Archiv: Gravitation / Rotation (Weltraumobjekte) / gravity / rotation (space objects)


26.04.2024 - 00:00 [ Journal of Geophysical Research: Solid Earth / onlinelibrary.wiley.com ]

Possible Eoarchean Records of the Geomagnetic Field Preserved in the Isua Supracrustal Belt, Southern West Greenland

(24 April 2024)

The preservation of a temperate climate and liquid water on early Earth depends critically upon the strength of the magnetosphere (Sterenborg et al., 2011; Tarduno et al., 2014). Recent atmospheric escape models have suggested that both weak (<10 μT) and strong (>1 mT) magnetic fields could substantially enhance atmospheric escape under present-day solar wind conditions via the polar wind or cusp escape, respectively (Gronoff et al., 2020; Gunell et al., 2018; Lundin et al., 2007). During the Archean, the Sun was rotating faster, generating a stronger stellar dynamo and therefore the solar wind was more intense than today (Vidotto, 2021). An increased solar wind strength causes greater interaction with the upper atmosphere and greater escape of ions assuming a constant level of protection from Earth‘s magnetosphere. Previous magnetohydrodynamic simulations have suggested that if Earth‘s magnetic field was half its present day strength 3.5 Ga ago, the area of the polar cap (the area containing open dipolar magnetic field lines, allowing atmospheric escape via the polar wind) could increase by up to 50% (Sterenborg et al., 2011).

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.

04.10.2021 - 07:04 [ National Astronomical Observatory of Japan / SciTechdaily.com ]

Interplay Between Magnetic Force and Gravity in Massive Star Formation

(September 26, 2021)

The magnetic field is part of one of the four fundamental forces in nature. It plays a vital role in everyday life, from producing electricity in hydroelectric power plants to diagnosing diseases in medicine. Historically, the Earth’s magnetic field served as a compass for travelers before modern technology was available. Crucially for life, the Earth’s magnetic field acts as a shield protecting us from charged particles emanating from the Sun, which are accelerated by the Sun’s magnetic field. Removing this shield would very likely extinguish life on Earth.

10.08.2021 - 13:29 [ American Geophysical Union / Science Daily ]

Ancient shell shows days were half-hour shorter 70 million years ago

(March 9, 2020)

The length of a year has been constant over Earth‘s history, because Earth‘s orbit around the Sun does not change.

10.08.2021 - 13:08 [ International Earth Rotation and Reference Systems Service - iers.org ]

Measuring the irregularities of the Earth‘s rotation

The variability of the earth-rotation vector relative to the body of the planet or in inertial space is caused by the gravitational torque exerted by the Moon, Sun and planets, displacements of matter in different parts of the planet and other excitation mechanisms.

10.08.2021 - 12:48 [ National Aeronautics and Space Administration ]

NASA Team Studies Middle-aged Sun by Tracking Motion of Mercury

(18.01.2018)

Like the waistband of a couch potato in midlife, the orbits of planets in our solar system are expanding. It happens because the Sun’s gravitational grip gradually weakens as our star ages and loses mass.

10.08.2021 - 12:44 [ Forbes ]

Earth Is Drifting Away From The Sun, And So Are All The Planets

(Jan 3, 2019)

Deep inside the Sun, the process of nuclear fusion occurs. Every second, the Sun emits some 3.846 × 1026 joules of energy, which are released via the conversion of mass into energy in the core. Einstein‘s E = mc2 is the root cause, nuclear fusion is the process, and the continuous emission of energy from the Sun is the result. This energy is the underlying process that powers practically every biologically interesting process occurring on Earth.

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.

15.09.2020 - 18:00 [ CNN ]

In Earth‘s early history, a day was 23.5 hours and a year lasted 372 days

(13.03.2020)

We‘ve long known that an Earth day lasts 24 hours, and that remains constant because Earth‘s trip around the sun doesn‘t vary.

However, the number of days that make an Earth year have shifted and shortened because days have grown longer. That is thanks to the moon‘s gravity, which draws on ocean‘s tides and slows Earth‘s rate of rotation.

