Researchers find a key clue to the evolution of bony fish and tetrapods.
- A new study says solar and lunar tide impacts led to the evolution of bony fish and tetrapods.
- The scientists show that tides created tidal pools, stranding fish and forcing them to get out of the water.
- The researchers ran computer simulations to get their results.
Tides influenced by the sun and the moon were likely the reason why fish developed limbs and early tetrapods evolved, found new research.
The groundbreaking study took a look at tides during the Late Silurian—Devonian periods, which happened between 420 million years ago and 380 million years ago.
The scientists built their work on the theory that the Moon's mass and specific location along its orbit can greatly affect vast tidal ranges across Earth and can create tidal pools. Because they are isolated from each other, the pools provided the biological motivation for fish stranded by high tides to eventually grow limbs.
The study involved researchers from UK's Bangor University and Oxford University as well as Uppsala University in Sweden. They devised very detailed numerical simulations that proved the existence of large tides during the period they studied. They are first to tie tidal hydrodynamics to an evolutionary biological event, states the press release from the University of Oxford.
To come up with the simulations, the scientists employed paleogeography, the study of historical geography, to reconstruct the Earth's continents within the numerical model. The calculations showed tides over four meters happening around the South China block. That area holds the known origin site of the earliest bony fish we know and has been a treasure-trove of the earliest fossils of that nature. Geological evidence also supports changes in tides to be lined to these fossils.
Neil deGrasse Tyson Explains the Tides
"Large tidal ranges could have fostered both the evolution of air-breathing organs in osteichthyans to facilitate breathing in oxygen-depleted tidal pools, and the development of weight-bearing tetrapod limbs to aid navigation within the intertidal zones," states the paper.
The researchers believe further tidal simulations from early Earth can be used to recreate that far past with greater detail. The findings can help us understand more what roles tides played in diversifying early vertebrates or in causing extinction events.
Check out the study published in Proceedings of the Royal Society A.
Tyson dives into the search for alien life, dark matter, and the physics of football.
- Astrophysicist Neil deGrasse Tyson joins us to talk about one of our favorite subjects: space.
- In the three-chaptered video, Tyson speaks about the search for alien life inside and outside of the Goldilocks Zone, why the term "dark matter" should really be called "dark gravity," and how the rotation of the Earth may have been the deciding factor in a football game.
- These fascinating space facts, as well as others shared in Tyson's books, make it easier for everyone to grasp complex ideas that are literally out of this world.
Gravitational wave researchers observe black holes of different sizes colliding for the first time.
- Gravitational wave researchers at LIGO and Virgo observatories spot black holes of different sizes colliding.
- The finding is unusual because previous black hole mergers involved partners of similar size.
- The new information re-confirms Einstein's theory of relativity.
Gravitational wave researchers discovered a very unusual merger of black holes 2.4 billion light-years away. They spotted a collision where one black hole was almost four times larger than another, expanding our understanding of such space cataclysms with help from Einstein (and even Elvis).
All mergers detected previously involved partners of comparable sizes. The event detected on April 12th, 2019 was called "exceptional" by Maya Fishbach, an astrophysicist at the University of Chicago in Illinois. What she and her colleagues found proves that very unevenly matched black hole pairs exist. "This is the first event in which we can confidently say the mass-ratio is not one," she stated during an online meeting of the American Physical Society.
The research was carried out in collaboration between the Laser Interferometer Gravitational-Wave Observatory (LIGO) — twin detectors in Washington and Louisiana — as well as the Virgo observatory near Pisa, Italy. They both detected the merger. One of the black holes observed was 30 times more massive than the sun and was spinning, said the scientists, while the other had a mass about eight times that of the sun.
In an amusing note, the scientists say that the very different masses created gravitational waves at multiple frequencies, which were actually in harmony with an Elvis Presley song. This cosmic music also confirms yet again Einstein's theory of general relativity.
Normally, two spiraling black holes of the same size would emit a single frequency, which would be double the rate at which they are orbiting one another, explains Science Magazine. In this case, as predicted by Einstein, the very different masses, also produce overtones - weaker waves at higher frequencies. And if you were to transpose these frequencies to piano notes and intervals, you would get the beginning of Presley's classic "I Can't Help Falling in Love with You."
The scientists hope that this uniqueness of the detected event could help provide more information about how black holes form. Of special interest is how the variation in mass could have arisen. Under one scenario, the pair could be the result of two massive stars who were orbiting each other, collapsing into black holes. Under another theory, the black holes could have formed independently and found each other in dense star clusters.
You can read more of the new findings on the arXiv preprint server.
The changes in brain structure aren't the only bodily changes caused by zero gravity.
- A new study finds that long term weightlessness can cause changes in brain structure, with an increase in white matter lasting a year after returning to Earth.
- The researchers believe it to be caused by an increase in fluid pressure on the brain.
- Potential solutions include creating artificial gravity.
I think my desire to go to space just declined a bit.
Eleven astronauts, ten men and one woman, were given MRI tests before they went for extended stays on the International Space Station. They were then given follow up scans the day after their return and at several points during the year after.
