# At the beginning of the universe

• lwymarie
In summary, the concept of a varying speed of light (VSL) and other varying dimensionful "constants" have been discussed in various threads and articles. However, physical measurements ultimately rely on dimensionless numbers and ratios, making it impossible to measure a change in a dimensionful quantity like the speed of light. Therefore, there is no way to determine if the speed of light was faster at the beginning of the universe compared to nowadays.
lwymarie
at the beginning of the universe, is light's speed faster than nowadays?

lwymarie said:
at the beginning of the universe, is light's speed faster than nowadays?

there are a few threads about the concpet of a varying speed of light (VSL), and to expand, the meaningfulness of any other varying dimensionful "constant".

http://arxiv.org/PS_cache/hep-th/pdf/0208/0208093.pdf

bottom line: every physical measurement we make is ultimately measuring a dimensionless number or numbers. if we measure a dimensionful quantity (say, length), we measure it against another like dimensioned quantity (say, a ruler) called a standard or a unit. we count tick marks. we mortals cannot measure a dimensionful quantity in and of itself and cannot measure a change in such a quantity in and of itself. we can only measure such a change against some other like dimensioned quantity, and the only salient measure is that ratio (of say, the speed of light against some other measure of speed), not either of the quantities being compared.

r b-j

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lwymarie said:
at the beginning of the universe, is light's speed faster than nowadays?

The middle length answer is another question - "how could you tell?"

## 1. What is the Big Bang Theory?

The Big Bang Theory is a scientific explanation for the origin and expansion of the universe. It proposes that about 13.8 billion years ago, all matter and energy in the universe was condensed into a single point, known as a singularity. This singularity then rapidly expanded, creating the universe as we know it.

## 2. How do we know the universe began with the Big Bang?

Scientists have gathered evidence from various fields such as physics, astronomy, and cosmology to support the Big Bang Theory. One key piece of evidence is the cosmic microwave background radiation, which is the remnant heat leftover from the explosion of the singularity. This radiation is found throughout the universe and is a strong indication that the universe began with the Big Bang.

## 3. What existed before the Big Bang?

The concept of "before" the Big Bang is difficult to understand because time and space as we know it did not exist before the universe began. Some theories suggest that the singularity may have been preceded by a previous universe or that the concept of time may not apply to the singularity.

## 4. How did the universe expand after the Big Bang?

The universe expanded and continues to expand due to a phenomenon called inflation. Inflation is a rapid expansion of the universe that occurred immediately after the Big Bang. It is thought to be driven by a repulsive force called dark energy, which is still not fully understood by scientists.

## 5. What will happen to the universe in the future?

Based on current scientific understanding, the universe will continue to expand forever. As it expands, galaxies will become further apart, and the universe will become colder and darker. Some theories suggest that eventually, the expansion may accelerate, leading to a "Big Rip" where the universe will tear apart completely.

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