And I think that, along with something deep and powerful like these songs are for me, you need something fun, happy, and amusing to balance it.

So, if you haven't heard of it already, meet Justin, a.k.a. shitmydadsays on Twitter. I don't like or use (anymore) twitter, but this is the funniest feed I've ever seen on the site.

Justin is a 29-year-old who lives with his 73-year-old dad. The feed, updated about once every day or two, consists solely of -- you guessed it -- shit his dad says. Only his dad is a hilarious treasure trove of wisdom. Some examples?

I hate paying bills... Son, don't say "me too." I didn't say that looking to relate to you. I said it instead of "go away."

That woman was sexy...Out of your league? Son. Let women figure out why they won't screw you, don't do it for them.

Nobody is that important. They eat, shit, and screw, just like you. Maybe not shit like you, you got those stomach problems.

Do these announcers ever shut the fuck up? Don't ever say stuff just because you think you should. That's the definition of an asshole.

I wouldn't worry about money...No, it has a lot to do with happiness, I just meant YOU shouldn't worry, cause you'd just piss it away.

Who in the fuck is tila tequila? Is she a stripper?...That's her? Yeah, that's a stripper, son, I don't give a shit what you say.

Hard to believe that you can look at something like this and not think it was another galaxy like our own, isn't it?

Yet when you look in the visible light -- which is all they knew how to do back then -- this is what the pinwheel galaxy (above) looks like through a modern advanced amateur telescope.

Is it really so clear to your naked eye that this image is so different from the one below?

Believe it or not, this image is of a planetary nebula, or just the gas blown off by a single star as it dies and collapses into a white dwarf. It isn't obvious to me that they should have known back then that these "spiral nebulae" are so different from planetary nebulae. Take a look at another spectacular one...

...and maybe a few more general ones.

Yup, they're all just dying stars that form planetary nebulae, and they're all within our own galaxy. Why couldn't the spiral ones be in there too? Thankfully, we've learned a lot more, and our observing abilities simply dwarf what they were 80 years ago. Take a look at today's Astronomy Picture of the Day, and see if you can't tell instantly what's a planetary nebula and what's a galaxy.

But without the full power of what we have today, it isn't obvious without doing some serious astronomical analysis, like measuring individual stars in these nebulae, which is what Hubble had to do. So enjoy the nearby planetary nebulae and the distant spiral nebulae, and enjoy the fact that we don't have to get them confused anymore. (And, it's always nice to give you some pretty pictures to look at on a Friday.)

How do type Ia supernovae work? Many solar systems out there are like our own, with one star dominating the system. Others, however, have two or more stars present in the system. Stars up to about four times the mass of our Sun, when they finish burning their nuclear fuel (we've got between 5 and 7 billion years to go for that), have their cores collapse down to white dwarfs. A white dwarf is a super dense object -- about 100 million times denser than Earth -- having a mass comparable to the Sun, but only the physical size of Earth. When there's a companion star nearby, however, the white dwarf can start stealing some of the mass. When the total mass of the star exceeds about 1.4 times the mass of our Sun, the atoms in the center become unstable, and the whole star explods in a type Ia supernova!

This happens all over the Universe, as the first white dwarfs formed when the Universe was just 150 million years old (barely 1% of its present age). These type Ia supernovae, as far as we can tell, go off regularly for the entire rest of the Universe, up until the present day. In fact, we've even found the binary companion that gave rise to the 1572 supernova!

The two things that make type Ia supernovae special? First off, they're the same at all times. Just like hydrogen atoms are the same everywhere in the Universe, whether it's 200 million years old or 13 billion years old, so it is with type Ia supernovae! In other words, if we see a type Ia supernova, we know that it formed from a white dwarf star tipping past the mass limit. Hence, they should be the same regardless of when in time they occur.

But second, and perhaps more importantly, when we measure the light from a type Ia supernova, we can immediately figure out how intrinsically bright it was, and therefore how far away it is. All you have to do is measure the shape of the light curve, and match it with well-known ones:

And that's why, when we see these supernovae, we can learn how far away they are. Combine that with a simple redshift measurement, and you can distinguish between a Universe with dark energy and one without it. The data are overwhelming (the one with a 'lambda' in it has dark energy):

And it was this analysis that led us to first accept dark energy as a probable component of the Universe. But once this came out at the end of the 1990s, there were a flurry of alternative explanations that came with it, and a lot of skepticism. Come back for part 3 to learn about it!

