The Total Package

Mano Singham and PZ Myers aren’t that interested in eclipses. I’m sort of the opposite, as a group of us drove 13 hours to reach totality, arriving only an hour and a half before the eclipse started… and departing for the return trip fifteen minutes after totality ended. Why the heck would anyone go to such extreme lengths for a few minutes of darkness?

The Corona

The solar corona is the hottest part of the sun we can see, far hotter than the surface, and we don’t know why that is. Despite being so hot, the corona is also very diffuse and thus the cooler chromosphere blasts out far more light than it does. This means you can’t see it if any part of the sun is visible, and the physics of choronographs means they block off significantly more of the corona than the Moon does during an eclipse.

While that’s all very nice and intellectual, there’s also something satisfying about looking up in the sky and seeing what looks like Albert Einstein being consumed by a black hole.

An image of the corona from "the Camera for Photographing Eclipse Photographic Collection."Mercury

The planet Mercury is likely the last visible-eye planet discovered. Because it clings so tightly to it, you need to blot out the Sun by exploiting sunsets and sunrises, and even then you need a view close to the horizon and the planet in a certain orientation. A solar eclipse accomplishes the same, only during the middle of the day. I’m not convinced I actually saw Mercury yesterday, as it was faint and appeared in the wrong spot too close to the sun, but oh well.

Sunsets on Every Horizon

I can verify this actually happens. The physics is pretty simple: the Moon’s shadow occupies a finite area. If you’re perfectly centred under it, every horizon is in the direction of a patch of earth which has at least some sunlight falling on it. That sunlight bounces back up into or scatters through the atmosphere, producing something that looks like a sunset. It is wicked cool!

Watching The Shadow

The shadow of the Moon is quite fuzzy, so if you’re expecting to see a sharp line you’ll be disappointed. The best view is definitely from space, though an airplane will do in a pinch; on Earth, I could spot the Eastern horizon getting gradually lighter even as we were in totality.

Shadow Bands

As NASA puts it, “Shadow bands are thin wavy lines of alternating light and dark that can be seen moving and undulating in parallel on plain-coloured surfaces immediately before and after a total solar eclipse.” Scientists aren’t entirely sure what they are, but the best guess is atmospheric cells warping light in a similar way to stellar flicker. They aren’t guaranteed to show up, but I insisted on laying out a white blanket to make them more visible. We missed seeing them as totality was approaching, but as the Sun started peeking back I strongly suggested everyone stare at the blanket. And we saw them!

A Chill In The Air

The Sun radiates a lot of heat our way, which is absorbed and scattered by the ground and atmosphere. Take away that source, and you’re just left with the radiation from said ground and atmosphere as it cools down. This is at its strongest during totality, and collectively we could feel the atmosphere was notably chillier just after the eclipse than it was in the lead up. I’m estimating the difference was about 5-10C.

People Losing Their Shit

My photos of the eclipse were pretty lousy, as I didn’t have any money to invest in the proper gear. Derek Muller of Vertasium was much luckier, but his video is more notable for the audio; he, and everyone around him, were losing their minds as they reached totality. You don’t get that from a partial solar eclipse.

Don’t listen to Singham or Myers. Total solar eclipses are the coolest, and if one happens to fall near you I recommend you take full advantage.

A Third One!

I know, I know, these are starting to get passé. But this third event brings a little more information.

For the third time in a year and a half, the Advanced Laser Interferometer Gravitational Wave Observatory (LIGO) has detected gravitational waves. […]

This most recent event, which we detected on Jan. 4, 2017, is the most distant source we’ve observed so far. Because gravitational waves travel at the speed of light, when we look at very distant objects, we also look back in time. This most recent event is also the most ancient gravitational wave source we’ve detected so far, having occurred over two billion years ago. Back then, the universe itself was 20 percent smaller than it is today, and multicellular life had not yet arisen on Earth.

The mass of the final black hole left behind after this most recent collision is 50 times the mass of our sun. Prior to the first detected event, which weighed in at 60 times the mass of the sun, astronomers didn’t think such massive black holes could be formed in this way. While the second event was only 20 solar masses, detecting this additional very massive event suggests that such systems not only exist, but may be relatively common.

Thanks to this third event, astronomers can set a stronger maximum mass for the graviton, the proposed name for any gravity force-carrying particle. They also have some hints as to how these black holes form; the axis of spin for these two black holes appear to be misaligned, which suggests they became binaries well after forming as opposed to starting off as binary stars in orbit. Finally, the absence of another signal tells us something important about intermediate black holes, thousands of times heavier than the Sun but less than millions.

The paper reports a “survey of the universe for midsize-black-hole collisions up to 5 billion light years ago,” says Karan Jani, a former Georgia Tech Ph.D. physics student who participated in the study. That volume of space contains about 100 million galaxies the size of the Milky Way. Nowhere in that space did the study find a collision of midsize black holes.

“Clearly they are much, much rarer than low-mass black holes, three collisions of which LIGO has detected so far,” Jani says. Nevertheless, should a gravitational wave from two Goldilocks black holes colliding ever gets detected, Jani adds, “we have all the tools to dissect the signal.”

If you want more info, Veritasium has a quick summary, while if you want something meatier the full paper has been published and the raw data has been released.

Otherwise, just be content that we’ve learned a little more about the world.