Originally Posted by JHM2K

Here's my question: how do scientists KNOW the distances with any reasonable precision?

For instance... Sonar works based on a frequency sent and received. Knowing the speed of the frequency, and dividing the time it takes to travel by two (signal down TO object + signal back FROM object = total elapsed time, divide by two to calculate distance TO object) you can have a reasonably accurate gauge of distance/depth.

Since laser/light range finding works in a very similar fashion (only a beam instead of a sound wave), how can scientists say something is 'millions' of light years away if the technology used to produce the laser isn't even a hundred years old? Based on that, if a celestial object was a million light years away, it would take 2 million years for the beam to hit the object and reflect back, correct? Meaning, in order for anyone to ACCURATELY prospect that the object is a million light years away, a caveman would have had to launch the laser. This is also assuming the caveman could aim the laser accurately enough to hit a star that far away. 1° of deviance in accuracy of the beam means your beam is millions of miles off-target.

Seems like 'space' is all one big guess.

And if the Voyager still has enough power to transmit a signal billions of miles away after 33 years, what kind of power source is in that thing, and WHY are we still using AA batteries in our remotes that go dead every year?

Snacks for thought....