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About half the Earth-Moon distance ... was how close 2018 GE3 went by last weekend.  Whee!

 

You can, like I did, call it up on JPL's Small Body Browser though most folks won't find that comprehensible.  50 to 100 meter size class is ... interesting but not extinction-level.  Could be bad if you were right under it, though; assuming it blows up in the atmosphere you'd be under a large nuke-class airburst, and at that point details that are hard to assess start mattering.

Edited by Cancer
left an embarrassing 's' out of 'assess'
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Sunset on Mars:  

This isn't really news; I just hadn't heard this point until today's meeting, in one of the prize lectures.   The neutron star - neutron star merger 18 months ago that was seen in gravitatio

And Sojourner on Mars, that went with Pathfinder... hey, found a graphic:  

Posted Images

On 4/15/2018 at 7:21 PM, Beast said:

what about ice melting at the ice caps?
the magnetic field does  redirect a good portion of  that radiation to the poles
and maybe  the outflow/inflow of the magnetic field is heating the ice cap?

 

Magnetic heating is not a factor for non-metallic substances, especially at low strengths such as that of Earth's magnetic field.  The field does indeed guide charged particles to the poles, but if charged particles melted ice caps, then one would expect a weaker magnetic field to result in less melting.

 

Furthermore, postulating alternate causes for climate change doesn't disprove the generally accepted greenhouse effect as the cause.  Even if the cause might be magnetic fields or sunspots or death rays from Mars, the science of spectral absorption has been well understood since the 19th century.  If we burn X fossil fuels, we add Y carbon dioxide to the atmosphere, resulting in Z heating, and by God we know X and Y, and the resulting Z matches predictions pretty damn closely.*  In order for someone to suggest that something else is causing climate change, they must also explain why it isn't CO2 emissions.

 

Trust me, I want to believe that our gas guzzlers aren't going to drown the cities and bleach the reefs.  But the reality is pretty dire.

 

 

* Supposed errors in the predictive models have since been corrected; the usual culprits are oceanic heat absorption (which caused an apparent slowdown in heating before it was measured) and satellite measurements of upper atmospheric temperatures (which is cherry picking one temperature measurement).  Almost every prediction of heating rates has ultimately turned out to be too conservative.

 

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And the CO2 data for the last 60 years is bulletproof.

 

And the CO2 accumulation, without any possible chance of contradiction, is anthropogenic.  Track down the economic figures for coal and petroleum production (they are freely available; every county publishes it as signs of their economic studliness).  Assume all the coal is burned, and half the petroleum is (some gets turned into plastics, and the 50% guess is in the right ball park); take the tonnage of fossil carbon burned, add the necessary tonnage of oxygen to turn that into CO2; then dilute the tonnage of CO2 in the known mass of the atmosphere.  The measured increase in CO2 content is within a factor of 2 of that simple calculation, and it is off in the sense that about half of the fossil-carbon CO2 is absorbed by something (largely dissolved in the ocean, but some is taken up in the biosphere) while the rest accumulates as atmospheric gas.  (If this sounds like a quickie classroom exercise, there's a good reason.) The "coldness" of the modern CO2 (that is, how little carbon-14 there is in it) is confirmation that it's fossil carbon, stuff that had lain for many times the 5730-year half-life of carbon-14 in mineral strata so it had decayed way completely.

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A recent NOVA episode gave quite a thorough explanation for it all, accessible to non-scientists. (Including a recreation of the 1840 experiment that showed that CO2 absorbs infrared.).

EDIT: The title was, "Decoding the Climate Machine." Or maybe "Decoding the Weather Machine." I watched it again, and both titles appeared on screen.

 

Short version is that any "skepticism" about humans causing climate change requires several areas of very well established science to be wrong, in ways that could be detected in a community college science lab. Plus a conspiracy so vast and baroque that it dwarfs the Illuminati, Trilateralists, Freemasons and Antarctic Space Nazis put together.

 

ADDENDUM: "But how do we know the CO2 comes from fossil fuels?" Cancer addressed this, but the only other known phenomenon -- at least, the only one I've heard of -- that might pump that much CO2 into the atmosphere that quickly is a flood basalt event, like the ones that created the Deccan Traps or the Channeled Scablands of Eastern Washington. And I think we'd notice a few million square miles of fresh, glowing lava.

