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"Zero Gravity" vs Zero-G - explained by Michael at Vsauce



 
 
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  #1  
Old July 27th 14, 12:03 PM posted to sci.space.history
Stuf4
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Default "Zero Gravity" vs Zero-G - explained by Michael at Vsauce

Another topic that has received a lot of attention on this forum going back more than a decade is the point regarding how "zero gravity" is an improper term that does not conform to accurate physics. Well back in May of 2013, Michael at Vsauce made this excellent video (now with more than 5 million views):

What if You Were Born in Space?
http://www.youtube.com/watch?v=jTL_sJycQAA&t=2m29s

Quote:
==========
It's a common misconception that astronauts float around weightless in space because there is no gravity there. But there's plenty of gravity. In fact, there's pretty much the same amount of gravity operating on them that there is operating on you right now while you watch this video.

....to say that astronauts float around in orbit because they are experiencing "zero gravity" is very misleading. Really what they are feeling is zero-g, where 'g' is acceleration felt as weight.
==========


In the comments he links to an old post from our sci.space forums.

My last post today about the Cosmos thread was speaking to how much progress we've made in our understanding of basic history. Here we see how much progress we've made in our understanding of basic physics.

....and these small steps have only taken a little more than one decade!

I'll close with one final quote here...

------------------------------------
All truth passes through three stages:
- First, it is ridiculed.
- Second, it is violently opposed.
- Third, it is accepted as being self-evident.
------------------------------------
Arthur Schopenhauer, German philosopher (1788 - 1860)

The archives of this forum stand as an arduous record of those first two stages.


~ CT
  #2  
Old July 27th 14, 12:24 PM posted to sci.space.history
Stuf4
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Posts: 554
Default "Zero Gravity" vs Zero-G - explained by Michael at Vsauce

Here's another excellent webpage on the topic, from Indiana University:

"Zero Gravity, Does It Exist?"
http://indianapublicmedia.org/amomen...does-it-exist/

One quote:
==========
Contrary to popular belief, there's no such thing as zero gravity. Weightlessness and zero gravity are two different things. The earth's gravity keeps the moon in orbit. And astronauts are generally much closer to earth than the moon is, which means that the earth's pull on them has to be much stronger.
==========

That post is dated August 29, 2013, but their message is actually a lot older than that. Here's the 2002 Wayback archive:

"Is there such a thing a zero gravity? Don and Yael set the record straight in this Moment of Science."
https://web.archive.org/web/20020708...rogravity.html

Here's the full transcript of the audio:

===========
D: Yaël. Let's check with NASA and see if we can do A Moment of Science in zero gravity!

Y: There's one big problem.

D: What's that--money?

Y: Well yes, but the big one is that there's no such thing as zero gravity.

D: Come on. You see astronauts floating around weightless all the time.

Y: Yes, but weightlessness and zero gravity are two different things. Think about it. The earth's gravity keeps the moon in orbit. And astronauts are generally much closer to earth than the moon is, which means that the earth's pull on them has to be much stronger.

D: Good point. So what's really going on?

Y: Well, while we're on Earth, we feel our weight because, as the Earth's gravity pulls us into its center, the ground pushes back against our feet. When astronauts orbit the earth, they're still subject to gravity, but they're moving sideways so quickly that even though they're being pulled towards the earth, they're not getting any closer to the center of the planet. In other words, they're basically in a state of constant freefall, and that's why they're weightless.

D: But that doesn't mean zero gravity can't exist. Isn't it just a matter of moving beyond the Earth's pull?

Y: Well, gravity never disappears entirely. It just gets weaker. And every object with mass, including you and me, has what's known as gravitational attraction.

D: I've been told that I'm fairly attractive.

Y: Anyway, although you're subject to all those forces, the Earth's gravity masks their pull because the Earth is so large and so close. So moving away won't free you of the Earth's gravity. All that would happen is that the Earth's pull would be masked by the pull of some other object, like Mars.
===========


If Indiana University can have an accurate understanding of gravity, then maybe there's hope that someday NASA will too!

~ CT
 




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