User John Hobson

8 votes

6 answers

2k views

Is there cosmological redshift within the Milky Way?

asked Jul 23, 2021 at 9:19

2 votes

1 answer

226 views

Can we have positively curved space within negatively curved spacetime?

asked Apr 10, 2021 at 11:51

2 votes

1 answer

143 views

How do you relate $\Omega_{k}$, the curvature term in the FLRW metric, to the radius of curvature?

asked Jul 17, 2023 at 10:56

2 votes

3 answers

120 views

What is the radius of a black hole? [duplicate]

asked Jul 30, 2023 at 16:13

1 vote

1 answer

86 views

Is there gravitational time dilation as we look further out into space (and therefore further back in time)?

asked Jan 22, 2023 at 12:05

1 vote

2 answers

75 views

Why does $n = -3(1+ \omega)$? [closed]

asked Dec 16, 2022 at 11:33

1 vote

1 answer

56 views

Is there a Doppler effect on the surface of an expanding balloon?

asked Nov 18, 2023 at 13:19

1 vote

1 answer

192 views

Why are physicists not more concerned that there are too many explanations for redshift in the universe?

asked Mar 26 at 19:58

0 votes

0 answers

38 views

Is there a formula for gravitational time dilation at the cosmological scale?

asked Dec 5, 2023 at 0:53

0 votes

2 answers

112 views

If a photon is absorbed, does the associated wave function disappear instantaneously, or at the speed of light?

asked Oct 5, 2023 at 15:11

-1 votes

1 answer

68 views

How accurate are astronomical observations around black holes? Can they distinguish between the following two scenarios?

asked Dec 19, 2022 at 12:18

-1 votes

2 answers

97 views

If every cubic metre of space contained roughly 10^41 photons, each with a wavelength of 88 billion light years, would it be possible to detect them

asked Feb 19 at 17:06

-3 votes

3 answers

128 views

Is the Doppler effect for light symmetric?

asked Mar 29 at 17:26

-3 votes

1 answer

178 views

Must spacetime be homogeneous?

asked Aug 9, 2021 at 15:21

-4 votes

2 answers

102 views

Are black holes 4-dimensional balls of spacetime? If so, will they have 3-sphere surfaces?

asked Dec 1, 2023 at 0:24

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15 Questions

Is there cosmological redshift within the Milky Way?

Can we have positively curved space within negatively curved spacetime?

How do you relate $\Omega_{k}$, the curvature term in the FLRW metric, to the radius of curvature?

What is the radius of a black hole? [duplicate]

Is there gravitational time dilation as we look further out into space (and therefore further back in time)?

Why does $n = -3(1+ \omega)$? [closed]

Is there a Doppler effect on the surface of an expanding balloon?

Why are physicists not more concerned that there are too many explanations for redshift in the universe?

Is there a formula for gravitational time dilation at the cosmological scale?

If a photon is absorbed, does the associated wave function disappear instantaneously, or at the speed of light?

How accurate are astronomical observations around black holes? Can they distinguish between the following two scenarios?

If every cubic metre of space contained roughly 10^41 photons, each with a wavelength of 88 billion light years, would it be possible to detect them

Is the Doppler effect for light symmetric?

Must spacetime be homogeneous?

Are black holes 4-dimensional balls of spacetime? If so, will they have 3-sphere surfaces?