Nothing to do with anything other than a situation which occured to me and puzzled me. I'm by no means a physicist, but I like to understand the world around me.
So here are my underlying assumptions:
- From the perspective of the universe, matter and energy are interchangeable.
- Law of conservation of mass and energy states that mass and energy can be interchanged, however, they can never be increased or reduced.
So let's go completely blue-sky here and say that we are masters of matter/energy, and can convert them back and forth at will with no loss. Not possible from a realistic perspective, but my understanding is that it is possible from a theoretical perspective, yes? So theoretically, you could take a 10-lb block of lead, convert it to light, and convert that light back to a 10-lb block of lead.
My question is --- let's say I made a perfectly straight tunnel with a perfect vacuum inside it and tied it to the space elevator so that one end is on the earth and the other is in orbit. Now, I convert a 10lb block of lead into laser light at one end of the tunnel (on earth), and shoot the light up the tunnel into orbit, where the energy is then converted back to lead. (the tunnel/laser isn't critical, you could also use a superconducting wire and electricity, or whatever).
Now here's the thing - my understanding of the above would violate the law of conservation of matter and energy, so I'm pretty sure it's wrong. It can't be possible that the block of lead would remain 10lbs, because if so, it would have gained potential energy from nowhere. So what am I missing? Given perfect conversion rates and absolutely no loss of energy in transmission, would the mass of the lead be lower? Seems like it would have to be to make up for the "new" potential energy, but why?
