Archiv: gravitational waves


01.07.2023 - 17:20 [ Nature.com ]

Giant gravitational waves: why scientists are so excited

On 29 June, four separate teams of scientists made an announcement1–4 that promises to shake up astrophysics: they had seen strong hints of very long gravitational waves warping the Galaxy.

Gravitational waves are ripples in the fabric of space-time that are generated when large masses accelerate. They were first detected in 2015, but the latest evidence hints at ‘monster’ ripples with wavelengths of 0.3 parsecs (1 light year) or more; the waves detected until now have wavelengths of tens to hundreds of kilometres.

Here Nature reports what these monster gravitational waves could mean for our understanding of the cosmos, and how the field could evolve.

01.07.2023 - 17:05 [ New York Times ]

The Cosmos Is Thrumming With Gravitational Waves, Astronomers Find

(June 28, 2023)

The scientists strongly suspect that these gravitational waves are the collective echo of pairs of supermassive black holes — thousands of them, some as massive as a billion suns, sitting at the hearts of ancient galaxies up to 10 billion light-years away — as they slowly merge and generate ripples in space-time.

“I like to think of it as a choir, or an orchestra,” said Xavier Siemens, a physicist at Oregon State University who is part of the North American Nanohertz Observatory for Gravitational Waves, or NANOGrav, collaboration, which led the effort. Each pair of supermassive black holes is generating a different note, Dr. Siemens said, “and what we’re receiving is the sum of all those signals at once.”

01.07.2023 - 16:50 [ Institute of Physics - IOP.org ]

Searching for the Nano-Hertz Stochastic Gravitational Wave Background with the Chinese Pulsar Timing Array Data Release I

(Published 29 June 2023)

Observing and timing a group of millisecond pulsars with high rotational stability enables the direct detection of gravitational waves (GWs). The GW signals can be identified from the spatial correlations encoded in the times-of-arrival of widely spaced pulsar-pairs. The Chinese Pulsar Timing Array (CPTA) is a collaboration aiming at the direct GW detection with observations carried out using Chinese radio telescopes. This short article serves as a „table of contents“ for a forthcoming series of papers related to the CPTA Data Release 1 (CPTA DR1) which uses observations from the Five-hundred-meter Aperture Spherical radio Telescope. (…)

A Pulsar Timing Array (PTA; Foster & Backer 1990) is an array of pulsars, which are regularly observed. The times-of-arrival (TOAs) are measured for pulses that we see beams of electromagnetic waves emitted by the pulsars sweeping over the Earth. As the directions of the radiation beam and the pulsar rotational axis do not coincide, we observe this radiation as regular pulses synchronized to the pulsar rotation (Gold 1969).

01.07.2023 - 16:38 [ Richard Panek / Washington Post ]

Everything you thought you knew about gravity is wrong

(02.08.2019)

We don’t know what gravity is.

Say that to the average person, and the answer you’ll probably get is some version of: “What are you talking about? Gravity is the force of attraction that makes things fall straight down.” But say it to a physicist, and the answer you’ll get is, “That’s right.”

I know, because those are the two answers I’ve been getting for the past few years, ever since I figured out that nobody knows what gravity is, and that just about nobody knows that nobody knows what gravity is. The exception is physicists: They know that nobody knows what gravity is, because they know that they don’t know what gravity is.

01.07.2023 - 16:32 [ Physics & Astronomy International Journal / medcraveonline.com ]

About the nature of gravitational and gravity waves

(March 20, 2018)

Gravitational waves, which Albert Einstein predicted in 1916.2 were a riddle until 14 September 2015. Gravitational waves are small deformations of the four dimensional space–time geometry. They propagate with the speed of light and they are generated by catastrophic events in the Universe, in which strong gravitational fields and sudden acceleration (or deceleration) of asymmetric distribution of large masses are involved. In the other words, according to the theory of relativity, any accelerating or decelerating massive object that isn’t spherically or cylindrically symmetrical generates detectable gravitational waves. That object could be for example neutron star or black hole binary system. Gravitational waves are also produced by cosmological explosions such as supernova. Gravity is the weakest of the four fundamental forces, it is known for a very long time, but still there is no a good unique gravity force (field) theory.

