Tag Archives: space

Antarctica’s Unique Meteorites

Dr Shearer agreed the 4.5-billion-year ages of the meteorites indicated the likely source was an asteroid. “The history of this rock involves partial melting on a fairly primitive body,” he explained. Even if the rocks had been blown off Venus in an impact 4.5 billion years ago, they could not have drifted in space for such a vast length of time before landing in Antarctica recently, scientists said.
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The identity of the object that spawned the two meteorites may be elusive, but researchers have been able to draw up a basic profile. They know, for instance, that the parent body had “differentiated” – that is, had been reprocessed into a layered object, usually with a core, a mantle and a crust. Stony meteorites which have undergone this reprocessing are known as achondrites.

Laws of Physics May Need a Revision

Something seems wrong with the laws of physics

Einstein’s general theory of relativity swept Newton away by showing that gravity operates by distorting space itself.

Even Einstein, however, may not have got it right. Modern instruments have shown a departure from his predictions, too. In 1990 mission controllers at the Jet Propulsion Laboratory (JPL) in Pasadena, California, which operates America’s unmanned interplanetary space probes, noticed something odd happen to a Jupiter-bound craft, called Galileo. As it was flung around the Earth in what is known as a slingshot manoeuvre (designed to speed it on its way to the outer solar system), Galileo picked up more velocity than expected. Not much. Four millimetres a second, to be precise. But well within the range that can reliably be detected.
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Altogether, John Anderson and his colleagues analysed six slingshots involving five different spacecraft. Their paper on the matter is about to be published in Physical Review Letters. Crucially for the idea that there really is a systematic flaw in the laws of physics as they are understood today, their data can be described by a simple formula. It is therefore possible to predict what should happen on future occasions.

That is what Dr Anderson and his team have now done. They have worked out the exact amount of extra speed that should be observed when they analyse the data from a slingshot last November, which involved a craft called Rosetta. If their prediction is correct, it will confirm that the phenomenon is real and that their formula is capturing its essence. Although the cause would remain unknown, a likely explanation is that something in the laws of gravity needs radical revision.

An interesting puzzle that illustrates how scientists attempt to confirm our understanding and real world results. And those efforts include uncertainty and confusion. Too often, I think, people think science is only about absolute truth and facts without any room for questions. We understand gravity well, but that does not mean we have no mysteries yet to solve about gravity.

Research paper: The Anomalous Trajectories of the Pioneer Spacecraft

Great Self Portrait

photo of astronaut's faceplate reflecting earth

Photo by, and of, Astronaut Clay Anderson, Expedition 15 flight engineer. He used a digital camera to expose a photo of his helmet visor during the mission’s third planned session of extravehicular activity (EVA) on the International Space Station (15 August 2007). Also visible in the reflections in the visor are various components of the station and a blue and white portion of Earth. During the 5-hour, 28-minute spacewalk, Anderson and astronaut Rick Mastracchio (out of frame), STS-118 mission specialist, relocated the S-Band Antenna Sub-Assembly from Port 6 (P6) to Port 1 (P1) truss, installed a new transponder on P1 and retrieved the P6 transponder.

NASA provides their content, photos etc. online in an open access spirit. When linking to content (especially images) it is best to provide context (and with the internet the easiest way to do is so is relevant links). You can find many low resolution pictures of the image above around the internet. Trying to find the context around the image is not so easy – it took me quite awhile to do so. I try to provide the context and links. Lately some more sites will link to some original sources but this is still done far to infrequently.

There are also still far too many pointy haired bosses (PHB) making decisions to break the web by killing pages: web pages must live forever. Those PHB’s decisions do reduce the great benefit of linking but it is still worth doing for those cases where web sites are managed by people with the knowledge and ability to manage an internet resource properly.

Photo: NASA – high resolution version

So, You Want to be an Astrophysicist?

Dynamics of Cats (good name don’t you think) has an interesting series of posts: So, you want to be an astrophysicist? The latest is: Part 2.5 – grad school by Steinn SigurÃ°sson:

Think very seriously about whether you want to do theory, observation, data analysis or instrumentation.
You may end up doing things you never imagined out of necessity (like theorists go take observations, cause if they don’t no one else will; or observers running simulations, or building the instrument they need to do the observations etc etc).
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Finally: READ!!! Pro-actively.
Check arXiv regularly and thoroughly. Read the papers relevant to you and anything else that looks interesting.
Read the references! They are there for a reason. Read the citations – if a paper is interesting, papers which cite it are also likely to be interesting. Use the ADS “C” option liberally and look through it quickly. If in doubt ask you advisor, or just read it anyway.

Next, the slightly tricky issue of what we actually “do”, research wise type of thingy. Might take a while…

arXiv.org is a (even the) great open access article resource. “Open access to 400,419 e-prints in Physics, Mathematics, Computer Science and Quantitative Biology.”