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

Lorentz Telescope

  1. Jan 2, 2015 #1
    Andromeda galaxy is measured as about 2,500,000 light years from me as I am at rest with respect to the Earth.
    Using luminosity of known objects in Andromeda.
    I have a close to light speed space ship which is pointing toward the Andromeda galaxy with a camera mounted on the nose cone.

    I am going to ride in the spaceship so I will select a coordinate system which is traveling with the
    space ship when it reaches 99 per cent the speed of light with respect to Earth I will take a picture.

    Will the space ship nose cone picture show the distance to Andromeda as closer than a picture take from Earth?
    Will the space ship nose cone picture show Andromeda younger than a picture taken from Earth?

    Duordi
     
  2. jcsd
  3. Jan 2, 2015 #2

    ghwellsjr

    User Avatar
    Science Advisor
    Gold Member

    There's no such thing as a Lorentz telescope, if by that, you mean one that will determine the Lorentz contraction and Time Dilation effects simply by observation and particularly by taking a picture. These are coordinate effects and unless you include a calculation that assumes a particular frame of reference, you're not going to get those factors.
     
  4. Jan 2, 2015 #3
    This Muon experiment produced relativistic results.

    http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/muon.html

    The results can be viewed as a time delay or Lorentz contraction depending on the coordinate system you choose but either coordinate system will work.
    So with the space ship camera I should be able to pick my coordinate system and get results which comply with my relativistic predictions.

    Suppose 10 years ago a super nova was recorded in Andromeda galaxy but due to weather conditions or the fact the Hubble telescope was not deployed yet
    we were not able to get all of the pictures we wanted. If Lorentz contraction does indeed happen and the distant galaxy can be brought closer by an imposed
    velocity then the light path time travel can be shortened. It will not take an impossible velocity to make Andromeda 249,990 light years away and we could take a picture of the ten year old super nova.

    In a more general case we could accelerate a camera and record all of the super novas in Andromeda for the last 100 years.
    So the Lorentz telescope camera would be more of time travel camera than a zoom camera.

    Duordi.
     
  5. Jan 2, 2015 #4

    ghwellsjr

    User Avatar
    Science Advisor
    Gold Member

    That's nonsense.

    Once an image of a distant event has passed you, there is no way to get to see it again. You would have to travel at faster than the speed of light away from the event to catch up and pass the image that is now traveling at the speed of light behind you.
     
  6. Jan 2, 2015 #5

    Vanadium 50

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor

    Yes it will. You have to outrun light to do this, and that means you'll be traveling faster than light - an impossible velocity.
     
  7. Jan 2, 2015 #6

    PeterDonis

    User Avatar
    2016 Award

    Staff: Mentor

    The distance to Andromeda is not directly observable from the picture, either from the space ship or from Earth. It has to be calculated, and to do the calculation, as ghwellsjr pointed out, you need to adopt a coordinate system. The distance you get will depend on which coordinate system you adopt.

    No. At the instant the space ship leaves Earth (if we assume that it accelerates to 0.99c instantaneously), the picture it sees is the same as the picture Earth sees. As the space ship travels, it will see Andromeda aging, and doing so much faster than Earth sees it aging--but that's because the space ship is moving towards Andromeda, so a light signal emitted by Andromeda at a given instant reaches the ship before it reaches Earth.
     
  8. Jan 3, 2015 #7

    pervect

    User Avatar
    Staff Emeritus
    Science Advisor

    Pictures don't directly show distance, as several posters have already mentioned. I don't think anyone has specified the actual optical effects though. The view from the spaceship would be something like that described in http://math.ucr.edu/home/baez/physics/Relativity/SR/Spaceship/spaceship.html, which however shows starfields rather than Andromeda.

    Important effects will be:

    Relativistic aberration - which will make Andromeda appear to have a smaller angular size in the photograph
    Relativistic beaming - which will make Andromeda appear brighter
    Doppler shift - which will change the color towards the blue end of the spectrum.

    As you accelerate in the direction of Andromeda, the relativistic aberration effects will make it's angular size shrink. At one time I had a link to a video (Searle, I think - not sure, it was Australlian) that showed a similar effect, but I haven't found the video online.

    The apparent age of the image of Andromeda will not change.

    The video would be nice to illustrate how the angular size shrink appears visually, but I can't find it :(

    It might also be worth reviewing the topic of distance measures in astronomy, but since that wasn't the question, I won't actually go into it. Since pictures don't convey distance directly, it would be worthi thinking about what techniques we do use to determine the distance to andromeda. It would be painful to try to analyze them all, but if you have a specific technique you think would apply to your spaceship case, do mention it. (Some techniques that are used for distance estimation would not be useful for the spaceship case).
     
    Last edited: Jan 3, 2015
  9. Jan 4, 2015 #8
    Good point, The Lorentz image will not be of the past past but the future. Lorentz contraction of the distance to Andromeda will cause the image to arrive sooner than it would otherwise so I will see an image which my normal telescope will receive at a later time.

    Thanks for the comment!
     
