The key point to realize is this photo was taken on December 17th and not on December 21st at the time of closest approach.

I was able to replicate the scene in Stellarium from these co-ordinates, near New South Wales Australia:

S 34 21' 30.75"
E 151 4' 54.60"
2020-12-17 10:53:11 UTC

The angular separation between bodies in the photo are exactly correct.

I often like to think of myself as being humbled by the demise of the geocentrist view; the Earth is not the center of the Universe, the Sun is not the center of the Universe, humans are a relatively recent addition to a much older life history on this planet, etc.

But somehow this caught me off-guard. Perhaps after all the Earth and its set of conditions are not unlikely. Perhaps it is in fact MORE unlikely for life to have begun on Earth at all than at a far more hospitable place elsewhere in the Universe. And quite nearby in the Universe, since methods for finding exoplanets do not work at very large distances yet.

Perhaps the last stand to explain Fermi's paradox is that very intelligent life does not *need* to develop in order to survive on clement worlds, and that it takes far too long for it to develop to survive long enough on harsher worlds.

But, learning from the above, I should not take that for granted either. Very intelligent life may be a few simple mutations away for many lifeforms. Very being quite a relative term as well in our case.

Very interesting.

Having had intermittent mild tinnitus myself for as long as I can remember I have just generated this 13kHz tone you mentioned. It turns out mine is almost exactly at the same frequency.

Does anyone know of frequency distributions for tinnitus in the population ?

The galaxies or the images ? Sometimes you find what you're looking for.

God ?

It's one thing to detect a very hard particle like ceramic material, but will the method be able to detect softer anomalies ?

If the higher resolution really works on soft tissue, this could be a game changer. And perhaps, much more affordable than MRI.

Did you mean its doors ?

Well, yes there are tidal forces caused by Phobos.

But are they strong enough ? Maybe.

Electricity through a conductor propagates at the speed of light in the conductor, which depends on the relative permittivity (eps_r) and relative permeability (mu_r) of the medium. Relative to empty space. In the air where both eps_r = ~1 and mu_r = ~1, the speed of light is the same as its speed in free space.

Most conductors that carry electricity have mu_r=1 but eps_r > 1, typically < 10, which tends to slow down the speed of light in said conductor. A typical rule of thumb for propagation speed of light (electromagnetic waves) in a PCB or a coax is around c = 2/3 x c0. So around 66% which is much faster than the 10% you refer to.

Now, time constants in conductors (the charging of capacitors to their full voltage) are another matter and can make it appear as though electricity is propagating slower than the speed of light. The end of line capacitor really does begin charging at the speed of light, though.

To be precise, none of our probes are outside the Sun's gravity well yet, although they may still possess enough velocity to escape it, which I haven't verified.

The heliopause is where the Sun's solar winds stop from being dominant compared to the interstellar winds.

The existence of Oort's cloud extending a thousand times further than the heliopause shows that there's still a long way to go before escaping the gravity well.

It is the energy that counts. Energy is not a linear function of velocity (Ek = mv^2 / 2). That's why a crash against a wall at 100 mph is 4 times as bad as a crash at 50 mph.

From the point of view of an immobile reference frame such as the road, each car has Ek joules of energy from their speed, which must be dissipated to bring the velocities down to zero.

In a head-on crash without braking, the energy dissipates purely by folding metal and subsequently crushing bone.

If you had two similar vehicles crashing into each other at equal speeds, meaning both vehicles have equal amounts of kinetic energy and fold in an equivalent way during the crash: it's as if you had crashed against a solid wall. Imagine this as crashing in a mirror copy of your vehicle.

In other words although the two vehicles double the system's total energy, each vehicle requires exactly half of the total energy to bring their velocity down to zero: just like crashing against a wall.

There is not much one can do against a rogue vehicle speeding towards them. Perhaps the best that could be done for now is preemptive braking, which could give a chance to the hittee.

Or there may come a day where such speeding is limited by some technical authoritarian means.

I believe this clock is accurate up to ±2ns per day, not per second. In fact I would be shocked if it were per second.

Plus, this has to be understood as a random walk of time keeping. When a clock "looses" a second, it's not necessarily slower than some other reference. It may be faster.

Now, if relativity states time dilation slows clocks (from the point of view of Earth-based observers), this is something we can agree upon and take into account. This is not clock imprecision of random loss (or gain) of time. It has in fact and must be taken into account for the GPS system to work at all.

See: https://physics.stackexchange....