{"id":532965,"date":"2026-06-13T07:15:13","date_gmt":"2026-06-13T07:15:13","guid":{"rendered":"https:\/\/www.europesays.com\/ie\/532965\/"},"modified":"2026-06-13T07:15:13","modified_gmt":"2026-06-13T07:15:13","slug":"einsteins-lost-theory-said-gravity-changes-speed-of-light-and-a-new-experiment-claims-it-was-right","status":"publish","type":"post","link":"https:\/\/www.europesays.com\/ie\/532965\/","title":{"rendered":"Einstein\u2019s Lost Theory Said Gravity Changes Speed of Light and a New Experiment Claims It Was Right"},"content":{"rendered":"

\"Elevator<\/a>A humble elevator shaft was recently used in a test of the constancy of the speed of light. Credit:\u00a0Jason Wong\/Flickr<\/a>,\u00a0CC BY-NC-ND 2.0<\/a><\/p>\n

Albert Einstein postulated in his 1905 theory of special relativity that the speed of light in a vacuum is constant. Ever since, that\u2019s been one of the fundamental assumptions of physics.<\/p>\n

Now\u00a0Enbang Li<\/a>, a physicist at the University of Wollongong in Australia, has challenged this idea by building a machine he says is capable of detecting changes in the speed of light as it crosses Earth\u2019s surface. The findings suggest that light is, in fact, sped up by gravity, which could have implications for Earth science applications ranging from climate monitoring to mineral resource exploration.<\/p>\n

An Old Conundrum<\/strong><\/p>\n

The idea that light is influenced by gravity is not new. Einstein\u2019s ideas, which were further developed with his theory of general relativity in 1915, predicted massive objects in space would bend light with their gravitational grab. This theory was famously\u00a0proven in 1919<\/a>\u00a0when two independent teams measured starlight passing a solar eclipse at two different points on Earth\u2019s surface and found the results matched Einstein\u2019s predictions.<\/p>\n

This bending of light\u2019s path, according to general relativity, is achieved by a warping of the space-time fabric. Under this scenario, the speed of light remains constant\u2014it just has to travel farther as it navigates the warped space-time around celestial bodies, so to a distant observer, it appears to have been slowed.<\/p>\n

But what if light doesn\u2019t navigate warped space-time and actually is slowed down or sped up by the gravity of large objects?<\/p>\n

Li pointed out that Einstein himself was not always convinced the speed of light was constant. In 1911, he wrote a\u00a0paper<\/a>\u00a0postulating that light speed changed depending on the gravity of objects it passed by. However, \u201cwhen he published his general theory,\u201d said Li, \u201che just abandoned this model.\u201d<\/p>\n

If the movement of light can be affected by gravity, Li reasoned, it might be possible to detect variations in its speed on a local level\u2014such as an elevator shaft in a building on the campus of the University of Wollongong.<\/p>\n

Raising the Big Issues<\/strong><\/p>\n

Gravity on Earth varies locally, depending on altitude, underground density, and topography. Gravity at the top of a tall building, for example, is\u00a0measurably weaker than it is at the bottom<\/a>.<\/p>\n

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With these variations in mind, Li installed an experiment in an elevator. It consisted of a coil of fiber-optic cable that if stretched out in one direction, would be 10 kilometers (6.2 miles) long. Laser beams were fired through the cables and then reflected back, thus traveling 20 kilometers (12.4 miles) before reaching an ultrafast photodetector. An oscilloscope measured the time it took for the beam to travel that distance. The experiment was run at the top of the shaft and at the bottom.<\/p>\n

The biggest challenge, Li said, was filtering out all the surrounding environmental \u201cnoise,\u201d such as changing temperature and humidity, electromagnetic disturbance, and building vibrations. Li designed a temperature control system, and the experiment was sealed in an enclosure with electromagnetic shielding to isolate air flows. Li ran the experiment and\u00a0found<\/a>\u00a0light moved minutely faster at the bottom of the shaft than at the top.<\/p>\n

