ElI5: How does anything in space not just get destroyed by high speed objects accelerating through space? How can we have space stations that are not blasted with huge holes from impacts?
In: Engineering
To expand on the whole “space is empty” bit.
I want you to imagine an asteroid belt. Alright, now forget about it, because real asteroid belts look absolutely nothing like what you see on science fiction television. There aren’t clear borders where they start and end, they aren’t filled with big rocks all just hovering in orbit about the sun – and specifically NOT collapsing into a planet… The real asteroid belt is mostly dust and gravel, out there, between Mars and Jupiter. When we send probes through it, there’s actually no concern whatsoever that the trajectory is going to collide with a big rock. What few rocks we have sent probes to are the exception, and notable for their size.
Think of the electromagnetic spectrum. Everything from gamma rays, to visible light, to WiFi, to radio waves… It all exists on one spectrum, it’s all happening at once. Now, electromagnetism has some propagation rules – it’s why WiFi doesn’t reach far, it’s absorbed into the air and moisture in the atmosphere. But space overall is exceptionally quiet. The vast majority of the spectrum, there’s nothing. It makes radio astronomy all the more interesting that they have an idea of what signals to look for, what they mean, and that they come from so far away and yet we can still reliably pick them up, it’s astounding. Black hole collision billions of years ago on the other side of the universe? We get the occasional blip.
Most of what you’ll find in open space are random hydrogen atoms. The heavier elements we come across are mostly leftovers from the second generation stars that went supernova, scattered their guts, and created the nebula that birthed our star and solar system. All that dust coalesced due to gravity, angular velocity was preserved, the disk spun in one direction, and that is the direction the sun and planets orbit and rotate. Most all of it has formed a few rocky planets, fell into the sun, or got ejected out like a projectile, or were swept up by the gas giants.
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