Hey so i've started learning some cosmology and i have a question about the expanding universe.(adsbygoogle = window.adsbygoogle || []).push({});

So i was told to picture a 3D graph with time on the vertical axis and space making a plane perpendicular to the vertical. I am using the metric where the diagonals are (1,-a,-a,-a) where a is a function of time. Now when the graph is drawn it looks like a grid which just gets bigger a time increases. Now i was told that dX which is the space between two points on the grid is always measured to be 1 unit. So for example as the grid expands the distance between points is always taken to be 1 unit, but your measuring stick would have also grown too.

Now my question is to say i were to travel between two points in the expanding space but at two different times. Technically the earlier time i would travel a farther distance then the later time. But i would still always be traveling the distance of 1 unit. Would the later journey require more energy compared to the earlier journey, and doesn't this mean that energy would be increasing?

I thought of it being some sort of Lorentz transformation but i don't think that would work because the two frames are different since one is stretched.

thanks for your help

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# Expanding universe and energy question

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