The Milky Way and Andromeda are siblings, … we used to think they were near-twins. .. [But] the black hole at [Andromeda’s] heart is more than a hundred times as massive as ours. And while our galaxy is strewn with about 150 of the bright galactic baubles known as globular clusters, Andromeda boasts more than 400. … Whereas Andromeda is a pretty well-adjusted spiral, the Milky Way is an oddball – dimmer and quieter than all but a few per cent of its peers. That is probably because typical spirals such as Andromeda are transformed by collisions with other galaxies over their lifetimes. …

The Milky Way must have lived relatively undisturbed. Except for encounters with a few little galaxies such as the Sagittarius dwarf, which the Milky Way is slowly devouring, we wouldn’t have seen much action for 10 billion years. Perhaps that is why we are here to note the difference. More disturbed spirals would have suffered more supernova explosions and other upheavals, possibly making the Milky Way’s rare serenity especially hospitable for complex life.

{ NewScientist | via Overcoming Bias }

Sixty-five million years ago, a Manhattan-size meteorite traveling through space at about 11 kilometers per second punched through the sky before hitting the ground near what is now Mexico’s Yucatán Peninsula. The energy released by the impact poured into the atmosphere, heating Earth’s surface. Then the dust lofted by this impact blocked out the sun, bringing years of wintry conditions everywhere, wiping out many terrestrial species, including the nonfeathered dinosaurs. Birds and mammals thus owe their ascendancy to the intersection of two orbits: that of Earth and that of a devastating visitor from deep space. (…)

In December 2004, scientists at NASA and the Jet Propulsion Laboratory (JPL), in Pasadena, Calif., estimated there was a nearly 3 percent chance that a 30-billion-kilogram rock called 99942 Apophis would slam into Earth in 2029, releasing the energy equivalent of 500 million tons of TNT. That’s enough to level small countries or raise tsunamis that could wash away coastal cities on several continents. More recent calculations have lowered the odds of a 2029 impact to about 1 in 250 000. This time around, Apophis will probably miss us—but only by 30 000 km, less than one-tenth of the distance to the moon. (…)

We considered several strategies. The most dramatic—and the favorite of Hollywood special-effects experts—is the nuclear option. Just load up the rocket with a bunch of thermonuclear bombs, aim carefully, and light the fuse when the spacecraft approaches the target. What could be simpler? The blast would blow off enough material to alter the trajectory of the body, nudging it into an orbit that wouldn’t intersect Earth.

But what if the target is brittle? The object might then fragment, and instead of one large body targeting Earth, there could be several rocks—now highly radioactive—headed our way.

{ IEEE Spectrum | Continue reading }

painting { Nicola Verlato }

What would we do if we encountered an alien race? As it turns out, the question has garnered considerable academic thought since the first reported flying saucer sighting in 1947, not just as an inquiry in human psychology, but also as a way of contemplating what aliens might do if they ever found us. From astronomers to ufologists to anthropologists, scholars who have contemplated the various “contact scenarios” believe our course of action would strongly depend on the relative intelligence level of the newfound beings. Here, we outline what would happen if we encountered primitive, humanlike, and godlike aliens. (…)

In 1950 the U.S. military developed a procedure called “Seven Steps to Contact,” laying out the logical steps we would take upon discovering creatures with roughly human-level sentience. According to the steps, we would begin with remote surveillance and data gathering, and would eventually move on to covert visitations with the goal of gauging the performance characteristics of the aliens’ vehicles and weaponry.

{ LiveScience | Continue reading }

related { Alien Abductions May Be Vivid Dreams, Study Shows }

photo { Laerke Posselt }

The Earth has a large moon, making it unique in the inner solar system. Mercury and Venus have no moons, and Mars has only two small asteroid-sized objects orbiting it. In this essay, the father of the SMART-1 lunar mission, Bernard Foing of the European Space Agency, looks at the effect the Moon has had on the Earth, and explores how different our world would be if we had no planetary companion. Would life have evolved differently, or even appeared on Earth without the Moon?

{ Astrobio | Continue reading }

painting { Jules Joseph Lefebvre, La Vérité, 1870 }

{ 1. Wyne Veen | 2 }

unrelated { If you were thrown into the vacuum of space with no space suit, would you explode? }

The idea that our universe is embedded in a broader multidimensional space has captured the imagination of scientists and the general population alike. 

This notion is not entirely science fiction. According to some theories, our cosmos may exist in parallel with other universes in other sets of dimensions. Cosmologists call these universes braneworlds. And among that many prospects that this raises is the idea that things from our Universe might somehow end up in another.

A couple of years ago, Michael Sarrazin at the University of Namur in Belgium and a few others showed how matter might make the leap in the presence of large magnetic potentials. That provided a theoretical basis for real matter swapping. 

