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"The most important scientific revolutions all include, as their only common feature, the dethronement of human arrogance from one pedestal after another of previous convictions about our centrality in the cosmos." -Stephen Jay Gould
Tuesday, I talked about an alternative theory to cosmic inflation.
Whereas cosmic inflation gives you a uniform, flat Universe, that's the same temperature everywhere, with a predictable spectrum of fluctuations, the alternative model gave none of those things, but did give those regions of concentric rings with low fluctuation amplitude.
In detail, of course,…
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"Nullius in Verba.
(Take nobody's word for it.)" -Motto of the Royal Society
You know the drill. New ideas come out all the time. Sometimes they're new theories, sometimes they're old theories with a new twist, but regardless, we need to ask the question: How good is your theory?
For whatever it's worth, I came up with a scale for this.
The best ideas are beyond validated. They are confirmed over and over, predict new phenomena that gets verified, and don't have any self-inconsistencies.
Well, a couple of weeks ago, a new twist on an old idea was proposed by Roger Penrose.
A little…
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"I have found the best way to give advice to your children is to find out what they want and then advise them to do it." -Harry Truman
It's the end of the term here at my college, as well as most colleges across the nation. And while the students are freaking out about finals, grades, and other things associated with the end of the semester, there's a new one that's coming up more and more frequently all across the nation.
I'm looking squarely at you, helicopter parents. While college students, perhaps, should be going through and learning to cope with the stresses of higher education, many…
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"Black holes are where God divided by zero." -Stephen Wright
Yesterday, I told you about all the evidence for the Black Hole at the center of our galaxy. In particular, we see multiple stars orbiting a single point that emits no light of any type at all.
And, perhaps unsurprisingly, the comments became very active. So let's take a look at some of what was said, and let's see what we can further learn about black holes from answering your questions.
I see the stars orbiting on their own orbits, but I mean, all orbits seem quite different to me, there´s no central point they are orbiting…
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"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
Black holes. You've all heard them before, and you can visualize them pretty easily. How so? Start by thinking about the Earth.
Held together by the immense force of gravity, the Earth is a difficult world to leave.
What exactly do I mean by that?
It takes a tremendous amount of energy to get off of the planet Earth. If you were at the surface of the Earth, you'd have to be moving at around 40,000 km/hr (or 25,000 mi/…
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"If we die, we want people to accept it. We are in a risky business, and we hope that if anything happens to us it will not delay the program. The conquest of space is worth the risk of life."
-Gus Grissom, who perished in the Apollo 1 fire.
Every once in a while, I try to look past the amazing accomplishments humanity has made in space. And here's a great little piece by Leo Kottke for you to listen to,
Memories Are Made Of This.Forget about walking on the Moon, sending spacecrafts to all the planets and even out of the Solar System, and instead to just focus on how beautiful some small…
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"The image is more than an idea. It is a vortex or cluster of fused ideas and is endowed with energy." -Ezra Pound
Back in the 1800s, observational astronomy was already entering its heyday. We had already discovered Uranus, the first planet not visible to the naked eye, knew of a number of comets and asteroids, and had a whole catalog of "bizarre" objects in the sky.
Some turned out to be star clusters, globular clusters, remnants of exploded stars, or other galaxies entirely! But one of the unfortunate things about astronomy around 1800 is that the Southern Hemisphere objects were grossly…
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"Keep up the good work, if only for a while, if only for the twinkling of a tiny galaxy." -Wislawa Szymborska
You all know about shooting stars.
Seen from Earth, mostly during meteor showers, these aren't stars at all, but are tiny fragments of rock that hit the Earth's atmosphere, and streak across it, leaving a bright fireball as it burns up. If you're a great (and lucky) astrophotographer, you can nab a picture of one close up as it burns up.
But this principle, that a fast-moving object traveling through space will run into whatever matter is in its way, leads us to some amazing…
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"It is all a matter of time scale. An event that would be unthinkable in a hundred years may be inevitable in a hundred million." -Carl Sagan
There's some speculation that NASA, later this week, might announce evidence for life on Saturn's moon Titan.
I'm not going to comment on the speculation, but it's worth asking the question, scientifically, "How would the Universe make life, from scratch?"
Let's start by telling you what "scratch" means. If you're familiar with the story of the Universe, one of the things you know is that things were very hot and dense in the past. So hot that you…
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"Sounds of laughter shades of life
Are ringing through my open ears
Exciting and inviting me
Limitless undying love which
Shines around me like a million suns
It calls me on and on across the Universe" -The Beatles
Now that you've all given thanks for all the great things you've got, it's time to enjoy some of the great music of our world. The Beatles had some amazing songs, such as Across the Universe, and this Rufus Wainwright cover more than does it justice.
