Did a skydiver see a meteoroid in flight?

April 6, 2014

A story surfaced over the last few days about a Norwegian skydiver who captured on film a rock flying by just after he deployed his parachute. Actually this happened about two years ago during which time some experts have been examining the evidence and have concluded that what he recorded was a falling meteoroid (it becomes a meteorite once it hits the ground)  I was very skeptical about this story and was waiting for the bad astronomer to debunk it but he failed to do so, so I will have to do it for myself. Update 7-4-2013: Phil Plait has now posted a more skeptical followup suggesting similar ideas as written here (and by others elsewhere) which I fully agree with.

meteorittfall_2columns_gallery-580x353

The first thing to think about is what are the chances of this happening? Records indicate that only one person has ever been hit by a meteorite. The person was a German boy who was hit by a pea sized meteorite. He was fine. There is also a story of a dog that was hit and vaporized but that story seems to be fake. In addition there are also a handful of cases  where cars have been hit by sizable meteorties. At least one, the Peeksill meteorite was verified.

peekskill_1

It could be that there are more unrecorded cases but we dont need precise numbers so let’s assume that as many as one car a year is actually hit by a sizable meteorite. There are about a billion cars in the world and most of them are outside exposed to the sky for most of the time. That is a lot of target space. On the other hand there are not too many active skydivers, maybe a hundred thousand at most doing on average a few jumps a year. Let’s be very optimistic and call it a million jumps where an event might have been recorded. A typical descent lasts about 5 minutes which is about a hundred thousandths of a year. You can work it our yourself, with these generous figures and the assumption that a car hit has a similar cross-section to the claimed event,  then we expect about one event like this every 100 million years. Yes, coincidences happen, but not something like that.

So what are the alternative theories. One possibility is a planned hoax. It would not be hard to put such a hoax together and there are plenty of hoaxes around, but the motivation to do an elaborate science hoax like this seems lacking. This is much more likely to be a hoax than a meteoroid but I dont think that is the best solution.

The most plausible explanation is the first thing that came into my mind and which others on slashdot have also suggested. It was a small stone that fell out of the parachute. Some people have disputed this because they say it was going too fast. In fact the estimated speed of the falling stone depends on its size or distance from the camera. The meteor experts estimated a large rock of a few kilograms travelling at 300 km/hr, but that is really based on the assumption that it is a meteoroid falling at terminal velocity. If it was a stone that fell out of a parachute it would have to be much smaller and slower and therefore nearer to the camera. This is equally consistent with what was recorded.

The object fell past about four seconds after the canopy opened. This is perfectly in line with expectations if it was on top of the parachute and bounced off. Is it possible for a skydiver to pack a stone in his parachute? Yes certainly as this video shows. A testimony from a skydiver on slashdot confirms that this happens. It is not common but it is common enough to expect someone to capture it on video sooner or later.

Update 8-4-2014: There is now an official explanation along the lines that the stone fell out as the parachute began to open and then passed the camera as the skydiver turned back a few seconds later. This is possible, as is my own similar explanation that it bounced off the top of the parachute and fell back a few seconds later.

Now everybody is saying that it is all fine and they knew all along that it might not have been a meteorite etc. Funny that the video and all the news reports made a very strong case for it being a meteorite and very few of us immediately noticed that this was very unlikely. That is the power of wishful thinking, confirmation bias and the persuasiveness of the authority of a qualified expert . If you were fooled, you will know to be more skeptical next time. In fact if you watch the video again you will see that they considered the possibility that it fell from the chute and that this was the one other possibility that they could not easily dismiss, but they did not say that outright. They just conveniently skipped over it and talked about other theories that could be more easily dismissed. The expert is also reported to have said that the chances of this happening are like winning the lottery three times in a row. That is about right and it is something that never happens but he did not seem to get that. Sometimes people’s desire to be involved in something special are just so strong that their powers of reason are put on hold.

