Starts With A Bang! » Life http://startswithabang.com Ethan Siegel's blog/video blog about Cosmology, the Universe, and everything else Sat, 04 Apr 2009 20:12:38 +0000 http://wordpress.org/?v=2.3.2 en It Begins… http://startswithabang.com/?p=1704 http://startswithabang.com/?p=1704#comments Mon, 30 Mar 2009 20:22:00 +0000 ethan http://startswithabang.com/?p=1704 Well, it’s happening this week, folks! I’m going to make the move over to ScienceBlogs this week, and I will have a special good-bye video post this Wednesday.

In the meantime, to help you cope with your sadness, Ian O’Neill at AstroEngine has this week’s Carnival of Space, and I have an example of artificial selection for you, duck-style:

The ones who are good at navigating metal grates survive to adulthood; the others, not so much. Yikes.

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Between Bird and Mammal Lies the 6th Sense… http://startswithabang.com/?p=1662 http://startswithabang.com/?p=1662#comments Mon, 23 Mar 2009 20:45:53 +0000 ethan http://startswithabang.com/?p=1662 This Australian “mammal” is one of the most bizarre creatures on Earth, having many of the characteristics usually reserved for either birds only or mammals only:

Ladies and gentlemen, the duck-billed platypus! Its most notable features are as follows:

1. It lays eggs. This is usually reserved exclusively for birds, reptiles, dinosaurs, etc. And these eggs are tiny! Mammals gestate with the eggs inside of them, giving birth to live young, but here’s a mammal that lays eggs!

2. It’s furry. Like mammals are — no feathers for this guy — the platypus is not only covered in fur, it’s got such a nice coat that it has historically been hunted for its fur!

3. It is venomous! This is extremely rare for mammals, and the platypus itself has three venomous compounds in it that are unique in all of nature to the platypus itself. The venom is emitted through a spur in the platypus’ foot, right around its ankle. And speaking of feet…

4. It has otter-like feet. Totally mammalian, you got it. On the other hand…

5. It has a duck-like bill. Totally bird-like, of course. On the other hand…

6. It has a beaver-like tail. Mammalian, I got it. I suppose we can go on and on, listing all the ways this animal is neither bird nor mammal, all of which I find fascinating. But this animal can do something that you and I cannot, no matter how hard we try. Your skin, your epidermal layer, is fantastic for sensing temperature, pressure, and pain. These three types of sensor suit us remarkably well, and allow us to experience all sorts of interesting sensations, like itch and ticklishness. But the platypus has us beat, because in addition to these, the platypus can detect electricity!

That’s right, the duck-billed platypus has the most sophisticated sense of “electroreception” of any mammal, allowing it to track its aquatic prey by locating where an electrical stimulus resulting from muscle contraction came from. Normally, we only see this in predatory fish, like I’ll show you in the image below:

But here it is, in a platypus! How cool of a sense is that?! So the next time someone tells you about “the sixth sense,” don’t think of ESP and don’t think of Bruce Willis, think about the platypus, an animal with a real sixth sense: the ability to detect electricity!

Because I want a sense like that…

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How Quickly do Humans Evolve? http://startswithabang.com/?p=1506 http://startswithabang.com/?p=1506#comments Mon, 16 Feb 2009 21:35:50 +0000 ethan http://startswithabang.com/?p=1506 One of the worst arguments out there against evolution is that we can see micro-evolution, in simple organisms, but not macro-evolution, or evolution in large plants and animals with long lifetimes. Therefore, the faulty argument goes, since we haven’t observed it directly, there’s no evidence for it. Let’s take a look at the obvious flaw in this argument:

Scientific studies have only been around for a few human generations. Evolution takes many generations to have visible effects. Something like a bacterium can reproduce so quickly that in just a few months you can have in excess of a hundred-thousand generations! So it’s very easy to observe evolution for microorganisms, since we have so much generational time to see change over time. This is much harder in longer-lived organisms. In humans, for instance, a typical generation is about 25 years. So while you get millions of generations for a microorganism, you only get one for humans and only a handful for even small mammals. So that logic is completely faulty.

