danielravennest

danielravennest t1_jdrc942 wrote

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).

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danielravennest t1_jd90e6s wrote

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.

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danielravennest t1_jd8zgzp wrote

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.

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danielravennest t1_jd8xys1 wrote

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.

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danielravennest t1_jd4lpvz wrote

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.

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danielravennest t1_jcziaew wrote

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.

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danielravennest t1_jc84ysh wrote

> 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.

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danielravennest t1_jc22hwt wrote

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.

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danielravennest t1_jbtisbu wrote

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.

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danielravennest t1_jbt9nfl wrote

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.

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danielravennest t1_jbt7cn8 wrote

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.)

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danielravennest t1_jamzcnl wrote

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.

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danielravennest t1_jajhve6 wrote

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.

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