Strict-Currency2840 t1_ith7i3y wrote on October 23, 2022 at 5:04 PM

Reply to comment by OrokaSempai in A Nearby Star Has Completely Blasted Away the Atmosphere From its Planet by Tao_Dragon

I’m pretty sure the earth is like 4 billions years old so I don’t think that’s right

OrokaSempai t1_ith8dks wrote on October 23, 2022 at 5:10 PM

4.543B. 543M years is plenty for an atmosphere to form. Hell, oldest known evidence of life on Earth is 3.7B.

Anyways, here is a credible source

https://forces.si.edu/atmosphere/02_02_01.html#:~:text=(4.6%20billion%20years%20ago)&text=As%20Earth%20cooled%2C%20an%20atmosphere,from%20gases%20spewed%20from%20volcanoes

flipmcf t1_itji6hh wrote on October 24, 2022 at 2:31 AM

Thanks. My point is that our star is very well behaved and our magnetic field is quite reliable. Probably a combination of both.

I just googled and found that Venus has no magnetic field today. So I guess our star is pretty well behaved, and Venus has sone good gravity.

I’ve always thought that if the momentum / velocity of a gaseous molecule is greater than the escape velocity of the planet… bye bye gas! No H2 or He in earth’s atmosphere because at ‘earth temperature’ that gas just can’t remain captured by earth’s gravity.

But I don’t know if that’s an actual thing b/c I never researched it or did the math. It’s just a theory.

And slamming charged particles into a planet’s atmosphere at relativistic speeds is surely also a contributing factor to removing an atmosphere. - just to bring the conversation back on topic.

Zprotu t1_itod3zu wrote on October 25, 2022 at 2:55 AM

Question. We know the earth is 4.543B years old, but what exactly does this number mean? Technically, wouldn't the creation process of the earth have started right at the moment of the solar system's beginning? (i.e the exact second of the gravitational collapse of the giant interstellar molecular cloud, so 4.6B years ago, adding about 400M years to the age)

OrokaSempai t1_itpn6iy wrote on October 25, 2022 at 11:59 AM

At some point 2 grains of sand stuck together that would eventually become the earth, but is that actually the earth? Before the moon was formed in an impact with another proto-planet, it was not the same size or composition as today, so at that point it was also a proto planet. That impact was the final step to those proto planets becoming the Earth and Moon, so personally I would say the earth is 4.5B years old, the point it became its final mass. (Also, the cores of the 2 proto planets would have combined at that point giving the earth a large core and powerful magnetic field).

Zprotu t1_itubxzx wrote on October 26, 2022 at 11:26 AM

Well all that is definitely included in the creation process of the earth to what it is today. Its why I would consider the point in time when the 2 grains of sand got stuck together as the start of the earth. We are talking about the beginning of earth's creation process after all. And this process began exactly at the moment of the gravitational collapse of the interstellar molecular cloud, no? Wouldn't thinking that the earth is 4.6B years old be correct if you frame it like that?