Nevertheless, perhaps we can, if we’re clever enough, find evidence for the evolution of humans in our history. Human history goes back a long time, and if we study it properly, perhaps we can find something that shows how human characteristics change over time. As reported on MSNBC, changes in human DNA (as shown from human skeletal remains) have occurred about 100 times more quickly in the past 10,000 years than at any time in human history:

John Hawks, a professor at UW-Madison (shout-out!), rejected the assumption that human evolution ceased roughly 50,000 years ago, and working off of a sample of 35,000 years of skeletons from all around the world, uncovered the following:

In Europeans, the cheekbones slant backward, the eye sockets are shaped like aviator glasses, and the nose bridge is high. Asians have cheekbones facing more forward, very round orbits, and a very low nose bridge. Australians have thicker skulls and the biggest teeth, on average, of any population today.

“It beats me how leading biologists could look at the fossil record and conclude that human evolution came to a standstill 50,000 years ago,” Hawks says.

By his account, Hawks’ theory of accelerated human evolution owes its genesis to what he could see with his own eyes. But his radical view was also influenced by newly emerging genetic data. Thanks to stunning advances in sequencing and deciphering DNA in recent years, scientists had begun uncovering, one by one, genes that boost evolutionary fitness. These variants, which emerged after the Stone Age, seemed to help populations better combat infectious organisms, survive frigid temperatures, or otherwise adapt to local conditions. And they were popping up with surprising frequency.

The general rule here, that I love, is “adapt to local conditions“. What’s one of the simplest adaptations to local conditions in any living organism? The ability to blend in with their environment. The most stunning example is probably the chameleon, which can even adapt to change its color to match whatever it’s up against:

Does this work in humans? Could our huge variety in skin color be due to local adaptations? And if so, could we use this as evidence for human macroevolution?

Well, as reported by NPR, the answers are yes, yes, and yes! According to their research, changes in human pigmentation take only 100 to 200 generations, which is as few as 2,500 years. They specifically cite India as their example, that a few thousand years ago, when they lived farther to the North, their skin was much lighter, and has darkened dramatically over the past few millennia as they’ve migrated back to the south, to warmer climates.

Now, here’s a kicker: we already know why changing pigment is important for humans! From the NPR article:

“Humans started in Africa,” Jablonski says, the part of Africa near the equator where it is intensely sunny with lots of ultraviolet light.

Ultraviolet light, or UV, in high doses can age the skin and damage the DNA molecule, which makes it harder to build a fetus. Not to mention that ultraviolet light can sometimes cause skin cancer.

On the other hand, if a human is plopped down in, say, Norway, where the days can be short and there is precious little ultraviolet light, this creates problems, too. All vertebrate animals need ultraviolet light to help produce vitamin D. Vitamin D helps us absorb calcium from our food to build strong bones. If we don’t get enough ultraviolet light, we’re less likely to survive to reproductive age to produce strong-boned babies.

Thus the dilemma: People who live in sunny climes around the equator have too much UV. People who move away from the equator eventually have too little UV.

In fact, take a look at this map of UV radiation on Earth. How well do you think it will match the native population of that area?

Breathtaking, isn’t it? According to UV data alone, Australian Aboriginals and Africans should be the darkest, people from northern Europe, Asia and Canada should be the lightest, and Native Americans, those from the middle east (like me, ancestrally), and equatorial Asia should be in between. Sound like any world that you live in?

But science is even cooler than just this. Because we can make a computer model to simulate how the evolution of something like pigment works. We don’t need to simulate melanin or anything that complex, we can do it for a single-celled organism. If you have 10 minutes (and if you’re at work, feel free to turn the sound off; it’s just music), have a gander at how this works:

And while you’re here, I’d like to point out two things. First, I was asked a while ago where to go for educational science information on physics, astronomy, the natural world, etc. The National Geographic Channel has been putting out some good stuff recently. It seems like practically every Sunday night, starting at 8 PM ET/PT, they have a really interesting new science program on. This past Sunday, they had a 3-part program called Known Universe, where they talked about some of the biggest, smallest, fastest, and most extreme things we’ve ever discovered or created in the known Universe. This is great and rare, because it actually addresses things we know for certain, not only speculative theories or those for which there’s insufficient evidence. Yes, they have discussions about what may come next, but they’re well-done and reasonable, and it’s the things we already know that’s the (well-deserved) focus of the show. I’m really happy about it, and I regret not advertising it sooner. But look for it; it’s worth watching.

