So, I started walking myself down this rabbit hole of how to make this work, then realized why it wouldn't. I'm leaving my path to get there intact for everyone's amusement. Spoiler Not if the center point is assumed to be moving. Yes. Not if the central point of origin is in motion on the same axis it fires towards and away from. Unless the entire system is in motion - which is what we're trying to measure here. Agreed. Very similar, but measuring two entirely different things. They were trying to detect the Aether. My idea is to detect 'absolute motion' by utilizing the peculiar nature of light's 'absolute velocity'. LIGO utilizes a laser through a splitter down two tunnels on a L shaped system, bounces back and forth through the length of it multiple times from mirrors to augment the net effective length of the tunnel and examine the interference patterns of the beam when rejoined to determine if one tunnel got microscopically longer than the other due to fluctuations in space time from gravitational waves. Using a similar principle, straighten out the track - and make it a real long one by re-bouncing the beams on their opposing ends. Fire a laser through a splitter at the center down the paths in both directions. Bounce them in their respective halves of the system a few thousand times. Compare the interference pattern to see if one tunnel "got shorter" than the other -gradually-. Code: |--------------------*+++++++++++++++++++| If it is a momentary effect, that is a gravitational wave. If it is a continuous effect over time that the beam fired down one tunnel had a shorter time to return than the corresponding beam fired down the other tunnel, then the measurement platform is moving in the direction of the shorter return time. Each 'laser packet' is moving at the speed of light in opposite directions Code: |--------------------*+++++++++++++++++++| in motion -> results in measurement |---------------------*++++++++++++++++++| Why build it in space? 1. Calibration. Run it in one orientation, measure. Flip it over, run it again. Just like calibrating a bubble level. 2. Enables measurements with the test rig (huge as hell) at different velocities. And why that won't work: Spoiler The beam fired in each direction must return to center for measurement of interference. Although the outbound paths may be of differential lengths (effectively shorter time to mirror in the direction of travel) - thus the impact of the light on either end may be different, the net time of arrival back at the center point would be the same - as the center point is also moving at the same rate as the ends. So, what might work... We know that everything in the universe is moving relative to everything else in the universe. We know that light, regardless of origin or the velocity of the origin, travels at the same rate (with exotic exceptions). Light does not inherit the added inertia of an origin in motion (this is key). Make the 'racetrack' very long - not sure how long, but likely hundreds of miles, but of an exact known length. Place the detectors in the ends, not the center. Use insanely accurate, independent and synchronized clocks at the origin and detectors. (Not real values.) Light leaves the central point at T=0.0EXP-20. Light arrives at the detector in the direction of travel at T=0.2EXP-20. Light arrives at the detector in the reverse direction of travel at T=0.1EXP-20. The light beam travels at the same absolute rate in both directions regardless of the motion of the point of origin. The whole system is moving on the same path. The light moving toward the 'rear' detector would have a shorter path to target than the light moving toward the 'front' detector. The rear detector is moving toward the light. The front detector is moving away from the light. The difference in detection times can translate into the velocity of the system. Can still flip it over to calibrate it. The clocks and detectors would have to be insanely accurate. Would need to be a very very long craft. The longer it is, the more accurately it could measure the difference in arrival times. An analogy... Jesse James is standing in the exact middle of a train car travelling at 50KPH. Jesse has two exact pistols with two exact bullets with two exact powder loads. The distance from him to the front and back walls is exactly the same. He fires in both directions at once, hitting two synchronized stopwatches causing them to stop. The bullets hit the front of the car and the rear of the car simultaneously - the bullets inherited his and the train's momentum. (ignoring lowered velocity gravitational drop blah blah) Jenny James, Jessie's great-great-great-great-great-great granddaughter, stands in the center of a long compartment inside of a spaceship traveling 50000KPH. Jenny has two exact laser pistols that fire the same wavelength. The distance from her to the front (direction of travel) and rear ends of the compartment is exactly the same. She fires in both directions at once, hitting synchronized atomic clocks at either end causing them to register the hits. The light hits both clocks, but the rear (relative to direction of travel) clock shows that it stopped first by some tiny fractional amount - the light does not inherit Jenny's and the spaceship's momentum. Light traveling toward the rear of the craft travels at the same absolute velocity as light traveling toward the front of the craft. The rear wall of the craft, moving toward the light source shortens it's net path. The front wall of the craft, moving away from the light source lengthens it's net path. So, I'm still convinced that we could hypothetically use the constant nature of the speed of light and the fact that it does not inherit momentum to create a detector to measure our absolute velocity through space. Velocity is a vector that requires no point of origin. Just, remember that you're standing on a planet that's evolving And revolving at nine hundred miles an hour That's orbiting at nineteen miles a second, so it's reckoned A sun that is the source of all our power The sun, and you and me, and all the stars that we can see Are moving at a million miles a day In an outer spiral arm at forty thousand miles an hour Of the galaxy we call the Milky Way ... The universe itself keeps on expanding and expanding In all of the directions it can whiz As fast as it can go, the speed of light you know Twelve million miles a minute and that's the fastest speed there is - Month Python et al. But - those are all Newtonian/Galileo relative measures. Do we have anything currently that we can say truly has no kinetic energy? An experiment was recently launched to build a Bose-Einstein condensate in orbit so that it can be contained within a low gravity environment in hopes that it will last minutes instead of sub-seconds. It will still have inherent motion as sung above. Would there be anything special to measure in a system of true 0 velocity? Put on a set of long blinders and go for a ride in the passenger seat of a fast moving car while looking out the side window. A farmer's field appears to be just a blur of green (low signal to noise). But, if you stop, you can see that the field has furrow rows and a weed in the 40th row (high signal to noise). What would we try to find, see, measure, test if we could truly, 'stop'? I have no idea really. Pure science at that point. --- Double Post Merged, May 25, 2018, Original Post Date: May 25, 2018 --- Addendum: Good article on this concept of, "How fast are we going?" https://www.scientificamerican.com/article/how-fast-is-the-earth-mov/ 390K/s with reference to the CBR (Cosmic Background Radiation). But - the CBR may be moving as well.