he's giving CERN priority over EG like this.
  • MrTomFTW Moderator 1 Feb 2013 11:39:26 38,132 posts
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    @Dirtbox LB is. Last sentence of his follow-up question.

    Follow me on Twitter: @MrTom
    Voted by the community "Best mod" 2011, 2012 and 2013.

  • LeoliansBro 1 Feb 2013 11:42:41 44,141 posts
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    Yeah DB, sorry. k=h/(mv). The 'm' is zero, therefore the wavelength 'k' is ... unknowable?

    LB, you really are a massive geek.

  • Dirtbox 1 Feb 2013 11:49:35 78,135 posts
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    I believe you're getting it a bit backward. Light is considered the extreme at one end of the spectrum and all else is measured by it in that equation. You wouldn't use De Broglie to calculate light's wavelength, you'd involve shit like Planck's constant and other giggery pokery that I don't really know enough about to sound knowledgeable.

    Edited by Dirtbox at 11:50:40 01-02-2013

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  • LeoliansBro 1 Feb 2013 11:56:19 44,141 posts
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    Ah, fair enough!

    LB, you really are a massive geek.

  • Fake_Blood 1 Feb 2013 12:23:30 4,206 posts
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    Dirtbox wrote:
    Energy bends gravity as well. And time.

    Do you mean with black holes? Light travels through space and space is bent by mass, amoungst other things.
    No I meant that photons interact with the gravitational field.
    They would'nt if they had no mass.
    You are probably mistaken because you once read that in order to accelerate any mass to the speed of light it would require infinite energy.
    Photons don't accelerate.
  • Dirtbox 1 Feb 2013 12:32:17 78,135 posts
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    Heh, what? What makes you think photons don't accelerate and what difference does it make?

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  • grey_matters 1 Feb 2013 12:40:51 3,729 posts
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    You have to be careful when talking about "mass" under relativistic conditions.
    Light has mass because it has energy. Energy and mass are equivalent from E=mc^2 (a coiled spring therefore weighs a tiny tiny bit more than the same spring uncoiled). It has no "rest mass" though.
  • Fake_Blood 1 Feb 2013 12:44:50 4,206 posts
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    I'm just trying to understand why you think that photons have no mass.
  • Dirtbox 1 Feb 2013 12:46:02 78,135 posts
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    Yeah, it's the rest mass that I'm talking about. Not that it's really possible to be sure of a photon's rest mass, but much of what we know of time, space and dimension is based on the assumption.

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  • Dangerous_Dan 1 Feb 2013 12:51:43 2,380 posts
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    Light travels with different velocities in different mediums, like glass, vacuum, air. It is slower, that's easy to measure. So after it leaves the glass and enters air, how long does it take to accelerate back to its speed in air?

    Light has no mass but it has an impulse so how is p=m*v? Go figure. So light shares certain qualites with mass like having an impulse but has no inertial mass.

    Now this is important: Is inertial mass = gravitational mass?
    Because that's not a given although most believe so.
    It is not clear from the get-go if the mass which is pulled by gravity is the same mass which grants objects inertia.
    But experimentation showed that inertial mass and the mass quality which makes things fall down (gravitational mass) are the same.

    Yet light has no inertial mass but has the quality of gravitational mass.

    The conclusion is that objects, atoms have inertial and gravitational mass and that both are the same for atoms. While light only has gravitational mass but no inertial mass.
  • Dirtbox 1 Feb 2013 12:53:51 78,135 posts
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    So rest mass = 0.

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  • Dangerous_Dan 1 Feb 2013 12:56:35 2,380 posts
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    If by rest mass you mean the F=m*a kind of mass then yes.
  • LeoliansBro 1 Feb 2013 13:02:23 44,141 posts
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    That's also the mass referred to in E=mc2 (and k=h/(mv))

    LB, you really are a massive geek.

  • grey_matters 1 Feb 2013 13:14:22 3,729 posts
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    Like I said you have to be very careful.
    Also, do not consider mass and matter to be the same thing. Many physical equations will apply to both classical notions of mass (derived from matter) and relativistic ones (derived from energy/mass equivalence).

    De Broglie adapted the momentum equation for light:

    p = h/lambda
    (p= momentum, h= Planck's constant, lambda= wavelength)

    to particles of matter with the standard ("classical") p=mv relation.

    There is no "divide by zero" as that case doesn't apply to light in the first place.

    Edited by grey_matters at 13:23:02 01-02-2013
  • spindizzy 19 Jun 2013 13:41:06 6,501 posts
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    What?!?! There was a thread with my name on it, and I only find it now???
  • X201 19 Jun 2013 13:42:46 15,359 posts
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    You were probably too busy playing with your tractor beam thingy.
  • spindizzy 19 Jun 2013 13:45:01 6,501 posts
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    Yep.

    BTW in case anyone is interested, an experiment at CERN recently announced that they can test whether gravity really acts on antimatter the same as matter.
    http://www.bbc.co.uk/news/science-environment-22355187
    (they don't have enough data yet though)
  • RedSparrows 19 Jun 2013 13:51:07 22,587 posts
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    spindizzy here's my science question, and it's typically vague:

    How do the 'top' scientists, or perhaps more outspoken ones, talk about science and its role in explaining the world? Are there scientists who engage closely with the arts, in this respect?

    For example, the German Romantic movement said that the whole Western tradition, on which science must surely rest, was false - there was no objective truth (or an approximation of objective truth that we can at least grasp in part), and that the universe was unknowable, benign or hostile, a collection of perpetually moving spirits and geists etc etc etc. It all varies.

    How does science, for the actual scientists themselves, talk about such things - if at all? Where does science meet philosophy (in the wider, historical sense) in the working lives of scientists?

    Edited by RedSparrows at 14:00:17 19-06-2013
  • sirtacos 19 Jun 2013 13:52:10 7,280 posts
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    sport wrote:
    Honestly, you don't need to wash it - a rinse is fine!
    Glol
  • Deckard1 19 Jun 2013 13:57:07 27,981 posts
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    I have a question, if computers are just a series of switches set to yes or no, how the fuck does all this stuff work then? Keep it brief.
  • kalel 19 Jun 2013 13:57:58 87,571 posts
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    De Vinci was one of the most eminent scientists, philosophers and artists in history.

    Don't really have a point here.
  • Chopsen 19 Jun 2013 13:58:16 15,948 posts
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    You just have to ask it the right questions.
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