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
When you watch someone fall into a black hole, what you actually see is pretty surprising. You see, a black hole's gravity distorts the space around it, and it does so without providing any light of its own, giving you a unique perspective on the Universe.
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.
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.
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.
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!
But if you think that's bizarre, here's where it gets really weird: the person falling in notices no difference in how time passes or how light appears to them. They would continue to fall in to the black hole and cross the event horizon as though nothing happened.
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.
Fun stuff, yes? Perhaps someday, "death by black hole" will be commonplace, although it will take an infinite amount of time for you to see someone else experience it!
In the comments on one of my posts, someone pointed me towards Stephen Crothers, who gives the following argument (in a nutshell) as to why black holes cannot possibly exist:
General Relativity is our theory of gravity, which relates the curvature of space to the gravitational acceleration of objects.
This theory only works in certain regimes; it breaks down at the point of singularities.
A black hole, as predicted by Schwarzschild, is a singularity.
Therefore, since singularities are forbidden by General Relativity, there is no reason to think that black holes exist.
(You can watch his video here, or read his full argument here.) Therefore, he argues, astronomers are wasting their time looking for black holes, since their existence isn't even a physical prediction.
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.
Some meteor showers are spectacular, while most are mundane. If you sit around during a typical shower, you might see anywhere from 50 to 100 meteors an hour, if the Moon isn't out.
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
Last week, scientists from LCROSS announced that they had detected "a buttload" of water on the Moon. Let's go over what happened and what it means.
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.
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.)
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!
Can you touch your toes? Seems like an easy thing to do for those of us who have the flexibility.
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.
Too bad that Futurama's smell-o-scope doesn't actually exists.
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!)
(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
Last time we visited dark energy, we discussed its initial discovery. This came about from the fact that supernovae observed with a certain redshift (i.e., moving away from us) appear to be systematically fainter than we were able to explain.
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!