29.06.2021 - 21:31 [ BBC ]

Rare black hole and neutron star collisions sighted twice in 10 days

When objects as massive as these collide they create ripples in the fabric of space called gravitational waves. And it is these ripples that the researchers have detected.

15.09.2020 - 18:14 [ Richard Panek / Washington Post ]

Everything you thought you knew about gravity is wrong

(02.08.2019)

“What are you talking about? Gravity is the force of attraction that makes things fall straight down.” But say it to a physicist, and the answer you’ll get is, “That’s right.”

I know, because those are the two answers I’ve been getting for the past few years, ever since I figured out that nobody knows what gravity is, and that just about nobody knows that nobody knows what gravity is. The exception is physicists: They know that nobody knows what gravity is, because they know that they don’t know what gravity is.

08.01.2020 - 02:24 [ CNN ]

Astronomers detect gravitational waves created by massive neutron star collision

Neutron stars are the smallest in the universe, the remnants of supernovae. Their diameters are comparable to the size of a city like Chicago or Atlanta, but they are incredibly dense, with masses bigger than that of our sun. So think of the sun, compressed into a major city — and then think of two of them violently crashing into each other.

15.11.2019 - 16:19 [ Richard Panek / Washington Post ]

Everything you thought you knew about gravity is wrong

(02.08.2019)

“What are you talking about? Gravity is the force of attraction that makes things fall straight down.” But say it to a physicist, and the answer you’ll get is, “That’s right.”

I know, because those are the two answers I’ve been getting for the past few years, ever since I figured out that nobody knows what gravity is, and that just about nobody knows that nobody knows what gravity is. The exception is physicists: They know that nobody knows what gravity is, because they know that they don’t know what gravity is.

28.10.2019 - 07:11 [ Heise.de ]

Missing Link: Zweifel trotz Nobelpreis – Streit über Graviationswellen-Messungen

LIGO und Virgo sind die ersten Experimente ihrer Art. Die Kollaboration umfasst mehrere tausend Physiker und damit fast jeden, der heute als Experte zu Graviationswellen durchgeht. Aus diesem Grund kann die LIGO/Virgo-Kollaboration es sich leisten, Kritik einfach zu ignorieren, auf ihre eigenen Analyseverfahren zu vertrauen und die Welt im Unklaren darüber zu lassen, genau wie sie eigentlich was analysiert.

11.08.2019 - 19:48 [ Richard Panek / Washington Post ]

Everything you thought you knew about gravity is wrong

(02.08.2019)

“What are you talking about? Gravity is the force of attraction that makes things fall straight down.” But say it to a physicist, and the answer you’ll get is, “That’s right.”

I know, because those are the two answers I’ve been getting for the past few years, ever since I figured out that nobody knows what gravity is, and that just about nobody knows that nobody knows what gravity is. The exception is physicists: They know that nobody knows what gravity is, because they know that they don’t know what gravity is.

30.05.2019 - 16:24 [ scitecheuropa.eu ]

Solving a century-long mystery: the origin of galactic cosmic rays

(04.04.2019)

The word ‘astronomy’ means the direct observations of extra-terrestrial objects. This definition is relevant to photons, neutrinos, and gravitational waves, i.e. massless, neutral and stable particles. But for cosmic ray electrons, protons, and nuclei, the term ‘astronomy’ is used with a certain reservation. Because of the deflections of electrically charged particles in the chaotic interstellar and intergalactic magnetic fields, the information about their original directions pointing to the sites of their production is lost. Instead, on the Earth, we detect an (almost) isotropic flux of cosmic rays contributed by a huge number of galactic and extragalactic sources.