How would a man on earth appear from outer space

In summary, the conversation discusses the appearance of a man dropping a ball from Earth to someone watching from outer space and the existence of pseudo forces due to the Earth's rotation. It is mentioned that these forces emerge when assuming a stationary reference frame but actually being in a rotating one. The question of feeling these forces is also brought up, with the conclusion that they are too weak to be felt in the presence of gravity. Additionally, it is noted that the appearance of the man and ball dropping from Earth is dependent on the watcher's reference frame.
  • #1
vijay_singh
28
0
Hi

I was reading a general physics book and wondered how would a man on Earth appear to somebody watching from outer space.
Say for example a man on Earth just drops a ball from his hand, will it appear to somebody watching from outer space, as if the ball is released tangent to the spin of the earth?

I hope my question makes sense!

Another question, why don't we feel the pseudo force due to the Earth's rotation on its axis? or is it too weak?
 
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  • #2
We do feel pseudo forces. That's why tornados and hurricanes (but not toilets) spin different directions in different hemispheres (because of the fictitious Coriolis force) and why the Earth is kinda like a squashed sphere not a perfect sphere (centrifigal force). In general these fictitious forces emerge when we assume we are in a stationary reference frame but actually are in a rotating one (see http://en.wikipedia.org/wiki/Rotating_reference_frame). However, how we look to a person in space is ENTIRELY dependent on what the reference frame of the person is. For example, if the person was in geosynchronous orbit they wouldn't see anything odd.
 
  • #3
vijay_singh said:
Another question, why don't we feel the pseudo force due to the Earth's rotation on its axis? or is it too weak?
It is too weak to be felt, in the presence of gravity. More precisely, it's about 300 times weaker than gravity (at the equator), and a human can't pick out that 1-in-300 difference. If there were no gravity, you'd probably be able to feel the centrifugal force, though; about 1.5-2 N on an average adult.
 
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  • #4
Hi vijay! :smile:
vijay_singh said:
Say for example a man on Earth just drops a ball from his hand, will it appear to somebody watching from outer space, as if the ball is released tangent to the spin of the earth?

Yes, if the Earth is dark (because it's night), but the ball is lit, then all the watcher will initially be able to see is the ball moving tangent to the spin of the earth, as you say. :smile:
 
  • #5
Thank you all for responding and confirming the answers.
 

1. What would a man on earth look like from outer space?

The man would appear as a small dot or speck, as the distance from outer space to earth is vast. Depending on the specific location and lighting, the man may also appear as a shadow or silhouette against the surface of the earth.

2. Would a man on earth be visible to the naked eye from outer space?

No, a man on earth would not be visible to the naked eye from outer space. As mentioned before, the distance is too great for a human to be seen without the use of powerful telescopes or other equipment.

3. Can a man on earth be seen from outer space at night?

Yes, a man on earth can be seen from outer space at night if he is standing in a well-lit area, such as a city or near a large fire. However, the man would still appear as a small dot or speck, and may be difficult to distinguish from other lights on the earth's surface.

4. How would a man's appearance change if he were on the moon?

If a man were on the moon, he would appear much smaller than if he were on earth. This is because the moon is much smaller than the earth, and therefore a human would take up less space in the field of view from outer space. The man may also appear white or grey in color, depending on the lighting and the surface of the moon.

5. Can a man on earth be seen from other planets in our solar system?

No, a man on earth cannot be seen from other planets in our solar system. The distance between planets is too great for a human to be seen without the use of advanced technology. Additionally, the man would appear even smaller from other planets due to their greater distance from earth.

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