 

SECOND ADDENDUM: Also, note what Cancer said before: The magnetic field is weakening on a timescale of tens or hundreds of thousands of years. Climate change is, measurably, happening on a scale of decades to centuries -- a thousand times faster.

 

Dean Shomshak

 

 

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The May 19, 2018 issue of the Economist has an article about how astronomers are using the GAIA dataset to try solving a fairly significant puzzle in astrophysics: the rate at which the universe expands. Astronomers have two ways to measure this... and the measurements do not match. One method works directly from the Cosmic Microwave Background. The other uses a "ladder" of inferences:

-- Nearby stars can have their distance measured by parallax.

-- Within that range are bright, pulsating stars called Cepheid variables. Conveniently, a Cepheid's period correlates rather precisely with its absolute brightness. So, Cepheids can be used to find the distance to nearby galaxies. (Near in a cosmic sense, anyway.)

-- In those galaxies, astronomers see supernovae; and because they know the distance to the galaxies, they can tell that a certain kind of supernova always has a certain brightness. So, by watching for these supernovae, astronomers can measure the distance to galaxies out hundreds of millions of light-years.

-- And by measuring how fast those galaxies recede at a given distance, they infer the rate at which the universe expands.

 

The two methods do not give the same result. They differ by about 6 kilometers per second per megaparsec. (IIRC. I don't have the article in front of me.)

 

Oops.

 

Many astronomers hoped the problem was in the long chain of inference from parallax to Cepheids to supernovae. Every measurement has a margin of error, after all, and the errors at one link in the chain will increase the errors of later stages. It was hoped that GAIA, by supplying more accurate measurements to more stars than were ever measured before, would adjust the brightness scale for Cepheids -- and this correction would adjust the distances to galaxies and make the measurements of cosmic expansion match.

 

Nope. They still don't match.

 

From this, astronomers conclude that something is going on they do not understand, and it's probably pretty important. More research needed.

 

Dean Shomshak

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The May, 2018 issue of Scientific American had an article about the new field of "Multimessenger" astronomy -- observing an event using neutrinos and gravitational waves as well as electromagnetic radiation. So far there are only a few examples, but they've already been significant. Supernova 1987A, first detected when its neutrino pulse registered on every neutrino detector in the world, revealed that even though supernovae can outshine a galaxy in visible light they emit even more of their energy in neutrinos. While the recent observation of two colliding neutron stars, observed in light and gravitational waves, has already disproven a number of alternative theories of gravity.

 

Dean Shomshak

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On ‎5‎/‎27‎/‎2018 at 5:04 PM, DShomshak said:

The May 19, 2018 issue of the Economist has an article about how astronomers are using the GAIA dataset to try solving a fairly significant puzzle in astrophysics: the rate at which the universe expands. Astronomers have two ways to measure this... and the measurements do not match. One method works directly from the Cosmic Microwave Background. The other uses a "ladder" of inferences:

-- Nearby stars can have their distance measured by parallax.

-- Within that range are bright, pulsating stars called Cepheid variables. Conveniently, a Cepheid's period correlates rather precisely with its absolute brightness. So, Cepheids can be used to find the distance to nearby galaxies. (Near in a cosmic sense, anyway.)

-- In those galaxies, astronomers see supernovae; and because they know the distance to the galaxies, they can tell that a certain kind of supernova always has a certain brightness. So, by watching for these supernovae, astronomers can measure the distance to galaxies out hundreds of millions of light-years.

-- And by measuring how fast those galaxies recede at a given distance, they infer the rate at which the universe expands.

 

The two methods do not give the same result. They differ by about 6 kilometers per second per megaparsec. (IIRC. I don't have the article in front of me.)

 

Oops.

 

Many astronomers hoped the problem was in the long chain of inference from parallax to Cepheids to supernovae. Every measurement has a margin of error, after all, and the errors at one link in the chain will increase the errors of later stages. It was hoped that GAIA, by supplying more accurate measurements to more stars than were ever measured before, would adjust the brightness scale for Cepheids -- and this correction would adjust the distances to galaxies and make the measurements of cosmic expansion match.

 

Nope. They still don't match.

 

From this, astronomers conclude that something is going on they do not understand, and it's probably pretty important. More research needed.

