Central Idea

• Researchers from India and the US have come up with a new way to answer a big question about the universe.
• This question is about how fast the universe is getting bigger.

Story of Our Universe

• The universe began around 13.8 billion years ago with a massive explosion called the Big Bang.
• As time passed, the universe kept getting bigger, with moments of speeding up and slowing down.
• Scientists want to understand this expansion to figure out what’s happening in the universe.

Hubble Constant: A Big Question

• The Hubble constant is a special number that tells us how quickly the universe is expanding.
• This number was first talked about by a scientist named Edwin Hubble in 1929.
• But scientists today are still not sure about its value.

Two Important Things to Measure

To know the Hubble constant, we need to measure two things carefully:

1. How far away things in space are from us.
2. How fast these things are moving away from us because of the universe’s expansion.

Old Ways vs. New Idea

Until now, scientists used a few methods to measure the Hubble constant:

• Looking at bright explosions in space called supernovae.
• Using special light from the early universe.
• Studying waves created by big crashes in space.

But now, a fresh idea has been propounded by Indian researchers:

• To measure using a thing called “gravitational lensing.”

Gravitational Lensing: A New Approach

• Gravitational lensing is like bending light using gravity. Imagine it like a magnifying glass in space.
• This idea came from a long time ago but got better recently.
• Scientists think they can use this lensing trick to measure the Hubble constant.
• They want to look at waves from space collisions that get bent by gravity.
• These bent waves could tell us about how fast the universe is expanding.

The Big Idea: A Bridge between Time

• This new idea is cool because it connects different times in the universe’s history.
• It could give us a good answer about the Hubble constant.

Challenges

• While this idea is exciting, there are some challenges to solve:

• 1. Making sure the signals are clear enough to measure.
  2. Using the new method to answer other questions too.
• If this new way works, it could help us learn about things like dark matter and other universe stuff.

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