...and this is why I don't like the balloon analogy -- people point to the way in which the analogy is completely unlike the analogous system, and then assume that there is a comparable property in reality.
Think of the universe as the dolly zoom in the movie Vertigo. No matter where Jimmy Stewart is, as he climbs up the tower, when he looks down you see the bottom of the tower stretching away from him. There is no real center point -- it's not like the center of expansion suddenly moves up the tower with him. And it's not as if the bottom of the tower is expanding into the ground below. It's just that the space between him and the bottom appears to stretch away.
Actually, let me rephrase that -- it's not counter-intuitive at all that amplitude goes as 1/r, but what's odd is that with gravitational waves, you directly detect the wave amplitude, so detectability falls off as 1/r. For most waves, you detect the wave intensity, which goes as amplitude squared and therefore 1/r^2.
Counter-intuitively, the strain amplitude goes as the inverse of the distance, not the inverse square!
The Earth-Moon system is bound, so not useful to measure the Hubble constant. By definition, a bound system is one in which gravity has overcome cosmological expansion.
These are all true, but I find the reasons people are giving for grocery stores completely miss the point:
No two tomatoes are the same.
I can't tell you which tomato I want without picking it up, looking at it, and feeling it.
And every US state has official road maps for free at the first visitor's center after you cross the state line.
It's all about delta-v, not about the occurence of said gasses on Earth.
Rockets work, whether we like it our not, according to the Tsiolkovsky rocket equation: the delta-v you can obtain it only logarithmic in your start mass / payload fraction, but linear in your exhaust velocity. That velocity is in ~3 km/s for chemical rockets, but 20-50 km/s for ion engines. That allows you to push a probe/ship from LEO into a transfer orbit using a massively lighter ship, which in turn allow you to launch that into orbit using a massively smaller launch vehicle.
I spend a large fraction of my time deep in the National Radio Quiet Zone. WiFi is illegal. The assumption that you will always be able to do wireless is faulty.
For some reason that I don't understand, ethernet adapters die at a ridiculous rate. I've been through 7 in 3.5 years, and everyone I know who uses them has similar stories. I've tried a variety of brands, with no difference in the results.
...without the transfer or matter of energy.
Come on it is the first line of the summary and a glaring error editors.
"Necessity is the mother of invention" is a silly proverb. "Necessity is the mother of futile dodges" is much nearer the truth. -- Alfred North Whitehead