For example, normal stars sitting on their own emit lots of light, from jiggling electrons in their hot atmospheres, but almost no gravitational radiation. That means that gravitational waves have much lower frequencies than light, and come from totally different kinds of happenings in the universe. Gravitational waves are emitted when big masses accelerate light is emitted when tiny electrical charges accelerate. When we can hear them, those vibrations will let us listen to huge and often invisible cataclysms throughout the observable universe. The fastest accelerations of the densest objects, with the strongest gravity, presumed to be black holes (which are themselves nothing but dense knots of spacetime curvature), create the loudest vibrations. The vibrations stretch the fabric of space itself back and forth in a way that can be detected far away. Albert Einstein's general theory of relativity tells us that all forms of matter create warps in spacetime and that motions of matter create vibrations that travel throughout space at the speed of light. In contrast to the swift-traveling vibrations in electrical and magnetic fields that we call light, the sounds of the universe are carried by vibrations in spacetime called gravitational waves. (To be fair, we should not forget here other messengers from afar-cosmic rays, neutrinos, cosmic dust, meteorites and other matter falling to Earth from outer space-and most of all, we should not forget the cosmic origin of all the atoms which make up Earth and ourselves! But those are other stories.) As James Clerk Maxwell showed in the 19th century, light is another name for vibrations in electrical and magnetic fields that travel through space-at the speed of light. That's one reason why our immediate knowledge of the universe far away from the solar system, from prescientific astronomy up to now, comes almost entirely from studying one form of energy: light. Space is a near-perfect vacuum, and ordinary sound carries only where there is matter to vibrate. The sounds of the cosmos are not the familiar sounds our ears sense, carried by vibrations in air. The universe is a musical that we've been watching all this time as a silent movie. It's just that we haven't heard those sounds yet. Space and time carry a cacophony of vibrations with textures and timbres as rich and varied as the din of sounds in a tropical rain forest or the finale of a Wagner opera. Happily, astronomers are finding ways to do that-to feel as well as see the active universe around us.Įinstein's theory of spacetime tells us that the real universe is not silent, but is actually alive with vibrating energy. Hearing the universe is more like touching than looking. It is one thing to see flashes of lightning in the distance, quite another to be shaken by the sound of rolling thunder. So how would you feel if suddenly, as you quietly admired a dark and starry sky, you heard the stars making all kinds of crazy noises?Īfter the initial shock of being jolted out of your poetic reverie, I think you would find that the universe felt much more immediate, present, real and alive. Finally, compared to 3D convolutional networks, our model is faster to train, it can achieve dramatically higher test efficiency (at a small drop in accuracy), and it can also be applied to much longer video clips (over one minute long). Despite the radically new design, TimeSformer achieves state-of-the-art results on several action recognition benchmarks, including the best reported accuracy on Kinetics-400 and Kinetics-600. Our experimental study compares different self-attention schemes and suggests that "divided attention," where temporal attention and spatial attention are separately applied within each block, leads to the best video classification accuracy among the design choices considered. Our method, named "TimeSformer," adapts the standard Transformer architecture to video by enabling spatiotemporal feature learning directly from a sequence of frame-level patches. We present a convolution-free approach to video classification built exclusively on self-attention over space and time.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |