|The beauty of crystalline solids on the atomic scale. (cosmosontv.com)|
So if you're ready to learn more, but especially if you're not, click on through...
|As a general rule, nothing is this close together in space. (cosmosontv.com)|
Oh boy, here we go again with the asteroids. After the very first episode, I talked about the common misconception of the crowded, Star-Wars-style asteroid belt. Well, it showed up in this episode again, and it was accompanied by a few other inaccuracies. The first is depicted above, with multiple planet-sized objects accreting swarms of asteroid-sized debris all within a few diameters of one another. In reality, such large objects would not last long with such similar orbits. Their significant gravity would almost certainly cause them to either collide or scatter one another apart within a few years, which is far shorter than the time scale for such large objects to form. Given that this was approximately a ten second shot though, it's hard to claim that Cosmos intends us to believe that this is how it looked. It got the point across.
The second correction I have is a bit more mysterious. Why does Cosmos keep showing the asteroid belt as a crowded mess? We've seen it before, so now they can use the few seconds of screen time to explain that they're actually not crowded out there, I would think. The even more unnecessary and ridiculous mistake was that they explained the impact of the object that formed the amazing Meteor Crater in Arizona as the result of a soft jostling of one asteroid in the belt by another. This basically isn't a thing. Take a look at this plot of the distribution of collision velocities for the large asteroids in the belt from this paper.
The probability of a collision with a given velocity is proportional to the height of the graph over that velocity. Notice what's going on at low speeds? That's right, nothing. Collisions between asteroids are usually quite violent, with rifle bullet speeds at the low end of the possibilities. Given that the meteorite that caused the crater in question was about 50 meters across, the collision depicted in the episode would have been an improbably slow collision.
This type of slow (and highly unlikely) collision would alter the orbit of an asteroid only a tiny bit (certainly not enough to move from a near circular orbit in the asteroid belt to an orbit which plunged all the way to the Earth), so the asteroid would have to already be on an orbit that brought it close to Earth anyway. Given that the asteroid already comes near Earth in its orbit, there is a much more likely explanation of how it was tugged into a collision course with our home: The Earth!
Just as a few years ago there was a slight chance that the asteroid Apophis could have had its trajectory perfectly bent by the Earth into a collision a few decades later, the Meteor Crater rock (or chunk of metal, it turns out) was probably perturbed mostly by the Earth itself onto a collision course that terminated 50,000 years ago. It could also have been nudged by Mars, Jupiter, or Venus, or it could be a fragment of a larger asteroid blasted apart in a violent (and therefore much more likely) collision with one of its neighbors. One thing is almost sure, though: It was almost definitely not gently and subtly nudged by another asteroid onto a direct collision course with us. That kind of orbital mechanics only works in Michael Bay films.
The reason this bothered me is that they already used the example of an asteroid's gravity tugging another asteroid "a little to the left" a few billion years before it eventually ended the age of the dinosaurs, so they already had used a more reasonable approach. Why go back to the Hollywood version now? Puzzling.
|Thank you, Bishop Ussher, for taking your religion seriously. (cosmosontv.com)|
In 30 seconds or less, here's why I can't take the Bible on faith:
The Bible contains obvious false and conflicting statements, such as the value of pi (the circle constant, 3.14159...) is exactly 3 (Kings 7:23), and a surprising implication that the Earth is 6000 years old. We know better. Therefore, the Bible can't always be right (which I would be hard pressed to accept even if it wasn't obviously wrong about many things). If it is sometimes right and sometimes wrong, we need some way of determining which statements are correct. The way we do that is examine each of them critically and look for confirmation in other sources. There is no external evidence for any of the Bible's supernatural claims. Therefore, I treat the Bible like a Christian treats the Odyssey or the Iliad or the Bhagavad Gita.
I could go into detail (ahem, have you read my blog?), but that's the elevator version. Let's move on to a few other tidbits.
Saturnalia is the reason for season! Actually, it's axial tilt. Long ago, when people first began figuring out the order in the movements of the Sun and the Moon, they noticed that the days grow longer and shorter over the course of the year. The longest day, usually around my birthday of 21 June, is the Summer Solstice, and the shortest day is six months later, the Winter Solstice. These special days were as good a reason as any to throw a party, and so every culture has some kind of festival centered around these times. The reason that the days grow longer and shorter, you might remember from science class, is that the Earth's axis is tilted 23.5 degrees with respect to its orbit around the Sun. This leads me to my favorite holiday greeting card:
Lastly, I'll just mention that Meteor Crater is spectacular, and if you ever find yourself driving across the American Southwest, it's only a couple of miles off of Interstate 40. Standing at the edge of a kilometer-wide hole in the ground will give rise to questions of whether our space program is sufficiently more advanced than that of the dinosaurs.
|I totally had a math class in this building! (cosmosontv.com)|
I was completely unaware of the story of the age of the Earth and the dangers of leaded gasoline, which is surprising given that a good chunk of this story played out within a short stroll of my office. Clair Patterson's work is a wonderful illustration of how the search for an answer to an intriguing but seemingly useless question can often lead to amazing improvements in our daily lives. The technological challenges encountered in solving tough experimental, observational, and explorational problems drive the development of new techniques for manipulating our environment to suit our goals, which rarely has only a single use.
Think not only of measuring minute quantities of lead, but also of the search for an understanding of the motion of the heavenly bodies, which lead to our understanding of the law of gravity that permits satellite communications, GPS, and weather monitoring. Or think of the search for an understanding of anti-matter, which has given us PET scans that help diagnose and monitor the inner structure and function of our own bodies for medical purposes. Think of the study of energy transfer in materials, which lead to thermodynamics and eventually the entire industrial civilization. Now envision what wonders await us in the future for our work in "abstract" fields of research today, or at least try to, since if the comparison holds we'll be living in a world we can't even imagine in 100 years.
Lastly, it's important to draw the obvious parallels between the debate on lead in the '60's and the debate on carbon today. We have science on one side and money on another in both cases (coincidentally both involve the oil industry), with the status quo looking bright only for the near future, and mostly for the special interests, it's vital that we, not just scientists but humans, stand up for what precious little knowledge we've been able to defend from our self-made hailstorm of doubt. We must continue to make the arguments clearly and plainly, and to invite those with opposing views to subject their theories to the same scrutiny to which we subject our own. We must, because if we continue for much longer down the path of comforting self-deception, we'll have no recourse but to hope that the consequences of our continued forcing on the environment aren't as bad as we predict they will be. Given the incredible power of science to tease out the truth, I wouldn't take that bet. I guess you could say I remain conservative on the issue.