Archive for the 'Astronomy' Category

Creationist Double Fail

A common creationist objection to the theory of evolution is the orbital recession of the Moon. It is well known that the distance between the Earth and Moon is gradually getting larger. Every year, the Moon is roughly 3.8 cm farther away than it was the year before. What creationists claim is that if you run the clock backwards, and let the Moon approach the Earth at that rate, it ends up colliding with the Earth long before the supposed age of the Earth-Moon system, thus showing that the world couldn’t be that old.

The usual objection is over the past 4.6 billion years (the age of the Moon), the rate that it’s been moving away at hasn’t been constant. The mechanics of lunar recession is complicated, having to do with the distribution of oceans and landmasses on the Earth (different distributions produce different gravitational “tugs” on the Moon as it orbits). Today’s rate is actually quite a bit higher than it has been in the past. So directly extrapolating today’s rate into the past won’t actually give you the correct answer.

And then…there’s this:

The Moon is currently 385,000 km away (on average. The Moon’s orbit is actually somewhat eccentric).

385,000 km / 3.8 cm per year = 10.1 billion years. Far older than the accepted age of the Earth.

So even if you do blindly extrapolate backwards, the Moon doesn’t actually end up colliding with the Earth. So not only do creationists not do their research, they also suck at math!

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Alien Civilizations VII: Black Hole Power

Some of you might remember my posts about the possible existence of alien intelligence. Executive summary:

Alien civilizations will tend to expand rapidly over intergalactic distances, eventually sweeping over our solar system. Such intelligence will harvest any and all resources it can for its own use, and thus be harvesting the solar system. Thus, alien civilization, if it existed, would be blatantly obvious. It is not, therefore, alien civilizations are unlikely to exist.

Now with my recent realization about black hole power, I have come to refine my arguments about alien intelligence. 1) Since a black hole power plant would be, in theory, a 100% efficient matter-to-energy converter, it will be the preferred method for alien intelligences to use. 2) Obviously, matter to fuel the black holes will still be necessary, thus alien intelligence will likely still harvest as much matter as they can. 3) Black holes are much more ideal for energy storage than antimatter, since literally nothing can escape them (except for Hawking Radiation as described earlier).

So, my former conclusion still holds.

But I did realize something interesting. Let’s say there was an alien intelligence doing this. They are expanding at slower-than-light speeds across intergalactic space, basically making them look like an expanding sphere of darkness where they have enclosed stars with Dyson Swarms (or perhaps collapsed them into black holes). This is basically what we see in the universe today. Huge intergalactic voids with “nothing” in them. And between these voids are thin streams of galaxies.

I made this argument before, but discounted it because Dyson Swarms would still allow waste heat to escape and thus be detectable over intergalactic distances (or, at least, a whole galaxy of infrared sources would be detectable).

The thing is, black hole power plants wouldn’t give off this waste heat. At least in theory. A whole galaxy of black holes would radiate almost no power, and thus be undetectable across the universe, except for their gravity.

Which would be even closer to what we see today: Dark Matter, Intergalactic Voids.

Basically, my idea is, we happened to evolve at a point in history where a number of civilizations have arisen in the universe and are just starting to bump into each other in intergalactic space. Our galaxy hasn’t been reached yet, but it will soon.

We can even apply the Anthropic Argument here. Basically, why are there no alien civilizations apparently around? Because they haven’t reached us yet. If they did, we wouldn’t have evolved to ask the question.

Anyway, despite all this rampant speculation, it is important to review Sagan’s quote at the top of the page: “We should not be afraid to speculate. But we should be careful to distinguish speculation from fact.” No matter what I may type here, it is ONLY empirical evidence that will decide on way or another. Speculation may have its place, but speculation must always give way to scientific evidence.

I don’t know if I’m right, but it is interesting to think about. It’s a jumping off point, not an end in itself.

HUGE Planet Discovery!

Scientists from the Kepler mission have just announced that they’ve potentially found more that 1,200 new planets orbiting other stars. That’s incredible!

Here’s a brief rundown: out of the potential 1,235 planets, 68 are approximately Earth-size, 288 are super-Earth-size (i.e. rocky planets that are several times the mass of Earth), 662 are Neptune-size, 165 are the size of Jupiter and 19 are larger than Jupiter.

Furthermore, they’ve found that 54 of these planets orbit within their star’s habitable zone, and that of these 5 are roughly Earth-sized.

Now, the Kepler survey covers roughly 156,000 stars, and detects planets by watching them transit across the face of their star, measuring the small dip in the star’s brightness. Naturally, the odds of an orbiting planet actually passing in front of its star is very low. Still, I estimate that, assuming there is a planet orbiting within its habitable zone, there is 0.3% it will be lined up correctly, which translates into about 450 stars.

Think about that, out of 450 candidate stars, 5 have Earth-sized planets in Earth-like orbits, or 1 out of every 90.  That would imply that there are a few billion potentially Earth-like planets in the galaxy, the closest likely being no more than 20 light-years away.

