All Questions
46
questions
1
vote
1
answer
63
views
Andromeda Galaxy and Hubble
When Hubble determined the distance to Andromeda he based his estimation on Cepheids. However, the result was less than half the current value. What was the cause of this error and could another ...
- 167
0
votes
1
answer
88
views
How can the distance to the Sun from the Earth be determined without relying on any prior baseline measurements?
I am asking if there is a way that a man could determine the distance from the earth to the sun without already having a baseline distance or dimension measurement to begin with, and without having ...
- 1
12
votes
6
answers
6k
views
How could Tycho Brahe determine positions without accurate clocks?
Tycho Brahe determined the positions of stars and planets to an accuracy of 2 minutes of angle. Pendulum clocks hadn't been invented yet so he couldn't have known the time to better than 15 minutes. ...
- 165
10
votes
3
answers
2k
views
Proof/explanation that Sun is bigger and more distant from Earth than Moon is, Middle Age technology allowed only
If I was living in the Middle Ages, how can someone prove or at least explain to me in a simple way that the Sun is bigger and more far from Earth than the Moon?
Can a parallax be used for it?
$$\text{...
- 191
-1
votes
2
answers
185
views
What is the logic behind the Eddington expedition that proved Einstein's general theory of relativity?
The Eddington expedition in 1919 proved Einstein's general theory of relativity.
[Eddington] argued that the deflection, or bending, of light by the Sun’s gravity could be measured... because ...
- 81
18
votes
3
answers
3k
views
On the Rømer experiments and the speed of light
In 1676, Rømer determined that the speed of light must be finite.
His experiment consisted on observing the eclipses of Io, one of Jupiter's moons, by Jupiter itself. He timed these eclipses over a ...
user137661
4
votes
0
answers
144
views
What is novel about the analysis showing that Mercury is "closer" to Earth than Venus?
Why is the recent analysis showing that Mercury and not Venus is on average the closest planet considered new?
This should surely come as no surprise to anyone who has ever looked at a plot of the ...
- 5,145
3
votes
1
answer
181
views
Did Eratosthenes make his measurements on the same day?
Erasthosenes measured the circumference of the earth on the summer solstice by observing the sun at Alexandria and Syene.
Was this done on the same day in one year or on the same day in two ...
- 331
2
votes
1
answer
167
views
'Harmony of the Spheres' or 'Harmony of the World' - is it debunked? [closed]
I sincerely apologise for this vague question but I'm writing an essay for my music class on musical harmony and it's historical origins. I came across the Pythagorean notion of Harmony of the Spheres ...
user136975
3
votes
1
answer
448
views
Transit of Venus and the computation of the Astronomical Unit
I have searched for the computation of the AU. The two best websites I found about it were
https://sunearthday.nasa.gov/2012/articles/ttt_75.php
How did Halley calculate the distance to the Sun by ...
- 172
2
votes
1
answer
359
views
How could Eratosthenes know the angle of the sun's rays in Alexandria?
The measurement of the Earth's radius by Eratosthenes is famously the first of its kind. As I understand, it relies on the fact that the sun's rays are parallel. At noon, the light falls directly ...
- 4,788
4
votes
1
answer
217
views
Kepler's genius, How?
I have a very simple question. How Kepler knew that orbits are elliptical, say I was living in his time. How would Kepler explain that the orbits are elliptical (since none of his 3 laws explain why ...
- 63
0
votes
1
answer
128
views
First method to observe solar prominences without an eclipse
What was the first method used to observe solar prominences without an eclipse?
I understand that Helium was first discovered in the Sun, separately by Pierre Janssen and Norman Lockyer, in 1868, ...
- 101
0
votes
1
answer
197
views
Alexandrian knowledge on distance of Sun from Earth
In the book "Cosmos", Carl Sagan describes the methods used by Eratosthenes in determining the radius of earth (Chapter 1). Going through the steps of the method, he makes the statement "The Sun is so ...
- 771
6
votes
2
answers
252
views
How could the precession of Mercury be known so accurately in the 19th century?
The discrepancy between the observed precession of the perihelion of Mercury and the value predicted by Newtonian theory was known in the 19th century to be approximately 43 arcseconds per century.
...
- 9,304