  10. Jan 4, 2015 #9
    As in the case with the muon's
    http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/muon.html
    The "close to the speed of light" muon's are younger when they reach Earth regardless of what coordinate system you use.
    If the muon's carried photographic information we would have recorded a younger photograph
    then a slower moving non Lorentz contracted particle which arrived with photographic information at the same time
    as the muon's.

    Do light photons Lorentz contract?
     
  11. Jan 4, 2015 #10

    ghwellsjr

    User Avatar
    Science Advisor
    Gold Member

    Are you saying that you carry two telescopes in your spaceship, a Lorentz telescope and a normal telescope, and that they take different images?

    Since all telescopes, cameras, and eyeballs are dependent on light travel time, they see images of the past, not of the future. I really don't know what you are trying to say in this post.
     
  12. Jan 4, 2015 #11

    ghwellsjr

    User Avatar
    Science Advisor
    Gold Member

    Another confusing post. When you say the muons are younger, what are they younger than?

    When you say the muons are taking pictures, what are they taking pictures of?

    If you have two muons that start at the same place but at different times and they arrive at earth at the same time, which means they traveled at different speeds, then yes, the faster one will have aged less than the slower one. Is that what you are pointing out?

    Why are you concerned about the Length Contraction of muons and photons? It has nothing to do with the explanation of why muons reach earth or anything else that I can think of in this thread.
     
  13. Jan 4, 2015 #12
    Suppose the Hubble space telescope were to take pictures of a pulsar with a two second interval in the Andromeda galaxy which happens to be in the Hubble
    telescopes orbital plane.
    Andromeda is approaching the Milky way at 110 Kilometers per second.
    http://www.nature.com/news/andromeda-on-collision-course-with-the-milky-way-1.10765
    The Hubble space telescope has an orbital velocity with respect to earth of about 8 Kilometers per second.
    http://hubblesite.org/the_telescope/hubble_essentials/
    The difference between a Hubble telescope Andromeda approach velocity and a Hubble telescope recession velocity is about 16 Kilometer per second.

    The Hubble telescope takes a sample movie while it has a receding velocity and again as it has an approaching velocity with respect to Andromeda galaxy.
    The photon image will be Doppler shifted and so will the period of the pulsar due to the differential Hubble telescope velocities.
    If the "distance" to Andromeda galaxy is about the same 250,000 light years I can determine how many quasar pulse cycles are traveling between the Hubble
    Space telescope and the pulsar in Andromeda for both the approach and receding Hubble velocities as a theoretical observer on the Hubble space station.

    There will be less pulse cycles for the receding Hubble velocity and more pulse cycles for the approaching velocity.
    Less pulse cycles require the image to be newer or younger.
    More pulse cycles require the image to be older.

    Notice that the image is not the same age.

    The same process can be derived by Lorentz contraction of the distance to Andromeda.
    If the pulsar has a pattern of pulsar fluctuations we may be able to use a land based telescope to record the pulsar pattern and match a "future"
    pattern recorded by the Hubble space telescope to a delayed image of the lower velocity land based telescope.

    Your thoughts?

    Duordi
     
  14. Jan 4, 2015 #13

    I was intending to compare two sets of particles.
    One set of particles Muons travel very fast and another set "not-muons" travel slow.
    Both carry photographic information.

    When I develop the pictures the muon photo is younger because of the travel velocity but also an additional amount younger because of (Lorentz contraction or time delay) depending on how you choose your coordinates.

    I will try to respond to another post with an example that clarifies this.
     
  15. Jan 4, 2015 #14
    No a Lorentz telescope requires velocity to operate.
    Lets suppose the Lorentz contraction is real.
    If I accelerate my space ship close to the speed of light the universe will flatten like a pancake in the direction I am moving.

    So if I take a picture of a star it should be closer than it was before I attained close to light speed.
    Light always travels at C so if there is less distance the image I receive must be younger.

    We do not see a distant galaxy as it is but as a time delayed image allowing the light to travel from a distant object to us.
    The Lorentz telescope would allow us to see an image which will arrive on Earth in the future.

    If as I accelerated my space ship in stages recording pictures I would receive light which the Earth will receive at a later time.
    When I discover an interesting occurrence I will tell my friends on Earth.
    My friends on Earth have time to prepare and can get detailed information when the image arrives at Earth velocity.
     
  16. Jan 4, 2015 #15

    ghwellsjr

    User Avatar
    Science Advisor
    Gold Member

    No they won't. You can't tell your friends on earth anything faster than the speed of light so if you send them a message at light speed of something you saw earlier because you are closer to the event, not because you are traveling toward the event, then they will get the message at the same instant they see the event for themselves.
     
  17. Jan 4, 2015 #16
    You are assuming space time must be flat and that your coordinate system is a "preferred coordinate system" which is the only one allowed.
    Accelerating to close to light speeds causes space time to warp.
    The distance between any particles in space is relative and not a fixed distance.