And second, the new Carnival of Space is up, just in time for… uhh… next year’s Valentine’s Day? Happy Monday, folks.

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There isn’t enough punishment for this http://startswithabang.com/?p=1480 http://startswithabang.com/?p=1480#comments Mon, 09 Feb 2009 22:25:22 +0000 ethan http://startswithabang.com/?p=1480 I normally try to keep my nose out of areas where I’m in over my head. In other words, there are areas where I’m an expert, and there are areas where I keep myself as informed as I can, but I have to rely on experts for their information. For instance, if you wanted to know about dark matter in our own galaxy, you should definitely come to me:

I’ve got expert knowledge on this, I’m familiar with what makes my findings scientifically rigorous and valid, and I know how to draw responsible conclusions based on the data in front of me. It is completely unreasonable to expect someone who isn’t an active researcher in theoretical astrophysics and cosmology to be an expert in the same way I am.

And by the same token, there are areas where I’m not an expert, such as what the incidences, symptoms, and causes of autism in children are:

So, to be informed, it should be reasonable for me to rely on the scientific findings of experts in that particular field of medical research. Now, I’ve talked before about the importance of being a good scientist, especially when your research can affect the health and well-being of others. So without further ado, I’d like to introduce you to someone you may not have heard of (unless you’re a huge fan of Bad Astronomy), Andrew Wakefield.

To give you the extremely quick version: in 1998, Dr. Andrew Wakefield published a very controversial paper following 12 children’s conditions at a clinic. His conclusion was that eight out of the twelve developed symptoms of autism after receiving their Measles, Mumps, and Rubella (MMR) inoculation. Since that piece of research, many millions of dollars have gone into researching the possibility of a link between vaccines and autism. Thousands of children have not been inoculated out of a fear of developing autism, and a few of those children have died as a result of contracting a disease for which a simple vaccine exists. There has been a huge grassroots movement that has sprung up among parents of autistic children, blaming the vaccine for their woes:

Now, over the last 11 years, overwhelming evidence has shown up that there is no link, not even a correlation (much less a causation) between vaccines and autism. But this past Sunday, an article came out in Wakefield’s home country of the UK, declaring the following:

MMR doctor Andrew Wakefield fixed data on autism


What? We have not just a scientist, but a medical doctor dealing with one of the fastest growing epidemics in medicine, falsifying results? And publishing them in a medical journal (the Lancet)? Remember that “eight out of twelve” statistic I quoted you earlier? Here’s what we get, upon further review:

Our investigation, confirmed by evidence presented to the General Medical Council (GMC), reveals that: In most of the 12 cases, the children’s ailments as described in The Lancet were different from their hospital and GP records. Although the research paper claimed that problems came on within days of the jab, in only one case did medical records suggest this was true, and in many of the cases medical concerns had been raised before the children were vaccinated.

The details are even worse. It turns out that after Wakefield’s “suggestion” that MMR, bowel disease/inflammation and autism were linked, the children were re-examined and diagnosed with these new bowel problems. I was unable to find US data, but in the UK, the number of confirmed measles cases in 2008 was 1,346. Want to know what the number of cases was in 1998, the year Wakefield’s paper was published? 56. One scientist’s false data has led to the resurgence of a disease that should be eradicated by this point. Nice move, Andrew, seriously.

That said, autism is a serious problem. We don’t know what causes it, we don’t know why the incidence of autism is so much higher than it’s ever been in the past, and these are things that need further investigation, absolutely. But not on a foundation of lies. And not by searching for a link that doesn’t exist with vaccines. Let’s do everyone justice, and have some sort of accountability for doctors and scientists who, through their actions (whether through ethical incompetence or unethical falsification), cause unnecessary death and disease among the general populace.

If you’re going to accept being lauded as an expert, you have to accept the responsibility of being an expert. Be honest. Be ethical. Or go do something else.

