Archiv: rotations / gravity (space objects)


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.

11.08.2019 - 21:47 [ Harvard.edu ]

Centennial cycles of the solar activity and Earth rotation

(Oktober 2011)

The centennial variations of the Universal Time UT1 and Length of Day LOD are investigated by means of long historical observational series of UT1 and LOD variations, which cover time span more than 3 centuries long. The correlation between the centennial cycles of the Earth rotation, climate and Total Solar Irradiance TSI is determined using the time series of North America temperature (2.2Ka) and precipitation (8Ka), Mean Sea Level MSL variations at Stockholm tide gauge station since 1774 and reconstructed TSI variations since 843. The model of the solar influences on the centennial and decadal cycles of the Earth rotation is based on a main centennial cycle and harmonics, ending by oscillation with period around 9a.

11.08.2019 - 21:38 [ Nils-Axel Mörner / suanet.ac.tz ]

Solar Wind, Earth’s Rotation and Changes in Terrestrial Climate

(08.03.2013)

Another effect of the interaction between the Solar Wind and the Earth’s magnetic field seems to be that it affects the Earth’s rate of rotation where Solar Minima lead to accelerations and Solar Maxima to decelerations (as discussed in previous papers; [2,5-10]). Several authors have noted a correlation between sunspot activity and Earth’s rotation [2,8-23] or Solar-planetary cycles and Earth’s rotation [10,24-32].

Golovkov [13] plotted Earth’s rate of rotation (spin rate) against sunspot numbers and found that high spin rates correlated with low sunspot numbers and low spin rates with high sunspot numbers. Mörner [2] plotted LOD against sunspot numbers for the period 1831–1995 and found a linear relationship where low LOD values (high spin rate) correlated with low sunspot numbers and high LOD values with high sunspot numbers. Consequently, the Earth’s rotation accelerates at low solar activity and decelerates at high solar activity.

The relations among solar activity, Solar Wind, variations in Earth’s atmospheric shielding capacity and variations in the Earth’s rate of rotation are expressed in Fig. 1

11.08.2019 - 21:32 [ Nils-Axel Mörner / core.ac.uk ]

Solar Wind, Earth’s Rotation and Changes in Terrestrial Climate

(2013)

Solar variability affects Earth climate. It is proposed that this forcing primarily goes via the interaction of the Solar Wind with the Earth’s magnetosphere, rather than via changes in irradiance, which is generally assumed. The cyclic variations in Solar Wind emission generate corresponding changes in the Earth’s rate of rotation (LOD), as recorded by correlations between sunspot numbers and LOD-variations. Variations in Earth’s rotation affect not only the atmospheric circulation but also the ocean circulation.

11.08.2019 - 21:00 [ ScienceNews.org ]

Every six years, Earth spins slightly faster and then slower

(10.07.2013)

The world turns slightly faster and slower on a regular 5.9-year cycle, a new study suggests. Researchers also found small speed changes that happen at the same time as sudden alterations in Earth’s magnetic field.

11.08.2019 - 20:46 [ Phys.org ]

Research pair find 5.9 year cycle of oscillations in length of day

(11.07.2013)

Unlike the ten year trend (believed to be caused by changes in the Earth’s core) and the episodic jerks (scientists have detected 10 such events since 1969) the 5.9 year cycle was unexpected. Every 5.9 years, they claim, the planet undergoes a period of several months where the length of each day is longer or shorter than „normal.“ The researchers don’t know what causes the cycle but suspect it has something to do with the core-mantle boundary.

Scientists are also interested in learning more about the episodic jerks that alter day-length for several months at a time—this new research has revealed that during each event, the Earth’s geomagnetic field undergoes a similar effect. Scientists don’t know why either occurs, but suspect they are connected.

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.

11.08.2019 - 19:02 [ arxiv.org ]

Anomalous post-newtonian terms and the secular increase of the astronomical unit

(14.10.2018)

In 2004 Krasinsky and Brumberg indicated that the analysis of all available radiometric measurements of distances between the Earth and the planets, and also the observations of martian landers and orbiters, showed that the Astronomical Unit is increasing at a rate 15 ± 4 meters per century [14]. Later on, a more careful analysis by Standish has shown that the secular rate is closer to 7 ± 2 meters per century [26]. Anyway, this is by far too large to be explained by the loss of solar mass due to solar wind and electromagnetic radiation. An explanation based upon tidal friction caused by the bulge produced by Earth gravity on the Sun has been proposed [17]. However, this model has not been validated and the detailed mechanism for this tidal friction is hypothetical. A secular effect on the eccentricity of planetary motions have been also unveiled by the recent detailed analysis of the Lunar orbit. The secular increase of the eccentricity is very small but, however, is clearly within the range of precision of Lunar laser ranging. This kind of unexplained observations,
after discarding any possible conventional explanation, could give rise to an arena where the status of General Relativity as a complete theory of gravity (at least, at the macroscopic level) could be tested.

In this paper we have assumed that a conventional explanation is not possible and that an extra force term is necessary in order to incorporate this behaviour in the post-newtonian formalism.

11.08.2019 - 18:45 [ 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.

11.08.2019 - 17:11 [ 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.

11.08.2019 - 17:08 [ 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.

11.08.2019 - 16:51 [ NewScientist.com ]

Why is the Earth moving away from the sun?

(01.06.2009)

It’s not much – just 15 cm per year – but since that’s 100 times greater than the measurement error, something must really be pushing Earth outward. But what?

One idea is that the Sun is losing enough mass, via fusion and the solar wind, to gradually be losing its gravitational grip (see Astronomical unit may need to be redefined). Other possible explanations include a change in the gravitational constant G, the effects of cosmic expansion, and even the influence of dark matter. None have proved satisfactory.

11.08.2019 - 15:25 [ 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.