Reporting diameters to three digits seems unrealistic. But at least it lets one drop in on Fig. 2a in my previous post. I could believe 3 digits of velocity because that data collection is well better. Think of miss distance in terms of geostationary orbit because that's where most of our most distance stuff hangs out. Multiply by 10.6
For most of those, even two digits is fantasy. I'll presume that like many display fields, rounding is more of a display thing than a realistic indicator.
Perhaps only Arecibo and FAST try to radar rocks. Not easy . Velocities come from multiple optical sightings and lovely math, so digits become plausible.
Orbital parameter figures are known to many digits. For an example, here are the parameters of yesterday's close rock, along with uncertainties expressed as 1-sigmas: JPL Small-Body Database Browser These uncertainties should shrink significantly as the number of observations increases and the "data-arc span" gets longer. But sizes are commonly known only from the apparent brightness. For dim objects, this measure is necessarily coarse.
Wasn't it 2017 - Earth had its 1st flyby from out Beyond our galaxy? This Interstellar traveler was roughly 400 yards long. Its trajectory was mapped & I don't recall which Galaxy they speculated that it came from, but after its arrival, our own star hurled it back out in another direction. Photo taken was very blurry, so they took creative license in cleaning it up. It differs from the common asteroid shape too. .
It was merely from beyond our solar system, not from another galaxy. It was moving faster than solar escape speed, that is how we know it was a visitor from elsewhere. But it wasn't moving fast enough to be unbound from our galaxy. That image is purely artistic license. The actual photos revealed only a single point of light, too small to be resolved into any shape, which varied in brightness over time (rotating object) consistent with something that long and narrow. In theory it could have even been a sphere with a white side and a very dark side, but that would also be quite wild.
But if it's not from our solar system, and not from another galaxy, that would mean it came from ......... .
Here is a zoo of radar images: Category:Radar images of Near-Earth Objects - Wikimedia Commons Perhaps another link could be added. My only assertion is that in few instances are there enough pixels to know dimensions to three real digits. In a way that's good news because it would need to be big and close to get 'artistic rendition' image quality. Nobody likes big and close - not with such large relative velocities. Point about accurate orbits @1064 is both accurate and not inconsistent. == Snuffling about, I find that Goldstone and Green Bank contribute much to radar imaging. That they often operate in bistatic mode. Means a big pulse of radar energy comes from (eg) Arecibo and returns are detected at high resolution elsewhere. Besides computational power, this needs very precise clocks at both ends. Arecibo has a big room full of capacitors which was earlier used to make radar strong radar pulses but I really don't know if is is still involved. Not on the public tour Can't even find a image on the web. It may persist simply because no one wants to pay whatever recycling would cost.
A technical advantage of this mode is that it is far easier to isolate the receiver from the transmitter. This isolation is essential for listening to weak signals at the limit of the receiver's thermal electron noise, and is a tough problem when both pieces of equipment are sitting next to each other and sharing the same antenna and feed lines. It gets really hard when the transmitter is sending out megawatt pulses.
Three million hectares of Siberian forests are now burning which is relatively large. Carbon storages of such forests is well known, so... This will have transferred about 0.06 petagrams of carbon to atmosphere as CO2. As always such numbers can be compared to global annual fossil-fuel burn of ~10 petagrams. Another fun Siberia fact concerns Tunguska asteroid* airburst in 1908 which leveled ~0.2 million hectares. Knockdowns in such cold climates decompose slowly, such that one can still go there and see things (THings uninteresting to many folks, but still... *Could have been a comet.
And Trump has offered Putin some firefighting assistance. Just a couple months after cutting firefighting assistance to the socialist state of Kalifornia.
It would be very nice, and topical, to know how related federal and state spending has changed since California recent difficult fires. A quantitative discussion won't ruffle feathers. Qualitative and vague insults might banish this discussion. Then I'd have to start another self-aggrandizing thread about what envtl news I think is important. Nobody wants that
In re, Calif put SB901 into law 2018 September. Will spend $1 billion over 5 years on forest-fuel management. Which might include some rakes here and there, but they are not primary modern tools for this. Worst imaginable forest-fuel management can be read about in relation to 1871 Peshtigo fire. Nothing like that in Calif. Or Siberia.
I'll link just one article here, and save the rest for another forum: LATimes: Trump opens new war with California over wildfires, seeking to slash payments for firefighting on federal land "As California prepares for what some officials fear will be another devastating fire season, the U.S. Department of Agriculture and U.S. Forest Service are withholding reimbursements that state fire agencies say are owed for battling wildfires on federal lands last year. Instead of fulfilling California’s full $72-million reimbursement request, the Forest Service conducted an audit of the California Fire Assistance Agreement and now accuses the state of overbilling. ... Under the current assistance agreement, which runs from 2015 to 2020, the state calculates those costs by averaging the salaries, benefits and other indirect expenses tied to the work of firefighters, according to Cal OES Fire Chief Brian Marshall. ... As a result of the audit, the federal government is now withholding more than $9 million of the original $72 million reimbursement request. ..." Apparently Uncle Sam owns 60% of California's forested lands. I don't yet see figures for portions burned or distribution of ignition points.
Boeing 737-MAX / MCAS update. After newly strengthened FAA testing, digging far deeper than before (and beyond the entire modern 737 flight history), revealed more serious problems in June, Boeing is fundamentally changing the flight control software architecture to make it more fault tolerant, detecting a greater scope of faults.. Not simply just using both sensors and both flight computers (before the grounding, only one used at a time, alternating between flights) to detect stuck or faulty sensors, but also dual computers monitoring each other to detect other errors such as cosmic ray bit flips in critical places. (The FAA was carefully spear fishing here, not just applying random bit flips.) When they don't agree, rather than causing a dive or uncommanded action, they will take no action and hand control back to the pilots. Newly stringent FAA tests spur a fundamental software redesign of Boeing’s 737 MAX flight controls
Global Trends in Renewable Energy Investment 2019 Download a report: Frankfurt School: GTR covers decade 2010-2019. Solar investment still outpacing wind.
Nice charts. Ok, I only read the abstract and looked at the charts. Hidden in there, levelized cost of offshore wind has really come down the most in the most recent years. Encouraging sign where there is a more steady supply of renewable energy, day or night. Also, pretty cool:
Fig 3 posted @1078. What might have caused the steep drop in PV cost, 2010 through 2012? Timing is right for US injection of money into R&D after 2009. But if that were causative, would we not have heard about it already? Shouted from rooftops?
Looking at longer trends, the steep 2010-2012 drop appears to have caught back up to the prior trend. I have been following solar PV for good while, but don't recall any particular technology improvement at the time. My best guess is economies of scale. Germany really started deep incentives for solar around that time and U.S. federal solar tax credits were getting going then as well. China, of course took off rapidly with PV deployments as well.