    Suppose I have two particles and i accelerate them to close to light speeds toward each other but they are 250,000 light years apart.
    I can theoretically accelerate the particles until they are one light year apart due to Lorentz contraction of space time.
    They will have created a worm hole but not one which is visible by everyone like a science fiction movie.
    Only the two high speed particles will experience this close condition because the configuration of the universe is based on the observer.
    If the two high speed particles communicated they would receive one year old data that is to say it would only take one year for the light to travel between them.
    If one of the particles close to Earth were to send a message to the Earth it would be time dilated because of the difference in velocity between earth and a particle
    but the message would arrive almost immediately because the separation distance is small.

    This does not violate faster then light speed information travel because the information did not travel faster than light in your preferred "at rest with you" coordinate system.
    Relativity means your preferred observed universe is no more credible than any other.
     
  18. Jan 4, 2015 #17

    pervect

    User Avatar
    Staff Emeritus
    Science Advisor

    If you have an emitter of electromagnetic radiation in andromeda of a known frequency, there will be in theory a certain number of "pulse cycles" of that radiation between you and Andromeda along the path of a given light beam (technical name - null geodesic) connecting you to Andromeda that you see at a particular time.

    I don't see any particularly good way of measuring that quantity experimentally that doesn't involve things like infinite chains of observers at every point between you and Andromeda. If one had such a chain of observers, one could do things like plot the E-field (assuming a plane-wave source of sufficient magnitude) versus a sort of length parameter (techinical term: an affine parameter) of the null geodesic, and count the number of cycles to get an observer independent number.

    I'm not sure if you meant to imply there was some "easy" way involving something other than an infinite number of chain of observers to measure this "number of cycles" quantity, or whether you were simply stating that the number existed, when you say "I can determine....". But I'm not sure this is relevant, really.

    The fact that the number of cycles is observer independent suggests determining a "distance measure" by multiplying the wavelength of the source by the number of cycles along the path, since we've argued that the number of cycles along the path is an observer-independent quantity. While the number of cycles along the path is an observer-independent quantity, the length of one cycle (the wavelength of the radiation) is not observer independent. Furthermore this wavelength doesn't transform by a factor of gamma, it transforms via the relativistic doppler factor, bondi's "k-factor", http://en.wikipedia.org/wiki/Relativistic_Doppler_effect. Thus this distance measure isn't any classical sort of distance, it doesn't transform in the manner distance as measured by a ruler does, and doesn't have the traditional notion of "simultaneity" that a classical distance measurement by a ruler does.

    Certainly, though, if you are in the flat space-time of special relativity and you multiply the wavelength as measured by an observer stationary with respect to the source by the number of cycles along the geodesic path, you do get the observer independent proper distance.

    I have reason to believe (see https://www.physicsforums.com/threads/synge-optical-observations-in-gr.754691/#post-4753260) that in the literature this general idea is known as 'optical coordinates' and that they are discussed in Synge's book "Relativity, the special and general theory". However I don't have this book personally, nor have I had a chance to read it.
     
  19. Jan 4, 2015 #18

    PeterDonis

    User Avatar
    2016 Award

    Staff: Mentor

    duordi134, you seem to have a number of misconceptions, but this one may be the biggest:

    No, it doesn't. Spacetime is the same no matter what speed you are traveling.

    ("Speed" is relative anyway, so you, right now, are traveling at close to light speed relative to, say, a cosmic ray particle passing by Earth. Does that mean you are warping spacetime just by standing still on Earth?)

    I think you need to re-think all of your posts in this thread with this misconception corrected. For example, this...

    ...shows the same error. No wormhole is created, and spacetime is the same for the two particles as for everything else. You have a serious misunderstanding of how Lorentz contraction works.
     
  20. Jan 4, 2015 #19
    I will take your advice and rethink myself and include the reference Pervect gave in his post.
    I think space-time exists as an infinite number of equally valid observers coordinate system and that there is no preferred coordinates systems which must produce all
    possible physical results.
    I do not believe that a single observer is preferred or that one observer can say if don't see anything then it does not exist.
    Another observer may both experience a different reality and interact with their reality differently as long as the laws of physics are followed for the coordinate system
    of the observer.

    Observed time of events and distances may be different between coordinate systems as long as the speed of light remains constant.

    For one observer (who is traveling close to the speed of light) with respect to the visible universe the universe may flatten like a pancake to a thickness of one light year.
    For another observer traveling at speeds close to zero with respect to the universe the universe may appear symmetrical 14 billion light years across.

    The time required for information to travel across the galaxy will be different for these two observers and there is nothing preventing the two observers
    from communicating information discovered if they are in close proximity with one another.

    We may prefer GR (a free fall coordinate observer) because the math is simpler but it does not make it any more valid then other observer
    reference frame.

    Physics is completely indifferent when it comes to the complication of the mathematics.

    Lorentz contraction will be accepted as a physical reality eventually because it is necessary to explain entanglement and other universal quantum properties.



    Duordi
     
  21. Jan 4, 2015 #20

    Dale

    Staff: Mentor

    Good plan. Thread closed.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Lorentz Telescope
  1. Lorentz Factor (Replies: 15)

  2. Lorentz Group (Replies: 10)

  3. Lorentz Transformation (Replies: 7)

  4. Lorentz invariance (Replies: 4)

  5. Lorentz transformation (Replies: 1)

Loading...