Einstein’s Theory of Gravity Passes an Extreme Test

Albert Einstein's theory of gravity, postulated more than a century ago as the General Theory of Relativity, is here to stay and remains to this date "a reasonable way to understand the universe", states Discover Magazine.

The theory explains that gravity is an outcome of space-time's inherent flexibility, which means huge objects distort the cosmic fabric, that creates a sort of well, around which other bodies orbit. Just like all other scientific theories, this theory also has some testable predictions, the most essential of which is the "equivalence principle".

So, for example, a hammer and a feather dropped from the same height in a vacuum will hit the ground at the same time; astronaut Dave Scott famously demonstrated this on the Moon in 1971. Whether or not this applied to massive objects like planets and stars has always been debated, but now astronomers have used the Arecibo Observatory to show that the phenomenon does hold true, meaning Einstein was right yet again. Over time, the researchers found nearly no detectable difference, indicating there is little room for alternative theories of gravity in this model.

Today's news, which appears in the journal Nature, concerns the equivalence principal, which roughly says that falling objects should all fall the same way.

An global team of astronomers tested this question by studying three stars orbiting each other about 4,200 light years from Earth.

Now, nearly 80 years later, a study led by researchers from the University of Amsterdam in the Netherlands have proven that even extremely massive objects, such as superdense neutron stars, fall just like a feather.

What they found is that something is making the pulsar move. And because pulsars spin, they can direct their poles toward Earth at regular intervals.

Theresa May says Cabinet supports her Brexit plan after Chequers summit
Mrs May said the Cabinet "has agreed our collective position for the future of our negotiations wit the EU". She said the common rulebook would mean "British businesses will continue to be a rule-taker from the EU".

Test subject PSR J0337+1715 (try saying that five times fast) is a triple star system, with one neutron star in a 1.6-day orbit with a white dwarf, both of which are in a 327-day orbit with another, more distant white dwarf.

The pulsar and the inner white dwarf are in a 1.6-day orbit. Only this time, instead of a hammer and feather, they used a pulsar and a white dwarf. An worldwide research team led by the Anton Pannekoek Institute of Astronomy at the University of Amsterdam, in the Netherlands, has shown that the equivalence principle, which holds that all bodies in the same gravitational field are equally accelerated, is correct.

Movements of pulsars are tracked by researchers by keeping an eye on its radio-wave emissions.

The Westerbork Synthesis Radio Telescope in the Netherlands was one of three telescopes used to study the three-star system, along with the Green Bank Telescope in West Virginia and the Arecibo Observatory in Puerto Rico. "We can tell its location to within a few hundred meters. That is a really precise track of where the neutron star has been and where it is going", Dr Archibald says.

If alternatives to Einstein's theory of gravity were correct, the neutron star fell differently from the white dwarf and the pulses would arrive at a different time than expected. However, no such deformation was detected by the researchers.

"If there is a difference, it is no more than three parts in a million", said Nina Gusinskaia from the University of Amsterdam in the Netherlands. The extreme nature of the observed system has resulted in an even narrower range of theory possibilities than ever before. "Also, we have improved on the accuracy of the best previous test of gravity, both within the solar system and with other pulsars, by a factor of about 10".

Researchers were wondering whether the same principles can apply to larger scales of the Universe, like a whole galaxy, and now they have the answer: it does!

Recommended News

We are pleased to provide this opportunity to share information, experiences and observations about what's in the news.
Some of the comments may be reprinted elsewhere in the site or in the newspaper.
Thank you for taking the time to offer your thoughts.