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How Many Intelligent Worlds Are There? http://startswithabang.com/?p=1478 http://startswithabang.com/?p=1478#comments Fri, 06 Feb 2009 09:05:10 +0000 ethan http://startswithabang.com/?p=1478 Looking at our galaxy, and knowing there are hundreds of billions of stars in it, I can’t help but wonder how many other worlds there are out there like Earth. I wonder how many other rocky planets are close to their stars, I wonder how many of those planets have life, I wonder how many of those evolve intelligent life, and I wonder how many of those (if any) are still around today.

The problem is, if you want to estimate this, there are too many unknowns to actually make a reasonable estimate. I point you to two recent articles from the BBC. First up:

Number of alien worlds quantified

Intelligent civilisations are out there and there could be thousands of them, according to an Edinburgh scientist.

The current research estimates that there are at least 361 intelligent civilisations in our Galaxy and possibly as many as 38,000.

Sounds like groundbreaking, supremely optimistic news! Other intelligent civilizations in our own galaxy, woohoo! But wait, what was that second recent BBC article I was referring to? Oh right, this one:

Odds on finding aliens ‘too low’

Scientists have counted out the chance of finding advanced alien life during the life-time of the Earth.

Prof Watson suggests four numbers of evolutionary steps are needed to create intelligent life in the case of humans. “These probably include the emergence of single-celled bacteria, complex cells, specialized cells allowing complex life forms and intelligent life with an established language.” His model, published in the journal Astrobiology, suggests… the chances of intelligent life emerging is low - less than 0.01 per cent over four billion years.

Why is there this discrepancy? Why isn’t there any agreement? Because while everyone agrees as to the steps that humans took in order to get here, we have no reference to how likely each of those steps is to have happened. For example, we know a little bit about how many other planets are out there, and we know a little bit about how life evolves once it’s begun, but here is a short list of questions we really have no idea about:

  1. How likely is it that life spontaneously arises from non-living things? This happened pretty quickly on Earth, as there is evidence that the first living things evolved on Earth nearly 4 billion years ago. But we don’t know how likely it would be to happen again if we started with similar initial conditions.
  2. Once life exists, how likely is it that sexual reproduction evolves? This is really a necessary step to creating complex life, because asexual reproduction with random mutations is far too slow of a mechanism to evolve complex life. It took Earth nearly 3 billion years of having asexual, living organisms to evolve gender.
  3. How likely is it that intelligent life evolves? Not just intelligent life, but technologically advanced (i.e., late 20th century Earth technology or later) enough to contact another world and receive a message sent at them. Estimates of this one seem to range incredibly far and wide, from as high as about 10% to as low as about one-in-many-millions.
  4. And on all of these planets, where all this is possible, how many of them will have this happen before their star gets too hot to allow life to live anymore? The Earth was good for the first 4.5 billion years or so, but we’ve only got another 1 billion left until the Sun’s solar output boils the oceans.

My estimate is that there are about 1 million Earth-sized planets in or near a habitable zone around their stars in the Galaxy. What are the chances that all of the above steps will then happen? Is it a 20% chance for each step? A 1% chance? A one-in-a-million chance? We have no idea. None.

And anyone who tells you differently is probably trying to sell you something. Don’t buy it. Admit that we don’t know, because we haven’t done the science, and that all of this is speculation. I’m not saying it isn’t interesting, I’m just saying it isn’t science. (Not yet, anyway.) I know I’ve used this image before, but you might as well just listen to Max Cannon:

And if you want to see a few more interesting space stories from the past week or so, check out the latest Carnival of Space; this one’s pretty good! Thanks to The Space Writer for putting it together!

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The Physics of Geckos http://startswithabang.com/?p=1459 http://startswithabang.com/?p=1459#comments Mon, 02 Feb 2009 20:12:15 +0000 ethan http://startswithabang.com/?p=1459 Sure, geckos are cute little lizards. They’ve even been made famous in households across the country by certain car insurance companies. But geckos are pretty miraculous in a way that would make even Spider-Man jealous:

Geckos can climb almost anything. Pretty much any surface, however slick, sheer, or wet, can be climbed upon by a gecko, whether completely upright, inverted, or even upside-down. If you live in a tropical climate, you may even notice geckos running rampant on your ceiling:

But unlike common adhesives, such as tape or suction cups, geckos work in a far more sophisticated way; let’s find out how.