Not only did the researchers find that long-term exposure to zero-gravity increased the amount of cerebrospinal fluid in the brain, but that the amount of white matter in the brain increased as well. Several of the astronauts also had deformed pituitary glands, the gland that tells all the others what to do, as a result of the increased pressure on it.
These changes lasted for some time, just as other astronauts' vision problems have continued for years after returning to Earth. This suggests that some of the effects, particularly the increased amount of fluid, might be permanent. The higher amount of fluid also flowed through the cerebral aqueduct at an increased velocity.
The researchers hypothesized that these changes, like the previously mentioned vision problems, were caused by increased pressure in the head itself caused by an increased amount of fluid present, including blood. While Earth's gravity causes fluid to flow out of the head and pool towards the lower part of the body, weightlessness removes this tendency, and fluids begin to shift their locations. This effect has been known for a while and is also why many astronauts look like they skipped leg day or have puffy faces when they take pictures in space.
What does this mean? Are astronauts in danger?
It is too early to say what these changes to the brain mean. While some of the changes are associated with other symptoms, none of those have been seen in any of the astronauts yet.
However, ideas for how to reduce the build-up of fluids in the head are already being put forward. One suggestion is to create artificial gravity through the rotation of a centrifuge, like the spaceship in "2001: A Space Odyssey" has, or to create negative pressure around the lower parts of the body to draw fluid to them. Either of these mechanisms would cause less fluid to remain in the head.
The human body evolved to function decently in an environment where gravity is always a factor. As humanity ventures out towards the stars, the problem of how to keep that body working in such an alien environment will be a substantial obstacle. However, if we can solve the problem of getting into space in the first place, the issue of keeping fluid out of our heads seems comparatively simple.
An astrophysicist proposes new designs for stellar engines that can move a solar system.
- An astrophysicist proposes two new designs for stellar engines.
- The engines would be able to move our sun and whole solar systems.
- Moving the sun would be necessary to avoid collisions with supernovas and other space catastrophes.
Advancing space travel generally involves building more powerful and efficient engines for space vehicles like rockets or shuttles. But what if instead of an individual spacecraft, you took our whole solar system on a ride through the galaxy by moving the sun? Such is the not-too-modest proposal of nuclear astrophysicist Matthew Caplan from Illinois State University. He published his designs for stellar engines in the December 2019 issue of the peer-reviewed journal Acta Astronautica.
In the paper, Caplan envisions two stellar engine designs, with one of them based on the idea of encapsulating the sun in a megastructure that would take advantage of its energy. Another engine would make use of a giant sail to move the solar system by about 50 light years during the course of a million years.
Why would anyone even want to do this? One big reason would be to move the solar system if we're anticipating running into a mega-explosion from a supernova or some such cataclysmic scenario. Of course, we'd need to be way more ahead technologically for any such endeavor.
If you were to be moving the solar system, the convenient thing is that theoretically everything inside it would move along at the same time. Being pulled by the sun's gravity would keep the contents of the system in consistent orbit.
One of the stellar engine designs involves a thin mirror-like solar sail, like the “Shkladov thruster". The reflective material would be thinner than a red blood cell. The sail would be positioned over the poles of the sun and would not be orbiting. It would be important to install it in such a way that it won't interfere with the Earth's temperature. This would also affect the direction in which we'd be steering the solar system.
How a Supernova Could Nuke Us
A nearby star system may “go supernova".
Thrust for the sail design would be created by solar radiation reflecting onto the mega-mirror. This is definitely not the fastest way to travel, with the sun being pushed along at the rate of 100 light-year in 230 million years. That's actually not fast enough to get out of the way of a supernova explosion, admits Caplan.
What would work better is a speedier “active" thruster, called the “Caplan thruster" by Kurzgesagt, which initially approached Caplan to design such engines. It would be propelled by thermonuclear blasts of photon particles. This thruster is a modified version of the “Bussard ramjet," conceptualized in the 1960s, which works on fusion energy. The engine would need millions of tons of fuel per second to function, creating fusion from matter it collects in the solar wind by utilizing a giant electromagnetic field. More energy would also be gathered by a Dyson sphere megastructure, built around the sun.
Caplan imagines the engine having two jets, with one using hydrogen pointed at the sun, to prevent colliding with it, and another, employing helium, directed away from the star. This would cause net momentum, like from a tug boat, and move the thruster forward.
The astrophysicist calculates this type of thruster would be fast enough to escape a supernova. It could also redirect the galactic orbit of our solar system in as little as 10 million years.
"A stellar engine produces a small net acceleration of the star, not large enough to disrupt the planetary system on short timescales, but sufficiently large to deflect the star and planetary system in its galactic orbit by many light-years given millions of years," wrote Caplan in the paper.
If it appears that talking about millions of years is impractical and too long a stretch of time, keep in mind that a different time scale applies in space and what is being proposed is for much more accomplished civilizations than ours. Caplan thinks “a catastrophe such as a supernova could likely be predicted millions of years in advance, at a minimum, for an advanced civilization with detailed understanding of star formation and the supernova mechanism."
How to Move the Sun: Stellar Engines
Check out the explanatory video from Kurzgesagt for more information.