The Space Thread

[Guest]

Why Are Plants Green? To Reduce the Noise in Photosynthesis.

Plants ignore the most energy-rich part of sunlight because stability matters more than efficiency, according to a new model of photosynthesis.

 

From large trees in the Amazon jungle to houseplants to seaweed in the ocean, green is the color that reigns over the plant kingdom. Why green, and not blue or magenta or gray? The simple answer is that although plants absorb almost all the photons in the red and blue regions of the light spectrum, they absorb only about 90% of the green photons. If they absorbed more, they would look black to our eyes. Plants are green because the small amount of light they reflect is that color.

 

But that seems unsatisfyingly wasteful because most of the energy that the sun radiates is in the green part of the spectrum. When pressed to explain further, biologists have sometimes suggested that the green light might be too powerful for plants to use without harm, but the reason why hasn’t been clear. Even after decades of molecular research on the light-harvesting machinery in plants, scientists could not establish a detailed rationale for plants’ color.

 

Recently, however, in the pages of Science, scientists finally provided a more complete answer. They built a model to explain why the photosynthetic machinery of plants wastes green light. What they did not expect was that their model would also explain the colors of other photosynthetic forms of life too. Their findings point to an evolutionary principle governing light-harvesting organisms that might apply throughout the universe. They also offer a lesson that — at least sometimes — evolution cares less about making biological systems efficient than about keeping them stable.

 

The mystery of the color of plants is one that Nathaniel Gabor, a physicist at the University of California, Riverside, stumbled into years ago while completing his doctorate. Extrapolating from his work on light absorption by carbon nanotubes, he started thinking of what the ideal solar collector would look like, one that absorbed the peak energy from the solar spectrum. “You should have this narrow device getting the most power to green light,” he said. “And then it immediately occurred to me that plants are doing the opposite: They’re spitting out green light.”

 

In 2016, Gabor and his colleagues modeled the best conditions for a photoelectric cell that regulates energy flow. But to learn why plants reflect green light, Gabor and a team that included Richard Cogdell, a botanist at the University of Glasgow, looked more closely at what happens during photosynthesis as a problem in network theory.

 

The first step of photosynthesis happens in a light-harvesting complex, a mesh of proteins in which pigments are embedded, forming an antenna. The pigments — chlorophylls, in green plants — absorb light and transfer the energy to a reaction center, where the production of chemical energy for the cell’s use is initiated. The efficiency of this quantum mechanical first stage of photosynthesis is nearly perfect — almost all the absorbed light is converted into electrons the system can use.

 

But this antenna complex inside cells is constantly moving. “It’s like Jell-O,” Gabor said. “Those movements affect how the energy flows through the pigments” and bring noise and inefficiency into the system. Quick fluctuations in the intensity of light falling on plants — from changes in the amount of shade, for example — also make the input noisy. For the cell, a steady input of electrical energy coupled to a steady output of chemical energy is best: Too few electrons reaching the reaction center can cause an energy failure, while “too much energy will cause free radicals and all sorts of overcharging effects” that damage tissues, Gabor said.

 

Gabor and his team developed a model for the light-harvesting systems of plants and applied it to the solar spectrum measured below a canopy of leaves. Their work made it clear why what works for nanotube solar cells doesn’t work for plants: It might be highly efficient to specialize in collecting just the peak energy in green light, but that would be detrimental for plants because, when the sunlight flickered, the noise from the input signal would fluctuate too wildly for the complex to regulate the energy flow.

 

Instead, for a safe, steady energy output, the pigments of the photosystem had to be very finely tuned in a certain way. The pigments needed to absorb light at similar wavelengths to reduce the internal noise. But they also needed to absorb light at different rates to buffer against the external noise caused by swings in light intensity. The best light for the pigments to absorb, then, was in the steepest parts of the intensity curve for the solar spectrum — the red and blue parts of the spectrum.

 

The model’s predictions matched the absorption peaks of chlorophyll a and b, which green plants use to harvest red and blue light. It appears that the photosynthesis machinery evolved not for maximum efficiency but rather for an optimally smooth and reliable output.

 

Cogdell wasn’t fully convinced at first that this approach would hold up for other photosynthetic organisms, such as the purple bacteria and green sulfur bacteria that live underwater and are named for the colors their pigments reflect. Applying the model to the sunlight available where those bacteria live, the researchers predicted what the optimal absorption peaks should be. Once again, their predictions matched the activity of the cells’ pigments.

“When I realized how fundamental this was, I found myself looking in the mirror and thinking: How could I be so dumb not to think about this before?” Cogdell said.

