Special & General Relativity Questions and Answers
If we traveled 100 light years into space, would we really see the Earth as it was 100 years ago?
From the Earth, Apollo astronauts on the Moon had a 1.3 second delay before receiving radio signals from Earth. The Earth was always 1.3 seconds in their past. Similarly, if you were out at 100 light years, any Earth signal you received, would have been emitted from Earth 100 years in your past, so in essence, you would always see the Earth as it was 100 years in your past.
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All answers are provided by Dr. Sten Odenwald (Raytheon STX) for the NASA Astronomy Cafe, part of the NASA Education and Public Outreach program.