Today, Sarrazin and a few pals say that our galaxy might produce a magnetic potential large enough to make this happen for real. If so, we ought to be able to observe matter leaping back and forth between universes in the lab. In fact, such observations might already have been made in certain experiments.

{ The Physics arXiv Blog | Continue reading }

photo { Adam Lampton }

What occurred to Newton was that there was a force of gravity, which of course everybody knew about, it’s not like he actually discovered gravity– everybody knew there was such a thing as gravity. But if you go back into antiquity, the way that the celestial objects, the moon, the sun, and the planets, were treated by astronomy had nothing to do with the way things on earth were treated. These were entirely different realms, and what Newton realized was that there had to be a force holding the moon in orbit around the earth. This is not something that Aristotle or his predecessors thought, because they were treating the planets and the moon as though they just naturally went around in circles. Newton realized there had to be some force holding the moon in its orbit around the earth, to keep it from wandering off, and he knew also there was a force that was pulling the apple down to the earth. And so what suddenly struck him was that those could be one and the same thing, the same force.

(…)

I’m not sure it’s accurate to say that physicists want to hand time over to philosophers. Some physicists are very adamant about wanting to say things about it; Sean Carroll for example is very adamant about saying that time is real. You have others saying that time is just an illusion, that there isn’t really a direction of time, and so forth. I myself think that all of the reasons that lead people to say things like that have very little merit, and that people have just been misled, largely by mistaking the mathematics they use to describe reality for reality itself. If you think that mathematical objects are not in time, and mathematical objects don’t change — which is perfectly true — and then you’re always using mathematical objects to describe the world, you could easily fall into the idea that the world itself doesn’t change, because your representations of it don’t.

There are other, technical reasons that people have thought that you don’t need a direction of time, or that physics doesn’t postulate a direction of time. My own view is that none of those arguments are very good. To the question as to why a physicist would want to hand time over to philosophers, the answer would be that physicists for almost a hundred years have been dissuaded from trying to think about fundamental questions. I think most physicists would quite rightly say “I don’t have the tools to answer a question like ‘what is time?’ - I have the tools to solve a differential equation.” The asking of fundamental physical questions is just not part of the training of a physicist anymore.

(…)

On earth, of all the billions of species that have evolved, only one has developed intelligence to the level of producing technology. Which means that kind of intelligence is really not very useful. It’s not actually, in the general case, of much evolutionary value. We tend to think, because we love to think of ourselves, human beings, as the top of the evolutionary ladder, that the intelligence we have, that makes us human beings, is the thing that all of evolution is striving toward. But what we know is that that’s not true. Obviously it doesn’t matter that much if you’re a beetle, that you be really smart. If it were, evolution would have produced much more intelligent beetles. We have no empirical data to suggest that there’s a high probability that evolution on another planet would lead to technological intelligence. There is just too much we don’t know.

{ Tim Maudlin/The Atlantic | Continue reading }

photo { Luisa Opalesky }

Three studies released Wednesday, in the journal Nature and at the American Astronomical Society’s conference in Austin, Texas, demonstrate an extrasolar real estate boom. One study shows that in our Milky Way, most stars have planets. And since there are a lot of stars in our galaxy — about 100 billion — that means a lot of planets. (…)

Confirmed planets outside our solar system — called exoplanets — now number well over 700, still-to-be-confirmed ones are in the thousands.

{ NY Times | Continue reading }

previously { Now, just where might this Great Filter be located? }

The question confronting us today is: who owns the Geosynchronous Orbit?

In recent years, “parking spots” in the geosynchronous orbit have become an increasingly hot commodity. According to the NASA, since the launch of the first television satellite into a geosynchronous orbit in 1964, the number of objects in Earth’s orbit has steadily increased to over 200 new additions per year. This increase was initially fueled by the Cold War, during which space was a prime area of competition between the United States and the Soviet Union. Yet over two decades after the end of the US-Soviet space race, even the global financial crisis that began in 2007 does not seem to have diminished the demand for telecommunications satellites positioned in GSO. This ongoing scramble to place satellites in GSO prompted some developing equatorial countries to assert sovereignty over the outer space “above” their territorial borders, presumably with the hope of extracting rent from the developed countries that circulate their technologies overhead. So far, the international community has rejected this notion, but the legal status of the GSO remains in limbo.

{ SSRN | Continue reading }

photo { Roman Signer }

{ Distant world looks ripe for life | Distant world looks too ripe for life }

“Did you know that 95% the universe is dark matter?” (…) “What about dark energy?” (…)

It is true that most of the universe is made up of things that can’t be seen, and whose presence is inferred by its effects on the things that can be seen. But what effects do we see? And how does that translate to a percentage of the universe that remains a mystery?