 

(There are plants that don’t appear green, like the copper beech, because they contain pigments like carotenoids. But those pigments are not photosynthetic: They typically protect the plants like sunscreen, buffering against slow changes in their light exposure.)

 

“It was extraordinarily impressive, I think, to explain a pattern in biology with an incredibly simple physical model,” said Christopher Duffy, a biophysicist at Queen Mary University of London, who wrote an accompanying commentary on the model for Science. “It was nice to see a theoretically led work that understands and promotes the idea that it is robustness of the system that seems to be the evolutionary driving force.”

 

Researchers hope the model can be used to aid in the design of better solar panels and other solar devices. Although the efficiency of photovoltaic technology has advanced considerably, “I would say it’s not a solved problem in terms of robustness and scalability, which is something that plants have solved,” said Gabriela Schlau-Cohen, a  physical chemist at the Massachusetts Institute of Technology.

 

Gabor has also set his mind on someday applying the model to life beyond Earth. “If I had another planet and I knew what its star was like, could I guess what photosynthetic life might look like?” he asked. In the code of his model — which is publicly available — there is an option to do exactly that with any selected spectrum. For now, the exercise is purely hypothetical. “In the next 20 years, we probably will have enough data on an exoplanet to be able to [answer] that question,” Gabor said.

[dockers_strike]

Fuck me, it worked! Or rather it made the 'hop'!
 

 

[Dougie Do'ins]

2 hours ago, dockers_strike said:

Fuck me, it worked! Or rather it made the 'hop'!
 

 

WTF is that all about ?

[Dougie Do'ins]

SpaceX: Musk's 'Mars ship' prototype aces 150m test flight

 

https://www.bbc.co.uk/news/science-environment-53659702

[Anubis]

How close is too close?

 

https://www.google.co.uk/amp/s/www.businessinsider.com/car-size-asteroid-2020qg-missed-earth-by-2000-miles-2020-8%3famp

 

 

A car-size asteroid called 2020 QG nearly hit Earth on Sunday - Business Insider

Dave Mosher and Morgan McFall-Johnsen 

Aug 17, 2020, 7:17 PM 

 

A diagram of asteroid 2020 QG flying past Earth on August 16. The yellow arrow shows the direction of the sun, blue shows Earth's direction, and the green hatches show the asteroid's location every 30 minutes. 

Minor Planet Center/International Astronomical Union

• An asteroid the size of a car flew within about 1,830 miles of Earth this weekend — closer than any known space rock has ever come without crashing into the planet.
• A NASA-funded program detected the asteroid, called 2020 QG, six hours after its close approach.
• If the asteroid had hit Earth, it probably would have exploded in the atmosphere in an airburst too high up to do any damage on the ground.
• But the near miss highlights a major blind spot in Earth's programs to search for dangerous asteroids.
• Visit Business Insider's homepage for more stories.

A car-size asteroid flew within about 1,830 miles (2,950 kilometers) of Earth on Sunday.

That's a remarkably close shave — the closest ever recorded, in fact, according to asteroid trackers and a catalog compiled by Sormano Astronomical Observatory in Italy. 

 

Because of its size, the space rock most likely wouldn't have posed any danger to people on the ground had it struck our planet. But the close call is worrisome nonetheless, since astronomers had no idea the asteroid existed until after it passed by.

 

"The asteroid approached undetected from the direction of the sun," Paul Chodas, the director of NASA's Center for Near Earth Object Studies, told Business Insider. "We didn't see it coming."

 

Instead, the Palomar Observatory in California first detected the space rockabout six hours after it flew by Earth.

 

Chodas confirmed the record-breaking nature of the event: "Yesterday's close approach is closest on record, if you discount a few known asteroids that have actually impacted our planet," he said.

 

NASA knows about only a fraction of near-Earth objects (NEOs) like this one. Many do not cross any telescope's line of sight, and several potentially dangerous asteroids have snuck up on scientists in recent years. If the wrong one slipped through the gaps in our NEO-surveillance systems, it could kill tens of thousands of people. 

 

2020 QG flew over the Southern Hemisphere

This recent near-Earth asteroid was initially called ZTF0DxQ but is now formally known to astronomers as 2020 QG. Business Insider first learned about it from Tony Dunn, the creator of the website orbitsimulator.com.

 

"Newly-discovered asteroid ZTF0DxQ passed less than 1/4 Earth diameter yesterday, making it the closest-known flyby that didn't hit our planet," Dunn tweeted on Monday. He shared the animation below, republished here with permission.

 

The sped-up simulation shows the approximate orbital path of 2020 QG as it careened by at a speed of about 7.7 miles per second (12.4 kilometers per second) or about 27,600 mph.