The key lies in the way the gecko’s feet work. Unlike other animals, each toe of a gecko’s foot contains hundreds of thousands, if not millions, of tiny, tiny hairs known as setae. These setae are only a tenth of a millimeter long, or about half the size of a typical paramecium.

What’s even more amazing is that each single seta, as you can see above, branches into about 1,000 different endings, each one ending in a tip known as (no joke) a spatula. These spatulae are so small that they can’t be seen with visible light; it takes ultraviolet light just to see these things, which measure in at just about 0.2 microns apiece.

So, on average, each one of a gecko’s four feet contain about a billion of these microscopic spatulae. But what makes them so special? Van der Waals forces. The way these work is pretty simple, and it works similarly to how you can rub an inflated balloon on your cotton shirt, stick it to the wall (or your hair), and have it stay, held up by static electricity.

Well, Van der Waals forces work the same way, except the edges of the spatulae get a random charge, either + or - on the tip. When they come near a surface, it causes a charge separation on the surface, and this makes a small, close-range, temporary attraction, like so:

When you get many of these together, they can form a lattice, and result in an extremely large force. The charges will change over time, but as long as they all change together, the attractive force will remain strong, and thus the gecko will remain stuck to the wall.

There’s one exception, though. What if there were a material that didn’t allow charges to separate? What if there were a material that was immune to forming these induced charges? Well, there is, and it’s teflon. Its molecular structure is so stable (thanks to the carbon-fluorine bonds) that the gecko’s spatulae can’t alter the electric charges at all, and hence there are no Van der Waals forces. (Alright, there are only very small Van der Waals forces, insufficient to allow a gecko to stick to it.) Teflon is the only known thing that a gecko cannot stick to.

And so what can we learn from this? Well, if you can reproduce this, if you can artificially build something with setae and spatulae on it, it could stick to just about anything, too, right?

Might as well see for yourself:

And that’s the physics of geckos. Better get those tiny hairs growing if you want to end up like Spider-Man, kids!

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The Solar System and the Greenhouse Effect http://startswithabang.com/?p=1398 http://startswithabang.com/?p=1398#comments Mon, 19 Jan 2009 20:43:53 +0000 ethan http://startswithabang.com/?p=1398 When people talk about global warming, they talk about the greenhouse effect and carbon dioxide. I realized, recently, that a lot of people still don’t believe that global average temperature and carbon dioxide levels are linked, despite a ridiculous amount of evidence clearly showing the link, like this:

Perhaps this will make sense to people if I explain it, clearly and simply, and perhaps this will help those of you who are interested readers to explain it clearly to others. Let’s show you the science of how the greenhouse effect works.

It begins in space: the Sun shines on the Earth. What’s the simplest thing that could happen? 100% of the Sun’s energy that hits Earth would be absorbed by the Earth, and then the Earth re-emits all of that energy back into space. This would give us nice, warm temperatures during the day, when the Sun shines on us, but freezing, abhorrently cold temperatures at night, where all we do is radiate our heat away. The temperature swing between night and day would be over a hundred degrees (Fahrenheit; it would be about an 80 degree swing in Celcius).

Luckily, this doesn’t happen on Earth. It happens on the Moon and Mercury, and even on Mars, but not on the Earth. Why not? Because Earth has this:

An atmosphere. A nice, thick, layered atmosphere. The atmosphere on Earth does two things: it keeps some of the light out, and it also keeps some of the heat in. Mercury and the Moon don’t have atmospheres, and Mars’ is so thin (only 0.7% as thick as Earth’s) that it can’t really do much of anything. The atmosphere on Earth means that instead of over a hundred degrees, the temperature difference between night and day is small. This is good.

But the atmosphere can lead to a greenhouse effect, which can be bad. Let’s take a look at how the greenhouse effect works. (See picture at right.) The Sun gives off light, most of which is visible to our eyes. Some of that light, when it strikes the atmosphere, gets reflected away off of water molecules, ozone molecules, and other particles. Some of it gets absorbed by clouds, and some gets scattered randomly. Some of these things happen whether there are clouds or not, others are very sensitive to the thickness and coverage of clouds. A thick cloud cover will block up to an extra 30% of the energy from the Sun and prevent it from reaching the Earth. Why are clouds so effective? Because the Sun gives off mostly visible light, and although visible light is sensitive to clouds, without them, it passes through the atmosphere, mostly unhindered. A typical day is shown below:

That’s the first part: the atmosphere preventing some light from getting through to the Earth’s surface in the first place. But when the Earth tries to re-emit that energy it absorbed, that light isn’t visible anymore: it’s infrared light, commonly known (and felt) as heat. When the Earth emits that heat, some of the heat gets absorbed by the atmosphere and re-emitted back down towards the Earth. That’s how the atmosphere keeps the heat in. So what’s the Greenhouse Effect?

