⭕ What is the Cosmic Speed Limit (the speed limit in the universe)❓
🟢 Cosmic Speed Limit
It is the highest speed at which an object or energy can travel through a vacuum. Light travels at that high speed. It is about 3 lakh kilometers per second. In addition to light, other electromagnetic waves such as radio waves, X-rays, and gamma-rays also travel at the same speed.The journey of light is like a car traveling on a road. There is a limit to how fast a car can travel on a road.
⭕ What is the expansion of the universe❓
🟢 Expansion of the universe is the expansion of space itself in all directions. It does not start from one point and expand in all directions, but is a phenomenon that occurs everywhere the same way.
At a distance of one megaparsec (Mpc), space is expanding at a rate of about 70 kilometers per second. One megaparsec is about 3.26 million light years.
🔹 At a distance of one megaparsec: 70 km/s
🔹 At a distance of two megaparsecs: 140 km/s
🔹 At a distance of one hundred megaparsecs: 7000 km/s
🔹 These figures show that the distance between galaxies and us increases at an increasing rate.
At a distance of about 4,200 megaparsecs (4.2 Gpc), the rate of expansion of the universe exceeds the speed of light, which is 300,000 kilometers per second. That is, the space between us, even for galaxies that are about 14.4 billion light years away, is expanding at a rate that exceeds the speed of light.
As the space between galaxies expands, the distance between them increases.
⭕ Why is it wrong to mix these two up?
🟢 The important difference is this:
🔹 The speed of light refers to the motion of an object (travel through space).
🔹 The expansion of the universe is the expansion of space itself (the size of space increases).
🔹 Light travels like a car driving down a road. However, the expansion of the universe is like the road itself lengthening. If a road is suddenly lengthened, doesn't the distance between two cars on it increase? That's how the universe expands.
That's why very distant galaxies appear to be moving away from us faster than the speed of light. It's not that galaxies are traveling faster than the speed of light, but rather that the space between us and them is expanding rapidly.
⭕ So why do people compare these?
🟢 People often use velocity calculations to help them understand how fast the universe is expanding. This is because they can easily explain how fast the distance between galaxies at a given distance and us is increasing. This simplification is only for understanding the large scale of the universe's expansion.
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