A New Test Of General Relativity

February 24, 2018
One of the great unsolved problems in modern physics is the nature of gravity. Since Einstein first published the general theory of relativity over a century ago, it has proven to be a very accurate model of the solar system and the cosmos. Repeated experiments have confirmed its predictions in the form of planetary orbits, gravitational lensing, and high precision measurements of time and frequency on the Earth and in orbit. So far no deviations from the predictions of general relativity have ever been detected.

However scientists have also been limited in the systems that they can study. Precise gravitational measurements can be made on the surface of the Earth or in orbit around the Earth, but our planet is rather small and boring. And while we can study the effects of gravitational lensing by observing distant galaxies, these effects are still caused by gravitational effects over long distances. We have not yet been able to measure the effects of general relativity in high energy, high density systems in which extreme gravitational fields are present. It is possible that general relativity will break down in these regions, and in fact we know from theoretical work in the theory of quantum gravity that general relativity cannot describe all objects in our Universe. At some point the theory will need to be replaced by something better, just as general relativity itself replaced Newtonian gravity.

And this coming Spring, a cosmic coincidence could provide one of the most powerful tests of the general theory of relativity. 

At the center of our own Milky Way galaxy, there exists a supermassive black hole. It is so massive that all of the stars and planets in our galaxy rotate around it, just as the planets in our solar system rotate around the Sun. And the gravitational field at its surface is so strong, that it may not obey the usual laws of general relativity. 

Near the center of the Milky Way there is also a dense collection of stars known as the S-stars. They are young, active stars whose formation and existence in such a hostile environment remains a mystery to astrophysicists. One of these stars, S0-2, is on course to pass very close to the supermassive black hole in the next few months, and when it does it will provide an excellent opportunity for astronomers to test the general theory of relativity.

Astronomers have carefully measured the precise wavelengths of light being emitted by this star, and will continue to do so through the rest of the year. According the general theory of relativity, these wavelengths will be redshifted, or stretched out by the warping of space near the event horizon of the black hole. By measuring the wavelength of the light that we receive in terrestrial telescopes, scientists will be able to compare the effects of the black hole's gravity on the star to the predictions of general relativity. And if they differ by any significant amount, it would indicate the first experimental evidence of a new, modified form of gravity - and perhaps even start to provide data on the nature of quantum gravity.

If the astronomers are able to find such deviations from the accepted models of gravity, then they expect to follow it up with further measurements of other stars near the galactic core and collect more data. If not, then it will tell us that general relativity is a valid theory even in extreme environments such as this one.

Either way it will be an important test of the general theory of relativity, and should result in some amazing new data that will be studied for years to come!

Surreal Numbers

February 23, 2018
I am always amazed at how simple some of the most interesting ideas and research in modern mathematics truly is. There are problems in mathematics that can be explained to a small child and yet the greatest minds of the past centuries have been unable to solve. Mathematics is one of the few fields of study where anyone can understand topics that the leading experts are still trying to solve. One such topic is the surreal numbers.

Everyone remembers as a child learning the integers, or counting...
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Energy Localization

February 10, 2018
After the memorial I posted earlier in the week, I have had a few readers ask me for more details about energy localization in the general theory of relativity. There are a few variations on this theory, and so I will try to focus on generic properties and as usual I will try to minimize formal equations in order to make this article accessible to a general audience.

The general theory of relativity was first published in 1915, and quickly confirmed by astrophysics experiments over the followi...
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In Memorium

February 7, 2018
There is some sad news to report this month, with the passing in January of one of my friends and mentors, Dr. Fred Cooperstock. Not only was he an accomplished physicists making significant contributions to the study of the general theory of relativity, but he was also a much loved and respected instructor to generations of physics students at the University of Victoria.

As a theoretical physicist he was best known for the Cooperstock Energy Localization Hypothesis, which argued that gravitat...
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Happy New Year!!

January 1, 2018
May you all have a happy and healthy 2018, full of enjoyment and prosperity. And may we all still be together again when the year ends and 2019 begins.

Happy New Year!!
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2017 Year In Review

December 31, 2017
Here we are at the end of another amazing year - it seems like just yesterday we were celebrating the start of 2017 and now it has come to an end. And though it was not the greatest year for the world at large, it has been a very good year for the scientific community.

The year started off with some very preliminary results being announced. The theoretical physics community saw a few hints of evidence of a holographic Universe in experimental data - though that is still quite controversial - w...
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Merry Christmas!

December 25, 2017

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A Christmas Visitor?

December 16, 2017
The astronomy community has been buzzing this week with discussions of a new object that has been seen in the solar system.  Its formal name is A2017UI (with the proposed common name Oumuamua, which is Hawaiian for "messenger from the distant past" ), and it is assumed to be an asteroid - but one such as we have never seen before. 

First off, it has entered the solar system from deep space, making it the first such asteroid in recent history to do so. Being extra-solar already makes it a valua...
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The Trouble With Strings

November 21, 2017
Let me begin by saying that I believe that the popularization of science in general and physics in particular is a very good thing. The more educated a society becomes, the more it is able to function and advance. And in the internet age in which false information is able to spread so rapidly, it is more important than ever for trained, professional scientists such as myself to promote skepticism and rational thought, and to try to communicate what is accepted scientific fact from superstitio...
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Angry Aliens?

November 17, 2017
Since mankind first looked up at the night sky, one of the biggest questions has been "Are we alone in the Universe?". Philosophers and theologians have debated this issue for centuries, while astronomers and astrobiologists continue to look for evidence and explore the data. When NASA sent probes to the edge of our solar system and beyond, they included information on our location in the galaxy and our culture in case other life forms one day discover them. Projects such as SETI have spent d...
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About Me

Dr. Chris Bird I am a theoretical physicist & mathematician, with training in electronics, programming, robotics, and a number of other related fields.


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