 

Dean Shomshak

 

I'd read the same article (or similar one) and been confused myself on what exactly the issue was. Are we still just talking measurement error,  methodology error, or are we seeing evidence of some unexplained phenomena? It seems to me that the assumptions of some kind of uniform expansion, or constant expansion, or constant acceleration of expansion are just that, an assumptions. Why couldn't the universe expand, non-uniformly... in pulses (that last millions or billions of years) rather than a steady stream? Wave propagation on a cosmic level, like  a ripple through a pond, bending space time in some parts of the universe differently than other, over the course of eons?

 

Not being a physics guy, I'm not clear on the base assumptions being made that allow the measurement processes you listed above. Any good source on those?

 

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2 hours ago, RDU Neil said:

The content is in the 8 June 2018 issue of Science (likely to be behind a subscriber wall).

 

Two papers here.  The one getting all the press is the result of mass spectrometer measurements of the stuff released from Martian surface samples when the stuff is heated.  This kind of thing was done with the Viking landers back in 1976, but the unsuspected presence of powerful oxidizing substances (perchlorates) in the Martian soil, generated over time by the solar ultraviolet (Mars's atmosphere does not block UV), made it more likely that those early results were due to the perchlorates reacting with stuff in the analysis chamber.  There's no way to remove the perchlorates from the soil, but by structuring your measurement process correctly you can sidestep them (cause them to be released from the soil, chew up other stuff which is what we really want to know about now, and eventually all the perchlorates are used up).  In effect, that's what they did with the mass spectrometer measurements: only measure things that are released after all the perchlorate damage is done.

 

Once you do that, you get solid detections of hydrocarbons (both aliphatics, chain-shaped molecules, like butane; and aromatics, ring-shaped molecules, the prototype of which is benzene), and things called thiophenes, which are compounds of carbon, hydrogen, and sulfur.  All of these are generated in the experiment by cooking the soil sample causing more complex organics to break down, and the breakdown products are released as gas and measured in the mass spectrometer.  You don't have a direct handle on what complex organics are in the soil; you just know they're there because only complex organics will release the other things when cooked.  It would take a rather more sophisticated instrument (something much larger than what's in the Curiosity rover now) to perform measurements of what those original organics are.

 

The second paper isn't getting as much press, but it also is interesting in the astrobiology front.  Using a laser spectrometers aboard  several instruments there have been measurements of methane content in the Martian atmosphere since 2004,  well before the Curiosity rover landed (Hiroshima Day 2012).  The detection of methane was announced early on, but it wasn't clear what it meant.  On Earth, methane is released from both currently-living biological sources (e.g., the bacteria in the guts of ruminants that turn cellulose into something that can be digested) and geological sources (some of which, at least, are from no-longer-living biological sources, but not all the sources are known).

 

The "other paper" in today's Science is a series of methane measurements from Curiosity, extending back over five Earth years (Aug 2012 - May 2017 included in the analysis), about 2 2/3 Mars years.  The methane content measured varies seasonally -- highest levels in norther summer, bottoms out in winter/spring.  Seasonal variation like that is easiest to explain via biological activity, not geological.

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3 minutes ago, Cancer said:

The "other paper" in today's Science is a series of methane measurements from Curiosity, extending back over five Earth years (Aug 2012 - May 2017 included in the analysis), about 2 2/3 Mars years.  The methane content measured varies seasonally -- highest levels in norther summer, bottoms out in winter/spring.  Seasonal variation like that is easiest to explain via biological activity, not geological.

 

I'd actually read something about these methane tests, but not the seasonal results. Very cool.

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On 6/6/2018 at 2:57 PM, DShomshak said:

The May, 2018 issue of Scientific American had an article about the new field of "Multimessenger" astronomy -- observing an event using neutrinos and gravitational waves as well as electromagnetic radiation. So far there are only a few examples, but they've already been significant. Supernova 1987A, first detected when its neutrino pulse registered on every neutrino detector in the world, revealed that even though supernovae can outshine a galaxy in visible light they emit even more of their energy in neutrinos. While the recent observation of two colliding neutron stars, observed in light and gravitational waves, has already disproven a number of alternative theories of gravity.

 

Dean Shomshak

 

Yeah, the unambiguous detection of neutrinos from 1987A dismissed a lot of questions with a single stroke.  Theory had predicted that core collapse supernovae should release a big neutrino burst, and the total energy in the neutrinos dwarfed the release in electromagnetic radiation (~99% of the energy comes out in neutrinos); the number of neutrinos detected was spang on this prediction, within the measurement uncertainties.  When I heard of the detection, that was literally the first question I asked: what the implied energy release in neutrinos was.  It was the key number: with that, you could tell if you basically understood supernovae or not.  And the number said: yes, you do have the basic understanding correct.

