danielravennest
danielravennest t1_jdr9mjg wrote
Reply to comment by [deleted] in 3 years ago I built this telescope in my parents' garage. It's since shown me supernovae, comets, 3 dwarf planets and been looked through by thousands of other people. by __Augustus_
Amateur Telescope Making. There's a list of books and links in the article.
danielravennest t1_jdr976i wrote
Reply to comment by Conscious_Exit_5547 in 3 years ago I built this telescope in my parents' garage. It's since shown me supernovae, comets, 3 dwarf planets and been looked through by thousands of other people. by __Augustus_
Astronomical telescopes are designed to focus at "infinity", since everything is so far away. Also if you are spying, fold up opera glasses or binoculars are less obvious.
danielravennest t1_jddsu44 wrote
Reply to comment by teehuis in A New Mission Will Search for Habitable Planets at Alpha Centauri by Aeromarine_eng
You don't. You program them ahead of time. We rarely send commands to the Voyagers any more. They are a light-day away. Mostly we just point a Deep Space Network dish at them at the expected time, and collect the data.
danielravennest t1_jd90e6s wrote
Reply to comment by The_Solar_Oracle in A New Mission Will Search for Habitable Planets at Alpha Centauri by Aeromarine_eng
In particular, the Sun is a gravitational lens. If you travel about 800 AU in the opposite direction from Alpha Centauri, you can look back and see what is there in great detail, because the lens is 2 million km in diameter. One reason to be that far out is to make it easy to block out the Sun itself, including prominances and the solar corona.
Centauri is 276,000 AU, so using the Sun is a lot easier mission.
danielravennest t1_jd8zgzp wrote
Reply to comment by teehuis in A New Mission Will Search for Habitable Planets at Alpha Centauri by Aeromarine_eng
Current technology is nuclear reactors and electric propulsion. We can feasibly get to 300 km/s with multiple stages. That makes Alpha Centauri 4250 years away.
But due to the "arrival paradox", a trip that long doesn't make sense to try. Assuming technology will keep improving, a later ship with better technology will be faster, and pass the older, slower ship before it arrives. Consider what our technology was like in 2,200 B.C. (4250 years ago).
Only if technology reaches a dead end, or the trips are short enough to not be passed before arrival (perhaps 50-100 years) does it make sense to try.
Our tech is already good enough to travel about 3 times the speed of the Voyagers, and catch up with them about the time their power gets so low we lose contact. If we really wanted to we could do that. We won't, since there are better and closer missions we can do instead.
danielravennest t1_jd8xys1 wrote
Reply to comment by UnknownStrikex in A New Mission Will Search for Habitable Planets at Alpha Centauri by Aeromarine_eng
Yet another method is using the Sun both as a power source, and a gravitational lens to focus the beam on a ship in transit. Starshot is limited by the laser array size. The probe quickly gets too far to maintain beam focus.
So instead you build your laser array near the Sun, where power is plentiful. To start with you aim the beam directly at the vehicle. When it gets too far you switch to a relay mirror at ~800 AU. The Sun bends light by its gravity. In this case it makes a lens with a 2 million km diameter, which gives you astounding resolution.
The beam is used by the ship to power a particle accelerator. The first part of the trip the accelerator is pointed aft to speed up. Later it points the other way to slow down. Going the other way, your communications will be focused back to the relay mirror, so you can get data back.
danielravennest t1_jd8w8wh wrote
Reply to comment by starhoppers in A New Mission Will Search for Habitable Planets at Alpha Centauri by Aeromarine_eng
It's hard to beat a laser-pushed lightsail going 1/8th the speed of light. The downside is the spacecraft will be tiny.
danielravennest t1_jd50pp3 wrote
Reply to comment by ToolemeraPress in The Internet Archive is defending its digital library in court today by OutlandishnessOk2452
They could follow Disney and Spotify, and make all the content available for a reasonable monthly subscription.