 

Early observations suggest the space rock flew over the Southern Hemisphere just after 4 a.m. Universal Time (midnight ET) on Sunday.

 

The animation above shows 2020 QG flying over the Southern Ocean near Antarctica. However, the International Astronomical Union's Minor Planet Center calculated a slightly different trajectory. The group's rendering (shown at the beginning of this story), suggests the asteroid flew over the Pacific Ocean hundreds of miles east of Australia.

 

Not dangerous, but definitely not welcome

As far as space rocks go, 2020 QG wasn't too dangerous.

 

Telescope observations suggest the object is between 6 feet (2 meters) and 18 feet (5.5 meters) wide — somewhere between the size of a small car and an extended-cab pickup truck. But even if it was on the largest end of that spectrum and made of dense iron (most asteroids are rocky), only small pieces of such an asteroid may have reached the ground, according to the "Impact Earth" simulator from Purdue University and Imperial College London.

 

Such an asteroid would have exploded in the atmosphere, creating a brilliant fireball and unleashing an airburst equivalent to detonating a couple dozen kilotons of TNT. That's about the same as one of the atomic bombs the US dropped on Japan in 1945. But the airburst would have happened about 2 or 3 miles above the ground, so it wouldn't have sounded any louder than heavy traffic to people on the ground.

 

This doesn't make the asteroid's discovery much less unnerving, though — it does not take a huge space rock to create a big problem.

A simulation of a 66-foot-wide (20-meter-wide) asteroid burning up in Earth's atmosphere. 

Darrel Robertson/NASA Ames

Take, for example, the roughly 66-foot-wide (20-meter) asteroid that exploded without warning over Chelyabinsk, Russia, in February 2013. That space rock created a superbolide event, unleashing an airburst equivalent to 500 kilotons of TNT — about 30 Hiroshima nuclear bombs' worth of energy. The explosion, which began about 12 miles (20 kilometers) above Earth, triggered a blast wave that shattered windows in six Russian cities and injured about 1,500 people.

 

And in July 2019, a 427-foot (130-meter) asteroid called 2019 OK passed within 45,000 miles (72,400 kilometers) of our planet, or less than 20% of the distance between Earth and the moon. Astronomers detected that rock less than a week before its closest approach, leading one scientist to tell The Washington Post that the asteroid essentially appeared "out of nowhere."

 

In an unlikely direct hit to a city, such a wayward space rock might kill tens of thousands of people.

 

NASA is actively scanning the skies for such threats, as Congress has required it to do since 2005. However, the agency is mandated to detect only 90% of "city killer" space rocks larger than about 460 feet (140 meters) in diameter.

 

In May 2019, NASA said it had found less than half of the estimated 25,000 objects of that size or larger. And of course, that doesn't count smaller rocks such as the Chelyabinsk and 2019 OK asteroids.

 

Objects that come from the direction of the sun, meanwhile — like 2020 QG — are notoriously difficult to spot.

 

"There's not much we can do about detecting inbound asteroids coming from the sunward direction, as asteroids are detected using optical telescopes only (like ZTF), and we can only search for them in the night sky," Chodas said. "The idea is that we discover them on one of their prior passages by our planet, and then make predictions years and decades in advance to see whether they have any possibility of impacting."

 

NASA has a plan to address these gaps in its asteroid-hunting program. The agency is in the early stages of developing a space telescope that could detect asteroids and comets coming from the sun's direction. NASA's 2020 budget allotted nearly $36 million for that telescope, called the Near-Earth Object Surveillance Mission. If funding continues, it could launch as early as 2025.

 

[Bjornebye]

Fucking drink drivers. 

[johnsusername]

https://www.theguardian.com/film/2020/aug/23/the-man-who-tried-to-contact-aliens-from-his-grandmas-living-room

 

The man who tried to contact aliens from his grandma’s living room

[Mudface]

On 05/08/2020 at 20:35, Dougie Do'ins said:

SpaceX: Musk's 'Mars ship' prototype aces 150m test flight

 

https://www.bbc.co.uk/news/science-environment-53659702

It went 150 metres up.

 

Musk: "Mars is looking real."

[dockers_strike]

On 23/08/2020 at 12:50, johnsusername said:

https://www.theguardian.com/film/2020/aug/23/the-man-who-tried-to-contact-aliens-from-his-grandmas-living-room

 

The man who tried to contact aliens from his grandma’s living room

SETI and Seth Shostak would have been pretty pissed off if he had succeeded!

