The most well-known one is that nothing -- not even light -- can ever escape once it falls in. Well, my question is, if you fell in to a black hole, as you crossed the event horizon in your sturdy, well-lit spaceship, would the lights stay on or would they go out as you crossed into the black hole? (Ignoring the tidal forces that would rip you and the spaceship apart.)

In other words, you've read the first 1497 pages of the Count of Monte Cristo as you cross the event horizon; will you be able to finish your book with your last remaining moments?

What do you think? Feel free to discuss below; I'll post the answer with an explanation on Monday!

Why it is that of all the billions and billions of strange objects in the Cosmos -- novas, quasars, pulsars, black holes -- you are beyond doubt the strangest? -Walker Percy

Well, if you watch someone else fall in, you'd see them approach the black hole normally, and then the bizarreness starts. As they go deeper and deeper into the gravitational field of the black hole, a few super bizarre things all start to happen simultaneously.

1. The light coming from the person gets redshifted; they'll start to take on a redder hue and then, eventually, will require infrared, microwave, and then radio "vision" to see.
2. The speed at which they appear to fall in will get asymptotically slow; they will appear to fall in towards the event horizon at a slower and slower speed, never quite reaching it.
3. The amount of light coming from them gets less and less. In addition to getting redder, they also will appear dimmer, even if they emit their own source of light!

What would you see if you fell into this black hole? Luckily, Andrew Hamilton and his group at Colorado have created a video (and an accurate video at that) to illustrate this:

And that's not even counting what the tidal forces would do to you as you fell in, which includes (in chronological order):

• Tearing your extremities (head, arms, legs) from your torso,
• tearing the individual muscles, tendons, ligaments, etc., apart from your body,
• tearing individual cells apart from one another,
• tearing the organelles inside each cell apart, destroying cells themselves,
• tearing the individual molecules apart into atoms,
• tearing your atoms apart into nuclei and electrons, and finally
• tearing the individual nuclei apart into, eventually, quarks and gluons.

1. General Relativity is our theory of gravity, which relates the curvature of space to the gravitational acceleration of objects.
2. This theory only works in certain regimes; it breaks down at the point of singularities.
3. A black hole, as predicted by Schwarzschild, is a singularity.
4. Therefore, since singularities are forbidden by General Relativity, there is no reason to think that black holes exist.

Talk about not seeing a forest for the trees. The "singularity" is not essential for a black hole to exist. Honestly, it isn't important at all whether there's a singularity or not. All that matters, in the real world, is that something is both massive and compact enough so that, within a certain radius, light cannot escape from it. That is the astrophysical definition of a black hole.

So, do they exist? Definitely. Where do you look for incontrovertible proof? The center of the galaxy! There are no two ways around it; there is definitely a black hole there.

How am I so sure? The above image shows the center of our galaxy. There are many, many stars orbiting the central point where the arrows are pointing. We have tracked these orbits over more than a decade, thanks to the UCLA Galactic Center Group. Here's a screenshot of their results.

From the motion of these orbits, we can figure out what the mass of the object they orbit around is. It turns out to be over 2 million times as massive as our Sun. And yet, we don't see any light coming from that point. We don't see a white dwarf, we don't see a neutron star, we don't see any object at all.

For a mass that large, you will have a black hole if that mass is confined to a sphere of a diameter of about ten million kilometers. That isn't hard, considering we have many, many stars that we know of where an entire solar mass is confined to a diameter of about ten kilometers. (These are neutron stars.) If you up the mass, the neutrons at the core will eventually collapse under the tremendous pressures, and collapse farther. There's a well-known upper limit to how massive a neutron star can be, and it's less than three solar masses, much less two million.

So you can argue about whether singularities violate General Relativity or not until you're blue in the face. It doesn't have a damned thing to do with whether any light gets out of your ultra-dense, massive object. And that's what we call a black hole, and it exists. Don't believe it? Then tell me what's going on at the galactic center.

If you take a time-lapse photograph and look for meteors, you will, sometimes, get a great view of what's going on. Although it isn't immediately clear what's a meteor and what's a passing satellite or airplane, you can tell them apart in this video by looking for the "instant" streaks, which are meteors, versus the ones that streak for many frames, which are satellites or aircrafts.

