The way some of the media report on climate change can be simply stunning. For example, an opinion piece in The Financial Post has the headline "New, convincing evidence indicates global warming is caused by cosmic rays and the sun — not humans".

There’s only one problem: that’s completely wrong. In reality the study shows nothing of the sort. The evidence, as far as the limitations of the experiment go (that’s important, see below), do not show any effect of cosmic rays on global warming, and say nothing at all about the effect humans are having on the environment.

What did you do, Ray?

OK, first things first: why should we even think cosmic rays might affect climate? There are several steps to this, but it’s not too hard to explain.

We know that clouds form by water molecules accumulating on seed particles, called condensation nuclei. The physical processes are complex, but these particles (also called aerosols) are suspended in the air and water droplets form around them. The more of them available, the better water can condense and form clouds (although of course this also depends on a lot of other things, like how much water is in the air, the temperature, the height above the ground, and so on).

Cosmic rays, it turns out, may play a role in this too. They are subatomic particles that zip through space at high speed. We are bombarded by them all the time, in fact! They hit atoms and molecules in the Earth’s atmosphere, depositing their energy there. This affects aerosol formation rate, and therefore might affect cloud formation. Clouds are bright and white, and reflect sunlight. Therefore they affect global warming.

So the whole idea goes like this: the more cosmic rays there are, the more aerosols are made, the more easily clouds can form, the more sunlight gets reflected back into space, and the less global warming we get. It’s controversial, for sure (Discover Magazine interviewed a proponent of this idea in 2007) but worth looking into.

ConCERNing clouds

In practice, the actual connection between cosmic rays and cloud formation is really hard to determine. So a group of scientists at the European particle lab CERN decided to test the basics. They created a cloud chamber, bombarded it with cosmic rays, and examined the results. They found two very interesting things:

1) The number of aerosols created went up vastly as the particles blasted the chamber. That would seem to indicate that cosmic rays really are tied to global warming. Except…

2) The actual total number of aerosols created was way below what’s needed to account for cloud formation. Sure, there were more aerosols, but not nearly enough.

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I’ve been scratching my head for a long time, trying to figure out why NASA hasn’t been taking the idea of preventing asteroid impacts more seriously. This idea has everything you’d want in a project: it’s cool (I mean, c’mon, we’re talking asteroid impacts!), it’s doable, it’s not terribly expensive, it’s already on the public’s mind thanks to Hollywood, and there’s always the eensy-weensy possibility that you might save all of humanity.

Yet, despite this, it’s been an uphill battle to get NASA to pay attention. While the space agency has been very good about supporting early detection programs, the support for a space mission to prevent an impact has been lacking. Of course, given their relatively small budget (<1% of the federal spending) I imagine taking on anything like this would be difficult.

So I’m pretty chuffed that the European Space Agency is looking into saving our collective skins. They’ve being studying the feasibility of a mission to test methods of asteroid impact mitigation, including a very very cool space mission they’ve dubbed Don Quijote (first proposed in 2002, and may launch sometime after 2020). It’s actually two separate spacecraft: one to impact a small near-Earth asteroid, and another to monitor the event carefully to see what happens, including how much the orbit of the asteroid was changed.

The idea here isn’t complicated: if we see an asteroid on an impact trajectory with Earth, we want to change the orbit so it doesn’t hit us. We could try blowing it up, but that’s actually a bad idea: at best it creates a lot of debris that can still smack into us, some of which may still be big enough to do us serious harm. So a better idea is to make sure it doesn’t hit us at all.

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Is this the greatest t-shirt idea ever thunk up? Why yes. Yes, it is.

That is Zach Weiner’s latest idea, which he claims is based on this Saturday Morning Breakfast Cereal strip, though it’s closer to this one, but of course is in reality based on my book.

And will I be getting one? Duh.

A giant impact from an asteroid or comet can ruin your whole day. Or year. Or, if you’re a dinosaur, your existence.

So astronomers do what they can to understand this menace from space. We look for rocks on orbits that intersect ours, we think about ways of moving them out of the way should we find one, and we also think about the record we do have of past impacts to see what we can learn from them.

There are about 180 impact craters known on our planet, ranging from tens of millennia in age to billions of years. They also vary in size from a few kilometers across to monsters so big they can only be detected from space. Sometimes it’s hard to measure their size (they can have multiple concentric rings, or be underground — covered up due to extreme age — making definite sizes hard to figure out) or hard to get their age. But we do have some statistics on them, and there have been many studies about them.

A big question is: are impacts periodic? That is, do they happen with some repeating period? If so, then there must be some astrophysical cause: a giant planet in the outer solar system, for example, that shakes loose comets every 50 million years, or the Sun passing near another star. This has been studied, and all kinds of periods have been found in the data. I’ve always been a little skeptical of them, since the data are sparse. And now it looks like my thoughts are being supported: a new study finds no such pattern in the ages of craters, and concludes all the periods found previously are probably due to errors in the analyses.

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A pair of astronomers monitoring an all-sky camera got a surprise (PDF) when they checked data from last February: a half dozen meteors all seemed to come from the same spot in the sky, indicating they all had a common origin. After doing some calculations, they found that they probably come from a parent comet with an orbit that’s at least 53 years long. Moreover, the orbit of this comet crosses that of the Earth, meaning we may have a close encounter with this object sometime in the future.

And because I can sense the oncoming panic on the web over this news, let me break it down for you. I’ll give you the science (which is cool), how we know this unseen comet may be potentially, um, interesting, then the reason you don’t need to run around in circles screaming (spoiler: it’s rude to others nearby, but also unnecessary).

