View Full Version : When and how did humanity discover the outer planets were made of gas?

2011-Oct-16, 07:40 PM
I've been curious about this for the longest time.

2011-Oct-16, 09:34 PM
About a century ago, I think. It would have been when spectroscopy started identifying what the outer planets were made of.

2011-Oct-16, 10:29 PM
I'm pretty sure it was when the density of planets was determined by analyzing the orbits of their moons.

The term "gas giant" was coined in the 1950s by James Blish.

2011-Oct-20, 12:37 AM
Once the distance to the planets was known, their extremely low density for their size was a dead giveaway. That said, there was serious speculation on Jupiter having a solid surface well into the 20th century.

2011-Oct-20, 02:00 AM
It's one of those things you discover almost in an instant, when you get the right numbers and do the math.

2011-Oct-20, 06:46 AM
On a vaguely related note, is it just coincidence that Jupiter (the Roman "king of the gods") happens to be the largest planet? I'm wondering how ancient stargazers would have picked that specific bright moving "star" to call "Jupiter", rather than say, the one that we call Saturn or Venus. (Venus is brighter than Jupiter, and if brightness is related to how "majestic" the planet is then why didn't they call that Jupiter instead?)

(I forget if I asked this already, I couldn't find a thread about it though)

2011-Oct-20, 06:55 AM
they were told that it was the biggest by the visiting aliens.. don't you watch the History Channel?

Ronald Brak
2011-Oct-20, 07:58 AM
Venus is the most impressive planet to view from earth, but is fast and flighty and is an obvious slave to the sun, never straying far from it. While Jupiter follows a much more sedate and magestic path through the sky, unaffected by the movement of anything else and is the brightest of the planets that don't chase the sun.