The Internet Archive doesn't have a lot of new books. Most of the physical books that were donated and scanned were library discards or other old copies.
danielravennest t1_jd4mniy wrote
Reply to comment by Mr_ToDo in The Internet Archive is defending its digital library in court today by OutlandishnessOk2452
Quite a few of my ebooks are open-source textbooks, unrestricted ones from the National Academies, or older ones out of copyright. But they don't cover everything I'm interested in.
danielravennest t1_jd4lpvz wrote
Reply to comment by EROSENTINEL in The Internet Archive is defending its digital library in court today by OutlandishnessOk2452
Yes. The three previous houses I lived in needed reinforcement, since that many books are heavy. My current home is 70 years old, and was built stronger. Even so, I have to spread the books around the house to avoid overloading the floor.
Side benefits are noise reduction across the house, and the thermal mass reduces heating and A/C cost as the house temperature varies less.
danielravennest t1_jd4kie4 wrote
Reply to comment by Carbidereaper in The Internet Archive is defending its digital library in court today by OutlandishnessOk2452
Z-library is good for new stuff, but the Internet Archive is better for old or obscure books.
danielravennest t1_jcziaew wrote
Reply to The Internet Archive is defending its digital library in court today by OutlandishnessOk2452
I've been borrowing IA books that have "two week loans", downloading the Adobe Digital Editions pdf, using a Calibre plug-in to remove the restrictions, then "cleaning up" the copy (remove blank pages, reduce page background or increase contrast, add bookmarks if needed, and optimize file size). If the IA ever goes down, I'll have a backup.
I'm not against buying books, I have thousands of physical ones. But I believe sharing knowledge is an absolute good.
danielravennest t1_jc84ysh wrote
Reply to comment by Ape_Togetha_Strong in In defence of dark energy | Nobel Laureate and dark matter pioneer James Peebles answers critics of dark energy. by IAI_Admin
> popsci "journalists" like to make sound as sensationalized as possible.
Of course they do. We live in a clickbaity world, because they need to attract eyeballs to earn ad revenue. That's why you see headlines about asteroids all the time. But when you read the article, you find they will miss Earth by millions of miles (usually) and are not a danger. But you already clicked the story, and ad counter went up.
danielravennest t1_jc22hwt wrote
Reply to comment by CodeCocina in Milky Way over Uruguayan Lighthouse. Credit: Mauricio Salazar by Davicho77
It is from the Greek, meaning "milky circle". The galaxy is a flattened disk, and we are inside it. So from our viewpoint it looks like a circle around the sky. They didn't have telescopes, so all they could see is a faint white band.
This is an all-sky view with our galaxy oriented horizontally. Sagittarius is a dwarf galaxy mostly hidden by the center of ours. It is on the other side. It is the nearest galaxy to our own, at 50,000 light years, and orbits the Milky Way. The two blobs on the lower right are the Magellanic Clouds, the next nearest, and also orbit the Milky Way. They are about 3 times farther, and much larger than the Sagittarius dwarf. Both will end up merged with the Milky Way eventually.
danielravennest t1_jbttgdt wrote
Reply to comment by ShittyBeatlesFCPres in Space sector reacts to collapse of Silicon Valley Bank by TransientSignal
Here's the official FDIC Press Release
danielravennest t1_jbtk39z wrote
Reply to comment by _zerokarma_ in Space Force allocates three historic Cape Canaveral launch pads to four companies by Azurebluenomad
Space Command and Space Division were the parts of the USAF that previously did this job.
danielravennest t1_jbtjdwx wrote
Reply to comment by NerfSchlerfen in Space Force allocates three historic Cape Canaveral launch pads to four companies by Azurebluenomad
Falcon Heavy is planned to be the launcher for parts of the Lunar Gateway station in lunar orbit. Starship, which has its own launch pads, is going to be the excessively oversized lunar lander, plus tanker flights to refill it in low Earth orbit.
danielravennest t1_jbtisbu wrote
Reply to comment by Uhgfda in Space Force allocates three historic Cape Canaveral launch pads to four companies by Azurebluenomad
No, they will be shared use. A "Launch complex" is pretty large because of the safety buffer zone needed around it. These were originally set up for larger rockets. A near empty Falcon 9 and these smaller rockets going up are smaller hazards, so they can be spaced enough to not damage each other, but still share one launch complex.