Of course this does not mean that everything a scientist says can be dismissed. It means you have to listen to the reasoning rather than just the claim. It is not always possible to estimate the approximate probability for something being true as it was in this case and not everyone has the right kind of sense to make the right judgement. If that is you then you might want to take note of who quickly saw the truth in this story and who didn’t so you have a better idea of who to trust next time :-)


Planck thoughts

March 22, 2013

It’s great to see the Planck cosmic background radiation data released, so what is it telling us about the universe? First off the sky map now looks like this

Planck_CMB_565x318

Planck is the third satellite sent into space to look at the CMB and you can see how the resolution has improved in this picture from Wikipedia

PIA16874-CobeWmapPlanckComparison-20130321

Like the LHC, Planck is a European experiment. It was launched back in 2009 on an Ariane 5 rocket along with the Herschel Space Observatory. The US through NASA also contributed though.

The Planck data has given us some new measurements of key cosmological parameters. The universe is made up of  69.2±1.0% dark energy, 25.8±0.4% dark matter, and 4.82±0.05% visible matter. The percentage of dark energy increases as the universe expands while the ratio of dark to visible matter stays constant, so these figures are valid only for the present. Contributions to the total energy of the universe also includes a small amount of electromagnetic radiation (including the CMB itself) and neutrinos. The proportion of these is small and decreases with time.

Using the new Planck data the age of the universe is now 13.82 ± 0.05 billion years old. WMAP gave an answer of 13.77 ± 0.06 billion years. In the usual spirit of bloggers combinations we bravely assume no correlation of errors to get a combined figure of 13.80 ± 0.04 billion years, so we now know the age of the universe to within about 40 million years, less than the time since the dinosaurs died out.

The most important plot that the Planck analysis produced is the multipole analysis of the background anisotropy shown in this graph

Planck_power_spectrum_565w

This is like a fourier analysis done on the surface of a sphere are it is believed that the spectrum comes from quantum fluctuations during the inflationary phase of the big bang. The points follow the predicted curve almost perfectly and certainly within the expected range of cosmic variance given by the grey bounds. A similar plot was produced before by WMAP but Planck has been able to extend it to higher frequencies because of its superior angular resolution.

However, there are some anomalies at the low-frequency end that the analysis team have said are in the range of 2.5 to 3 sigma significance depending on the estimator used. In a particle physics experiment this would not be much but there is no look elsewhere effect to speak of here, any these are not statistical errors that will get better with more data. This is essentially the final result. Is it something to get excited about?

To answer that it is important to understand a little of how the multipole analysis works. The first term in a multipole analysis is the monopole which is just the average value of the radiation. For the CMB this is determined by the temperature and is not shown in this plot. The next multipole is the dipole. This is determined by our motion relative to the local preferred reference frame of the CMB so it is specified by three numbers from the velocity vector. This motion is considered to be a local effect so it is also subtracted off the CMB analysis and not regarded as part of the anisotropy. The first component that does appear is the quadrupole and as can be seen from the first point on the plot. The quadrupole is determined by 5 numbers so it is shown as an everage and a standard deviation.  As you can see it is significantly lower than expected. This was known to be the case already after WMAP but it is good to see it confirmed. This contributes to the 3 sigma anomaly but on its own it is more like a one sigma effect, so nothing too dramatic.

In general there is a multipole for every whole number l starting with l=0 for the monpole, l=1 for the dipole, l=2 for the quadrupole. This number l is labelled along the x-axis of the plot. It does not stop there of course. We have an octupole for l=3, a hexadecapole for l=4, a  dotriacontapole for l=5, a tetrahexacontapole for l=6, a octacosahectapole for l=7 etc. It goes up to l=2500 in this plot. Sadly I can’t write the name for that point. Each multipole is described by 2l+1 numbers. If you are familiar with spin you will recognise this as the number of components that describe a particle of spin l, it’s the same thing.

If you look carefully at the low-l end of the plot you will notice that the even-numbered points are low while the odd-numbered ones are high. This is the case up to l=8. In fact above that point they start to merge a range of l values into each point on the graph so this effect could extend further for all I know. Looking back at the WMAP plot of the same thing it seems that they started merging the points from about l=3 so we never saw this before (but some people did bevause they wrote papers about it). It was hidden, yet it is highly significant and for the Planck data it is responsible for the 3 sigma effect. In fact if they used an estimator that looked at the difference between odd and even points the significance might be higher.

