Was Kepler the First to Measure the Distances from Earth to All Known Planets?

In summary, Kepler was the first to discover that the orbital period is proportional to the cube of the radius and that Saturn was 900 million miles from Earth.
  • #1
Thecla
131
10
Can we say that Kepler in the early 17th century was the first person to know the distance from the Earth to all the known planets?
One of his laws:The square of the orbital period is proportional to the cube of the radius(actually the semi-major axis). So he new Saturn was about 900 million miles from the earth, Jupiter about 400 million miles away. Was he the first? Copernicus didn't know. Brahe?.
By the time Newton was born the size of the Solar System was well known among European astronomers.
 
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  • #3
Thecla said:
By the time Newton was born the size of the Solar System was well known among European astronomers.

The solar system extends all the way through the Ort Cloud, about half the distance to the next nearest star. They didn't know THAT.
 
  • #4
I'm not sure what you consider the edge of the solar system, but if it is the bow shock, that's a tiny fraction of the distance to the nearest star.
 
  • #6
  • #7
The thread title is rather misleading. The OP is really asking who first knew the distances from the sun to the known planets. As in whatever planets were known at the time -- I guess this would mean the planets out to Saturn.
 
  • #8
Kepler knew the relative distances between planets, but I'm not sure if he knew any absolute distances. Had they figured out a way to measure the length of 1 AU at that point?
 
  • #9
relating to all this ... this statement... "At the great distances of the Oort Cloud, comets can be affected by the gentle gravitational tugs of nearby passing stars. The passing stars tug on the comets, "perturbing" their orbits, sending some of them into the inner solar system" from the page ... http://www.astronomynotes.com/solfluf/s8.htm chronos listed above, and other printings I have seen over the years, has always irked me

nearby passing stars ?? are there stars closer than the Alpha Centauri system passing by that we have never seen ?
or... can the Alpha Centauri trinary system at 4.3 lightyears affect objects in the Oort Cloud ?

Dave
 
  • #10
Agreed, although we could just now be seeing comets perturbed by rogue stars passing by a many thousands of years ago.
 
  • #11
Thecla said:
Can we say that Kepler in the early 17th century was the first person to know the distance from the Earth to all the known planets?
One of his laws:The square of the orbital period is proportional to the cube of the radius(actually the semi-major axis). So he new Saturn was about 900 million miles from the earth, Jupiter about 400 million miles away. Was he the first? Copernicus didn't know. Brahe?.
By the time Newton was born the size of the Solar System was well known among European astronomers.

In the late Middle Ages they had a sufficient idea of the distances to estimate that Jupiter and Saturn were bigger than the Moon. But past that the distances were hazy. In Ptolemy's geocentric model the sphere of stars was estimated to be about 20,000 Earth radii away. Thus Earth was just a tiny speck in an immense and perfectly working system of moving nested spheres, in their mechanistic model. The Greeks didn't believe truly empty space was possible and couldn't imagine action-at-a-distance forces, so they imagined a bunch of cosmic gears made of invisible material supported the planets and the celestial sphere.
 
  • #12
Thecla said:
Can we say that Kepler in the early 17th century was the first person to know the distance from the Earth to all the known planets?
There is not really a "first person".
The Earth-Sun distance (astronomical unit, AU) was measured with increased accuracy, starting around 17th century, using the transits of Venus and Mars.
Older estimates were made even in ancient times but not very close, I think.

The relative distances were known during Kepler times. It's not clear for me if he knew about the first modern absolute measurements.

Based on Kepler law, is sufficient to measure the absolute value of the AU and then all the other planetary distances can be found as absolute values.
 

1. How big is the Solar System?

The Solar System is vast, spanning approximately 4.5 billion kilometers from the Sun to the outer edges of the Kuiper Belt. It is difficult to accurately measure the size of the Solar System since it is constantly expanding and changing. However, the average distance from the Sun to the Earth, known as an astronomical unit (AU), is about 150 million kilometers.

2. What is the largest planet in the Solar System?

Jupiter is the largest planet in our Solar System, with a diameter of 142,984 kilometers. It is more than 11 times wider than Earth and has a mass of 1.9 x 10^27 kilograms. It is also the fifth planet from the Sun and is known for its iconic Great Red Spot, a massive storm that has been raging for centuries.

3. How many planets are in the Solar System?

There are eight planets in the Solar System: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. These planets are classified as terrestrial (Mercury, Venus, Earth, and Mars) or gas giants (Jupiter, Saturn, Uranus, and Neptune). In addition to these eight planets, there are also five dwarf planets: Ceres, Pluto, Haumea, Makemake, and Eris.

4. What is the farthest object in the Solar System?

The farthest object in the Solar System is currently believed to be a dwarf planet named Eris, located in the Kuiper Belt. It is about 96 AU away from the Sun, making it almost 14.4 billion kilometers from our star. However, there may be undiscovered objects beyond Eris that could be even farther away.

5. How long would it take to travel to the edge of the Solar System?

The Solar System has no defined edge, so it is difficult to determine how long it would take to reach it. However, if we consider the outermost planet Neptune as the edge, it would take a spacecraft traveling at the speed of light (299,792,458 meters per second) about 4 hours and 7 minutes to reach it from the Sun. However, with current technology, it would take much longer, as our fastest spacecraft would take about 30,000 years to reach Neptune.

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