The fact that the atmosphere will let visible light in pretty easily, but won’t let infrared light out. This is how a greenhouse works: it lets in the visible light and then reflects the infrared light around, keeping temperatures inside very warm even when it’s very cold outside. Carbon dioxide is so important because it’s really good at absorbing infrared radiation, and so the more CO2 there is in the atmosphere, the hotter the Earth is going to get. I thought you might need to see some numbers to help you see the effects that greenhouse gases can have; they don’t really affect how much light gets transmitted to the Earth in the first place, but they do affect how much heat gets kept inside. Numbers, anyone? I’m going to show three numbers: the percentage of light that gets to the Earth, initially, through the atmosphere, the percentage of heat that gets kept in by the atmosphere, and the total amount of energy relative to there being no atmosphere at all. Let’s have a look at what happens for just a little bit of greenhouse gas:

  • Light in: 70% Heat reflected (no greenhouse gases): 30% Total energy: 100%
  • Light in: 70% Heat reflected (slight greenhouse gases): 32% Total energy: 102.9%
  • Light in: 70% Heat reflected (moderate greenhouse gases): 35% Total energy: 107.7%
  • Light in: 70% Heat reflected (heavy greenhouse gases): 40% Total energy: 116.7%
  • Light in: 70% Heat reflected (extreme greenhouse gases): 50% Total energy: 140%

Just by adding more greenhouse gases, and doing nothing else, we could literally boil the planet. How do we know? We have an example in our Solar System:

Venus. The average temperature of Venus is higher than the hottest temperature on Mercury, even though Venus is nearly twice as far from the Sun as Mercury is! How is this possible? Let’s look at some estimated stats for Venus, which blocks more light but has a tremendous greenhouse effect:

  • Light in: 40% Heat reflected (Venus’ greenhouse gases): 90% Total energy: 400%

Venus is four times as hot as it would be if it didn’t have an atmosphere! And that’s why Venus is even hotter than Mercury — because of its greenhouse effect. And that’s why we need to be really careful about the amount of Carbon Dioxide, Methane, Water Vapor, and other greenhouse gases in our atmosphere! And we’ve already been over how to fix it:

Will we reforest our planet? Or will we end up like Venus?

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Did a Gamma-Ray Burst cause the Trilobite Extinction? http://startswithabang.com/?p=1358 http://startswithabang.com/?p=1358#comments Fri, 09 Jan 2009 17:23:11 +0000 ethan http://startswithabang.com/?p=1358 We could really devote an entire website to the bad and inaccurate science that they report on the History Channel. Earlier this week was a post for Debbie on the galactic eclipse, and today we have one for Lucas.

Apparently, Lucas was watching the history channel, and he saw a scientist contend that a Gamma-Ray Burst wiped out the trilobites, and that another one could be waiting for us to wipe out humanity. Yes, History Channel really seems to be pining for the destruction of the world, I know. But is there any merit to their contention: could a Gamma-Ray Burst have destroyed the trilobites? Let’s take a look; first at the trilobites.

These were insect-like/crustacean-like creatures that ranged from being just an inch or two long to up to three feet long. They lived on Earth for about 200 million years, finally going extinct at the end of the Permian Era (right before the Triassic Era and the rise of the dinosaurs), when there was a mass extinction even more catastrophic than the one that wiped out the dinosaurs. This one, the Permian Extinction, happened about 250 million years ago. The cause of the Permian extinction is still up for debate, and there’s an excellent book on the topic called When Life Nearly Died.

There doesn’t seem to be evidence for a great asteroid impact, like the one that destroyed the dinosaurs. Instead, the four leading theories are all events that just occurred naturally on Earth: two are theories that involve an extensive increase in glacier-formation and coverage of the planet, one is a severe amount of volcanic activity in siberia, and another is the effects that the formation of the supercontinent Pangaea had on oceanic life.