Well, the Leonids peak tonight, and they are spectacular. Instead of getting one or two meteors a minute, we should get -- on average -- a meteor every five to ten seconds! What's more? The peak, tonight, is at around 3 AM Eastern Standard Time (Midnight Pacific Standard Time).

Even better? The Moon is practically new tonight.

This means that only a tiny crescent will be in the sky, and it'll be gone by an hour or two after sunset. Which means, if you get clear skies, you'll have ideal meteor shower conditions!

So where should you look on the sky? Near the constellation Leo; the meteors will emanate from there. (Ignore Saturn in the image below; it was there in 2006, but isn't in 2009. The stars are still in the same place, though.)

And at its peak, we should get about 500 meteors per hour, which is huge. If you get to see it remember to thank Comet Tempel Tuttle for coming through in 1998 and leaving this beautiful debris trail for us.

All of it makes for a beautiful sight this night! So go out and enjoy it, and know that I'll be jealous here in cloudy Portland!

I thought I should consult you first before I went ahead with my plan to destroy the Moon. -Greg Angelone, via The Straight Dope

The Moon is very different from Earth. It has no atmosphere (literally, less than one atom thick), day-and-night lasts for two weeks apiece, and the temperature extremes are horrifically severe. But one of the biggest differences? Whereas the Earth is tilted at 23.5 degrees as it goes around the Sun, the Moon is tilted by less than two degrees.

This is hugely important. On Earth, because of the 23.5 degree tilt, every place on Earth receives a significant amount of sunlight at some point during the year. But with a tilt that tiny on the Moon, the Sun never gets more than 1.54 degrees above the horizon as seen from either the North or South Pole of the Moon!

Or, in other words, if you dug a hole that was 100 meters deep and 100 meters wide, only the top 2.7 meters of your hole would ever get illuminated by the Sunlight, and the bottom 97.3 meters would be permanently shadowed. So if you ever put water in that hole, it should freeze and remain frozen for all eternity.

Well, we don't have holes that have been dug at the poles, but we do have "natural" holes. These appear as humongous craters, like so.

So, what did we do with LCROSS? We crashed it into one of these permanently shadowed craters, and looked at the debris plume that got shot up from the impact. If we find a huge amount of water, then we can infer that pretty much all of these permanently shadowed craters on the Moon are loaded with huge amounts of water, and will be for pretty much the next billion years.

So, the fact that we found "a buttload" of water? That means the Moon's craters at the North and South poles are loaded up with reservoirs of water, and all we have to do is go there and claim it. Hooray for exploration! Hooray for space! And hooray for the Moon!

But I want you to know something... you and me, it's not gonna be a one-way street. 'Cause I don't believe in one-way streets. Not between people, and not while I'm driving. So, here's some advice I wish I woulda got when I was your age: Live every week like it's Shark Week. -Tracy Jordan, 30 Rock

And, much like Tracy, the song for you this week is simple, sweet, and good-hearted. Enjoy an old classic, Just the Two of Us by Grover Washington, Jr., and Bill Withers.

Many of you have asked about whether there were any good science programs on television, and I have found one for you. Starting tomorrow night, it isn't Shark Week (sorry, Tracy). It's National Geographic's 2nd Annual Expedition Week. I've gotten an advance copy, and these are really interesting investigations into all sorts of natural and human phenomena. And yes, there's a great episode (with a lot of science) about Sharks (Image Credit: © Chris Ross/Chris Fischer).

There's also an episode about Terraforming Mars, which is balanced and scientifically accurate, plus it has Robert Zubrin, whom I met back in 1999 and really respect his views on Mars exploration and colonization. (Image Credit: National Geographic Channel.)

But the other episodes I've seen so far -- about the Amazonian Head-Shrinkers and the First Jesus -- have been fascinating, too.

The treatment of these subjects is entirely different from what I've come to expect from, say, the History Channel. The expeditions are riveting because the questions they're asking are riveting, and you get to journey along with the researchers, watching some of the science unfold as it unfolds. It gives me a tremendous appreciation for the level of specialization of knowledge in our society, as well as providing an accurate picture of scientific investigation.

It's something that's very rare on television these days, and I've found this to be an excellent program. So if you can watch it, enjoy it, and have a great weekend!

