From fruit flies to stars, learning is everywhere

  Fruit flies often appear on the experiment table of biologists. To see them clearly, you need to use a high-power magnifying glass. Stars travel all year round in the distant and vast universe. To see them clearly, you need to use an astronomical telescope. The two seem to be irrelevant, but Emory Bartos, a PhD in physics at Columbia University, is keen to explore them.
Appreciate the fruit fly dance

  Put a cut apple or orange on the table, and in less than half a day, you will harvest a group of uninvited guests-fruit flies. They danced around the fruit and feasted on them. You wave your hands impatiently, they spread out, but soon come together again. You may be thinking, how can there be such annoying things in the world! But did you know that little fruit flies appeared in the laboratories of many biologists and told us many secrets of life. Recently, they have taught us something new.

Emery Bartos

  Since animals came ashore 360 ​​million years ago, more and more complex ways of movement have been developed. Movement is essential for animals to escape from predators, find mates, and find food. Because the neural network is relatively simple, easy to reproduce and cultivate, fruit flies have become a good model for studying animal movement. But, fruit flies are so small, how can we see their walking? A video camera may be able to solve this problem.
  Emery Bartos customized such a camera for fruit flies. This camera is named FlyWalker and consists of a camera and computer analysis software. In the FlyWalker system, when the fruit fly “dancing” on the transparent glass, every dance step of it will be recorded by the high-speed camera. In order to figure out whether it is jumping “samba” or “waltz”, the computer will mark the six legs of the fruit fly as right back, right middle, right front, left back, left middle, and left front, respectively. Analyze the movement trajectory of each leg. After shooting for a period of time, the scientists got a video of the “national standard dance” of fruit flies. There are two common “dancing poses” for fruit flies, the “tripod” dance or the “four-legged” dance, supported by three legs, and the other three. Walk with swinging legs back and forth, or support on four legs and walk on the other two legs. Normal fruit flies basically “dance” at a fixed frequency. Once the “dance” of fruit flies is abnormal, whether it is too fast or too slow, FlyWalker can quickly distinguish it.
  Relying on this system, many fruit fly experiments were finally completed. Salis Mazman, a professor of microbiology at the California Institute of Technology, is dedicated to studying the influence of the gut flora of fruit flies on its movement, but no clear data has been found before. It wasn’t until FlyWalker that he discovered that the fruit flies with Lactobacillus brevis in the intestine walked “staggered” and “out of breath”, and walked much slower than the non-bacterial fruit flies, which verified his conjecture. The success of this experiment is inseparable from Bartos’s FlyWalker system. It is also because of FlyWalker. We can see Bartos’s name in many biological papers related to fruit flies.

FlyWalker records the “dancing posture” of fruit flies
Tracking Space Car Accident

  Although the fruit fly camera shines in the zoologist’s laboratory and makes Bartos famous in the biological world, he still prefers to look up at the stars and study astrophysics.
  Gold has been a symbol of wealth since ancient times, and now people are increasingly inseparable from it. Even if you don’t wear gold jewelry, you can still find it on your mobile phone and desktop computer. Every electronic product contains less than 0.1 gram of gold, and its corrosion resistance and electrical conductivity are favored by manufacturers. According to statistics, in 2018, the electronics industry used nearly 270 tons of gold.
  But where does gold come from? You may think that it is original to the earth and is buried in the earth’s crust. Is it really the case?

