Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

I My lecturer says "Special relativity is absolutely wrong"

  1. Apr 21, 2016 #1
    Hi guys

    In an assignment I wrote for university I was penalised for claiming that FTL neutrinos would violate special relativity.

    Below is the relevant part of my assignment and the response from my lecturer. Could somebody please explain what he could mean by that because as far as I can tell, FTL particles violate special relativity and special relativity is not "absolutely wrong".

    https://imgur.com/bXt3O6K [Broken]
     
    Last edited by a moderator: May 7, 2017
  2. jcsd
  3. Apr 21, 2016 #2
    Faster than light neutrinos don't exist - the experiment that purported to find them in 2011 turned out to have electrical flaws that lead to misleading data.
    Of course were they to exist they would violate SR.
     
  4. Apr 21, 2016 #3
    His little schpiel about General Relativity allowing faster than light travel is absolute hokum.
    Special Relativity is not wrong in the way that Newtonian mechanics is not wrong. They are just approximate theories - effective only within their domain of application.
     
  5. Apr 21, 2016 #4

    russ_watters

    User Avatar

    Staff: Mentor

    What class/level is that for?
     
  6. Apr 21, 2016 #5
    If I'm not mistaken, general relativiy posits that curved spacetime must reduce to the physics of special relativity for small free falling areas. Which would suggest in a free falling frame (a local inertial frame) the speed of light is still the max speed locally.
     
  7. Apr 21, 2016 #6

    Orodruin

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    Locally, the speed of light is the upper limit, GR and SR agrees on this. On a global level, you would have to (very carefully) define what you mean by "travelling faster than light" if you are going to make such blanket statements.
     
  8. Apr 21, 2016 #7
    Yup, the contention of my assignment was that scientific anomalies such as the "discovery" of FTL neutrinos are usually due to experimental error.

    Yup exactly what I thought. Alas I'm still going to lose marks sigh...

    A philosophy of physics class at one of the top universities in Australia. Kind of disappointing. (btw guys please don't go trying to message my lecturer saying he is wrong, I get the feeling that would screw me over pretty bad).
     
  9. Apr 21, 2016 #8
    Okay guy's i really need to know if I'm missing something here or is my lecturer brainwashing my entire class into thinking special relativity is wrong and completely superseded by general relativity.

    Here is a discussion one of the students in my class had with the lecturer:

    https://imgur.com/kysV8bn [Broken]
     
    Last edited by a moderator: May 7, 2017
  10. Apr 21, 2016 #9
    Putting aside what my lecturer said for a moment, I have a question: Due to the expansion of the universe, galaxies the distance between distance galaxies grows extremely quickly over time. Can we say in any sense that these galaxies are travelling faster than the speed of light?
     
  11. Apr 21, 2016 #10

    jbriggs444

    User Avatar
    Science Advisor

    No. It would be better to stick with the statement that their separation grows quickly over time.

    Edit: One could pick a coordinate system in which one galaxy is at rest and the other galaxy has a velocity faster than the speed of light. But that "velocity" is as much an artifact of the choice of the coordinate system as anything physical. Pick another coordinate system and you get another "velocity". One ought not give such "velocities" the courtesy of calling them by that name.
     
  12. Apr 21, 2016 #11

    jbriggs444

    User Avatar
    Science Advisor

  13. Apr 21, 2016 #12

    russ_watters

    User Avatar

    Staff: Mentor

    Taught by a physicist or philosopher?


    Just the title makes my skin crawl.
     
  14. Apr 21, 2016 #13
    I think you can guess the answer to that...

    Ahaha that's a good read.

    Guys are there ANY circumstances under which special relativity is superseded by general relativity? Is there at least an inkling of truth to what he is saying?
     
  15. Apr 21, 2016 #14

    ChrisVer

    User Avatar
    Gold Member

    Why would FTL particles violate SR?
    Something that could potentially violate SR is for massive particles to travel at the speed of light... the region of travelling slower and faster than the speed of light are nicely defined in SR.
     
  16. Apr 21, 2016 #15

    jtbell

    User Avatar

    Staff: Mentor

    General relativity applies when there is gravity. Special relativity is a good approximation when gravitational effects are "small enough" that we can ignore them for the purposes at hand.
     
  17. Apr 21, 2016 #16

    atyy

    User Avatar
    Science Advisor

    Your lecturer is wrong, because special relativity is a great approximation to general relativity in some domain, and the report of superluminal neutrinos was in the domain where special relativity is expected to hold.
     
    Last edited by a moderator: May 7, 2017
  18. Apr 21, 2016 #17

    atyy

    User Avatar
    Science Advisor

    In a strict sense, general relativity forbids the comparison of velocities of distant objects. Only special relativity permits it.

    There is a sense in which the galaxies can be said to be travelling faster than the speed of light, but it is not in the same sense in which the neutrinos were said to be travelling faster than light.

    See post #10 by jbriggs444 above.
     
  19. Apr 21, 2016 #18
    Thanks for that explanation. So I guess the question is, if I want to go about trying to convince him that he is wrong (an extremely difficult thing to accomplish when he has based entire lectures on SR being wrong) how should I go about it and what are some of the best sources I can use to back up my claims?
     
  20. Apr 21, 2016 #19

    Orodruin

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    Well, technically, he is not "wrong", just as SR is not "wrong". The concept of "wrong" is not very useful when dealing with scientific models and it is much more relevant to discuss whether a model is "useful" or not. Newtonian mechanics might be considered "wrong" as it does not describe what we can observe at large velocities or small distances. However, this does not invalidate Newtonian mechanics, it just restricts its domain of applicability. It still works perfectly fine for most every-day applications.

    In the same sense, SR is not "wrong" it is just not applicable to some situations when space-time curvature becomes significant. If your lecturer wants to take his argument to the extreme - GR is also "wrong", although its domain of applicability is larger than that of SR.
     
  21. Apr 21, 2016 #20

    russ_watters

    User Avatar

    Staff: Mentor

    I would talk to a physics professor at your university about it. You are unlikely to win an argument like this on your own, regardless of what sources you provide.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: My lecturer says "Special relativity is absolutely wrong"
  1. Penrose Lecture (Replies: 2)

  2. Video lectures on GR? (Replies: 7)

  3. Giving a lecture (Replies: 2)

  4. Is Einsten saying (Replies: 28)

Loading...