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Gravitational echoes may be caused by the collision of two black holes, and may indicate that these objects have completely new physical properties. This conclusion was made by RUDN physicists after a series of mathematical calculations. The scientists state that if the existence of the echo phenomenon is confirmed, astrophysicists would have to reconsider their view of compact space objects. The results of the study were published in Physical Review D.

According to the theory of general relativity (GR), any massive object distorts space-time. A similar effect is observed when a heavy metal ball is placed on stretched elastic fabric. The heavier is the ball, the deeper is the depression in the fabric. Similarly, the higher the mass of an object, the more it distorts space-time. Black holes are among the heaviest objects in the universe, and therefore distort space-time the most. When two black holes collide, gravitational waves spread out from the site of collision. They can be compared to rings on the water, or sound waves, but there is one important peculiar feature. Gravitational waves do not propagate spatially—they are themselves the oscillations of space-time.

Gravitational waves from the collision of two black holes decay with time, but on their final stage, they can cause the so-called echo—additional wave scattering. It can be compared to regular acoustic echo. The existence of such gravitational echo has not been confirmed yet, and there are different opinions about its possible source. A RUDN physicist, together with colleagues from the Czech Republic and Russia, assumed that if the existence of gravitational echo is experimentally confirmed, it would be the beginning of the new physics adding to GR.

Continue reading “Gravitational echo phenomenon will become a key to the new physics, physicist says” »

Researchers hoping to better interpret data from the detection of gravitational waves generated by the collision of binary black holes are turning to the public for help.

West Virginia University assistant professor Zachariah Etienne is leading what will soon become a global volunteer computing effort. The public will be invited to lend their own computers to help the scientific community unlock the secrets contained in gravitational waves observed when black holes smash together.

LIGO’s first detection of gravitational waves from colliding black holes in 2015 opened a new window on the universe, enabling scientists to observe cosmic events spanning billions of years and to better understand the makeup of the Universe. For many scientists, the discovery also fueled expansion of efforts to more thoroughly test the theories that help explain how the universe works—with a particular focus on inferring as much information as possible about the black holes prior to their collision.

Continue reading “DIY gravitational waves with ‘BlackHoles@Home’” »

Scientists believe that time is continuous, not discrete—roughly speaking, they believe that it does not progress in “chunks,” but rather “flows,” smoothly and continuously. So they often model the dynamics of physical systems as continuous-time “Markov processes,” named after mathematician Andrey Markov. Indeed, scientists have used these processes to investigate a range of real-world processes from folding proteins, to evolving ecosystems, to shifting financial markets, with astonishing success.

However, invariably a scientist can only observe the state of a system at discrete times, separated by some gap, rather than continually. For example, a stock market analyst might repeatedly observe how the state of the market at the beginning of one day is related to the state of the market at the beginning of the next day, building up a conditional probability distribution of what the state of the second day is given the state at the first day.

In a pair of papers, one appearing in this week’s Nature Communications and one appearing recently in the New Journal of Physics, physicists at the Santa Fe Institute and MIT have shown that in order for such two–time dynamics over a set of “visible states” to arise from a continuous-time Markov process, that Markov process must actually unfold over a larger space, one that includes hidden states in addition to the visible ones. They further prove that the evolution between such a pair of times must proceed in a finite number of “hidden timesteps”, subdividing the interval between those two times. (Strictly speaking, this proof holds whenever that evolution from the earlier time to the later time is noise-free—see paper for technical details.)

Continue reading “The discrete-time physics hiding inside our continuous-time world” »

A Harvard physicist has shown that wormholes can exist: tunnels in curved space-time, connecting two distant places, through which travel is possible.

But don’t pack your bags for a trip to other side of the galaxy yet; although it’s theoretically possible, it’s not useful for humans to travel through, said the author of the study, Daniel Jafferis, from Harvard University, written in collaboration with Ping Gao, also from Harvard and Aron Wall from Stanford University.

“It takes longer to get through these wormholes than to go directly, so they are not very useful for space travel,” Jafferis said. He will present his findings at the 2019 American Physical Society April Meeting in Denver.

One of the ultimate goals of modern physics is to unlock the power of superconductivity, where electricity flows with zero resistance at room temperature.

Progress has been slow, but in 2018, physicists have made an unexpected breakthrough. They discovered a superconductor that works in a way no one’s ever seen before — and it opens the door to a whole world of possibilities not considered until now.

In other words, they identified a brand new type of superconductivity.

Continue reading “Physicists Have Found an Entirely New Type of Superconductivity” »

Professor Brian Cox explains the process that causes all stars, including eventually our own sun, to die.

Stars are only able to survive as long as they have a supply of hydrogen to burn.

Our star, the Sun, will run out of fuel in about a billion years.

Continue reading “Physics KS3 / GCSE: Death of the Sun and stars” »

We already recover power from the wheels of some cars when slowing. Kinetic energy recovery systems (KERS) have been used in Formula One racing to store energy in a flywheel when braking, and then push it back to the wheels later for a boost in speed. Electric cars often use regenerative braking, which converts the speed of the wheels into electrical power to recharge the battery. These systems are a great way to increase efficiency, but like everything in the Universe, they are not 100 per cent efficient. Sadly, the laws of physics prohibit the existence of true perpetual motion, so it’s the best we can do.

One week after LIGO switched back on, it has already detected the gravitational waves from another pair of merging black holes, marking the beginning of a new era of gravitational wave astronomy.

Today our middle-aged Universe looks eerily smooth. Too smooth, in fact.

While a rapid growth spurt in space-time would explain what we see, science needs more than nice ideas. It needs evidence that whittles away contending arguments. We might finally know where to look for some.

A team of physicists from the Centre for Astrophysics | Harvard & Smithsonian (CfA) and Harvard University went back to the drawing board on the early Universe’s evolution to give us a way to help those inflation models stand out from the crowd.

Continue reading “What Existed Before The Big Bang? Astronomers Have Found a Test to Narrow It Down” »