<p>The solar system and the Earth have formed billions of years ago from a pile of stuff (mostly hydrogen gas and rocks, with traces of other things) that collapsed together due to gravity pulling all those parts together.</p>

<p>The current orbital speeds and spin motions of planets are just residuals from that collapse. In other words, a pile of rocks and stuff collapsed and made the Earth, and the result happened to spin at whatever rate back then - and that's all there is to it. Other "piles of stuff" (planets) spin at different rates, because that's how they collapsed from the cloud of gas and rubble; there's no special reason for it.</p>

<blockquote>
  <p>Isn't acceleration infinite out in space?</p>
</blockquote>

<p>Acceleration only happens when there's an external force accelerating the object along its direction of motion. I.e. when something is actively pushing it.</p>

CC BY-SA 3.0
2017-04-17T22:29:11.253Z
Thank you. So, eventually the earth's spin will be too slow to support life?
LetTheWritersWrite
CC BY-SA 3.0
2017-04-17T22:36:42.027Z
@LetTheWritersWrite It is not clear whether life requires the planet to spin. The conditions would be dramatically different on a tidally locked planet, with the eternal day side too hot and the eternal night side too cold, but the climate might be temperate near the terminator (the region in between day and night). But the Earth will become inhospitable to life much sooner than that, for different reasons (the Sun will go end-of-life in a few billion years).
Florin Andrei
CC BY-SA 3.0
2017-04-17T22:06:19.057Z
2017-04-17T22:06:19.057Z
Florin Andrei
<p>If we assume that the big bang creates 'all', and the expansion is not of matter in a pre-existing space, but of matter in a co-existing space, created with it, then no acceleration exists at all...</p>

CC BY-SA 3.0
2017-04-17T21:20:28.007Z
But how did the earth remain spinning at the perfect speed?
LetTheWritersWrite
CC BY-SA 3.0
2017-04-17T22:00:30.327Z
@LetTheWritersWrite A) There is no "perfect speed". B) The spin rate of the Earth has changed through its history, and continues to change even now. It spins at whatever speed it happens to spin now, and that's all there is to it.
Florin Andrei
CC BY-SA 3.0
2017-04-17T16:19:12.530Z
2017-04-17T20:30:41.763Z
2017-04-17T20:30:41.763Z
xxavier
<p>I'm not scientist at all so the answer might be obvious but I was pondering about the big bang. I started wondering how is it possible that the earth had to accelerate at some point in history to the speed it currently has but not continue accelerating past it? Isn't acceleration infinite out in space?</p>

CC BY-SA 3.0
2017-04-17T17:01:16.593Z
1) Earth formed about 9 billion years after the big bang 2) acceleration is not infinite in space
Asher
CC BY-SA 3.0
2017-04-17T17:36:32.807Z
I never asked when it was formed.If acceleration isn't infinite, how does the earth remain in orbit at the same speed? Isn't gravity causing friction?
LetTheWritersWrite
CC BY-SA 3.0
2017-04-17T17:40:42.653Z
You didn't have to ask when Earth was formed. You said you were pondering the Big Bang and then transitioned to talking about the Earth accelerating as if the two ideas were connected somehow. Asher was just pointing out these two events were separated by 9 billion years and unconnected.
zephyr
CC BY-SA 3.0
2017-04-17T17:44:16.817Z
But they are connected. Bang, mass explodes, cools down, become rocks, rocks continue spinning into planets and galaxies form.......
LetTheWritersWrite
CC BY-SA 3.0
2017-04-17T21:59:16.443Z
No, gravity does not cause friction.
Florin Andrei
<big-bang-theory>
How does the earth not continue accelerating?
LetTheWritersWrite
# How does the earth not continue accelerating?

(Asked by: username_0 on 2017-04-17)

I'm not scientist at all so the answer might be obvious but I was pondering about the big bang. I started wondering how is it possible that the earth had to accelerate at some point in history to the speed it currently has but not continue accelerating past it? Isn't acceleration infinite out in space?

**Tags:** big-bang-theory
> **Comments:**
> **username_1**: 1) Earth formed about 9 billion years after the big bang 2) acceleration is not infinite in space  
> **username_0**: I never asked when it was formed.If acceleration isn't infinite, how does the earth remain in orbit at the same speed? Isn't gravity causing friction?  
> **username_2**: You didn't have to ask when Earth was formed. You said you were pondering the Big Bang and then transitioned to talking about the Earth accelerating as if the two ideas were connected somehow. Asher was just pointing out these two events were separated by 9 billion years and unconnected.  
> **username_0**: But they are connected. Bang, mass explodes, cools down, become rocks, rocks continue spinning into planets and galaxies form.......  
> **username_3**: No, gravity does not cause friction.  

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## 2 answers

### Answer by username_3 on 2017-04-17. Score: 1 | Accepted answer

The solar system and the Earth have formed billions of years ago from a pile of stuff (mostly hydrogen gas and rocks, with traces of other things) that collapsed together due to gravity pulling all those parts together.

The current orbital speeds and spin motions of planets are just residuals from that collapse. In other words, a pile of rocks and stuff collapsed and made the Earth, and the result happened to spin at whatever rate back then - and that's all there is to it. Other "piles of stuff" (planets) spin at different rates, because that's how they collapsed from the cloud of gas and rubble; there's no special reason for it.

> Isn't acceleration infinite out in space?

Acceleration only happens when there's an external force accelerating the object along its direction of motion. I.e. when something is actively pushing it.

> **Comments:**
> **username_0**: Thank you. So, eventually the earth's spin will be too slow to support life?  
> **username_3**: @LetTheWritersWrite It is not clear whether life requires the planet to spin. The conditions would be dramatically different on a tidally locked planet, with the eternal day side too hot and the eternal night side too cold, but the climate might be temperate near the terminator (the region in between day and night). But the Earth will become inhospitable to life much sooner than that, for different reasons (the Sun will go end-of-life in a few billion years).  

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### Answer by username_4 on 2017-04-17. Score: -2

If we assume that the big bang creates 'all', and the expansion is not of matter in a pre-existing space, but of matter in a co-existing space, created with it, then no acceleration exists at all...

> **Comments:**
> **username_0**: But how did the earth remain spinning at the perfect speed?  
> **username_3**: @LetTheWritersWrite A) There is no "perfect speed". B) The spin rate of the Earth has changed through its history, and continues to change even now. It spins at whatever speed it happens to spin now, and that's all there is to it.  

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