5 Forces That Keep the Universe Together
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on the surface of the vessel “as a free particle.” The idea, for example, of planets
going around the sun due to gravitational force, means in Einstein’s language
that, the space around the sun is curved, and the planets are simply following a
line path in that curved space. In physics language, the line is called a geodesic.
The metric of a space has ten components i.e. ten parts to it. They all depend
on each other in an intricate way and affect the motion of particles.
The gravitational force is so weak that only if you are standing next to
an extremely massive body like the Earth, you can feel it, but if you are
standing next to another person or another 100 persons, even though there is
gravitational force on you, it is too weak for you to feel. The space around one
or 100 persons is not very curved. Every massive object, and in fact any object
that has energy, regardless of whether it has mass, will feel the gravitational
force with a universal strength. That is how sun is pulling the planets to go
around it. Light beams which contain energy but no mass get attracted towards
massive heavenly bodies, such as the sun and the stars, as they pass by them on
their way from distant stars. That leads to the bending of light, first predicted
by Einstein and later observed by Sir Arthur S. Eddington, during a 6 min
total solar ellipse in May 29, 1919, confirming the general theory of relativity
by Einstein. This observation made Einstein a celebrity overnight. A headline
in New York Times read—Lights All Askew in the Heavens—referring to the
bending of light.
Another major confirmation of Einstein theory came recently with the discovery of gravity waves by LIGO (Laser Interferometer Gravity Observatory)
experiment from distant black hole mergers. In fact, there have been more than
ten gravity wave signals from black hole mergers starting with the first one in
2015, and one from a binary neutron star merger in 2017. As of this writing,
in addition to the detections of gravity wave signals published, there may be
others in the process of publication.
More gravity wave signals are likely to be detected once several more
detectors which are being planned are set up. There already exists the VIRGO
gravity wave detector, located outside Pisa, Italy, funded by the Italian and
French governments. This has already observed the binary neutron star
merger gravity wave. There is the planned LIGO-India, a joint US–India
collaboration. There are also plans to set up gravity wave detectors in space,
the LISA project, which is a joint NASA and European Space Agency project.
These discoveries have launched the new field of gravitational wave astronomy,
studying the structure of the universe using not only light but a separate messenger, the gravity wave, which travels un-impeded for much farther distances
than light. They could probe the structure of the universe even better than
what can be learned using neutrinos. The gravity waves have already revealed
significant new facts about the universe, such as the neutron star merger.
35
on the surface of the vessel “as a free particle.” The idea, for example, of planets
going around the sun due to gravitational force, means in Einstein’s language
that, the space around the sun is curved, and the planets are simply following a
line path in that curved space. In physics language, the line is called a geodesic.
The metric of a space has ten components i.e. ten parts to it. They all depend
on each other in an intricate way and affect the motion of particles.
The gravitational force is so weak that only if you are standing next to
an extremely massive body like the Earth, you can feel it, but if you are
standing next to another person or another 100 persons, even though there is
gravitational force on you, it is too weak for you to feel. The space around one
or 100 persons is not very curved. Every massive object, and in fact any object
that has energy, regardless of whether it has mass, will feel the gravitational
force with a universal strength. That is how sun is pulling the planets to go
around it. Light beams which contain energy but no mass get attracted towards
massive heavenly bodies, such as the sun and the stars, as they pass by them on
their way from distant stars. That leads to the bending of light, first predicted
by Einstein and later observed by Sir Arthur S. Eddington, during a 6 min
total solar ellipse in May 29, 1919, confirming the general theory of relativity
by Einstein. This observation made Einstein a celebrity overnight. A headline
in New York Times read—Lights All Askew in the Heavens—referring to the
bending of light.
Another major confirmation of Einstein theory came recently with the discovery of gravity waves by LIGO (Laser Interferometer Gravity Observatory)
experiment from distant black hole mergers. In fact, there have been more than
ten gravity wave signals from black hole mergers starting with the first one in
2015, and one from a binary neutron star merger in 2017. As of this writing,
in addition to the detections of gravity wave signals published, there may be
others in the process of publication.
More gravity wave signals are likely to be detected once several more
detectors which are being planned are set up. There already exists the VIRGO
gravity wave detector, located outside Pisa, Italy, funded by the Italian and
French governments. This has already observed the binary neutron star
merger gravity wave. There is the planned LIGO-India, a joint US–India
collaboration. There are also plans to set up gravity wave detectors in space,
the LISA project, which is a joint NASA and European Space Agency project.
These discoveries have launched the new field of gravitational wave astronomy,
studying the structure of the universe using not only light but a separate messenger, the gravity wave, which travels un-impeded for much farther distances
than light. They could probe the structure of the universe even better than
what can be learned using neutrinos. The gravity waves have already revealed
significant new facts about the universe, such as the neutron star merger.