Contemplating: As You Gazes at the Stars, It's Like Peering into the Past
Contemplating: As You Gazes at the Stars, It's Like Peering into the Past
If the universe is 13.6 billion years old, it may seem surprising that astronomers can observe galaxies near the Big Bang, which birthed the universe. However, this phenomenon becomes less extraordinary once you grasp the concept of light.
Everything you perceive is a relic of the past. Light travels at 186,282 miles per second (299,792 kilometers per second) - swift, yet still sufficient to require time to reach your eyes. For a lamp, that time is a mere millisecond. Your brain, in its turn, needs 13 milliseconds to process the information. A lapse of 14 milliseconds may be imperceptible, yet it's indisputable that all light you observe is a representation of the past.
You perceive the world as it was, not as it truly is.
Eleventh Hour Light
This concept is particularly relevant when gazing at the night sky. The light you witness - be it sunlight, moonlight or starlight - has traversed significant distances to reach your eyes.
For instance:
- Moonlight requires 1.28 seconds to reach your eyes.
- Sunlight takes 8 minutes and 20 seconds to reach your eyes.
- The light emanating from the brightest visible star in the northern hemisphere's night sky, Sirius, takes 8.6 light years - a considerable distance. Catch a glimpse of it tonight, as it rises in the southeast a few hours after dark, and you'll be observing it as it was in 2015.
(A light-year is the distance covered by light at 186,282 miles per second within a year on Earth.)
- The light from Dubhe in the Big Dipper takes 125 years to arrive.
- Polaris's starlight requires 433 years to reach your eyes.
- The stellar light from the Andromeda galaxy (M31) has traveled an astounding 2.5 million light-years.
At that time, Earth was in the Pleistocene Epoch, and our early human ancestors, Homo habilis, had only recently emerged in East and South Africa.
Galactic Sovereignty
Our cosmic neighborhood itself is diverse. Andromeda, for instance, falls within the same Local Group as the Milky Way (the most distant celestial object visible to the naked eye). With the aid of telescopes, you can even spot galaxies like M81 and M82, situated a staggering 11 million light-years away. Consider the distance this light has traveled: we're looking into a past where Earth was in the Miocene Epoch, a time when horses, camels, deer, and elephants were beginning their evolutionary journey.
Beyond these nearby galaxies lie billions more, many of them billions of light-years distant - the focus of astronomers' fascination. These galaxies are situated near the very edge of the universe's creation - their light having taken the universe's entire existence to reach us.
Expanding Universe
Astronomers can observe approximately 46 billion light-years in any direction. How can that be, given the universe's 13.8 billion-year age? Because the universe is expanding. All celestial bodies you witness are not only viewed as they were in the past but are also moving away from us at an accelerating pace. Astronomers can detect light from such vast distances due to the universe's expansion, not because the light has traveled for 46 billion years.
Remote galaxies appear red because their light is stretched - or 'redshifted' - by the expanding universe. This 'redshift' results in longer wavelengths, hence the red color.
The Hubble Ultra Deep Field showcases about 100 tiny, red galaxies - some of the most distant known, having emerged when the universe was a mere 800 million years old. Recently, the James Webb Space Telescope, with its sharper, more sensitive optics, has been able to scrutinize infrared light, peering through the dust and gas that characterize early galaxies. The further infrared a telescope can detect, the further it can travel into the past, reflecting on the Big Bang. The deepest image generated so far by the Webb, titled 'Webb's First Deep Field', was unveiled in 2022, and revealed, among other things, galaxies existing just a billion years after the Big Bang. In May, 2023, it discovered a galaxy called JADES-GS-z14-0, which existed 300 million years after the Big Bang. Its light has been journeying for 13.5 billion years.
The next time you yearn to delve into the past, simply look up.
Wishing you clear skies and wide-open eyes.
- astronomers have used the Hubble Deep Field to observe about 100 tiny, red galaxies, some of the most distant known, which emerged only 800 million years after the Big Bang due to the cosmic expansion.
- The James Webb Space Telescope's capabilities allow it to scan infrared light, providing a glimpse into the past even further, with its deepest image titled 'Webb's First Deep Field' revealing galaxies existing just a billion years after the Big Bang in 2022.
- The Webb Space Telescope made another significant discovery in May 2023, spotting a galaxy called JADES-GS-z14-0, which existed 300 million years after the Big Bang, and its light has been traveling towards us for 13.5 billion years.
- The James Webb Space Telescope's discoveries, such as JADES-GS-z14-0, challenge the universe age paradox, proving that even the oldest galaxies can be observed, revealing a universe in a constant state of change and expansion.
- The Hubble Deep Field and the James Webb Space Telescope's discoveries of distant galaxies contribute to the intriguing concept that, by observing the redshift universe, we're essentially "seeing the past," making starlight travel time an essential factor in understanding our cosmic history.