Planck length and space expansion/contraction

In summary, as cosmological time progresses, the edges of a cubic volume of space expand with the scale factor. However, due to the time-reversible nature of physics, it is also possible to imagine time going backwards and the edges contracting with the scale factor. This raises the question of whether this would result in the edges being smaller than the smallest length scale, the Planck length. However, according to current understanding, there is no contradiction here.
  • #1
jcap
170
12
Imagine a cubic volume of space, defined today, with edges of the order of the Planck length.

As cosmological time goes forward this volume expands so that the edges of the cube expand with the scale factor. This seems ok.

However, as physics is time-reversible, it should be valid to imagine time going backwards so that the edges contract with the scale factor.

But then they would be smaller than the Planck length. If the Planck length is the smallest length scale then is there a contradiction here?
 
Space news on Phys.org

Related to Planck length and space expansion/contraction

1. What is the Planck length?

The Planck length is the smallest possible unit of length in the universe, measuring at approximately 1.6 x 10^-35 meters. It is named after physicist Max Planck and is derived from fundamental physical constants such as the speed of light, gravitational constant, and Planck's constant.

2. How is the Planck length related to space expansion and contraction?

The Planck length is not directly related to space expansion or contraction. It is a fundamental constant that represents the scale at which quantum effects become significant. However, theories such as quantum gravity and string theory suggest that the Planck length may play a role in understanding the nature of space and time.

3. Can the Planck length change over time?

According to current theories, the Planck length is a constant and does not change over time. However, some theories propose that the Planck length may vary in different regions of the universe or under extreme conditions such as near a black hole.

4. Is the Planck length the smallest possible unit of length?

The Planck length is currently believed to be the smallest possible unit of length. However, this is based on our current understanding of physics and could change in the future as new theories and discoveries emerge.

5. How does the concept of space expansion relate to the expanding universe theory?

The expanding universe theory states that the universe is continuously expanding, with galaxies and other objects moving away from each other. This expansion does not occur at a constant rate and can vary over time. The idea of space expansion is one possible explanation for this phenomenon, where space itself is expanding and causing the apparent movement of galaxies.

Similar threads

I Is the Planck length a proper length?
    • Cosmology
Replies
6
Views
2K
I Does the Planck length expand in a FRW universe?
    • Cosmology
Replies
1
Views
1K
I Does the Friedmann vacuum equation have a linear solution?
    • Cosmology
Replies
1
Views
1K
Gravitational waves, distance and space-time
    • Cosmology
Replies
11
Views
2K
What happens when matter pops into and out of existence at Planck length scales?
    • Cosmology
Replies
9
Views
2K
A The scale of an extra dimension
    • Beyond the Standard Models
Replies
1
Views
2K
I Some questions about Cosmic Inflation
    • Cosmology
Replies
4
Views
2K
Questions Concerning The Planck Epoch
    • Cosmology
Replies
15
Views
4K
A Experimental test of shrinking matter theory?
    • Cosmology
2
Replies
42
Views
3K
I Length Contraction & Time Dilation Beyond Planck Scale: Correct?
    • Special and General Relativity
Replies
4
Views
1K

Hot Threads

Recent Insights

Back
Top