Discover The Heavens

You might've heard time and time again that our universe has been expanding ever since its beginning. This is being widely accepted nowadays, but this wasn't the case a few decades back. The universe was thought to be static, eternal, and hence thought to have no beginning. What did we discover that caused this dramatic change of views? What implications did it have on our understanding of the universe? Why is it still being actively researched? In previous posts, we have been taking the fact that the universe is expanding for what it is. But the answers to these questions lie behind the science of the universe's expansion. Let's delve deeper! (Left - Vesto Slipher, Center - Henrietta Leavitt, Right - Edwin Hubble) In 1912, astronomer Vesto Slipher studied the spectrum of various galaxies. He found that, for most of the galaxies in our universe, the absorption lines were shifted to the red end of the spectrum / redshifted. He concluded that this redshift was due to the ...

Image Credit: NASA's Goddard Space Flight Center "Sound! In space!? Isn't sound a mechanical wave, doesn't it need a medium to propagate through? But space is a vacuum, and "In space, no one can hear you scream" is a well-known fact," you might be thinking. Well, you are right. Indeed, sound does not travel in space now, but it did in its very early years, billions of years back. You might've read in previous posts that we cannot see anything beyond the Cosmic Microwave Background (CMB), the earliest light in the universe. While it is true that we can't see any light beyond the time when CMB was released during the epoch of recombination, we can see sound waves from the time before recombination, embedded in our universe. How did these sound waves come to be and how exactly can we see them even now? And what do they tell us about our universe? Let's find out! Before the epoch of recombination, the universe was too hot for atoms to form and el...

Our universe is majestic, marvelous, and fascinating everywhere we look. From black holes to galaxies to planets and stars, nothing fails to captivate our curious selves. But what do you think the universe— the space itself that contains everything—looks like? What does the universe as a whole look like, and what shape does it have? Think with me for a moment here. Firstly, how do we tell the shape of something? How do we tell if something is shaped like a square, a circle, or if something is flat or curved? Well, by looking at it from the "outside".  Now, let's say we have two 2-dimensional friends, Cici and Fifi. Cici lives in her universe that is curved, like the surface of a sphere. And Fifi lives in her universe, which is flat, like a sheet of paper. If they wanted to find out the shape or curvature of their universe, how would they figure it out?  Since both Cici and Fifi are 2D beings, they cannot look at their universe from the "outside". Their range of ...

Imagine that one day the world we live in suddenly goes completely dark with no light around us. Many of us would've pictured an apocalyptic day where the sun, moon and the other stars would've vanished. In our minds, we always tend to associate natural light with stars. Without stars, we feel, there would be no light. But, would you believe me if I told you that light as we see it was present in our universe even before stars were formed? Elementary and composite particles (Epoch is a moment in time which marks the beginning of a new era due to drastic changes in the formation of our universe)  Quark epoch: Around  10 −12  seconds after the big bang, the universe was filled with a dense, hot ionized plasma containing elementary particles called quarks, leptons and their antiparticles. The collisions between these particles were too energetic, and the universe was too hot for other composite particles to form.  Hadron epoch: As time ticked by, the universe expanded...

Humanity’s historical events are alive in our everyday lives as cultures and traditions. The past events that define us are described in books, scripts, and artefacts. But what about the past of The Cosmos that defines us? We just have to look up and gaze into the past that is alive in the present. Let me show you how. Light travels at a speed of 299,792,458 m/s in vacuum, which means light travels a distance of 299,792,482 meters in one second. So when we see a flash of lightning three kilometres away, we are seeing something that happened a hundredth of a millisecond ago. This is not the distant past, but as the distance that light travels increases, the time it takes to reach us also increases. Let us consider The Moon, that is about 380,000 km away from The Earth. It takes 1.3 seconds for light to travel from The Moon to us. Thus we see The Moon as it was 1.3 seconds ago. The Sun is about 150 million kms away from The Earth, so we see The Sun as it was 8 minutes ago. From here thin...