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Cosmic Times

Let’s Explore Cosmic Times Through Webb’s Lens!

The James Webb Space Telescope (JWST) has brought us an exciting week with its release of stunning photos of our Universe that reflects the old cosmic times.

One of the images allows us to glimpse faint distant galaxies as they appeared over 13 billion years ago.

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The SMACS 0723 deep field image was taken with only a 12.5-hour exposure. Faint galaxies in this image emitted this light more than 13 billion years ago. Credits: NASA, ESA, CSA, and STScI

How Old is Our Planet Earth?

Today, cosmologists have successfully measured the age of the universe in various ways, and all these measurements agree. The age, approximately 13.7 billion years, is now a well-established fact and won’t undergo significant changes. Just like knowing the age of the earth, we also understand the age of the universe. That helps us comprehend the immense expanse of time since its inception and our place within it.

How Does the Speed of Light Shape Our View of the Cosmic Times?

Now is the perfect moment to pause and marvel at our exceptional access to the mysteries of the Universe. Thanks to our first-class ticket that allows us to explore its depths and witness the past through these extraordinary images.

These images also bring up intriguing considerations regarding how the Universe’s expansion impacts our calculations of distances on a cosmological scale.

Looking back in time may sound peculiar, but it’s a daily practice for space researchers.

Our Universe adheres to the laws of physics, with one well-known rule being the incredible speed of light. When we refer to “light,” we’re actually talking about all the wavelengths across the electromagnetic spectrum, zipping through space at a mind-boggling 300,000 kilometers per second.

Although light appears direct in our everyday experiences, it still takes time to make one’s way cross over the cosmic times.

For instance, when we gaze at the Moon, we’re seeing it as it appeared 1.3 seconds ago—just a tiny glimpse into the past. The same applies to sunlight, but in this case, the photons (light particles) emitted from the Sun’s surface take a little over eight minutes to reach Earth.

One paleontologist told The New York Times:

“It’s only by doing that that we’re able to reconstruct ancient ecosystems.”

How We Are Seeing a Nebula Image That is 2,000 Years Ago?

Our galaxy, the Milky Way, stretches over 100,000 light-years. While the beautiful newborn stars captured in the JWST’s Carina Nebula image lie 7,500 light-years away. In simpler terms, the image we see of this nebula comes from a time approximately 2,000 years in cosmic times before the invention of writing in ancient Mesopotamia.

Carina Nebula
The Carina Nebula is a birthplace for stars. Credits: NASA, ESA, CSA, and STScI

Whenever we direct our gaze beyond Earth, we’re essentially peering into the past, witnessing how things used to be. For astronomers, this ability to observe light from various points in time is like having a superpower, enabling us to piece together the enigmatic story of our universe.

What sets JWST apart and makes it truly spectacular is its capability to observe a wide range of infrared light. Unlike Earth-based telescopes, space-based telescopes like Hubble can access specific light ranges that Earth’s dense atmosphere blocks. Hubble, designed for ultraviolet (UV) and visible parts of the electromagnetic spectrum, excels in those areas. On the other hand, JWST’s specialization in infrared light allows it to peer further back in time compared to Hubble.

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The electromagnetic spectrum with Hubble and JWST’s ranges. Hubble is optimised to see shorter wavelengths. These two telescopes complement each other, giving us a fuller picture of the universe. Credits: NASA, J. Olmsted (STScI)

What are the Longer & Shorter Wavelengths of Galaxies in Cosmic Times?

Galaxies emit various wavelengths across the electromagnetic spectrum. That ranges from gamma rays to radio waves and everything in between. Each of these wavelengths provides crucial insights into the distinct physics occurring within a galaxy.

When galaxies are relatively close to us, their emitted light hasn’t undergone significant changes, allowing us to examine a wide range of wavelengths and gain a comprehensive understanding of their internal processes.

However, when galaxies are extremely distant, we face a different situation. The light from these faraway galaxies, as observed now, has been stretched due to the expansion of the universe. Which results in longer and shorter wavelengths.

The Concept of “Cosmological Redshift”:

Consequently, some of the light that was originally visible to our eyes when it was emitted has lost energy over time due to the universe’s expansion. As a result, it now resides in an entirely different segment of the electromagnetic spectrum. This fascinating phenomenon is known as “cosmological redshift.”

Why are Time Dilation and Relativity Essential for the Accuracy of GPS?

When people or objects move at speeds close to that of light, strange effects predicted by Einstein’s theory of relativity start to influence time. One of these effects is that each observer perceives the other’s clock as running slower. This doesn’t mean there’s anything wrong with the clocks themselves. Rather, time itself appears to slow down for the fast traveler compared to those who remain at rest.

This time dilation phenomenon is real and has practical implications. For instance, if one twin were to travel at a speed approaching that of light and then return to Earth, she would be younger than her twin sister who stayed behind. The same effect occurs when gravity is strong, causing clocks to run slower. And it is one of the mesmerizing fact of cosmic time, and time travelling.

In particle accelerator laboratories, scientists routinely demonstrate the slowing down of clocks due to motion, significantly lengthening the lifetimes of unstable elementary particles when they move at speeds close to that of light.

Both the time dilation effect and the impact of gravity on clock speed, as described by Einstein’s general theory of relativity. And they are crucial factors considered in the operation of the Global Positioning System (GPS). Neglecting these effects would result in GPS errors, with inaccuracies amounting to several kilometers per day!

What Correlated Pairs of Objects Across the Universe Reveal About the Cosmic Times?

Cosmologists have long observed an intriguing pattern in space, discovering correlated pairs of objects distributed throughout the universe. These pairs are noticeable in various forms, such as hot spots seen in early universe maps from telescopes, pairs of galaxies, galaxy clusters, or superclusters in the present-day universe, and pairs found at all distances apart. By moving a ruler across a map of the sky, these “two-point correlations” become evident. With the presence of an object at one end increasing the likelihood of another object.

The most straightforward explanation for these correlations traces back to the early moments of the Big Bang. This is one of the impressive, and most awe-inspiring event in cosmic times. During this cosmic event, pairs of quantum particles spontaneously came into existence as space expanded exponentially. The particle pairs that emerge earlier in this process moved the farthest apart over time, leading to the formation of objects that are now distantly separated in the sky. On the other hand, particle pairs that emerged later remained closer together, forming pairs of objects that are more closely located to each other. Much like fossils that preserve ancient history, these pairwise correlations observed across the sky encode the passage of time. Which specifically representing the very beginning of time.

The Correlation Fact is Phenomenal! Let’s Agree to a Point:

For the universe as a whole, in which everything is moving with respect to everything else and some of the light that we see comes from near black holes where the gravity is very strong indeed, what clock can we possibly use to describe a meaningful age? What all cosmologists do is to imagine that there are clocks everywhere that started running at the Big Bang. And how that move with the expansion of the universe along with the nearby galaxies?

This gives a definite cosmic times that all observers can agree on.

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