There is another anomaly called the cold spot in the constellation of Eridanus. This is not on the axis of evil but it is terribly far off. Planck has also verified this spot first seen in the WMAP survey which is 70 µK cooler than the average CMB temperature.

What does it all mean? No idea!


Name A Very Large Radio Telescope Array

October 15, 2011

Do you remember the radio telescopes in the Film Contact where Jodie Foster and her team of geeks received the first haunting signal from alien intelligence? That was actually the Very Large Array run by the NRAO in Mew mexico and it has just finished a big upgrade to its electronic systems. They think that VLA is not a sufficiently imaginative and so they want to rename it but they also want the public to come up with the new name. You can very quickly and easily make a suggestion or several suggestions here.

I have already suggested “Carl Sagan Radio Observatory” and I am sure I will not be the only one using that theme. The BBC has gone for “Unfeasibly Large Telescopes”. There must be some more sophisticated ideas out there, so submit them and let us know.

 


ESA’s EUCLID to explore dark energy while NASA’a WFIRST is in doubt.

October 5, 2011

Just as the Nobel prize in physics is awarded for the discovery that points to dark energy, Europe’s space agency has announced that it will go ahead with it’s mission to map out the effects of dark energy on the distribution of galaxies over time. The mission christened EUCLID will be scheduled to launch in 2019 and will map the positions of galaxies out towards the edge of the observable universe. EUCLID was one of two missions that ESA announced yesterday under the banner “Dark and Bright“, the other being Solar Orbiter to launch in 2017.

ESA's EUCLID observatory

The news comes shortly after doubt was cast on the future of WFIRST a similar mission planned by NASA. The problem faced by the American Space Agency is that JWST, its ambitious next generation space-telescope, is over budget and absorbing funding from other projects.

The status of big science in the US has recently taken some big blows.  With the Tevatron bowing out to the superiority of Europe’s Large Hadron Collider and NASA’a manned space capability ending with the demise of the shuttle while China build’s up for a spectacular new space program, the days of US superiority in science seem to be fading into night. Many hopes now rest with the James-Webb Space Telescope which has the potential to be a ground breaking observatory especially for the exploration of the early universe, but the risk is high. The JWST is a complex instrument that will be sent to the Lagrange points far away from the Earth. Even if the US had a manned space program there would be no hope of servicing the mission as they did for the Hubble Space Telescope. It has to work first time and keep working. At least the American’s can still say they are bold.


Grail about to launch

September 8, 2011

NASA’s Grail mission is about to launch with destination the Moon.

The Delta II rocket will release two satellites into orbit above the lunar surface that will study the effect of gravitational anomalies on the flight trajectories. This will provide information about the internal density and structure of the Moon. They will also carry cameras to send back stereo 3D pictures of the moon surface.

Countdown is currently 4 minutes and holding.

Update: launch scrubbed for today due to bad weather. There are two launch windows tomorrow but forecast high winds may push the date back further.

When it does happen it will be covered on NASA TV

Update 10-Sep-2011: GRAIL has now launched

 

 

 


Juno set for launch

August 5, 2011

NASA is set to launch the billion dollar space probe Juno today. It is destined for a long voyage to Jupiter where it will enter orbit to study the planet and its moons in more detail then previous missions such as Galileo.  The journey will take six years and will include flybys of Mars and Earth to send it further out to the gas giant.

If all goes well the rocket will be sent into space on an ATLAS rocket in the next few minutes (12:25 local time). You can watch it on NASA TV.

Update: The launch was a success. Here is a recording in case you missed it.

 


Dawn approaches for Vesta

July 16, 2011

The NASA Dawn mission is approaching Vesta and should enter into obit tonight. We will know if it was successful tomorrow morning. It will stay in orbit around the asteroid for a year before gently pulling away using its ion drives to head out for Ceres which is now classified as a dwarf planet.

Studies of Vesta and Ceres could provide clues about the early formation of the solar system.

Update 17-Jul-2011: It has been confirmed that Dawn successfully entered orbit around Vesta.

Update 20-Jul-2011: This new picture now available


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