Across The UniverseWhile you're enjoying that, why not take a look at some of the great things some cancer researchers are doing?…
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"The Sun, with all those planets revolving around it and dependent on it, can still ripen a bunch of grapes as if it had nothing else in the universe to do." -Galileo
So tomorrow is American Thanksgiving, and it's one of our traditions that I'm most happy to take part in. So without any ado, let me give thanks with you.
Thanks not just for the wonderful world we have, with its glorious skies and all the secrets it slowly reveals to us, but for everything that allows us to have the world we have.
Thanks to the atom, with its massive, compact nucleus and its oppositely-charged, much lighter…
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"Surely something is wanting in our conception of the universe. We know positive and negative electricity, north and south magnetism, and why not some extra terrestrial matter related to terrestrial matter, as the source is to the sink. ... Worlds may have formed of this stuff, with element and compounds possessing identical properties with out own, indistinguishable from them until they are brought into each other's vicinity. ... Astronomy, the oldest and most juvenile of the sciences, may still have some surprises in store. Many anti-matter be commended to its care! ... Do dreams ever come…
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"Photograph: a picture painted by the sun without instruction in art." -Ambrose Bierce
The most common emails I get about this blog are questions about physics, astronomy, and some very speculative theories. But second most common are questions asking where I get my pictures.
Well, except in rare instances, I don't make them myself. Should you just make like Sharon Jones and the Dap-Kings and,
Keep On Looking?Let me tell you about a great tool to help you figure out where any image on the site comes from! Let's pick one at random, from say, this recent post.
So what can you do? You can copy…
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"I came at exactly the right time... I was 26 years old, and all the monks and priests down here were ready to retire. So I overlapped enough that I got to know them all." -Allan Sandage
As many of you have heard, Allan Sandage passed away last Saturday. Let me tell you a little bit about this man, why he stands as such a towering figure in modern cosmology, and why he should be held in even higher esteem than he normally is.
Allan Sandage was a coworker of Edwin Hubble's, and he took up one of the most pressing questions of the day after Hubble's death in 1953: What is the Age of the…
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"I've been noticing gravity since I was very young." -Cameron Diaz
Yesterday, I told you about one of the simplest arguments for dark matter. We look out at the fluctuations in the microwave background on all the different angular scales we can measure -- from about 0.2 degrees all the way up to the whole sky -- and look at what the temperature fluctuations are doing.
We also look at the large-scale structure in the Universe, and try to correlate how mass clumps together.
We are only allowed -- by the laws of physics -- a few parameters to play with to try to fit this massive data set. We…
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"What makes the universe so hard to comprehend is that there's nothing to compare it with." -Anonymous
If I were brand new to theoretical cosmology, I might be skeptical of a whole bunch of "dark" things that I'd heard of. "Dark matter?" "Dark energy?" Come on; you've got to be kidding me! You're telling me that 95% of the Universe is not made of protons, neutrons, and electrons, like all the matter we know?
After all, I look out at the Universe, and this is what I see.
Stars, galaxies, gas and dust... normal matter, all of it. Yet all I need to do is start with two very well-supported…
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"Victory is sweetest when you've known defeat." -Malcolm Forbes
It is official; you voted and the world has listened. I am proud to welcome you to the best physics blog in the world!
We not only won physics.org's best blog, we were also the people's choice award winner!
Thanks to the judges, thanks to all of you who voted, and a special thanks to all of you who just read and enjoy what I'm putting out, regardless of whether you comment on every single post or not on a single one at all.
The Universe wouldn't be the same without each one of us, and I owe a huge thanks to each one of you.…
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"No one means all he says, and yet very few say all they mean, for words are slippery and thought is viscous." -Henry Brooks Adams
There are plenty of advocates out there for letting go of the great, descriptive, but outdated words of our language. And I simply can't get on board with that. As Storyhill will tell you, there's value in holding on.
Holding OnWhy? Those of you who've been reading this site for a while know that one of the great struggles I deal with is expressing, in a clear, straightforward, and meaningful way, these physical concepts that baffle some of the world's greatest…
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"A vacuum is a hell of a lot better than some of the stuff that nature replaces it with." -Tennessee Williams
Matter -- everything you know, love, hate, see, taste, and feel -- takes up space.
Even air must take up space. Not just wind, but still, stationary air takes up space. We've known this since Empedocles, in the 5th Century B.C., who had a clepsydra -- a hollow gourd with many holes in the bottom and a single hole at the top -- demonstrated it.
You plunge the gourd into a stream, lake or river, and it fills with water. If you lift the gourd up, the water leaks out of the bottom. But…
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"Global warming is the greatest and most successful pseudoscientific fraud I have seen in my long life." -Hal Lewis
The most valuable natural resources we have at our disposal during our brief lives are the following.
That's right, the Earth and the Sun. And if we want life on Earth to continue as we know it, we have to avoid destroying our own natural environment. The big questions are whether we're actually damaging it to the point of devastating destruction, and if so, what we need to do to fix it.
One of the things we've measured reasonably well -- at, for instance, weather stations all…