Even considering other planets, 54 out of 450 equates to 1 out of 9. Which means that there’s likely some Jovian planet (possibly with habitable moons) within 10 light-years.

Note, however that I say Earth-sized, not Earth-like. The survey can’t measure the atmosphere or anything like that, so they could all actually be uninhabitable. Venus would count along one of the five if it were in the survey. But still, given what it implies about the abundance of Earth-like planets, this is a HUGE discovery.

Potential Ocean Planet Found!

A few days ago, it was announced that the star GJ 1214 has a planet orbiting it, dubbed GJ 1214b. The massively interestesting part is they were able to measure this planet’s diameter as it transited across its star, and measure its mass via its star’s wobble like you do. Anyway, using this they calculated the planet’s density, which is estimated to be around only 1800 kg/m^3.

For comparison, Earth is around 5500 kg/m^3, while water is about 1000 kg/m^3. In other words this planet is mostly made of liquid water! At least that’s the most likely answer. The next most likely liquids (like liquid carbon dioxide) boil at a much lower temperature than what the planet is estimated be at (between 250 – 550 degrees F).

Now, the more astute among may notice that the planet is also above the boiling point of water. The thing is, as pressure goes up, so does the boiling point (the reverse is also true, which is why at higher elevations the boiling point drops and it take longer to cook food). For example, at 100 atmospheres, the boiling point of water is around 520 degrees F. So it’s possible for there to be a huge global ocean, as long as a sufficiently dense atmosphere is also there. That sounds like a pretty big conjecture, but the density of the planet is known, meaning there must be some sort of atmosphere dense enough to hold it in. My bet is that its mostly water vapor (most astronomers are saying its likely hydrogen and helium, but at the same time there’s substantial loss to space due to its proximity to the star, and there’s really no way for the planet to make more hydrogen and helium to replenish it).

So, lets explore this world together! First, based on its density, scientists calculate that it composed of roughly 25% rock and 75% water. Obviously, the rock will be in the core since rock is denser than water and will sink towards the center. The planet’s diameter is estimated to be 34,000 km across, so its core, taking up about one-fourth the volume, would be around 21,000 kilomteters across. On top of that is water, an ocean 6500 km deep. That’s roughly 1000 times as deep as Earth’s oceans!

Now some interesting things happen when you consider how that all fits together. As I said before the atmosphere is likely composed of water vapor. Water vapor is a greenhouse gas, and will cause the temperature to rise, causing more water to evaporate, thus increasing the greenhouse effect. This will likely continue until some sort of equilibrium is reached, where the influx of heat from the star is the same as the amount radiated away. This might be beyond the point where water goes supercritical (that is,  the line between liquid and gas vanishes and they sort ‘blend into’ each other). That means that the water vapor atmosphere likely just gets denser and denser until it reaches the density of water, at which point it can’t compress anymore.

Even more interesting is what happens down in the depths of this massive ocean. There, the pressure become high enough that the water will become solid, making an exotic form of ice known as Ice VII. This is not like ordinary ice. This is hot ice, denser than water, and probably forms a layer around the rocky core.

In short, this planet most likely looks like a miniature Jovian planet, with water as the gas present instead of hydrogen.

So what about the most obvious question: if there water, what about life? I don’t know. With supercritical water I don’t think that organic structures could even form. But, if the atmosphere really is made of hydrogen (which isn’t a greehouse gas) the temperature would stay much lower, low enough for water to retain all its life-assisting properties. Anyway, here’s a nice graphic (I like graphics) to help illustrate what this planet is like:

 

Kaboom! On Jupiter!

Breaking news: something has impacted on the planet Jupiter.

There isn’t any confirmation of what it is was yet but my money’s on a small asteroid, probably no bigger than a mile across.

Anyway, for anyone with a telescope, this site details when the spot is visible. All times are in UT so subtract 5 hours for Eastern Time and 8 hours for Pacific. I know I’ll be looking up. It’s times like this that I’m glad I have a relatively big ‘scope.

See Venus During the Day!

If you’ve noticed lately, Jupiter and Venus are pretty close in the sky right now and soon after the Sun sets you can see them in the south-eastern sky. The Moon is hanging out nearby. What most people don’t know is that it is possible to see Venus during the day. It’s hard but with the Moon nearby, you’ll have a good point of reference.

First, find the Moon. It’s also up, cresent-shaped and a couple of degrees away. Just find it and start looking in the area to the right of the Moon (i.e. towards where the Sun is in the sky). It’s not too far, maybe two fingers held at arms length. Make sure you’re in a shaded area otherwise the Sun will probably wash it out.

Seriously! Go try it! Now, before the Sun sets! If you can’t do it today, tomorrow will hopefully be good too. The Moon will just have moved ten to twelve degrees towards the east, so it will maybe be a full hand-span away from Venus then.