Describing a force as a curved space series#
Through a series of thought experiments, Einstein demonstrated that the consequences of special relativity are often counterintuitive - even startling. Starting from these two postulates, Einstein showed that space and time are intertwined in ways that scientists had never previously realized.
No matter how fast an observer is moving or how fast a light-emitting object is moving, a measurement of the speed of light always yields the same result. Second, light travels at an unvarying speed of 186,000 miles a second.Einstein recognized that if the motion is perfectly uniform, it's literally impossible to tell - and identified this as a central principle of physics. It’s a bit like when you look out a train window and see an adjacent train appear to move - but is it moving, or are you? It can be hard to tell. As long as an object is moving in a straight line at a constant speed (that is, with no acceleration), the laws of physics are the same for everyone. First, the natural world allows no “privileged” frames of reference.For example, GRACE monitors changes in sea level and can detect changes in Earth’s crust brought on by earthquakes. These changes have revealed important details about our planet. GRACE detects tiny changes in gravity over time. Image credit: NASA/University of Texas Center for Space Research Areas in blue have slightly weaker gravity and areas in red have slightly stronger gravity. The GRACE mission helps scientists to create maps of gravity variations on Earth. These spacecraft are part of the Gravity Recovery and Climate Experiment (GRACE) mission. NASA uses two spacecraft to measure these variations in Earth’s gravity. Gravity is slightly stronger over places with more mass underground than over places with less mass. However, gravity isn’t the same everywhere on Earth. Gravity is what holds our world together. It holds down our atmosphere and the air we need to breathe. The sun's gravity keeps Earth in orbit around it, keeping us at a comfortable distance to enjoy the sun's light and warmth. Watch this video to find out more about these areas of immense gravity! You can't see the change with your eyes, but scientists can measure it.īlack holes pack so much mass into such a small volume that their gravity is strong enough to keep anything, even light, from escaping. If you shine a flashlight upwards, the light will grow imperceptibly redder as gravity pulls it. Albert Einstein discovered this principle. Gravity not only pulls on mass but also on light. Gravity creates stars and planets by pulling together the material from which they are made. The gravitational pull of the moon pulls the seas towards it, causing the ocean tides. Gravity is what holds the planets in orbit around the sun and what keeps the moon in orbit around Earth. But because Earth is so much more massive than you, your force doesn’t really have an effect on our planet. You exert the same gravitational force on Earth that it does on you. And if you were on a planet with less mass than Earth, you would weigh less than you do here. All its mass makes a combined gravitational pull on all the mass in your body. So, the closer objects are to each other, the stronger their gravitational pull is.Įarth's gravity comes from all its mass. Objects with more mass have more gravity. Image credit: NASAĪnything that has mass also has gravity. If another object is nearby, it is pulled into the curve. Albert Einstein described gravity as a curve in space that wraps around an object-such as a star or a planet. Earth's gravity is what keeps you on the ground and what makes things fall.Īn animation of gravity at work. Why do you land on the ground when you jump up instead of floating off into space? Why do things fall down when you throw them or drop them? The answer is gravity: an invisible force that pulls objects toward each other. The force of gravity keeps all of the planets in orbit around the sun. Gravity is the force by which a planet or other body draws objects toward its center.
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