Galaxies rotate, and when we use gravitational laws to predict what that rotation should look like, we find that they should behave like the solar system–the farther away something is from the central mass (in the case of the solar system, the sun, and in the case of a galaxy, the supermassive black hole at the center), the slower it should orbit; the gravitational force on Pluto, for instance, is much smaller than the gravitational force on Mercury, because it’s much farther away from the sun. A star at the fingertip of an arm of the galaxy should orbit more slowly than we do. However, that’s not really what happens: galaxies have flat rotation curves, meaning that objects farther away from the supermassive black hole don’t really orbit more slowly than things closer to it.

What this implies is that there is lots of mass spread throughout the galaxy–that most of the mass isn’t just at the center–and that the spread-out mass has a large gravitational effect on the galaxy’s rotation.

{ Smaller Questions | Continue reading }

photos { 1. Pearly | 2. Natalia Arias }

related { Computer simulations suggest that a giant planet was kicked out of our solar system billions of years ago, saving Earth in the process. But how solid are those simulations? }

{ SETI@Home is a distributed computing initiative that analyses radio signals for signs of extra terrestrial intelligence. SETI@Home volunteers have identified some 4.2 billion signals. Most, if not all, of them are likely to be the result of noise or interference. | The Physics arXiv Blog }

Annie Platoff, a librarian at UC Santa Barbara, is on a mission to find out what happened to the American flags that astronauts planted on the moon during the six lunar landings.

Platoff’s research pinpointed four of them, including the one from Apollo 17, the final lunar mission.  At the very least, the nylon national symbols are “tattered” and have “darkened” over the years.  She speculates that the other two, planted during Apollo 11 and Apollo 12, fell victim to the ignition gases emitted from the lunar module during blast-off.

{ Time | Continue reading }

artwork { Jasper Johns, Green Flag, 1956 | Graphite pencil, crayon and collage on paper }

It wasn’t so long ago we thought space and time were the absolute and unchanging scaffolding of the universe. Then along came Albert Einstein, who showed that different observers can disagree about the length of objects and the timing of events. His theory of relativity unified space and time into a single entity - space-time. It meant the way we thought about the fabric of reality would never be the same again.

But did Einstein’s revolution go far enough? Physicist Lee Smolin at the Perimeter Institute for Theoretical Physics in Waterloo, Ontario, Canada, doesn’t think so. He and a trio of colleagues are aiming to take relativity to a whole new level, and they have space-time in their sights. They say we need to forget about the home Einstein invented for us: we live instead in a place called phase space.
If this radical claim is true, it could solve a troubling paradox about black holes that has stumped physicists for decades. What’s more, it could set them on the path towards their heart’s desire: a “theory of everything” that will finally unite general relativity and quantum mechanics.

{ NewScientist | Continue reading }

‘Multiverse’ theory suggested by microwave background

The idea that other universes — as well as our own — lie within “bubbles” of space and time has received a boost.

Studies of the low-temperature glow left from the Big Bang suggest that several of these “bubble universes” may have left marks on our own.

This “multiverse” idea is popular in modern physics, but experimental tests have been hard to come by. The preliminary work, to be published in Physical Review D, will be firmed up using data from the Planck telescope.

{ BBC | Continue reading }

In our Solar System, planets fall into two types. First, there are the rocky planets like Earth, Mars, and Venus, which are similar in size and support gaseous atmospheres. Then there are the gas giants, like Jupiter, Saturn, and Uranus. These huge puff balls are two or more orders of magnitude bigger than their rocky cousins.

Perhaps strangest of all, there are no planets in between; nothing that sits on the borderline between rocky minnow and gas giant.

This sharp distinction has driven much of astronomers’ thinking about planet formation. One of the main challenges they have faced is to come up with a theory that explains the formation of two entirely different types of planet, but no hybrids that share characteristics of both.

That thinking will have to change. It now looks as if we’ve been fooled by our own Solar System. When astronomers look elsewhere, this two-tiered planetary division disappears.

Astrophysicists have now spotted more than 500 planets orbiting other stars and all of these systems seem entirely different to our Solar System. They’ve seen entirely new class of planets such as the Super-Jupiters that are many times larger than our biggest planet with orbits closer than Mercury.

But the one we’re interested in here has a mass that spans the range from Earth to Uranus, exactly the range that is missing from our Solar System.

Astronomers are calling these new types of planet Super-Earths, and so far they have found more than 30 of them.

{ The Physics arXiv Blog | Continue reading }

In the early 1970s, NASA sent two spacecraft on a roller coaster ride towards the outer Solar System. Pioneer 10 and 11 travelled past Jupiter (and Saturn in Pioneer 11’s case) and are now heading out into interstellar space.

But in 2002, physicists at NASA’s Jet Propulsion Laboratory in Pasadena, noticed a puzzling phenomenon. The spacecraft are slowing down. Nobody knows why but NASA analysed 11 years of tracking data for Pioneer 10 and 3 years for Pioneer 11 to prove it.

