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100 years of General Relativity

Updated Tuesday, 13th October 2015

2015 marks the 100th anniversary of Albert Einstein's Theory of General Relativity. Find out what it's all about and why it still matters.

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A  bronze statue of Albert Einstein holding a notebook with written equations about relativity, sculpted by Robert Berks. He is sat looking slightly to the right and there are trees with lush green leaves in the background. Creative commons image Icon Wally Gobetz [CC BY-NC-ND 2.0] via Flickr Creative Commons under Creative-Commons license

It's been 100 years since Albert Einstein first presented his complete Theory of General Relativity to the Prussian Academy in 1915. Einstein's field equations still hold up over a century later and represent our best understanding of the wider universe, including black holes, neutron stars, dark matter and the fundamental nature of gravity.

When you think of Einstein, you might think of E=mc2 - the relationship between energy and mass which underpinned his Theory of Special Relativity, published earlier in 1905. The Theory of General Relativity expanded upon this with the famous metaphor of a bowling ball creating a dent in a rubber sheet - demonstrating how matter can warp spacetime creating dynamic gravitational forces and bending the path of light as it travels through the universe.

But why is century-old science still relevant today? For a start, it hasn't yet been disproved - observational evidence from many different experiments continue to back up the science, from peculiarities in Mercury's orbit to spacetime curvature measurements from NASA's Gravity Probe B. The LIGO team at CalTech hope to definitively prove Einstein's theory with experiments made possible by their new Laser Interferometer Gravitational-Wave Observatory. Technology we use, from detecting far off galaxies through gravitational lensing to the GPS on our satnavs and phones, demonstrate practical applications of relativity way beyond anything Einstein could ever have imagined back in 1915.

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What is relativity?

Read more about the 100th anniversary of Einstein's theories at

60 second adventures in astronomy


The International Year of Light celebrates lots of different light-related scientific anniversaries and discoveries throughout 2015 - including Einstein's Theory of General Relativity. Find out more about these milestones in understanding by watching this video or visiting the International Year of Light hub on OpenLearn.


International Year of Light


Celebrating six scientists who changed the world, and our understanding of light.

In the 11th Century, Arab scientist, Ibn Al-Haytham, was told to work out how to regulate the erratic flooding of the River Nile. He soon realised it was utterly impossible and, fearing execution, he pretended to be insane.

He was placed under house arrest: bad news for Al-Haytham, good news for civilisation. He suddenly had a lot of free time to continue his studies. Eventually he wrote The Book of Optics, which showed how vision takes place when light enters the eye.

Al-Haytham had furthered our understanding of light’s nature and 800 years later AugustinJean Fresnel, while discovering the wave nature of light, would create something truly illuminating, with his aptly named, Fresnel lens.

The Fresnel lens can project light for miles around; and soon became the big thing in keeping-ships-off-rocks.

And Fresnel’s ground breaking studies into wave theory have seen him become just as popular with scientists as sea captains.

A slow learner, who couldn’t read at aged 8, he is now considered the Father of the wave theory of light. Despite Fresnel had laid the foundations...

The nature of light remained a mystery until James Clerk Maxwell discovered the deep connection between electricity and magnetism.

In discovering electromagnetic force he proved that light is in fact an electromagnetic wave.

Maxwell was the first scientist to unify any of nature’s fundamental forces and a great influence on our next hero, Albert Einstein, whose theory of General Relativity gave us (Epic Voice) ‘One ring to rule them all’.

With General Relativity Einstein theorised the phenomenon known as gravitational lensing. It explains why distant galaxies sometimes appear shaped like a ring wrapped around a closer galaxy.

During gravitational lensing, a heavy object bends the space around it making a lens. This can magnify the light of a distant galaxy, presenting it as a ring around the closer one.

Einstein had taken our understanding of light far into outer space and soon Arno Penzias and Robert Wilson would detect the earliest hum of the cosmos using a...

Microwave (Clears throat)..... using microwaves!

Yes by detecting the very same light that warms many a bachelor’s lonely heart, Arno Penzias and Robert Wilson discovered the echo of the big bang.

At first they thought the strange radio signal was caused by pigeon poo in their antenna. But with the poo removed ... the signal remained. They won a Nobel Prize for their work, an accolade they share with our last hero of light, Charles Kao.

Back in the 60s, most engineers thought glass was an inefficient medium for carrying Telecommunications.

But Charles Kao (and George Alfred Hockham) believed it could be better than copper. He found that by purifying glass and bundling it into fibres, it could carry huge amounts of information over long distances using light.

And thanks to Kao, we can now communicate from one side of the world to the other in an instant.

All these scientists have made history in the field of light and in 2015 we’re celebrating the anniversaries of their discoveries as part of the International Year of Light.


We don’t have enough information for many important decisions in our lives.

In these cases, we act from a position of relative ignorance. What to believe, or who to trust is becomes a subjective and social decision.

In exploring why people might give credence to ideas which may seem inexplicable, my colleague Amanda van Eck Duymaer van Twist and I have identified several important strategies:

1) Trust in experts: We might look towards external certifications, peer review, or life experience in trying to seek the testimony of those who know more than we do about a subject.

2) Trust in peer groups: Friends or colleagues’ opinions about ‘who to trust’ can be very influential. Sometimes offering contrary opinions or promoting alternative authorities can lead to ostracization from social networks.

3) Trust in personal experience: We each have our past experiences which moderate our judgement of experts and peer groups. But sometimes we all use ‘gut instincts’ or ‘intuition’ as an important deciding factor in who or what to trust.


By thinking about sources for trust and asking critical questions about the effects of beliefs and practices, we can start to more judiciously evaluate beliefs and their associated actions.

For example, we can ask:

  • Do these beliefs provide hope and meaning to those who hold them?
  • What are the actions people take in response to specific beliefs?
  • To what extent do these beliefs and associated activities serve to enrich and help the lives of those who hold them? 
  • Do associated actions or activities cause harm?
  • Are harmful practices or experiences being reinterpreted, rationalised or explained away?

By asking these kinds of questions, it also becomes easier to raise specific objections to beliefs and practices which might cause harm. While other beliefs and practices, even if they cannot be proved ‘true’ – can be very useful and even beneficial for their adherents.

Even if we remain relatively ignorant about things - like what happens after death, we can still evaluate the application of these beliefs and associated practices in people’s lives.


For Further Information

For more information about research on South Asian beliefs in immortality and practices relating to life-extension see

van Eck Duymaer van Twist, A. and Newcombe, S. (2018) ‘“Trust Me, You Can't Trust Them”: Stigmatised Knowledge in Cults and Conspiracies,’ in Asbjørn Dyrendal, David Robertson and Egil Asprem (eds.) Brill Handbook of Conspiracy Theory and Contemporary Religion. Brill: 152-179.

Newcombe, S. (2017) ‘Yogis, Ayurveda and Kayakalpa– The Rejuvenation of Pandit Malaviya’ History of Science in South Asia 5(2): 85–120. DOI: 10.18732/hssa.v5i2.29


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