Notice what isn’t on any of these lists? A Gamma-Ray Burst. Why not? Let’s look at what Gamma-Ray Bursts are:

When stars die, they typically expand and give off a lot of energy. If a star is large enough, the core will collapse and a tremendous amount of energy will be released in a supernova explosion. This is so powerful that a single supernova will be brighter than an entire galaxy full of hundreds of billions of stars! But the very brightest supernovae, the biggest stars that explode, can produce ultra-powerful jets that shoot out in opposite directions. If one of those jets (which are really narrow, only about one degree wide) is pointed directly at us, we get bathed in a whole lot of extra energy even beyond what a supernova can do, and that’s called a gamma ray burst.

Well, this is possible, of course. There are hundreds of billions of stars in our galaxy, and we get about one supernova every 100 years. Surely one of them would have made a gamma-ray burst that would have hit Earth, right?

Not even close. We can compute how often gamma-ray bursts happen. Very, very few supernovae are large enough, powerful enough, or the right type to produce a gamma-ray burst. As far as we can tell, maybe only one in 1,000. Furthermore, gamma-ray bursts are extremely rare in older galaxies like ours; nearly all of the ones we see occur in very young galaxies. (For you technical kids, we can tell that galaxies are older by how much carbon, oxygen, nitrogen, and other heavier elements they have. We’ve got an awful lot in ours.) Let’s assume this makes it 5 times less likely that we’ll have one than normal. Only about 1 in 3,000 gamma-ray bursts that do occur will have their narrow jets pointed at Earth, assuming that the gamma-ray bursts have jets that are three degrees in diameter. And finally, if you want to affect life on Earth, the gamma-ray burst needs to occur within 6,000 light years, otherwise it won’t be close enough to have the energy to disturb us. 6,000 light years means we can get about one-tenth of the galaxy.

Put these numbers together, and how often do we expect a gamma-ray burst to affect life on Earth? Once every 15 billion years. FYI, 15 billion years is older than the age of the Universe, and about 3 times older than the Earth itself. So no, it’s really unlikely that we’ve ever gotten hit by an extinction-caliber gamma-ray burst, and there’s no evidence that one ever happened on Earth.

But the History Channel threw in one last zinger: that the star WR 104 may make a gamma-ray burst that destroys all life on Earth.

Jerks. This makes me mad! Know why? This star is 8,000 light years away, which means it’s too far to affect life on Earth even if it does make a gamma-ray burst (possible, but not a certainty) and even if one of the jets points at Earth (not likely, but again, about a 1 in 3,000 chance).

So although there’s no way of knowing for sure, there is no evidence that a Gamma-Ray Burst caused the trilobite extinction, and there is plenty of evidence that either glaciation, volcanism, or the formation of Pangaea caused it instead. There’s also no chance that a Gamma-Ray Burst will wipe out life on Earth in the near future, because we don’t have a star powerful enough that’s close enough to us to do the job. And that’s all I’ve got on this one, Lucas. Hope it helps you sleep better at night!

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The Worst Scientist in History http://startswithabang.com/?p=1319 http://startswithabang.com/?p=1319#comments Tue, 30 Dec 2008 00:14:22 +0000 ethan http://startswithabang.com/?p=1319 There are many great, elegant, and simple theories and ideas that attempt to make sense of this Universe. Above all, many of these ideas are beautiful, and often the people who come up with them are brilliant.

Almost all of these great, elegant, and simple theories are wrong. This is important to remember and difficult for many scientists to accept. Most theories, no matter how well-conceived or how brilliant they are, will eventually fail to an experimental test that does not yield what the theory predicts.

The key, and this is a really hard part for anyone with an ego (and I am just as guilty of this as any other scientist), is admitting when your brain-child, your theory, is wrong. There are plenty of examples of this: Halton Arp and Fred Hoyle refusing to let go of their incorrect theories when it was shown that their theories were invalid and the Big Bang was more correct, Howard Georgi going into a deep depression when the proton didn’t decay as predicted by his theory of Grand Unification, and even Einstein refusing to abandon his idea of a classical unification of E&M and Gravity, ignoring all of the evidence for quantum theory.