15.09.2020 - 18:00 [ Frankfurter Allgemeine Zeitung ]

Eine Schaltsekunde mehr Zeit

(30.12.2008)

Wie unregelmäßig sich die Erde dreht, sieht man daran, dass zwischen 1999 und 2006 sieben Jahre vergehen mussten, bis eine Schaltsekunde nötig wurde; diesmal sind es nur drei Jahre.

15.09.2020 - 16:58 [ Newsweek ]

NASA Shows Einstein Was Right: Our Sun Is Losing Mass – and Its Grip on Our Solar System

(19.01.2018)

As our sun gets older, it‘s losing mass, and so its gravitational pull becomes weaker. As a result, the orbits of all the planets in our solar system are expanding, not unlike „the waistband of a couch potato in midlife,“ according to a new NASA press statement.

A team of researchers from the Massachusetts Institute of Technology, the University of Maryland and the NASA Goddard Space Flight Center has shown that the aging sun is behaving according to Albert Einstein‘s theory of general relativity.

15.09.2020 - 16:53 [ National Aeronautics and Space Administration ]

NASA Team Studies Middle-aged Sun by Tracking Motion of Mercury

(18.01.2018)

Like the waistband of a couch potato in midlife, the orbits of planets in our solar system are expanding. It happens because the Sun’s gravitational grip gradually weakens as our star ages and loses mass.

15.09.2020 - 16:49 [ Sparkonit.com ]

The Orbits Of All The Planets In Our Solar System Are Expanding As The Sun Gets Older, Study On Mercury’s Orbit Reveals

(25.01.2018)

“Mercury is the perfect test object for these experiments because it is so sensitive to the gravitational effect and activity of the Sun,” explained Antonio Genova, the lead author of the study and a MIT researcher working at NASA’s Goddard Space Flight Center.

Researchers were able to make these calculations from the data gathered by NASA’s MESSENGER spacecraft which made three ‘flybys’ of Mercury in 2008 and 2009 and orbited Mercury between March 2011 and April 2015 before it crashed into Mercury in 2015, Mail noted.

15.09.2020 - 16:30 [ University of North Carolina at Charlotte ]

Solar Rotation Effects on The Thermospheres of Mars and Earth

(spring 2006)

The first thing that must be understood in this paper is the chain of events that is being tracked. From the Sun‘s rotational quirks, to their effects on CO2 in the respective atmospheres of Mars and Earth. There is also a comparison to older, normalized data from Venus.

(…)

Interestingly, once the data was compiled, there was no correlation found between the levels of CO2 found in the upper atmosphere (~150km on Earth, where this transformation takes place.) Broadening their search, the authors found a strong correlation between the ratio of CO2/O2 and the thermal changes. They feel this suggests that the thermal diffusion effect relies on some form of resonance between the two molecules involved

15.09.2020 - 16:17 [ Harvard.edu ]

Equatorial solar rotation and its relation to climatic changes

(29. September 1977)

During the years from 1965 to 1976, the magnitude of the solar rotation speed averaged annually showed a good inverse correlation with the annual relative sunspot numbers. It is suggested that this variation of the equatorial solar rotation speed may be responsible for the earth‘s present unusual climatic conditions. A similarity concerning the low sunspot activity for 1976 and the year 1643, just before the beginning of the Maunder Minimum (1645-1715) with its very severe climatic conditions, is pointed out. It appears, therefore, likely that the present unusual climatic conditions will remain as long as the solar activity continues to decrease.

15.09.2020 - 15:14 [ US National Science Foundation ]

Researchers find link between Atlantic hurricanes and weather system in East Asia

(11.08.2020)

In the new study, the U.S. National Science Foundation-funded researchers say that a stronger East Asian Subtropical Jet Stream (EASJ) is associated with fewer Atlantic tropical cyclones.

The EASJ is an upper-level river of wind that originates in East Asia and moves west to east across the globe. It carries with it an atmospheric phenomenon called a Rossby wave.

Rossby waves occur naturally in the Earth‘s oceans and atmosphere, forming because of the planet‘s rotation

14.05.2020 - 20:45 [ inverse.com ]

The Sun‘s midlife crisis could be making it stand out in the universe

(30.04.2020)

„The solar dynamo is one of the last unsolved mysteries of solar physics,“ Reinhold says. „We don’t really know why it’s 11 years long, or how it is generated.“

Other stars also run on cycles, but theirs varies from three years to eight years.

