meta user
network profile
| bio | website | leosondra.cz |
|---|---|---|
| location | Rančířov near Jihlava, Czech Republic | |
| age | ||
| visits | member for | 1 year, 4 months |
| seen | 20 mins ago | |
| stats | profile views | 47 |
|
May 30 |
comment |
Why do helium filled balloons move away from the Earth? +1 for the pressure gradient which is quite important |
|
May 28 |
comment |
Parallax, obliquity, precession, and Orion? @Rob Let's consider Betelgeuse (alpha Orionis, the bright reddish star at a Orion shoulder). At present (epoch 2000), its ecliptical coordinates are 88.7546 and -16.0270. Conversion to the year -4500 gives ecliptical latitude -16.9027 degrees. So the distance from ecliptic was greater than is now. |
|
May 18 |
comment |
Is period of rotation relative? "But that doesn't mean, that the pulsar is rotating 0.15 slower in the observers space-time". Why? |
|
May 18 |
comment |
Parallax, obliquity, precession, and Orion? Your answer is irrelevant, since ecliptical latitudes of stars change in time significantly even for geocentric observer. |
|
May 18 |
comment |
Parallax, obliquity, precession, and Orion? -1 "Keep in mind that the obliquity you've mentioned here is the angle of Earth's axial tilt with respect to the ecliptic. The angle of the ecliptic is relatively unchanging." That's not true. |
|
May 18 |
answered | Parallax, obliquity, precession, and Orion? |
|
May 17 |
awarded | Nice Question |
|
May 16 |
comment |
From where (in space-time) does Hawking radiation originate? @Nathaniel I am not sure if I undestood Nathaniel correctly, but myself I would formulate the problem as follows: Distant observer sees Havking radiation from a black hole (with Planck spectrum and say measurable temperature). Now suppose there is a gas between the event horizon and the observer - would the observer detect absorption line in the black hole spectrum? How does this result change if the gas is free falling? How does it change with distance of the gas (or the observer) from the black hole. Will the distant observer observer the lines if he is free falling? |
|
May 16 |
comment |
Gravitational redshift of Hawking radiation @JohnRennie I see - so the radiation comes from the just outside the horizon and the redshift is quite large but finite, reducing the temperature to low values observed but still greater than zero. |
|
May 16 |
comment |
Can general relativity be completely described as a field in a flat space? @Anixx There is a difference between spacetime being flat and space alone being flat. The word universe is this context is somewhat ambiguous. |
|
May 15 |
asked | Gravitational redshift of Hawking radiation |
|
May 13 |
awarded | Custodian |
|
May 13 |
reviewed | Approve suggested edit on Is period of rotation relative? |
|
May 10 |
comment |
Is period of rotation relative? I would guess that solely the gravitational dilation would slow the time by about 15 percent... |
|
May 10 |
asked | Is period of rotation relative? |
|
May 8 |
comment |
Mirror image at relativistic speeds Naively, I would say there must be some kind of Doppler efect in action - or police would not be able to measure a car speed with radar? |
|
May 7 |
comment |
Can spacetime be non-orientable? @LubošMotl "For example, a left-handed neutrino would turn into a right-handed neutrino if you made a round trip." Does this argument apply also in the expanding universe where is not possible - as far as I know - to make a round trip? |
|
May 5 |
comment |
Historic derivation of Wien's law @MyUserIsThis Ok, I will try to post here a summary as soon as possible (in English, of course). |
|
May 5 |
comment |
Historic derivation of Wien's law The 1893 paper by Willy Wien appeared in Sitzungber. preuß. Akad. Wiss. Berlin, 55 (1893). It was presented by Helmholtz at meeting of the Academy on February 9, 1893. I have a translation to Russian in the book "Von Kirchhoff bis Planck" by Hans-Georg Schöpf. If you are interested I can find it and post a summary. |
|
May 4 |
asked | Does it make a sense to speak about age of electron or atom? |