[johnsusername]

[dockers_strike]

I love these vids by David Kipping. Whether you agree with his thoughts and presentations is pretty immaterial. They are thought provoking as he doesnt claim to be right or wrong.

 

 

[Mudface]

1 hour ago, dockers_strike said:

I love these vids by David Kipping. Whether you agree with his thoughts and presentations is pretty immaterial. They are thought provoking as he doesnt claim to be right or wrong.

 

 

Thanks for that, really interesting stuff. I watched another one of his and it's excellent too-

 

 

[TheHowieLama]

The woman in blue has just realised this photo is going to be her legacy.

 

[dockers_strike]

Not sure if previously posted, pictures of Mars in 4k.

 

Loved it when the guy said Mars is the only planet we know of inhabited only by robots!

 

 

[dockers_strike]

Starship makes it's 2nd 'hop'!

 

 

[Bjornebye]

46 minutes ago, dockers_strike said:

Not sure if previously posted, pictures of Mars in 4k.

 

Loved it when the guy said Mars is the only planet we know of inhabited only by robots!

 

 

Thats a cool statement but I guarantee now that if I was to be the first man from Earth to walk on that red bastard and was enjoying it, my exes mum would walk past and blank me. 

[Anubis]

On 28/08/2020 at 21:28, TheHowieLama said:

The woman in blue has just realised this photo is going to be her legacy.

 

Fucking cunt misappropriating the Star Fleet logo. Paramount should sue the dumpy twat.

[Stickman]

@latestinspace
Hoba, the largest meteorite ever discovered, still lies where it struck 80,000 yrs ago.

 

 

[Mudface]

12 minutes ago, Stickman said:

@latestinspace
Hoba, the largest meteorite ever discovered, still lies where it struck 80,000 yrs ago.

 

 

https://en.wikipedia.org/wiki/Hoba_meteorite

 

This is where the lizard people control us from.

[Guest]

18 minutes ago, Stickman said:

@latestinspace
Hoba, the largest meteorite ever discovered, still lies where it struck 80,000 yrs ago.

 

 

 

5 minutes ago, Mudface said:

https://en.wikipedia.org/wiki/Hoba_meteorite

 

This is where the lizard people control us from.

I love this type of stuff. That bad boy just flying around in space for billions of years waiting to smash into something and then after all that time it encounters a planet with an atmosphere that is able to show it what's up. Bad ass.

[Mudface]

Just now, Fluter in Dakota said:

 

I love this type of stuff. That bad boy just flying around in space for billions of years waiting to smash into something and then after all that time it encounters a planet with an atmosphere that is able to show it what's up. Bad ass.

Wanker of a meteorite. I bet when it crashed, all the early Namibians and animals for miles around pissed themselves laughing at it.

[Anubis]

Clearly just waiting for a strange storm and lightning strike before a Martian war machine emerges.

[dockers_strike]

Breaking news, scientist disclose they MAY have found evidence of life in the clouds of Venus with the detection of phosphine(?) gas!

 

At the moment this is the only link I found but BBC News is currently running the story.

 

https://www.helensburghadvertiser.co.uk/news/national-news/18719840.detection-phosphine-venuss-clouds-indicates-potential-life/

 

And another

 

https://www.nationalgeographic.com/science/2020/09/possible-sign-of-life-found-on-venus-phosphine-gas/

[Bjornebye]

11 minutes ago, dockers_strike said:

Breaking news, scientist disclose they MAY have found evidence of life in the clouds of Venus with the detection of phosphine(?) gas!

 

At the moment this is the only link I found but BBC News is currently running the story.

 

https://www.helensburghadvertiser.co.uk/news/national-news/18719840.detection-phosphine-venuss-clouds-indicates-potential-life/

 

And another

 

https://www.nationalgeographic.com/science/2020/09/possible-sign-of-life-found-on-venus-phosphine-gas/

Fuck me I was only saying the other day that they will start saying there are aliens to divert attention away from the fuck ups this and Trumps governments made 

[Jordy Brouwer]

22 minutes ago, dockers_strike said:

Breaking news, scientist disclose they MAY have found evidence of life in the clouds of Venus with the detection of phosphine(?) gas!

 

At the moment this is the only link I found but BBC News is currently running the story.

 

https://www.helensburghadvertiser.co.uk/news/national-news/18719840.detection-phosphine-venuss-clouds-indicates-potential-life/

 

And another

 

https://www.nationalgeographic.com/science/2020/09/possible-sign-of-life-found-on-venus-phosphine-gas/

Hope so but there are so many false alarms. I've read the headline "scientists may have discovered life..." so many times. 

 

Just hope they don't ask "take us to you're leader" or we are going to have to deploy expectations management.