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Comment by jungletime | Hacker News Reader

Does Earth's atmosphere ever spill out into outer space? Is it possible for an asteroid to pass through our outer atmosphere, and then fly on to hit Venus?

In some ways humans are simpler than the cells they are made off. Yeah, you may know how to drive a car, but can you synthesize DNA? I find it fascinating that complexity goes up, when you zoom into a human. And cells exhibit all these behaviours.

There was this video I watched once, where a white blood cell was chasing a bacteria around. And it looked like a game of pacman. I would have never expected that a cell has some sort of self awareness, and is able to navigate its environment.

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Cells don't have self-awareness. You need brains for that. Just because something acts purposeful and goal-directed doesn't make it self-aware, unless you think a Roomba is self-aware.

But you're right, cells are must more complex than our intuition often gives them credit for. But the time you get to a bacterium, fully 50% of the basic biomechanics of life are already in place. In fact, you can think of yourself as little more than a colony of specialized "bacteria" that self-organized into a whole that is greater than the sum of its parts, not at all unlike the way humans self-organize into groups (tribes, city-states, nation-states, corporations) that are greater than the sum of their parts.

> you may know how to drive a car, but can you synthesize DNA?

I think the framing is wrong here. A cell synthesizes DNA mechanically and without will or intent. The cell is made up of molecules that grab other molecules and operate on the other molecules to do something (repair, replicate, infect, etc.). When the right molecules come into contact with their targets, the synthesis just happens by the chemistry and physics that dictate the shape and movement of the molecules (modulo the stochastic and probabilistic process of other molecules moving around and becoming available). What we call life is an ever more complex set of molecules and their organization that allows their mechanical self-replication--and the other complex processes that extract and build all the constituent molecules from the environment (by building other molecular structures such as cell walls that also act mechanically on the molecules of the environment).

This is certainly a fascinating notion, but it assumes arbitrary boundaries that have no real foundation in reality. Imagine instead what a staggering feat it is that the very cells that demonstrate all these remarkable biochemical behaviors can work in concert to drive a car!

I find this change in perspective to be quite instructive...that "humans" are not made of "cells," so much as collections of "cells" have developed a behavior that we describe as "human."

It is not possible for an asteroid to do that. If a space rock hit our atmosphere, it would either burn up or rapidly lose speed and crash to the ground.

I know the white blood cell animation you are talking about.

White blood cells are not self-aware. It might be helpful to picture cells (and even large animals) not as the discrete objects that are seen by the naked eye, but rather as a cloud of "stuff". In the middle is the meat; on the outside is various liquids, particles, and gases that leak out. So, the white blood cell isn't keeping an eye on the bacteria and chasing it. It's increasing contact with the "stuff" that it recognizes as foreign.

This is incorrect, meteorites can skip off the Earth’s atmosphere. The 1972 great daylight fireball is an example of such an object.

When a sufficiently large asteroid[0] slams into Earth, the impact plume[1] can hoist matter off the surface. The velocity of said matter may be sufficiently high to escape Earth's orbit, potentially seeding the solar system with life[2].

[0]: https://impacts.to/downloads/lowres/impacts.pdf#page=21

[1]: https://youtu.be/bU1QPtOZQZU?t=70

[2]: https://en.wikipedia.org/wiki/Panspermia#Lithopanspermia

I'm pretty sure driving a car requires more complexity than synthesizing DNA. Humans make up a very small percentage of all life on earth and only we can drive cars while most other life can make DNA

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