Bartos tracks the “car accident” of the black hole

  We know that hydrogen is the mother of elements, and many of the following elements are produced by hydrogen nuclear fusion, but in the tens of millions of years after the formation of the universe, there is no element heavier than iron. After the fusion of iron, There is no longer enough energy to support the nuclear fusion reaction to continue. So how did the following elements come into being?
  It turns out that when the planet is fully occupied by iron elements, the earth’s surface can no longer carry such heavy iron elements. They will collapse inward under the action of gravity, and eventually they will all pile together, forming a dense crowded side by side. Planet. The gravity of the iron element can even squeeze atoms to deform, neutralize electrons and protons to form neutrons, so we call this dense planet a “neutron star.”
  Scientists speculate that the neutron stars in the universe are orbiting in their respective orbits and are in peace with each other. Until 4.6 billion years ago, two neutron stars collided! The huge energy produced by the collision of neutron stars finally made the nuclear fusion reaction break the “iron” curse, and finally produced heavier elements including gold. The mass of gold produced in this “car accident” is about 3 to 13 times the mass of the earth. After the intense collision, the gold was scattered everywhere in the universe, and some of it came to the earth.
  So how can we prove whether this “car accident” 4.6 billion years ago really happened? Bartos analyzed the residual radioactive isotopes in an ancient meteorite that was 100 million years longer than the earth’s lifespan, and then compared these values ​​with the isotope ratios produced by computer-simulated neutron star collisions, and found that the two values ​​are almost complete. equal.
  But before this, astronomers had two conjectures about the question of “who is the mother of heavy elements”. In addition to the neutron star “car accident”, the burst of supernovae was also thought to be the cause of the production of heavier elements such as gold. Supernova burst refers to the phenomenon in which the life of a star comes to an end and bursts out the last light and heat.
  According to current astrophysical theories, the energy produced by supernovae can also allow iron to continue to fuse into gold. However, the burst frequency of supernovae is very high. The European Space Agency has reported that the burst frequency of supernovae in the Milky Way is about once every 50 years. If the heavy elements are formed by the energy fusion produced by supernovae, the content of gold in the universe should be Very high. But in fact the content of gold in the universe is very low. Therefore, Bartos believes that it is not the burst of supernova, but the “neutron star car accident” that gave birth to the element of gold.

  In addition to gold, elements such as iodine and zinc, which are necessary for humans and other organisms, also appeared after the “car accident.” It is these elements that gave rise to such colorful life on earth today. From this perspective, the neutron star “car accident” can be regarded as a “cosmic shaper.”
  If the “car accident” of the neutron star is considered to be the shaper of the universe today, then the “car accident” of the black hole may become the end of the universe, and Bartos is also tracking the “car accident” of the black hole.
  Bartos analyzed the data collected by LIGO (Laser Interference Gravitational Wave Observatory) in the United States and Virgo Observatory in Italy. He discovered that in the summer of 2017 alone, four black hole collisions occurred in the universe. As a result, there have been 10 known black hole collisions. After the black holes collide, do they bounce or merge into a “super black hole” that can swallow millions of stars? If a “super black hole” swallows a star, will the matter of the star annihilate or “assemble” into a new object? These questions attracted Bartos.
Physicist in life

  Although he focuses on such huge propositions as astronomy and the universe, and has made some major discoveries at the age of 29, Bartos is not proud of it. He is willing to share what he knows with more people.
  Neil Freudenberg is the author of the science fiction novel “Lost and Longing”, in which she describes the discovery of gravitational waves and the working principle of the LIGO observatory. In order to write this book, she discussed with Bartos for a long time, she said, “Bartos generously gave her a lot of help.”
  As a novelist, Freudenberg’s mathematical foundation is far less solid than Bartos. Before consulting Bartos, she was worried that she would be overwhelmed by long-form mathematical knowledge and basic principles, but Bartos took the initiative to tell She, there are only four simple operations in physics, unless the calculation is wrong, there is no need to discuss mathematical knowledge.
  Not only that, but rather than boring basic principles, Bartos prefers to explain everything he loves with phenomena in life, such as black holes. One day, Freudenberg was talking about black holes with Bartos in the park. He used the trees and squirrels in the park to compare black holes. Just as there are so many and common tree holes in trees, there are also many black holes in the universe. Large or small, far or near. A black hole can swallow all nearby matter, but what is swallowed will not disappear, just change its appearance. For example, in spring, squirrels hide many nuts in tree holes, but in winter, only leftover nut shells are left. And, just like we can judge who ate the nuts by looking at the footprints in the tree hole. If we can find the footprints left by the matter swallowed by the black hole in space and time-gravitational waves, then we can judge who entered the black hole when. Although the forces at work are different, the black hole has so many similarities with the tree hole. The black hole does not seem to be as mysterious as imagined.
  Bartos succeeded in arousing Freudenberg’s interest. She said that if I stopped writing novels, I would study gravitational waves. This is something that Einstein predicted to exist but cannot be detected, but now that scientists have detected it, we know more about black holes.
  In fact, physicists are also ordinary people. Their success may only be better at observing life than others, more focused than others, and thinking more than others.