- #1
Ranku
- 410
- 18
What was the size of the 'radius' of the universe when it started to expand acceleratingly about 6 Gyrs ago?
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In summary, the conversation discusses the measurement of the 'radius' of the universe when it started to expand acceleratingly about 6 Gyrs ago. The clarification of the term 'radius of the universe' is needed, as it could refer to the scale factor, the radius of the observable universe at the time, or the distance to the cosmological event horizon. The speaker also notes that the cosmic scale factor, a(t), is dimensionless and currently measures at approximately 10^29 cm. The question remains as to the specific measurement of a when the universe began to accelerate.
- #2
Calimero
- 258
- 0
Not quite sure what are you asking. You probably asking either about scale factor (a), or about radius of observable universe at the time. Or maybe about distance to the cosmological event horizon ?
Can you be more specific about what you mean with 'radius of the universe' ?
Can you be more specific about what you mean with 'radius of the universe' ?
- #3
Ranku
- 410
- 18
Calimero said:
Thank you for clarifying the question before answering it
If 'radius' of the universe is a, then cosmic scale factor is a(t), which is dimensionless. a has units of distance, which is presently ~10^29 cm. So I need to know how large was a when the universe started to accelerate ~6 Gyrs ago?
1. What is the radius of the universe 6 billion years ago?
The radius of the universe 6 billion years ago, also known as the cosmic horizon, is estimated to be around 46.6 billion light years.
2. How is the radius of the universe 6 billion years ago determined?
The radius of the universe 6 billion years ago is determined by measuring the distance of the farthest observable objects in the universe and using the expansion rate of the universe to calculate the size of the observable universe at that time.
3. Has the radius of the universe 6 billion years ago changed over time?
Yes, the radius of the universe 6 billion years ago has changed over time due to the expansion of the universe. As the universe expands, the distance between objects increases and the cosmic horizon expands along with it.
4. How does the radius of the universe 6 billion years ago compare to the current radius?
The current radius of the observable universe is estimated to be around 93 billion light years, which is almost twice the radius 6 billion years ago. This is due to the ongoing expansion of the universe.
5. Why is knowing the radius of the universe 6 billion years ago important?
Knowing the radius of the universe 6 billion years ago is important for understanding the evolution of the universe. It provides insight into the expansion rate of the universe and the age of the universe. It also helps us better understand the early stages of the universe and how it has changed over time.
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