Although the researchers aren‘t quite sure what makes the Sun so unique, they have a few possible explanations.

14.05.2020 - 20:37 [ Forbes ]

Is Our Sun In A 9,000 Year ‘Feeble Phase?’ Similar Stars Are Five Times More Fickle, Find Scientists

(30.04.2020)

The Sun takes 24.5 days to rotate once around their own axis; the 369 chosen all rotate once every 20-30 days.

“The speed at which a star rotates around its own axis is a crucial variable,” said Prof. Dr. Sami Solanki, director at MPS and co-author of the new paper. “The magnetic field is the driving force responsible for all fluctuations in activity.”

13.03.2020 - 08:57 [ National Aeronautics and Space Administration ]

NASA Team Studies Middle-aged Sun by Tracking Motion of Mercury

(18.01.2018)

Like the waistband of a couch potato in midlife, the orbits of planets in our solar system are expanding. It happens because the Sun’s gravitational grip gradually weakens as our star ages and loses mass.

13.03.2020 - 08:53 [ Newsweek ]

NASA Shows Einstein Was Right: Our Sun Is Losing Mass—and Its Grip on Our Solar System

(19.01.2018)

As our sun gets older, it’s losing mass, and so its gravitational pull becomes weaker. As a result, the orbits of all the planets in our solar system are expanding, not unlike „the waistband of a couch potato in midlife,“ according to a new NASA press statement.

A team of researchers from the Massachusetts Institute of Technology, the University of Maryland and the NASA Goddard Space Flight Center has shown that the aging sun is behaving according to Albert Einstein’s theory of general relativity.

13.03.2020 - 08:41 [ CNN ]

In Earth‘s early history, a day was 23.5 hours and a year lasted 372 days

(today)

We‘ve long known that an Earth day lasts 24 hours, and that remains constant because Earth‘s trip around the sun doesn‘t vary.

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.

02.01.2020 - 16:52 [ Harvard.edu ]

Equatorial solar rotation and its relation to climatic changes

(29. September 1977)

During the years from 1965 to 1976, the magnitude of the solar rotation speed averaged annually showed a good inverse correlation with the annual relative sunspot numbers. It is suggested that this variation of the equatorial solar rotation speed may be responsible for the earth‘s present unusual climatic conditions. A similarity concerning the low sunspot activity for 1976 and the year 1643, just before the beginning of the Maunder Minimum (1645-1715) with its very severe climatic conditions, is pointed out. It appears, therefore, likely that the present unusual climatic conditions will remain as long as the solar activity continues to decrease.

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.

15.11.2019 - 15:49 [ European Southern Observatory (ESO) / Youtube ]

Zooming into Sagittarius A*

(07.11.2018)

ESO’s exquisitely sensitive GRAVITY instrument has added further evidence to the long-standing assumption that a supermassive black hole lurks in the centre of the Milky Way. New observations show clumps of gas swirling around at about 30% of the speed of light on a circular orbit just outside a four million solar mass black hole — the first time material has been observed orbiting close to the point of no return, and the most detailed observations yet of material orbiting this close to a black hole.

15.11.2019 - 15:31 [ Carnegie Science / Youtube ]

Hypervelocity star

(12.11.2019)

The artist impression of the ejection mechanism by the supermassive black hole. Credit: James Josephides (Swinburne Astronomy Productions)

15.11.2019 - 15:21 [ Carnegie Science ]

Runaway star was ejected from the “heart of darkness”

“My favorite part of this discovery is thinking about where this star came from and where it‘s going,” said Ji. “It was born in one of the craziest places in the universe, near a supermassive black hole with lots of other nearby star friends; but it‘s going to leave our galaxy and die all alone, out in the middle of nowhere. Quite a fall from grace.”

15.11.2019 - 15:06 [ CBS News ]

Supermassive black hole throws star out of Milky Way galaxy at speed of 3.7 million mph

Five million years ago, when humanity‘s ancestors were just learning to walk upright, a star was ejected from Sagittarius A*, the supermassive black hole at the center of the Milky Way Galaxy, at a staggering 3.7 million mph. This month, a group of researchers spotted the superfast star traveling relatively close to Earth.

