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

Can we see the Earth in the past

  1. Feb 27, 2010 #1
    If matter modulates space-time then the Earth modulates space-time as it travels through it. If it does then can we send a spaceship to the location of Earths wake and measure the disturbance. How? By using laser interferometry. If we arrange a laser transmitter to shine through Earths wake and arrange a laser receiver on the other side of the wake we can detect space-time disturbances. Those disturbances can be de-modulated and then reproduced as images of Earth. The entire process hangs on whether space-time is modulated by matter and how long the disturbance lasts.

    What do you think?
  2. jcsd
  3. Feb 27, 2010 #2


    User Avatar
    Science Advisor
    Gold Member

    If by "Earth's wake" you mean the gravitational waves produced by the Earth-Sun system, then these waves are really puny...I'm not sure how accurate of a machine you would need to measure that. If you just mean Earth's disturbance of Space-time, we could measure that here on Earth...as Gravity. o_O
  4. Feb 28, 2010 #3


    User Avatar
    Science Advisor
    Gold Member

    Gravity waves are very weak making them exquisitely difficult to detect [see LIGO]. Only compact objects, like binary neutron stars [e.g., Hulse, et al], have yielded any observable effects.
  5. Feb 28, 2010 #4
    The Earth's wake is a disturbance of space-time that means space is affected and time is affected. The question is do we have instruments that can detect such changes? Perhaps at some point we can design a clock that can detect nano-changes in space-time then move the clock around to collect data points at which time a picture can be formed.

    If the physics allow it then it's just a matter of technology catching up.
  6. Mar 13, 2010 #5
    It sounds like you're talking about gravity waves, which are the space-time disturbances created by a moving mass. Like Matterwave and Chronos said, these waves are very difficult to detect, and we haven't been able to detect the strongest of them until just recently. Unfortunately, it doesn't seem to provide much information as to what that object was like in the past.

    As an analogy, this is sort of like dropping a rock into a pond and studying the ripples that it creates. Then by looking at only the ripples, trying to guess the composition of the rock. We may be able to infer a few things: whether it's a large or small rock, heavy or light, dropped straight in or at an angle, etc.
  7. Mar 13, 2010 #6
    Gravitational waves propagate through spacetime at the speed of light, so even if it were possible to accurately detect the waves and infer images, you would only be able to "see" as far into the Earth's past as when your detector was launched into space and started recording.
  8. Mar 14, 2010 #7
    I'm saying that matter effects space-time at a quantum level. As the earth moves through space-time it's not like a boat moving through water pushing the water out of the way and leaving a disturbance behind like a ships wake turbulence. Rather, all space that was occupied by Earth has been "changed" by Earths matter. The question is how much change and how long does the change stay. Does space-time get modulated by matter and does this modulation stay till some other matter changes it?
  9. Mar 14, 2010 #8
    That depends on whether or not space-time gets modulated by matter and how long the modulation stays. It would be similar to a cosmic ray going through a cloud chamber only in a cloud chamber the track doesn't stay too long. If Earths "track" stayed a while then a measuring device could be send at any point of Earth's passing and detect the "track".
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook