Since most physicists still believe that cause needs to precede effect, we conclude that no information can be transmitted faster than the speed of light. Relativity teaches us that if two space-time events are separated so that they cannot be connected by any signal travelling at c or less, then different observers will disagree as to which of the two events came first. More importantly, the relativistic notion of simultaneity makes it clear that no information can travel faster than light without throwing all our concepts of cause and effect into disarray. A massive object needs infinite energy to reach c, while massless particles like photons always carry their energy at precisely the speed of light. Apparently, the peak of this pulse is simply not the kind of “thing” to which Einstein’s famous law applies.Īt almost 300 000 km s -1, the cosmic speed limit, c, is one of the most widely known constants in physics. In the latest experiment, a group of researchers at the NEC Research Institute in Princeton, US, observed the peak of a laser pulse leave a small cell filled with caesium gas before it had even entered the cell (L J Wang, A Kuzmich and A Dogariu 2000 Nature 406 277). Nonetheless, experiments over the past 20 years have been forcing us to re-examine what we mean by the word “nothing”. Despite a recent raft of reports in the media, this statement is as true now as it ever was. The observation of a light pulse leaving a gas-filled chamber before it had even arrived sparked a media frenzy, yet the laws of physics have remained intact. Webinars Tune into online presentations that allow expert speakers to explain novel tools and applications.Video Watch our specially filmed videos to get a different slant on the latest science.Podcasts Our regular conversations with inspiring figures from the scientific community. Audio and video Explore the sights and sounds of the scientific world.Supercool physics Experiments that probe the exotic behaviour of matter at ultralow temperatures depend on the latest cryogenics technology.The science and business of space Explore the latest trends and opportunities associated with designing, building, launching and exploiting space-based technologies.Revolutions in computing Find out how scientists are exploiting digital technologies to understand online behaviour and drive research progress.Nanotechnology in action The challenges and opportunities of turning advances in nanotechnology into commercial products.#BlackInPhysics Celebrating Black physicists and revealing a more complete picture of what a physicist looks like.Artificial intelligence Explore the ways in which today’s world relies on AI, and ponder how this technology might shape the world of tomorrow. Collections Explore special collections that bring together our best content on trending topics.Innovation showcases A round-up of the latest innovation from our corporate partners.Projects and facilities Follow the latest progress at the world’s top scientific experiments.Policy and funding Understand how emerging policy changes could affect your work and career.Education and outreach Learn about novel approaches to educating and inspiring the scientists of the future.Business and innovation Find out how recent scientific breakthroughs are driving business innovation and commercial growth.Impact Explore the value of scientific research for industry, the economy and society.Personalities Find out who’s doing what in industry and academia.Interviews Discover the views of leading figures in the scientific community.Opinion and reviews Find out whether you agree with our expert commentators.Careers Consider your career options with valuable advice and insightful case studies.People Meet the people behind the science.Events Plan the meetings and conferences you want to attend with our comprehensive events calendar.Blog Enjoy a more personal take on the key events in and around science.
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