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14 Cards in this Set
- Front
- Back
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Astronomical Unit (AU) |
The mean distance from the centre of the Earth to the centre of the Sun |
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Light year (Ly) |
The distance travelled by light in a vacuum in one year. |
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Parsec (pc) |
The distance at which a radius of one AU subtends an angle of one arcsecond |
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Arc minute |
1° = 60 arcminutes |
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Arc second |
1 arc minute = 60 arc seconds so 1°= 1/3600 arc seconds |
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Stellar parallex |
A technique used to determine the distance to stars that are less than 100pc away from the earth, by comparing their apparent positions against 'stationary' stars 6 months apart. |
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Doppler Effect |
The change in frequency and wavelength of waves from an object moving relative to an observer compared with what would be observed without relative motion |
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Blue-Shift |
The shortening of observed wavelengths that occurs when a wave source is moving towards the observer as the absorption lines is moved towards the blue end of the spectrum |
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Red-shift |
The lengthening of observed wavelengths that occurs when a wave source is moving towards the observer as the absorption lines is moved towards the red end of the spectrum |
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Hubble's Law |
v ∝ d The recessional speed (v) of a galaxy is almost directly proportional to its distance (d) from the Earth |
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Expanding Universe |
The idea that the fabric of space and time is expanding in all directions, and the further two points are, the faster their relative motion away from each other is |
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Cosmological Principle |
The assumption that when viewed on a large enough scale, the universe is homogeneous and isotropic |
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Homogeneous |
The uniform distribution of matter across the universe when viewed on a sufficiently large scale, with the laws of physics being universal |
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Isotropic |
Appearing the same in all directions to an observer, regardless of position |