Gravity Sensing on the Go<\/strong><\/p>\n

Next, Li took his research a step further by building a small, portable machine he claims can detect changes in the speed of light as it nears more gravitationally dense objects.<\/p>\n

In this second experiment, Li positioned a moveable 72-kilogram (159-pound) weight near the machine. Light, he found, moved faster when the weight was near the machine than when it was farther away.<\/p>\n

The results, which were published in\u00a0Scientific Reports<\/a>, are consistent with the variable speed of light model Einstein proposed in 1911, although Li\u2019s preliminary results are much larger than that model predicts.<\/p>\n

If proven, the findings would present a fundamental challenge to our understanding of both general and special relativity.<\/p>\n

In the world of Earth sciences, they could lead to greatly improved gravity-sensing technologies. Because of their sensitivity to changes in mass, gravity sensors are used to\u00a0map the seafloor<\/a>\u00a0and to locate underground mineral reserves. Gravity sensing can also improve our\u00a0understanding of Earth\u2019s climate<\/a>\u00a0as variations in the gravity field can be linked to factors like changes in ice mass and shifts in groundwater.<\/p>\n

Currently, gravimeters are vulnerable to vibrations and movement, whereas Li\u2019s machine, which has no moving parts, could even be used on board a plane or submarine.<\/p>\n

\u201cA Striking Claim\u201d<\/strong><\/p>\n

Chris Stevens<\/a>, a numerical relativist with the University of Canterbury in New Zealand, called the work \u201cintriguing and ambitious.\u201d While Stevens, who was not involved in the research, said that Li\u2019s work is \u201cwell founded,\u201d he noted that any observable effects of gravity on light on Earth would be \u201cextraordinarily small\u201d and therefore these results must be treated with caution.<\/p>\n

\u201cIn my own research on observable gravitational phenomena,\u201d he explained, \u201cI usually require a few black holes colliding somewhere in the universe. Separating genuine gravitational signatures from environmental and instrumental noise will therefore be exceptionally demanding.\u201d<\/p>\n

Stevens said the implications of Li\u2019s research, if validated, would be far-reaching. \u201cThe work is exciting because it pushes precision photonic measurement techniques into a regime where relativistic effects may become practically useful for geophysics and sensing applications.\u201d<\/p>\n

John Norton<\/a>, an historian of physics at the University of Pittsburgh who was also not involved in the research, called the findings a \u201cstriking claim.\u201d He was, however, skeptical of them, saying \u201cif there is a coupling between light and gravity of magnitude greater than general relativity predicts, it is hard to see how the 1919 eclipse test and later studies of\u00a0gravitational lensing<\/a>\u00a0would not have found it.\u201d<\/p>\n

Li acknowledged there is a long way to go before his device finds everyday use. Disentangling the intricacies of space and time, he said, is a vast challenge. \u201cIn physics, people still say gravity is a mystery. Light is another mystery. So if you put these two mysteries together, that\u2019s going to be a giant mystery.\u201d<\/p>\n

This article originally appeared in Eos Magazine<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"A humble elevator shaft was recently used in a test of the constancy of the speed of light.…\n","protected":false},"author":2,"featured_media":532966,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_share_on_mastodon":"0"},"categories":[271],"tags":[14589,18,19,17,53830,452,133],"class_list":["post-532965","post","type-post","status-publish","format-standard","has-post-thumbnail","category-physics","tag-einstein","tag-eire","tag-ie","tag-ireland","tag-minerals","tag-physics","tag-science"],"share_on_mastodon":{"url":"https:\/\/pubeurope.com\/@ie\/116741572885438869","error":""},"_links":{"self":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts\/532965","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/comments?post=532965"}],"version-history":[{"count":0,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts\/532965\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/media\/532966"}],"wp:attachment":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/media?parent=532965"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/categories?post=532965"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/tags?post=532965"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}