Now, here's the challenge. Stand with your back and your heels pressed up against a wall, and now try to touch your toes.

You can't do it! Not without putting your hands down on the floor, you can't. There's a super-simple reason for this: center-of-mass.

For human beings, your center-of-mass is somewhere in your abdomen. It's lower down for women than men, but in the abdomen region for everyone. When you typically bend down to touch your toes, you'll notice that the upper part of your body moves forwards, while the lower part moves backwards. You do this by default, but the major reason you need to do this is so that your center-of-mass stays over a stable point: your feet!

But as soon as you prop yourself up against the wall, the lower part of your body can't move back! So as the upper part moves forward, your center of mass moves forward. It goes from being over your heels to being over your arches to your toes, and the instant it extends out beyond your toes, you know what happens?

You begin to rotate, and once that happens, you're going to fall, like so:

(Image credit: Gabrielle Varieschi.) And that's it! This is a great trick to try on children to teach them about stability. It's also great for physics teachers to introduce torque, rotation, and center-of-mass. (And on unsuspecting coworkers to teach them about falling on their faces!)

It's a remarkable phenomenon that such a simple thing as touching your toes would be off-limits with your heels against a wall, but there it is! Don't believe me? Try it yourself and see what happens, but I warned you...

Professor Hubert Farnsworth: I'm sorry, Fry, but astronomers renamed Uranus in 2620 to end that stupid joke once and for all.
Fry: Oh. What's it called now?
Professor Hubert Farnsworth: Urrectum. Here, let me locate it for you.
Fry: No, no, I, I think I'll just smell around a bit over here.

Why is it too bad? Because space is filled with many different types of atoms, including Carbon, Nitrogen, Oxygen, and Hydrogen: the elements essential to terrestrial life. In space, these sometimes appear in isolation, they sometimes appear in toxic combinations (like hydrogen cyanide), and they sometimes appear as simple organic molecules, like sugars, alcohols, and esters. (Amino acids may yet be there, but we haven't discovered them yet!)

But earlier this year, astronomers turned their telescopes towards the galactic center, and looked at the dust cloud Sagittarius B2, which looks like this. (And click it to enlarge.)

(Image credit: ESO.) Sagittarius B2 is less than 400 light years from the galactic center. They found over 50 chemical compounds there, but one of the most interesting? Ethyl formate, which we typically form on Earth by reacting ethyl alcohol (the alcohol found in wine, beer, and liquor) with formic acid (which is commonly produced by ants and bees). The chemical compound is pretty simple, and looks like this:

Yes, it's an organic molecule, but we produce these in space all the time. What's particularly interesting about Ethyl Formate? It's what gives Rum its smell, and give Raspberries their flavor!

And that's at least, partially, what our galaxy smells like! Any Andromedans out there reading this? We smell like Raspberries and Rum! I have no idea what you smell like, but in comparison, I bet you stink compared to us!

(Image Credit: COBE's DIRBE imager; thanks Ned!) So the next time someone wonders what space smells like, you can not only tell them, you can tell them where to go to smell it!

Though the Sun is gone, I have a light. -Kurt Cobain

But we weren't satisfied with simply saying that there must be dark energy. We asked a lot of critical questions about why these supernovae might appear so faint.

First off, we asked the question, "Could these supernovae from far away be different than the type Ia supernovae we have today?"

Unfortunately, the answer is a resounding no. So long as atoms work exactly the same way, they require the same pressure to collapse at all points, times, and places in the Universe. The process of forming a Type Ia Supernova -- having a white dwarf accrete mass until the core collapses and it explodes -- should be independent of location and time.

Well, if the supernovae are constant, could the environments that they form in be different than the environments today? Of course they could. So, is there any way to make them appear fainter without them actually being fainter, and without having to resort to dark energy? Sure, you might say, block some of that light! All you need is some dust, like so.

What a simple idea, right? Problem solved?

Not so fast. Dust, in real life, is made up of real particles (atoms, molecules, grains, etc.), with real sizes. This means they affect light differently at different wavelengths. Not just red, green, and blue, but X-rays, ultraviolet, infrared, and more. We don't see this light dimmed more in one spectral band than any other; it's dimmed equally at all wavelengths!

