with the wavelength ratio 1 + z we want 1 + z = 1/2 so v = -3/5 c = -0.6c if i calculated correctly (i did this in my head without a napkin), where the source moves away from the observer with velocity v. so it would have to move towards you quite rapidly.
assuming we want the frequency to double,
going by this formula: https://en.wikipedia.org/wiki/Redshift
with the wavelength ratio 1 + z we want 1 + z = 1/2 so v = -3/5 c = -0.6c if i calculated correctly (i did this in my head without a napkin), where the source moves away from the observer with velocity v. so it would have to move towards you quite rapidly.
0.6 *300 000 km/s =180 000 km/s
How many freedom units is that?
Greater than the cumulative speed achieved by 20,000 horses fed with 3 canisters of barley.