Once you can accept the Universe as being something expanding into an infinite nothing which is something, wearing stripes with plaid is easy. -A. Einstein

The why and how are questions that we do not yet have an answer to. Nonetheless, dark energy is practically as universally accepted among cosmologists as evolution is among biologists. In this new series, I'd like to take you through our current understanding of dark energy, and why we can't just wave our hands and explain it away.

How did this all get started? Well, you look out at things in the Universe, at things far away, and you're actually looking back in time. You'd think that if you looked at something one million light years away, you'd be looking backwards one million years in time, since light travels at the speed of light.

And you'd actually be wrong. Why? Because the Universe has been expanding during that one million years! Well, if you look at things in the Universe that happen at a whole bunch of different distances, you can figure out how the Universe has expanded over its history.

And if you know how it's expanded, you can learn what is it made up of. Well, if the Universe were all matter, it would do one of the first three cases in the top image, which I'll repeat for you here.

But if the Universe has dark energy in it, it should do the "accelerating" case at the far right. How can we tell them apart? Well, Hubble's law links two special things: distance and velocity. But the way these things are linked depends on what's in your Universe, like so:

The big thing is that, in a Universe with dark energy, distant objects will appear to be fainter than in a Universe without it. And in 1998, that was exactly what was discovered: Type Ia supernovae, formed the same way at all times in the Universe, were fainter than they should have been at large distances!

This was measured by two independent teams and subsequently confirmed numerous times. In fact, this was my discovery of the decade for the 1990s! And yet, it's one of the most unsettling parts of our picture of the Universe, that over 70% of the total energy in the Universe is this mysterious dark energy. We've been trying to explain it away, do without it, or come up with a reasonable alternative for our observations ever since, and we haven't been able to do it.

And I think it's worth telling you about all the different ways we've tried, and all about why those ways don't work. And at the end, you can decide whether it's hard to kill or not. So come back soon for parts 2, 3, and everything after!

My heroes had the heart to lose their lives out on a limb,
And all I remember is thinking, "I want to be like them!" --Gnarls Barkley

The Ares I-X rocket has been all over the news recently. I'm not sure that the news coverage sufficiently showcases how impressive this rocket actually is. Sure, you've all seen a picture of the rocket on the launchpad.

Yes, the rocket has a long history. Yes, it's nearly twice as high as the space shuttle (at a whopping 327 feet, or 99.7 meters). But did you know that when it was rolled out, it was attached to the launch pad by only four bolts?

And perhaps most impressively, do you realize how tall 327 feet actually is? Perhaps this vertical panorama of the rocket before it was rolled out expresses it better than words can.

Of course, before you're ready for launch, you had better test your engines. And that means testing the multiple different stages of the engines. Take a look at the following two images to get an idea of the thrust involved.

Both initial stages (above) and subsequent (below) need to be tested.

The 2.6 million pounds of thrust that Ares I-X can produce is enough to accelerate it from 0-60 in under 8 seconds. Not bad, considering it's accelerating a rocket, and it continues to accelerate for minutes, rather than topping out after a few seconds like your car does. We got a great view of this last week, at Ares I-X's maiden launch.

You get your rocket going quickly enough, and you wind up making a shock collar, as the difference in pressure at high speeds is enough to pull water vapor out of the air in a cone-like shape. Rory Duncan captured this beautifully:

And finally, because of a slight malfunction in one of the parachutes, part of the rocket that splashed-down into the ocean got damaged upon impact with the water. Amazing what a "soft" surface like water can do to a hard one like high-grade metal alloys used in constructing this rocket.

A promising start to the rocket that may ultimately lead to a return to manned exploration beyond Earth's orbit! And thanks to Universe Today, Astronomy Picture of the Day, and Graeme McMillan at io9 for providing many of the amazing photos found in this special!

Here is your king's scepter, and here is your kingdom, with the scorpion, the cobra, and the lizard for subjects. Free them if you will. Leave the slaves to me. --Ramses, in The Ten Commandments

This year, I went as Pharaoh Ramses II, as played by Yul Brynner (above and below).

Well, this is my take on it!

Even Moses couldn't resist having his picture taken with me.

So Happy Halloween to all of you, and I hope you enjoy the new profile photo!

What do you all say? Should we have a Halloween Costume Contest next year?