So, real dust is out. But what if we invented some new type of dust that absorbed light the same at all wavelengths? We can give it a name: grey dust. We have no idea what would cause it, but it's a lot more believable that there's some new kind of dust out there than there is a whole new type of energy pervading the Universe.

Well, if this grey dust were there, then the light from distant supernovae would simply continue to appear dimmer and dimmer the farther away they were. Whereas, if the Universe had dark energy, the supernovae should start to appear relatively brighter beyond a certain distance. Take a look at the graph below to compare some different theories with the data.

As you can see, grey dust (the top line) is as inconsistent as a Universe with only normal matter (bottom line) when compared to the data.

So you can't simply blame it on a trick of the light. In fact, if we look at the most modern supernova data, it clearly favors dark energy significantly over even a flat, low-density Universe.

Other "light-blocking" schemes, such as photon-axion oscillations, suffer from the same problem; they don't give the right turn-over as shown above. If we've got the right laws of gravity, there's pretty much no way around dark energy.

But we don't like relying on only one source of data. Supernovae are nice, but what happens when we look at all the other evidence? Does that tell us there must be dark energy too, or could it be that the supernova data just cannot be trusted? Seems like a job for part 4, and so I'll see you then!

While most of the article was about Mars' history as a planet and the argument that in the past, it was much more Earth-like than it is today, I had one sentence that appears to have touched off a firestorm in the comments:

I don't know whether there was life on Mars or not, but based on what I know about abiogenesis and early Martian conditions, I think there's a good chance there once was.

Because this is a fundamental assumption that we make about the natural world. In all instances that we've observed, life only originates from pre-existing life. Yet at some point, there was certainly no life. It's hard to imagine having life when your Universe is so hot you can't even form atoms, isn't it? So if we go back 13.7 billion years, close to the big bang, we know there was no life.

So there are a whole plethora of possibilities for its origin. The primordial soup on Earth, in the atmosphere, in space, on another planet, from a pre-existing star, etc. Abiogenesis is simply the idea that when life arose, it did so from non-life, through natural processes.

We have no idea how long it took (the oldest evidence for life on Earth points back at least 3.5 billion years), whether Earth started with life or not, or whether that life originated somewhere else. But we know that we have life now, and we know that at some point in the past, there wasn't life in the Universe. So yes, I've made an assumption of abiogenesis. But is that unreasonable? Other than life originating supernaturally, is there any alternative? I suppose you could say it was brought here from another Universe, but then it had to originate in that Universe somehow. Unless it's turtles all the way down, I don't see it.

And as scientists, we operate under the assumption that the laws of nature govern the observable phenomena in the Universe. Including the origin of life. So this is an open scientific question, as to how life originated. That's why people still study it. We can get to complex organic molecules from non-life, and we can get to a huge amount of complexity starting with simple life, but we don't know how to go from complex organic molecules to life, yet. But I think it's reasonable to assume that we must. Do you?

The Mars Polar Lander cost the average American the price of half a cheeseburger. A human lander would cost the average American more -- perhaps even ten cheeseburgers! So be it. That is no great sacrifice.
-JONAH GOLDBERG, National Review Online, May 3, 2000

And they approached me to write an article for them about Mars. An excerpt is below:

But the closest reasonable place to look for life outside Earth? That has to be Mars. Today, Mars is dry, desolate, and frozen. Its atmosphere is so thin that it would take 140 Martian atmospheres all stacked atop one another to give you the same pressure we find here on Earth. Why would we even consider a place like this to be hospitable to life? There are three pieces to the argument: imaging from space, exploration of the soil, and the theory of Mars' history.
[...]
So finally, we come to the theory side, where we try to put these observations together. Clearly, from the observations of riverbeds, discoveries of unusual minerals on the surface, and frozen water just beneath the soil's surface, Mars wasn't always like it is now. It used to have liquid water, which means it used to have a thicker atmosphere. Like all planets at the beginning of the solar system, Mars probably had a molten core that produced a strong magnetic field, shielding it from solar radiation and keeping the atmosphere intact. That means water, water everywhere! On Earth, everywhere there's water, there's life. Was the same true on Mars?

So read the articles, and let me know your opinions! What do you think we'll find when we finally do go and look for life on Mars?

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!