Or, to put it another way, mass and energy are interchangeable. Einstein wrote down an equation that relates the two. All rights reserved. Share Tweet Email. Why it's so hard to treat pain in infants. This wild African cat has adapted to life in a big city. Animals Wild Cities This wild African cat has adapted to life in a big city Caracals have learned to hunt around the urban edges of Cape Town, though the predator faces many threats, such as getting hit by cars.
India bets its energy future on solar—in ways both small and big. Environment Planet Possible India bets its energy future on solar—in ways both small and big Grassroots efforts are bringing solar panels to rural villages without electricity, while massive solar arrays are being built across the country.
Go Further. Animals Climate change is shrinking many Amazonian birds. Animals Wild Cities This wild African cat has adapted to life in a big city. Animals This frog mysteriously re-evolved a full set of teeth. Animals Wild Cities Wild parakeets have taken a liking to London. Animals Wild Cities Morocco has 3 million stray dogs. Meet the people trying to help. Environment COP26 nears conclusion with mixed signals and frustration.
Environment Planet Possible India bets its energy future on solar—in ways both small and big. Environment As the EU targets emissions cuts, this country has a coal problem. Paid Content How Hong Kong protects its sea sanctuaries. History Magazine These 3,year-old giants watched over the cemeteries of Sardinia. Science Coronavirus Coverage What families can do now that kids are getting the vaccine. Magazine How one image captures 21 hours of a volcanic eruption.
Reports of cosmic speed breakers, such as faster-than-light neutrinos announced in , have always turned out to be wrong. This has odd consequences. From the perspective of one, what speed is the other approaching at? Moving clocks tick slower and moving rulers appear shorter, so there is no one objective measure of time and space — and you really will age less in a speeding spacecraft.
At our normal speeds, these warping effects are negligible, but close to light speed they become hugely significant, and ensure no object can ever cover a given space in a shorter time than light can.
Mass is just a concentrated form of energy, connected by the constant speed of light. By then he was a professor in Berlin and had been inducted into the Prussian Academy of Sciences. Even so, he had time on his hands. His estranged wife, Mileva Maric, finally accepted that her life with Einstein was over, and had moved back to Zurich with their two sons.
Though the increasingly strained family relations weighed heavily on Einstein, the arrangement also allowed him to freely follow his mathematical hunches, undisturbed day and night, in the quiet solitude of his barren Berlin apartment. By November, this freedom bore fruit. Einstein corrected his earlier error and set out on the final climb toward the general theory of relativity.
But as he worked intensely on the fine mathematical details, conditions turned unexpectedly treacherous. A few months earlier, Einstein had met with the renowned German mathematician David Hilbert, and had shared all his thinking about his new gravitational theory. Hilbert considered it fair game to pursue an opening in a promising but as yet unfinished theory of gravity; Einstein considered it atrociously bad form for Hilbert to muscle in on his solo expedition so near the summit.
His years of hard work notwithstanding, Einstein might get scooped. The worry was well-founded. A week later, on November 25, lecturing to a hushed audience at the Prussian Academy, Einstein unveiled the final equations constituting the general theory of relativity.
No one knows what happened during that final week. In the end, Hilbert did the right thing. He acknowledged that whatever his role in catalyzing the final equations might have been, the general theory of relativity should rightly be credited to Einstein. And so it has. Hilbert has gotten his due too, as a technical but particularly useful way of expressing the equations of general relativity bears the names of both men.
Of course, the credit would only be worth having if the general theory of relativity were confirmed through observations. Remarkably, Einstein could see how that might be done. General relativity predicted that beams of light emitted by distant stars would travel along curved trajectories as they passed through the warped region near the Sun en route to Earth. Einstein used the new equations to make this precise—he calculated the mathematical shape of these curved trajectories. Battling the challenges of weather, each team took a series of photographic plates of distant stars momentarily visible as the Moon drifted across the Sun.
During the subsequent months of careful analysis of the images, Einstein waited patiently for the results. Finally, on September 22, , Einstein received a telegram announcing that the eclipse observations had confirmed his prediction. Indeed, in the decades since the eclipse measurements, there have been a great many other observations and experiments—some ongoing—that have led to rock-solid confidence in general relativity. General relativity claims that as a body like the Earth spins on its axis, it should drag space around in a swirl somewhat like a spinning pebble in a bucket of molasses.
It took a generation of scientific effort to develop the necessary gyroscopic technology and then years of data analysis to, among other things, overcome an unfortunate wobble the gyroscopes acquired in space. There is one remaining experiment, currently more than 20 years in the making, that many consider the final test of the general theory of relativity. According to the theory, two colliding objects, be they stars or black holes, will create waves in the fabric of space, much as two colliding boats on an otherwise calm lake will create waves of water.
0コメント