Also, SpaceX doesn't use the landing pads very often any more, and when they do the rocket is gone in a few hours. As long as the new rockets aren't trying to launch at the same time (i.e. loaded with fuel), they don't really conflict.
danielravennest t1_jbt9nfl wrote
Reply to comment by DragonDai in Ancient dormant viruses found in permafrost, once revived, can infect amoeba. Findings hint at a much bigger problem—as the planet warms and the permafrost melts, there is a chance of viruses emerging that are capable of infecting humans by Wagamaga
I would doubt it. That same capitalism is massively increasing solar panel production because there is a buck (or Chines Yuan since most of them are made there) to be made:
>"According to the Silicon Industry Branch, China’s silicon material production capacity will reach 2.4 million tons in 2023, double that of last year." Source
Silicon being the material solar cells are made of. It takes about 2 grams per Watt to make the cells. So that much capacity theoretically could supply 1200 GW of solar per year, or 240 GW of nuclear plant output equivalent. World nuclear capacity is ~400 GW. So you would be adding 60% of that every year. That's a whole lot of clean power.
danielravennest t1_jbt7cn8 wrote
Reply to comment by sagitt12 in Ancient dormant viruses found in permafrost, once revived, can infect amoeba. Findings hint at a much bigger problem—as the planet warms and the permafrost melts, there is a chance of viruses emerging that are capable of infecting humans by Wagamaga
It would give you a nasty burn, same as the heating element on a stove burner or toaster, which are about the same temperature.
The correct answer is "don't stand close to volcanic eruptions" because they can kill you in several ways (poison gases, heat, rock falls, etc.)
danielravennest t1_jb5ots6 wrote
Reply to comment by B-Bog in Humans Started Riding Horses 5,000 Years Ago, New Evidence Suggests by geoxol
If you had lived over a hundred years ago, keeping horses would seem as normal as keeping cars are today. The US horse population fell dramatically after 1920 as cars became common.
danielravennest t1_jan1f25 wrote
Reply to comment by TheKingPotat in NASA: Several large asteroids projected to zoom past Earth this week by 1080krld
It will just appear as a streak or series of dots, like satellites do already. It will be visible to the unaided eye if you are in the right place to see it at its closest.
danielravennest t1_jamzcnl wrote
Reply to comment by TheKingPotat in NASA: Several large asteroids projected to zoom past Earth this week by 1080krld
It will be moving too fast for Hubble or Webb to track during the flyby (and Webb can't point towards Earth and the Sun). But they can try when it is farther away and appears to move more slowly. Some weather and military satellites in GEO may be able to spot it, and every telescope and radar on the ground will give it a try. Osiris-REX will be chasing it, and will try to boop Apophis like it did for the sample collection on Bennu, but the sample head is gone now.
danielravennest t1_jajhve6 wrote
Reply to comment by the_fungible_man in NASA: Several large asteroids projected to zoom past Earth this week by 1080krld
Risk is based on size and impact probability. The asteroid with the highest risk ranking is 101955 Bennu. But it won't have a chance of impact until 2178.
We already sent a probe to it, and grabbed a sample that is due to land on Sept. 24th.
Everything else that shows up in news stories is either lower chance of impact, too small to do much damage, or so far in the future we're not worried yet.
On April 13th, 2029 the asteroid 99942 Apophis will pass only 31,600 km from the Earth's surface, but we know its orbit with 3 km uncertainty, so it will definitely miss us. The same probe that visited Bennu is being retasked to meet up with Apophis. There will probably be a lot of hype about that asteroid before it arrives.
Any other news story about asteroids approaching Earth are clickbait. If one that was a real hazard is discovered, it would be the top story in all the news media.
danielravennest t1_jdrc942 wrote
Reply to comment by LowVacation6622 in [NASA on Twitter] Newly-discovered asteroid 2023 DZ2 will pass Earth more than 100,000 miles (161,000 km) away–about half the distance to the Moon–making its close approach at 3:51 p.m. EDT (12:51 p.m. PDT) by ICumCoffee
The search programs have found nearly all the 1 km+ size "potentially hazardous objects" (come within 5% of the Earth's orbit size). They are working on the 140 meter and up size (city killers).