97% of Galaxies Are Moving Faster Than Light, HOW IS THIS POSSIBLE?

Summary

This video explores the concept of the expanding universe, explaining how 97% of galaxies are moving away from us faster than the speed of light due to space expansion, not motion through space. Using analogies like ants on a balloon and bread dough, the video breaks down the complex physics behind cosmic expansion and redshift. It also touches on the idea of a 'sphere of inaccessibility,' showing how some galaxies will forever be out of reach, while others will eventually come into view. Despite increasing observable galaxies, the video concludes that we'll see more of the universe's past, but never its present state.

Takeaways

• 😀 97% of galaxies in the observable universe are moving away from us faster than the speed of light, due to the expansion of space.
• 😀 Einstein's theory of special relativity only applies to objects moving through space, not the space itself expanding.
• 😀 The expansion of space means galaxies are not physically moving through space faster than light, but the distance between us and them is increasing.
• 😀 The 'birthday party for anteaters' analogy illustrates how the expansion of space makes objects (galaxies) move further apart, even if they remain stationary.
• 😀 A more accurate analogy involves ants embedded in dough that expands, showing how galaxies are held together by gravity but still experience the effects of space expansion.
• 😀 Galaxies, stars, and planets remain the same size because their gravity counteracts the expansion of space around them.
• 😀 Space isn't expanding into anything else; it's the entire universe that's expanding, which is a crucial concept in understanding cosmic expansion.
• 😀 The further galaxies are from us, the faster they appear to be receding due to the expansion of space, reaching speeds beyond the speed of light in some cases.
• 😀 Redshift occurs as light from distant galaxies stretches due to space expansion, indicating their distance and speed, even though no object is traveling faster than light.
• 😀 The cosmic horizon is 45 billion light-years away, representing the furthest point we can observe due to the expanding universe.
• 😀 As the universe continues expanding, galaxies that are currently outside the observable universe will eventually become visible to us, but only as they were in the distant past.
• 😀 Due to the accelerating expansion of space, the sphere of inaccessibility (beyond which no signal can ever reach us) is shrinking over time.
• 😀 The observable universe is growing as more galaxies move into view, but we can only observe them as they were billions of years ago, not as they are today.
• 😀 The video ends with a challenge for viewers to calculate how many galaxies are receding faster than light, encouraging further engagement with the concepts discussed.

Q & A

What is the key reason that 97% of galaxies in the observable universe are moving away from us faster than the speed of light?

The key reason is that the space between us and these distant galaxies is expanding. According to Einstein's theory of special relativity, nothing can move faster than the speed of light through space, but this rule doesn't apply to the expansion of space itself.

How do the examples of the balloon and bread with ants illustrate the concept of space expansion?

The balloon analogy illustrates the expansion of space in two dimensions, where ants (representing galaxies) get farther apart as the balloon inflates. The bread analogy is a better fit for space because it represents expansion in three dimensions, where ants (galaxies) get further apart as the dough (space) expands.

Why do galaxies, solar systems, stars, and planets not increase in size despite the expanding space around them?

These objects do not increase in size because their gravity is much stronger than the force of space expansion. The expanding space affects the distances between objects on larger scales, but gravity keeps these objects from changing size.

What is the significance of redshift in the context of the universe's expansion?

Redshift occurs when light stretches as it travels through expanding space. The further a galaxy is, the greater the redshift of its light, which tells us that it is moving away faster. This stretching of light allows us to understand the rate at which galaxies are receding.

What is the 'sphere of inaccessibility' in the universe?

The sphere of inaccessibility refers to the region of space beyond which no signal or light we emit today will ever reach, due to the accelerating expansion of space. Galaxies within this sphere are moving away faster than the speed of light.

How does the observable universe differ from the cosmic horizon?

The observable universe is the region of space from which light has had time to reach us, while the cosmic horizon represents the maximum distance from which light can travel, taking into account the expansion of the universe. The cosmic horizon is much further away than the observable universe.

Why do we see distant galaxies as they were in the past, rather than how they are today?

We see distant galaxies as they were in the past because the light from these galaxies has been traveling toward us for millions or billions of years. The light we observe today was emitted a long time ago, and the expansion of space affects how we see them.

What is the current distance of GN-z11, and how does it relate to its past light emission?

GN-z11 is currently 32 billion light-years away, but we observe it as it was 400 million years after the Big Bang. The light from GN-z11 has been traveling towards us for over 13.5 billion years, and as space expanded, its wavelength was stretched, resulting in a redshift.

What does the accelerating expansion of space mean for the future of the observable universe?

As the space between galaxies continues to expand at an accelerating rate, more and more galaxies will move beyond the observable universe. However, we will also be able to see more galaxies in the future because the light from galaxies currently beyond our reach will eventually reach us.

What happens to the 'sphere of inaccessibility' and the edge of the observable universe over time?

The sphere of inaccessibility is shrinking, meaning fewer galaxies will ever be accessible to us. In contrast, the edge of the observable universe is growing larger as light from distant galaxies continues to reach us over time, expanding the universe we can observe.