Normally, when this happens, you have no reason to care. One person cannot hold up the scientific endeavor, cannot stop the tide of research and evidence as we gather more and more data and refine our understandings of the Universe. Science, technology, health, and medicine march forward.

Right?

Umm… right?

That’s what you think. Meet Trofim Lysenko. Biologist, agronomist, with a specialized interest and knowledge set in the field of inherited traits. Also, in my opinion, he is the worst and most dangerous scientist of the 20th Century. With his expert knowledge and status, he was able to promise increased crop yields following the famines and drop in food production in the USSR in the 1930s. In 1940, he was appointed director of the Institute of Genetics within the USSR’s Academy of Sciences, a position he held for 25 years.

What makes him the worst scientist in history? He was a denier of science. Despite overwhelming evidence in support of Gregor Mendel’s theory of genetics and inherited traits, Lysenko stuck to his own theories of hybridization instead. Lysenko’s theories became widely accepted in the USSR, and in 1948, scientific dissent from his theory of hybridization was outlawed.

It was not until about 15 years had passed, and crop productivity had failed to improve, that people in power realized that Lysenko was not fairly considering all of the evidence. Modern agricultural techniques were eventually adopted and Lysenkoism fell out of favor. But science in that field, especially in the USSR, was set back a good 20 years by Lysenko’s denial of the evidence.

Well, I must say, it’s a good thing that there’s nobody with any political influence who can make huge mistakes on issues of science policy. It’s a good thing that, in the USA, the scientific community is always consulted for their expert opinion on matters of national and international importance. And it’s a good thing that the opinion of one politician or one rogue scientist can’t dictate policy.

Right?

Umm… right?

A-ha! Three more weeks, America, just three more weeks. I have hope that this time, we’re getting it right.

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Q & A: How to Fight Global Warming http://startswithabang.com/?p=1313 http://startswithabang.com/?p=1313#comments Fri, 26 Dec 2008 20:08:59 +0000 ethan http://startswithabang.com/?p=1313 People often write in wanting to know the answers to big questions. Earlier this week I got a message from kampfgestfj asking me about global warming. More to the point, he wanted to know the following:

Why are there still those that don’t believe global warming is affected by man’s input into the environment?

Now, I don’t have a good answer for this, because I don’t understand the reasoning behind denying mankind’s influence on global warming. For me, the scientific evidence is pretty straightforward: industrialization is at an all-time high, there are more pollutants in the atmosphere now than at any point in all of human history, and global average temperature has followed the trend of CO2 in the atmosphere over hundreds of thousands of years according to all reasonable tests of scientific rigor. (And yes, you have to include an appropriate time-lag of about 50-100 years for the full effects to be felt.)

But there is a new finding that I find absolutely delightful. Ever hear about the little ice age in Europe? A few hundred years ago, the temperature in Europe decreased by a little less than 1 degree Celcius, and remained that way for about 200 years. Have a look:

Well, we think we know why this happened. When the Europeans came over to America, the Aztec and Incan civilizations crumbled. This was due to many factors, including (and perhaps especially) disease. From when the Europeans came over in about 1500 to about 1600, the populations of the Incan and Aztec empires dropped by about 90%. This was about 9% of the world’s population, and it meant that about 500,000 km2 of land went from being used by humans to wilderness. At those latitudes, that means there was about 500,000 km2 of reforestation that occurred.

Now, as everyone knows, trees breathe in Carbon Dioxide and breathe out Oxygen. The researchers estimate that 10 billion tonnes of Carbon Dioxide was removed from the atmosphere by this reforestation, significantly contributing to the fall in global average temperature.

Even with accounting for volcanic activity and the Sun’s variation in intensity, the impact of humans, according to the study, was undeniably important. So if we want to fix our global warming problem now, what’s the answer?

Well, it’s simple. RE-forestation. This is a surefire way to remove significant amounts of CO2 from the atmosphere. But this is a huge policy problem: how can we not only keep humans out of habitable areas, how can we get humans to leave areas where they’re already living? We know the problem. We know how to fight it. We even know how to fix it. The big question is how do we make it happen?

And that’s one I don’t have an answer for, just hope that we’ll get it right, and soon.

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