This deceleration, called “the Pioneer anomaly,” has become one of the biggest problems in astrophysics. One idea is that gravity is different at theses distances (Pioneers 10 and 11 are now at 30 and 70 AU [Astronomical Units]). That would be the most exciting conclusion.

But before astrophysicists can accept this, other more mundane explanations have to be ruled out. Chief among these is the possibility that the deceleration is caused by heat from the spacecraft’s radioactive batteries, which may radiate more in one direction than another.

{ The Physics arXiv Blog | Continue reading }

In recent years, the search for an Earth-like planet orbiting another star has been the most exciting in science. The world has waited with baited breath for the discovery of another Earth.

But the discovery of Earth 2.0 has been a damp squib. Not because astronomers haven’t found one; on the contrary! The problem is they’ve found too many candidates. And these have turned out to be so unlike Earth that it’s hard to imagine that any of them can be a convincing twin.

We’re left, like the starving donkey equidistant between two bails of hay, unable to decide on what to celebrate.

The top candidates so far are these:

* Gliese 4581 g, the fourth rock from a red dwarf some 20 light years from Earth in the constellation of Libra

* GJ 1214 b, a sub-Neptune-sized planet orbiting a star in the constellation of Ophiucus 40 light years away

* and HD 28185 b, a gas giant in a near circular orbit that is entirely within the habitable zone of a Sun-like star in the constellation of Eridanus. This planet’s moons, if it has any, may be good candidates for ‘other Earths’

Today, we can add another strange planet to the list: 55 Cancri f, one of five planets known to orbit an orange dwarf star some 40 light years away in the constellation of Cancer.

{ The Physics arXiv Blog | Continue reading }

photo { Constantin Brancusi, Bird in Space, ca. 1936 }

Take a look at your hands. In them, you find atoms that once belonged to stars dead more than five billion years ago. Those stars, bigger than our sun, forged much of the chemistry of life during their last moments, before exploding into giant supernovae. They forged chemical elements spread through the interstellar medium, collecting here and there in self-gravitating hydrogen clouds. Occasionally, these clouds would become unstable to their own gravity and contract. These contracting nebulae gave rise to stars and their orbiting planets, trillions of them in our Milky Way alone.

In at least one of them, elements combined in incredibly complex ways to create living creatures. And of these myriad beings, one developed mind, the ability to sustain complex thoughts and to wonder about its origins.

We are, in a very real sense, self-aware stardust. (…)

There are many gaps to fill in this cosmic narrative, and this is what makes science exciting. As we thrust ahead, we learn more about the universe and our place in it. Perhaps one of the most controversial questions that follows from this discussion concerns our inevitability. Is our existence an inevitable consequence of the laws of Nature? Or are we an accident, and the cosmos could equally well exist without us?

{ Marcelo Gleiser | Continue reading }

Some unusual solar readings, including fading sunspots and weakening magnetic activity near the poles, could be indications that our sun is preparing to be less active in the coming years.

The results of three separate studies seem to show that even as the current sunspot cycle swells toward the solar maximum, the sun could be heading into a more-dormant period, with activity during the next 11-year sunspot cycle greatly reduced or even eliminated.

{ Space | Continue reading | + video | Read more: Major Drop in Solar Activity Predicted }

artwork { Richard Serra, out-of-round X, 1999 | On view through Aug. 28, 2011, at The Metropolitan Museum of Art, NYC }

In 1998, two teams of astronomers independently reported amazing and bizarre news: the Universal expansion known for decades was not slowing down as expected, but was speeding up. Something was accelerating the Universe.

Since then, the existence of this something was fiercely debated, but time after time it fought with and overcame objections. Almost all professional astronomers now accept it’s real, but we still don’t know what the heck is causing it. So scientists keep going back to the telescopes and try to figure it out. (…)

We see galaxies rushing away from us. Moreover, the farther away they are, the faster they appear to be moving. The rate of that expansion is what was measured. If you find a galaxy 1 megaparsec away (about 3.26 million light years), the expansion of space would carry it along at 73.8 km/sec (fast enough to cross the United States in about one minute!). A galaxy 2 megaparsecs away would be traveling away at 147.6 km/sec, and so on*.

The last time this was measured accurately, the speed was seen to be 74.2 +/- 3.6 km/sec/mpc. (…)

By knowing this number so well, it allows better understanding of how the Universe is behaving. It also means astronomers can study just how much the Universe deviates from this constant rate at large distances due to the acceleration. And that in turn allows us to throw out some ideas for what dark energy is, and entertain notions of what it might be.

{ Discover | Continue reading }

related { Evidence of Big Bang May Disappear in 1 Trillion Years }