But just to be up front: should you panic? Nope. We know there are objects out there that could hit us in the future sometime. This comet is in many ways just another one. As I’ll point out below, we pass through lots of meteor streams, so there are plenty of other comets that could hit us. I know, I know, that doesn’t sound reassuring, but think about it: how often is the Earth hit by a comet? Not very often, despite having a few on the list of Potentially Hazardous Objects. So having one more we know about out there isn’t great, but in reality doesn’t really make things any worse for us.

Meatier showers

That picture above is one of the meteors in question. You can see the streak as the tiny bit of rock (probably the size of a grain of sand) glowing as it rammed through the Earth’s atmosphere at about 35 km/sec (22 miles/sec, or nearly 80,000 mph). If you go out on any dark night, you’re bound to see the random meteor or five. But meteor showers are when we see lots of them in a short time, and they occur when the Earth passes through the dust debris left behind by a comet.

Most comets are dirty snowballs: dust, pebbles, and boulders held together by ice (water ice, but also frozen carbon dioxide and other things we normally think of as gases). This makes comets the litter bugs of the solar system, shedding material when the Sun warms them up and turns the ice into gas. The vapor blows off, and the looser material forms a ribbon or stream that stays more or less along the same orbit as the comet.

If the path of the comet intersects the orbit of the Earth, we plow through that material at the same time every year. (more…)

A rock about 10 meters in size will fly past the Earth Monday at 13:30 UTC (09:30 Eastern US time) 17:01 UTC (13:01 Eastern US time) [Note: the time of closest approach was updated this morning, June 27]. It’ll be a particularly close shave — passing just 12,400 km (7430 miles) from Earth’s surface; a bit less than the diameter of the Earth itself — but it’ll miss for sure.

[Update 2: Images and an animation of the asteroid are now up at the Remanzacco Observatory blog; thanks to NickAstronomer on Twitter for the tip!]

We’re in no danger from the asteroid, named 2011 MD, since there’s essentially zero chance it will hit us. Even if it did, it’s too small to impact the surface, and would instead break apart and burn up in the atmosphere. That would be exciting, and make quite a show, but that’s about it.

Here’s a diagram of the asteroid’s trajectory (note that the size of the Earth is not to scale!):

On this scale, the Earth is actually about half the size shown; it was enlarged on the diagram to make it clear. In this smaller diagram here the trajectory is shown from a different angle (edge-on to the Moon’s orbit) with the Earth to scale, and you can see better that 2011 MD will miss us.

You can really see in those diagrams just how much the Earth’s gravity bends the orbit. At this close an approach the Earth’s gravity is significant, and the path of the object will be significantly altered. Just how much it’s changed is difficult to know until observations are made after the event. However, I’ll note the asteroid will be on the daylit side of Earth after it passes, making observations a bit tricky. I expect radar observations will be made using radio telescopes, which don’t need darkness to work and can provide very accurate measurements of the orbital path.

Speaking of orbits, this one is interesting. 2011 MD’s orbit is quite similar to Earth’s around the Sun, taking 396 days to go around once. The orbit is more elliptical than Earth’s, with a semi-major axis of 1.056 AU.

What does that mean? (more…)

Much ado was made over the recent news that the Sun’s magnetic activity may be cooling off over the next few years. Can this mean the Earth itself will literally cool off, slipping into an ice age? Some news sites are reporting it that way (of course, the execrable Daily Mail uses the headline "Earth facing a mini-Ice Age ‘within ten years’ due to rare drop in sunspot activity"; which isn’t even within a glancing blow of reality).

The answer — spoiler alert! — is almost certainly "no". I want to make sure that’s clear, because I will bet essentially any amount of money that some climate change denial sites will run with this story and claim that we don’t need to worry about global warming. That’s baloney, and what follows is why. The reasons take a minute to explain, but of course that’s where the cool stuff (haha!) is. So let’s take this one step at a time. And if you have the attention span of an E. coli bacterium, you can skip down to the conclusion section.

[Note: a lot of this is taken from my book "Death from the Skies!", where I interviewed approximately a bazillion people. One in particular was Caspar Ammann, who was very helpful in explaining the solar connection with the Little Ice Age to me.]

The Quiet Sun

The Sun has a magnetic cycle, its magnetic field waxing and waning in strength roughly every 11 years. The strength and complexity of the solar field governs a lot of the surface activity, including sunspots, solar flares, prominences, and coronal mass ejections.

Right now, in 2011, we’ve just left a period of an extended minimum, and the next max is due in late 2013 and early 2014. But scientists studying the Sun have seen three independent lines of reasoning indicating that the next rise to the solar peak, in 2022 or so, may be delayed or even not occur at all. I wrote about this in an earlier post, so you can get the details there. It’s the core of the "oncoming ice age" claim, so you should read it.

I’ll note right off the bat that not everyone agrees with these findings. Doug Biesecker, a solar physicist NOAA Space Weather Prediction Center [full disclosure: Doug is an acquaintance of mine; I interviewed him for an episode of "Bad Universe" about solar storms] , has written a document calling the findings into question. It’s not exactly a rebuttal; it’s more of a warning not to over-interpret the results. He also points out that a weak cycle may not have an effect on our climate; we simply don’t know for sure.

At this point you may be asking, so what? If the Sun has fewer sunspots and no flares, what difference does that make here on Earth? And how could it possibly trigger an ice age?

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