I had a dream, which was not all a dream.
The bright sun was extinguish'd, and the stars
Did wander darkling in the eternal space... --Lord Byron, Darkness

Halloween, believe it or not, is an astronomical holiday! The two solstices and two equinoxes are obvious astronomical holidays, since they correspond to the days of greatest, least, and equal daylight/night everywhere in both the Northern and Southern Hemispheres.

But halfway in-between each solstice and equinox lie the cross-quarter days. Just as we still mark the winter solstice (almost) with Christmas and the vernal equinox (almost) with Easter, we mark the cross-quarter days (almost) with minor holidays, including Groundhog Day, May Day, and Halloween, which comes from the old Celtic Samhain.

So happy Halloween from me, the Universe, and Bok globule Sh 2-136. I've got my costume all picked out, but no pictures until the weekend! Any guesses?

The farther backwards you can look, the farther forwards you are likely to see. -- Winston Churchill

But Hubble still has never seen one of the elusive, Holy Grails of astronomy: a metal-free star.

You see, immediately after the big bang, the Universe was filled with protons and neutrons, which finally fuse together (when the Universe cools enough) to create hydrogen, helium, and lithium nuclei. A few hundred thousand years later, the Universe cools enough to turn these nuclei into stable, neutral atoms. But that's it: beyond those three elements, there's nothing heavier. The Universe can't make them, not until the first stars form.

And someday, that's what we'd love to find: a metal-free star. These first stars, without any traces of heavier elements, are responsible for exploding and enriching (or polluting, depending on your perspective) the surrounding space with elements much heavier than lithium. Well, we just determined that a Gamma-Ray Burst earlier this year shattered the distance record:

At a redshift of eight, it's the most distant object ever discovered. This was light emitted around 13 billion years ago, when the Universe was less than one billion years old. And yet, looking at the spectrum of this one, it's still full of heavy elements!

Why?

When you form stars, anywhere, you make many, many little, low-mass stars, like red dwarfs. But you make a few very high-mass stars, called O-type or B-type stars. These stars are huge. Compared to a G-type star like our Sun, there's simply no contest.

Huge! Well, there's a big problem with being huge. What is it? Let's ask Bladerunner:

The light that burns twice as bright burns for half as long - and you have burned so very, very brightly, Roy. Look at you: you're the Prodigal Son; you're quite a prize! --Dr. Tyrell

So that's why this gamma-ray burst we've found, despite being only an estimated 630 million years into the birth of the Universe, is still chock-full of these heavier elements.

In fact, instead of a redshift of eight, we'd have to get all the way out to a redshift of around forty before we expect to start seeing a metal-free star. And the continued observation of this Gamma-Ray Burst confirms that, despite occurring 95% of the Universe's lifetime ago, the Universe was very, very similar then to the way it is now. The same stars, the same stuff, the same explosions as the ones we see now. There's never been a more distant, more comforting observation than this, that tells us pretty much exactly what we expected.

Gamma-Ray Bursts come from stars that die in very certain ways, and this one, from 13 billion years ago, is just like the ones that happened recently -- and close -- to us. By finding very few differences, one amazing piece of the picture comes into view: the Universe looked a lot like it does now a very short time after the big bang. That we can see things when the Universe was only 5% of its current age is like me looking back on my life and remembering everything that happened when I was 18 months old. Only, I wasn't able to do all the things I can do now back then. But the Universe can, and did, and now we've seen the first pieces of evidence for that! So thank you to that massive star that died all those billions of years ago. It's shown us that the Universe grows up very, very quickly! Read the comments on this post...]]> http://scienceblogs.com/startswithabang/2009/10/setting_the_cosmic_distance_re.php http://scienceblogs.com/startswithabang/2009/10/setting_the_cosmic_distance_re.php Astronomy Thu, 29 Oct 2009 10:03:06 -0500 In 1908, a huge fireball streaked across the sky and exploded a few kilometers above the Earth's surface, downing trees for miles and miles around but leaving no impact crater on the ground. This mystery was known as the Tunguska event.

But how did this happen? The amount of energy released was estimated to be somewhere between 5 and 30 Megatons of TNT. (Comparably to a "typical" hydrogen bomb.) What could've caused this devastation?

My answer: a large meteor or small asteroid/comet could have done this easily. How? Let me explain.

