# How far away from earth am I visible?
**URL:** https://boards.straightdope.com/t/how-far-away-from-earth-am-i-visible/175573
**Category:** Factual Questions
**Created:** [May 16, 2003, 12:18am UTC](https://boards.straightdope.com/t/how-far-away-from-earth-am-i-visible/175573 "2003-05-16T00:18:33Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@Bob55](https://boards.straightdope.com/u/Bob55)
#### Post date: [May 16, 2003, 12:18am UTC](https://boards.straightdope.com/t/how-far-away-from-earth-am-i-visible/175573/1 "2003-05-16T00:18:33Z")
I know that I’m visible to satellites orbiting the earth, but exactly how far away could I be seen? If someone on a planet light years away built a lense for a telescope as big as say, earth’s orbit, could they make out humans on the surface of the earth?
A recent discussion with my grandfather sparked this question - he plays a lot of golf, and at 85 years old he tends to lose the ball in the distance. He asks, “why can’t we perform a surgery that would make our eyes mimic eagle eyes?” While researching eagle vision I discovered that [An eagle](http://www.fws.gov/r5soc/faqs.htm) can see objects three to four times farther away than can a human. One study of the acuteness of eagle sight showed that an eagle can see another eagle soaring at a distance of 25 - 65 kilometers! (15-40 miles).
Another [site](http://www.pbs.org/wnet/nature/eagles/masters.html) said Eagles can spot rodents up to 2 miles away and continues to say:
> [@](#):
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> In part, eagles have excellent vision because their eyes, which are very large in proportion to their heads, are densely packed with sensory cells. While humans typically have 200,000 light-sensitive cells per square millimeter of retina, eagles may have 1 million – five times more. Similarly, while humans have only one fovea, a funnel-shaped part of the retina where vision is sharpest, eagles have two. Finally, where people see just three basic colors, eagles see five, enabling them to pick out even well-camouflaged prey.
So (back to the question at hand), it seems distance is both a result of eye size and sensory cells - does this mean that I am potentially visible from billions of light years away? Will light reflected from my body exist in space for the next billion years or so, until it is absorbed by interstellar gas or hits the edge of the universe?
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### Author:  [@Duke\_of\_Rat](https://boards.straightdope.com/u/Duke_of_Rat)
#### Post date: [May 16, 2003, 12:39am UTC](https://boards.straightdope.com/t/how-far-away-from-earth-am-i-visible/175573/2 "2003-05-16T00:39:13Z")
> [@](#):
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> \*Originally posted by Bob55 \*
> \*\*Will light reflected from my body exist in space for the next billion years or so, until it is absorbed by interstellar gas or hits the edge of the universe? \*\*
Yep…you better stop wearing those plaid leisure suits posthaste!! Can’t tell who might be watching.
We have microscopes that are millions (?) of times more powerful than an eagle’s eye and still can’t see everything. Not sure of the scale, but sub-atomic particles would seem to be larger to an eagle, relatively speaking, than you are at a billion light years.
I say go for the nude sunbathing!