16.10.2019 - 23:23 [ Newsweek.com ]

NASA Engineer Proposes ‚Helical Engine‘ For Interstellar Travel With No Propellant

Burns said his helical engine would work by accelerating ions confined in a loop. By changing their mass slightly, the engine would then move the ions back and forth along the direction of travel to produce thrust. New Scientist notes that the helical engine would need to be 650 feet long and 40 feet wide in order to work.

16.10.2019 - 23:20 [ Nasa.gov ]

Helical Engine

• What and Why
•Thought Experiment
•Ions and Particle Accelerators
•Classical vs Relativistic Dynamics
•Helical Engine Architecture
•A Specific Design Example
•Conservation of Momentum
•Conclusions

16.10.2019 - 23:14 [ NewScientist.com ]

NASA engineer‘s ‚helical engine‘ may violate the laws of physics

This mass changing isn’t prohibited by physics. Einstein’s theory of special relativity says that objects gain mass as they are driven towards the speed of light, an effect that must be accounted for in particle accelerators. In fact, a simplistic implementation of Burns’s concept would be to replace the ring with a circular particle accelerator, in which ions are swiftly accelerated to relativistic speed during one stroke, and decelerated during the other.

But Burns thinks it would make more sense to ditch the box and rod and employ the particle accelerator for the lateral as well as the circular movement – in which case, the accelerator would need to be shaped like a helix.

11.08.2019 - 22:20 [ arxiv.org ]

A Relationship between the Solar Rotation and Activity Analysed by Tracing Sunspot Groups

(10.11.2017)

Main result of our investigation is the finding that the Sun rotates more differentially at the minimum than at the maximum of activity during the 1977 – 2016 epoch. This is in agreement with theoretical predictions of reduced differential rotation in the presence of strong magnetic fields. Inverse correlation between equatorial rotation and solar activity was found by many authors before and is corroborated here regardless of the recent revision of sunspot number. The secular decrease of rotation velocity accompanying the increase of activity stopped in the last part of the 20th century when solar activity started to decrease. It was noted that when the significant peak of equatorial rotation velocity is observed during minimum of activity the strength of next maximum is smaller then the previous one. It was suggested that this finding might be connected to a decrease of the magnetic energy of the Sun.

11.08.2019 - 22:09 [ Phys.org ]

Researchers report possible solution to a long-standing solar mystery

(13.12.2016)

The team used several years of data from the Helioseismic and Magnetic Imager on NASA‘s Solar Dynamics Observatory satellite to measure a sharp down-turn in the sun‘s rotation rate in its very outer 150km. Kuhn said, „This is a gentle torque that is slowing it down, but over the sun‘s 5 billion year lifetime it has had a very noticeable influence on its outer 35,000km.“ Their paper describes how this photon-braking effect should be at work in most stars.

This change in rotation at the sun‘s surface affects the large-scale solar magnetic field and researchers are now trying to understand how the solar magnetism that extends out into the corona and finally into the Earth‘s environment will be affected by this braking.

11.08.2019 - 22:08 [ ScienceAlert.com ]

The Sun Is Slowing Down, And Scientists Think They Finally Know Why

(16.12.2016)

To figure out what was going on, the team looked at 3.5 years of data from NASA‘s Solar Dynamics Observatory satellite, which has been observing the Sun since 2010.

Their data was taken from the Helioseismic and Magnetic Imager, which looks at solar oscillations in the Sun‘s magnetic field.

They noticed that there had been a sharp slow-down in the Sun‘s rotation rate in its very outer 150 km layer, which they predict is due to something called the photon-braking effect.

11.08.2019 - 21:54 [ Observatoire de Paris ]

Centennial cycles of the solar activity and Earth rotation

(Oktober 2011)

The irregular and long-term variations of the Earth rotation are mainly caused by the displacements
of matter in different parts of the planet which excitation mechanism is the influence of the Sun and
solar activity cycles. The solar cycles can drive great number of geodynamical processes connected with the convections of the Earth fluids on the surface and inside the Earth. Many of climate and weather parameters are affected directly by the variations of the solar activity.