When a meteor enters Earth's atmosphere, it's moving very, very quickly relative to the Earth. Meteors have a speed relative to Earth anywhere between about 40,000 and 260,000 kilometers-per-hour (11 to 72 kilometers/second), which is incredibly fast. The Earth's atmosphere works -- through friction -- to slow this meteor down, heating it up and causing it to glow.

But if there's a lot of ice and/or frozen carbon dioxide in this meteor, it's going to heat up and start to boil. If you have a solid piece of rock with a cavern of boiling water inside, it's only a matter of time before the pressure builds up enough to cause a powerful explosion.

If I assume my meteor moves at the maximum speed its allowed, 260,000 kilometers-per-hour, I can figure out how massive it needs to be to produce 10 Megatons (4 x 10¹⁶ Joules) of energy. The answer? A little over 1,000 tonnes, which means it was probably a rock a little less than ten meters on each side. Which means it was about the size of the smaller rock to the left of Haystack Rock in this picture.

And physics will take care of the rest: convert that kinetic energy into heat energy, use that heat to boil liquid inside, and -- just like it did for the mythbusters -- the increased pressure will cause the explosion we're all looking for. And the only scientific principle you need to know to make this possible? The conservation of energy.

And that's it. Plain-and-simple, how simply hurtling through the atmosphere, if you're filled with something that can boil, can cause you to explode with a tremendous amount of energy. And there's no faking that.

But there's a whole lot that we do know about it just from looking out at the Universe.

You see, there are a whole bunch of scales we can see, from galaxies to clusters to superclusters and the large-scale structure of the Universe as a whole.

And -- since the big bang happened just under 14 billion years ago -- we can look at what these objects looked like at many different times along the way. We can see galaxies back when the Universe was a few hundred million years old, clusters when it was just 3 billion years old,

and the overall large-scale structure all the way back to when the Universe was just a few hundred thousand years old! (Thanks, WMAP!)

And what do we learn about the properties of dark matter from all of this?

1. It isn't in dense clumps. Not faint, dark stars, not planets, not basketballs, and not gas and dust. We've already gone over that it can't be normal matter, but it also can't form structures the same way that normal matter does.

2. It doesn't interact with itself. Yes, it interacts gravitationally, but that's not what I mean. It doesn't feel the strong nuclear force, it doesn't feel the electromagnetic force, and if it feels the weak force, it feels it even more weakly than neutrinos do! (And you need about a light year of lead to stop your typical neutrino.) As a result of this, dark matter is incredibly fluffy and diffuse, which means even in our Solar System, by the heart of our galaxy, dark matter's effects are negligibly unobservable.

3. These dark halos form very early. This is very important. Looking back as far as we can see, we find that these diffuse collapsed structures have been around for pretty much the entire history of the Universe. This tells us that the dark matter is cold, or that its kinetic energy has pretty much always been much, much less than its mass. This rules out every single standard model particle that we know of from being dark matter, since the stable ones are relatively light and are all produced hot.

So what is it? Unfortunately, this is really all we know about dark matter. We know how much there is, we know what its gravitational effects are, we know how it doesn't interact, and we know that it's always been cold and relatively slow-moving. Can you invent something that meets these requirements? Then congratulations, you have just invented a dark matter candidate!

All of the viable candidates fall into three main categories:

1. The Weakly Interacting Massive Particle (WIMP): you were once hot and produced during the big bang, but you stopped interacting with the rest of the Universe when it was very young. You cooled and collapsed, and you were heavy enough that by time we see structure, you're cold. The lower limit on how massive you are is somewhere around 100 times greater than the mass of a proton.
2. The Reptile: because you were born cold. You could have a large mass or a teeny-tiny mass, or be anywhere in between. But however you were made, you were born with very little energy, and were therefore made (or at least given a mass) sometime well after the big bang. The axion is a great example of this, and I just invented the moniker "reptile", so be prepared to explain yourself to your physicist friends.
3. The exotic: because you're not like anything else we know in the Universe. Maybe you're a bunch of unstable particles held together by some bizarre property that renders you undetectable. Maybe you're a fundamental fluid with a miniscule amount of viscosity, the only one we've ever encountered in the Universe. And maybe you're something else entirely, but you're neither WIMP nor a reptile. That's okay, we've got a home for you. "Exotic."

So there's still a very, very long way to go to discover what it is. But although I may not be able to tell you that it's an elephant, I know it has tusks, a trunk, and smells terrible!