 

Last fall's gravity-waves-plus-electromagnetics detection of the merging neutron star event, and plausible interpretation of the ejecta as freshly synthesized r-process material, likewise settled a number of questions at a single stroke.

 

These stunning results, qualitatively different from any previous observations, drastically reduce the number of viable alternatives to known physics, because any new exotic theory not only has to explain whatever problem the theory was constructed to solve, but it has to work so that the rest of the observations are obeyed as well.  

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On 6/8/2018 at 9:53 AM, Cancer said:

These stunning results, qualitatively different from any previous observations, drastically reduce the number of viable alternatives to known physics, because any new exotic theory not only has to explain whatever problem the theory was constructed to solve, but it has to work so that the rest of the observations are obeyed as well.   

 

Would we have heard of any of these viable alternatives? (e.g., loop quantum gravity, string theory)

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27 minutes ago, Jhaierr said:

 

 

Would we have heard of any of these viable alternatives? (e.g., loop quantum gravity, string theory)

The Wikipedia articles on LQG and String Theory are interesting, even though I can't make heads or tails of the math. It sounds from what I'm reading that both these theories have weaknesses that these new discoveries point out. The fallout may last quite a while.

 

What happens if you're a theoretical physicist whose life's work is destroyed by one observation?

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32 minutes ago, Michael Hopcroft said:

The Wikipedia articles on LQG and String Theory are interesting, even though I can't make heads or tails of the math. It sounds from what I'm reading that both these theories have weaknesses that these new discoveries point out. The fallout may last quite a while.

 

What happens if you're a theoretical physicist whose life's work is destroyed by one observation?

In Traveller HERO, clearly you failed a career survival check and it's time to muster out and become a PC!

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23 hours ago, Jhaierr said:

Would we have heard of any of these viable alternatives? (e.g., loop quantum gravity, string theory)

 

Probably not, from 1987A.  That was long enough ago that it's sort of "ancient lore" by now.

 

The other, quite possibly, but generally I don't pay a lot of attention to way out theories.  Having an observation blow up your theory is ... common.  As Einstein once said, "A theoretician's most valuable tool is his wastebasket." 

 

Real theoreticians aren't wedded to any particular theory unless they really think they've got something (and have some people agreeing with them).  What makes a good theoretician is being able to play with a new idea, understand its limitations as well as its possibilities, and work out what's viable and what isn't; and, when confronted with a real measurement that refutes the theory, abandon it and move on.  (That last is what separates theoreticians from the loonies who claim to have "a new theory" and Will Not Let It Go.)   IMO new theories are in the "crunch all you want, we'll make more" category, but there's lots to be got out of that when done properly.  But I am a hard-headed observationalist.

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On 6/8/2018 at 8:33 AM, RDU Neil said:

 

I'd read the same article (or similar one) and been confused myself on what exactly the issue was. Are we still just talking measurement error,  methodology error, or are we seeing evidence of some unexplained phenomena? It seems to me that the assumptions of some kind of uniform expansion, or constant expansion, or constant acceleration of expansion are just that, an assumptions. Why couldn't the universe expand, non-uniformly... in pulses (that last millions or billions of years) rather than a steady stream? Wave propagation on a cosmic level, like  a ripple through a pond, bending space time in some parts of the universe differently than other, over the course of eons?

 

Not being a physics guy, I'm not clear on the base assumptions being made that allow the measurement processes you listed above. Any good source on those?

 

The short answer being, "We don't know.  Hence the problem."  It could be any of those.  Especially since Planck and WMAP spacecraft don't agree; they ought to, since they measured the same thing.  But the fact that they seem to be converging on two different values, over multiple studies, argues against measurement error.

 

As for non-uniform expansion, no.  Or at least, not in a way that affects this measurement.  While the rate of expansion is not constant, it does appear smooth and consistent with General Relativity over the history of the universe we can observe.  And it appears uniform in all directions as well.

 

You might as well start with WIkipedia, since it links to more scientific stuff.  https://en.wikipedia.org/wiki/Hubble's_law

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On 6/8/2018 at 3:27 AM, RDU Neil said:

 

"Mars rover strikes oil; fossil fuel industry ramping up drilling efforts"

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