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# Space Exploration/lightyear exploration

Question
Hello. I understand that the universe is endless.  But I was wondering about how many light years of space have been explored.

Hi Johann,
Depends on your definition of "explored"... if you mean by actual human travel, we've been to the surface of the moon 6 times with Apollo 11, 12, 14, 15, 16, and 17.
The moon is about 1.3 light-seconds distant.
If you mean robotic spacecraft, then the current record holder is Voyager 1 at about or approaching 12 billion miles, see http://www.heavens-above.com/
and punch on "Spacecraft escaping the Solar System".
Since there are about 6 trillion miles in a light year, the fraction of 12 billion over 6 trillion, which looks like this arithmetically
is 12,000,000,000/ 6,000,000,000,000 which reduces to 12/6000 which (divide both sides of the fraction by 12), and you get 1/500th of a lightyear.  A better unit to use is the AU or distance from the sun to the Earth... Voyager I is approaching 126 AU from the sun. (There are 63,240 AU in one light year.)  So 63,240 / 500 = about 126 AU.

If you are talking telescopes and recording light (and other electromagnetic radiation) then we've "seen" or "explored" nearly back to the Big Bang 13.7 billion years ago, or 13.7 billion
light years distance.  The Cosmic Background Microwave picture goes back to only some 380,000 years after the Big Bang.
Hope this helps,
Clear Skies,
Tom Whiting
Erie, PA

Space Exploration

Volunteer

#### Tom Whiting

##### Expertise

I can answer most questions about space flight and planetary exploration from an astronomy standpoint, but not from a computer or electronics standpoint. No astrology questions please, or questions about alleged UFO identifications.

##### Experience

Astronomy, my main catagory, has been my hobby and pastime for over 50 years. Taught astronomy and meteorology at the University level for over 13 years.

Organizations
President- Erie County Mobile Observers Group for over 15 years. Also on allexperts.com astronomy catagory for over 8 years.

Publications
Astronomy Technology Today and also wrote the "Over Erie Skies" column in our local newspaper for 11 years.

Education/Credentials
BS Metallurgical Engineering Grove City College, PA Master's Degree, Gannon University, Erie, PA Also retired USAF pilot, 20 years.

Awards and Honors
Discoverer of the mini-coathanger asterism in Ursa Minor; also the mini-dipper asterism up in the bowl of the Little Dipper.