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Definition
the combination of time and the three dimensions of space.
--> the theorized 4th dimension |
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Term
| According to general relativity, why does Earth orbit the Sun? |
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Definition
| Earth is following the straightest path possible, but spacetime is curved in such a way that this path goes around the Sun. |
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| According to general relativity, how is time affected by gravity? |
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Definition
| Time runs slower in stronger gravitational fields. |
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| How do we know what happens at the event horizon of a black hole? |
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Definition
| We don't know for sure: we only know what to expect based on the predictions of general relativity |
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| Gravitational lensing occurs because |
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Definition
| gravity curves space and light always follows the straightest possible path through space. |
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| What evidence supports the theory that there is a black hole at the center of our galaxy? |
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Definition
| The motions of the gas and stars at the center indicate that it contains a million solar masses within a region only about 1 parsec across |
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Term
| According to general relativity, what is gravity? |
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Definition
| the bending of space time around massive objects |
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Term
| What did Einstein have to say about Newton's theory of gravity?` |
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Definition
| he proposed that Newton's theory was just an approximation to a more general theory of gravitation, and that this general theory of gravitation could not only predict motions as Newton's had but could also predict the bending of light and very small corrections needed to agree with all the observations |
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Term
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Definition
an object so massive that the curvature of space time becomes infinite
no light or energy can escape it |
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Term
| what is the only evidence we have of black holes existing? |
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Definition
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Term
| What is the surface of a black hole? |
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Definition
the radius at which the path of light has been bent inwards so that no light can escape
also known as the event horizon |
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Term
| what is the radius of the event horizon called? |
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Definition
the Schwarzschild radius
R=2GM/c^2 |
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| what does the special theory of relativity say? |
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Definition
| that the passage of time slows down both for objects moving very fast, and for objects moving nearby very massive objects (this is also known as time dilation) |
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| Time dilation due to speed |
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Definition
| relative to a stationary observer, time slows down the faster an object moves |
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Term
| Time dilation due to gravity |
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Definition
| time slows down for objects within a strong gravitational field relative to those in a weak gravitational field |
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Term
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Definition
Muons decay at a regular predictable rate in our atmosphere as they come in from space
We can measure how many muons are detected at high elevation and by knowing how quickly they decay, predict how many we should observe at a lower elevation
We measure considerably more muons at sea level than we should
␣ By moving very near the speed of light, the muon lifetime has actually been extended from our perspective, so that they take longer to decay than they would have if they were stationary
From the ␣␣␣␣␣␣ perspective, it is able to travel further in its lifetime because the distance it is travelling has been shortened (aka length contraction) |
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