Buzz
The Hubble Space Telescope during its 2009 servicing mission
Image courtesy of NASATo understand how telescopes can peer into the past, consider this modern example: observing our sun. While it’s not advisable to stare directly at it, if you were to glance at the sun right now, you’d actually be seeing light that left its surface eight minutes ago. In essence, you’re witnessing the sun as it was in the past.
Isn’t this fascinating? In a way, we’re living in the future! Imagine being able to inform the sun about the World Series winner eight minutes before it happens, potentially turning solar gambling into a lucrative venture.
Sadly, we aren’t privy to the universe’s wonders before anyone else. Instead of catching a glimpse of the future, we’re simply too distant to witness what’s currently happening to the sun. This phenomenon revolves around light and its speed. Light moves at 186,000 miles (300,000 kilometers) per second [source: Russell]. In scientific terms, that’s astonishingly fast.
Light’s speed is so immense that when we turn on a lamp, we never perceive a delay. The light reaches us almost instantaneously because of its proximity. However, the sun’s rays, which are 92 million miles (150 million kilometers) away, have a significant journey to Earth. As a result, we always see the sun as it was eight minutes ago. If the sun were to vanish suddenly, we wouldn’t know for eight minutes.
The sun is merely a nearby example. When we gaze into deep space using telescopes, the same principle applies. For instance, Alpha Centauri, the closest star to us, is 4.2 light years away [source: Russell]. This means we’re seeing it as it appeared 4.2 years ago.
Telescopes such as the Hubble observe galaxies located 100 million light years away. Just as the sun appears eight minutes older than it actually is, these galaxies are seen as they were 100 million years ago. If we were on one of those distant galaxies right now, peering at Earth through a powerful telescope, we’d witness dinosaurs roaming our planet.
In essence, those distant galactic observers would also be peering into the past as they watched Earth.