For myself, I've concluded that dark matter very, very likely exists, that these three places are the right places to be looking, and that the more astrophysical evidence we can acquire (to tell us where the dark matter is, what its gravity is doing, etc.), the better we'll know this unseen elephant.

This concludes my official series on Dark Matter, but I'm always happy to talk more about it and answer good questions!

I do not know what I may appear to the world; but to myself I seem to have been only like a boy playing on the seashore, and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me. --Isaac Newton

Just inspiring, awesome, and yes, this was all undiscovered to him and subsequent scientists for centuries. The ability to give him a single picture like this would have changed worldviews about our place in the Universe for centuries (no need to wait for Hubble to find that the Universe is full of galaxies).

It looks like a table of galaxies, laid out, as it were, just for us. And now the very views and perspectives that eluded some of the greatest minds for their entire lifetimes are just... here. For you and me and everyone who wants to see them. Enjoy!

Those of you who know me personally might know I have a taste for Mike Judge, including his very funny movie Idiocracy. One of the funniest parts of Idiocracy was their all-pervasive energy drink, Brawndo:

Well, look out, Brawndo! Because here comes a possibly superior (fictional) product, Powerthirst!

I can't decide which one I'd rather drink, but I'm sure that either way, I'd be completely unstoppable. Science, energy, electrolytes, aaaaaarrrrrrrgggggghhhhh!

Michael Benson gives an account -- in words and pictures -- of a journey outwards, from nearby stars to nebulae to other galaxies to clusters of galaxies. The pictures alone are worth having a look at.

Beautiful? I don't know that that even begins to describe it, but it certainly helps give me a great perspective on what these different regions look like.

The idea of zooming out and looking at things on larger and larger scales really appeals to me. In fact, I think the slideshow fills in a lot of gaps for something like this video... (and if you're impatient, you may just want to start at the 3:30 mark or so)

In any case, enjoy the slideshow, enjoy the video, and I hope you enjoy the feeling of smallness that I feel when I look on these grand scales.

What do you need to do to make this happen, and how does it work?

First off, you need to design a stable magnetic track. This is actually simpler than you might think; you just need three magnetic "lines", where the outer two go in one direction, and the inner one goes in the opposite direction:

Next, you need a high temperature superconductor, typically made of Yttrium, Barium, and Copper Oxide. This way, when you get this thing down to the temperature of liquid nitrogen (77 Kelvin), all of the resistance goes away. (That's why, in the videos, the levitating thing is always smoking; that's the fact that it's only 77 Kelvin!)

When you bring a material like this close to -- but not in contact with -- a magnet, it magnetizes as well. Typically the little eddy currents (below) that magnetize this material decay after a short amount of time.

But when it's superconductor, there is no magnetic field inside! That's what the Meissner effect tells us (for those of you who followed the hint yesterday). In other words, the superconductor expels all the magnetic fields inside of itself, creating a perfect diamagnet, which simply means that it repels the permanent magnets below it.

And that's why it levitates! But, how do you get it to always stay the same distance away from the permanent magnet, even when it's upside down?!

Well, that requires one more thing, called flux pinning, which means you need imperfections in your superconductor. The effect of flux pinning keeps the magnet from floating away, and keeps the superconductor at a fixed height away from the magnet. The forces of the magnet and of the flux pinning are very large compared to gravity, and that's why you can turn it at an angle or even upside-down!

And that's it! Now that you know how it works, you've got a great project for an undergraduate physics student, or a physics enthusiast with access to liquid nitrogen! Amazing what we can do with just the simple laws of nature, isn't it?

(Video courtesy of Wimp.com.) What's going on here? Well, you've got:

• a series of bar magnets on the bottom,
• a ceramic cylinder,
• an insulating, non-magnetic piece of plastic between the magnets and cylinder,
• and liquid nitrogen being poured into the cylinder before the insulator's removed.

Amazing! For those of you who like puzzles, you've got until tomorrow's post goes up to figure it out. (I'll give you a hint: Walther Meissner.) What's going on here, and how does this work when you're upside-down?

Read the comments on this post...]]> http://scienceblogs.com/startswithabang/2009/10/say_chowdah_frenchie.php http://scienceblogs.com/startswithabang/2009/10/say_chowdah_frenchie.php Physics Wed, 21 Oct 2009 11:06:29 -0500