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[td][/td] [td]== Structure of cosmic expansion ==[/td]
[td]== Structure of cosmic expansion ==[/td] [td]Distant galaxies in all directions are observed to move away from Earth and their velocity is proportional to their distance from Earth. This observation, known as [[Hubble's law]], combined with the observation that the universe at the largest scales is [[Homogeneity (physics)|homogeneous]] (the same everywhere) and [[isotropic]] (the same in all directions), means that the universe is expanding uniformly at the present time. Uniform expansion is equivalent to the observed linear relationship between the the recession velocities <math>\vec v</math> of a galaxy and its positions <math>\vec x</math>:[/td]
[td]Distant galaxies in all directions are observed to move away from Earth and their velocity is proportional to their distance from Earth. This observation, known as [[Hubble's law]], combined with the observation that the universe at the largest scales is [[Homogeneity (physics)|homogeneous]] (the same everywhere) and [[isotropic]] (the same in all directions), means that the universe is expanding uniformly at the present time. Uniform expansion is equivalent to the observed linear relationship between the recession velocities <math>\vec v</math> of a galaxy and its positions <math>\vec x</math>:[/td] [td]: <math>\vec v = H_0 \vec x,</math>[/td]
[td]: <math>\vec v = H_0 \vec x,</math>[/td] [td]where the Hubble constant <math>H_0</math> quantifies the rate of expansion today.<ref name=Longair-2023>{{Cite book |last=Longair |first=Malcolm S. |url=https://link.springer.com/book/10.1007/978-3-662-65891-8 |title=Galaxy Formation |date=2023 |language=en |doi=10.1007/978-3-662-65891-8 |issn=0941-7834}}</ref>{{rp|52}}[/td]
[td]where the Hubble constant <math>H_0</math> quantifies the rate of expansion today.<ref name=Longair-2023>{{Cite book |last=Longair |first=Malcolm S. |url=https://link.springer.com/book/10.1007/978-3-662-65891-8 |title=Galaxy Formation |date=2023 |language=en |doi=10.1007/978-3-662-65891-8 |issn=0941-7834}}</ref>{{rp|52}}[/td]
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[td][/td]Revision as of 11:24, 31 August 2025
[/td][td][/td] [td]== Structure of cosmic expansion ==[/td]
[td]== Structure of cosmic expansion ==[/td] [td]Distant galaxies in all directions are observed to move away from Earth and their velocity is proportional to their distance from Earth. This observation, known as [[Hubble's law]], combined with the observation that the universe at the largest scales is [[Homogeneity (physics)|homogeneous]] (the same everywhere) and [[isotropic]] (the same in all directions), means that the universe is expanding uniformly at the present time. Uniform expansion is equivalent to the observed linear relationship between the the recession velocities <math>\vec v</math> of a galaxy and its positions <math>\vec x</math>:[/td]
[td]Distant galaxies in all directions are observed to move away from Earth and their velocity is proportional to their distance from Earth. This observation, known as [[Hubble's law]], combined with the observation that the universe at the largest scales is [[Homogeneity (physics)|homogeneous]] (the same everywhere) and [[isotropic]] (the same in all directions), means that the universe is expanding uniformly at the present time. Uniform expansion is equivalent to the observed linear relationship between the recession velocities <math>\vec v</math> of a galaxy and its positions <math>\vec x</math>:[/td] [td]: <math>\vec v = H_0 \vec x,</math>[/td]
[td]: <math>\vec v = H_0 \vec x,</math>[/td] [td]where the Hubble constant <math>H_0</math> quantifies the rate of expansion today.<ref name=Longair-2023>{{Cite book |last=Longair |first=Malcolm S. |url=https://link.springer.com/book/10.1007/978-3-662-65891-8 |title=Galaxy Formation |date=2023 |language=en |doi=10.1007/978-3-662-65891-8 |issn=0941-7834}}</ref>{{rp|52}}[/td]
[td]where the Hubble constant <math>H_0</math> quantifies the rate of expansion today.<ref name=Longair-2023>{{Cite book |last=Longair |first=Malcolm S. |url=https://link.springer.com/book/10.1007/978-3-662-65891-8 |title=Galaxy Formation |date=2023 |language=en |doi=10.1007/978-3-662-65891-8 |issn=0941-7834}}</ref>{{rp|52}}[/td]
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